KR20070070045A - Compatible optical information recording and reproducing apparatus - Google Patents

Abstract

A compatible optical information recording/reproducing device is provided to conduct symmetry compensation or slice level compensation of an RF(Radio Frequency) signal extracted from a DVD(Digital Versatile Disk)-ROM(Read Only Memory) disk by using a blue LD(Laser Diode), thus the signal is properly reproduced. A blue LD irradiates a laser beam of 405nm central wavelength on the first and second optical disks. An objective lens(16) focuses the beam irradiated from the blue LD on the first and second optical disks. A symmetry compensator(6a) compensates a reproduction signal(RF signal) when information on the second optical disk is reproduced.

Description

Compatible optical information recording and reproducing apparatus

1 and 2 are block diagrams and schematic diagrams each showing a reproduction unit of the optical information recording and reproducing apparatus according to the first embodiment of the present invention.

3 is a block diagram showing an optical information recording and reproducing apparatus according to a comparative example.

4 is a schematic diagram showing a reproduction unit of the optical information recording and reproducing apparatus of the comparative example.

5A and 5B are schematic diagrams showing waveforms of an RF signal obtained from an optical information recording and reproducing apparatus according to an embodiment of the present invention, in which FIG. 5A is a waveform of an RF signal before symmetry correction, and FIG. The waveform of the RF signal.

6 is an eye pattern representing an RF signal obtained by reproducing a DVD-ROM disk using a red laser having a center wavelength of 650 nm in the optical information recording and reproducing apparatus according to the comparative example of FIGS. 3 and 4. It is a case where the equalizer EQ for red laser diode LD is not used, and FIG. 6B is a case where EQ for red LD is used.

FIG. 7 is an eye pattern representing an RF signal obtained by reproducing a DVD-ROM disc using a blue LD having a center wavelength of 405 nm in the optical information recording and reproducing apparatus of the comparative example of FIGS. 3 and 4, and FIG. 7A is an EQ for red LD. Is not used, and FIG. 7B is a case where the red LD EQ is used.

8 is an eye pattern showing an RF signal reproduced from a DVD-ROM disc by the optical information recording and reproducing apparatus according to the embodiment of the present invention of FIGS. 1 and 2;

9 is a block diagram showing a reproduction unit of the optical information recording and reproducing apparatus according to the second embodiment of the present invention.

Fig. 10 is a block diagram showing a playback unit of the optical information recording and reproducing apparatus according to the third embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1 ... AD converter 3 ... Peak detection circuit

5.Mean value detecting circuit 6a, 6b ...

7 ... Symmetry correction circuit 10a ... Blue LD

10b ... red LD 11 ... dichroic prism

16.Objective lens 18.Optical disk

19 ... Opening limiter 30 ... Operator

32 ... LPF 34 ... VCA circuit

36 ... Equalizer (EQ) Circuit 37a ... EQ for Blue LD

37b ... Equal 39 for red LD 39 ... slice circuit

40 ... PLL circuit 41 ... Synchronous detection circuit

42 ... EFM circuit 44 ... Disc discrimination circuit

54a ... CW drive circuit for blue LD 54b ... CW drive circuit for red LD

56a ... APC circuit for blue LD 56b ... APC circuit for red LD

58 ... slice level compensation circuit 60 ... opening limit control circuit

The present invention relates to a compatible optical information recording and reproducing apparatus, and more particularly to a compatible optical information recording and reproducing apparatus which is compatible with an optical system reproduced by a blue laser and a DVD optical system reproduced by a red laser.

In general, an optical information recording and reproducing apparatus having compatibility between a DVD (Digital Versatile Disc) and a compact disc (CD) is widely used.

Furthermore, a next generation DVD using a blue semiconductor laser has been developed as a large capacity optical information recording and reproducing apparatus. In this case, there is a strong demand for an optical information recording and reproducing apparatus compatible with a conventional DVD or CD.

