JPH0679384B2 - Objective lens drive - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens driving device for an optical head used in an optical disc device, and more particularly to a mechanism for detecting the position of the objective lens.

[Conventional technology]

FIG. 3 (a) and FIG. 3 (b) are a plan view and a front view of the main part of the conventional objective lens driving device, respectively.

In the figure, the movable part 2 holding the objective lens 1 is held by a pair of focusing leaf springs 3a, 3b which are parallel to each other, and the ends of the focusing leaf springs 3a, 3b are attached to the relay plate 4. . The relay plate 4 is attached to the fixed portion 6 via a single leaf spring 5 for tracking. The pair of focusing leaf springs 3a and 3b are arranged in a direction perpendicular to the focus direction of the objective lens 1, and the tracking leaf spring 5 is arranged parallel to the optical axis of the objective lens 1. A pair of reflection plates 30 are fixed to both side surfaces of the movable part 2, and a pair of reflection type sensors composed of the light emitting diode 8 and the light receiving sensor 9 are arranged on both sides of the objective lens corresponding to the reflection plates 30. The differential output 21 is detected by the differential amplifier 20,
The position of the objective lens 1 was detected.

[Problems to be Solved by the Invention]

Since the above-described conventional objective lens driving device has a configuration for detecting the position variation due to the movement of the reflecting plate 30 attached to the movable portion 2 holding the objective lens 1, the reflecting plate 30 is used for the objective lens 1 Since the end faces cannot be aligned perfectly parallel to the optical axis direction, even if the objective lens 1 moves in the focus direction, it is detected as a slight movement error in the track direction.

Further, since the light emitting diode 8 is composed of two pieces, there is a drawback that two light amount fluctuation differences occur due to the aging of the light emitting diode 8 and an error occurs in the differential output.

[Means for Solving the Problems]

An objective lens driving device of the present invention includes a movable portion that holds the objective lens, and a pair of focusing leaf springs that support the movable portion and that are perpendicular to the optical axis of the objective lens and are parallel to each other.
A relay plate to which the ends of the pair of focusing leaf springs are fixed, a leaf spring for tracking that is attached to a fixed portion that supports the relay plate and is parallel to the optical axis of the objective lens, and the tracking plate for the relay plate. A reflective film formed on a surface substantially perpendicular to the tracking leaf spring on the side opposite to the surface to which the leaf spring is connected, a light source fixed so as to face the reflective film, and the light source for tracking the light source. It includes a pair of light receiving sensors which are arranged on both sides in a direction orthogonal to the leaf spring and which enter the reflected light of the reflecting film emitted from the light source, and a differential amplifier which outputs a difference between outputs of the pair of light receiving sensors. Composed of.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

1 (a) and 1 (b) are a plan view and a front view, respectively, showing an embodiment of the present invention. In the figure, a movable part 2 holding an objective lens 1 is held at one end of a pair of focusing leaf springs 3a, 3b which are parallel to each other, and the other end of the focusing leaf springs 3a, 3b is a relay plate. It is attached to 4. The relay plate 4 is attached to the fixed portion 6 via a single leaf spring 5 for tracking. The focusing leaf springs 3a and 3b are arranged in a direction perpendicular to the focus direction (optical axis direction of the objective lens 7), and the tracking leaf spring 5 is arranged parallel to the optical axis direction of the objective lens 1. . A reflection film 7 is formed on a surface of the relay plate 4 opposite to the supporting portion of the tracking leaf spring 5 and perpendicular to the tracking leaf spring 5. The light emitting diode 8 is fixed to the fixing portion 6 so that the light emitting surface is parallel to the reflection film 7 and faces the reflection film 7. On both sides of the light emitting surface of the light emitting diode 8 in the tracking direction orthogonal to the leaf spring 5 for tracking, a pair of light receiving sensors 9, so that the light receiving surfaces are adjacent to each other on the same surface as the light emitting surface
10 is arranged so that the light emitted from the light emitting diode 8 is reflected by the reflection film 7 and can be received by the light receiving sensors 9 and 10. Moreover, the dimension of the reflective film 7 in the tracking direction is arranged to be approximately half the center distance of the light receiving sensors 9 and 10.

