JP3731564B2 - Optical disk device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technique for preventing an optical pickup and an optical disk on which data is recorded or reproduced from colliding with each other when an out-of-focus condition occurs due to an external impact or the like in an optical disk apparatus.
[0002]
[Prior art]
The optical disk apparatus is configured to emit laser light from an optical pickup so that the recording surface of the optical disk is focused while rotating the optical disk at high speed in order to record data on the optical disk or to reproduce data recorded on the optical disk. Irradiate. However, in the optical disk device, when the optical disk is rotated at a high speed, the recording surface of the optical disk vibrates due to the warp / surface vibration of the optical disk itself or the vibration of the optical disk rotation driving motor. As a result, the data cannot be recorded or reproduced successfully. Therefore, the optical disk apparatus keeps the distance between the optical pickup and the recording surface of the optical disk constant by the focus servo mechanism, and always converges the laser beam on the recording surface of the optical disk to stably record and reproduce data. Yes.
[0003]
In order to perform focus servo, the optical disc apparatus detects the distance between the optical pickup and the recording surface of the optical disc by a detecting means, and generates a focus error signal according to the distance. For example, an optical disc apparatus receives reflected light from an optical disc with a four-division photodiode (hereinafter referred to as a photodetector), and performs a calculation by an astigmatism method or a Foucault method to generate a focus error signal. . Then, the focus servo mechanism displaces the objective lens of the optical pickup in the focus direction (direction orthogonal to the recording surface of the optical disk) by the focus actuator in response to the focus error signal.
[0004]
Here, details of how to obtain the focus error signal will be described. FIG. 4 is a diagram showing the relationship between the photodetector and the beam spot. FIG. 5 is a diagram showing the relationship between the focus error signal and the distance between the recording surface of the optical disk and the optical pickup. As an example, a case where the distance between the recording surface of the optical disc and the optical pickup is detected using an astigmatism method will be described. As shown in FIG. 4 (A), the photodetector 13 is composed of four divided photodetector elements 13a to 13d. When the distance between the recording surface of the optical disk and the optical pickup is the optimum value, that is, when the focus of the laser beam is on the recording surface of the optical disk, as shown in FIG. The light spot (focal point) is set to be substantially circular at the center of the photodetector 13. When the distance between the recording surface of the optical disk and the optical pickup is short, that is, when the focus of the laser beam is on the back side with respect to the recording surface of the optical disk, as shown in FIG. The direction of the elements 13b and 13d is an elliptical beam spot having an ellipse. Further, when the distance between the recording surface of the optical disc and the optical pickup is long, that is, when the focus of the laser beam is closer to the front side than the recording surface of the optical disc, as shown in FIG. The direction of the elements 13a and 13c is an elliptical beam spot having an ellipse.
[0005]
Thus, the shape of the spot formed on the photodetector 13 differs depending on the distance between the recording surface of the optical disc and the optical pickup. Therefore, the reproduction signals A to D obtained from the light detection elements 13a to 13d are
FE = (A + C)-(B + D)
By performing arithmetic processing as described above, a focus error signal FE that changes in accordance with the distance between the recording surface of the optical disc and the optical pickup is obtained.
[0006]
The level of the focus error signal FE is an S-shaped curve as shown in FIG. In the optical disk apparatus, the focus servo is performed so that the focus error signal FE becomes 0 because the focus error signal FE is 0 when the spot is a perfect circle shown in FIG. However, the focus error signal FE is 0 even when the distance between the recording surface of the optical disc and the optical pickup is long or close, that is, when the focus is out of focus. Therefore, in this case, the distance between the recording surface of the optical disc and the optical pickup cannot be set to an optimum value. Therefore, conventionally, the defocus detection is performed using the full addition signal (RF signal) RF of the reproduction signals A to D obtained from the light detection elements 13a to 13d. The full addition signal (RF signal) RF is
RF = A + B + C + D
It is represented by As shown in FIG. 5B, the full addition signal RF is maximized when the distance between the recording surface of the optical disk and the optical pickup is an optimum value, and decreases as the distance increases or the distance decreases. Therefore, by using the focus error signal FE and the full addition signal RF, focus servo can be performed so that the distance between the recording surface of the optical disk and the optical pickup becomes an optimum value.
