JPH0636500Y2 - Optical head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of an optical head used for recording / reproducing information on / from an optical disc such as an audio disc, a video disc and a data disc.

There is a strong demand for miniaturization of optical disk devices, and for this purpose, it is essential to realize a thin optical head itself. For example, in FIG. 6 of Japanese Patent Laid-Open No. 55-117745, a light source is arranged below the lens driving device with respect to the optical disc, and light is emitted from the light source in parallel with the optical disc surface and the light is half mirrored. Discloses an optical head in which the light is reflected in a direction perpendicular to the optical disc surface and directed toward the lens. However, when the light source is arranged below the lens driving device with respect to the optical disc, the height of the optical head is increased. The size becomes large, and it becomes difficult to reduce the thickness of the optical disk device.

The barrels of Japanese Utility Model Publication No. 58-35134 and Japanese Utility Model Publication No. 58-62448 (both designated by reference numeral 2).
When the dimensions in the focusing direction of the L-shaped protruding portion in which the arm and the arm portion (both of which are indicated by reference numeral 3) are integrated and the coil holding portion to which the focusing coil is fixed are compared, Is getting bigger. With such a configuration, it is a disadvantage to make the device thinner. Furthermore, there is no description of the positional relationship of the elements of the optical system, and it is unclear how to reduce the height of the optical head.

According to the present invention, the assembling work of the optical head becomes remarkably efficient, and the size of the optical head in the direction perpendicular to the medium surface of the disc-shaped recording medium can be remarkably reduced. As a result, an inexpensive and compact optical disc device can be realized. It is an object of the present invention to provide an optical head that greatly contributes to

The optical head of the present invention comprises a base that extends along the medium surface of a disk-shaped recording medium on which information is recorded in a track shape, and is movably arranged on the base and parallel to the medium surface. At a first position along a direction intersecting the radial direction of the medium surface at
A movable member having a first portion and a second portion, the thickness dimension of which in the focusing direction perpendicular to the medium surface is smaller than that of the second portion, and is fixed to the first portion. A lens having a lens optical axis parallel to the focusing direction, a focusing coil and a tracking coil fixed to the second portion, and the lens is arranged on the opposite side of the disc-shaped recording medium. And a reflecting member fixed to the base and bending an optical path in a substantially perpendicular direction; and a reflecting member arranged on the base, the split being formed by a plane including the lens optical axis and extending in the radial direction. Of the two spaces, the first space and the second space, the light source and the photodetector arranged in the first space, and the tracking space arranged in the second space. And a focusing coil and magnetic field generating means for directing a magnetic flux to the coils, and the reflecting member, the focusing coil, and the tracking coil intersect one plane parallel to the medium surface. The light from the light source is projected to the disk-shaped recording medium through the reflecting member and the lens, and the reflected light is received by the photodetector through the lens and the reflecting member. It is characterized by having done.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing the structure of an example of the main part of the optical head of the present invention. In this example, the linearly polarized elliptical beam from the semiconductor laser 1 is made to enter the polarizing prism 3 as a parallel light flux by the collimator lens 2 and transmitted through the polarizing film 4, and the transmitted light is totally reflected at a right angle by the reflecting prism 5. After passing through the λ / 4 plate 6, the elliptical beam is guided to the objective lens 7 so that the major axis direction of the elliptical beam becomes the tangential direction of the optical disk (not shown) and projected in a spot shape on the optical disk. The reflected light from the optical disc follows the same optical path as the outward path up to the polarization prism 3 and enters the polarizing film 4, but in the return path, the polarization direction is orthogonal to the polarization direction of the outward path due to the action of the λ / 4 plate 6. Therefore, all the returning light is reflected by the polarizing film 4. The return light from the optical disc reflected by the polarizing film 4 is reflected once by the optical surface 8a of the critical angle prism 8 to form four light receiving regions 9a to 9d divided into two in the radial direction and the tangential direction of the optical disc. These light-receiving regions 9a to 9a ...
A data signal, a focus error signal and a tracking error signal are obtained from the output of 9d.