As shown in FIGS. 2 (a) and 2 (b), the objective lens 1 moves in the direction of arrow A, so that an angular displacement θ is generated in the relay plate 4 and the reflection film 7 about the tracking leaf spring 5. Since the positional displacement Δx occurs in the reflective film 7, the area of the reflective film 7 located on the light receiving sensor decreases on the light receiving sensor 9 and increases on the light receiving sensor 10. In addition, when the objective lens 1 is moved in the reverse direction, it is reversed.

Due to the angular displacement θ due to the movement of the objective lens 1 and the position movement Δx of the reflection film 7, the reflected light of the light emitted from the light emitting diode 8 is received by the light receiving sensors 9 and 10 as the displacement of the reflection area of the reflection film 7, and the differential amplifier At 20, a differential output 21 corresponding to the amount of movement of the objective lens 1 is obtained.

Generally, the best detection sensitivity of a reflection type position sensor composed of a light emitting diode, a light receiving sensor and a reflection film is
It is well known that this is obtained when the end of the reflective film is arranged near the center point of the light emitting diode and the light receiving sensor. The conventional objective lens driving device shown in FIG. 3 is similarly arranged.

From this, also in this embodiment, the dimension of the reflective film 7 in the tracking direction of the objective lens 1 is from the midpoint between the center of the light receiving sensor 9 and the center of the light emitting diode 8 to the center of the light emitting diode 8 and the center of the light receiving center 10. To the midpoint between,
That is, by setting the distance between the light receiving sensors 9 and 10 to be approximately half, a good displacement detection sensitivity can be obtained.

As described above, the objective lens 1 is detected by detecting the change in the reflection area of the light emitting diode 8 on the reflection film 7 on the light receiving sensors 9 and 10 of the reflection film 7 provided on the surface of the relay plate 4. Differential output of differential amplifier 20 according to the amount of tracking direction movement
By obtaining 21, the position of the objective lens is detected.

〔The invention's effect〕

As described above, the present invention detects the position of the objective lens by detecting the area movement of the reflection film formed on the surface of the relay plate supporting the pair of focusing leaf springs holding the objective lens. By doing so, even if the objective lens moves in the focus direction, the change in the relay plate that can only be displaced in the direction perpendicular to the focus direction is detected, so the lens in the track direction is not affected by the focus direction. This has the effect of detecting only the movement of.

Further, since the number of light emitting diodes is one and the light emission is configured to be the differential detection of the two light receiving sensors, the differential output value and the detection change of the zero position point do not occur even when the light amount changes due to a change with time. There is an effect.

[Brief description of drawings]

1 (a) and 1 (b) are a plan view and a front view, respectively, showing an embodiment of the present invention, and FIGS. 2 (a) and 2 (b).
Is a diagram showing the principle of the present invention, and FIGS. 3 (a) and 3 (b) are a plan view and a front view showing a conventional objective lens driving device, respectively. 1 ... Objective lens, 2 ... Movable part, 3a, 3b ... Focusing leaf spring, 4 ... Relay plate, 5 ... Tracking leaf spring, 6 ... Fixed portion, 7 ... Reflective film, 8 ... … Light emitting diode, 9, 10… Light receiving sensor, 20… Differential amplifier, 21…
… Differential output, 30 …… Reflector.

Claims (1)

[Claims] 1. A movable part for holding an objective lens, a pair of focusing leaf springs which support the movable part and are perpendicular to the optical axis of the objective lens and parallel to each other, and an end of the pair of focusing leaf springs. A relay plate to be fixed, a tracking leaf spring that supports the relay plate and is attached to a fixed portion and is parallel to the optical axis of the objective lens, and the opposite side of the surface of the relay plate to which the tracking leaf spring is connected. A reflection film formed on a surface substantially perpendicular to the tracking leaf spring, a light source fixed so as to face the reflection film, and arranged on both sides of the light source in a direction orthogonal to the tracking leaf spring. The objective lens driving device includes: a pair of light receiving sensors that enter the reflected light of the reflecting film emitted from the light source; and a differential amplifier that outputs a difference between outputs of the pair of light receiving sensors. Apparatus.