JPS6236735A - Optical pickup - Google Patents

Abstract

PURPOSE:To improve the assembling job efficiency and to reduce the manhour and the cost, by performing freely the relative position control among a position detecting part, a light source for position detection and on of photodetecting members against other members. CONSTITUTION:In case an objective lens 34 has no displacement, the control is carried out so as to secure the coincidence among the optical axis of a light emitting element 41, a dividing line 39c of a photodetecting element 39 in the tracking direction and the center of a detecting part 44 respectively. Thus the difference of the output voltage is equal to zero between the photodetecting areas 39a and 39b of the element 39. While said difference of output voltage is proportional to the displacement of the lens 34 when this lens 34 has a displacement. Then a current proportional to the output voltage difference flows to the tracking coils 33a and 33b through a feedback action. Thus, a closed loop is formed for a servo system and the lens 34 is held with control at the position of the displacement zero in the tracking direction T. Thus the lens 34 is corrected despite the effects caused by the undesired vibrations in a high- speed access mode, etc. As a result, a reading or writing action is quickly started.

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. 9 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, and reaches a reflection prism 5 via a beam splitter 4. Then, the parallel light beam reflected in the 90° direction by the reflecting prism 5 is reflected by the 174-wave plate 6.
The light beam passes through the objective lens 7 and forms a light spot with a diameter of about 1 μm on the bit P formed on the recording surface 8a of the recording medium 8 such as a compact disk.

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

At this time, since this reflected light passes through the quarter-wave plate 6 twice in a round trip, its polarization direction is perpendicular to the forward polarization direction and is totally reflected in the 90° direction by the polarizing film 4a. The totally reflected return light from the recording surface 8a passes through the cylindrical lens 9 and enters the photodetector 10.

This photodetector 1o has a light-receiving area divided into two in the radial direction and the full 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, in response to the focus error signal and the tracking error signal, the focus control mechanism and tracking servo mechanism of the actuator 11 connected to the objective lens 7 are driven to slightly move the objective lens 7 and record its focus. A correction operation is performed so that the light spot is aligned with the recording surface 8a of the medium 8 and accurately follows the pit P provided on the track.

By the way, as shown in FIG. 10 (cross-sectional side view of main parts),
The lower end of the lens frame 12 that holds the objective lens 7 is connected to a pair of parallel tracking leaf springs 1 erected on the holding tube 13.
4, and the upper and lower surfaces of the holding cylinder 13 are further supported by a pair of parallel focusing springs 15 disposed in the horizontal direction. Slight movement of the lens 7 in two-dimensional directions is prevented.

Further, the focus 4 novo mechanism or the tracking servo mechanism of the actuator 11 is configured such that a focus error signal or a dragging error signal is fed back only during normal recording and reproducing operations. Therefore, for example, the circuit of the focus servo mechanism or the i-racking servo mechanism during high-speed access is in an OFF state.

Therefore, the rapid acceleration and deceleration of the key 17 during high-speed access causes the parallel leaf springs 14, 15, etc. to vibrate, causing unnecessary vibrations in the objective lens 7.

As a result, the positioning accuracy of the pickup is reduced, or each servo mechanism becomes uncontrollable, resulting in problems such as a delay in access time.

To deal with this, for example, in Japanese Patent Application Laid-open No. 58-26331, the position of the objective lens is detected using a capacitance 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 signal linear, and the sensor diameter is large, making it unsuitable for miniaturizing optical pickups. do not have. Furthermore, there is a possibility that it will be affected by electromagnetic noise from the outside.

In addition, there is also a type that performs tracking control by rotating a mirror by a predetermined angle using an actuator, which reflects the luminous flux from the light source toward the objective lens, such as disclosed in Japanese Patent Application Laid-Open No. 57-94942. In this optical pickup, in order to eliminate unnecessary vibrations that occur in the mirror during high-speed access, an angular position detection Vi position is used 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 Jin's 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, Vtl becomes larger as a whole and its structure becomes more complicated.

In order to deal with the above problems, the applicant filed the first
As shown in FIG. 0 and FIG. 11, a position detecting section 16 bent into an L shape is provided on the side of the lens frame 12, and a light source 17 and a light source 17 are divided into two with this position detecting section 16 in between. By detecting the output voltage difference from the two-divided light-receiving surface of the light-receiving member 18, it is possible to perform feedback control during access, thereby eliminating the need for high-speed access. An invention has been disclosed in which even if the objective lens 7 receives vibrations, a correction operation is performed immediately.

