JPS6240630A - Optical pickup - Google Patents

Abstract

PURPOSE:To correct properly the displacement of an objective lens due to the undesired vibration at high speed access by providing a reflecting face to the side face of a support member of the objective lens and providing oppositely a light source nd photodetecting element to the inner face of a support cylinder opposite thereto. CONSTITUTION:A reflecting face 44 is provided to the side face of the support member 37 of the objective lens 34 and the light source 41 for position detection and photodetecting members 39a, 39b are provided oppositely to an inner peripheral face 25c of the support cylinder 25 opposed to the face. When the objective lens 34 is displaced by an undersired vibration at high speed access, a deflection is caused to the support member 37. The deflection is detected by the distribution of luminous quantity of the photodetecting members 39a, 39b through the change in a reflecting angle of luminous flux irradiated to the reflecting face 44 form the light source 41. The position of the objective lens 34 is corrected properly with high accuracy by the output voltage difference in this case.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical pickup that reads information recorded on a recording surface of a recording medium such as a compact disc or writes information on this recording surface.

[Prior Art and Problems to be Solved by the Invention] Conventionally, information recorded on a recording medium such as a compact disc, a video disc, or an optical disc such as a data disc is read or information is written to this recording medium. Various writing optical pickups have been proposed.

FIG. 8 is a schematic diagram showing the operating principle of this type of optical pickup.

Scattered light emitted from a light source 1 such as a light emitting diode is collimated into a parallel light beam by a collimator lens 2, passes through a diffraction grating 3, is divided into three parts, passes through a beam splitter 4, and reaches a reflecting prism 5. The parallel light beam reflected in the 90° direction by the reflecting prism 5 passes through the 174-wave plate 6, passes through the objective lens 7, and reaches the bit P formed on the recording surface 8a of the recording medium 8 such as a compact disc. A light spot with a diameter of approximately 1 μm is imaged.

The light beam reflected from the recording surface 8a reaches the beam splitter 4 via the opposite optical path.

At this time, this reflected light passes through the 174 wavelength plate 6 twice in a round trip, so its polarization direction is perpendicular to the polarization direction of the outgoing path, and it is totally reflected in the 90'' direction by the polarized light 1jJ4a. The return light from the recording surface 8a passes through a cylindrical lens 9 and enters a photodetector 10.

This photodetector 10 has a light-receiving area divided into two in the radial direction and the tangential direction of the recording surface 8a of the recording medium 8, and detects data signals and A focus error signal and a tracking error signal are detected.

Then, the focus servo mechanism and the tracking servo mechanism of the actuator 11 provided in the objective lens 7 are driven in accordance with the focus error signal and the tracking error signal, and the objective lens 7 is moved slightly, and the focus is set on the recording medium 8. A correction V' is made to match the recording surface 8a and so that the light spot accurately follows the bit P provided on the track.

By the way, as shown in FIG. 9 (a cross-sectional side view of the main part), the lower end of the lens frame 12 that holds the objective lens 7 is connected to the holding tube 1.
A pair of parallel tracking leaf springs 14 erected at 3
The upper and lower surfaces of the holding cylinder 13 are further supported by a pair of parallel focusing leaf springs 15 disposed in the horizontal direction, and these parallel leaf springs 14 and 15 support the objective during the correction operation. Slight movement of the lens 7 in two-dimensional directions is allowed.

Further, the focus servo mechanism or the dragging servo mechanism of the actuator 11 is configured such that a focus error signal or a tracking error signal is fed back only during normal recording and reproducing operations. Therefore, for example, the circuit of the focus servo mechanism or tracking servo mechanism during high-speed access is in an OFF state.

Therefore, the parallel leaf springs 14, 15 and the like vibrate due to rapid acceleration and deceleration of the carriage during high-speed access, causing unnecessary vibrations in the objective lens 7.

As a result, problems arise such as the positioning accuracy of the pickup being reduced or the control of each navigation mechanism becoming impossible, resulting in a delay in access time.

To deal with this, for example, Japanese Patent Laid-Open No. 58-26331 discloses that the position of the objective lens is detected using an electrostatic capacitive arsenic type non-contact minute displacement detection probe, so that tracking control can always be performed in a closed loop. A conventional technique related to an optical head configured as described above is disclosed.

However, since this conventional technology uses a capacitive detection sensor, a linear analyzer is required to make the output (ffi) linear, and the sensor diameter is large, making the optical pickup smaller and lighter. Not suitable for
There is also a risk of being affected by electromagnetic noise from the outside.