The optical surface 8a of the critical angle prism 8 is set so that the incident angle of the return light from the optical disc with respect to the optical axis becomes substantially a critical angle. A multilayer antireflection coating is applied as described in JP-A-57-122410.
Further, the incident surface of the polarizing film 4 of the polarizing prism 3 and the optical surface 8a of the critical angle prism 8 are arranged so that the incident angle to the critical angle prism 8 is P-polarized light and the incident surface to the optical surface 8a is in the tangential direction. The polarizing prism 3 and the critical angle prism 8 are integrated by adhesion or the like in order to make the incident surfaces orthogonal to each other and to reduce the deviation due to thermal expansion and contraction due to temperature fluctuations of these incident surfaces.

On the other hand, the lens holder 11 has a first portion 10 and a second portion 31 which are sequentially arranged along a direction intersecting the radial direction of the disc-shaped recording medium. The objective lens 7 is fixed to the first portion 10, and the focusing coil 12 and the tracking coil 13 are fixed to the second portion 31. With respect to the wall thickness of the recording medium in the direction perpendicular to the medium surface (focusing direction), the wall thickness of the first portion 10 is smaller than the wall thickness of the second portion 31.

In this embodiment, the lens holder 11 is slidable in the optical axis direction of the objective lens 7 and is rotatably engaged with the shaft 14 via a bearing in a plane orthogonal to the optical axis. By generating a magnetic flux in a direction orthogonal to the direction of the current flowing through the focusing coil 12 and the tracking coil 13, the objective lens 7 is passed through the second portion and the first portion.
Along with linearly displacing in the direction of the optical axis and displacing in an arc in a plane orthogonal to the optical axis, focus servo and tracking servo are performed so that the light spot follows the center of the track of the optical disk in the focused state. To

2A and 2B are a cross-sectional view and a plan view showing a specific structure of the optical head shown in FIG. The semiconductor laser 1 is held by an inner frame 21, and the inner frame 21 is screwed through a spring 23 to an outer frame 22 so that the position of the inner frame 21 can be adjusted in the beam emission direction.
Fixed by 24. The outer frame 22 is provided with a diaphragm 25 for narrowing the beam from the semiconductor laser 1 and holds the collimator lens 2 for collimating the beam.
Are fixed to the substrate 26 with screws 27. Further, as shown in FIGS. 3A and 3B, the integrated polarizing prism 3 and critical angle prism 8 adjust the incident angle of the return light from the optical disc on the optical surface 8a of the critical angle prism 8 with respect to the optical axis. In order to obtain it, it is held by a rotating member 28 rotatably provided with respect to the substrate 26. Furthermore, a reflecting prism and a λ / 4 plate 6
Are integrated with each other by adhesion or the like and fixed to the substrate 26.

Further, the focusing coil 12 is wound on the surface of the second portion 31 of the lens holder 11 which is perpendicular to the surface of the recording medium, and the tracking coil 13 is fixed on the surface of the focusing coil 12. There is. The first part 10 holding the objective lens 7 and the second part fixing the above two types of coils
The lens holder 11 which is an integrated structure with the portion 31 is supported by the substrate 26 via the elastic member 33 so as not to hinder the displacement thereof. Further, a cylindrical inner yoke 35 is provided inside the second portion 31 so as to be connected to the yoke 34, and a pair of permanent magnets 36a and 36b are fixed to the outer yokes 37a and 37b on the outer side so as to face each other. A magnetic flux that crosses the focusing coil 12 and the tracking coil 13 is generated between each of the pair of permanent magnets 36a and 36b and the inner yoke 35, and the magnetic flux and the focusing coil 12 and the tracking coil 13 are generated. The second portion 31 is displaced along the shaft 14 to perform the focus servo, and the shaft 14 is rotated about the shaft 14 to perform the tracking servo, depending on the magnitude and the direction of the current applied to the. Further, other parts except the objective lens 7 are covered with a case 30. FIG. 2B is a plan view showing a partial cross section with the case 30 removed. The shaft 14 is attached to the substrate 26 via the shaft fixing collar 32 and the yoke 34.

On the other hand, the photodetector 9 is fixed to the end of the arm 39 with the screw 38. The arm 39 is formed integrally with a cylindrical holding member 40 that is arranged so as to surround the outer frame 22 that holds the collimator lens 2. The holding member 40 moves so that the photodetector 9 moves in a direction orthogonal to the optical axis of the return light from the optical disc that enters through the critical angle prism 8 and rotates about the linear movement direction. The supporting member 41, which is formed in a substantially U-shape on the substrate 26, supports the holding member 40 so as to be slidable in the axial direction and rotatable about the axis, and the displacement of the holding member 40 is held by the holding member 40. The member 40 is configured to be regulated by being pressed and fixed to the support member 41 by a pressing plate 42 having elasticity.

