JPS5982640A - Optical head device - Google Patents

Abstract

PURPOSE:To make a tracking controlling signal free from error by fixing a photodetector on the moving end of a parallel spring and fixing the relative position in the tracking direction between an objective lens and the photodetector. CONSTITUTION:The tracking parallel spring 21 consists of two plate springs and one end part 24 of each plate spring is fixed on a fixed supporting member to form a fixing end. The other end part side is coupled through a coupling part 25 to form a moving end and constituted so that the two plate springs are kept at parallel state. Even if the objective lens in a lens barrel 23 is displaced in the tracking direction, the photodetector follows up the displacement of the objective lens and moves and the relative position of both the photodetector and objective lens in the tracking direction is not changed by attaching the photodetector to the coupling part 25 with adhesives or the like. Consequently, a far field image on the photodetector is not displaced, i.e. an optical head device free from error in a tracking control signal is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides optical recording of audio signals, video signals, etc.
! The present invention relates to an optical head device used in an optical disk device for recording and reproducing information, and particularly relates to an optical head device (f'f-) using the far field method.

An optical disk device tracks a light spot along one (13) circular or concentric information track on an optical disk. This is called tracking. As a method for detecting errors in this tracking, information track tracking is performed. A far-field method is known that uses diffracted light from ε!1 PI (a), (b), and (e).

The laser beam is focused by an objective lens 1 onto an information track groove 2 on the disk. The depth of this groove 2 is often one-eighth of the wavelength of the laser beam used. The laser beam is then diffracted by the information track #)2 and reflected by the optical disk. At this time, depending on the relative position of the objective lens 1 and the information track groove 2, the light intensity distribution of the far field image formed by reflection from the original disk becomes specific. FIG. 1(b) shows a state when the center of the objective lens 1 and the center of the information track groove 2 coincide, and the light intensity distribution is symmetrical. Also, Figure 1 (a), (b)
1 and 2 are cases in which the center of the objective lens 1 and the center of the information track groove 2 do not coincide with each other, and the light intensity distribution is asymmetric.

In this way, the light intensity distribution becomes symmetrical or asymmetrical depending on the relative position of the objective lens 1 and the information track fI2, so the signal for controlling the tracking position, that is, the tracking control signal, is parallel to the information track groove 2. This can be obtained by introducing the above-mentioned far field image to two photodetecting sections divided into two, and finding the difference output between the two photodetecting sections. Then, the position of the objective lens in the tracking direction is controlled by this tracking control signal, and the state shown in FIG. Make it.

However, in optical head devices using such a far-field method, those in which only the objective lens is moved have a drawback that the tracking control signal includes an error. FIG. 2 is a diagram illustrating the occurrence of errors. However, a focusing error detection optical system and a quarter-wave plate, which are not directly related to the explanation, are not shown. The light emitted from the semiconductor laser 1o is converted into parallel light by a collimator lens 9, and its optical path is bent by a beam splitter 8. Then, the objective lens 1 focuses the light onto the optical disk. The light reflected by the optical disk enters a photodetector 7 consisting of two detection sections 7a and 7b. When the information track groove 2 is displaced to the position 2', the objective lens 1 is moved to the position 1' by tracking control.
Displaced to the position. Therefore, the principal light of objective lens 1 @15
is displaced to the position 16. For this reason, the photodetector 7
The far field image formed above is from 11 to 1
However, the photodetector 7 remains at the same position and does not move.

As described above, when the relative positions of the objective lens 1 and the photodetector 7 in the tracking direction shift, the far field image on the photodetector is displaced, and this displacement causes an error to be included in the tracking control signal. Become. In order to eliminate this error, conventional optical head devices perform tracking by rotating all optical elements such as a semiconductor laser, beam splitter, and focusing drive magnetic circuit together with a photodetector around a rotation axis. It has been known. However, in addition to the photodetector, this optical head device must also drive a semiconductor laser, an optical element, and a commercially available focusing drive mechanism, which increases the weight of the drive unit. This has the disadvantage that the size of the optical head becomes large, and as a result, the entire optical head device becomes large.

SUMMARY OF THE INVENTION An object of the present invention is to solve these drawbacks and provide an optical head device that has a very simple groove edge and does not cause tracking errors.

In order to achieve such an object, the optical head device according to the present invention has one end of each of the two plate springs fixed to a fixed support part to serve as a fixed end, and the other end side fixed to the fixed support part. Two leaf springs are connected to each other so as to remain parallel to form a moving end, and the moving end has a parallel spring movable in the tracking direction, and an objective lens fixed to the moving end and movable in the focusing direction. In an optical head device having a lens barrel, a photodetector is fixed to a moving end of the parallel spring,
By fixing the relative positions of the objective lens and the photodetector in the tracking direction, the tracking control signal is configured to contain no errors.

