JP2601035B2 - Optical pickup device position adjustment device for optical pickup - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup (optical PU) for recording or reproducing information on a CD (compact disk) or the like, and in particular, adjusts the position of the light receiving element with respect to the incident optical axis. The present invention relates to an improvement in a light receiving element position adjusting device.

[0002]

2. Description of the Related Art For an optical pickup having a light receiving element, it is necessary to adjust the position at the time of production so that the light receiving element is located at the center of the incident optical axis. Conventionally, such position adjustment is performed by moving the objective lens 12 up and down with respect to the optical disk 10 as shown by an arrow FA, as shown in FIG.

Normally, the objective lens 12 is at a position shown by a solid line lower than a focus position with the optical disk 10 due to a natural drop due to its own weight. Therefore, the light beam from the optical disk 10 does not form a good image on the light receiving element, and no signal from the light receiving element required for position adjustment can be obtained. Thus, as shown by the arrow FA, the objective lens 12 is driven to cross the depth of focus range indicated by WA in FIG. Then, when the objective lens 12 crosses the focusing depth range WA (refer to the broken line position in the figure), the light beam is focused on the light receiving element, and a signal for adjustment can be obtained.

FIG. 7 shows this state. As shown in the graph GA of FIG.
It is driven in a range of WB around the focus depth range WA. The drive frequency is, for example, several Hz. When the objective lens 12 passes through the focusing depth range WA, for example, a signal as shown by a graph GB in FIG.

[0005] The light receiving element is configured, for example, as shown in FIG. In the figure, a four-division type light receiving element 14
Is provided with four divided light receiving surfaces A, B, C, and D divided by four.
The positions of B, C, and D can be adjusted in the X and Y plane directions. In the following description, the four divided light receiving surfaces A, B,
C and D are called elements A, B, C and D. At this time, the elements A and B are connected to the non-inverting input side of the operational amplifier 16 via the resistors R10 and R12, respectively.
Each is connected to the inverting input side of the operational amplifier 16 via the resistors R14 and R16. The elements B and C are connected to the non-inverting input side of the operational amplifier 18 via the resistors R18 and R20, respectively, and the elements A and D are connected to the resistors R22 and R22, respectively.
It is connected to the inverting input side of the operational amplifier 18 via R24.

[0006] Of the above components, the resistors R10, R12,
An X position signal operation circuit is constituted by R14, R16 and the operational amplifier 16, and resistors R18, R20, R2
2, R24 and the operational amplifier 18 constitute a Y position signal computing circuit. The operational amplifier 16 outputs an X position signal represented by X = (A + B)-(C + D), and the operational amplifier 18 outputs a Y position signal represented by Y = (B + C)-(A + D). It has become.

Next, the operation of adjusting the position of the light receiving element 14 will be described. As described above, consider the moment when the objective lens 12 just passes through the focus depth range WA. At this time, if the light receiving element 14 is displaced in the plus direction of X, more light beams will be incident on the elements A and B than on the elements C and D. Therefore, the signal level on the non-inverting input side of the operational amplifier 16 is higher than the other signal level, and the operational amplifier 16 outputs a positive position signal. When the light receiving element 14 is displaced in the negative X direction, a negative signal is output from the operational amplifier 16.

Therefore, when the objective lens shown in FIG. 6 is driven while the light receiving element 14 is moved in the X direction, a graph shown in FIG. 9 is obtained. As is clear from this graph, when the light beam enters the center of the light receiving element 14,
The level of the output signal of the operational amplifier 16 is drastically reduced. Therefore, if the position of the light receiving element 14 is adjusted at the decreasing point in that case, the light beam will be incident on the center of the light receiving element 14 well. The same applies to the Y direction.

More specifically, an X position signal and a Y position signal output from the operational amplifiers 16 and 18 are input to an X axis and a Y axis of an oscilloscope (not shown), respectively, and the waveform of the light receiving element 14 is measured by observing a waveform. Position adjustment is performed by moving an adjustment mechanism (XY stage). That is, as shown in FIG. 9, an X or Y position signal generated intermittently is observed with an oscilloscope, a direction to be adjusted is determined from the polarities of the XY signals, and light is received at a waveform minimum level position at the center position. The position of the element 14 is adjusted.

