JPH04103037A - Objective lens driving device - Google Patents

Abstract

PURPOSE:To improve the position detecting sensitivity by executing a position detection in a place the moving amount for moving together with a movement of an objective lens is large. CONSTITUTION:In the case a movable part 2 moves in the direction as indicated with an arrow A, the light quantity of a reflected light 11b becomes larger than the light quantity of a reflected light 11a, and accordingly, an output signal 12b becomes larger than an output signal 12b, by which a differential output signal 16 becomes a negative output. On the other hand, in the case the movable part 2 moves in the direction as indicated with an arrow B, the light quantity of the reflected light 11a becomes larger than the light quantity of the reflected light 11b, and accordingly, the output signal 12a becomes larger than the output signal 12b, by which the differential output signal 16 becomes a positive output. In such a way, the position detecting sensitivity of an objective lens is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an objective lens and a drive device for an optical head used in an optical disk device, and particularly to a position detection mechanism for the objective lens.

[Prior Art] Conventionally, this type of objective lens driving device is shown in FIG. 5(a),
As shown in (b) and (c), the movable parts 2 holding the objective lens 1 are parallel to each other and the objective lens l
is supported by one end of a pair of focusing leaf springs 3a, 3b which are movable in a direction parallel to the optical axis of the focusing leaf springs 3a, 3b, and the other end of the focusing leaf springs 3a, 3b holds the relay plate 4 between them. Further, a tracking leaf spring 5 movable in a direction perpendicular to the optical axis of the objective lens 1 is fixed to the center portion of the relay plate 4 surrounded by the focusing leaf springs 3a and 3b. The other end of the tracking leaf spring 5 is located between the focusing leaf springs 3a and 3b, and is attached to the center of a U-shaped fixing part 6. On the other hand, the movable part 2 includes a focusing leaf spring 3a,
3b and the tracking plate spring 5 to respectively displace the objective lens l in the optical axis direction and in a direction perpendicular to the optical axis.

A reflective film 7 is formed on the opposite surface of the relay plate 4 to which the tracking leaf spring 5 is fixed.

Further, a light emitting diode 8 faces the center of the reflective film 7, light receiving sensors 9a and 9b are arranged perpendicularly on a plane parallel to the optical axis of the objective lens 1 on both sides of the light emitting diode 80, and a tracking plate spring is arranged on both sides of the light emitting diode 80. 5 in a line parallel to the direction of motion. The irradiated light 10 from the light emitting diode 8 is reflected by the reflective film 7, and the reflected light lea and Ilb are received by the respective light receiving sensors 9a and 9b.

In this case, when the movable part 2 is subjected to a force perpendicular to the optical axis of the objective lens 1 by the driving part and the tracking plate spring 5 is bent, the relay plate 4 is tilted and the reflected light from the reflective film 7 is The reflection angles of 11a and Jlb change, causing a difference in the amount of light. It is detected by each light receiving sensor 9a.

9b and output signals 12a and 12b, which are amplified by a differential amplifier 15 to obtain a differential output signal 16. By detecting the magnitude of the differential output signal 16, the output signal 12a and 12b are output. Performing position detection.

[Problems to be Solved by the Invention] In the conventional objective lens driving device described above, the problem as shown in FIG. 6(a)
As shown in , the objective lens 1 is not moving at all, there is no difference in the amount of reflected light 11a and llb, and the differential output signal 16 is zero. Figure 6(b) shows
In a state where the objective lens 1 is moved in the six directions of the arrow, the relay plate 4 rotates counterclockwise about the tracking leaf spring 5 as a fulcrum, and each reflected light 1ia, ll from the reflective film 7 is reflected.
b moves in the direction of arrow B.

However, the amount of change in movement of the relay plate 4 that moves along with the movement of the lens 1 is very small because the movement is near the fulcrum. Therefore, the change in the amount of reflected light 11a, llb from the light emitting diode 8 due to the movement of the reflective film 7 is very small. That is, there is a drawback that the position detection sensitivity of the objective lens 1 is low.

