JPH09106550A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of parts and to provide a small-sized device by using a light detection means for detecting a light quantity of light source light and detecting a position of a movable member in the tracking direction. SOLUTION: An optical pickup device is provided with a laser diode 103 as a light source, a collimate lens 104 making outgoing light from the diode 103 parallel rays of light, a first beam splitter 105, a photodetector 106, a second beam splitter 110, a triangle prism 114, an objective lens 102 and a light detection means 111 for detecting the outgoing light quantity of the laser diode 103. Further, supporters 113a, 113b are attached to a base 108 being a pickup main body of the device, and a bobbin 107 is linked to respective supporters 113a, 113b through four pieces of wires 112a-112d. Further, a motor (not shown in figure) is provided between the base 108 and the bobbin 107, and the wires 112a-112d are elastically deformed by the drive of the motor, and the bobbin 107 is made movable in the direction of the elastic deformation, and the bobbin 107 is made movable for the base 108. Since the objective lens 102 and the beam splitter 110 are attached to the bobbin 107, the lens 102 and the splitter 110 are moved in the tracking direction together with the bobbin 107.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention reproduces information recorded on an optical recording medium such as an optical disk by utilizing its reflected light, or records or erases information on the recording medium. The present invention relates to an optical pickup device.

[0002]

2. Description of the Related Art Conventionally, light is modulated by a signal from an external information source and irradiated on a recording medium such as an optical disk as a light spot to binaryly record information on the recording medium, or the recording medium. 2. Description of the Related Art There is known an optical pickup device that reproduces and erases information recorded on a recording medium using reflected light from a recording medium. In order to accurately record, reproduce, and erase this information, it is necessary to perform position control in the focusing direction so that the focal position of the objective lens is positioned on the surface of the recording medium. It is also necessary to perform position control in the tracking direction so that the light spot on the surface of the recording medium is accurately positioned with respect to the guide groove (groove) formed on the recording medium.

The position control of the objective lens in the tracking direction is performed by moving the entire optical pickup device when the amount of movement is large, and when the amount of movement is small, an actuator incorporated in the optical pickup device. Therefore, only the movable part that holds the objective lens is moved.

In order to accurately perform such position control in the tracking direction, an actuator equipped with a detector for detecting the movement of the objective lens in the tracking direction with respect to the housing of the optical pickup device is required.

FIG. 15 is a block diagram of an optical pickup device provided with the above actuator. Referring to FIG. 15, a lens holder 12 holding an objective lens 11 is movably attached to an optical pickup device body by an elastic wire 13. A magnet 14 and yokes 15 and 16 are provided in the main body of the optical pickup device. The magnet 14 and the yokes 15 and 16 form a magnetic circuit, and the coil 1 attached to the lens holder 12 is provided.
By passing a current through 7, the lens holder 12 can be moved in the X direction.

Further, the lens holder 12 has an opening 18
A light-shielding member 18 having a is provided, and a light source 19 and a two-divided photodetector 20 are provided at required intervals with the light-shielding member 18 interposed therebetween.

FIGS. 16A and 16B show a two-division photodetector 20.
It is a figure for demonstrating operation | movement of (20a, 20b). The light emitted from the light source 19 is applied to the opening 18 of the light blocking member 18.
The light passes through a and enters the two-division photodetector 20, but when the lens holder 12 moves in the X direction, the light blocking member 18 also moves in the X direction integrally with it, and the light spot 21 on the two-division photodetector 20. Also moves in the X direction according to the above movement amount. FIG.
6 (a) shows the light spot 21 in a stationary state in which the lens holder 12 is not moving, and FIG. 16 (b) shows the lens holder 1
2 shows a light spot 21 in a state where 2 moves in the X direction. As can be seen from FIGS. 16 (a) and 16 (b), the light spot 21
Is equally incident on each of the divided portions 20a and 20b of the two-divided photodetector 20, and the output from each of the divided portions 20a and 20b is the same, but when the light spot 21 moves, the divided portions of the two-divided photodetector 20 are divided. There is a difference in output between 20a and 20b.
By detecting this difference by the differential amplifier 22, the amount of movement of the objective lens 11 held in the lens holder 12 in the X direction can be detected.

However, in the above-mentioned optical pickup device, in order to detect the position of the objective lens, it is necessary to provide the dedicated light source 19, and there is a problem that the number of parts is increased. In order to avoid this problem, for example, in Japanese Patent Laid-Open No. 4-153923, a lens holder (lens drive unit) is provided with optical path branching means for partially changing the optical path of the light emitted from the laser diode, and the light is branched by the optical path branching means. The laser beam is made to enter the light detecting means.
In such a configuration, the light detecting means outputs a signal according to the amount of change in the irradiation position of the laser beam branched by the optical path branching means, whereby a dedicated light source for detecting the objective lens position is separately provided. Even without doing so, the position of the objective lens can be detected, and the number of parts can be reduced.