[0010]

However, in the prior art described above, the signal is output only in the in-focus depth range WA, so that the signal becomes a steep pulse. In addition, the frequency of occurrence is 12 dB / after the frequency f ₀ (= around 20 Hz).
The length becomes long due to the lens drive characteristic attenuated by oct. Therefore, in order to improve the signal detection accuracy especially near the center position, an extremely complicated and highly accurate circuit device is required.

Therefore, after the position adjustment by the above-described method, a focus servo is applied to adjust the light receiving element 14 to a position where the DC component of the X (Y) signal becomes 0 V, so that the final position setting is performed. Done. That is, the position adjustment of the light receiving element 14 is performed by provisional adjustment based on an intermittent signal obtained by driving the objective lens 12 and final adjustment with a focus servo applied.

However, even such a method has the following disadvantages. (1) Since the objective lens 12 is driven to obtain a focus position, driving at a high frequency cannot be performed, and the waveform of an oscilloscope is difficult to observe. (2) The driving of the objective lens 12 in the direction of the arrow FA is several times as large as the focusing depth range WA because of the necessity of satisfactorily passing through the focusing depth range WA even if the bobbin drive sensitivity varies and the assembly position varies. The range is the drive range W of the objective lens 14.
B is required. For this reason, a considerable load is required for driving the objective lens 12.

(3) As shown in FIG. 9, the signal level when the light receiving element is greatly displaced becomes extremely small. For this reason, the direction to be adjusted cannot be known from the signal waveform on the oscilloscope until the position is adjusted to some extent near the center. (4) Two types of adjustment work, a temporary adjustment and a main adjustment, are required, which makes the adjustment device complicated and requires a long adjustment time. (5) The temporary adjustment signal is a signal having a high crest factor as described above, and is not suitable for high-speed automatic adjustment.

The present invention has been developed in view of this point, and it is an object of the present invention to provide a light receiving element position adjusting device of an optical pickup suitable for automation which can easily and accurately adjust the position of the light receiving element in a short time. With that purpose.

[0015]

SUMMARY OF THE INVENTION The present invention relates to an optical pickup.
Irradiates the optical beam output from the backup onto the optical disc
Then, the optical beam reflected by the optical disk is received.
A four-division type light receiving element provided in the optical pickup;
The light beam is divided into four divided light receiving surfaces of the light receiving element.
To receive light at the approximate center where the four light receiving surfaces intersect in a plane.
The position of the four divided light receiving surface is adjusted in the XY plane direction so that
A light receiving element position adjusting device for an optical pickup,
Normal rotation while forcibly supporting the optical disc
Rotating the optical disc at a higher speed than the
The light beam within a range including the focusing position of the optical pickup;
Displacement means for displacing in the optical axis direction of the
As a result, the optical disk is displaced in the optical axis direction of the optical beam.
Output from the quadrant light receiving surface of the light receiving element.
The light receiving surface of the light receiving element based on the output signal
Position information in the XY plane direction with respect to the approximate center of
Calculating means, and the displacement position information output from the calculating means.
The light beam is divided into four parts by the light receiving element based on the information.
The four-divided light receiving surface is XY so that light is received substantially at the center of the light surface.
An XY direction drive mechanism for performing position adjustment in a plane direction is provided.

[0016]

According to the present invention, light reflected from an optical disk
The beam is divided into four divided light receiving surfaces of the four divided light receiving surfaces of the light receiving element.
Are divided into four parts so that the light
When adjusting the position of the optical surface in the XY plane direction,
Faster than normal rotation while forcibly tilting and supporting
Rotate the optical disk and focus on the optical pickup
Within the range including the position, in the direction of the optical axis of the optical beam.
Output signals from the four-divided light receiving surface of the light receiving element
Changes depending on the position of the disk or optical disk equivalent
Therefore, from the change, the approximate center of the four-divided light receiving surface of the light receiving element
Position information in the XY plane direction can be obtained.
The light beam is divided into four light beams based on this deviation position information.
The device is divided into four parts so that light is received at approximately the center of the light receiving surface.
The position of the light receiving surface is adjusted in the XY plane direction.