Furthermore, there is also a type of optical system that performs tracking control by rotating a mirror by a predetermined angle using an actuator, as disclosed in Japanese Patent Application Laid-Open No. 57-94942, which reflects a light beam from a light source toward an objective lens. In order to eliminate unnecessary vibrations that occur in the mirror during high-speed access, the type pickup uses an angular position detection device to correct the tilt angle of the mirror during access.

However, it is necessary to leave a certain distance between the position detection light source provided in this prior art position detection device and the mirror. Furthermore, in order to detect the inclination angle of the mirror using the light flux from this light source, it is necessary to irradiate this mirror with a relatively large light spot, and when this light spot becomes large, the light receiving element that receives the reflected light has to receive the reflected light. The area will also have to be enlarged. As a result, the overall size of the device becomes larger and its structure becomes more complex.

Please note that the applicant has filed an earlier application (patent application filed in 1986) by the same applicant.
- As shown in FIG.
In addition, the light source 17 and the light receiving member 18 divided into two parts are disposed opposite to each other with the n detection unit 16 in between, and the output voltage difference from the light receiving surface of the light receiving member 18 divided into two parts is determined. By detecting this, feedback control during access is enabled, and even if the objective lens 7 receives unnecessary vibration during high-speed access, a correction operation is immediately performed.

However, since the lens frame 12 is provided with the position detection unit 16, etc., the ff1Nl of the entire lens frame 12 increases, and as a result, it becomes difficult to perform correction operations in the tracking direction and focusing direction during reading or overlapping. It is necessary to supply a large amount of control current, which increases power consumption.

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is possible to achieve high-speed access with a simple structure that is not affected by external electromagnetic noise, and is not affected by external electromagnetic noise. It is an object of the present invention to provide an optical pickup that can detect the displacement of an objective lens that occurs at certain times, avoid appropriate correction operations, and further reduce the amount of control current consumed.

[Means for Solving the Problems] The optical pickup according to the present invention includes an objective lens provided on the recording surface of a recording medium to converge a light beam from a light source onto the recording surface, and this objective lens 7. In a device that is connected to the cut unit and performs a correction operation on the recording surface in at least two dimensions, a supporting member that supports the objective lens so as to be movable in at least two dimensions is provided with a reflective surface, and the reflective surface A light source for position detection and a light receiving member that receives the light beam from the light source for position detection reflected by the reflective surface are installed opposite each other, and the support member is deflected during high-speed access. The light receiving element distribution, which changes depending on the reflection angle of the light beam from the position detection light source irradiated onto the reflective surface provided on the support member, is detected, and the objective lens is corrected to the appropriate position. This is what I did.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

1 to 5 relate to the first embodiment of the present invention, FIG. 1 is a schematic sectional view of the main part of an objective lens actuator of an optical pickup, and FIGS. 2 and 3 show the state of displacement of the objective lens. FIG. 4 is a cross-sectional side view of the objective lens actuator of the optical pickup, and FIG. 5 is a plan view of the objective lens actuator with the yoke holding frame removed.

In these figures, reference numeral 21 is an objective lens actuator 21 of an optical pickup. The outer frame 22 of this actuator 21 is formed into a cylindrical shape with both ends open, and a permanent magnet 23 having a rectangular cross-sectional shape and an annular shape as a whole is fixed at approximately the center inside the outer frame 22. ing.

Further, on both pole sides of the permanent magnet 23, a yoke 24a having a rectangular and linear cross-sectional shape and an annular rest,
A magnetic circuit is formed by the yokes 24a, 24b and the permanent magnet 23. Furthermore, a gap is formed between the yokes 24a and 24b.

Furthermore, a holding cylinder 25 is disposed within the outer frame 22. This holding cylinder 25 includes a substantially cylindrical middle cylinder part 25a with openings at both ends, and a coil holding cylinder part 25b which is integrally formed in a concentric cylinder shape on the outside of this middle cylinder 1g25a and has one end (upper end side) open. It is formed from. This coil holding cylinder part 25
A focusing voice coil 26 is wound around the outer periphery of b. This focusing voice coil 26
The coil holding cylinder part 25b around which the voice coil 2 is wound
6 at one end (upper side) facing the permanent magnet 23.
The frontage side is fitted into the gap formed by the yokes 24a and 24b so as to be freely removable.

