JPH01125729A - Optical system position detector - Google Patents

Abstract

PURPOSE:To detect the position of a lens with simple constitution by providing a position detecting light source, which projects slit light which is long in the direction perpendicular to a prescribed direction, and a means which changes the output of photosensor. CONSTITUTION:A position detecting light source 5 which projects the slit light which is long in the direction perpendicular to the prescribed direction and photosensor 7 which receives the light from the light source 5 are provided, and the means which changes the output of the photosensor in accordance with the motion in a prescribed direction of a holding member is arranged in the optical path through which the luminous flux projected from the position detecting light source 5 is made incident on the optical sensor 7. A triangular aperture, a triangular photosensor, or a triangular reflecting member is used as this means which changes the output of the photosensor. Thus, the position of the optical system is inexpensively detected with simple constitution without damaging the using efficiency of light.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical system position detection device for detecting the position of an optical system. It is most suitable for an objective lens position detection device for knowing the position of an objective lens for reading information.

[Prior Art] Generally, an optical information recording and reproducing device using an optical disk or a magneto-optical disk is configured such that a spiral tracking guide groove is provided on the disk in advance, and a light spot is irradiated according to the groove. ing. This is called tracking, and for example, a method called a push-pull method is well known.

By the way, in order to make the minute spot on the disk follow the tracking guide groove, a method is usually adopted in which the objective lens is moved relative to the tracking detector. In the push-pull method, as shown in FIG.
The reflected light from the disk passes through a beam splitter 103 and a condensing lens 106, and then passes through a beam splitter 103 and a condensing lens 106, and then passes through two-split sensors 107a and 107b, which are placed at a distance D from the focal point G of the condensing lens. It is configured to receive light at

FIG. 12(b) is a diagram of the two-split sensors 107a and 107b viewed from the front of their light receiving surfaces.

As is well known, in the push-pull method, tracking is performed by comparing the intensity of the ±1st-order light among the light diffracted by the tracking guide grooves (referred to as groups) of the disk with the output of a two-split sensor. There is.

When the rotation of the disk is not eccentric (and the objective lens is not moving relative to the two-split sensor), the intensity distribution of the diffracted light from group 105b becomes symmetrical, as shown in Figure 13 (al). , as shown in FIG. 13(b), the center of spot +08 on the two-split sensor 107 is on the sensor dividing line -F, and the spot +08 on the two-split sensor 107 is located at the sensor dividing line -F.
The 11th-order diffracted light beams 109 and 110 due to D05b are symmetrically incident on each of the two-split sensors.

However, as shown in Fig. 12, if there is a large eccentricity in the rotation of the disk and the objective lens moves by a large amount of δ relative to the two-split sensor, the two-split sensor 1
07 is installed shifted by D from the focal position G, the two-split sensor 10 is installed as shown in FIG.
The center of the spot l11 on 7 is shifted by Δ, and the 11th order diffracted light 112 . Figure 14 (
As shown in a), when +13 becomes asymmetrical, its strength also becomes unbalanced. If you perform tracking servo in this state, the 2-split sensor +07a
In order to perform tracking servo so that the two outputs of , b are equal, the disk 1 is
The spot on 05 will be controlled to be shifted by d with respect to the center of the track.

This will eventually lead to deterioration of the reproduced signal quality and uncertainty in signal recording.Furthermore, when recording information, it is possible that the spot will cover adjacent tracks, and in some cases, information that has already been recorded may be It also leads to destruction. If the positions of the objective lens and the two-split sensor are shifted relative to each other in this way, the above-mentioned problems occur.

In order to improve these drawbacks, a device having a configuration as shown in FIG. 15, for example, has also been proposed.

In the apparatus shown in FIG. 15, a beam splitter +14 is inserted between a half mirror 103 and an objective lens 104, which separates the optical path of the light flux from the light source and the light flux directed toward the reproduced signal detection means, and a part of the light flux reflected from the disk is removed. are guided through the lens 115 to the light receiving surfaces 107a and 107b of the tracking detector. Since these are all carried in the same housing 116, the spot on the detector does not move even if tracking is performed, so the above problem can be solved.

[Problems to be Solved by the Invention] However, the conventional example shown in FIG. 15 has the following drawbacks. First, the configuration is complicated, which is disadvantageous in terms of cost. Furthermore, the weight of the movable part increases, the actuator becomes larger to ensure the necessary actuator capacity, and power consumption also increases. Furthermore, if the beam splitter 114 is placed in the optical path, the efficiency of using the amount of light decreases. Fixing the relative positions of the objective lens and the two-split sensor in this way is one method, but there are many problems.

[Means and effects for solving the problems] An object of the present invention is to provide a means for preventing deterioration of reproduced signal quality and for knowing the position of an objective lens necessary for reliable signal recording. It is an object of the present invention to provide an optical system position detection device which improves the drawbacks of the above-mentioned conventional example and has a simple configuration and does not adversely affect the small amount of actuators.

