JP2006313629A - Digital signal processor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that an error of losing information occurs, and drawing-in of focusing and tracking becomes unstable, when both a low-density disk and a high-density disk are reproduced and recorded. <P>SOLUTION: A DSP34 makes a light source of longer wavelength emit light to discriminate the type of the loaded disk 12, based on a signal from an amplitude detection means when a convergent lens 10 is driven for approaching a disk 12 and then receding from it. When the light source of the wavelength is discriminated, a filtering operation signal is supplied to a feedback loop. When it is not discriminated, the DSP34 instructs light emission of a light source of shorter wavelength. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical disc apparatus that optically records a signal on an information carrier using a light beam from a light source such as a laser and reproduces the recorded signal. The present invention relates to a digital signal processor that executes processing for controlling a focus position.

  An optical disk device for reproducing CD audio and CD-ROM normally uses a laser light source of 780 nm.

  On the other hand, a laser light source of 650 nm is used for a high-density optical disc (a disc having a higher density and a larger capacity than CD; here, abbreviated as SD).

By the way, a 780 nm long wavelength laser for CD and a 650 nm short wavelength laser for high density disk are mounted, CD, CD-R with 780 nm long wavelength laser, and high density disk SD with 650 nm short wavelength laser. Has been proposed (see, for example, Patent Documents 1, 2, and 3).
JP-A-8-221890 JP-A-10-64168 Japanese Patent Laid-Open No. 10-55606

  However, when the optical disc apparatus is loaded with a CD-R, if a short-wavelength laser is irradiated and the focus and tracking servos are operated, the light beam usually reaches the recording film about 1/4 to 1/2 round. There is an inconvenience that the converged irradiation causes the recorded information to disappear. The disappearance of the information is so large that it cannot be corrected even if error correction is performed, and it may be impossible to reproduce the information. The reason for the disappearance of the information is that the organic dye film of the CD-R using the organic dye film is usually designed so that the reflection characteristic at 780 nm is optimized, and therefore, a short wavelength laser of 650 nm or less is irradiated. In contrast, the light beam is absorbed. Therefore, it has been difficult to reproduce information by detecting the intensity of reflected light corresponding to information marked on the recording film. Further, the light beam spot is reduced, the power per unit area is increased, and the recorded information may be lost due to the absorption characteristics of the recording film itself.

  Further, in the conventional optical disc described above, when the CD playback speed is increased to 6 × speed, 12 × speed, or 24 × speed, the disc surface deflection and eccentric acceleration are the square of the playback speed (rotational speed). It increases in proportion to. Therefore, depending on disc variations and chucking variations, surface wobbling and eccentric acceleration are out of tolerance of focus and tracking control gains, so that there is a problem that control cannot be pulled in and a startup failure state occurs.

  Furthermore, it is difficult to ensure a constant torque characteristic with a spindle motor from a high speed rotation such as 24 times speed to a low speed rotation such as a standard speed, and disk rotation control becomes unstable in consideration of variations in the spindle motor. There is a problem that it becomes a jitter of the reproduction signal and deteriorates the performance.

  The present invention has been made to solve the above-mentioned problems of the prior art, and provides a startup control method for reproducing (or recording) both CDs and CD-Rs and new high-density disks. It is what we propose. Also, in order to realize high-speed CD playback, we propose a stable focus, tracking pull-in method and more stable rotation control method, and a new high-density optical disc playback and recording device that shares high-performance CD playback performance. The purpose is to provide.

  Since the present invention generally discriminates the type of a disk before performing focus and tracking control, it is a very short time (several ms or less) that the converged light beam hits the recording surface. Even if one is missing, the error can be sufficiently corrected, and there is no problem with information reproduction.

  Furthermore, the present invention provides a focus control and tracking control means by first irradiating the longest wavelength laser 1 in a device equipped with two or more lasers of long wavelength and short wavelength, for example, a device equipped with 3 lasers. In a state where it is not applied, it is discriminated whether the loaded disc is a CD or a CD-R, and if it is not a CD or CD-R, the laser 2 of the long wavelength is irradiated next, and similarly focus control and tracking control means It is determined whether or not the loaded disk is a high-density disk in a state where no light is applied. If the disk is not a high-density disk, the laser 3 having the shortest wavelength is irradiated and similarly the focus control and tracking control means are not applied. Then, it is determined whether the loaded disc is an ultra-high density disc. When the discriminating result when each laser is irradiated is determined to be a group of discs to be reproduced by the laser, focusing and tracking control is performed for the first time, and binarization and error correction are executed. Information is reproduced.

  Furthermore, according to the present invention, in a device having a large reproduction power (such as a reproduction compatible machine such as a CD-RW), by making a configuration in which light is emitted with a low laser power at the time of the above-mentioned discrimination, the discrimination should be wrong. Thus, even if the CD-R or the like is irradiated with a short wavelength laser, the loss of information can be completely prevented.

  Next, a configuration corresponding to the invention according to the present application will be described.

In the first aspect of the present invention, a digital filter operation including addition, delay, and multiplication is performed with a focus error signal that changes according to the distance between the optical disc and the focal point of the convergent lens as an input. A digital signal processor having a function of feeding back a control signal to the focus moving means after performing phase compensation,
Emitting a long wavelength laser; and
Moving the converging lens in a focus control direction;
Comparing the amplitude of the focus error signal with a predetermined value;
Closing the loop in which the feedback is performed if the amplitude of the focus error signal is greater than a predetermined value;
If the amplitude of the focus error signal is smaller than a predetermined value, emitting a short wavelength laser; and
Moving the converging lens in a focus control direction;
A digital signal processor with an algorithm that includes

  With the above configuration, the digital signal processor of the present invention can quickly identify the type of information carrier, for example, CD or SD, in the non-operating state of the focus control system, and shifts to the optimum focus control operation according to the information carrier. It is possible.

  The second aspect of the present invention is the digital signal processor according to the first aspect of the present invention, which executes a step of turning off the laser when no focus error signal is detected when the short wavelength laser is emitted.

  The third aspect of the present invention is the digital signal processor according to the first aspect of the present invention, which executes a step of emitting the long wavelength or short wavelength laser before issuing a command to rotate the optical disc.

  The fourth aspect of the present invention executes a process of feeding back the digital filter calculation result to the focus moving means after issuing a command to rotate the optical disk and before the optical disk reaches a predetermined number of rotations. The digital signal processor according to the first aspect of the present invention.

  The present invention can realize high-speed reproduction of conventional CDs and CD-Rs with high reliability, and can also reproduce or record new high-density discs with high reliability.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, members having the same function are denoted by the same reference numerals.