Next-generation DVD optical information recording and reproducing apparatus has a blue semiconductor laser having a center wavelength of about 405 nm and an objective lens having a high number of apertures (for example, 0.6 to 0.85) to realize a recording capacity of 15 gigabyte or more on a single-layer basis. There is a need for an optical system and an image encoding method for reducing the size of a semiconductor laser spot formed on a DVD using OL.

The above-mentioned optical system is complicated to share the objective lens and to ensure compatibility with an optical disc such as a DVD-ROM disc (Read Only Memory) or a CD-ROM while recording and reproducing the next generation DVD. That is, a beam splitter for converting the optical path by numerical aperture limitation, aberration correction, reflection and / or transmission of semiconductor laser light having a different wavelength is required. Since the amount of light decreases each time it passes through these optical component elements, the more complicated the optical system, the smaller the light reaching the optical disk and then reflected and incident on the photodetector for reproduction.

In the semiconductor laser corresponding to the optical disc standard for reproduction only, since the recording on the optical disc is not necessary, only the optical output of the level necessary for reproduction is required. In this case, the attenuation of the light due to the optical components arranged in order to ensure compatibility with the next-generation DVD is large, and there is a case where the light output of the above-described reproduction-only semiconductor laser is insufficient. On the other hand, it is possible to design an optical pickup device using a high power semiconductor laser, but this causes a problem of an increase in cost.

In a compatible optical information reproducing apparatus for playing next-generation DVDs and DVD-ROM discs, in order to reduce the cost of the optical pickup device, for example, the blue semiconductor laser (LD) and the numerical aperture (NA) are 0.60. When a DVD-ROM disc is played back using a high-number objective lens, a good RF signal cannot be obtained properly as shown in FIG. 5A even when a radio frequency (RF) signal is corrected with a standard equalizer. In addition, even when the rotation control is performed in this state, since correct synchronization control cannot be performed, a problem arises in that a good demodulation signal cannot be obtained.

In contrast, Japanese Patent Laid-Open No. 2002-109764 discloses a technique for reproducing a DVD-ROM disc by changing a tracking error (TE) polarity.

However, even when the tracking error (TE) polarity is changed and reproduced, good reproduction characteristics may not be obtained in some cases.

Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a compatible optical information recording and reproducing apparatus having compatibility with next-generation DVDs.

In order to achieve the above object, a compatible optical information recording and reproducing apparatus according to the present invention has a cover layer thickness of 0.1 or 0.6 mm and a recording of a first optical disk optimized for recording and reproduction with laser light having a center wavelength of 405 nm. And reproducing, and the reproducing can be performed on the second optical disc in which the cover layer thickness is 0.6 mm and the center wavelength is 650 nm, and the recording and reproducing are optimized.

A blue laser diode (LD) for irradiating laser light having a center wavelength of 405 nm to the first and second optical disks; An objective lens for focusing light irradiated from the blue LD onto the first and second optical disks; And geometry correction means for correcting a reproduction signal (RF signal) when the information on the second optical disc is reproduced.

An opening limiting element disposed between the blue LD and the objective lens, the opening limiting element selectively limiting the opening according to a wavelength with respect to the laser light irradiated to the first or second optical disk; And an opening limit control circuit for controlling the opening limiting element. Therefore, when recording and reproducing optical information are made to be compatible with the first optical disc and the second optical disc having a cover layer thickness of 0.6 mm, the numerical aperture of the objective lens is optimized to record and reproduce the first optical disc. The numerical aperture of the objective lens is used for controlling the aperture limiting element and for recording and reproducing optical information by making the first optical disc and the second optical disc having a thickness of 0.1 mm of cover layer compatible. The aperture limiting element is controlled to be optimized for regeneration. When the cover layer thicknesses of the first and second optical discs are different, the numerical aperture of the objective lens is optimized for recording and reproduction of the second optical disc based on the result of the type discrimination of the first and second optical discs.

