JP2001067687A - Optical information recording/reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely record/reproduce information even when axes of a drive system and an optical system scanning an optical card are loaded tilted with respect to a horizontal surface by measuring deviation from a target value of a focus control signal in a central position of a recording area of an optical information recording medium and correcting the focus control signal using the deviation. SOLUTION: A positional relation of a carriage with a light spot is decided, and the carriage is sought to an information track positioned on the center of the information recording surface of the optical card. The seek is performed by moving the carriage in the track traverse direction and controlling a stop position with an MPU 203 based on a tracking control signal. Thereafter, an optical head is scanned to the center of the information track, and the deviation from the target value of the focus control signal Af at the prescribed point of the optical card. Then, an offset canceling the deviation is generated, and is recorded in the memory of the MPU 203, and is added to the target value through a D/A converter 205.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for recording information on an optical information recording medium or reproducing the recorded information.

[0002]

2. Description of the Related Art Conventionally, various types of recording media for optically recording information and reading recorded information, such as a disk, a card, and a tape, are known. These optical information recording media include those that can be freely recorded and reproduced, those that can be additionally recorded and reproduced, and those that can only be reproduced. In particular, it is considered that the use of an optical card as a recording medium will be expanded due to features such as ease of manufacture, portability, and accessibility. Various optical information recording / reproducing apparatuses for this optical card have been proposed.

In such an optical information recording / reproducing apparatus, information is recorded and reproduced while always performing auto-tracking and auto-focus control. In addition, information is recorded on the recording medium by modulating according to the recording information and scanning the information track with a light beam narrowed down into a minute spot, and a series of information is recorded as an optically detectable information pit row. Is done.

[0004] In reproducing information from a recording medium, a light beam spot having a power as low as not to be recorded on the medium scans an information pit row of an information track and reflects light or transmitted light from the recording medium. Is detected, and the recorded information is reproduced based on the obtained detection signal.

FIG. 9 is a diagram showing a configuration example of an optical system of such an optical information recording / reproducing apparatus. In FIG.
Reference numeral 101 denotes a semiconductor laser as a recording / reproducing light source. The luminous flux emitted from the semiconductor laser 101 is collimated by a collimator lens 102 and then divided into a plurality of luminous fluxes by a diffraction grating 103. The split light beam passes through the polarizing beam splitter 104 and the quarter-wave plate 105 and passes through the objective lens 10.
At 6, the light is focused on the optical card 107 as a minute light spot.

The reflected light from the optical card 107 is detected by a photodetector 109 via an objective lens 106, a quarter-wave plate 105, a polarizing beam splitter 104, and a toric lens 108. An information reproduction signal and a tracking and focus control signal are generated by the detection signal.

[0007] Of the light beams split by the diffraction grating 103, recording, reproduction, and focus control (hereinafter, referred to as AF) are performed using the 0th-order diffracted light, and tracking control is performed using ± 1st-order diffracted light. (Hereinafter referred to as AT). In this case, AF is an astigmatism method, AT
Is a three-beam system.

FIG. 10A is a schematic plan view of an optical card. The optical card 107 has a large number of information recording / reproducing tracks arranged in parallel, some of which are T1, T2, T3.
It is shown as ... This track is divided by tracking tracks tt1-tt4. The tracking tracks tt1-tt4 are grooves or tracks T
1-T3 is formed of a material having a different light reflectance, and is used as a guide for obtaining a tracking signal. Further, the focus is pulled in at the position of the HP in the figure without a track.

FIG. 10A shows an example in which information is recorded or reproduced on the track T3. The 0th-order diffracted light 110 for recording, reproduction and AF is recorded on the track T3 by A
The ± first-order diffracted lights 111 and 112 for T are respectively tracking t
It is irradiated at t3 and tt4. Here, the diffracted light 11
A tracking control signal is obtained from the reflected light from the light sources 1 and 112, and the zero-order diffracted light 110 is controlled so as to scan the track T3 correctly. Also, the diffracted lights 110, 111,
Reference numeral 112 scans the information track of the optical card 107 right and left on the drawing while maintaining the same positional relationship under AF and AT control.

In this scanning method, there are a method of moving the optical system and a method of moving the optical card. In either method, the optical system and the optical card reciprocate relative to each other.
Non-constant speed parts occur at both ends of the optical card. This state is shown in FIG. The horizontal axis of FIG. 10B represents the horizontal direction of the optical card, and the vertical axis represents the relative scanning speed between the optical system and the optical card. Usually, the optical card 107
Is used as a recording area.