[0017]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing an apparatus for adjusting the position of a light receiving element of an optical pickup according to the present invention. FIG. 2 shows an arrangement state of the optical disc 20 in the present embodiment. In the present embodiment, the optical disc 20 is arranged with a predetermined inclination given in advance. FIG. 2B shows the entire structure.
FIG. In these figures, the optical disk 20
Are arranged with an inclination of φ from the state of no inclination indicated by line LA in the figure. That is, the right half 20A is inclined downward from the normal position, and the left half 20B is inclined upward from the normal position.

This inclination can be achieved by inserting an inclination piece 20D between the turntable 20C and the optical disk 20 which are arranged substantially horizontally, as shown in FIG. Is formed. The optical disc 20 is
The posture is held by the disc table 20E holding the turntable 20C. Due to such an inclination of the optical disk 20, the focusing distance between the pickup and the optical disk 20 changes within the range of WC. The optical disc 20 is adjusted so that the in-focus depth range WA is included in the fluctuation range WC. That is, in the present embodiment, instead of moving the bobbin of the objective lens 12 up and down, the optical disk 20 is moved up and down.

The optical pickup 22 has a structure shown in FIG.
The light receiving element 14 shown in FIG.
The light beam reflected from the disk 20 is used as the light receiving element 14 element.
(Four-division light-receiving surface) Each of the elements A, B, C, and D
B, C, and D receive light at the approximate center where they intersect in a plane.
The elements of the light receiving element 14 (quadrant light receiving surface) A, B, C,
The position of D is adjusted in the XY plane direction. Next, an RF level detection circuit 24, an X position signal calculation circuit 26, and a Y position signal calculation are provided on the detection signal output side of the optical pickup 22 for detecting the light beam from the optical disc 20 inclined and arranged as described above. The inputs of the circuit 28 are each connected. Among these, the output side of the RF level detection circuit 24 is directly connected to the input side of the control circuit 30.
The output sides of the X and Y position signal calculation circuits 26 and 28 are connected to the control circuit 30 via the position detection circuits 32 and 34, respectively.
Is connected to the input side.

Next, the input side of the focus drive circuit 36 is connected to the focus signal output side of the control circuit 30, and the output side of the focus drive circuit 36 is connected to the focus drive signal input side of the optical pickup 22. Have been. Also, the output side of the position control signal for X and Y of the control circuit 30 is connected to the input side of the X and Y position control amplifiers 38 and 40. These position control amplifiers 38, 40
Is connected to a drive mechanism 44 for moving the light receiving element 14 in the X and Y directions. The optical disk 2
The rotation drive of 0 is performed by the spindle motor 42.

Of the above components, the X and Y position signal operation circuits 26 and 28 are composed of an input resistor and an operational amplifier as shown in FIG. Position detection circuit 32,
Numeral 34 is for detecting the position of the light receiving element in the X and Y directions from the state of the input position signal. The control circuit 30 grasps the polarity and level of the position detection signals input from the position detection circuits 32 and 34 by performing A / D conversion and the like,
It has a function of recognizing a position direction to be adjusted on the basis thereof and supplying a corresponding drive signal to the X and Y position control amplifiers 38 and 40. The X and Y position control amplifiers 3
8, 40 are driver amplifiers for driving the driving mechanism 44.

Next, the focus drive circuit 36 drives the objective lens up to the approximate focus position in the optical pickup 22 based on an instruction from the control circuit 30. The RF level detection circuit 24 is for detecting the RF output signal level of the optical pickup 22, and the control circuit 30 determines whether or not the optical pickup 22 is at the in-focus position based on the detected value. It has become. Further, the drive mechanism 44 is provided with the optical pickup 2
The two light receiving elements are moved in the X and Y directions, respectively, so that the center of the light receiving element is positioned at the center of the reflected light beam from the optical disk 20.

Next, the operation of the embodiment configured as described above will be described with reference to FIGS. The optical disk 20 is rotated at a desired rotation speed by a spindle motor 42. This rotation is performed with the disc tilted. By increasing the rotation speed, the period of signal detection can be shortened, and the detection accuracy can be increased.