[0009]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 4
According to the technique disclosed in No. 153923, it is possible to reduce the number of parts regarding the position detection of the objective lens. However, among those skilled in the art, further reducing the number of parts of the entire optical pickup device,
It is desired that the optical pickup device has a small size and a simple structure.

An object of the present invention is to provide an optical pickup device having a smaller and simpler structure by further reducing the number of parts as compared with the prior art.

[0011]

In order to achieve the above object, the invention according to claim 1 condenses light from a light source onto a recording medium by an objective lens to record, reproduce or erase information. In the optical pickup device to perform, it is provided on the pickup body and the pickup body side,
Light detecting means for detecting the light amount of the light source light, and a movable member to which an objective lens is attached and which is movable in at least the tracking direction with respect to the pickup body, and the light detecting means for detecting the light amount of the light source light Is used to detect the position of the movable member in the tracking direction.

According to a second aspect of the invention, in the optical pickup device according to the first aspect, the movable member comprises:
Further, a light branching unit for branching a part of the light source light in a direction substantially perpendicular to the tracking direction is attached, and the light detecting unit is provided on the pickup body side so that the light branched by the light branching unit enters. The light detecting means changes the incident position of the branched light from the light branching means on the light detecting means when the light branching means moves along with the movement of the movable member. By detecting, the position of the movable member in the tracking direction is detected.

According to a third aspect of the present invention, in the optical pickup device according to the first aspect, a part of the light source light is further branched to the pickup body side in a direction substantially perpendicular to the tracking direction, and the light is emitted. An optical branching unit is provided for entering the detecting unit, and the movable member is
A light blocking member having an opening that allows only a part of the branched light branched from the light branching unit toward the light detecting unit to pass therethrough is provided, and the light detecting unit is associated with the movement of the movable member. When the light blocking member moves, the position of the movable member in the tracking direction is detected by detecting a change in the incident position of the light passing through the opening of the light blocking member on the light detecting means. There is.

According to a fourth aspect of the invention, in the optical pickup device according to the third aspect, the optical branching means is:
A part of the light source light from the light source is branched toward the light detecting means, and the reflected light from the recording medium is branched toward the signal detecting means for receiving the light and detecting the information signal. It is characterized by

Further, the invention according to claim 5 is based on claim 1,
The optical pickup device according to claim 2 or 3, wherein a two-divided light receiving element is used for the light detection means, and in the two-divided light receiving element, a dividing boundary line between two divided light receiving surfaces is perpendicular to the tracking direction. The output light amount of the light source light is detected by the sum signal of the output signals from the two divided light receiving surfaces, and the tracking of the movable member is performed by the difference signal of the output signals from the two divided light receiving surfaces. The feature is that the directional position is detected.

The invention according to claim 6 is the same as claim 1,
The optical pickup device according to claim 2 or 3, wherein a three-divided light receiving element is used for the light detecting means,
The three-divided light receiving element is arranged such that each divided boundary line of the three divided light receiving surfaces is perpendicular to the tracking direction. The output light signal of the light source light is detected by the output signal and the position of the movable member in the tracking direction is detected by the difference signal of the output signals from the divided light receiving surfaces at both ends.

According to a seventh aspect of the invention, in the optical pickup device according to the fifth or sixth aspect, a tracking direction of the movable member is calculated by a signal obtained by dividing the difference signal by the detection result of the emitted light amount of the light source light. It is characterized by detecting the position.

According to an eighth aspect of the invention, in the optical pickup device according to the third aspect, the movable member comprises:
A light-shielding portion that is coaxial with the optical axis of the objective lens and has an opening that shields a part of the light source light toward the objective lens is further provided. The dimension of the opening of the light-shielding portion in the tracking direction and the aperture of the light-shielding member. Is substantially equal to the dimension in the tracking direction.

According to a ninth aspect of the invention, in the optical pickup device according to the third aspect, the optical path of the light source light emitted from the light source and incident on the light branching means is inclined at a predetermined angle with respect to the tracking direction. It is characterized by that.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram (perspective view) showing a configuration example of an optical pickup device according to the present invention, and FIG. 2 is a diagram showing the optical pickup device of FIG.

Referring to FIGS. 1 and 2, this optical pickup device includes a laser diode 103 as a light source,
A collimator lens 104 that collimates the light emitted from the laser diode 103 (light source light), a first beam splitter (light splitting means) 105, and a signal detector (light receiving element) 10
6, a second beam splitter (light splitting means) 110,
It has a triangular prism 114, an objective lens 102, and light detection means 111 for detecting the amount of light emitted from the laser diode 103.

The base 108, which is the pickup body of the optical pickup device, has columns 113a and 11a.
3b is attached, and four wires 112a, 112b, 112c, 1 are attached to the columns 113a, 113b.
The bobbin 107 is connected via 12d. Also,
A motor (not shown) is provided between the base 108 and the bobbin 107, and the wires 112a, 112b, 112c, and 112d are elastically deformed by the driving of the motor, so that the bobbin 107 is elastic with respect to the base 108. It is movable in the direction of deformation. That is, the bobbin 107 is a movable member that is movable with respect to the base 108 that is the pickup body.