SUMMARY OF THE INVENTION An object of the present invention is to provide an objective lens driving device with high sensitivity for detecting the position of an objective lens.

[Means for Solving the Problems] In order to achieve the above object, the objective lens drive device according to the present invention includes an objective lens, a movable part, a focusing leaf spring, a tracking leaf spring, and two An objective lens driving device having a reflective film and a pair of light emitting element and light receiving element, the objective lens condensing light from a light source onto the surface of an optical disc medium, and the movable part comprising: an objective lens; The focusing leaf spring supports the movable part so that it can be displaced in the focusing direction parallel to the optical axis of the objective lens, and the tracking leaf spring supports the movable part so that it can move in the focusing direction parallel to the optical axis of the objective lens. The two reflective films are disposed on the surface of the movable part where the objective lens is located.
It is arranged in the tracking direction and symmetrically with respect to the optical axis of the objective lens, and the paired light emitting element and light receiving element are respectively installed at fixed positions corresponding to each reflective film, The position of the objective lens is detected by transmitting and receiving light through a reflective film.

Furthermore, the objective lens driving device according to the present invention includes an objective lens, a movable part, a focusing leaf spring, a tracking leaf spring, four reflective films, and a pair of a light emitting element and a light receiving element. An objective lens driving device comprising: an objective lens that focuses light from a light source onto an optical disk medium surface; a movable part that holds the objective lens; and a focusing leaf spring that is movable. The tracking plate spring supports the movable part so as to be movable in the tracking direction perpendicular to the optical axis of the objective lens. Of the four reflective films, two reflective films are placed on the surface where the objective lens of the movable part is located, and the remaining two reflective films are placed on the reflective surface.
They are arranged symmetrically with respect to the optical axis of the objective lens in the tracking direction, and a pair of light emitting elements and light receiving elements are respectively installed at fixed positions corresponding to each reflective film. , the position of the objective lens is detected by transmitting and receiving light through a reflective film.

[Operation] Position detection is performed at a location where the amount of movement associated with the movement of the objective lens 1 is large. Therefore, it becomes possible to obtain a larger output signal, and the position detection sensitivity of the objective lens is improved. [Embodiment] Next, the present invention will be described with reference to the drawings.

(Example 1) FIGS. 1(a), (b), (c), and (d) are diagrams showing Example 1 of the present invention, and FIG. 1(a) is a front view,
(b) is a side view, (c) is a plan view, and (d) is a perspective view.

The present invention comprises: an objective lens 1 that focuses light from a laser diode onto the surface of an optical disk medium; a movable part 2 that holds the objective lens; Focusing leaf springs 3a, 3b parallel to each other and movable in the focusing direction, and a relay plate 4 supporting the other end of the focusing leaf springs 3a, 3b.
, a tracking plate spring 5 that is movable in a tracking direction perpendicular to the optical axis of the objective lens unit, and a fixed part that supports the relay plate 4 via the tracking plate spring 5.

Furthermore, the movable part 2 has two reflective films 7a and 7b on the surface where the objective lens is located in the tracking direction,
and an objective lens], and light emitting diodes 8a and 8b are installed opposite to each of the reflective films 7a and 7b, and further, each of the light emitting diodes 8a and 8b is A light receiving sensor 9a is provided on the same plane and parallel to the tracking direction.

9b are arranged in parallel. Then, the reflected lights lea and Ilb reflected by the reflective films 7a and 7b are sent to each light receiving sensor 9a,
9b receives the output signal 12 of the light receiving sensors 9a and 9b.
a and 12b are amplified by a differential amplifier 15 to obtain a differential output signal 16.

FIGS. 2(a), 2(b), and 2(c) are diagrams showing the principle of the embodiment of the present invention. FIG. 2(b) shows a state in which the objective lens l has not moved at all, and the reflected light 11
There is no difference in the amount of light between the reflected light a and the reflected light 11b, so the differential output signal 16 is zero.