(1) Rough Position Control of Focusing Position As shown in FIG. 6, the objective lens 12 of the optical pickup 22 is located at a position deviating from the normal focusing depth range WA. For this reason, it is necessary to drive the objective lens 12 so that the focus depth range WA falls within the focus variation range WC due to the disc tilt. In the present embodiment, the objective lens 12 is gradually driven by the focus drive circuit 36 based on a command from the control circuit 30. The output RF signal of the optical pickup 20 at this time is detected by the RF level detection circuit 24 and supplied to the control circuit 30. And R
When the generation of the F signal is confirmed in the control circuit 30, it is determined that the objective lens 12 is at the approximate focus position.

(2) Position Adjustment of Light Receiving Element Next, when the tilted optical disk 20 is rotated at a speed higher than the normal rotation speed , the disk surface is moved to a predetermined focusing depth range WA as shown in FIG. Crosses periodically. As a result, the RF signal is obtained from the light receiving element 14 of the optical pickup 22 as described above, and further, from the position signal calculation circuits 26 and 28, for example, an X or Y position signal as shown in FIG. Can be obtained. FIG. 5 shows a case where the light receiving element 14 is displaced to the + side of X or Y.

FIGS. 5A and 5B show examples of measurement of the X position signal in the present embodiment and the conventional example in the state where the same light receiving element is displaced. As is clear from the comparison between the present embodiment in FIG. 7A and the conventional example in FIG. 7B, the present embodiment has a shorter detection cycle and a higher detection level. For this reason, it is possible to obtain the position accuracy of the light receiving element 14 with sufficient accuracy. The same applies to the Y position signal.

The X and Y position signal operation circuits 26 and 2
8 are supplied to the position detection circuits 32 and 34, respectively. In the position detection circuits 32 and 34, processing such as integration or peak hold is performed on each input signal, whereby the position detection signals shown in FIG. 4 can be obtained. This position detection signal indicates that the light receiving element 14 is
This signal crosses zero when the light beam reaches the center position from 0.

Since the level of this position detection signal is fluctuated by the laser emission power of the light source, it is impossible to obtain an absolute amount of position shift of the light receiving element 14. However, the center position with respect to the light beam is unchanged without being influenced by the light beam, and the zero-cross point corresponds to the position as described above. Such a position detection signal is input to the control circuit 30. The control circuit 30 outputs drive signals to the X and Y position control amplifiers 38 and 40 based on the input position detection signal. Then, based on these drive signals, the position of the light receiving element 14 in the drive mechanism 44 is adjusted.

More specifically, up to the central area WD including the beam center PC, the light-receiving element 1 according to the polarity of the position detection signal.
4 is performed. Then, in the central region WD, the amount of change of the position detection signal becomes steep, and the minute drive of the drive mechanism 44 is performed based on the change polarity, and the change result of the position detection signal at this time is determined. The direction to be adjusted and the amount of adjustment are recognized. The control circuit 30
The driving mechanism 44 is driven again based on the result, and the final position adjustment of the light receiving element 14 is performed.

As described above, according to the present embodiment, the optical disc is inclined and rotated instead of the objective lens. Then, conditions are set such that the fluctuation range WC at this time is near the in-focus depth range WA. For this reason, the position signals of X and Y are not pulsed as steeply as in the past, but are gentle. Also, by increasing the rotation speed of the optical disk, the period of signal detection can be shortened. Accordingly, it is possible to obtain a very good level of a large position signal, and the following effects can be obtained.

(1) Since there is no need to perform complicated signal processing, the circuit configuration is simplified. (2) The position detection accuracy of the light receiving element is dramatically improved. For this reason, the main adjustment as in the related art is not required, and the operation can be completed in one adjustment process. (3) The period of the position signal from the light receiving element is
The setting can be easily made only by changing the disk rotation speed by rotating the disk at a higher speed than the normal rotation . Therefore, the period can be shortened, the measurement time constant can be shortened, and high-speed measurement and high-speed automatic adjustment can be performed. (4) Compared with the conventional objective lens bobbin driving method, the focus fluctuation range can be set very easily by the disk inclination, and is always stable without being influenced by the variation in the assembly size on the optical pickup side or the variation in the bobbin driving sensitivity. A focus position variation can be obtained.