FIG. 11 shows each diffracted light 110 of FIG.
It is the elements on larger scale of -112. The 0th-order diffracted light 110 for recording, reproduction, and AF is the ± 1st-order diffracted light 111, 1 for AT.
12 and scans the center of the track T3.
The shaded portions 113a, 113b, and 113c are recording rows by the 0th-order diffracted light 110 due to the strong power of the semiconductor laser 101, and are generally called pits.

Since the pits 113a, 113b, and 113c have different reflectivities from those around the other recording rows, the weak light spots 110 are again emitted.
, The reflected light of the zero-order diffracted light 110 becomes pit 113
Modulated by a, b, and c to obtain a reproduced signal. Also, A
The ± first-order diffracted lights 111 and 112 for T are applied to the periphery of the recording row and to the tracking tracks tt3 and tt4, and the reflected light provides a tracking control signal.

FIG. 12 is a circuit diagram showing details of the photodetector 109 of FIG. 9 and a signal processing circuit. In FIG.
The photodetector 109 includes a four-divided optical sensor 114 and an optical sensor 11
It is composed of 5,116 optical sensors in total.
The light spots 110a, 111a, and 112a are the diffracted lights 110, 11 in FIG.
11 shows reflected light from optical cards 1,112.

The light spot 110a is a four-divided optical sensor 11
4, and the light spots 111a and 112a are collected on the optical sensors 115 and 116, respectively. Sensor outputs in the diagonal directions of the four-divided sensor 114 are added to an adder 117,
Each is added at 118. Further, the gain switching signal output from the MPU 203 is applied to the operational amplifier circuits 119 and 120.
And input to the adder circuits 121 and 122 to switch the gain of each circuit.

The outputs of the adders 117 and 118 are similarly added by an adder 121 and reproduced as an information reproduction signal RF. That is, the information reproduction signal RF is transmitted to the four-division optical sensor 11.
4 corresponds to the sum total of the light spots 110a condensed at 4. Further, the outputs of the adders 117 and 118 are subtracted by the differential circuit 120 to become a focus control signal Af.

That is, the focus control signal Af is the difference between the sums of the four divided optical sensors 114 in the diagonal directions. Since the astigmatism method is well known in the literature, the description is omitted here. Outputs of the optical sensors 115 and 116 are subtracted by a differential circuit 119 to become a tracking error signal At. Normally, the tracking error signal At is controlled so as to become 0,
As a result, tracking control for scanning the light spot following the information track is performed.

The outputs of the optical sensors 115 and 116 and the addition circuits 117 and 118 are added by an addition circuit 122.
It becomes the focus light amount signal Pf. That is, the focus light amount signal Pf is output from the four-divided sensor 114 and the optical sensors 115 and 11.
6, light spots 110a, 111a, 112a
Is equivalent to the sum of

Next, the configuration of the drive system of the optical information recording / reproducing apparatus will be described with reference to the drawings. In FIG.
Denotes an MPU for controlling each part of the apparatus, 302 denotes a pulse motor which is a driving source for reciprocating the movable optical head 301 in the track direction of the optical card 107, and is rotated by a micro step driver 303. I have.

An optical card 107 as an information recording medium is mounted on a carriage 309. The carriage 309 is configured to be able to move in a direction traversing the track of the optical card 107 by driving the DC motor 308 and to seek an optical spot to a desired track of the optical card 107. The DC motor 308 is operated by the carriage drive circuit 30 based on an instruction from the MPU 203.
7 is controlled.

On the upper surface of the optical card 107, the optical card 10
7, a movable optical head 301 for irradiating a light beam for recording and reproduction is arranged opposite to the optical head. The optical head 301 has the same configuration as the optical system of FIG. 9 described above. Optical head 3
01 is attached to the endless belt 310 and the pulley 31
A reciprocating motion of the optical card 107 in the track direction is performed by a drive system composed of 1, 312 and a pulse motor 302.

Reference numeral 304 denotes a laser drive circuit for driving a semiconductor laser in the optical head 301 based on an instruction from the MPU 203. The information beam is intensity-modulated by a predetermined modulation method when recording information, and the light beam is reproduced when information is reproduced. The semiconductor laser is controlled so that the power of the beam cannot be recorded. An AT 305 drives an AT coil and an AF coil based on a detection signal of a photodetector in the optical head 301, displaces an objective lens in a tracking direction and a focus direction, and performs tracking control and focus control.
/ AF control circuit.