The fixing mechanism of the photodetector 9 will be described below with reference to FIGS.
Further details will be described with reference to C and FIG.

The support body 41 is configured by providing two blocks 43 and 44 on the substrate 26 so as to face each other with a space therebetween. These blocks 43, 44 are formed with arcuate receiving surfaces 43a, 44a for supporting the cylindrical holding member 40 so as to be slidable in its axial direction and rotatable about its axis. A female screw 45 is formed on the upper surface of the block 43, and a rectangular step portion 46 and a through hole 47 penetrating from the bottom surface of the step portion 46 are formed on the upper surface of the other block 44.
The pressing shaft 48 is fitted to the step portion 46 formed in the block 44 so as not to rotate, and the screw 49 is screwed into the female screw 48a formed in the pressing shaft 48 through the through hole 47. The elastic pressing plate 42 has a screw hole 42a through which the screw 50 penetrates at one end.
Is formed with a notch 42b which is engaged with the pressing shaft 48 at the other end and which is open at one end and extends in the lengthwise direction, and an opening 42c is formed at the central part of the holding member 40 at this part. The elastic piece 42e is made to project obliquely downward from the flat portion 42b so as to abut.
Are formed and configured. Note that FIG. 4A shows a plan view of only the support member 41, and FIGS. 4B and 4C show cross-sectional views before and after the holding member 40 is pressed and fixed to the support member 41 by the pressing plate 42. The figure shows an exploded perspective view of the fixing mechanism.

In this example, first, as shown in FIG. 4B, the block 43 is passed through the screw hole 42a formed at one end of the pressing plate 42 through the screw 50.
Is fixed to the block 43 by screwing it into the female screw 45 formed on the block 43, and the notch 42b formed on the other end of the press plate 42 is fitted to the step 46 of the block 44. Engage with shaft 48. Next, as shown in FIG. 4C, the holding shaft 40 is pulled into the step portion 46 by rotating the holding shaft 48 until the lower surface of the holding shaft 48 contacts the bottom surface of the step portion 46 as shown in FIG. 4C. The pressing plate 42 elastically presses and fixes it to the support member 41.

According to this structure, the pressing shaft 48 fits into the step portion 46 and does not rotate, and the pressing plate 42 that engages with the pressing shaft 48 is provided.
The notch 42b is formed so as to extend in the lengthwise direction and be open, and its engaging position changes depending on the depth of fitting of the holding shaft 48 to the step portion 46, so that the holding member 40 is pressed and fixed. Even if the screw 49 is rotated, the rotational couple does not act on the pressing plate 42, and the support member 41 is not distorted. Therefore, the holding member 40 can be reliably pressed and fixed without displacement. When the holding member 40 is displaced to adjust the position of the photodetector 9, only the elastic piece 42e of the pressing plate 42 is in contact with the holding member 40, that is, the holding member 40 is pressed only by the elastic piece 42e. As shown in FIG. 2A, the holding member 40 is loosened as shown in FIG.
Since the pin 51 can be stood upright from the outside, there is no play between the holding member 40 and the support member 41,
Therefore, the position can be adjusted easily and surely.

The optical head of the present invention is provided with a base (for example, the substrate 26) extending along a medium surface of a disk-shaped recording medium on which information is recorded in a track shape, and movably arranged on the base. A first portion (for example, the first portion 1) parallel to the medium surface and along a direction intersecting the radial direction of the medium surface.
0) and a second portion (for example, the second portion 31) and the thickness of the first portion is smaller in the focusing direction perpendicular to the medium surface than in the second portion. (For example, the lens holder 11), a lens fixed to the first portion and having a lens optical axis parallel to the focusing direction, and a focusing coil fixed to the second portion (for example, the focusing portion). Coil 12) and a tracking coil (for example, the tracking coil 13), and a reflecting member that is arranged on the opposite side of the lens from the disk-shaped recording medium and is fixed to the base to bend the optical path in a substantially perpendicular direction. (For example, the reflection prism 5) and the one disposed on the base, which is a plane including the lens optical axis and extending in the radial direction. First space being divided form and a second
Of the two spaces, the light source (for example, the semiconductor laser 1) and the photodetector (for example, the photodetector 9) arranged in the first space, and the light arranged in the second space. The coil includes a tracking coil, the focusing coil, and a magnetic field generating unit for directing a magnetic flux to the coils (for example, the permanent magnet 36 and the yoke 35), and the reflecting member, the focusing coil, and the tracking coil. Is arranged at a position crossing one plane parallel to the medium surface, the light from the light source is projected onto the disk-shaped recording medium via the reflecting member and the lens, and the reflected light is the lens, The light is received by the photodetector through a reflecting member.