In addition, the geometry correction means according to the present invention includes an analog-to-digital converter for converting the input analog signal into a digital signal; A peak detection circuit for detecting a peak value of the converted digital signal; And an average value detection circuit for calculating an average value from the detected peak values.

In addition, the geometry correction means may further include a geometry correction circuit for correcting the geometry from the average value calculated by the average value detection circuit.

In addition, the geometry correction means may further include a slice level correction circuit for correcting the RF signal is disordered by calculating the average value calculated by the average value detection circuit instead of the geometry correction circuit.

Hereinafter, a compatible optical information recording and reproducing apparatus according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same component, and description of a detailed description is abbreviate | omitted.

1 and 2 are block diagrams and schematic diagrams each showing a reproduction unit of the optical information recording and reproducing apparatus according to the first embodiment of the present invention.

In the optical information recording and reproducing apparatus according to the present embodiment, a blue laser diode (hereinafter referred to as LD) 10a for irradiating a blue laser light to a DVD-ROM disk and a laser irradiated from the blue LD 10a. The objective lens 16 having a numerical aperture NA of approximately 0.65 for focusing light to form an optical spot on a DVD-ROM disc, and a geometry for correcting a reproduction signal (a radio frequency signal; hereinafter referred to as an RF signal) ( symmetry) correction means 6a. The geometry correction means 6a performs geometry correction on the RF signal obtained from the DVD-ROM disc, so that good reproduction characteristics can be obtained. Here, optical disks that are compatible with the optical information recording and reproducing apparatus include optical disks reproduced by a blue laser by the blue LD 10a, for example, recording / reproducing media such as HD DVD (trademark), and DVD-ROM disks. Playback-only media, and the like.

3 is a block diagram showing an optical information recording and reproducing apparatus according to a comparative example, and FIG. 4 is a schematic diagram showing a reproducing section of the optical information recording and reproducing apparatus according to the comparative example. First, the comparative example of FIG. 3 is demonstrated.

The optical information recording and reproducing apparatus of the comparative example includes a blue LD 10a, a red LD 10b, and an objective lens 16 whose NA is about 0.6. This optical information recording and reproducing apparatus is an optical disc recorded / reproduced with a blue laser irradiated from a blue LD 10a, for example an HD DVD (trademark), and a DVD-ROM reproduced with a red laser irradiated from a red LD 10b. Record and / or reproduce information on the disc.

An operation of reading a signal from the optical disc 18 using the optical information recording and reproducing apparatus of the comparative example will be described.

The blue LD 10a corresponding to the next-generation DVD optical disc standard or exclusively for reproduction, for example, the red LD 10b having a wavelength corresponding to the optical disc standard such as a DVD-ROM disc, respectively, is a continuous wave for the blue LD. It is driven by the driving circuit 54a and the red LD CW driving circuit 54b.

That is, the CW output irradiated from the blue LD 10a passes through the dichroic prism 11 and goes to the half mirror 12. A part of the CW output is branched by the half mirror 12 to be incident on the monitor light receiving element 14, and then converted into a current. Subsequently, the converted electric signal is input to a blue LD automatic power control circuit (hereinafter referred to as an APC circuit) 56a, so that the output of the blue LD 10a maintains a predetermined value. For controlling the CW drive circuit 54a.

In addition, the CW output irradiated from the red LD 10b is reflected by the dichroic prism 11 and directed to the half mirror 12. A part of the CW output is branched from the half mirror 12, is incident on the monitor light receiving element 14, and then converted into an electric signal. This converted electric signal is input to the red LD APC circuit 56b and controls the red LD CW drive circuit 54b.

First, the optical pickup (PU) 8 is moved to the inner circumference of the optical disc 18, and then irradiated with a beam of a predetermined light output, for example, a blue and red laser beam having a light output of 0.5 mW. This irradiated laser beam is focused by an objective lens 16 having a numerical aperture of approximately 0.65 to form an optical spot on the optical disk 18.