Here, the objective lens 10 is attached to the bobbin 107.
2 is attached, and a triangular prism 114 is attached to the base 108 below the objective lens 102. Further, in the base 108, the first beam splitter 105, the collimator lens 104, the laser diode 103, the signal detection unit 106, and the light detection unit 11 are provided on the tracking direction side of the triangular prism 114.
1 is attached. In addition, the second beam splitter 110 includes the triangular prism 114 and the beam splitter 10.
5 is arranged between the second beam splitter 11 and
0 is attached to the side surface of the bobbin 107.

That is, the objective lens 102 and the beam splitter 110 are attached to the bobbin 107, and the other parts are attached to the base 108 and do not move, whereas the objective lens 102 and the beam splitter 1 are attached.
10 is attached to the bobbin 107 and is movable. More specifically, the bobbin 107 is movable at least in a direction (tracking direction) substantially orthogonal to the optical axis Z of the objective lens 102 with respect to the base 108 serving as the pickup body, and therefore, the objective lens 102 and the beam The splitter 110 is adapted to move in the tracking direction when the bobbin 107 moves in the tracking direction.

In the optical pickup device having such a configuration, the light (light source light) emitted from the laser diode 103 is converted into parallel light by the collimator lens 104, transmitted through the beam splitter 105, and incident on the beam splitter 110. . A part of the light incident on the beam splitter 110 passes through the beam splitter 110 and is reflected by the triangular prism 114, so that the objective lens 1
It is condensed on the recording medium 101 by 02.

The light condensed on the recording medium 101 is reflected by the recording medium 101 to be converted into light containing information recorded on the recording medium 101, and the reflected light is converted by the objective lens 102. The light becomes parallel light, is reflected by the triangular prism 114, is incident on the beam splitter 105 via the beam splitter 110, is reflected by the beam splitter 105, is incident on the signal detection unit 106, and is an electrical information signal by the signal detection unit 106. Is converted to. That is, the information recorded on the recording medium 101 can be output from the signal detection unit 106 as an information signal (recording signal).

Part of the light (light source light) emitted from the laser diode 103 and traveling toward the triangular prism 114 is
As described above, the light is transmitted through the beam splitter 110 and is incident on the triangular prism 114, but some other light (light source light)
Is detected by the beam splitter 110.
The light is reflected to the side and enters the light detection means 111.

Here, when the light detecting means 111 is composed of, for example, a two-divided light receiving element having two divided light receiving surfaces 111a and 111b, the bobbin 107 of the light detecting means, that is, the two divided light receiving element 111 is tracked by the bobbin 107. In the neutral position in the direction (that is, the position where the displacement is “0”), the spot center of the light source light reflected by the beam splitter 110 is divided into two split light receiving surfaces 111a, 111a.
It is arranged so as to be located on the division boundary line of 11b. That is, when the bobbin 107 does not move in the tracking direction, the center of the light spot 119 on the two-divided light receiving element 111 is located on the division boundary line of the divided light receiving surfaces 111a and 111b, as shown in FIG. And, therefore,
The respective outputs from the two divided light receiving surfaces 111a and 111b are the same, and there is no difference.

On the other hand, when the bobbin 107 moves in parallel in the tracking direction, the beam splitter 110 also moves by the same amount, and the light spot 11 on the two-divided light receiving element 111 is moved.
The center of 9 also moves by the same amount, as shown in FIG.
Therefore, the two divided light receiving surfaces 11 of the two-divided light receiving element 111
There is a difference between the outputs from 1a and 111b. Since this output difference corresponds to the movement amount of the bobbin 107, the tracking direction position of the objective lens 102 movable integrally with the bobbin 107 can be detected by detecting this output difference.

Since the amount of light received by the two-divided light receiving element 111 and the amount of light emitted by the laser diode 103 are in a proportional relationship, the two divided light-receiving surfaces 111 of the two-divided light receiving element 111.
By controlling the laser diode 103 so that the sum of the respective outputs from a and 111b becomes a desired value, it is possible to correct the output fluctuation of the laser diode 103 due to the ambient temperature change.

As described above, in the optical pickup device of FIGS. 1 and 2, the light detecting means for detecting the light amount of the light source light is also used for detecting the tracking direction position of the objective lens attached to the movable member. Since it is possible to detect the position of the objective lens in the tracking direction, it is not necessary to separately provide a light receiving element, and the position of the objective lens can be detected by using a part of the light source light used for recording, reproducing and erasing the recording medium. Therefore, it is not necessary to separately provide a light source for detecting the position of the objective lens. As a result, the number of parts can be further reduced, and a smaller and simpler optical pickup can be provided as compared with the conventional one.