With this configuration, the present invention has the following effects.

An optical-related member including a light source and a photodetector in each of a first space and a second space divided and formed by a plane including a lens optical axis and extending in a radial direction of a medium surface, and focusing. Since the coil, the tracking coil, and the electromagnetic-related member composed of the magnetic field generating means are completely separated and arranged on the same base, overcrowding can be avoided in the arrangement of the member and the member related to light and electricity can be avoided. Since the members related to magnetism are grouped according to their functions and arranged substantially horizontally on the same base, the assembling work of the optical head becomes extremely efficient.

Further, the light-related member and the electromagnetic-related member are separately arranged in a first space and a second space on the base, and a reflecting member, a focusing coil and a tracking coil are provided on the medium surface. Since the optical head is arranged at a position intersecting with one parallel plane, the dimension of the optical head in the focusing direction can be easily reduced, and as a result, the optical head becomes extremely thin.

[Brief description of drawings]

FIG. 1 is a perspective view showing the structure of an example of the main part of the optical head of the present invention, and FIGS. 2A and 2B are sectional and plan views showing the specific structure of the optical head shown in FIG. 1, and FIG. A and B are partial detailed views of FIG. 2, and FIGS. 4A, B, C and 5 are diagrams for explaining the structure of the fixing mechanism of the photodetector shown in FIG. 1 ... Semiconductor laser, 2 ... Collimator lens 3 ... Polarizing prism, 4 ... Polarizing film 5 ... Reflecting prism, 6 ... λ / 4 plate 7 ... Objective lens, 8 ... Critical angle prism 8a. Optical surface, 9 ... Photodetector 9a-9b ... Light receiving area, 10 ... First part 11 ... Lens holder 12 ... Focusing coil 13 ... Tracking coil 14 ... Shaft, 21 ... Inner frame 22 …… Outer frame, 23 …… Spring 24 …… Screw, 25 …… Aperture 26 …… Substrate, 27 …… Screw 28 …… Rotating member, 30 …… Case 31 …… Second part, 32 ...... Shaft fixing collar 33 ...... Elastic member, 34 ...... Yoke 35 ...... Inner yoke, 36a, 36b ...... Permanent magnet 37a, 37b ...... Outer yoke, 38 ...... Screw 39 ...... Arm, 40 ...... Holding member 41 ... Supporting member, 42 ... Holding plate 42a ... Screw hole, 42b ... Notch 42c ... Opening part, 42d ... Flat part 42e ... Elastic piece, 43,44 ... Block 43a, 44a …… Receiving surface, 45 …… Female thread 46 …… Step, 47 …… Through hole 48 …… Pressing shaft, 48a …… Female thread 49 …… Screw, 50 …… Screw

Claims (1)

[Scope of utility model registration request] 1. A base, which extends along the medium surface of a disk-shaped recording medium on which information is recorded in a track form, and a movably arranged on the base and parallel to the medium surface. It has a first portion and a second portion along a direction intersecting the radial direction of the medium surface, and has a thickness dimension in the focusing direction perpendicular to the medium surface that is larger than that of the second portion. A smaller movable member, a lens fixed to the first portion and having a lens optical axis parallel to the focusing direction, a focusing coil and a tracking coil fixed to the second portion, A reflecting member which is arranged on the side opposite to the disk-shaped recording medium with respect to the lens and which is fixed to the base and bends an optical path in a substantially perpendicular direction, and which is arranged on the base. A light source and a photodetector arranged in the first space among two spaces, a first space and a second space, which are divided and formed in a plane including the optical axis of the lens and extending in the radial direction; The tracking coil arranged in a second space, the focusing coil, and a magnetic field generating unit for directing a magnetic flux to the coils, and the reflecting member, the focusing coil, and the tracking coil. Arranged at a position intersecting with one plane parallel to the medium surface, the light from the light source is projected onto the disk-shaped recording medium through the reflecting member and the lens, and the reflected light is the lens and the reflecting member. The optical head is characterized in that the light is received by the photodetector through the light.