The beam reflected from the optical disk 18 is incident on the main light receiving element 20 via the objective lens 16. The main light receiving element 20 is a multi-division region for detecting a focusing error signal (hereinafter referred to as FE signal), a tracking error signal (Tracking Error signal; TE signal), and an RF signal. Consists of.

The beam incident on the multi-division region of the main light receiving element 20 is converted into an electrical signal, and then arithmetic operation is performed by the arithmetic unit 30 according to a predetermined arithmetic expression. Each of these calculators 30 receives an information signal on the optical disc 18 therein.

First, the focusing coil 22 is moved in the vertical direction with respect to the optical disc 18, and it is determined whether the optical disc 18 is set in the apparatus based on the calculation result of the FE signal. Here, if it is confirmed that the optical disk 18 is set, the peak-peak level of the FE signal is read. Then, the type of the optical disc is determined by a widely known method.

In addition, the gain of the voltage controlled amplifier circuit (hereinafter referred to as a VCA circuit) 34a is adjusted by comparing the set value of the peak-to-peak level of the FE signal. Turn the servo on.

Next, the optical disk 18 is rotated, and the peak-peak level of a predetermined detection signal, for example, a TE signal, is read out. Then, by comparing the set values, the two poles of the VCA circuit 34b are adjusted to turn on the tracking servo in the ON track. Then, the RF signal is detected from the rotating optical disk 18.

Next, the peak-peak level of the RF signal is compared with the set value to adjust the gain of the VCA circuit 34d, and the blue LD equalizer circuit of the RF signal according to the signal determined by the disc discrimination circuit 44 Equalizer circuit (hereinafter referred to as EQ circuit) 37a or red LD EQ circuit 37b is selected. Here, the TE signal output from the operator 30 is branched, one side is directly input to the VCA circuit 34b, and the other side is a low pass filter (hereinafter referred to as LPF) 33. Is entered. Therefore, the TE signal is smoothed in the LPF and then input to the VCA circuit 34c. In addition, the FE signal output from the calculator 30 is input to the VCA circuit 34a. The FE signal output from this VCA circuit 34a is sent to a pulse width modulation circuit (hereinafter referred to as a PWM circuit) 38 via a digital equalizer (Digital EQ) 36a.

In addition, the RF signal output from the VCA circuit 34d is branched to the blue and red LD EQ circuits 37a and 37b, and each operator 30 receives a result from the disc discrimination circuit 44 by each operator 30. One EQ circuit 37a or 37b is selected. The RF signal by the selected EQ circuit 37 is input to the slice circuit 39, and the synchronous detection circuit 41, the phase-locked loop (PLL) circuit 40, and the EFM; Eight to Fourteen Modulation) is output to the circuit (42). The synchronous detection circuit 41 is connected to the PLL circuit 40, and is input to the PWM circuit 38 after being compared with a reference clock (not shown).

From the PWM circuit 38, a focusing signal FOCS is output to the focusing coil 22, and a tracking signal TRKG is output to the tracking coil 24. In addition, the spindle motor control signal SPDL and the carriage signal CARG are output.

In addition, a signal for disc discrimination is input to a central processing unit (hereinafter referred to as a CPU) 46. The CPU 46 is connected to a servo controller 52, a disc discrimination circuit 44, and a random access memory (hereinafter referred to as RAM) 48, and the optical information recording and reproducing apparatus. Take control of the whole.

Next, CW driving conditions of the semiconductor laser 10 will be described.

In general, the maximum rated output of a LD used for reproduction of a DVD-ROM disc having a center wavelength of 650 nm wavelength and a CD-ROM disc having a center wavelength of 780 nm wavelength is 5 or 7 Hz or less. Therefore, it is possible to record / reproduce information with respect to DVD-ROM discs, CD-ROM discs and their compatible optical disc standards with the optical pickup having this maximum rated output.