FIG. 4 is a diagram showing another structural example of the optical pickup device according to the present invention. In the optical pickup device of FIG. 1, two beam splitters 105 and 110 are provided and one beam splitter 110 is attached to the bobbin 107, but in the optical pickup device of FIG.
Functions of both beam splitters 105 and 110 (that is, part of the light from the light source is reflected and directed to the photodetector 111, and the signal light reflected from the recording medium 101 is also used.
One beam splitter 120 (having a function of reflecting (reflected light) and directing it to the signal detection unit 106) is attached to the base 108 at a distance from the bobbin 107, and on the side surface of the bobbin 107. Is provided with a light shielding plate 109 having an opening 109a of a predetermined size in the optical path of light traveling from the beam splitter 120 to the light detecting means 111.

Here, the dimension d of the opening 109a of the light shielding plate 109 in the tracking direction is set to be smaller than the dimension of the diameter of the light source light traveling from the beam splitter 120 to the light detecting means 111 in the tracking direction.
Numeral 09 is adapted to block light from both ends in the tracking direction of the light source light directed to the light detection means 111. In addition, the light detecting means 111 is configured to, for example, divide the two light receiving surfaces 111a,
In the case of being constituted by a two-division light receiving element having 111b, this light detecting means, that is, two-division light receiving element 111
(111a, 111b) indicates that when the bobbin 107 is at the neutral position in the tracking direction, the spot center on the two-divided light receiving element 111 of the light passing through the opening 109a is 2
Two divided light receiving surfaces 111a, 11 of the divided light receiving element 111
It is set so as to be located on the division boundary line of 1b.
That is, when the bobbin 107 does not move in the tracking direction, the light spot 1 on the two-divided photodetector 111 is
The center of 19 is, as shown in FIG.
Since they are located on the division boundary line of 1a and 111b, the respective outputs from the two division light receiving surfaces 111a and 111b are the same and there is no difference.

On the other hand, when the bobbin 107 moves in parallel in the tracking direction, the light shielding plate 109 also moves integrally with the bobbin 107, and the opening 109a is displaced in the tracking direction, so that the spot 119 of the light source light passing through the opening 109a. Also changes as shown in FIG. Therefore, similarly to the device of FIG. 1, a difference occurs between the outputs from the two divided light receiving surfaces 111a and 111b of the two-divided light receiving element 111, and the tracking direction position of the objective lens 102 is detected by detecting this output difference. Can be detected. Further, the amount of light emitted from the laser diode 103 can be detected by the sum of the outputs from the two divided light receiving surfaces 111a and 111b.

In the apparatus shown in FIG. 4, the position of the objective lens 102 is detected by changing the light-shielding position of the light-shielding plate 109.
Tracking width of light spot on 11 is always constant
It is (d).

By the way, in the optical pickup device of FIG. 1, FIG. 2 or FIG. 4, it is desirable that the bobbin 107 is moved in parallel in the tracking direction, but in reality, the wires 112a, 112b, which support the bobbin 107,
As shown in FIG. 6, due to the characteristics and errors of 112c and 112d, the characteristics and errors of the thrust force that drives the bobbin 107,
It may move with some rotation (ie, some tilt).

FIG. 7 is a diagram showing the positional relationship of each component when the bobbin 107 is tilted in the optical pickup device of FIGS. Referring to FIG. 7, when the bobbin 107 tilts by the angle θ around the objective lens 102, the reflection position of the beam splitter 110 shifts in the tracking direction by the angle α, and the reflecting surface of the beam splitter 110 tilts by the angle θ.

When the reflecting surface of the beam splitter 110 is tilted by θ, the reflection angle of the light source light from the laser diode 103 to the light detecting means 111 is tilted by 2θ in the beam splitter 110. Therefore, the light detection by the tilting of the bobbin 107 is performed. Deviation β of the light spot 119 on the means 111
₁ is represented by the following equation when the distance from the objective lens 102 to the light receiving surface of the light detection means 111 is l ₁ .

[0039]

[Formula 1] β ₁ = l ₁ tan 2θ−α

FIG. 8 is a diagram showing the positional relationship of the respective parts when the bobbin 107 is tilted in the optical pickup device of FIG. Referring to FIG. 8, when the bobbin 107 is tilted about the objective lens 102 by an angle θ, the deviation β ₂ of the light spot 119 on the light detecting means 111 is a direction orthogonal to the tracking direction and the optical axis direction of the objective lens 102. In the tracking direction, the objective lens 10 in the tracking direction is set to have a distance from the objective lens 102 to the light shielding plate 109 at l _2.
When the distance from 2 to the center of the opening 109a of the light shielding plate 109 is l ₃ , it is expressed by the following equation.

[0041]

[Equation 2] β ₂ = l ₂ sin θ−l ₃ (1-cos θ)

When the bobbin 107 is tilted by the angle θ, the light detecting means 11 in the optical pickup device shown in FIGS.
Deviation of the light spot on ₁ (β ₁ (= l ₁ tan 2θ−α),
Deviation of the light spot on the light detecting means 111 in the optical pickup device of FIG. 4 β ₂ (= l ₂ sin θ−l ₃ (1-cos
θ)), when the tilt angle θ is small, α ≈ 0, 1-cos θ ≈ 0, tan2θ> sin2θ, sin
Since 2θ> sinθ and l ₁ > l ₂ in the configuration of each device, the following equation holds.