[0007]
The focus error signal varies depending on the operation mode of the optical disk device, the type and variation of the optical disk, and the like. For example, the reflectivity differs between a write once optical disc and a rewritable optical disc, and the reflectivity varies depending on the model number even with an optical disc of the same recording method. For this reason, the amplitude of the output signal of the photodetector varies due to variations in the optical disc, and the accuracy of the focus servo decreases due to the amplitude variation of the focus error signal. Therefore, conventionally, an AGC (Automatic Gain Control) circuit that automatically sets the focus error signal FE to an optimum magnitude has been used. The output signal of the AGC circuit is supplied to the signal processing circuit, and a focus servo drive signal is formed. This focus servo drive signal is supplied to an electromagnetic actuator via a drive amplifier (drive circuit). Then, the objective lens of the optical pickup is displaced in the focus direction by the actuator.
[0008]
FIG. 6 is a waveform diagram of a full addition signal, a focus error signal, and a focus drive signal when a defocus occurs in a conventional optical disc apparatus. In the optical disc apparatus, when the irradiation position of the laser beam deviates from the recording / reproducing area of the optical disc, the focus servo becomes abnormal and the objective lens and the optical disc may collide. For example, when the focus is lost due to an external impact or the like, the level of the full addition signal RF of the photodetector decreases. Further, the focus error signal FE becomes almost 0 as described above. Therefore, the optical disc apparatus recognizes that the focus has been lost. The optical disc apparatus is set to turn off the focus servo process when recognizing that the focus is lost. On the other hand, if the optical disk is scratched / dirt / debris, the laser light applied to the optical disk is diffusely reflected, the levels of the total addition signal RF and the focus error signal FE are lowered, and defocusing occurs. Will be in the same state. However, there is little time for the levels of the full addition signal RF and the focus error signal FE to decrease due to dust or the like. Therefore, in the optical disc apparatus, the focus servo processing is set to be turned off when the levels of the full addition signal RF and the focus error signal FE are lowered even after a predetermined time T that is not affected by dust or the like has elapsed. Has been.
[0009]
However, in the optical disc apparatus, the original focus error signal is almost zero until the focus is lost and it is recognized that the focus is lost. Therefore, normally, even if noise is superimposed on the focus error signal, it is not affected by the noise. However, in the above case, if noise is superimposed on the focus error signal, the AGC circuit amplifies this noise. As a result, the amplitude of the focus drive voltage increases, the lens of the optical pickup swings greatly, and particularly when the objective lens is out of focus in the direction of approaching the recording surface of the optical disc, the objective of the optical pickup is placed on the recording surface of the optical disc. The lens sometimes collided.
[0010]
With respect to such problems, Japanese Patent Application Laid-Open No. 60-28034 discloses a technique related to an optical information recording / reproducing apparatus. According to this technology, when the focus servo system does not operate normally due to disturbance to the servo system, the state is detected regardless of whether the condenser lens starts to move away from the disk or in the approaching direction. Then, the light is detected by a light detection device comprising an amplifier, and the condensing lens is driven in a direction away from the disk to effectively prevent collision between the disk and the condensing lens. Therefore, it is possible to prevent collision between the condensing lens and the disk due to the disturbance of the servo system only by providing another optical detector and an amplifier in addition to the normal optical detector.
[0011]
Japanese Patent Application Laid-Open No. 9-305981 discloses a technique relating to an optical disc apparatus and an optical pickup control method. According to this technology, when the focus is lost, the focus actuator is immediately stopped to avoid collision between the objective lens and the optical disk, and the optical pickup and objective lens are forced to a position where there is no possibility of collision with the optical disk. The focus servo pull-in is performed at that position, and then the tracking and focusing for the original track are returned. Therefore, even when the optical disk is bent due to its own weight or the like, the objective lens of the optical pickup and the optical disk can be prevented from coming into contact with each other, and appropriate focusing can be performed.