By the way, the main body portion 17a of the light source 17 has a yoke 19.
It is fitted into a round hole 19c drilled in a. Also,
Main body body 18b of the light receiving member 18 facing the light source 17
Also, the other yoke 19a is arranged parallel to the yoke 19a.
It is similarly fitted into the round hole 19 bored in 9b (see FIG. 12).

Further, a ring-shaped recess 20 integrally formed with the position detection section 16 is fitted and fixed to the lens frame 12.

In such a configuration, the positional relationship of each of the component parts 16 to 18 is determined at the same time as assembly. For example, due to errors in the manufacturing process or assembly of parts, the center of the position detection unit 16 is moved by Δa to the right from the line connecting the optical axis of the light source 17 and the division a18a of the light receiving member 18, as shown in FIG. If the dividing line 18a of the light-receiving member 18 deviates from the line connecting the optical axis of the light source 17 and the center of the position detection unit 16 by an amount of Figure (The vertical axis is from the output voltage (Pl) of one light-receiving surface of the light-receiving member 18 to the output voltage (Pl) of the other light-receiving surface (
As shown by the broken line or the two-point wi line in the pictorial diagram (in which the horizontal axis shows the position of the objective lens), the actual voltage difference Ofl is Δa in the horizontal direction from the set center position of the objective lens. It shifts by Δb.

As a result, it becomes difficult to accurately detect the position of the light-receiving member 18 within the position-detectable region ±α. The same applies when the optical axis of the light source 17 is deviated from the line connecting the dividing line 18a of the light receiving member 18 and the center of the position detecting section 16 in the - direction.

In addition, in order to accurately match the center of the position detection unit 16, the optical axis of the light source 17, and the dividing line 18a of the light receiving member 18, the manufacturing process and assembly of the yokes 19a and 19b must be performed with precision and Light source 17. The manufacturing process and attachment of the light receiving member 18 requires strict control of viscosity. Similarly,
The center of the position detection section 16 is aligned with the dividing line 18 of the light receiving member 18.
In order to match the angle a, the lens frame 1 of the light receiving member 18 must be
The length of the protrusion from 2 must be strictly controlled based on part processing accuracy.

As a result, there are problems in that the manufacturing and assembly process becomes complicated, requires skill, increases the number of work steps, and increases the product cost. It is difficult to fully guarantee component accuracy and assembly accuracy.

[Object of the Invention] The present invention has been made in view of the above circumstances, and it is possible to set the relative positions of the position detection unit, the light source, and the light receiving member to high precision without severely affecting the precision of the parts and the assembly precision. As a result, it is an object of the present invention to provide an optical pickup that can reduce the number of man-hours and reduce the cost of the product.

[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 In the device that is connected to an actuator and performs a correction operation on the recording surface at least two-dimensionally, the objective lens is provided with a position detection section, and a position detection light source and a light receiving member are connected with the position detection section in between. are arranged opposite to each other, and at least one of the position detection section, the light source for position detection, and the light receiving member is adjustable in position relative to other members, and the assembly of parts is sometimes performed using position detection. By relatively moving at least one of the light source, the light source for position detection, and the light receiving member, the position of each member can be adjusted.

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

1 to 4 relate to a first embodiment of the present invention, in which FIG. 1 is a schematic plan view of the main part of an objective lens actuator of an optical pickup, and FIG. 2 is a perspective view showing a state in which a light receiving member is attached to a yoke. 3 is a cross-sectional side view of the objective lens actuator of the optical pickup, and FIG. 4 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 J3-shaped cross section and an annular shape as a whole is formed.
, 24b are fixedly installed, and these yokes 24a, 24b
A magnetic circuit is formed by the permanent magnet 23 and the permanent magnet 23 . Furthermore, Coke 24a.

A gap is formed between 24b. Furthermore, a holding cylinder 25 is disposed within the outer frame 22.

This holding cylinder 25 has a substantially cylindrical middle part 25 with openings at both ends.
a, and a coil holding cylinder part 25b that is integrally formed in a concentric cylinder shape on the outside of this middle cylinder part 25a and has one end (upper end side) open.
It is formed from. A focusing voice coil 26 is wound around the outer periphery of the coil holding cylinder portion 25b. A voice coil 26 for casing is wound around this coil.

One end (upper) frontage side of the coil holding cylinder part 25b is inserted into and out of the gap forming the yokes 24a and 24b'c so that the voice coil 26 faces the permanent magnet 23.