  FIG. 1 shows a block diagram of an optical disc apparatus that is equipped with two laser light sources having different wavelengths and reproduces two or more types of discs having different densities such as CD and SD.

  As shown in the figure, the optical disc apparatus of the present invention is a long-wavelength laser light source 1 that is an optical system for irradiating a light beam 11 onto a disc 12 that is an information carrier, and the light emitted from the light source 1 is converted into parallel light. A coupling lens 5, a laser light source 2 having a short wavelength, a coupling lens 6 for converting light emitted from the light source 2 into parallel light, a wavelength-dependent polarizing element 7, a polarizing beam splitter 8, an actuator 9, and a converging lens 10. Further, a laser control circuit 3 for controlling the laser light source 1 and a laser control circuit 4 for controlling the laser light source 2 are provided. Further, the optical disc apparatus of the present invention includes a digital signal processor (DSP) 34. The laser light sources 1 and 2 are controlled through laser control circuits 3 and 4 by a signal from a digital signal processor (DSP) 34.

  The light beam generated from the laser 1 is collimated by the coupling lens 5. The parallel light then passes through the wavelength-dependent polarizing element 7, then passes through the polarizing beam splitter 8, and is converged by the converging lens 10 that moves in the focus and tracking direction by the actuator 9, and the light beam spot is formed on the disk 12. It is formed.

  Similarly, the light beam generated from the laser 2 is collimated by the coupling lens 5. The parallel light then passes through the wavelength-dependent polarizing element 7, then passes through the polarization beam splitter, and is converged by the converging lens 10 that moves in the focus and tracking direction by the actuator 9, thereby forming an optical beam spot on the disk 12. Is done. The optical beams 11 a and 11 b generated by the lasers 1 and 2 are applied to the disk 12 rotated by the disk motor 13. These two optical beams are selectively used depending on the type of disc to be mounted.

  When a conventional disk such as a CD or CD-R is loaded, the laser light source 1 of 780 nm is caused to emit light via the laser control circuit 3 in accordance with a control signal from the digital signal processor 34. When a new high-density disk such as SD is loaded, the 650 nm laser light source 4 is caused to emit light via the laser control circuit 4 according to the control signal of the digital signal processor 34.

  This optical disk apparatus includes a four-divided light detector 15 as an element for receiving reflected light from the disk 12, and the reflected light from the disk 7 passes through a converging lens 10 and a polarization beam splitter 8 and is divided into four parts. The light enters the detector 15. The four-divided detector 15 has a dividing line configuration as shown in FIG. 2, and the sum signal of the diagonal lines A to D is added to the adder 21a via the current-voltage conversion amplifiers 20a, 20b, 20c, and 20d. , 21b, and the difference signal is taken by the differential amplifier 27 to form an astigmatism method to obtain a defocus signal FE. Each diagonal sum signal is binarized by comparators 22a and 22b, the phases of the binarized signals are compared by a phase comparator 23, and the output of the phase comparator 23 is denoised by a low-pass filter 24. A phase difference tracking signal TE (track deviation signal) is obtained.

  Further, the sum of the light amounts of the respective channels (detectors) A to D of the four-divided photodetector 15 is taken by the adder 25 and passed through the low-pass filter 28 to generate the total light amount signal AS. The same signal is similarly taken by a high-band adder 26, and this signal is envelope-detected to generate an RF envelope detection signal RFENV. The signal of the adder 26 is processed for gain control, equalizing, and the like, and becomes a signal for reading information on the disk 12. However, since it is not directly related to the present invention, detailed description thereof is omitted.

  The FE, TE, AS, and RFENV generated as described above are input to a digital signal processor (hereinafter, DSP) 34. This digital signal processor uses FE or TE as input, performs digital filter operation by addition, delay, and multiplication, performs low-frequency gain compensation for focus and tracking, and phase compensation near the gain intersection, then DA conversion A focus control signal is output to the drive circuit 36 via the device 35. The drive circuit 36 amplifies the control signal input from the DA converter 35 and outputs a signal to the actuator 9 to realize focus control. A tracking control signal is output to the drive circuit 38 via the DA converter 37. The drive circuit 38 amplifies the control signal input from the DA converter 37 and outputs a signal to the actuator 9 to realize tracking control.

  Next, the CD and SD discrimination methods including the laser control at the start-up according to the first to third embodiments of the present invention are shown in FIGS. Additional details will be described. FIG. 3 shows FE, AS, and RFENV when each laser light source 1 is turned on based on the sequence of the present invention at the time of starting the CD and the converging lens 10 is UP / DOWN in the focus direction by the actuator 9. FIG. 6 is a signal waveform diagram of drive signals in the focus direction of the actuator 9. FIG. 4 shows the FE, AS, when the laser light source 1 is turned on based on the sequence of the present invention at the start-up with the SD mounted, and the convergent lens 10 is UP / DOWN in the focus direction by the actuator 9. It is a signal waveform diagram of the driving signal in the focus direction of RFENV and actuator 9.

  A first embodiment will be described. As shown in FIGS. 3 and 4, the long wavelength 780 nm laser 1 has characteristics suitable for CD, and the short wavelength 650 nm laser 2 has characteristics suitable for high density SD. However, for example, if there is almost no difference between CD and SD in terms of external dimensions, it is unknown which laser may be emitted.

  In the first embodiment, as shown in FIG. 5, first, a signal is sent from the DSP 34 to the laser control circuit 3 to cause the long wavelength laser 1 to emit light (S1). Next, the convergent lens 10 is UP / DOWN (S2). At this time, if a CD or CD-R is installed in the apparatus, the S-shaped signal amplitude appearing on the FE is larger than a predetermined comparison value as shown in FIG. 3 (S3, S4). As a result, the DSP 34 detects that the loaded disk 12 is a CD or CD-R, drives the convergent lens 10 to the lowest point, and then UPs again (S5, S6) S appearing on the FE. The character signal level is detected (S7), focus filter calculation is started, a drive signal is output to the DA converter 35, and the focus control loop is closed (S8). Further, the tracking control loop is closed (S9), the address information on the disk 12 is read, (10) the search operation for moving the light beam to the desired track is performed, and the necessary information (reading the TOC information etc.) is set to the standby state. (S11).

  If no disk is loaded, no signal is output (S16), so it is determined as 'NODISK', the laser is turned off, and the disk is placed in a waiting state (S17).