Further, the holding cylinder 25 has a spacer 27 disposed above the yoke 24a at the upper end of the middle cylinder part 25a.
It is attached to the outer frame 22 by a focusing spiral spring 28a made of an elastic material whose periphery is held at the outer frame 22. Furthermore, this holding cylinder 25 has a focusing spiral spring 2 similar to the above-mentioned one whose periphery is held by a spacer 29 disposed at the lower end side of the outer frame 22 at the lower end side of the middle cylinder part 25a.
8a is attached to the outer frame 22. 1, that is,
The holding n25 is a focusing spiral spring 28a, 28b.
The outer frame 22 can be moved freely in its axial direction (optical axis direction F) by
is supported by

A yoke holding frame 30 is attached to the inside of the outer frame 22 above the focusing spiral spring 28a. a pair of first and second
The fixed yokes 31a and 31b, the first J3 and the second
Fixed yoke 31a.

A pair of first and second permanent magnets 32a and 32b connected to both ends of 31b are provided.

Tracking coils 33a, 33b are wound approximately at the center of the first and second fixed yokes 31a, 31b. An objective lens 34 is disposed between the first and second fixed yokes 31a, 31b around which the tracking coils 33a, 33b are wound. The objective lens 34 is attached to a lens frame 35 with its optical axis directed toward the central axis of the outer frame 22. A magnetic member 36 formed to face the tracking coils 33a and 33b is fitted onto the outside of the lens frame 35. Further, a gap is formed between the lens frame 35 and the magnetic member 36, and an elastic member is formed in this gap to allow movement of the objective lens 34 in the tracking direction T) in a direction perpendicular to the optical axis. A pair of parallel leaf springs 37 for tracking
．． One end of 37 is inserted and fixed. Roughly, this one
- The other end side of the racking plate spring 37.37 is the holding cylinder 2
5 and is fixed inside the lower end of this holding cylinder 25.

On the other hand, a light emitting element 41, which is an example of a light source for position detection, is fixedly installed on the inner circumferential surface 25c of the middle cylinder part 25, which is numbered in the holding n25, and faces parallel to the tracking parallel plate spring 37. Furthermore, light receiving elements 39a and 39b, which are examples of a light receiving section H, are fixed at equal intervals in the vertical direction sandwiching the light emitting cord 41. Further, the light emitting element 41 is disposed so as to be oriented substantially toward the center of the parallel leaf spring 37 in the longitudinal direction, and a reflective surface 44 is formed in the portion of the parallel leaf spring 37 that the light emitting element 41 is directed to. has been done.

This reflective surface 44 can be formed by plating the parallel plate spring 37, pasting a 7S film on the side surface of the parallel plate spring 37, or finishing the side surface of the parallel plate spring 37 itself into a mirror finish. It was formed.

Further, although not shown, an amplifier is connected to each of the light receiving elements 398 and 39b, and a differential amplifier is connected to this double-width amplifier, and tracking is performed in proportion to the output voltage difference of the received light ω detected by the differential amplifier. A laminar flow is applied to the tracking coils 33a, 33b.

Note that, as shown in FIG. 1, when the parallel plate spring 37 is not deformed, the light beam emitted from the light emitting element 41 is reflected vertically by the reflecting surface 44 in a uniform manner. ing.

Next, the operation of the optical pickup with the above configuration will be explained.

As shown in FIG. 1, the dragging parallel springs 37, 37 that support the objective lens 34 when it is stationary are perpendicular to the holding tube 25. The inner circumferential surface 25c of the middle cylinder part 25a facing the side surface is parallel to each other. In this state, the light beam emitted from the light emitting element 41 is transmitted to the parallel plate spring 3.
It is formed on the side surface of the IC anti-sword surface 44 and is reflected in the vertical direction at an equal angle. Therefore, the same amount of light is incident on the light receiving elements 39a and 39b arranged at equal intervals above and below the light emitting element 41, and the difference in output power detected by both the light receiving elements 39a and 39b is O.

On the other hand, when the objective lens 34 moves in the tracking direction T due to high-speed access operation, etc., the parallel leaf spring 37
is elastically deformed, the reflecting surface 44 formed on the side surface of the parallel plate spring 37 is inclined, and the distribution of the amount of light received by each light receiving element 39a, 39b changes.