[0012]
Further, Japanese Patent Application Laid-Open No. 11-120599 discloses a technique relating to an optical disk recording / reproducing apparatus and method. According to this technique, an optical disk recording / reproducing apparatus includes an objective lens that focuses laser light emitted from a laser light source disposed in an optical pickup on a signal recording surface of the optical disk, and the objective lens is recorded on the signal recording medium of the optical disk. A biaxial actuator that is an objective lens driving operation means for driving the objective lens by a driving voltage, and a focus servo pull-in operation, and the driving voltage is stored in the storage unit. And a control unit that is a control unit having a control function for preventing the objective lens from colliding with the optical disk when the stored predetermined level is exceeded. As a result, the optical disk recording / reproducing apparatus can prevent the objective lens from colliding with the optical disk even if the servo pull-in detection fails due to reasons such as dust adhering to the surface of the optical disk.
[0013]
In addition, Japanese Patent Laid-Open No. 2-206025 discloses a technique related to a focus servo device. In this focus servo device, a light intensity monitoring circuit and a reference voltage circuit for monitoring the amount of reflected light and detecting deviation from the recording / reproducing area are added, and when the deviation from the recording / reproducing area occurs, the servo loop is opened to respond to the focus error. A switch for inhibiting the actuator drive is inserted between the AGC circuit and the phase compensation circuit. Therefore, if the actuator deviates from the recording / reproducing area, the actuator driving is suppressed before the exciting current of the driving coil becomes excessive, so that there is no fear of contact accident between the objective lens and the optical disk.
[0014]
There has also been a method of preventing a direct collision between the objective lens and the recording surface of the optical disk by attaching an impact buffering material around the objective lens.
[0015]
[Problems to be solved by the invention]
However, the above conventional method has a problem that it is necessary to add a new member, leading to an increase in the cost of the optical disk apparatus. In addition, as described in the above publication, when a switch is added as a new member, noise may occur when the switch is opened or closed, causing the focus actuator to malfunction and causing a collision between the optical pickup and the optical disk. There is.
[0016]
Accordingly, an object of the present invention is to provide an optical pickup device that can prevent the optical pickup and the optical disc from colliding with each other without adding a new member.
[0017]
[Means for Solving the Problems]
  In order to solve the above problems, the optical disc apparatus of the present invention has the following configuration. That is,
  Laser light is irradiated to the data recording surface of the optical disc through the objective lens, and the reflected lightIs received by a four-division photodiode.Reproduction signal detection means for generating an RF signal and an FE signal;
  Generated by the reproduction signal detecting means.The FE signal is amplified to a predetermined level by control according to the RF signal.Adjust the gain of FE signalFE signal is amplified with the adjusted gain.FE signal amplification means for
  By the FE signal amplification meansamplificationFocusing means for displacing the objective lens of the reproduction signal detection means in a direction perpendicular to the data recording surface of the optical disk based on the FE signal and condensing laser light on the data recording surface; In the provided optical disc apparatus,
  By the reproduction signal detection meansGenerationWhen the state in which the RF signal is lower than a predetermined level continues for a second time shorter than the first time, the FE signal amplification process is performed.StepStop,
  By the reproduction signal detection meansGenerationAnd a control means for stopping the focusing means when the state in which the RF signal is lower than a predetermined level continues for a first time.
[0018]
  In this configuration,The FE signal amplification means of the optical disc apparatus adjusts the gain of the FE signal so that the FE signal is amplified to a predetermined level by control according to the RF signal generated by the reproduction signal detection means, and the FE signal is adjusted with the adjusted gain. Amplify the signal. Also,The control means of the optical disk apparatus is the reproduction signal detection means.GenerationShiRWhen the state in which the F signal is lower than the predetermined level continues for a second time shorter than the first time, the FE signal amplifying operation is performed.StepStop. Also, SystemMeansReBy raw signal detection meansGenerated RWhen the state in which the F signal falls below a predetermined level continues for the first timeTheStop the focus means.