  When the high-density SD is mounted, when long-wavelength light is emitted, the S-shaped signal amplitude appearing on the FE is smaller than a predetermined comparison value as shown in FIG. 4 (S4). As a result, the DSP 34 determines that the mounted disk 12 is not a CD or CD-R and drives the converging lens 10 to the lowest point. Then, the DSP 34 turns off the laser drive circuit 3 and turns on the laser drive circuit 4. , The 780 nm laser 1 is turned off (S12), and the 650 nm laser 2 is emitted (S13). When the converging lens 10 is UP / DOWN again in this state (S14), the level of the S-shaped signal appearing on the FE becomes larger than the predetermined value a (S15) (if it is smaller than the predetermined value a, it becomes S19 and S17). Upon detecting this, the DSP 34 determines that the loaded disc is SD (S18), and moves the converging lens 10 to the lowest point again. Then, UP is performed again (S20, S21), the level of the S-shaped signal appearing on the FE is detected (S22), the filter operation of the focus is started and the drive signal is output to the DA converter 35, and the focus control loop Is closed (S23). Further, the tracking control loop is closed (S24), the address information on the disk 12 is read (S25), the search operation for moving the light beam to the desired track is performed, and the necessary information (read the control track information etc.) is in the standby state. (S26). In addition, in order to cope with the variation in the reflectivity of the disk or the like, before detecting the amplitude level of the S-shaped signal, the S-shaped amplitude that appears when the convergent lens 10 is DOWN is measured, and the DSP 34 has a predetermined amplitude so that the amplitude becomes a predetermined amplitude. If the gain of the multiplier or attenuator (not shown) is switched, the focus control can be stably performed for both CD and SD, so that the startup time is not particularly prolonged.

  Next, a second embodiment will be described. Similar to the first embodiment, as shown in FIGS. 3 and 4, the long wavelength 780 nm laser 1 is suitable for CD, and the short wavelength 650 nm laser 2 is suitable for high density SD. Has characteristics. However, for example, if there is almost no difference between CD and SD in terms of external dimensions, it is unknown which laser may be emitted. Therefore, first, as shown in FIG. 6, a signal is sent from the DSP 34 to the laser control circuit 3 to cause the long wavelength laser 1 to emit light (S1). Next, the convergent lens 10 is UP / DOWN. At this time, if a CD or CD-R is attached to the apparatus, the U-shaped signal amplitude appearing on the AS is larger than a predetermined comparison value as shown in FIG. 3 (S2, S3). As a result, the DSP 34 determines that the mounted disk 12 is a CD or CD-R, drives the convergent lens 10 to the lowest point, and then UPs again (S5, S6) S appearing on the FE. The character signal level is detected (S7), focus filter calculation is started, a drive signal is output to the DA converter 35, and the focus control loop is closed (S8). Further, the tracking control loop is closed (S9), the address information on the disk 12 is read and a light beam is moved to a desired track, the necessary information (TOC information etc. is read (S10)), and the standby state is entered. Become.

  If no disk is loaded, no signal is output (S4), it is determined as 'NODISK', the laser is turned off, and the disk is waiting to be loaded (S16, S17).

  When the high-density SD is mounted, the U-shaped signal amplitude appearing on the AS is smaller than a predetermined comparison value as shown in FIG. 4 (S4). As a result, the DSP 34 determines that the mounted disk 12 is not a CD or CD-R, drives the focusing lens 10 to the lowest point, and then turns off the laser drive circuit 3 and turns on the laser drive circuit 4. A signal is transmitted, the 780 nm laser 1 is turned off (S12), and the 650 nm laser 2 is emitted (S13). When the converging lens 10 is UP / DOWN again in this state (S14), the level of the U-shaped signal appearing on the AS becomes larger than the predetermined value b (if it is smaller than the predetermined value b, it becomes S19 and S17). Detecting this (S15, S18), the DSP 34 determines that the loaded disk is SD, and moves the converging lens 10 to the lowest point again. Then, UP is performed again (S20, S21), the level of the S-shaped signal appearing on the FE is detected (S22), the filter operation of the focus is started and the drive signal is output to the DA converter 35, and the focus control loop Is closed (S23). Further, the tracking control loop is closed (S24), the address information on the disk 12 is read (S25), the search operation for moving the light beam to the desired track is performed, and the necessary information (read the control track information etc.) is in the standby state. (S26).

  In addition, in order to cope with variations in the reflectivity of a disk or the like, before detecting the amplitude level of the S-shaped signal on the FE, the U-shaped amplitude on the AS that appears when the convergent lens 10 is DOWN is measured, and the amplitude is a predetermined amplitude. The gain of the AS multiplier or attenuator (not shown) in the DSP 34 is switched so that the gain of the FE multiplier or attenuator (not shown) in the DSP is switched by that ratio. Thus, it is possible to stably carry out the focus control for both CD and SD, so that the startup time is not particularly prolonged.

  Next, a third embodiment will be described. Similar to the first and second embodiments, as shown in FIGS. 3 and 4, the long wavelength 780 nm laser 1 has characteristics suitable for CD, and the short wavelength 650 nm laser 2 has high density SD. It has characteristics suitable for. However, for example, if there is almost no difference between CD and SD in terms of external dimensions, it is unknown which laser may be emitted. Therefore, first, as shown in FIG. 7, a signal is sent from the DSP 34 to the laser control circuit 3 to cause the long wavelength laser 1 to emit light (S1). Next, the convergent lens 10 is UP / DOWN (S2). At this time, if a CD or CD-R is attached to the apparatus, the V-shaped signal amplitude appearing on RFENV is larger than a predetermined comparison value as shown in FIG. 3 (S3, S4). As a result, the DSP 34 determines that the mounted disk 12 is a CD or CD-R, drives the convergent lens 10 to the lowest point, and then UPs again (S5, S6) S appearing on the FE. The level of the character signal is detected or the peak level of the RFENV signal is detected to start the focus filter operation, and the drive signal is output to the DA converter 35, and the focus control loop is closed (S8). Further, the tracking control loop is closed (S9), the address information on the disk 12 is read (S10), the search operation for moving the light beam to the desired track is performed, and the necessary information (read TOC information etc.) is set to the standby state. (S11). If no disk is loaded, no signal is output. Therefore, it is determined as 'NODISK', the laser is turned off, and the disk is waiting to be loaded.

