KR100464764B1 - Recording medium recording and reproducing apparatus and recording medium recording and reproducing method - Google Patents

Abstract

The laser diode irradiates a laser beam onto a compact disk (CD) through a grating, a beam splitter, and an objective lens. Then, the laser light reflected by the CD enters (enters) the photodiode through the objective lens and the beam splitter. The numerical aperture (NA) of the objective lens is set to 0.6 so that a digital video disk (DVD) on which data is recorded at a high density with a thin substrate thickness can be reproduced. In order to prevent the influence of the aberration caused by the objective lens having a large numerical aperture, only the return light of NA up to about 0.3 is detected in the photodiode, and the normalized detector Thereby forming a relatively small-sized light-receiving portion having a size of 3 탆 to 16 탆.

Description

Recording medium recording and reproducing apparatus and recording medium recording and reproducing method

The present invention relates to a recording medium recording and reproducing apparatus and a recording medium recording and reproducing method, and more particularly to a recording medium recording and reproducing apparatus and a recording medium recording and reproducing apparatus for recording or reproducing information on a plurality of kinds of disk- ≪ / RTI >

A CD has been widely used as a recording medium for reproducing information using light. However, recently, a new recording medium such as a DVD for digitally recording an image of a long time has been considered.

In reading such digital information from a recording medium using light, the laser light is irradiated onto the recording medium, the reflected light from the recording medium is detected, and the level of the reflected light is converted into binary data.

Fig. 1 shows an example of a configuration of an optical pickup for CD. As shown in Fig. 1, the laser diode (LD) 1 generates laser light having a wavelength of 780 nm. The grating 2 divides a single laser beam emitted from the LD 1 into a plurality of (substantially three) laser beams. One of the three laser beams is used for reading and focusing record information And the other two are used for the tracking servo. The three laser beams are also collectively referred to as light.

The beam splitter 3 made of a transparent parallel flat plate reflects the laser light emitted from the LD 1 through the grating 2 toward the objective lens 4 and is incident on the objective lens 4, (Converged light) reflected by the CD 10 returned through the photodiode 5 to the photodiode (PD) 5 as a photodetector. While the reflected light is transmitted through the beam splitter, the reflected light is given astigmatism by the beam splitter 3.

The objective lens 4 converges the laser light to irradiate the information recording layer 12 of the CD 10 on which the fine pits are arranged. The objective lens 4 converges the reflected light from the information recording layer 12 of the CD 10 and enters the photodiode 5 via the beam splitter 3. [

The larger the numerical aperture (NA) of the objective lens 4, the larger the angle at which the light converges, and the light converges in a smaller range. In Fig. 1, (4) are used.

The photodiode 5 is adapted to detect the return light of the laser light irradiated to the CD 10 by the LD 1. [ Since the laser light emitted from the LD 1 is divided into three by the grating 2, there are also three light receiving portions of the photodiode 5 corresponding thereto. One of them receives the laser light reading the recorded digital information, and the other two receives the two laser lights for tracking servo control. In particular, it is used for tracking control of the objective lens 4 so that laser light for reading digital information recorded in accordance with the difference in the amount of light between the two laser lights is irradiated on a predetermined track of the CD 10.

Since the laser light reflected by the information recording layer 12 and incident on the photodiode 5 passes through the beam splitter 3 as convergent light, astigmatism is generated. The focus servo of the objective lens 4 is performed using this astigmatism.

In the CD 10 as a recording medium, an information recording layer 12 is formed on a transparent substrate 11 having a thickness t of 1.2 mm and a protective film 13 is formed on the information recording layer 12. The laser light emitted from the LD 1 is converged by the objective lens 4 and is transmitted through the transparent substrate 11 to be irradiated onto the information recording layer 12. The information recording layer 12 has fine pits corresponding to the recording information. When the laser light is irradiated on the pits, the information recording layer 12 causes diffraction, and return light (reflected light from the recording medium and incident on the photodiode 5 ) Is weakened. When a laser beam is irradiated to a place where no pit is irradiated, the laser beam is directly reflected, so that the intensity of the return light is strong. As described above, the return light from the CD 10 is detected by the photodiode 5, and the intensity of the return light is converted into binary numbers "1" and "0" The digital data is read.

As described above, the digital information recorded from the CD 10 is read by irradiating the laser light to the predetermined position of the CD 10 while detecting the tracking servo and the focus servo, and detecting the return light.

Recently, a DVD having the structure shown in Fig. 2 has been proposed. Information is recorded on only one side of the CD 10, whereas information is recorded on both sides of the DVD 20. Particularly, in the DVD 20, the first disc member forms the substrate 21, the information recording layer 22 is formed on the substrate 21, the protective film 23 is formed thereon, The disk member forms the substrate 31 and the information recording layer 32 is formed on the substrate 31 and the protective film 33 is formed on the substrate 31. The first and second disk members are formed on the protective film 23, And the protective film 33, as shown in Fig. Therefore, the DVD 20 is symmetrical with respect to the center plane thereof.