As shown in Fig. 4, the optical information recording and reproducing apparatus of the comparative example includes a blue LD 10a, a diffraction grating 63, a dichroic prism 11, a first detection lens 64a, and a main light receiving element 20. , DVD hologram unit 20b, reflective mirror 62, collimated lens 65, 1/2 wave plate 66, half mirror 12, second detection lens 67, monitor light receiving element ( 14), quarter wave plate 68, and objective lens 16 having an NA of about 0.65.

The transmission optical elements do not transmit 100% of incident light. For example, when the transmittance of 650nm band of each component is 70% and a CW beam of 0.5 s is to be obtained after the objective lens 16 by using six transmission optical elements, the light of the semiconductor laser LD is used. Output P ₁ requires 4.25 kW. That is, P ₁ = 0.5 / (0.7 ^ 6) = 4.25 mW. Therefore, if the maximum rating of LD was 5 GPa, it was enough.

However, there is a need for a compatible optical information recording and reproducing apparatus including a next-generation DVD having a center wavelength of 405 nm. In this case, it is very difficult to maintain high transmittance for all of the two or three wavelengths including the 405 nm band. For example, even when designed to have a transmittance of 90% in the 405 nm band, it is often 50% in the 650 nm band. In addition, it is necessary to match a phase or the like for each wavelength, and the number of optical parts passing through each wavelength inevitably increases.

For example, when the wavelength of 650 nm is used at the 5 kHz output, when there are 6 transmission optical elements and the transmittances are 70, 60, 70, 50, 70, and 60%, the light output P ₂ is 0.31 ㎽ Required. That is, P ₂ = 5 x 0.7 x 0.6 x 0.7 x 0.5 x 0.7 x 0.6 = 0.31 mW. Therefore, in the case of using an LD having a light output of 5 kHz, reproduction may not be sufficient. In other words, 0.5 kW is required for reproduction on the optical disc 18, and the required light output P ₃ is 8.1 mW. That is, P ₃ = 0.5 / (0.7 × 0.6 × 0.7 × 0.5 × 0.7 × 0.6) = 8.1 μs. Therefore, reproduction is difficult with the reproduction LD having a maximum rated output of 5 kW. If the LD is used with a CW output of 8 mW, it is easy to cause catastrophic optical damage (COD) in the LD cross section due to a temperature rise or the like.

It can be solved by using a new type of semiconductor laser having a large maximum rated power, but in this case, a new semiconductor laser design is required, and there is a problem that an optical system of an optical pickup is required. Therefore, in the case of solving the above-mentioned problems while using a conventional semiconductor laser, the design of a new semiconductor laser or an optical system can be unnecessary or simplified, it is easy to take a high frequency weight, and can be very advantageous in terms of cost. Therefore, the present invention is characterized by having a configuration which can solve the above problems while employing a conventional semiconductor laser in view of such a point.

According to the embodiment of the present invention, not only can a DVD-ROM disc be played back from the blue LD 10a, but also a red LD 10b for DVD playback by performing a symbol correction on the RF signal. And the optical element used only with the red laser, its driving circuit and APC are unnecessary. In addition, the loss of light efficiency due to the optical element can be reduced, and the maximum rated power can be reduced in energy.

When playing an optical disc, a phenomenon called "asymmetry", which is a phenomenon in which the center of the eye pattern of the RF signal is displaced, may occur (for example, "the illustrated compact disc reader (revised edition 2)"). Nakashima, Kogawa, 1988, Omsa). The asymmetry that occurs in a CD or DVD recorder depends on the shape of the pit and the depth of the pit in the disc manufacturing process. For this purpose, asymmetry correction is performed to adjust the recording signal so that the DC component of the EFM signal is zero. It is done.

On the other hand, in the present embodiment, the correction of the structure is based on the correct geometry that is the center of the peak-to-peak of the signal by shifting the center of the eye pattern of the RF signal reproduced from the optical disk against the misalignment caused when the optical system is not reproduced. I use it to mean correction.