Further, in the holding cylinder 25+, a spacer 2 is provided at the upper end of the middle cylinder part 25a, and above the yoke 24a.
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 spacer 2 disposed at the lower end side of the outer frame 22 at the lower end side of the middle cylinder part 25a.
9, and is attached to the outer frame 22 by a focusing spiral spring 28a similar to that described above. That is, the holding cylinder 25 has a focusing spiral spring 28a,
28b, it is supported by the outer frame 22 so as to be movable in its axial direction (optical axis direction).

Further, a yoke holding frame 30 is attached to the inside of the outer frame 22 above the focusing spiral spring 28a.
This yoke holding frame 30 has a pair of first and second rings formed in a bar shape and arranged parallel to the tracking direction -'.
Fixed yokes 31a, 31b, and the first and second fixed yokes 31a.

Two pairs of first and second permanent magnets 32a and 32b connected to both ends of magnet 31b are provided.

Tracking coils 33a, 33b are wound approximately at the center of the first and second fixed yokes 31a, 31b. The tracking coils 33a, 33b
The first and second fixed yokes 31a and 31b are wound with
An objective lens 34 is disposed between them. The objective lens 34 is mounted on 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 a pair of elastic elements are formed in this gap to allow movement of the objective lens 34 in the tracking direction T) in the direction intersecting the optical axis. Tracking leaf spring 37 consisting of members.
One end of 37 is inserted and fixed. Further, the other end of the tracking square plate spring 37, 37 is inserted into the holding cylinder 25 and fixed inside the lower end of the holding cylinder 25.

On the other hand, as shown in FIGS. 1 and 2, a horizontally elongated hole 31c in the tracking direction T is bored in the first fixed yoke 31a on the side closer to the first permanent magnet 32a. This hole 3
The cylindrical main body body 38a of the light receiving element fixing member 38 is inserted into the 1C and fixed by means such as adhesive. Further, a light receiving element 39 is formed into a circular tube on the front surface of the light receiving element fixing member 38, and light receiving areas 39a and 39b are provided on the light receiving element 39, which are divided into two in the tracking direction from a central dividing line 39c. .

Note that the light receiving areas 1t39a, 39b' of this light receiving element 39
A tracking current proportional to the output voltage difference of the detected light M is applied to the transformer coils 33a and 33b.

Further, a horizontally elongated hole 31d extending in the same direction as the second fixed yoke 31b is also bored in a portion of the second fixed yoke 31b that faces the hole 31c of the first fixed yoke 31a. The cylindrical main body portion 40a of the light emitting element fixing member 40 is inserted into the hole 31d and fixed by adhesive or other means. A light emitting cord 41, which is an example of a light source, is fixed to the front surface of the light emitting element fixing member 40.

Further, reference numeral 42 is a position detection member formed by processing a thin plate material, etc., and includes a mounting portion 43.

A detecting section 44 that is elongated from one side of the mounting section 43 and bent in a right angle direction (downward in the figure) is shown on the right. Further, the detection section 44 is located at the center of the mounting section 43.
A horizontally long mounting hole 43a is drilled along the direction of
This attachment hole 43a is attached to the lens frame 35, and its bottom surface is placed on the magnetic member 36 (fixed by means such as attachment).

In addition, in the optical pickup, the optical axis of the light emitting element 41, the segment υ1 line 39c provided at the center of the light receiving cable 39, and the center of the plate thickness of the detecting part 44 of the position detecting member 42 are coincident with each other. Assembled in the same condition.

It is being

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

First, an explanation will be given of the adjustment work for aligning the optical axis of the light emitting cable 41 of the assembly opening, the dividing line 39c of the light receiving element 39, and the center of the plate height of the detection unit 44.
1 optical axis and the portion of the light-receiving cord 39 υjI! If the thickness center of the detecting part 44 of the position detecting member 42 deviates in one direction from the line connecting the position detecting member 42 to the lens frame 35, the position detecting member 42 attached to the lens frame 35 can be attached in the longitudinal direction of the mounting hole 43a. , move it in the tracking direction shown by the arrow in the figure.

At the gate, the output voltage difference in the amount of light received from the light emitting cord 41 detected between the light receiving regions 39a and 39b of the light receiving element 39 is observed with a monitor, etc., and when this output voltage difference becomes 0, the above-mentioned position is detected. The member 42 is fixed to the magnetic member 36 and the lens frame 35. As this fixing means, for example, an ultraviolet curing adhesive 71 may be used.