Since the digital information is recorded at a high density in the DVD 20, the substrates 21 and 31 are thinner than the substrate 11 of the CD 10 in order to reduce the influence of skew, . That is, while the substrate 11 of the CD 10 is 1.2 mm thick, the substrates 21 and 31 of the DVD 20 are 0.6 mm thick. In addition, the pit length and pit interval in the DVD 20 are shorter than those of the CD 10.

Since the recording density of the DVD 20 is larger than the recording density of the CD 10 as described above, the LD 41 of the optical pickup device for the DVD 20 needs to have a shorter wavelength (650 nm ) Is used for generating the laser beam. The grating 42, the beam splitter 43, the objective lens 44, and the photodiode (PD) 45 are configured in the same manner as the CD optical pickup device.

However, since the DVD 20 has finer pits than the CD 10 (because the recording density is large), the objective lens 44 is provided with the numerical aperture NA (NA) of 0.45 (NA = 0.6) is used. As described above, by using the objective lens 44 having a large numerical aperture, it is possible to converge the laser light in a smaller range and to read fine pits.

As described above, since the structures of the CD 10 and the DVD 20 are different, it is generally necessary to use a different optical system (optical pickup device) in order to read the record information from the CD 10 and the DVD 20. [

3, when the optical pickup device for the DVD 20 is to be applied to the CD 10, the optical pickup device for the DVD 20 reads the record information of the DVD 20 in the best state The difference in thickness between the substrate 11 of the CD 10 and the substrates 21 and 31 of the DVD 20 and the difference in the thickness of the objective lens 4 ) And (44), the influence of the spherical aberration appears.

For example, when a CD having a substrate thickness of 1.2 mm is reproduced with an objective lens having numerical apertures of 0 and 6 optimized for a DVD having a substrate thickness of 0.6 mm, the generated spherical aberration is converted into a fourth- ) Spherical aberration coefficient W ₄₀ , reaching 3.6 탆. This is expressed as a square average (rms), and becomes 0.268 rms 占 퐉 (0.412 rms? When standardized by the wavelength? (= 650 nm)). In optical discs, in general, the square sum total of the aberrations of all the optical systems is Of 0.07 rms? Or less. Therefore, it is difficult to accurately read the record information of the CD 10 with the configuration as shown in Fig.

Thus, the applicant of the present invention has found that, by adjusting the NA of the objective lens in accordance with the type of the recording medium to be read, the application of the optical pickup for DVD to CD can be achieved, for example, in Japanese Patent Application No. 6 (1994) -277400 No. 08 / 555,339).

Fig. 4 and Fig. 5 show the principle of the above proposal. As shown in these drawings, this configuration example is similar to that of the optical pickup device for DVD shown in Fig. 2 except that the aperture stop 51, the drive unit 53 for driving the aperture stop 51, And the discriminating device 52 is disposed.

The discriminating device 52 discriminates the type of the recording medium and the driving part 53 drives the diaphragm 51 in accordance with the discrimination result of the discriminating device 52. Particularly, when the drive unit 53 reads the record information of the DVD 20, as shown in Fig. 4, the diaphragm 51 is opened so that the NA of the objective lens 44 becomes 0.6. On the other hand, when the recording information of the CD 10 is read, the driver 53 opens the diaphragm 51 so that the NA of the objective lens 44 is 0.45, as shown in Fig. In this way, when reading the record information of the CD 10, the numerical aperture of the diaphragm 51 is reduced, and the influence of the spherical aberration (the fourth order spherical aberration coefficient W ₄₀ is proportional to the fourth power of the numerical aperture NA ) Is reduced, and a reading operation is performed.

However, if such a mechanical diaphragm 51 is newly disposed, the number of components of the apparatus is increased, which not only becomes expensive, but also increases the size of the apparatus. Since the diaphragm 51 operates mechanically, the diaphragm 51 is vulnerable to vibration, and it is difficult to perform a quick operation, which is a cause of failure.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and it is an object of the present invention to provide an apparatus and a method for detecting a return light entering a predetermined range without requiring a mechanical diaphragm, The present invention enables writing or reading of data with respect to a recording medium of the above type.

According to the recording medium recording and reproducing apparatus of the present invention, a first recording medium having an information recording layer on a substrate of a first thickness and a second recording medium having an information recording layer on a substrate of a second thickness A recording medium recording and reproducing apparatus for selectively recording or reproducing information, comprising: generating means for generating light to be irradiated on an information recording layer of the first or second recording medium; And a light receiving means for receiving return light from the information recording layer of the first or second recording medium, wherein the light receiving means receives the light reflected from the information recording layer of the first or second recording medium, The means is characterized in that the normalized detector size is 3 μm or more and 16 μm or less.

According to the recording medium recording and reproducing method of the present invention, the information recording layer of the first or second recording medium is provided with the generating means for generating light to be irradiated through the substrate, the light from the generating means, The optical pickup device comprising irradiation means for irradiating the information recording layer of the first or second recording medium and light receiving means for receiving the feedback light from the information recording layer of the first or second recording medium, A first recording medium having an information recording layer on a substrate of a first thickness or a second recording medium having an information recording layer on a substrate of a second thickness thicker than the first thickness, A recording medium recording and reproducing method for recording or reproducing information, the method comprising the steps of: irradiating return light from the information recording layer with the light receiving means having a normalized detector size of 3 m or more and 16 m or less It characterized by comprising a step of light.