Next, the principle of the present invention will be explained based on FIGS. 6(a)' and 6(b). Note that (,) is a plan view, and (b) is a front view.

The tracking parallel spring 21 is made of two leaf springs, each of which has one end 24 fixed to a fixed support member to form a fixed end. The other end is connected via a connecting portion 25 to form a moving end, and the two leaf springs are configured to remain parallel. Also, orthogonal to this parallel tracking spring 21, one end of a parallel focusing spring 22.22 is continuous with the coupling portion 25, and a lens barrel 26 is attached to the other end. In such a configuration, when the lens barrel 26 moves in the tracking direction, the tracking parallel plane is moved? 1,
The focusing spring 22 and the coupling part 25 are moved in parallel in the tracking direction by the same amount as the lens barrel 2, using the fixed end of the trunking parallel spring as a fulcrum, as shown by the broken line 22' in the figure. 11.

Therefore, even if the objective lens in the lens barrel 26 is displaced in the dragging direction by attaching the photodetector to the coupling part 25 with adhesive or the like, the photodetector will not move following the displacement of the objective lens. , the relative positions of both in the tracking direction do not change, and therefore an optical head device in which the far-field image on the photodetector does not shift, that is, the tracking control signal does not contain any error, can be realized.

Embodiments of the present invention will be described below based on the drawings.

FIGS. 4(a) and 4(b) are structural explanatory diagrams of an optical head device according to an embodiment of the present invention. Figure (8) is a plan view, and Figure (b) is a longitudinal sectional view.

The configurations of the tracking parallel spring 21 and the tracking spring 22 are similar to those shown in FIGS. 6(a) and 6(b), and the fixed ends 24.24 of the trunking parallel spring 21. is the optical head outer cylinder 3 as an identification support part.
2 with set screws 67, respectively. A photodetector 26 is attached to the inner wall of the joint 25 by adhesive or the like.
Parallel focusing spring 22.
22 passes through the hole 32m of the optical end tube 52, and the lens barrel 26 is attached to the end thereof. Lens barrel 2
An objective lens 1 is inserted into the tip of the lens 6, and a heat filter 64 is placed below the objective lens 6, and the splitter filter 4 is fixed to the substrate 6. This splitter 64 introduces the laser beam into the objective lens 1 and guides its reflected light to the photodetector 26 through the hole 65 of the lens mirror @26.

Further, a coil 61 is wound around the outside of the upper part of the lens barrel 26, and this coil filter 1 and the lens barrel 26 are connected to each other.
A ring-shaped yoke 27 is inserted between the groove and the outer peripheral wall of the coil 61, and a ring-shaped permanent magnet 28 and a yoke 29 are arranged outside the trench and the coil 61.

These yokes 27, 29 and permanent magnets are both fixed to the inner wall of the optical head outer cylinder 62.

The above parts constitute a focusing drive circuit, and by supplying a current to the excitation 1 to the coil 61, an electromagnetic force acts between it and the permanent magnet 28, and it is integrated with the coil filter 1. Lens barrel 23, that is, objective lens 1
can be controlled to move in 7 orcasing directions FD. Although not shown, driving in the tracking direction TD may be performed by providing a tracking Ijl at circuit orthogonal to the focusing coil 61 or by any other suitable method.

An upper plate 60 is attached to the upper part of the optical head outer cylinder 62, and this upper plate 60 is provided with a hole 30a through which the tip of the lens barrel 2 passes. In addition, the outer cylinder 6 for optical
The lower end portion of 2 is fixed to the board 33 with a set screw 6B.

The optical head device consisting of the above (Ita configuration) is explained in FIG. As shown above, the tracking parallel spring 2
1 is also displaced, and the photodetector 26 is displaced by the same amount as the tracking displacement amount, so the relative positions of the objective lens 1 and the photodetector 26 in the tracking direction TD do not change.

In addition, the focusing drive mechanism allows the lens barrel 26 to
Move the objective lens 1 in the focus direction FD @j
When doing so, the focus sync parallel spring 22 is displaced and controlled in the same way as the tracking parallel spring 1 described above.

FIGS. 5(a) and 5(b) are structural explanatory diagrams of an optical head device according to another embodiment of the present invention. FIG. 5(a) is a plan view including a partial cross section, and FIG. 2(b) is a longitudinal sectional view.

The same reference numerals as in FIGS. 4(a) and 4(b) indicate the same or equivalent parts.