As shown in FIG. 2(a), when the movable part 2 moves in the arrow △ direction (tracking direction), the amount of reflected light 1]11 becomes larger than the amount of reflected light lea, and therefore the output Since the signal 121J is larger than the output signal 12a, the differential output signal 16 becomes a negative output.

As shown in FIG. 2(c), when the movable part 2 moves in the direction of arrow B (tracking direction), the amount of reflected light 11a becomes larger than the amount of reflected light 11b, and therefore the output signal 12a is larger than the output signal 12b, so that the differential output signal 16 becomes a positive output. According to the first embodiment described above, the objective lens position detection sensitivity is improved because position detection is performed at a location where the amount of change in movement is large (the location farthest from the fulcrum) that moves along with the movement of the objective lens l. I can do it.

(Example 2) In Example 1, when the movable part 2 moves in the focusing direction, the position detection sensitivity may decrease. Second
Figures (d), (e) and (e) are diagrams for explaining the influence on position detection sensitivity when the movable part moves in the focusing direction. Here, since the light source of the light emitting diode is a diffused light, the output of the light receiving sensor arranged facing each other varies depending on the distance, and similarly, the output of the light receiving sensor also fluctuates.

FIG. 2(e) shows a state similar to FIG. 2(b) in which the movable part 2 has moved in the six directions of arrows (tracking jig direction).

Here, as shown in FIG. 2(d), when the movable part 2 moves in the six arrow directions (tracking direction) and also moves in the arrow C direction (focusing direction), the reflective film 7a
, 7b and the light receiving sensors 9a, 9b become smaller, so the amount of reflected light 11a, Ilb increases.

Therefore, since the output signals 12a and 12b both become large, a differential output signal 16 that is larger than that in the state where the focusing direction is not moved as shown in FIG. 2(e) is obtained. Contrary to the case in FIG. 2(d), the movable part 2 moves in the six directions of the arrows, and the focusing direction)
FIG. 2(f) shows the state in which it has been moved to this point. In this case, the reflective films 7a and 7b and the light receiving sensor 9a.

Since the distance from 9b increases, the reflected light]], a,
The light amount of Ilb decreases. Therefore, the output signal 12
a.

+2b are both small, so that the differential output signal 16 becomes smaller in the focusing direction in FIG. 2(e) than when the lens is not moving.

Embodiment 2 of the present invention provides an objective lens driving device that solves the drawbacks of Embodiment 1.

FIG. 3(a), (b), and (c) are Embodiment 2 of the present invention.
FIG. 3(a) is a front view, FIG. 3(b) is a side view, and FIG. 3(c) is a plan view.

In this embodiment, reflective films 7a are provided at four locations on the movable part 2,
7b, 7c, and 7d are provided. That is, two reflective films 7a are provided on the surface of the movable part where the objective lens 1 is located.

7b, and the remaining two reflective films 7c and 7d are installed on the surface opposite to the surface where the objective lens 1 is located. Its installation structure is the same as in the first embodiment. Also, a reflective film 7a.

A light emitting diode 8a faces each of 7b, 7c, and 7d.

8b, 8c, and 8d are installed, and furthermore, on the same plane as each of the light emitting diodes 8a, 8b, 8c, and 8d, light receiving sensors 9a, parallel to the tracking direction are installed.
9b, 9c, and 9d are arranged in parallel. Then, the reflected light l reflected by the reflective films 7a, 7b, 7c, and 7d
ea, llb, llc, and lad each light receiving sensor 9
a.

9b, 9c, and 9d, the light receiving sensors 9a and 9c
The sum signal of the output signals 12a and 12b is obtained, and the sum output signal 14a is obtained, and the output signal 1 of the light receiving sensors 9a and 9b is obtained.
Take the addition signals of 2b and 12a and output the addition output signal 14b.
The two added output signals 14a and 14b are amplified by the differential amplifier 15 to obtain the differential output signal 16.