  Therefore, FE signal amplifierStepBy stopping, the level of the FE signal is reduced, so that the amount by which the focusing unit displaces the objective lens in the direction perpendicular to the data recording surface of the optical disk can be reduced. As a result, it is possible to prevent the objective lens from colliding with the recording surface of the optical disk when defocusing occurs. That is, in the optical disk apparatus, normally, even if noise is superimposed on the focus error signal, it is not affected by the noise, but when defocusing occurs, the level of the FE signal becomes almost zero, so the noise is included in the focus error signal. When the signal is superimposed, the FE signal amplification means amplifies this noise. As a result, the amplitude of the focus drive voltage increases, the lens of the optical pickup swings greatly, and particularly when the objective lens is out of focus in the direction of approaching the recording surface of the optical disc, the objective of the optical pickup is placed on the recording surface of the optical disc. The lens sometimes collided. However, the objective lensPlaceBy reducing the amount, it is possible to prevent a collision between the objective lens and the recording surface of the optical disc when defocusing occurs.
  Also, when the RF signal drops due to dust on the recording surface of the optical disk, it usually returns immediately to the original level. In such a case, the FE signalamplificationTo prevent the processing operation of the optical disk apparatus from becoming complicated.
  In addition, when the focus is continuously lost, the focus unit is stopped, and the optical disk apparatus is reset to recover from the focus failure.
[0023]
  Further, the control means includes the FE signal amplifier.StepIf the RF signal becomes larger than the predetermined level between the stop and the stop of the focusing means, the FE signal amplifying meansStopReleaseAnd operating the FE signal amplification means.It is characterized by that.
[0024]
  In this configuration, the FE signal amplifierStepIf the RF signal becomes higher than the predetermined level between the stop and the stop of the focusing means, the FE signal amplifying operation is performed.SteppedRelease suspensionTo operate the FE signal amplification means.. Therefore, when the RF signal continues to decrease for more than the second time due to dust on the recording surface of the optical disk.In addition,It is possible to return to normal operation.
[0025]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a schematic configuration of an optical disk reproducing apparatus according to the present invention. The optical disc apparatus 1 is configured to record data on the optical disc 2 and to reproduce the data recorded on the optical disc 2, with a spindle motor 3, a frequency generator 4, a motor drive circuit 5, an optical pickup 6, an encoder 14, a laser power. A control circuit 15, a laser drive circuit 16, a focus error signal generation circuit 21, a full addition signal generation circuit 22, a signal processing circuit 23, a decoder 24, a CPU 25, an AGC circuit 28, a phase compensation circuit 29, and a focus drive circuit 30 are provided. Yes. The optical pickup 6 includes an objective lens 7, a focus actuator control coil 8, a beam splitter 9, a collimator lens 10, a laser diode 11 including a photodiode 12, a photodetector (four-division photodiode) 13, and a cylindrical lens. 17 is provided. In addition, the CPU 25 includes a timer 26.
[0026]
The optical disc 2 is a recording medium capable of optically reproducing or recording / reproducing information. The spindle motor 3 drives the optical disc 2 to rotate. The frequency generator 4 is a sensor that detects the number of rotations of the spindle motor 3. The motor drive circuit 5 controls the rotation speed of the spindle motor 3 in accordance with the signal output from the frequency generator 4. The optical pickup 6 irradiates the recording surface of the optical disc 2 with a laser beam as a spot, and detects return light from the optical disc 2. The objective lens 7 focuses the laser beam on the recording surface of the optical disc 2. The control coil 8 moves the objective lens 7 in the focus direction. The beam splitter 9 separates the light emitted from the laser diode 11 and the return light from the optical disk 2. The collimator lens 10 converts light emitted from the laser diode 11 that is a point light source into parallel light. The laser diode 11 is a light source that emits laser light. The photodiode 12 is built in the laser diode 11 and detects the light amount of the laser diode 11. The photodetector 13 is a four-divided photodiode that detects return light from the optical disc 2 and includes photodetector elements 13a to 13d. The cylindrical lens 17 condenses the return light dispersed by the beam splitter 9 on the photodetector 13.
[0027]
The encoder 14 encodes the recording signal. The laser power control circuit 15 controls the power of the laser light emitted from the laser diode 11. The laser drive circuit 16 drives the laser diode 11 in accordance with the signal output from the laser power control circuit 15.