Reference numeral 306 denotes a reproducing circuit for reproducing recorded information based on a detection signal of a photodetector in the optical head 301. The reproduced signal is output to the MPU 203,
The PU 203 performs predetermined signal processing on the reproduced signal to generate reproduced data.

FIG. 5 is a diagram showing an AF control circuit of the optical information recording / reproducing apparatus. In FIG. 5, focusing is performed using the focus control signal Af created in FIG. 201 is a phase compensation circuit for performing phase compensation of the focus control signal, and 202 is a focus control signal A.
An A / D converter for detecting f. The A / D converter 202 outputs a focus control signal A as described later.
The zero cross and the deviation component of f are detected and output to the MPU 203.

The movable portion including the objective lens 106 is supported by two spiral springs so as to have a degree of freedom in a direction perpendicular to the optical card. The output of the phase compensation circuit is
AF coil driver 21 for driving AF coil 211
0, the movable portion including the objective lens 106 is configured to move in a direction perpendicular to the recording information surface by driving the AF coil driver 210.

FIG. 6 is a diagram showing a change in the focus control signal Af with respect to the distance when the objective lens is driven in a direction perpendicular to the optical card surface. When the objective lens is moved from the side closer to the optical card surface (negative side of the x-axis) toward the in-focus position, the focus control signal Af temporarily becomes negative near the in-focus point and becomes 0 at the in-focus point. After passing through the focal point, it becomes positive once, and then converges to 0 as the objective lens moves away.

At the time of the focus pull-in operation, the MPU 2
In accordance with a command from 03, the objective lens is moved toward the in-focus position by a circuit (not shown). The AF coil 211 is driven by the function of the position control loop, and the objective lens gradually moves toward the in-focus position.

When approaching the in-focus position, the focus control signal Af crosses zero at the in-focus point as shown in FIG. The A / D converter 202 detects this zero cross, and
Inform U203 of the zero-cross timing. MPU
Numeral 203 turns on the focus control loop at the timing of zero crossing (t = t0), and performs focus pull-in so that the voltage at point C in FIG. 5, which is the difference between the target value and the focus control signal Af, becomes 0. . Thereafter, the focus servo state is established.

However, when the focusing servo is applied so that the focus control signal Af becomes 0 with the target value being 0, the voltage of the focus control signal Af is not 0,
Due to the effect of the spring used in the actuator, V
_error A deviation of [V] occurs. This is shown in FIG.
Therefore, even if the objective lens is driven such that the focus control signal Af becomes 0 with the target value set to 0, defocus occurs by the deviation.

In consideration of this deviation, the operation is performed so that the objective lens is focused at the in-focus position. This is shown in FIG. When the focus is pulled in at the home position, the deviation of the focus control signal Af + V
_{The error} [V] is measured, the target voltage output from the MPU 203 through the D / A converter 205 to the point B in FIG. 5 is set to −V _error [V] as shown in FIG. Servo is applied so that the output C of the amplifier 204, that is, the difference between the focus control signal Af and the target value becomes zero.

That is, the voltage of the target value is -V _error [V].
Gives the offset of By doing this,
As shown in FIG. 8B, the focus control signal Af
The servo is applied with -V _error [V] as the target value.
When the _error increases by V _error [V] due to the deviation, the operation is stabilized. As a result, the focus control signal Af becomes 0, and the objective lens is stabilized at the in-focus position.

[0031]

However, when the focusing servo is applied by the focusing method as in the prior art, the axis of the drive system for scanning the optical card and the axis of the drive system of the optical system are aligned with the horizontal plane. When the optical card is tilted with respect to the horizontal plane, or when the optical card is mounted with the tilt, the focus control signal Af is set according to the amount of displacement of the objective lens in order to focus following the displacement of the tilt. Of the objective lens greatly deviates from the in-focus position, which makes it difficult to accurately record and reproduce information.

Also, in order to keep the deviation within a certain range even with a large displacement, the open loop gain must be increased, so that small scratches and dust on the surface of the optical card can be obtained. Has also a problem in that the focus is shifted.

Therefore, according to the present invention, the axis of the drive system for scanning the optical card or the axis of the drive system of the optical system is inclined with respect to the horizontal plane, or the optical card is mounted with the inclination with respect to the horizontal plane. It is an object of the present invention to provide an optical information recording / reproducing apparatus which records / reproduces information accurately even when the information is recorded.