  When the high-density SD is mounted, since it appears on RFENV as shown in FIG. 4, the V-shaped signal amplitude is smaller than a predetermined comparison value (S4). As a result, the DSP 34 determines that the mounted disk 12 is not a CD or CD-R, drives the focusing lens 10 to the lowest point, and then turns off the laser drive circuit 3 and turns on the laser drive circuit 4. A signal is transmitted, the 780 nm laser 1 is turned off (S12), and the 650 nm laser 2 is emitted (S13). In this state, when the converging lens 10 is UP / DOWN again (S14), the level of the V-shaped signal appearing on RFENV becomes larger than a predetermined value c (S15) (if it is smaller than the predetermined value c, it becomes S19 and S17). Upon detecting this, the DSP 34 determines that the loaded disc is SD (S18), and moves the converging lens 10 to the lowest point again. Then, UP is performed again (S20, S21), the level of the S-shaped signal appearing on the FE or the peak level of the RFENV signal is detected (S22), the focus filter operation is started, and the drive signal is output to the DA converter 35. Then, the focus control loop is closed (S23). Further, the tracking control loop is closed (S24), the address information on the disk 12 is read (S25), the search operation for moving the light beam to the desired track is performed, and the necessary information (read the control track information etc.) is in the standby state. (S26).

  Further, in order to cope with the variation in the reflectivity of the disk or the like, before detecting the amplitude level of the S-shaped signal on the FE or the peak level of the RFENNV, the V-shaped amplitude on the RFENV that appears when the convergent lens 10 is DOWN is measured. The gain of the RFENV multiplier or attenuator (not shown) in the DSP 34 is switched so that the amplitude becomes a predetermined amplitude, and the gain of the FE multiplier or attenuator (not shown) in the DSP is further changed by the ratio. If configured to be switched, it is possible to stably carry out the focus control for both CD and SD, so that the startup time is not particularly prolonged.

  In the first to third embodiments, when a 650 nm laser is emitted by determining that it is not a CD or CD-R, the laser emission power is reduced to such an extent that the information on the CD-R does not disappear. If a predetermined pull-in level and gain corresponding to the light emission power are set, and it is determined that the CD-R is not a CD-R, and the setting is made so as to return to the specified power, the reliability is further improved.

  In addition, the measured values of the amplitude of FE measured in the first embodiment, the amplitude of AS measured in the second embodiment, and the amplitude of RFENV measured in the third embodiment are combined, respectively. The calculation may be performed so that a difference occurs depending on the type, and the initial setting value to be switched may be set not only by the laser but also by the disk based on the calculation result.

  Also, in the first to third embodiments, the invention was invented with two lasers taking a wavelength of 780 nm and a wavelength of 650 nm as an example, but the present invention is also applicable to lasers having three or more different wavelengths. It is possible to adapt by sequentially switching the procedure described above. Further, the present invention can be applied to a blue laser having a wavelength of 650 nm or 635 nm, and even shorter, and the present invention is not limited to the wavelength.

  Furthermore, when switching from a long wavelength laser to a short wavelength laser, if the focus control is kept operating, it can be very fast and the startup time is shortened. In particular, when the focus position is deviated by a certain amount due to a difference in substrate thickness or the like, stable switching can be achieved by adding or subtracting an offset to the focus control system immediately before switching.

  Furthermore, CDs such as CDs usually mounted on desktop PCs are usually mechanically clamped and loaded. Therefore, when the spindle is rotated without a disk, the spindle motor side turntable and the opposite clamper come into contact. May cause abnormal noise or damage.

  Therefore, as a fourth embodiment, in a state where the spindle motor is stopped, that is, in a state where the disk is not rotating, first, a signal is sent from the DSP 34 to the laser control circuit 3 to cause the long wavelength laser 1 to emit light. Next, the convergent lens 10 is UP / DOWN. At this time, if a CD or CD-R is installed in the apparatus, the S-shaped signal amplitude appearing on the FE and the U-shaped signal amplitude appearing on the AS are respectively predetermined values as shown in FIG. 3 even when the disk is stopped. Come bigger. Accordingly, the DSP 34 determines that the loaded disk 12 has a CD or a CD-R. When the level of each signal is smaller than a predetermined value, the DSP 34 drives the convergent lens 10 to the lowest point depending on whether the loaded disk 12 has an SD disk or no disk. After that, an OFF signal is sent to the laser drive circuit 3 and an ON signal is sent to the laser drive circuit 4, the 780 nm laser 1 is turned off, and the 650 nm laser 2 is emitted. When the converging lens 10 is UP / DOWN again in this state, when the S-shaped signal amplitude appearing on the FE and the U-shaped signal amplitude appearing on the AS are larger than the predetermined values, the DSP 34 has the disc mounted. It is determined that the disc is an SD type disc. If the level of each signal is smaller than the predetermined value, the DSP 34 enters a disk waiting state as “NO DISK” in which no disk is loaded.

  If it is determined that there is a disk, the spindle motor is further rotated, and the disk is discriminated again according to any of the first to third embodiments, thereby preventing damage to the spindle motor and the accuracy of the discrimination. Can be improved.

  As described above, in recent years, a wide variety of discs having the same external dimensions, such as next-generation high-density discs and recordable CDs, have been proposed and standardized. The fifth, sixth, and seventh embodiments are such specific disc type discriminating methods. With this, it is possible to record or reproduce various discs with one drive. FIG. 14 is a block diagram showing a configuration for realizing the fifth, sixth, and seventh embodiments. The fifth, sixth, and seventh embodiments are also shown in FIG. As in the fourth embodiment, the present invention can be realized by a program of the microcomputer 51 that controls the DSP 34 and the entire apparatus. FIG. 15 is similar to FIGS. 3 and 4, in addition to CD and single-layer SD having a higher density than CD, two-layer SD-W having a larger capacity and CD-RW which is a recordable CD. On the other hand, it is a wave form diagram which shows the waveform of FE, AS, and RF when 780 nm and a laser of 650 nm are each emitted and irradiated. Next, description will be made with reference to FIGS. 14 and 15.

  A fifth embodiment will be described. For example, if the apparatus of the fifth embodiment can reproduce four types of discs such as conventional CD, SD, SD-W, and CD-RW, first a signal is sent from the DSP 34 to the laser control circuit 3, The long wavelength laser 1 is caused to emit light. Next, the convergent lens 10 is UP / DOWN. At this time, if a disk is mounted on the apparatus, the S-shaped signal amplitude appearing on the FE varies as shown in FIG. The amplitude value (MAX, MIN value) of the FE signal is taken into the DSP 34 by the AD converter 33, and the value is output to the microcomputer (CPU) 51 via the bus, and the output amplitude value of the FE is obtained. The CPU 51 stores in a built-in RAM. In the case of normal CD and CD-R, it is possible to discriminate only by the amplitude value of FE in this long wavelength laser, and after continuously driving the focusing lens 10 to the lowest point, the level of the S-shaped signal appearing on the FE after being UP again. Or the peak level of the RFENV signal is detected to start focus filter calculation, and a drive signal is output to the DA converter 35 to close the focus control loop. Further, the tracking control loop is closed, the address information on the disk 12 is read, a search operation for moving the light beam to a desired track is performed, and necessary information (reading the TOC information and the like) is set to the standby state.