The above objects of the present invention include at least a light source, an optical system for controlling light from the light source, a holding member for holding the optical system, and means for driving the holding member together with the optical system in a predetermined direction. An optical system position detection device for detecting the position of the optical system of an optical system driving device, comprising: at least a position detection light source that projects a long slit light in a direction perpendicular to the predetermined direction; and a light sensor that receives light from the light source for detecting the same position of liI, and a light beam emitted from the light source for detecting the same position of liI is included in an optical path in which the light flux is incident on the light sensor, corresponding to the movement of the holding member in the predetermined direction. This is achieved by an optical system position detection device characterized in that a means for changing the output of the optical sensor is arranged.

Examples of means for changing the output of the optical sensor with movement in the predetermined direction include a method using a triangular aperture, a triangular optical sensor, and a triangular reflecting member.

[Function] According to the optical system position detection device as described above, a simple configuration consisting of the position detection light source, the slit, and the optical sensor can accurately detect the objective lens (optical system for boat fishing).
Information about the relative position of the two-split sensor and the two-split sensor can be obtained separately from the optical signal obtained from the optical system, and the information obtained from the two-split sensor can be corrected using this information, resulting in accurate tracking. It can be performed. This configuration of the present invention has the following features compared to the configuration shown in FIG.
It has great practical advantages.

[Examples] Hereinafter, the optical system position detection device according to the present invention will be described in detail based on specific examples.

In principle, the present invention can be widely applied to detecting the position of a movable optical system, but as an example, the case where it is applied to an optical information recording/reproducing device will be described. first,
Before explaining the present invention in detail, an outline of an optical head of an optical information recording/reproducing apparatus will be explained with reference to FIG.

In FIG. 2, 11 is a semiconductor laser which is a light source;
2 is a collimator lens for collimating the laser beam, and 3 is an objective lens for focusing the laser beam on the disk 14. The reflected light from the disk 14 is reflected again by the objective lens 3! The light is directed to the V destination and reflected by 13 half mirrors or polarizing beam splitters.

The laser light reflected by I3 enters a servo sensor and an RF (information detection) sensor (not shown).

The objective lens 3 is controlled by the servo sensor output so that the laser beam follows the recording track with the laser beam always focused on the disk 14k, and the RF sensor is used to read out information or address signals recorded on the disk. be done.

The entire system is called an optical head, and the mechanism that moves the objective lens is called an actuator. The objective lens 3 is attached to the movable part of the actuator and is constructed as shown in FIG.

FIG. 1 is a diagram showing an example of the configuration of the present invention.

Figure 1 (A) is a side view of the actuator, (B)
is a diagram seen from the disk side.

1 is a cylindrical bobbin that is the movable part of the actuator,
It is configured to rotate in the direction of arrow a with the bottle 2 as an axis by means of a magnetic coil and a magnet (not shown), and to move up and down in the direction of arrow A. Reference numeral 3 denotes an objective lens, which is constructed integrally with the bobbin 1.

4 is a triangular aperture attached to the bobbin
Then, the light from the light source (LED) 5 attached to the non-movable part of the actuator or the head body passes through the long slit 6 in the focusing direction, and this light also passes through the non-movable part of the actuator or the head main body. The light is received by an optical sensor 7 attached to the bobbin, and a position signal indicating the rotational position of the bobbin, that is, in the tracking direction (direction a) of the objective lens is obtained.

The functions of this embodiment will be explained using FIGS. 3 and 4.

When the bobbin rotates clockwise as shown in FIG. 3, the light that has passed through the slit 6 enters the triangular aperture 4 on the side closer to the apex, and the output of the optical sensor 7 becomes smaller. On the other hand, when the bobbin is rotated counterclockwise, it becomes as shown in FIG. 4, and the light passing through the slit 6 is incident on the side closer to the base of the triangle, and the output of the optical sensor 7 becomes larger.

When the bobbin is in the reference position and not rotating, the sensor output indicates the reference output.

Therefore, the bobbin rotation position and the output of the amplifier 7 are
The relationship will be as shown in the figure. In other words, a signal corresponding to the position 1n of the objective lens is obtained by the output of the optical sensor 7.

(Example 2) In the above example, the amount of light passing through the triangular aperture corresponds to the position of the objective lens, but the same can be achieved by attaching a triangular reflecting member to the bobbin as follows. You can get the following functions.

That is, as shown in FIG. 6, a triangular reflecting member 15 is attached to the bobbin seal, and an optical sensor 16 is fixed at a position where it can receive light from the reflecting member 15 on the same side as the light source.

In this case, when the bobbin rotates clockwise or counterclockwise, the output of the optical sensor 16 becomes small and large, respectively, as shown in Fig. 7.8, and the output of the optical sensor 16 becomes small and large, respectively, as shown in Fig. 5. A relationship like this is obtained.