[0034]

In order to solve the above-mentioned problems, the present invention provides a method for irradiating an optical information recording medium with a light spot and performing focus control of the light spot based on a focus control signal. In an optical information recording / reproducing apparatus for recording or reproducing recorded information, means for measuring a deviation from a target value of a focus control signal at a center position of a recording area of the optical information recording medium, and using the measured deviation Means for correcting the focus control signal.

[0035]

Embodiments of the present invention will be described below with reference to the drawings. Note that the focus control circuit according to the optical information recording / reproducing apparatus of the embodiment of the present invention is the same as that shown in FIG.

FIG. 1A is a flowchart showing the procedure of the operation of the embodiment of the present invention. FIG. 1B is a top view of the optical card 107. The operation of the present embodiment will be described with reference to FIGS. First,
When the MPU 203 recognizes that the optical card 107 has been loaded on the carriage 309 of the optical information recording / reproducing apparatus (step S1), a focus pull-in operation is performed (step S2). During focus pull-in operation, the MPU
In accordance with a command from 203, the objective lens 106 is moved toward a focus position by a circuit (not shown).

The AF coil 211 is driven by the position control loop, the objective lens 106 gradually moves toward the focus position, and the focus control signal Af crosses zero at the focus point. The A / D converter 202 detects the zero cross, and notifies the MPU 203 of the timing of the zero cross.

The MPU 203 turns on the focus control loop at the timing of zero crossing so that the value of the focus control signal Af becomes 0, that is, the differential amplifier 204 which is the difference between the target value 0 and the value of the focus control signal Af. The focus is drawn so that the output (point C in FIG. 5) becomes zero. Thereafter, the focus servo state is established.

The focus pull-in operation is as shown in FIG.
Is performed at the home position HP located at the end of the optical card 107 shown in FIG. 7, and when the optical card 107 is loaded on the carriage 309, the light spot irradiates the home position HP. Determine the positional relationship.

Then, in this state, the optical head is sought to the information track located at the center of the information recording surface of the optical card 107 (step S3), and the objective lens 106 is displaced on the information track in the cross-track direction. Let me
Tracking control is performed so that the light spot is located at the center of the information track (step S4). The seek to the target information track moves the carriage 309 in the cross-track direction, and based on the tracking control signal, the M
This is achieved by the PU 203 controlling the stop position.

Thereafter, the optical head is scanned toward the center of the information track (step S5), and the deviation of the focus control signal Af from the target value at the point a of the optical card 107 shown in FIG. 1B is measured. (Step S6) An offset for canceling the deviation is generated and stored in the memory of the MPU 203 (Step S7), and is added to the target value through the D / A converter 205.

Here, FIG. 3A is a diagram in which a focusing drive system of a spring actuator is modeled.
In FIG. 3A, m is the mass of the movable part including the objective lens 106, k _F is the spring constant of the spring supporting the movable part in the actuator, and D _F is the viscosity coefficient.

When an equation of motion is established for this model,

[0044]

(Equation 1) Becomes g represents gravitational acceleration. When the above equation is Laplace transformed,

[0045]

(Equation 2) Is obtained.

FIG. 3B is a block diagram of the focusing servo system. R (s) represents the target position of the objective lens for focusing following the inclination of the drive shaft with respect to the horizontal plane and the inclination of the optical card 107 with respect to the horizontal plane. From FIG. 3B, the deviation E which is a focusing error is obtained.
When (s) is obtained,

[0047]

(Equation 3) Becomes However, in FIG.

[0048]

(Equation 4) And α is the product of the gain of the detection system and the drive amplifier and the actuator thrust constant. Here, the target position change R
Occurs, the steady-state deviation ε due to the influence of the change R is

[0049]

(Equation 5) And the deviation increases in proportion to R.

For example, as shown in FIG. 2A, when the axis of the drive system of the optical head is inclined with respect to the horizontal plane, the target of the focusing control signal Af is proportional to the amount of displacement of the objective lens. The deviation from the value becomes large, and the deviation at the points a to c is V V shown in FIG.
_Aerror ~ V _Cerror . In this case, the optical card 1
In the vicinity of the point c of FIG.
6 also deviates greatly from the in-focus position, making it difficult to record and reproduce accurate information.