For example, as shown in FIG.
When the parallel leaf spring 37 is displaced in a direction approaching 1, the middle of the parallel plate spring 37 tilts counterclockwise. As a result, the light emitting element 41
The amount of upward reflection of the luminous flux emitted from the reflective surface 44 decreases, and therefore the amount of light detected by the light receiving element 39b becomes greater than the detection value of the light receiving element 39a.

On the other hand, as shown in FIG.
1, the parallel plate spring 37
The middle part of the road slopes counterclockwise.

As a result, the amount of downward reflection of the light beam reflected by the reflecting surface 44 decreases, and the amount of light detected by the light receiving element 39a becomes greater than the detection value of the light receiving element 39b.

In this case, when the objective lens 34 is displaced in the tracking direction T, the angle of repulsion of the light beam at the reflecting surface 44 changes, and the output voltage difference between the light receiving elements 39a and 39b changes depending on the displacement of the position of the objective lens 34. Proportional.

A current proportional to this output voltage difference is fed back to flow through the tracking coils 33a and 33b to form a Ribo system closed loop, and the displacement of the objective lens 34 in the tracking direction is controlled to be maintained at a zero position. Therefore, even if the objective lens is affected by unnecessary vibrations during high-speed access, a correction operation is immediately performed and reading or writing can be started quickly.

Note that during normal recording and reproduction, when a focus error signal current is passed through the voice coil 26, a force acts on the holding tube 25, causing the focusing spiral spring 28a.

Due to the deflection deformation of 28b, the objective lens 34 is displaced in the l-racking direction F. Further, the tracking error signal current is sent to the tracking coil 33a.

When flowing to 33b, the parallel leaf spring for 1:3 is 37°3.
7, the objective lens 34 is displaced in the tracking direction T.

Further, FIG. 6 (plan view) shows a second embodiment of the present invention.

A bracket 53 is erected on the base 52 of the objective lens actuator 51 in this embodiment, and one end of a pair of tracking leaf springs 54 is fixed to the bracket 53. In addition, a relay member 5 is attached to the other end of the tracking plate spring 54 that protrudes laterally in a converged state.
5 is fixed. Further, one end of a pair of focusing leaf springs 56 facing in the vertical direction and parallel to each other is fixed to this relay member 55.
A support member 57 that holds the objective lens 34 is fixed to the other end of the lens 6 . This objective lens 34 is connected to the plate spring 54.
．． 56 allows movement in the tracking direction °F and in the focusing direction F (see FIG. 7).

Note that 58 is a focusing coil, 59 is a tracking coil, and 60 is a permanent magnet.

In addition, a reflective surface 44 is formed approximately at the center of the side surface of each of the racking leaf springs 1 to 54 by the same means as in the first embodiment. Furthermore, a light receiving element 41 facing this reflective surface 44, and light receiving elements 3 arranged at equal intervals in the direction in which the focusing plate spring 54 is disposed with the light receiving element 41 in between.
9a and 39b are fixed parts 4A that are erected on the base 52.
61 is fixedly installed.

When the objective lens 34 moves to 1 in the ranking direction T during a high-speed access operation, the tracking plate spring 54 that supports this λ/1 object lens 34 deforms, and the tracking plate spring 54 formed on the side surface of this tracking plate spring 54 deforms. The reflection angle of the light beam from the light emitting element 41 that is irradiated onto the reflective surface 44 changes.

Therefore, the amount of light incident on the light receiving elements 39a and 39b changes, causing a difference in the output/J voltage. Then, a current corresponding to this output voltage difference is applied to the five tracking coils, and a control operation is performed so that the amount of displacement of the objective lens 34 becomes O.

Moreover, FIG. 7 (side view) shows a third actual flow example of the present invention.

The objective lens actuator 51 in this embodiment detects the amount of displacement of the objective lens 34 in the focusing direction F and performs a correction operation.

That is, a reflective surface 44 is formed at the center of the side surface of the focusing leaf spring 56 facing the base 52, and the light emitting element 41 and the longitudinal side of the focusing leaf spring 56 are formed on this reflective surface 44 with the light emitting element 41 in between. Light receiving elements 39a and 39b arranged at equal intervals in the direction face each other,
The light emitting element 41 and the light receiving elements 39a and 39b are fixedly mounted on a fixing member 61 that is erected on the base 52.