[0028]
The focus error signal generation circuit 21 generates a focus error signal (FE signal) FE based on the signal output from the photodetector 13. The full addition signal generation circuit 22 fully adds the signals output from the photodetector 13 and outputs a full addition signal (RF signal) RF. Here, if the output signals of the light detection elements 13a to 13d constituting the light detector 13 are A, B, C, and D, the focus error signal generation circuit 21 calculates FE = (A + C) − (B + D). Is going. Further, in the full addition signal generation circuit 22, a full addition signal RF = A + B + C + D, which is the sum of the output signals of the photodetecting elements 13a to 13d, is obtained as a read signal.
[0029]
The signal processing circuit 23 performs predetermined processing on the fully added signal RF. The decoder 24 decodes the full addition signal RF processed by the signal processing circuit 23 into a reproduction signal. The CPU 25 controls the AGC circuit 28 according to the full addition signal RF output from the full addition signal generation circuit 22. Further, the CPU 25 controls each part of the optical disc apparatus 1 such as the motor drive circuit 5 and the laser power control circuit 15. The timer 26 measures a fixed time (first time) T and a detection time (second time) t. The AGC circuit 28 automatically adjusts the gain of the signal output from the focus error signal generation circuit 21. The phase compensation circuit 29 compensates the phase of the signal output from the AGC circuit 28. The focus drive circuit 30 outputs a signal to the control coil 8 of the focus actuator, and moves the objective lens 7 in the focus direction (a direction perpendicular to the recording surface of the optical disk). Further, the distance between the objective lens 7 of the optical pickup 6 and the recording surface of the optical disc 2 is detected by the optical pickup 6, the focus error signal generation circuit 21, and the full addition signal generation circuit 22. In addition, focus servo is performed by the optical pickup 6, the focus error signal generation circuit 21, the AGC circuit 28, the phase compensation circuit 29, and the focus drive circuit 30.
[0030]
Next, the operation of the optical disc apparatus 1 will be described. When the user performs an optical disk reproduction operation using an operation unit (not shown) of the optical disk apparatus 1, a signal corresponding to the operation is transmitted to the CPU 25. The CPU 25 detects this operation, outputs a signal to the motor drive circuit 5, drives the spindle motor, and rotates the optical disc 2. Further, the CPU 25 outputs a signal to the laser power control circuit 15. The laser power control circuit 15 starts emitting laser light from the laser diode 11 via the laser driving circuit 16. The optical pickup 6 irradiates the recording surface of the optical disc 2 with laser light, and detects the return light from the optical disc 2 with the photodetector 13. Each light detection element 13a-13d which comprises the photodetector 13 outputs the signal according to the received laser beam. The focus error signal generation circuit 21 generates a focus error signal using the signal output from the photodetector. The full addition signal generation circuit 22 generates a full addition signal using the signal output from the photodetector.
[0031]
The full addition signal RF is output to the signal processing circuit 23 and the CPU 25. The signal processing circuit 23 performs a predetermined process on the full addition signal RF output from the full addition signal generation circuit 22 and outputs the result to the decoder 24. The decoder 24 decodes the signal output from the signal processing circuit 23 and outputs a reproduction signal. The CPU 25 constantly monitors the level decrease of the full addition signal RF. If the full addition signal RF is less than a predetermined value, the CPU 25 starts the timer 26 and measures the detection time t. If it is greater than or equal to the predetermined value, time is not measured.
[0032]
The AGC circuit 28 adjusts the gain of the focus error signal output from the focus error signal generation circuit 21, and outputs a signal adjusted to a predetermined level to the phase compensation circuit 29. The phase compensation circuit 29 performs phase compensation of this signal. To output a signal to the focus drive circuit 30. The focus drive circuit 30 outputs a focus drive signal to the control coil 8 of the focus actuator in accordance with the signal output from the phase compensation circuit 29, and moves the objective lens 7 to adjust the laser beam spot position.