Next, the optical information recording and reproducing apparatus of this embodiment shown in FIG. 1 will be described.

As shown in Fig. 1, in the optical information recording and reproducing apparatus of this embodiment, the geometry correction means 6a is provided between the VCA circuit 34d of the RF signal and the EQ circuits 37a and 37b for the red and blue LD. . This geometry correction means 6a comprises an analog-to-digital converter (hereinafter referred to as AD converter) 1 for converting an input analog signal into a digital signal, and a peak detection circuit 3 for detecting a peak value of the converted digital signal. ), An average value detection circuit 5 for calculating an average value from the detected peak values, and a geometry correction circuit 7 for correcting the geometry from the calculated average values. 3, the red LD 10b, the red LD CW driving circuit 54b, and the red LD APC circuit 56b are excluded from the apparatus shown in FIG.

Here, the geometry correction means 6a performs geometry correction as follows. That is, the AD converter 1 digitizes each waveform of the RF signal output from the VCA circuit 34d, the peak detection circuit 3 detects the peak value of each wave, and the average value detection circuit 5 Averages the overall peak values. The wave correction circuit 7 corrects each wave to have a shape of a shape.

For example, FIG. 5 is a schematic diagram showing the waveform of the RF signal obtained from the optical information recording and reproducing apparatus of this embodiment, in which FIG. 5A is the waveform of the RF signal before the correction of the geometry, and FIG. 5B is the waveform of the RF signal after the correction of the geometry. Waveform.

As shown in FIG. 5A, the RF signal that does not have the geometry correction is composed of a continuous waveform in which the waveform of the short T (T: 1 bit time width) is not located at the center and the structure is disturbed. Here, the peak maximum voltages of the digitized signals are represented by p ₁ , p ₃ , p ₅ ,. , p _n , and the peak minimum voltage is, for example, p ₂ , p ₄ , p ₆ ,. , p _{n + 1} , the center value for each T waveform is calculated, for example, w _n = (p _n + p _{n + 1} ) / 2, and the center value of the whole is Σw _n / (n / 2) is detected by the average detection circuit. Here, the center value of the entirety is, for example, 2.5 volts (V).

And as shown to FIG. 5B, the geometry correction can be performed so that the center value of the whole may approach 2.5V, for example. Therefore, it becomes possible to play the DVD-ROM disc with the blue LD 10a.

Hereinafter, the optical information recording and reproducing apparatus according to the embodiment of the present invention will be described in detail.

6A and 6B show an eye pattern representing an RF signal obtained by reproducing a DVD-ROM disc using a red laser of 650 nm band in the optical information recording and reproducing apparatus according to the comparative example of FIGS. 6A is a case where the red LD EQ 37b is not used, and FIG. 6B is a case where the red LD EQ 37b is used.

This waveform is displayed on the oscilloscope and the eye pattern is shown by overwriting the 14T (T: channel time width) of the RF signal from 3T. As shown in Figs. 6A and 6B, regardless of the presence or absence of the red LD EQ 37b, the center of each T is almost at the center position, and the eye is further opened by the red LD EQ 37b. have.

7A and 7B are eye patterns representing RF signals obtained by reproducing a DVD-ROM disc using a blue laser having a wavelength of 405 nm in the optical information recording and reproducing apparatus according to the comparative example of FIGS. 3 and 4. 7A is a case where the red LD EQ 37b is not used, and FIG. 7B is a case where the red LD EQ 37b is used.

As shown in Fig. 7A, since the geometry correction means 6a is not used, the amplitude of the 3T waveform, which is the shortest pit time width, becomes lower than the center position. In addition, even when the red LD EQ 37b is used for this signal, an appropriate equalizer is not applied to the waveform of the RF signal as shown in Fig. 7B, and the center of each T becomes nonuniform, resulting in a time shift. Even if the slice level is set at the center position in this state, rotation control and signal demodulation of the spindle motor become difficult.