In addition, if the optical axis of the light emitting element 41 and the center of the plate thickness of the detection part 44 coincide with J3, and the dividing line 39C of the light receiving element 39 is biased in one direction, the light receiving element 39 is fixed. The light receiving element fixing member 38 is moved in the tracking direction (arrow direction in the figure) along the hole 31c formed in the first fixed yoke 31a, while the light receiving area 39a of the light receiving element 39 is moved.
, 39b is observed with a monitor or the like, and when this output voltage difference becomes ○, the light receiving element fixing member 38 is fixed to the first fixed yoke 31a by the same means as described above. .

Furthermore, if the dividing line 39c of the light receiving element 39 and the center of the plate thickness of the detecting part 44 match, and the optical axis of the light emitting cable 41 is shifted in one direction, the light emitting element 41 is fixed to the light emitting element 41. Drill the element fixing member 40 into the second fixing yoke 31b, JQ
The light receiving area 39 of the light receiving element 39 is moved in the tracking direction (in the direction of the arrow in the figure) along the hole 31d.
Observe the output voltage difference between the amounts of received light detected by a and 39b with a monitor, etc., and when this output voltage difference reaches O, the light emitting element fixing member 40 is fixed to the second fixing yoke 31b by the same means as described above. let

Note that the optical axis of the light emitting element 41 and one part of the light receiving element 39
17JI! j39c and the center of the plate thickness of the detection part 44 occurs relative to each other due to the effects of component manufacturing processing errors and assembly errors. The amount of light received is 1#! 39
Adjust fI! so that the output voltage difference during operation detected by a and 39b becomes a value as shown by the solid line in FIG. ! do.

Next, the operation will be explained.

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, and the objective lens 34 is displaced in the tracking direction F due to the deflection deformation of the focusing spiral springs 28a and 28b. Furthermore, when the tracking coils 33a and 33b are supplied with the tracking current, the tracking plate spring 37
, 37, the objective lens 34 is displaced in the tracking direction T.

Next, when the objective lens 34 moves in the tracking direction T due to a high-speed access operation, the position detection member 42 is displaced along with the movement, and the detection portion 44 is emitted from the light emitting element 41 and is directed to the light receiving element 39. The received light 3 distribution is changed. When the objective lens 34 is not displaced, the optical axis of the light emitting element 41 and the tracking direction of the light receiving element 39 are divided! ! If J3 is adjusted in advance so that i+39c and the center of the detection section 44 coincide with each other, the output voltage difference between the light receiving areas 39a and 39b of the light receiving cable 39 will be O.

Furthermore, when the objective lens 34 is displaced, the detection unit 44
The light distribution is proportional to the displacement of the objective lens 34, and the output voltage difference between the light receiving regions 39a and 39b of the light receiving element 39 is proportional to the displacement of the objective lens 34. A current proportional to this output voltage difference is fed back to flow through the tracking coils 33a and 33b to form a servo system closed loop, and the objective lens 34 is controlled to be maintained at a zero displacement position in the tracking direction T. 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.

Further, FIG. 5 (a plan view of the main part) and FIG. 6 (a diagram explaining the adjustment operation) show a second embodiment of the present invention.

An attachment hole 43a formed in the attachment portion 43 of the position detection member 42 in this embodiment is rotatably attached to the outer periphery of the lens frame 35 that holds the objective lens 34. Also, the center of the plate thickness of the detection part 44 protruding from one side of the mounting part 43 is the distance between the optical axis of the light emitting element 41 and the light receiving element 39 υ1\A3
It has a protruding length extending outward by ΔC from the line connecting 9c. This deflection length -C is determined based on manufacturing process errors and assembly errors of each component.

During adjustment, the position detection member 42 is rotated around the lens frame 35, and the diagonal 44a of the detection section 44 is rotated.

The center of the line connecting 44b is aligned with the line that intersects the line connecting the light beam of the light emitting element 41 and the Pi line 39C of the light receiving element 39, and the detection unit 44 detects the light receiving area 39a.

39b so as to equally block light. Of course, this adjustment is performed while observing the output voltage difference between the light receiving regions 1139a and 1139b of the light receiving element 39 on a monitor. The magnetic member 36 and the lens frame 35 are
Glue and fix.

Fig. 7 (perspective view of main parts) shows a third embodiment of the present invention, in which a light-receiving element fixing member 38 is formed in an L-shape, and an upper surface 38a and a side surface 38a of this light-receiving element fixing member 38 are shown. is brought into sliding contact with the first fixed yoke 31a, and this first
Light receiving element fixing member 38 using fixed yoke 31a as a guide
Slide it in the direction of the arrow in the figure, that is, in the dragging direction, adjust it so that the dividing line 39c of the light-receiving element 39 is aligned with the optical axis of the light-emitting element 41 (see Figure 1), and fix it by means such as a mount. .