The present invention is not limited to the above-described embodiment, but includes, for example, the following. (1) In the central region WD (see FIG. 4), since the change in the RF signal level of the light receiving element in the region is small,
The laser emission power for the optical disk may be controlled according to the RF level value. (2) In the above embodiment, the optical disk is tilted, but the optical disk may be vibrated in the vertical direction. In this case, the same effect can be obtained by vibrating a disk piece or a reflecting mirror instead of the optical disk.

(3) In the above embodiment, the position information of the light receiving element is obtained from the X and Y position signals. However, the position change characteristics of the RF signal level may be used together. (4) In the above embodiment, the position adjustment of the light receiving element is automatically performed by providing the X and Y position control amplifiers and the driving mechanism in the XY directions. However, the light receiving element is manually adjusted based on the position detection result. May be configured as a manual adjustment device that drives the. (5) In addition, the circuit configuration can be variously changed in design to achieve the same operation, and those are also included in the present invention. For example, it can be performed by software using a microcomputer or the like.

[0034]

As described in the foregoing, according to the light receiving element position adjusting apparatus for an optical pickup according to the present invention, light Di
The light beam reflected from the disc is divided into four light receiving surfaces of the light receiving element.
Of the light receiving surfaces at the approximate center where the four light receiving surfaces intersect in a plane.
Adjust the position of the quadrant light receiving surface in the XY plane direction so that
When performing the operation, the optical disc is forcibly tilted and supported while being supported.
Rotate faster than normal rotation and light the optical disc
The optical axis of the optical beam within the range including the focus position of the pickup
In the direction of the photodetector.
Each output signal of the
It changes according to the position, so the change
Deviation position in the XY plane direction with respect to the approximate center of the divided light receiving surface
Position information, and based on this displacement position information
The light beam is placed at approximately the center of the four-division light-receiving surface of the four-division light-receiving element.
Adjust the position of the 4-split light receiving surface in the XY plane direction to receive light
Therefore, there is an effect that the position of the light receiving element can be easily and accurately adjusted in a short time.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a light-receiving element position adjusting device of an optical pickup according to the present invention.

FIG. 2 is an explanatory diagram showing an arrangement of optical disks in the embodiment.

FIG. 3 is a time chart showing an operation in the embodiment.

FIG. 4 is a signal waveform diagram showing an operation in the embodiment.

FIG. 5 is a diagram showing position signal waveforms of the present embodiment and a conventional example.

FIG. 6 is an explanatory diagram showing a conventional technique.

FIG. 7 is an explanatory diagram showing the operation of the conventional technique.

FIG. 8 is an explanatory diagram illustrating an example of a light receiving element.

FIG. 9 is a waveform chart showing a position signal in the light receiving element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 14 ... Light receiving element 16, 18 ... Operational amplifier 20 ... Optical disk (light emission means) 22 ... Optical pickup 24 ... RF level detection circuit 26 ... X position signal calculation circuit (calculation means) 28 ... Y position signal calculation circuit (calculation means) Reference Signs List 30 control circuit 32, 34 position detection circuit (computing means) 36 focus drive circuit 38 X position control amplifier 40 Y position control amplifier 42 spindle motor 44 X, Y direction drive mechanism

Claims (1)

(57) [Claims] An optical beam output from an optical pickup.
Irradiates the optical disk with light
The four-division type light receiving element for receiving the light beam is mounted on the optical pickup.
And preparing the light beam for the light receiving element.
Among the four divided light receiving surfaces, the four divided light receiving surfaces intersect in a plane.
The four-divided light receiving surface is XY plane so as to receive light at the approximate center.
Position of the light receiving element of the optical pickup that adjusts the position in the direction
An adjusting device for normal rotation of the optical disc while forcibly supporting and tilting the optical disc.
Rotating the optical disc at a higher speed than the
The light beam within a range including the focusing position of the optical pickup;
Displacing means for displacing in the optical axis direction of the optical disk;
When displaced in the optical axis direction, the light receiving element
The light receiving elements based on output signals respectively output from the surfaces.
To the XY plane direction with respect to the approximate center of the
Calculating means for obtaining the shift position information, based on the shift position information output from the calculating means,
Approximately the center of the light beam divided into four light receiving surfaces of the light receiving element.
Position the 4-divided light receiving surface in the XY plane direction so as to receive light at
An XY direction drive mechanism for performing adjustment, comprising: a light receiving element position adjusting device for an optical pickup.