On the other hand, according to the optical information recording and reproducing apparatus according to the embodiment of the present invention, the RF signals of the DVD-ROM disc and the CD-ROM disc can be improved by the geometry correction means 6a.

Fig. 8 shows an RF signal after reproducing a DVD-ROM disc with a blue laser and equalizing it with a red LD EQ 37b in the optical information recording and reproducing apparatus according to the embodiment of the present invention shown in Figs. An eye pattern representing.

As shown in Fig. 8, according to this embodiment, the geometry correction means 6a shows that even in the DVD-ROM disc, the jitter is small and the center of each T becomes almost the center position.

9 is a block diagram showing a reproduction unit of the optical information recording and reproducing apparatus according to the second embodiment of the present invention.

In the optical information recording and reproducing apparatus according to the present embodiment, instead of the geometry correction circuit 7 included in the geometry correction means 6a of FIG. 1, the red LD EQ 37b and the blue LD EQ 37a, a slice level is used. It is characterized in that it includes a correction circuit 58. That is, the geometry correction means 6b includes an AD converter 1, a peak detection circuit 3, an average value detection circuit 5, and a slice level correction circuit 58. According to the present embodiment, by calculating the average value of the geometry instead of the correction, the sliced RF signal can be corrected based on the slice level calculation value in the slice level correction circuit 58. Therefore, the same effect as that of the optical information recording and reproducing apparatus according to the embodiment described with reference to FIG. 1 can be obtained.

In the first and second embodiments, an HD DVD (trademark), which is an optical disk whose cover layer thickness is 0.6 mm and the center wavelength is optimized for recording and playback using laser light in the 405 nm band, and the cover layer thickness is 0.6 mm The compatibility of DVD-ROM discs, which are optical discs optimized for recording and reproduction using laser light having a wavelength of 650 nm, has been described.

On the other hand, as an optical disk whose center wavelength is optimized for recording and reproducing by laser light having a wavelength of 405 nm, in addition to the optical disk having the cover layer thickness of 0.6 mm, an optical disk having a cover layer thickness of 0.1 mm or 0.3 mm has been proposed and developed. For example, Blu-ray (trademark) is proposed as an optical disk with a cover layer thickness of 0.1 mm. In this case, the NA of the objective lens 16 is about 0.85.

As described above, an optical disc with a cover layer thickness of 0.1 mm and a center wavelength of 405 nm is optimized for recording and reproduction, and an optical disc with a cover layer thickness of 0.6 mm and a center wavelength of 650 nm is optimized for recording and reproduction. The compatibility of the DVD-ROM discs can be realized in the same manner.

Fig. 10 is a block diagram showing a playback unit of the optical information recording and reproducing apparatus according to the third embodiment of the present invention.

The optical information recording and reproducing apparatus according to the third embodiment is characterized in that the NA of the objective lens 16 is about 0.85 and includes an opening limiting element 19 and an opening limiting control circuit 60. The aperture limiting element 19 is disposed between the objective lens 16 and the blue LD 10a and has an aperture limiting function of wavelength selectivity. The aperture limiting element 19 is composed of a hologram element or a liquid crystal element having wavelength selectivity. The aperture limiting control circuit 60 is provided between the aperture limiting element 19 and the CPU 46 to control the aperture limiting element 19 so that the numerical aperture of the objective lens 16 has a predetermined value. can do.

Therefore, when an optical disc with a cover layer thickness of 0.6 mm and a center wavelength of 650 nm is optimized like a DVD-ROM disc is inserted, the disc discrimination circuit 44 discriminates the optical disc. Based on the determination result, the opening limit control circuit 58 controls the NA to be about 0.6 or about 0.65 in accordance with the DVD-ROM disc or the like inserted by the liquid crystal element 19. Subsequently, it is possible to perform geometry correction or slice level correction as in the first and second embodiments.