(Third Embodiment) Furthermore, as shown in FIG. 9, the same function can be obtained by configuring the light from the slit 5 to be received by a triangular optical sensor 17 provided on the movable part of the actuator.

In other words, when the bobbin rotates clockwise or counterclockwise, light hits the triangular optical sensor 17 as shown in Figures 1θ and 11, so the output becomes small and large, respectively, as shown in Figure 5. A relationship like this is obtained.

Note that the signals obtained in each of the above embodiments are fed back to the output of the tracking error signal by a conventionally known method, so that accurate tracking can be performed.

In addition, in the first to third embodiments described above, if a light 1 adjustment mechanism (not shown) is provided to reduce changes in the light intensity of the light source over time, fluctuations in light intensity after lighting, etc., the accuracy of lens position detection can be improved. It can be further increased.

The present invention is not limited to the above-mentioned embodiments, and various modifications and applications are possible.

For example, although the above description has been made regarding the case where the actuator is of a bobbin rotating type, the same function can be achieved in other systems by installing a triangular aperture or a reflective member in the movable part of the actuator. Moreover, the installation location can be set at any location as long as it does not interfere with other functions of the actuator movable part.

FIG. 16 is a diagram showing a schematic diagram of one configuration of such an objective lens driving device. Figure 16 (A) Perspective view % (B
) is a view seen from the Z direction. In the figure, 3 is an objective lens, 30 is a tracking coil, 31 is a focusing coil, 32 is a holding member for the objective lens, 33 is a support rod, and 34 is a fixing portion. In FIG. 1, this objective lens driving device moves in the Z direction by the action of a focusing coil 31 and a magnet (not shown), and moves in the Y direction by the action of a tracking coil 30 and a magnet (not shown).

Therefore, the support rod 33 is made of an elastic member that can be bent in both the Y and Z directions.

It is clear that the light source 5, slit 6, and optical sensor 17 of the present invention that can detect the movement of the holding member 32 in the tracking direction Y can also be applied to this objective lens driving device. Note that FIG. 1 shows, as an example, a case where a triangular optical sensor 17 is applied.

Further, in the description of each of the above embodiments, five triangles are used as means for changing the output of the optical sensor in response to the movement of the holding member (for example, the actuator movable part) in the predetermined direction (for example, the tracking direction). mouth opening,
Although the optical sensor and the like are shown, the movement is not only triangular but also substantially in the predetermined direction (for example, the tracking direction)! It is clear that the present invention can be implemented with any shape that changes the output of the optical sensor in response to the ratio of the optical sensor.

[Effects of the Invention] As explained above, according to the optical system position detection device of the present invention, it is possible to know the position of the optical system with a simple configuration, at low cost, and without impairing light utilization efficiency. Ta. In particular, when the present invention is applied to the detection of the objective lens of an optical head,
Information on the objective lens position is necessary for accurate tracking when using a disk with a large eccentricity, and by applying a servo to fix the objective lens position B during rapid access, it is possible to It becomes possible to measure the improvement of signal quality.

[Brief explanation of the drawing]

FIG. 1, FIG. 6, FIG. 9, and FIG. 16 are diagrams for explaining the present invention in detail, respectively. FIG. 2 is a diagram illustrating the outline of the head of the optical information recording/reproducing apparatus Fffi. Section 3.4.5, 7, 8. +0. Each of the Figures I1 is a detailed illustration of the present invention. 12 to 14 are diagrams each explaining the push-pull method. FIG. 15 is a diagram illustrating a conventional example. l: Bobbin 2: Bin 3: Objective lens 4: Aperture 5: Light source (LED) 6: Slit 7.16.17: Optical sensor 15: Reflective member agent Patent attorney Jo Taira Yamashita Figure 5 Figure 6 n Figure 7 j5 Figure 12 Figure 13 Figure 14 Figure 15 i

Claims (4)

[Claims] (1) An optical system comprising at least a light source, an optical system for controlling light from the light source, a holding member for holding the optical system, and means for driving the holding member together with the optical system in a predetermined direction. An optical system position detection device that detects the position of the optical system of a system driving device, at least a position detection light source that projects a long slit light in a direction perpendicular to the predetermined direction;
an optical sensor that receives light from the light source, and further includes an optical sensor that corresponds to the movement of the holding member in the predetermined direction during an optical path in which the light beam projected from the position detection light source enters the optical sensor. An optical system position detection device characterized in that a means for changing the output of the optical sensor is arranged. (2) The means for changing the output of the optical sensor is a triangular opening attached to the holding member, and light reception through the opening is performed by the optical sensor attached to a part other than the holding member. An optical system position detection device according to claim 1. (3) The means for changing the output of the optical sensor is a triangular reflecting member attached to the holding member, and light reception via the reflecting member is performed by the optical sensor attached to a part other than the holding member. An optical system position detection device according to claim 1. (4) The optical system position detection device according to claim 1, wherein the means for changing the output of the optical sensor is a triangular optical sensor itself attached to the holding member.