  In the case of CDs other than CD, a signal is sent from the DSP 34 to the laser control circuit 4 to cause the short wavelength laser 2 to emit light. Next, the convergent lens 10 is UP / DOWN. As shown in FIG. 15, the S-shaped signal amplitude appearing on the FE is different for each disk. Further, it differs from the amplitude of the FE signal obtained when the long wavelength laser 780 nm is irradiated. As in the case of the 780 nm laser, this FE signal amplitude (MAX, MIN value) is taken into the DSP 34 by the AD converter 33, and the value is outputted to the microcomputer (CPU) 51 via the bus. The CPU 51 stores the amplitude value of the fed FE in the built-in RAM.

  The CPU 51 subtracts the stored FE value at each wavelength, for example (subtraction is basically desirable for ease of processing, but the present invention is not limited thereto), and the subtraction result is used as a predetermined discrimination value. In comparison, it is possible to specify whether the type of the currently loaded disc is SD, SD-W, or CD-RW.

  FIG. 16 shows the amplitude value of each signal obtained when the laser is irradiated with 780 nm and 650 nm lasers and the lens is UP / DOWN in FIG. As shown in FIGS. 15 and 16A, in the case of SD (single layer), the amplitude value of FE at 780 nm is stored as SFE78, and the amplitude value at 650 nm is stored as SFE65. Each amplitude value is subtracted and compared with predetermined levels of FA and FB, and if it falls within the range, it can be discriminated as SD (one layer). In the case of SD-W (two layers), the amplitude value of FE at 780 nm is stored as DFE78, and the amplitude value at 650 nm is stored as DFE65. Each amplitude value is subtracted and compared with a predetermined level of FB and FC, and if it falls within the range, it can be determined as SD-W (two layers). Further, in the case of CD-RW, the amplitude value of FE at 780 nm is stored as WFE78, and the amplitude value at 650 nm is stored as WFE65. Each amplitude value is subtracted and compared with a predetermined level of FC, and if it is smaller than that value, it can be determined as CD-RW.

  Next, a sixth embodiment will be described. In the sixth embodiment, it is assumed that an apparatus similar to the fifth embodiment can reproduce four types of discs such as conventional CD, SD, SD-W, and CD-RW. First, a signal is sent from the DSP 34 to the laser control circuit 3 to cause the long wavelength laser 1 to emit light. Next, the convergent lens 10 is UP / DOWN. At this time, if a disk is mounted on the apparatus, the U-shaped signal amplitude appearing on the AS varies as shown in FIG. The amplitude value (MAX or MIN value) of the AS signal is taken into the DSP 34 by the AD converter 33, and the value is output to the microcomputer (CPU) 51 via the bus, and the output AS amplitude value is obtained. The CPU 51 stores in a built-in RAM. In the case of normal CD and CD-R, it is possible to discriminate only by the amplitude value of AS in this long wavelength laser. Subsequently, after driving the converging lens 10 to the lowest point, the UP of the S-shaped signal appearing on the FE is displayed again. When the level is detected or the peak level of the RFENV signal is detected, focus filter calculation is started and a drive signal is output to the DA converter 35 to close the focus control loop. Further, the tracking control loop is closed, the address information on the disk 12 is read, a search operation for moving the light beam to a desired track is performed, and necessary information (reading the TOC information and the like) is set to the standby state. Next, in the case of CDs other than CD, a signal is sent from the DSP 34 to the laser control circuit 4 to cause the short wavelength laser 2 to emit light. Next, the convergent lens 10 is UP / DOWN. As shown in FIG. 15, the U-shaped signal amplitude appearing on the AS is different for each disk. Furthermore, the amplitude of the AS signal obtained when the long wavelength laser 780 nm is irradiated is also different. As in the case of the 780 nm laser, this AS signal amplitude (MAX or MIN value) is taken into the DSP 34 by the AD converter 33 and the value is output to the microcomputer (CPU) 51 via the bus. The CPU 51 stores the AS amplitude value thus obtained in the built-in RAM.

  The CPU 51 subtracts the AS value at each stored wavelength, for example (subtraction is basically desirable for ease of processing, but the present invention is not limited thereto), and the subtraction result is used as a predetermined discriminant value. In comparison, it is possible to specify whether the type of the currently loaded disc is SD, SD-W, or CD-RW.

  FIG. 16 shows the amplitude value of each signal and the discriminant value obtained when the lenses are irradiated with 780 nm and 650 nm lasers in FIG. 15 and the lens is UP / DOWN as described above. Is. As shown in FIGS. 15 and 16B, in the case of SD (single layer), the AS amplitude value at 780 nm is stored as SAS 78, and the amplitude value at 650 nm is stored as SAS 65. Each amplitude value is subtracted and compared with predetermined levels of AA and AB, and if it falls within the range, it can be determined as SD (1 layer). In the case of SD-W (two layers), the AS amplitude value at 780 nm is stored as DAS 78, and the amplitude value at 650 nm is stored as DAS 65. Each amplitude value is subtracted and compared with predetermined levels of AB and AC, and if it falls within that range, it can be determined as SD-W (two layers). In the case of CD-RW, the AS amplitude value at 780 nm is stored as WAS78, and the amplitude value at 650 nm is stored as WAS65. Each amplitude value is subtracted and compared with a predetermined level of AC, and if it is smaller than that value, it can be determined as CD-RW.

  Next, a seventh embodiment will be described. In the seventh embodiment, as in the fifth and sixth embodiments, it is assumed that the apparatus can reproduce four types of discs such as conventional CD, SD, SD-W, and CD-RW. First, a signal is sent from the DSP 34 to the laser control circuit 3 to cause the long wavelength laser 1 to emit light. Next, the convergent lens 10 is UP / DOWN. At this time, if a disk is mounted on the apparatus, RF appears as shown in FIG. 15, but this envelope detection circuit 29 is provided via an envelope detection circuit 29 provided to facilitate detection of this amplitude. The amplitude of the V-shaped signal appearing on the output RFENV is different for each disk. The amplitude value (MAX or MIN value) of the RFENV signal is taken into the DSP 34 by the AD converter 33, and the value is output to the microcomputer (CPU) 51 via a bus. The amplitude value of the output RFENV is obtained. The CPU 51 stores in a built-in RAM. In the case of normal CD and CD-R, it is possible to discriminate only by the amplitude value of the RFENV signal in this long wavelength laser, and after continuously driving the focusing lens 10 to the lowest point, the S-shaped signal appearing on the FE after being UP again. When the level is detected or the peak level of the RFENV signal is detected, focus filter calculation is started and a drive signal is output to the DA converter 35 to close the focus control loop. Further, the tracking control loop is closed, the address information on the disk 12 is read, a search operation for moving the light beam to a desired track is performed, and necessary information (reading the TOC information and the like) is set to the standby state. Next, in the case of CDs other than CD, a signal is sent from the DSP 34 to the laser control circuit 4 to cause the short wavelength laser 2 to emit light. Next, the convergent lens 10 is UP / DOWN. As shown in FIG. 15, the V-shaped signal amplitude appearing on RFENV is different for each disk. Further, the amplitude of the RFENV signal obtained when the long wavelength laser 780 nm is irradiated is also different. As in the case of the 780 nm laser, the RFENV signal amplitude (MAX or MIN value) is taken into the DSP 34 by the AD converter 33, and the value is output to the microcomputer (CPU) 51 via the bus. The CPU 51 stores the amplitude value of the RFENV thus obtained in the built-in RAM.