[0043]

## EQU3 ## l ₁ tan 2θ−α> l ₂ sinθ−l ₃ (1-cos θ)

As can be seen from Equation 3, when the bobbin 107 is tilted by an angle θ, the apparatus of FIG. 4 shifts the light spot on the light detecting means 111 due to the tilt of the bobbin 107 more than the apparatus of FIGS. 1 and 2. The quantity is small and therefore the objective lens 10
The position detection error of 2 can be reduced.

In the optical pickup device of FIG. 1, the beam splitter 110 is attached to the bobbin 107, whereas in the optical pickup device of FIG. 4, the beam splitter 120 is attached to the base 108.
In place of the beam splitter, a light shielding plate 109 is attached to the.

Since the light shielding plate 109 is lighter than the beam splitter, the mass of the movable portion which is movable integrally with the bobbin 107 is smaller in the apparatus of FIG. 4 than in the apparatus of FIGS. In the device of No. 4, as compared with the device of FIG. 1, the driving force of the movable portion is small, and it is possible to reduce the size of the drive motor and save the drive power.

Further, in the optical pickup device of FIG. 4, since the beam splitter 120 is attached to the base 108, there is no positional deviation from the signal detection unit 106 also attached to the base 108, and therefore signal detection is performed. In the unit 106, the signal light (reflected light) can be detected with higher accuracy.

Furthermore, in the optical pickup device of FIG.
Since one beam splitter 120 has a function of splitting the light from the light source toward the light detecting means 111 and also having a function of splitting the light reflected from the recording medium 101 toward the signal detecting unit 106, FIG. As compared with the optical pickup device of FIG. 2, the number of beam splitters can be reduced and the number of parts can be reduced.

In the above description, the light detecting means 111
Although the two-divided light receiving element is used for the light detecting means 111,
As the light receiving element, any light receiving element other than the two-divided light receiving element can be used. 9 (a) and 9 (b) are diagrams showing the light spot positions when the photodetector 111 uses a three-divided light receiving element. 9 (a) and 9 (b) are shown in FIG.
It corresponds to (a) and (b).

For example, in the optical pickup device shown in FIG. 4, when a two-divided light receiving element as shown in FIGS. 5A and 5B is used as the light detecting means 111, the beam splitter 1
The intensity of light traveling from 20 to the light shielding plate 109 increases from the outer periphery toward the center, so that the light shielding plate 109
The intensity of the light passing through the opening 109a varies depending on the light-shielding position, and when the output variation of the laser diode 103 is detected by the signal corresponding to the total light received by the two-division light-receiving element 111, the amount of light received due to the light-shielding position change. Fluctuations occur,
This becomes a detection error.

On the other hand, the photodetector means 111 shown in FIG.
When using a three-divided light receiving element as shown in (a) and (b),
Three divided light receiving surfaces 111a, 111 of the three-divided light receiving element
By detecting the amount of light emitted from the laser diode 103 from the output from the central divided light receiving surface 111b of b and 111c, it is possible to reduce the influence of the position variation of the light shielding plate 109. That is, as shown in FIGS. 9A and 9B, the central divided light receiving surface 111 of the three-divided light receiving element 111.
b receives the central portion of the light traveling to the light shielding plate 109, and always receives the light of the same portion even if the position of the light shielding plate 109 changes, so that even if the position of the light shielding plate 109 changes, 3
It is possible to improve the detection accuracy of the emitted light amount of the laser diode 103, that is, the light amount of the light source light, without affecting the light receiving amount of the central light receiving surface 111b of the divided light receiving element 111.

Further, since the output difference between the divided light receiving surfaces 111a and 111c at both ends of the three-divided light receiving element 111 changes according to the change of the light shielding position, the divided light receiving surfaces 111a and 111 at both ends are changed.
By detecting the output difference of 1c, the objective lens 102
The position in the tracking direction can be detected.

Further, in the optical pickup device of FIG. 1, FIG. 2 or FIG. 4, the bobbin 107 can block light between the triangular prism 114 and the objective lens 102 as shown in FIG. 10, for example. The structure may be such that it does not exist, or, as shown in FIG. 11, it has a structure having a light blocking portion 140 for blocking a part of light between the objective lens 102 and the triangular prism 114. May be. Here, the light shielding portion 140 has an opening 140a, and when the light emitted from the laser diode 103 is reflected by the triangular prism 114 and travels toward the objective lens 102, this light is shown in FIG. So that the opening 140
Part of the light is blocked when passing through a, and the objective lens 102
Incident on.