Figure 4 (a), (b), (c), (d), (e
) and (f) are front views showing the principle of Example 2 of the present invention. FIG. 4(b) shows a state where the objective lens 1 is not moving at all, and there is no difference between the sum of the light amounts of the reflected light 11a and llc and the sum of the light amounts of the reflected light 11b and the reflected light +1d. , the addition output signal 14a and the addition output signal +4b are equal, so the differential output signal 16 becomes zero. When moving in the six directions of arrows (tracking direction) as shown in FIG. 4(a), the sum of the amounts of reflected light 11b and 11d becomes larger than the sum of the amounts of reflected light 11a and 11c, The addition output signal 14b is larger than the addition output signal 14a. Therefore, the differential output signal 1
6 is a negative output. As shown in Figure 2(c), arrow B
Direction (tracking direction): When moving 2 times, reflected light 1
The sum of the amounts of light 1a and reflected light i1c becomes larger than the sum of the amounts of reflected light 11b and reflected light lad, and the addition output signal 1
4a is larger than the addition output signal 14b. Therefore, the differential output signal 16 becomes a positive output.

FIGS. 4(d) and (eL(f)) are front views showing the case where the movable part 2 moves in the tracking direction and also in the focusing direction. FIG. 4(e) shows
This shows a state in which the movable part 2 moves in the entry direction (tracking direction) and does not move in the focusing direction.

FIG. 4(d) shows that the movable part 2 moves in the direction A (tracking direction) and in the direction of arrow C (focusing direction).
It also shows that it is moving. In this case, Fig. 4(e)
Comparing the cases, the amounts of reflected light 11a and 11b increase, and the amounts of reflected light 11c and 11d decrease. However, from the sum of the light amounts of the reflected light 11a and the reflected light 11c, an addition output signal 14a, the reflected light 11b and the reflected light 11
An addition output signal +4b is obtained from the sum of the light amount with d, and further 1
Since the differential output signal 16 is obtained from the added output signals of 4a and 14b, the differential output signal 16 in FIG. 4(e) and the differential output signal 16 in FIG. 4(cl) become equal signals. .

Further, FIG. 4(f) shows a state in which the movable portion 2 is moving in the six directions of arrows (tracking direction) and also in the direction of arrows (focusing direction). In this case, compared to the case of FIG.
The amount of light increases. However, reflected light 11a and reflected light 11c
An addition output signal 14a is obtained from the sum of the light amounts of 1, and an addition output signal 14b is obtained from the sum of the light amounts of the reflected light 11b and the reflector d,
Furthermore, since the differential output signal 16 is obtained from the addition output signals 14a and 14b, the differential output signal 16 in FIG. 4(e) and the differential output signal 16 in FIG. 4(g) become equal signals.

As described above, according to the second embodiment of the present invention, even when the movable section 2 is moving in the focusing direction, stable objective lens position detection can be performed without being affected by the movement.

Note that the four light receiving sensors 9a and 9b shown in Example 2.

By changing the output signal processing of 9c and 9d, the lens position in the focusing direction can also be detected.

As shown in FIG. 4 (g) + (h) and (1), the sum of the light receiving sensor output signals 12a and 12b is taken, and the sum of the light receiving sensor output signals 12c and 12d is taken, and the sum output signal 14a is obtained.

By obtaining the differential output signal 16 of 14b, the lens position in the focusing direction is detected. In FIG. 4(h), reflected light I Ia, ] lb, ] Ic, I
The light amounts of Id are all equal, so the light receiving sensor output signals 12a, 12b, 12c, and 12d are also all equal, resulting in an addition output signal 14d.

14b are also equal, so the differential output signal 16 becomes zero. As shown in FIG. 4(g), when the movable part 2 moves in the direction of arrow C (focusing direction), the reflected light 11a
, Ilb is larger than the reflected light tic, lid, and the light receiving sensor output signals 12a, 12b
is larger than the light receiving sensor output signals 12c and 12d. Therefore, since the addition output signal 14a is larger than the addition output signal +4b, the differential output signal 16 becomes a positive output. As shown in FIG. 4(1), contrary to FIG. 4(g), when the movable part 2 moves in the direction of arrow D (focusing direction), the amount of reflected light beams 11a and lIb becomes smaller. The amount of the reflected light beams 11c and lld is smaller than that of the reflected light beams 11c and lld, and the light receiving sensor output signals 12a and 12b are smaller than the light receiving sensor output signals 12c and 12d. Therefore, the addition output signal 14a is higher than the addition output signal 14b.
Since the differential output signal 16 becomes smaller, the differential output signal 16 becomes a negative output.