  The CPU 51 subtracts the RFENV value at each stored wavelength, for example (subtraction is basically desirable for ease of processing, but this embodiment is not limited by the contents of the calculation), and the subtraction result is obtained. Compared with a predetermined discriminant value, it is possible to specify whether the type of the currently loaded disc is SD, SD-W, or CD-RW.

  FIG. 16 shows the amplitude value of each signal obtained when the laser is irradiated with 780 nm and 650 nm lasers and the lens is UP / DOWN in FIG. As shown in FIGS. 15 and 16 (3), in the case of SD (single layer), the RFENV amplitude value at 780 nm is stored as SRF78, and the amplitude value at 650 nm is stored as SRF65. Each amplitude value is subtracted and compared with predetermined levels of RA and RB. If it falls within the range, it can be determined as SD (one layer). In the case of SD-W (two layers), the RFENV amplitude value at 780 nm is stored as DRF78, and the amplitude value at 650 nm is stored as DRF65. Each amplitude value is subtracted and compared with a predetermined level of RB and RC, and if it falls within the range, it can be determined as SD-W (two layers). Further, in the case of CD-RW, the amplitude value of RFENV at 780 nm is stored as WRF78, and the amplitude value at 650 nm is stored as WRF65. Each amplitude value is subtracted and compared with a predetermined level of RC, and if it is smaller than that value, it can be determined as CD-RW.

  Further, by combining the fifth, sixth, and seventh embodiments, it is possible to improve the accuracy of discrimination, to cope with various optical heads, and to discriminate various types of disks. For example, the DSP 34 is configured to detect the amplitudes of the signals FE, AS, RFENV and TE obtained from the disk, and the CPU stores all of its amplitude values for each wavelength laser. Divide FE, RFENV, and TE for long wavelength laser emission by AS for short wavelength laser emission, and FE, RVENV, TE for short wavelength laser emission and AS for long wavelength laser emission. By comparing or subtracting each value and discriminating the disc type according to the result, it is possible to accurately discriminate even when the disc reflectivity fluctuates due to dirt and dust. Become.

  Further, in a read-only disk (ROM) in which a track is formed by a pit row and a recordable disk (RAM) in which a track is formed by a guide groove or wobble signal, the amplitude of a track deviation signal (TEpp) detected by push-pull, Since the amplitude and S / N of the track deviation signal (TEph) detected by the S / N and phase difference are different, the focus control is activated to detect the amplitude of each TE and the pulse width of noise when binarized. Thus, the ROM disk and the RAM disk may be discriminated according to the detected value. Further, it may be determined by the magnitude of a crossing signal (groove crossing signal) that appears on the FE when the light beam crosses the track.

  Also, under conditions that prevent CD-R from being erased (disk rotation stops, laser power, wavelength, etc.), both CD and CD-R lasers emit and emit both long and short wavelengths. Then, it is also possible to take a signal at each wavelength of all the discs and discriminate them collectively.

  In the above-described embodiment, the case of performing playback on a CD (CD-R), SD, SD-W, and CD-RW disc has been described. For example, the current PD, MO, MD, and the future Appropriately applied to devices that play two or more types of the above-mentioned discs by mounting two or more lasers with different wavelengths on all discs such as DVD and high-density MO that will be on the market. It is possible to specify a light source having a suitable wavelength while protecting the disk.

  As in the first to third and fourth embodiments, in the fifth, sixth, and seventh embodiments, two lasers have been described by taking a wavelength of 780 nm and a wavelength of 650 nm as an example. The invention can also be applied to two or more lasers having different wavelengths by sequentially switching the above-described procedures. Further, the present invention can be applied to a blue laser having a wavelength of 650 nm or 635 nm, and even shorter, and the present invention is not limited to the wavelength.

  Further, in the above description, the signal amplitude value is stored in the CPU built-in RAM. However, when the DSP capacity and RAM capacity are sufficient, the signal may be stored in the DSP built-in RAM. . If there is a large amount of data to be stored, an external RAM accessible from the DSP or CPU may be provided.

  Next, an activation procedure characterized by the pull-in timings of focus control and tracking control, which are the eighth and ninth embodiments, will be described with reference to FIGS. FIG. 8 shows open loop gain characteristics and disc surface deflection acceleration characteristics for focus control, and FIG. 9 shows open loop gain characteristics and eccentric acceleration characteristics for discs.

  As represented by CD, the playback speed is increased, so-called disk rotation speed increases, so the time for the spindle motor to reach the desired rotation speed at startup is longer. Conversely, when the rotation speed increases, it is proportional to the square of the rotation speed. As a result, the disc surface deflection and eccentric acceleration increase. As shown in FIGS. 8 and 9, when the acceleration of the disk exceeds the open loop gain of the servo, there is a problem that the focus control and tracking control are difficult to be pulled.

  FIG. 10 shows the startup procedure of the apparatus showing the eighth embodiment. This will be described. When a disk is loaded in the apparatus, a startup process is performed by a system control microcomputer (not shown), and a spindle motor ON command is first sent from the microcomputer to the DSP 34. When the DSP 34 receives a spindle motor ON command from the microcomputer, the DSP 34 outputs an ON signal from a predetermined port and activates the spindle motor 13 via the spindle control circuit 14 (S1). After the command is sent, the DSP 34 controls the speed so as to reach a predetermined rotational speed by looking at the FG from the spindle motor 13 (S2). The time required to reach the predetermined rotation is 500 ms to 1500 ms. During this time, the microcomputer sends commands to the DSP 34 one after another. In response to the command, the DSP 34 performs laser ON (S2, S4), focus control ON (S5, S6, S7), and tracking control ON (S8, S9, S10, S11, S12). Since the laser ON time is several milliseconds, the spindle motor has not yet reached the predetermined number of rotations at the time when the focus starts to be pulled in, and the focus control is immediately pulled in at this timing (S5). Subsequently, the tracking control is turned on, but the time for drawing the focus control is about 200 ms to 500 ms, and the spindle motor is still in a state lower than the predetermined rotation speed even at the start time of the tracking control drawing.