In this case, if the light receiving element fixing member 38 is provided with a clip 38c that sandwiches the outer surface of the first fixing yoke 31a as shown in FIG. 8 (side view), the light receiving element fixing member 38 can be fixed to the first It can be moved in the tracking direction while being attached to the yoke 31a.

Of course, this third embodiment can also be applied to the light emitting element fixing member 40. Further, according to this embodiment, the first
There is no need to drill holes 31c and 31d in the fixed yoke 31a or the second fixed yoke 31b as in the first embodiment, and processing and assembly are simplified.

Note that the present invention is not limited to the above-mentioned embodiments; for example, one or two of the light receiving element 39, the light emitting element 41, and the detecting section 44 may be fixed in advance to the fixed yokes 31a, 31b or the lens frame 35. It may be something that exists. Further, although adjustment of the tracking direction is shown in each of the embodiments shown in the figures, for example, in FIG.
If one of the holes 31c and 31d drilled in b is bored vertically in the focus direction F, adjustment in both the tracking direction and the ° focus direction becomes possible.

[Effects of the Invention] As described above, according to the present invention, an objective lens that converges a light beam from a light source onto the recording surface of a recording medium is provided opposite to the recording surface of the recording medium, and this objective lens is connected to an actuator. In the objective lens, a position detection section is provided in the objective lens, and a position detection light source and a light receiving member are connected to each other with the position detection section in between. are arranged opposite to each other, and at least one of the position detecting section, the light source for position detection, and the light receiving member is adjustable in position relative to the other members, so that the position detecting section and the light source for position detection are The relative position of the light-receiving member and the light-receiving member can be set with high precision without strict component accuracy and assembly accuracy, improving the efficiency of manufacturing and assembly work.
The number of work steps can be reduced, and the cost of the product can also be reduced.

[Brief explanation of drawings]

1 to 4 relate to a first embodiment of the present invention, in which FIG. 1 is a schematic plan view of the main part of an objective lens actuator of an optical pickup, and FIG. 2 shows a state in which a light receiving member is attached to a yoke. 3 is a cross-sectional side view of the objective lens actuator of the optical pickup, FIG. 4 is a plan view of the objective lens actuator with the yoke holding frame removed, and FIG.
is a plan view of the main part of an optical pickup according to a second embodiment of the present invention, and FIG. 6 is an arrangement of FIG. ! ! Operation explanatory diagram, FIG. 7 is a perspective view of the main part according to the second embodiment of the present invention, ':jI
Figure B is a side view showing a modification of Figure 7, Figure 9 is a principle diagram showing the operation of the optical pickup, Figures 10 to 14 are conventional examples, and Figure 10 is an optical pickup. 11 is a plan view of the same, FIG. 12 is a perspective view showing a state in which the light receiving member is attached to the yoke, and FIG.
Figures 14 and 14 are schematic diagrams illustrating the positional deviation of the position detection unit, the light source for position detection, and the light receiving member in each manner, and Figure 15 shows the output voltage (Pl) of one light receiving surface of the light receiving member on the vertical axis to the output voltage (Pl) of the other light receiving surface of the light receiving member. It is a diagram showing the value obtained by subtracting the output voltage (P2) of the light receiving surface and the position of the objective lens on the horizontal axis. 1... Light source, 8... Recording medium, 8a... Recording surface,
21...actuator, 30..."-retaining part,
31a. 31b...Fixed yoke, 31c, 31d...Horizontal hole, 34...Objective lens, 38a, 40a...Body body, 39...Light receiving member, 39C...Parting line, 41...
...Light source for position detection, 42...Member for position detection, 4'
3a...Several holes, 44...Position detecting section. Fig. 1 vgz Fig. 1'lJ Prison size Fig. 5 Fig. 10 Fig. 7 Fig. 8 SF, Fig. 9 Fig. 110 Fig. 11 Fig. 15 Fig. 15 Procedure net) Pressure use (voluntary) November 5, 1985 2 , Title of the invention Optical pickup 3, Relationship to the case of the person making the amendment Patent applicant

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, the objective lens is provided with a position detection section,
A position detection light source and a light receiving member are arranged opposite to each other with the position detection unit in between, and the position of at least one of the position detection unit, the position detection light source, and the light receiving member is adjusted relative to the other member. An optical pickup characterized by being flexible.