Then, as described above, the deviation of the focusing control signal Af from the target value at the point a is measured, and
An offset for canceling the deviation is generated, stored in the memory, and added to the target value. Then, the deviation can be _kept within a certain range like _V'Aerror , _V'Berror , and _V'Cerror shown in FIG. As a result, the objective lens 106 is focused near the focus position on the entire information recording surface.

Further, the deviation from the target value at the point a may be caused when the axis of the drive system for scanning the optical card or the drive system of the optical system is inclined with respect to the horizontal plane, or the optical card is inclined with respect to the horizontal plane. Even in this case, it can be regarded as the center value of the deviation generated by displacing the objective lens to follow the displacement of the inclination in order to focus on the entire information recording surface.

Therefore, by adding an offset for canceling the deviation at the center of the information recording surface of the optical card to the target value, the axis of the drive system in the track transverse direction of the optical card is inclined with respect to the horizontal plane. Also, the deviation due to the inclination can be kept within a certain range.

As described above, in the present embodiment, the optical card 1
07, a deviation from a target value of the focusing control signal Af is measured at the center of the information track located at the center of the information recording surface, an offset for canceling the deviation is generated, and the target value considering the deviation is used. Records and reproduces information.
Therefore, even when the drive system for scanning the optical card 107 or the drive system of the optical system is inclined with respect to the horizontal plane, or when the optical card 107 is mounted with the inclination with respect to the horizontal plane, information is accurately recorded.・ Playback is possible.

In this embodiment, the case where the optical head is scanned is described. However, since it is sufficient to perform relative scanning between the optical head and the carriage, even if the carriage is scanned, both of them are scanned. You may.

In this embodiment, a case where a spring-based actuator is used has been described. However, an actuator having an elastic system other than a spring may be used.

[0057]

As described above, the present invention measures the deviation of the focus control signal from the target value at the center position of the recording area of the optical information recording medium, and uses the measured deviation to determine the focus control signal. Is corrected.

Therefore, since focus control is performed based on the focus control signal corrected within the allowable range,
Even if the axis of the drive system for scanning the optical card or the axis of the drive system of the optical system is inclined with respect to the horizontal plane, or if the optical card is mounted with the inclination with respect to the horizontal plane, accurate information can be obtained. Can be recorded and played back.

[Brief description of the drawings]

FIG. 1 is a flowchart showing an operation of an embodiment of the present invention and a top view of an optical card.

FIG. 2 is a diagram illustrating a state in which an axis of a drive system of an optical head is tilted and signals at this time.

FIG. 3 is a model diagram of a spring actuator of the optical information recording / reproducing apparatus and a block diagram of a focusing system.

FIG. 4 is a diagram showing a configuration of a drive system of the optical information recording / reproducing apparatus.

FIG. 5 is a diagram illustrating an AF control circuit portion of the AT / AF control circuit of the focus pull-in device.

FIG. 6 is a diagram illustrating a change in a focus control signal Af with respect to a distance when an objective lens is driven.

FIG. 7 is a diagram illustrating a state in which a deviation of V _error [V] occurs due to the influence of a spring used in an actuator.

FIG. 8 is a diagram showing a focus control signal in the optical information recording / reproducing device.

FIG. 9 is a diagram showing an optical system of the optical information recording / reproducing apparatus.

FIG. 10 is a diagram showing the relationship between the information recording surface of the optical card and the scanning speed for the area.

11 is an enlarged view showing a part of the optical card of FIG. 10;

FIG. 12 is a diagram illustrating a light detection unit of the optical system of FIG. 9 and a signal processing circuit that processes an output signal thereof.

[Explanation of symbols]

 Reference Signs List 101 semiconductor laser 106 objective lens 107 optical card 109 photodetector 114 quadruple sensor 115, 116 optical sensor 119, 120 differential circuit 121, 122 addition circuit 201 phase compensator 202 A / D converter 203 MPU 205 D / A converter 206 Dip switch 207 Acceleration sensor 210 AF coil driver 211 AF coil

Claims (1)

[Claims] 1. An optical information recording / reproducing apparatus that irradiates an optical information recording medium with a light spot and records information or reproduces recorded information while performing focus control of the light spot based on a focus control signal. The optical information recording medium further comprises: means for measuring a deviation of a focus control signal from a target value at a center position of a recording area of the optical information recording medium; and means for correcting the focus control signal using the measured deviation. Optical information recording / reproducing device.