[0033]
In the optical disc apparatus 1, the above operation is always performed during reproduction of the optical disc or data recording on the optical disc, and focus servo is performed so that the laser beam has an optimum spot diameter on the recording surface of the optical disc.
[0034]
Next, an operation when the level of the full addition signal RF is lowered in the optical disc apparatus 1 will be described. FIG. 2 is a waveform diagram of the full addition signal, the focus error signal, and the focus drive signal when the level reduction of the full addition signal RF occurs in the optical disc apparatus of the present invention. FIG. 3 is a flowchart for explaining the operation when the level of the full addition signal RF is lowered in the optical disc apparatus of the present invention.
[0035]
As shown in FIG. 2, the full addition signal RF has a substantially stable value in a state where no defocusing occurs. At this time, the focus error signal FE and the focus drive signal are substantially 0 level. When the optical disc apparatus 1 receives an impact or the like and loses focus, the full addition signal RF is in a state where the signal level is lowered. On the other hand, after the focus error signal FE fluctuates greatly in an S-shape, the original focus error signal becomes almost 0, and is in a state of being slightly moved by a noise component. Further, the focus drive signal fluctuates greatly in an S shape like the focus error signal FE, and the noise component of the focus error signal FE is amplified by the AGC circuit 28, and therefore fluctuates at a predetermined level.
[0036]
As described above, when the level of the full addition signal RF is reduced due to out of focus or the like in the optical disc apparatus 1, the optical disc apparatus 1 operates as follows. That is, when the CPU 25 detects that the total addition signal RF is less than a predetermined value (s1), the CPU 25 starts the timer 26 and starts measuring the detection time t (s2). When the total addition signal RF becomes a predetermined value or more before the detection time t elapses (s3), that is, when the decrease of the total addition signal RF is influenced by dust or the like on the recording surface of the optical disk, the CPU 25 detects it. The time t is stopped (s11), and the process of s1 is performed. On the other hand, the CPU 25 turns off the gain adjustment operation of the AGC circuit 28 (s5) when the full addition signal RF continues to be less than the predetermined value even after the detection time t has elapsed (s4). As a result, the noise component superimposed on the focus error signal is not amplified and the focus drive signal is finely moved, so that the objective lens 7 and the recording surface of the optical disc 2 collide with each other without the object lens 7 swinging greatly. Can be prevented.
[0037]
The CPU 25 turns off the AGC circuit 28 until it recognizes that the focus has been lost (s7), that is, between the time when the level of the full addition signal RF decreases and the fixed time T elapses. When RF becomes a predetermined value or more (s6), the gain adjustment operation of the AGC circuit 28 is turned on (s12), and the process of s1 is executed. On the other hand, when the predetermined time T has elapsed (s7), the CPU 25 turns off the focus servo (s8).
[0038]
It should be noted that when the gain adjustment operation of the AGC circuit 28 is turned on in s12 of the above process, the amplification factor may be set so as to increase gently. Thereby, it is possible to prevent the focus error signal FE from fluctuating suddenly and the objective lens from being suddenly displaced accordingly.
[0039]
The detection time t is preferably set according to the servo response of the optical disk device. In addition to DVD, CD, LD, and the like are suitable as the optical disk to be played back by the optical disk playback apparatus of the present invention.
[0040]
【The invention's effect】
  As described above, according to the present invention,By controlling according to the RF signal, the gain of the FE signal is adjusted so that the FE signal is amplified to a predetermined level, and the FE signal is amplified with the adjusted gain.FE signal amplifierStepBy stopping, the level of the FE signal is reduced, so that the amount by which the focusing unit displaces the objective lens in the direction perpendicular to the data recording surface of the optical disc can be reduced. As a result, it is possible to prevent the objective lens from colliding with the recording surface of the optical disc when defocusing occurs..
[0041]
  In addition, when the state in which the RF signal is lower than the predetermined level continues for a second time shorter than the first time, the FE signal amplification means is stopped, so the RF signal is attached to the recording surface of the optical disc. When it decreases due to dust or the like, it usually returns immediately to the original level. In such a case, the gain adjustment of the FE signal is stopped to prevent the processing operation of the optical disc apparatus from becoming complicated.