The support frame 46 has a cylindrical bottom with a recessed portion.
A set of upper and lower crown springs 41° 41 is fixed within the frame. This crown spring 41°41 constitutes a focusing parallel spring 471.

At the center of the crown spring 41, there is a lens barrel 26.
is attached, and an objective lens 1 is inserted into its tip. Furthermore, a focusing drive mechanism consisting of the same yoke 31, yoke 27, 29 and permanent magnet 28 as described in FIGS. ing. York 2
7.29 and the permanent magnet 28 are 1τ1 (by this focusing drive mechanism fixed to the outer tube 46 by a material 48, the lens barrel 26, that is, the objective lens 1, is controlled to move in the focusing direction FD.

An outer cylinder 46 is provided on the outside of the support frame 46, and a plate spring 47 is connected between the protrusion 49 on the upper inner wall of the outer cylinder 46 and the bottom outer peripheral wall of the support frame 46. This spring 47 is attached symmetrically to the center of the support frame 43. Therefore,.

Support frame 45 (t, this spring 47, 47
It is now supported by This splash 47°4
7 constitutes a tracking parallel spring, the end of the spring 47 on the outer frame 46 side corresponds to a fixed end, and the end on the support frame 43 side corresponds to a moving end. A photodetector 26 is attached to a recessed portion of the support frame 46 that is integrated with this moving end. Further, on the outside of the four parts, the focusing drive device fi? A tracking seat movement mechanism 44 made of similar members is attached to control the movement of the support frame 46, that is, the objective lens 1 of the lens barrel 2 in the tracking direction T'D. This tracking drive machine 47444 is
It is constructed so that it can be assembled by being held by the support member 45 and inserted from the outside of the outer cylinder 46, thereby facilitating the assembly work. The prism 42 inserted into the hole /l 3 a of the recess serves as a beam splitter and a light introduction path, and is fixed to the outer cylinder 46.

Of course, this prism 42 is not fixed to the outer cylinder 46,
It may be configured integrally with the photodetector 26.

In the optical head device having the above configuration, when the support frame 4'5 is pre-excited by the tracking drive mechanism 44 and the movement of the objective lens 1 of the lens barrel 2'6 is controlled +111,
Since the springs 47 and 47 are displaced and the objective lens 1 and the light beam 26 are displaced by the same amount in the tracking direction TD, the relative positions of the objective lens 1 and the photodetector 26 in the tracking direction TD change. stomach.

Further, when controlling the movement of the objective lens 1 of the lens barrel 26 in the focusing direction FD by the focusing drive mechanism, the crown springs 41 and 41 are moved by the springs 47 and 4 described above.
The displacement and control are performed in the same manner as in case 7.

In the above embodiment, the focusing spring includes:
Although examples using flat rjfIJ', springs, and crown springs have been shown, any type of spring member may be used as long as it supports the objective lens in the focusing direction.

As described above, in the optical head device according to the present invention, by mounting the photodetector at the moving end of the tracking parallel spring (=I), the relative relationship between the objective lens and the photodetector in the tracking direction is achieved during tracking. position 11'4. does not change,
For this reason, a tracking system that does not include errors (fI'll
Signals can be obtained and highly accurate tracking is possible. Furthermore, as described above, since it is sufficient to simply fix the photodetector to the moving end with an adhesive or the like, the structure of the optical head is simple and miniaturized.

[Brief explanation of the drawing]

Diagrams explaining that errors are included, Figure 6 (a), (
b) is a diagram explaining the present invention in detail, FIGS. 4(a) and (b)
) is a structural explanatory diagram of an optical head device according to one embodiment of the present invention, and FIGS. 5(a) and 5(b) are structural explanatory diagrams of an optical head device according to another embodiment of the present invention. 1...Objective lens, 2...] Information track groove, 21...
...Parallel spring for tracking, 22...Parallel spring for focusing, 26...Lens barrel, 41...Crown spring (parallel spring for focusing), 4 pieces...0
7. Ti. (parallel blade for tracking). Agent: Patent Attorney Mitsuru Kimura, Figure 4, Figure 5

Claims (2)

[Claims] (1) One end of each of the two leaf springs is fixed to a fixed support part to form a fixed end, and the other end is connected to each other so that the two leaf springs remain parallel to each other in the tracking direction. An optical head device having a parallel spring as a movable moving end, and a lens barrel fixed to the moving end of the parallel spring and having an objective lens movable in a focusing direction,
The photodetector was fixed to the moving end of the parallel spring! (
Optical head device with special features. (2) The digital camera head device according to claim 1, wherein the rectangular tube is configured to be movable in the focusing direction by a second parallel spring integrally configured with the parallel spring.