  Therefore, the eccentric acceleration and surface deflection acceleration of the disk are within or close to the tracking range of the open loop gain of each control, and there is almost no failure in pulling. In particular, when the start-up time of the spindle motor is remarkably fast, the time from a certain number of rotations to a certain number of rotations is measured, and learning for switching the drive gain according to the time is performed (this is the ninth embodiment, The focus control and tracking control may be pulled in at a predetermined number of rotations during the learning process (to be described in detail later).

  FIG. 11 shows an activation procedure of the apparatus showing the ninth embodiment. This will be described. When a disk is loaded in the apparatus, a startup process is performed by a system control microcomputer (not shown), and a spindle motor ON command is first sent from the microcomputer to the DSP 34. When the DSP 34 receives a spindle motor ON command from the microcomputer, the DSP 34 outputs an ON signal from a predetermined port and activates the spindle motor 13 via the spindle control circuit 14 (S13). After sending the command, the DSP 34 controls the speed so as to reach a predetermined rotational speed by looking at the FG coming from the spindle motor 13 (S2). After the motor reaches a predetermined number of revolutions, the DSP 34 turns on laser (S3, S4, S5), focus control ON (S6, S7, S8), and tracking control ON (S9, S10, S11) according to the command. Do. At this time, the disk with small eccentricity and surface deflection is brought into the standby state by pulling in the focus control and tracking control without any problem, searching for a desired track on the disk and reading necessary information (S12, S13). However, if the surface shake and the eccentricity are large, the focus or tracking control cannot be drawn if the acceleration is large. Therefore, when the DSP 34 detects a pull error in the focus control or tracking control (S8, S11), the DSP 34 resets the target rotational speed output to the spindle motor to a low value (for example, 1/2) (S13, S14). Here, there are various methods for detecting a focus or tracking pull-in error. For example, a focus pull-in error is generally detected when the RFENV signal is smaller than a predetermined level or when there is no track deviation signal. In general, a tracking pull-in error is detected by counting a binarized signal of a track deviation signal and obtaining a count value greater than a predetermined value.

  Based on the above signal, the DSP 34 detects a focus / tracking pull-in error, sets the target rotational speed to a low value, and after the rotational speed has decreased, the focusing lens 10 is UP / DOWN again to pull in the focus control. Perform a pull-in. For example, if the rotational speed is halved, the surface deflection and the acceleration of eccentricity become 1/4, and the control can be pulled in even if the surface deflection and eccentricity are relatively large. After the tracking is pulled in, a desired track is searched, the required number of revolutions is read while being controlled in a predetermined manner, and necessary information is read, and a standby state is set (S13).

  Next, a tenth embodiment of the present invention will be described. FIG. 12 is a characteristic diagram showing the variation in the starting torque of the motor and the starting time up to a certain rotational speed.

  As shown in FIG. 12, the start-up time differs depending on the torque variation of the motor. Further, the torque variation becomes the gain variation of the rotation control system, and the rotational speed fluctuates due to the disturbance or the like, resulting in the jitter of the reproduction signal. . Therefore, the tenth embodiment is a learning method for absorbing variations in the rotating system. FIG. 13 is a block diagram showing the spindle motor 13, the spindle control circuit 14, and the DSP 34 in FIG. 1 in more detail.

  When a disk rotation command is sent from the CPU (not shown) to the DSP 34 when the apparatus is activated, the DSP 34 sends a rotation command to the spindle motor 13 via the spindle control circuit 14. The spindle motor is provided with a hall element, which generates an FG signal of one revolution N pulses (6 pulses in the present embodiment) and inputs it to the DSP 34. The DSP 34 detects and determines whether the motor is stopped or rotating when the FG signal is input and the period falls within a predetermined time.

  Further, the DSP 34 calculates and sets the target cycle (target frequency) of the FG with respect to the target predetermined rotational speed designated by the CPU, and sends the drive signal to the spindle control circuit so that the FG that comes in becomes the cycle (frequency). 14 to the spindle motor. The spindle control circuit 14 has a gain variable unit 41, and a predetermined gain is initially set.

  A method of learning the torque fluctuation of the spindle motor will be described. As described above, when the driving torque of the motor and the gain of the control circuit vary, the time required to reach a certain rotational frequency varies. Since FG is input to the DSP 34 and one period is constantly measured for frequency control, the current rotational speed can be detected in the period. Therefore, for example, the arrival time from 0 rotation (stop state) to 500 rotations is measured. The gain set in the gain variable section 41 corresponding to the measurement time can be obtained by storing it as a table value on the ROM in the DSP 34 or referring to it, or by obtaining a relational expression and executing the calculation in the core. Set in the upper gain setting RAM.

  By setting the set value obtained according to the start time of the spindle motor as described above in the gain variable section 41, a stable rotation control system that absorbs the influence of the spindle motor torque variation, backlash, friction, etc. can be obtained. Can be built.

  In the description of the embodiment, it has been described that the arrival time from 0 to 500 rotations is measured. In this case, the spindle motor is subjected to inertial force immediately after the power is turned OFF / ON or reset during operation of the apparatus. Therefore, if it waits for 0 rotation, that is, the rotation stops, it takes time to retry. Therefore, if it is configured to measure the change time between two rotation speeds where the rotation increases, for example, from 300 rotations to 500 rotations, there is no waiting time even when the power is turned OFF / ON, and it is accurate. In addition, spindle start-up (rotational change) times A, B, and C can be measured. Further, if two rotation speeds to be learned are set according to the reproduction speed of a CD or the like, accurate torque learning can be performed and more stable rotation control can be constructed. In particular, if the number of rotations at two points is set to a rotation number related to about twice, software processing is simplified and accurate measurement is possible.

  Also, when there are various playback speed modes such as 8 cm (single), 12 cm, standard speed, 2 times speed, and 8 times speed with a single device, such as a CD, etc., for each disc type (diameter) or playback speed. If learning is performed, the rotation control system becomes more stable.