In this case, when the bobbin 107 moves in the tracking direction and the light blocking plate 109 moves, and the light blocking position changes, as shown in FIG.
The amount of light passing through 40a also fluctuates, as does the light passing through the opening 109a of the light blocking plate 109. Thus, in the optical pickup device of FIG. 4, when the dimension of the opening 140a of the bobbin 107 in the tracking direction and the dimension of the opening 109a of the light shielding plate 109 in the tracking direction are set to be substantially equal, the bobbin 107 moves in the tracking direction. Since the amount of light received by the light detecting means 111 by the opening 109a of the light blocking plate 109 and the amount of light entering the objective lens 102 fluctuate at the same rate, the light detecting means 111 moves to the objective lens 102 by moving the bobbin 107. It is possible to detect the variation of the emitted light amount of the laser diode 103 which is proportional to the variation of the incident light amount of the light source light (the received light amount of the recording medium 101). Therefore, based on the detection result of the photodetector means 111, The amount can be detected and controlled more accurately.

Further, in the optical pickup device of FIG. 4, when a two-divided light receiving element is used as the light detecting means 111,
The position of the objective lens 102 is detected by the difference signal between the outputs of the two divided light receiving surfaces 111a and 111b.
The output of the laser diode 103 is modulated according to the signal to be recorded when the information is recorded on the recording medium 101, and the output at the time of reproducing and the output at the time of erasing are also modulated differently. When the output of 103 changes, the difference signal of the two-divided light receiving element 111 also changes. Therefore, it is necessary to change the reference amount of the difference signal of the two-division light receiving element 111 according to the output modulation of the laser diode 103.

When a two-divided light receiving element is used as the light detecting means 111, the amount of light emitted from the laser diode 103 is detected by the sum signal of the outputs of the two divided light receiving surfaces 111a and 111b, and the laser is detected based on this detection result. Although the amount of light emitted from the diode 103 is controlled, the amount of light emitted from the laser diode 103 varies due to a control error, and this amount of variation is reflected in the position detection of the objective lens 102 and causes an error.

In order to avoid such a problem, the two divided light receiving surfaces 111a and 111 of the two-divided light receiving element 111 are used.
It is preferable to detect the position of the objective lens 102 by a value obtained by dividing the difference signal of each output of b by the sum signal of each output. That is, the value obtained by dividing the difference signal of each output by the sum signal of each output does not change even if the output of the laser diode 103 is modulated, and the output control error is not reflected. Therefore, based on this value, the objective lens The position of 102 can be detected easily and with high accuracy.

Further, in the optical pickup device of FIG. 4, when a three-divided light receiving element is used for the light detection means 111, of the three divided light receiving surfaces 111a, 111b, 111c, the divided light receiving surfaces 111a, 111c at both ends are used. The position of the objective lens 102 is detected by the difference signal of each output, and the emitted light quantity of the laser diode 103 is detected by the output signal of the central divided light receiving surface 111b. In this case as well, the light detecting means 111 is divided into two. Similar to the case of using the light receiving element, the difference signal between the outputs of the divided light receiving surfaces 111a and 111c is divided by the output signal of the central divided light receiving surface 111b,
By detecting the position of the objective lens 102 using the divided value, the position of the objective lens 102 can be detected easily and with high accuracy.

FIG. 12 is a diagram showing a modified configuration example of the optical pickup device of FIG. In the optical pickup device of FIG. 4, as shown in more detail in FIG.
Light incident on 0 is parallel to the tracking direction, is reflected by the beam splitter 120, changes its direction by 90 °, and travels toward the light detection means 111. In the optical pickup device of FIG. 12, the light is shown in more detail in FIG. As described above, the light incident on the beam splitter 120 from the laser diode 103 is inclined by an angle δ with respect to the tracking direction, changes its direction at the beam splitter 120 at an angle of 90 ° + δ, and travels toward the light detecting means 111. Has become. In this way, the light emitted from the laser diode 103 and directed to the bobbin 107 is tilted with respect to the tracking direction, so that the objective lens 1 in the direction orthogonal to the tracking direction and the optical axis direction of the objective lens 102 is obtained.
02 and the light shielding plate 109 (l _{2 in} FIG. 8) can be reduced.

Further, the shift amount of the light spot on the light detecting means 111 due to the inclination of the bobbin 107 is as described above.
Since l ₂ sin θ−l ₃ (1-cos θ) is obtained and l ₂ can be reduced as described above, the shift amount of the light spot can also be reduced.

Further, the cross-sectional shape of the light emitted from the laser diode 103 is elliptical, and in the apparatus of FIG. 4, as shown in FIG. 13, the elliptical light toward the objective lens 102 is tracked in the minor axis direction. If the direction coincides with the direction, the minor axis direction of the light toward the light detection unit 111 is inclined at an angle of 90 ° with respect to the tracking direction. In this case, the dimension of the opening 140a of the bobbin 107 in the tracking direction and the dimension of the opening 109a of the light shielding plate 109 in the tracking direction are equalized, and the fluctuation rates of the amounts of light passing through the openings 140a and 109a due to the movement of the bobbin 107 in the tracking direction are equalized. Even with the intention of reducing various errors, the bobbin 10
7 toward the opening 140a and the opening 10 of the light blocking plate 109
An error occurs because the direction of the minor axis of the ellipse deviates from the light directed to 9a by 90 °.