[Effects of the Invention] As explained above, according to the objective lens driving device of the present invention, position detection is not performed in a place where the amount of movement displacement is small as the objective lens moves, as in the conventional example. Since position detection is performed at a location where the amount of movement associated with the movement of the objective lens is large, a larger output signal can be obtained than in the conventional example, and there is an effect that the position detection sensitivity of the objective lens can be improved.

[Brief explanation of drawings]

FIG. 1(a) is a front view showing Embodiment 1 of the present invention, FIG. 1(b)
is the same side view, (c) is the same plan view, (d) is the same perspective view, Fig. 2 (a), (b), (c), (d), (e'
1. (f) is a diagram showing the principle of Example 1 of the present invention,
FIG. 3(a') is a front view showing Embodiment 2 of the present invention;
J) is the same side view, (c) is the same plan view, Fig. 4 (a),
(b), (cl, (dL (eL (f”)+ (
g), (h). (1) is a diagram showing the principle of the second embodiment of the present invention, and FIG.
) is a front view showing the conventional example, (1)) is a side view of the same, (c)
is a perspective view of the same, and FIGS. 6(a) and 6(L) are diagrams showing the principle of the conventional example. 1. Objective lens 2 Movable part 3a, 3
b...Focusing leaf spring 4-Relay plate 5...Tracking leaf spring 6 Identification parts 7, 7a, 7
b, 7c, 7d---Reflection film 8.8a, 8b,
8c, 8d---Light emitting diode 9a, 9b, 9
c, 9d--light receiving sensor 0.10a, 10b, IO
c, 10d...Irradiation light Ia, llb, llc,
1ld-Reflected light 2a, 12b, 12'c, 12d
Output signal 13a, +3b...-summing amplifier 4a,
14b...addition output signal

Claims (2)

[Claims] (1) An objective lens driving device comprising an objective lens, a movable part, a focusing leaf spring, a tracking leaf spring, two reflective films, and a pair of light emitting element and light receiving element, the objective lens driving device comprising: an objective lens; The lens focuses the light from the light source onto the surface of the optical disk medium, the movable part holds the objective lens, and the focusing leaf spring moves the movable part parallel to the optical axis of the objective lens. The tracking plate spring supports the movable part so that it can be displaced in the tracking direction perpendicular to the optical axis of the objective lens, and the two reflective films support the movable part so that it can be displaced in the focusing direction. On the plane where the objective lens is located,
It is arranged in the tracking direction and symmetrically with respect to the optical axis of the objective lens, and the paired light emitting element and light receiving element are respectively installed at fixed positions corresponding to each reflective film, An objective lens driving device characterized in that it transmits and receives light through a reflective film to detect the position of an objective lens. (2) An objective lens driving device comprising an objective lens, a movable part, a focusing leaf spring, a tracking leaf spring, four reflective films, and a pair of light emitting element and light receiving element, the objective lens driving device comprising: an objective lens; The lens focuses the light from the light source onto the surface of the optical disk medium, the movable part holds the objective lens, and the focusing leaf spring moves the movable part parallel to the optical axis of the objective lens. The tracking leaf spring supports the movable part so as to be movable in the tracking direction perpendicular to the optical axis of the objective lens, and the four reflective films are two The reflective film is on the surface of the movable part where the objective lens is located, and the remaining two reflective films are on the reflective surface.
They are arranged symmetrically with respect to the optical axis of the objective lens in the tracking direction, and a pair of light emitting elements and light receiving elements are respectively installed at fixed positions corresponding to each reflective film. An objective lens driving device characterized in that the objective lens driving device detects the position of an objective lens by transmitting and receiving light through a reflective film.