  According to the first to seventh embodiments described above, it is possible to reproduce or record a new high-density disc while protecting information already recorded like a CD-R. In addition, it is possible to start in a standby mode where it is possible to immediately discriminate which disk is mounted at the time of startup and to reproduce (record). Even in the case of a disk with large surface deflection and eccentricity according to the eighth embodiment, high speed start-up and high speed reproduction can be realized by pulling in the focus and tracking system while the rotational speed does not increase immediately after start-up. . Similarly, in the ninth embodiment, when the pull-in of the control fails in a disk with a large amount of run-off, the pull-in is performed by lowering the rotational speed, and after the pull-in, the rotational speed is returned to the predetermined rotational speed. High-speed playback can be realized with certainty. In addition, it is possible to realize accurate motor learning without increasing the cost by measuring the torque fluctuation and variation of the motor by using the FG used for speed control to measure the transition time to two rotational speeds. A stable rotation control system can be constructed.

  Further, the disc presence / absence determination described in the fourth embodiment can be performed by measuring the rise time of the motor and using the measured value. When there is no regular disk, the inertia is small, so it is possible to reach a predetermined rotation at a high speed or to run out of control and lock. Therefore, if the motor rise time does not fall within the predetermined range, it can be determined that no disc is loaded. By determining the presence / absence of a disk in this way, two processes such as starting the motor and determining the presence / absence of a disk can be executed in parallel. Therefore, it is possible to shorten the activation time.

  As is apparent from the above description, the present invention determines whether a loaded disk is a high-density disk or an ultra-high-density disk by irradiating a laser without applying focus control and tracking control means. Therefore, the converged light beam hits the recording surface for an extremely short time (several ms or less), and even if one of the information marks is lost, it is possible to sufficiently correct the error, thereby reproducing the information. There is no problem with this.

  In addition, the present invention discriminates the type of the disk while irradiating in order from the laser having the longer wavelength to the shorter one, thereby allowing the short wavelength to be recorded on a recordable medium (such as a CD-R) that absorbs the short wavelength laser. There is no irradiation. As a result, it is possible to reproduce a CD, which has been impossible with a single short wavelength laser, and to prevent the loss of information on a recordable disc such as a CD-R by the short wavelength laser.

  Further, according to the present invention, in a device having a large reproduction power (such as a reproduction compatible machine such as a CD-RW), it is possible to make an erroneous determination by adopting a configuration in which the laser power is emitted at the time of the determination. Thus, even if the CD-R or the like is irradiated with a short wavelength laser, the loss of information can be completely prevented.

  Further, the present invention can realize high-speed playback even on a disk with large surface deflection and eccentricity.

  Furthermore, the present invention measures the torque fluctuations and variations of the motor by using the FG used for speed control to measure the transition time to two rotational speeds, so that accurate motor learning can be achieved without increasing costs. And a stable rotation control system can be constructed.

  Therefore, as a whole, the present invention can reliably realize high-speed reproduction of conventional CDs and CD-Rs, and can also reproduce or record new high-density discs with high reliability.

  The digital signal processor according to the present invention can realize high-speed reproduction of a conventional CD and CD-R with high reliability, and can also reproduce or record a new high-density disk with high reliability. For example, it is useful as an optical disk device or the like.

It is a block diagram for demonstrating the structure of one embodiment of this invention. It is the block diagram which showed in detail the part of the photodetector among the structures of one embodiment of this invention. FIG. 6 is a waveform diagram showing in detail each part at the time of focus pull-in when a conventional CD is mounted in an embodiment of the present invention. FIG. 5 is a waveform diagram showing in detail each part at the time of focus pull-in when a new high-density disk is mounted in an embodiment of the present invention. It is a flowchart which shows the starting procedure of the 1st Embodiment of this invention. It is a flowchart which shows the starting procedure of the 2nd Embodiment of this invention. It is a flowchart which shows the starting procedure of the 3rd Embodiment of this invention. FIG. 6 is an open loop frequency characteristic diagram of disc surface deflection acceleration and focus control. It is an open loop frequency characteristic diagram of the eccentric acceleration of the disk and focus control. It is a flowchart which shows the starting procedure of the 4th Embodiment of this invention. It is a flowchart which shows the starting procedure of the 5th Embodiment of this invention. It is the characteristic view which showed the relationship between the torque variation of a spindle motor, and starting time. FIG. 10 is a detailed block diagram of a spindle motor control portion of FIG. 1 for explaining a sixth embodiment of the present invention. It is a block diagram for demonstrating the structure of the optical disk device for demonstrating the 5th-7th embodiment of this invention. FIG. 6 is a waveform diagram of signals obtained by convergent irradiation of lasers of respective wavelengths when a conventional CD and a new high-density disk are mounted on an embodiment of the optical disk apparatus of the present invention. In one embodiment of the optical disk apparatus of the present invention, when a conventional CD and a new high-density disk are loaded, the stored value in the RAM of each signal obtained by convergent irradiation of the laser of each wavelength and its discrimination level are shown. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 780 nm laser 2 650 nm laser 3 Laser control circuit 4 Laser control circuit 5 Coupling lens 6 Coupling lens 7 Wavelength-dependent polarizing element 8 Polarizing beam splitter 9 Actuator 10 Converging lens 11 Light beam 12 Disc 13 Spindle motor 14 Spindle control circuit 15 Photodetector 20 Current-voltage conversion amplifier 21 Adder 22 Comparator 23 Phase comparator 24 Low-pass filter 25 Adder 26 Adder 27 Differential amplifier 28 Low-pass filter 29 Envelope detection circuit 30 AD converter 31 AD converter 32 AD converter 33 AD converter 34 Digital signal processor (DSP)
35 DA converter 36 Drive circuit 37 DA converter 38 Drive circuit 41 Gain converter 42 Hall element 43 Comparator

Claims (4)

After performing a digital filter operation by adding, delaying, and multiplying with a focus error signal that changes according to the distance between the optical disc and the focal point of the converging lens as input, performing low-frequency gain compensation and phase compensation near the gain intersection, A digital signal processor having a function of feeding back a control signal to the focus moving means,
Emitting a long wavelength laser; and
Moving the converging lens in a focus control direction;
Comparing the amplitude of the focus error signal with a predetermined value;
Closing the loop in which the feedback is performed if the amplitude of the focus error signal is greater than a predetermined value;
When the amplitude of the focus error signal is smaller than a predetermined value,
Emitting a short wavelength laser;
Moving the converging lens in a focus control direction;
A digital signal processor with an algorithm that includes   The digital signal processor according to claim 1, wherein if a focus error signal is not detected when the short-wavelength laser is emitted, a step of turning off the laser is executed.   The digital signal processor according to claim 1, wherein the step of emitting the long wavelength or short wavelength laser is executed before issuing a command to rotate the optical disk.   2. The digital signal processor according to claim 1, wherein after issuing a command to rotate the optical disk, a process of feeding back the digital filter calculation result to the focus moving unit is executed before the optical disk reaches a predetermined number of rotations.

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