On the other hand, in the device of FIG. 12, as shown in FIG. 14, the minor axis direction of the elliptical light directed to the light detecting means 111 is at an angle of (90 ° -δ) with respect to the tracking direction. That is, it is inclined at an angle smaller than 90 °. As described above, in the apparatus of FIG. 12, the deviation in the minor axis direction of the ellipse between the light traveling toward the opening 140a of the bobbin 107 and the light traveling toward the opening 109a of the light shielding plate 109 is smaller than 90 ° (90 °.
Since the angle can be −δ), the error can be reduced.

[0063]

As described above, according to the first aspect of the invention, the light detecting means for detecting the light amount of the light source light is used for detecting the position in the tracking direction of the objective lens attached to the movable member. Since it can also be used for the above, it is not necessary to separately provide a light receiving element for detecting the tracking direction position of the objective lens.
In the invention described above, the position of the objective lens can be detected by utilizing a part of the light from the light source used for recording, reproduction and erasing of the recording medium. Therefore, it is necessary to provide a separate light source for detecting the position of the objective lens. Also disappears. As a result, the number of parts can be further reduced, and a smaller and simpler optical pickup can be provided as compared with the conventional one.

In particular, according to the third aspect of the invention, the position of the objective lens can be detected by changing the light shielding position of the light shielding member attached to the movable member by the movement of the movable member. Since the light branching means for branching a part of the light from the light source to the light detecting means is provided not on the movable member but on the pickup body side, the light branching means is provided on the movable member side, as compared with the case of claim 2. The detection error when the movable member is tilted can be reduced, and the light-shielding member is lighter in weight than the light branching means, so that the mass of the movable member can be reduced, and the drive motor can be downsized and the drive power can be reduced. It can also be planned.

According to the invention described in claim 4, the light branching means branches a part of the light source light from the light source toward the light detecting means and receives the reflected light from the recording medium. Since it has a function of branching toward the signal detecting means for detecting the information signal, the number of parts can be further reduced.

According to the fifth and sixth aspects of the present invention, the light detecting means includes a two-divided light receiving element, and the two-divided light receiving element has a division boundary line between two divided light receiving surfaces. It is placed so that it is perpendicular to the tracking direction.
The output light amount of the light source light is detected by the sum signal of the output signals from the two divided light receiving surfaces, and the tracking direction position of the movable member is detected by the difference signal of the output signals from the two divided light receiving surfaces. Also, a three-divided light receiving element can be used as the light detecting means. When using the three-divided light receiving element, each of the three divided light receiving surfaces has a dividing boundary line perpendicular to the tracking direction. Of the output signals from the three divided light receiving surfaces,
The amount of light emitted from the light source is detected by the output signal from the split light receiving surface in the center, and the tracking direction position of the movable member is detected by the difference signal between the output signals from the split light receiving surfaces at both ends. It is possible to improve the detection accuracy by using an existing light receiving element having a different structure.

In particular, according to the sixth aspect of the invention, since a constant part of the central portion of the light source light is monitored to detect the light amount of the light source light, a part of the light source light traveling to the light detecting means is Even if the light shielding position of the light shielding member attached to the movable member changes due to the movement of the movable member, it does not affect the detection of the light amount of the light source light, and the detection accuracy can be improved.

According to the seventh aspect of the invention, the position of the movable member in the tracking direction is detected by a signal obtained by dividing the difference signal by the detection result of the emitted light amount of the light source light. Since there is no influence of output modulation or fluctuation of the light source, the position detection accuracy can be improved.

According to the invention described in claim 8, the movable member is provided with a light-shielding portion which is coaxial with the optical axis of the objective lens and has an opening for shielding a part of the light source light toward the objective lens. Further, since the dimension of the opening of the light blocking portion in the tracking direction and the dimension of the opening of the light blocking member in the tracking direction are substantially equal to each other, the variation rate of the amount of light passing through each opening due to the movement of the movable member is reduced. The values are substantially equal to each other, whereby the detection accuracy of the amount of light received by the recording medium can be improved.

According to the ninth aspect of the invention, since the optical path of the light source light emitted from the light source and incident on the light branching means is inclined at a predetermined angle with respect to the tracking direction, the light shielding provided on the movable member. The position of the portion can be brought closer to the objective lens, and the error in detecting the objective lens position when the movable member is tilted can be reduced. Further, since the difference between the rate of change in intensity of the light toward the objective lens in the tracking direction and the rate of change in intensity of the light toward the light detection means in the tracking direction becomes small, the light amount detection accuracy when implementing claim 7 is further improved. Can be made.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an optical pickup device according to the present invention.

FIG. 2 is a diagram showing a configuration example of an optical pickup device according to the present invention.

FIG. 3 is a diagram for explaining a light spot position on a light detection unit.

FIG. 4 is a diagram showing another configuration example of the optical pickup device according to the present invention.

FIG. 5 is a diagram for explaining a light spot position on a light detection unit.