As described above, according to the present invention, the blue LD 10a can be used for correct reproduction by performing geometry correction or slice level correction of the RF signal extracted from the DVD-ROM disc. In addition, the optical component that transmits only the red LD and the red laser for DVD reproduction, its driving circuit, and the APC become unnecessary, and the output of the blue LD 10a can be made low. As a result, a compatible optical information recording and reproducing apparatus including a next generation DVD can be realized.

As mentioned above, although the Example of this invention was described referring drawings, this invention is not limited to these specific examples.

For example, various design changes made by those skilled in the art regarding the size, shape, arrangement, and the like of components of semiconductor laser, LPF, geometry correction means, optical component, light receiving element, etc. constituting the optical information recording and reproducing apparatus are also described. It is included in the present invention as long as it does not depart from the gist. In addition, the optical discs of the present invention have been described using only ROM discs as an example, but DVD-R also includes a warm disc (WORM Disc; Write Once Read Many Dics), a rewritable disc, DVD + R, DVD + RW, and the like. The same effect as that of a ROM disk is obtained.

Claims (13)

Recording and reproducing were performed for the first optical disk with a cover layer thickness of 0.1 mm or 0.6 mm and having a center wavelength of 405 nm and having optimized recording and reproduction, and a cover layer thickness of 0.6 mm and a center wavelength of 650 nm. It is possible to perform playback on a second optical disc in which recording and reproduction are optimized with a large number of laser lights. A blue laser diode (LD) for irradiating laser light having a center wavelength of 405 nm to the first and second optical disks; An objective lens for focusing light irradiated from the blue LD onto the first and second optical disks; And a geometry correction means for correcting a reproduction signal (RF signal) when the information on the second optical disk is reproduced. The method of claim 1, An opening limiting element disposed between the blue LD and the objective lens, the opening limiting element selectively limiting the opening according to the wavelength with respect to the laser light irradiated to the first or second optical disk; And an opening limit control circuit for controlling the opening limiting element. The method of claim 2, When recording and reproducing optical information are made compatible with the first optical disc and the second optical disc having a cover layer thickness of 0.6 mm, And the aperture limiting element is controlled so that the numerical aperture of the objective lens is optimized for recording and reproduction of the first optical disc. The method of claim 2, When recording and reproducing optical information are made compatible with the first optical disc and the second optical disc having a cover layer thickness of 0.1 mm, And the aperture limiting element is controlled so that the numerical aperture of the objective lens is optimized for recording and reproduction of the second optical disc. The method of claim 4, wherein When the cover layer thicknesses of the first and second optical discs are different, the numerical aperture of the objective lens is optimized for recording and reproduction of the second optical disc, based on a result of the type discrimination of the first and second optical discs. Compatible optical information recording and reproducing apparatus. The method according to any one of claims 1 to 5, The geometry correction means, An analog-digital converter for converting the input analog signal into a digital signal; A peak detection circuit for detecting a peak value of the converted digital signal; And an average value detection circuit for calculating an average value from the detected peak values. The method of claim 6, The geometry correction means, And a geometry correction circuit for correcting the geometry from the average value calculated by the mean value detection circuit. The method of claim 7, wherein The geometry correction circuit, And correcting the geometry before the RF signal extracted at the time of reproduction of the second optical disc is synchronized with the rotation of the optical disc. The method of claim 7, wherein The geometry correction circuit, And correcting the geometry before signal demodulating the RF signal extracted during reproduction of the second optical disc. The method of claim 7, wherein The geometry correction circuit, And correcting the geometry before slicing the extracted RF signal during reproduction of the second optical disc. The method of claim 6, The geometry correction means, And a slice level correction circuit for calculating an average value calculated by the average value detection circuit and correcting an RF signal with disturbed geometry. The method of claim 11, The slice level correction circuit, And a slice level is corrected before slicing the extracted RF signal during reproduction of the second optical disc. The method of claim 11, Each of the peak detection circuit and the average value detection circuit, And a peak and a mean value for a one-bit time width are detected before slicing the extracted RF signal during reproduction of the second optical disc.

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