When the objective lens 34 moves in the focusing direction F during high-speed access operation, the focusing leaf spring 56 that supports the objective lens deforms, and the leaf spring 56
The light emitting element 4 is irradiated onto a reflective surface 44 formed on the side surface of the light emitting element 4.
The angle of reflection of the light beam from 1 changes. Therefore, the amount of light incident on the light receiving elements 39a and 39b changes, causing a difference in output voltage.As a result, a current corresponding to this output voltage difference is applied to the focusing coil 58, and the amount of displacement of the objective lens 34 is changed to O. The correction will be made so that

Note that the present invention is not limited to the above embodiments; for example, in the first embodiment, the focusing plate spring 28a
Alternatively, a reflective surface may be formed on 28b, and the light emitting element and the light receiving element may be opposed to this reflective surface to control the displacement in the focus direction. In each embodiment shown in the figure, two light-receiving elements are provided, but the amount of displacement in the tracking direction or focusing direction can be detected based on the magnitude of the absolute value of the output of the light-receiving element. If this is done, it is possible to reduce the number of light receiving elements to one.

[Effects of the Invention] As explained above, according to the present invention, an objective lens that converges a light beam from a light source onto the recording surface of the recording medium is disposed opposite to the recording surface of the recording medium, and this objective lens is connected to the actuator. A supporting member that supports the objective lens so as to be movable in at least two dimensions is provided with a reflective surface, and the reflective surface In addition, since the position detection light source and the light receiving member that receives the light beam from the position detection light source reflected by the reflective surface are arranged in opposition to each other, the bending of the support member during high-speed access is prevented. The light amount distribution of the light receiving element, which is displaced by the reflection angle of the light beam from the position detection light source irradiated onto the reflective surface provided on the support member, can be detected, and the objective lens can be corrected to an appropriate position.

Furthermore, since the structure is cylindrical, it can be made smaller along the axis.

In general, it is not affected by electromagnetic noise,
Control operations can be performed with good viscosity.

Furthermore, there is no need to assemble any member to the objective lens that detects the amount of displacement of the objective lens, which reduces the burden on the supporting member, and accordingly suppresses unnecessary vibrations during normal operation. The sensitivity of focusing control and dragging control allows accurate operation with normal control current.

[Brief explanation of the drawing]

1 to 5 relate to the first embodiment of the present invention, FIG. 1 is a schematic sectional view of the main part of an objective lens actuator of an optical pickup, and FIGS. 2 and 3 show the state of displacement of the objective lens. 4 is a cross-sectional side view of the objective lens actuator of the optical pickup, FIG. 5 is a plan view of the objective lens actuator with the yoke holding frame removed, and FIG. 6 is according to the second embodiment of the present invention. 7 is a side view of the optical pickup according to the third embodiment of the present invention, FIG. 8 is a principle diagram showing the operation of the optical pickup, and FIG. 9 is a diagram of the optical pickup according to the conventional example. FIG. 1... Light source, 8... Recording medium, 8a... Recording surface,
21゜51...actuator, 25...holding cylinder,
34...Objective lens, 37.54.56...Supporting member, 39a. 39b... Light receiving member, 41... Light source for position detection, 4
4... Reflective surface. Figure 1 Figure 25 Ellipse Figure 2 Figure 6 Figure 7 Figure 8 Procedure Ne Fu Masa W! (Spontaneous) January 23, 1985 1, Indication of the case 1985 Patent Application No. 18082
6 No. 2, Title of the invention: Optical pickup 3, Relationship with the case of the person making the amendment Patent applicant representative: Toshi Shimoyama Department 4, Agent: 160-5 Date of amendment order: 1. Details of the invention Please correct the explanation column below. 1) Corrected "light emitting diode" in line 10 of page 2 to "laser diode". 2) [Actuator 11] on page 3, line 15, and page 4, line 10, was corrected to ``actuator.'' 3) "Mirror frame 12" on page 4, line 2 and page 6, line 14
” was corrected to “Mirror frame 11.” 4) On page 6, lines 12 and 13, change “(Patent Application No. 1983-)” to “(Patent Application No. 1988-)”
-175218)”.

Claims (1)

[Claims] An objective lens is provided opposite to the recording surface of the recording medium to converge the light beam from the light source onto the recording surface, and this objective lens is connected to an actuator to correct the recording surface at least two-dimensionally. In the optical pickup, a supporting member that supports the objective lens movably in at least two dimensions is provided with a reflective surface, and a position detection light source and a position detection light reflected by the reflective surface are provided on the reflective surface. 1. An optical pickup characterized in that a light-receiving member that receives a light beam from a light source is provided opposite to the light-receiving member.