FIG. 6 is a diagram for explaining the inclination of the bobbin.

FIG. 7 is a diagram showing a positional relationship of each component when the bobbin is tilted in the optical pickup device of FIGS. 1 and 2.

FIG. 8 is a diagram showing a positional relationship of each component when the bobbin is tilted in the optical pickup device of FIG.

FIG. 9 is a diagram for explaining a light spot position on a light detection unit.

FIG. 10 is a diagram showing a configuration example of a bobbin.

FIG. 11 is a diagram showing another configuration example of the bobbin.

FIG. 12 is a diagram showing another configuration example of the optical pickup device according to the present invention.

13 is a diagram for explaining light source light in the optical pickup device of FIG.

FIG. 14 is a diagram for explaining light source light in the optical pickup device of FIG.

FIG. 15 is a diagram showing a configuration example of a conventional optical pickup device.

FIG. 16 is a diagram for explaining the operation of the two-split photodetector.

[Explanation of symbols]

101 recording medium 102 objective lens 103 light source (laser diode) 104 collimating lens 105 first beam splitter
(Optical splitter) 106 Signal detector 107 Bobbin (movable member) 108 Base (pickup body) 110 Second beam splitter
(Light splitting means) 111 Light detecting means 114 Triangular prism 109 Light blocking plate 109a Opening of light blocking plate 120 Beam splitter (light splitting means) 140 Light blocking portion 140a Opening of light blocking portion

Claims (9)

[Claims] 1. An optical pickup device for collecting, reproducing, or erasing information by condensing light from a light source onto a recording medium by an objective lens. The optical pickup device is provided on a pickup body and a pickup body side. A light detecting unit for detecting the light amount of light and a light detecting unit for attaching the objective lens and having a movable member movable at least in the tracking direction with respect to the pickup body are provided. An optical pickup device, wherein the position of the movable member in the tracking direction is detected by using the optical pickup device. 2. The optical pickup device according to claim 1, wherein the movable member is further provided with an optical branching unit for branching a part of the light source light in a direction substantially perpendicular to the tracking direction, and the light detecting unit. Is provided on the pickup main body side so that the light branched by the light branching unit is incident, and the light detection unit, when the light branching unit moves as the movable member moves, An optical pickup device, characterized in that the position of the movable member in the tracking direction is detected by detecting a change in the incident position of the branched light from the light branching unit on the light detecting unit. 3. The optical pickup device according to claim 1, further comprising: a light for branching a part of the light source light in a direction substantially perpendicular to the tracking direction on the pickup body side and making the light incident on the light detecting means. A branching unit is provided, and the movable member is provided with a light blocking member having an opening that allows only a part of the branched light branched from the light branching unit toward the light detecting unit to pass therethrough. The light detecting means detects a change in an incident position on the light detecting means of light passing through an opening of the light blocking member when the light blocking member moves along with the movement of the movable member. An optical pickup device, wherein the position of the movable member in the tracking direction is detected by. 4. The optical pickup device according to claim 3, wherein the light branching unit branches a part of the light source light from the light source toward the light detecting unit, and reflects the reflected light from the recording medium. An optical pickup device, characterized in that the optical pickup device is adapted to branch in the direction of a signal detecting means for receiving light and detecting an information signal. 5. The optical pickup device according to claim 1, 2 or 3, wherein:
A two-divided light receiving element is used, and the two-divided light receiving element is arranged such that the division boundary line of the two divided light receiving surfaces is perpendicular to the tracking direction, and the sum of the output signals from the two divided light receiving surfaces is used. The amount of light emitted from the light source is detected by the signal, and 2
An optical pickup device characterized in that a position of a movable member in a tracking direction is detected by a difference signal of output signals from one divided light receiving surface. 6. The optical pickup device according to claim 1, claim 2, or claim 3, wherein a three-divided light receiving element is used for the light detecting means, and the three-divided light receiving element has three divided light receiving surfaces. The divided dividing lines of are arranged so as to be perpendicular to the tracking direction, and the output light amount of the light source light is detected by the output signal from the central divided light receiving surface among the output signals from the three divided light receiving surfaces. An optical pickup device is characterized in that the position of the movable member in the tracking direction is detected by a difference signal of output signals from the divided light receiving surfaces at both ends. 7. The optical pickup device according to claim 5, wherein the position of the movable member in the tracking direction is detected by a signal obtained by dividing the difference signal by a detection result of the amount of emitted light of the light source light. Optical pickup device. 8. The optical pickup device according to claim 3, wherein the movable member has a light-shielding portion that is coaxial with the optical axis of the objective lens and has an opening that shields a part of the light source light toward the objective lens. The optical pickup device is further provided, wherein the dimension of the opening of the light shielding portion in the tracking direction is substantially equal to the dimension of the opening of the light shielding member in the tracking direction. 9. The optical pickup device according to claim 3, wherein the optical path of the light source light emitted from the light source and incident on the optical branching means is inclined at a predetermined angle with respect to the tracking direction. .