[0042]
  Further, when the state in which the RF signal is lower than the predetermined level continues for the first time, the focusing unit is stopped. Therefore, when the focus is continuously out of focus, the focusing unit is stopped and the optical disc apparatus is stopped. It is possible to recover from out of focus by performing a reset or the like.
[0043]
  Also, the FE signal amplifierStepIf the RF signal becomes higher than the predetermined level between the stop and the stop of the focusing means, the FE signal amplifying operation is performed.SteppedRelease suspensionTo operate the FE signal amplification means.Therefore, the normal operation can be restored even when the RF signal continues to decrease for a second time or more due to the influence of dust or the like on the recording surface of the optical disk.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of an optical disk reproducing apparatus according to the present invention.
FIG. 2 is a waveform diagram of a full addition signal, a focus error signal, and a focus drive signal when defocusing occurs in the optical disc apparatus of the present invention.
FIG. 3 is a flowchart for explaining an operation when an out of focus occurs in the optical disc apparatus of the present invention.
FIG. 4 is a diagram showing a relationship between a photodetector and a beam spot.
FIG. 5 is a diagram showing a relationship between a recording surface of an optical disc and a distance between an optical pickup and a focus error signal.
FIG. 6 is a waveform diagram of a full addition signal, a focus error signal, and a focus drive signal when defocus occurs in a conventional optical disc apparatus.
[Explanation of symbols]
1: Optical disk device
2: Optical disc
6: Optical pickup
7: Objective lens
13: Photodetector (quadrant photodiode)
21: Focus error signal generation circuit
22: Full addition signal generation circuit
25: CPU
26: Timer
28: AGC circuit

Claims (3)

Reproduction signal detecting means for irradiating the data recording surface of the optical disc with laser light through an objective lens and receiving the reflected light with a four-division photodiode to generate an RF signal and an FE signal;
FE signal amplifying means for adjusting the gain of the FE signal so that the FE signal is amplified to a predetermined level by control according to the RF signal generated by the reproduction signal detecting means, and amplifying the FE signal with the adjusted gain. When,
The objective lens of the reproducing signal detector means based on FE signal amplified by the FE signal amplifying means, is displaced in the direction perpendicular to the recording surface of the data of the optical disk, condensing the laser beam on the data recording surface In an optical disc device comprising a focusing means for causing light to be emitted,
When the RF signal generated state lower than a predetermined level is continuously shorter second time than the first time by the reproduction signal detecting means, stops the FE signal amplifying hand stage,
Thereafter, when the state in which the RF signal is further lowered below a predetermined level continues for the first time, the focus unit is stopped,
When the RF signal prior to successive said first time is greater than the predetermined level, to release the stop of the FE signal amplifying means, comprising a control means for operating the FE signal amplifying means An optical disc device characterized by the above. Reproduction signal detecting means for irradiating the data recording surface of the optical disc with laser light through an objective lens and receiving the reflected light with a four-division photodiode to generate an RF signal and an FE signal;
FE signal amplifying means for adjusting the gain of the FE signal so that the FE signal is amplified to a predetermined level by control according to the RF signal generated by the reproduction signal detecting means, and amplifying the FE signal with the adjusted gain. When,
The objective lens of the reproducing signal detector means based on FE signal amplified by the FE signal amplifying means, is displaced in the direction perpendicular to the recording surface of the data of the optical disk, condensing the laser beam on the data recording surface In an optical disc device comprising a focusing means for causing light to be emitted,
When the RF signal generated by the reproducing signal detecting means state lower than a predetermined level is continuously shorter second time than the first time, to stop the FE signal amplifying hand stage,
An optical disc apparatus comprising: control means for stopping the focus means when the state in which the RF signal generated by the reproduction signal detection means has fallen below a predetermined level continues for a first time. Said control means, after stopping the FE signal amplifying hand stage, until stopping the focusing means, when the RF signal is greater than the predetermined level, the stop of the FE signal amplifying means 3. The optical disc apparatus according to claim 2 , wherein the FE signal amplifying means is operated by canceling.

Images