According to the recording medium recording and reproducing apparatus of the present invention, the first recording medium having the information recording layer on the substrate of the first thickness, the second recording medium having the information recording layer on the substrate of the second thickness, A recording medium recording and reproducing apparatus for selectively recording or reproducing information with respect to a medium, the recording medium recording and reproducing apparatus comprising: generating means for generating light to be irradiated on the information recording layer of the first or second recording medium; Irradiating means for irradiating the information recording layer of the first or second recording medium to the information recording layer of the first or second recording medium and receiving means for receiving return light from the information recording layer of the first or second recording medium, Wherein the light receiving means is arranged so that its normalized detector size is larger than the diameter of a spot on the light receiving means of the return light when the _first numerical aperture from the first recording medium is N ₁ , Of Is smaller than the diameter of a spot of light on the light-receiving means of the return light when the _second numerical aperture is larger than N ₂ .

According to the recording medium recording and reproducing method of the present invention, the information recording layer of the first or second recording medium is provided with the generating means for generating light to be irradiated through the substrate, the light from the generating means, The optical pickup device comprising irradiation means for irradiating the information recording layer of the first or second recording medium and light receiving means for receiving the feedback light from the information recording layer of the first or second recording medium, A first recording medium having an information recording layer on a substrate of a first thickness or a second recording medium having an information recording layer on a substrate of a second thickness thicker than the first thickness, Wherein the normalized detector size is a diameter of a spot on the light receiving means of the return light when the _first numerical aperture from the first recording medium is N ₁ , Is smaller than the diameter of a spot of light on the light-receiving means of return light when the _second numerical aperture from the second recording medium is larger than N ₂ , the light from the information recording layer The method comprising the steps of:

Next, embodiments of the present invention will be described in detail with reference to the drawings.

Fig. 6 shows a cross-sectional view of a configuration example of an optical pickup device in an embodiment of the recording medium recording and reproducing apparatus of the present invention. 6, the optical pickup apparatus includes an LD 41 (generating means) for generating a laser beam having a wavelength of 650 nm (or 635 nm), a laser beam generated by the LD 41, A beam splitter 43 for separating incident light and reflected light and imparting astigmatism to the reflected light, and an objective lens 44 having an NA of 0.6 for irradiating laser light to the recording medium And a photodiode 61 (light receiving means) which detects the reflected light and has a small light receiving portion. The photodiode 61 having a small light receiving portion detects only the return light (reflected light) incident in a predetermined range, and does not detect the return light of the outer peripheral portion.

Next, the size of the light receiving portion of the photodiode 61 as the photodetector used in the present embodiment will be described.

7 is a graph showing the relationship between the thickness of the substrate of the recording medium and the thickness of the substrate of the DVD 20 when the thickness of the substrate of the recording medium is increased by 0.1 mm from the thickness of 0.6 mm (the thickness of the substrates 21 and 31 of the DVD 20) Of the return light.

As shown in Fig. 7, the more the light (light in the case of NA is larger) that is incident on the photodiode 61 away from the optical axis, the more the imaging point is away from the Gaussian plane. When the NA is 0.45, the imaging point is about 5 占 퐉 from the Gaussian plane, and when NA is 0.6, the imaging point is about 8.3 占 퐉, away from the Gaussian plane. When the thickness of the substrate of the recording medium is increased by 0.6 mm to 1.2 mm (the thickness of the substrate 11 of the CD 10), deviation of the imaging point from the Gaussian plane when NA is 0.6 is about 51.8 탆 ( = 8.3 [micro] m > 0.6 mm / 0.1 mm), so that the imaging point greatly deviates from the Gaussian plane.

8 shows the relationship between the increment of the thickness Δ when the thickness of the substrate of the recording medium is 0.6 mm (the thickness of the substrates 21 and 31 of the DVD 20) The point at which the wavefront aberration rms becomes minimum, and the point at which the spot intensity becomes maximum on the optical axis) from the Gaussian plane.

The case where the embodiment shown in Fig. 6 is applied to DVD corresponds to the point A in Fig. That is, when the thickness of the substrate is 0.6 mm (the increment Δt of thickness is 0 mm), the point where the light of NA = 0.6 converges, the point where the wavefront aberration becomes minimum and the point on the optical axis where the spot intensity becomes maximum , All located on the Gaussian plane. On the other hand, when the thickness of the substrate increases, these points gradually move away from the Gaussian plane, and the distance becomes a different value at each point.

When the optical pickup apparatus shown in Fig. 6 is applied to a CD having a thickness of 1.2 mm (increase in thickness? T of 0.6 mm), the distance from the Gaussian plane at which the wave front aberration is minimized is about 24 占 퐉 (point B) . The point (spot intensity maximum point) at which the spot intensity of light becomes maximum on the optical axis becomes a point (point C) of about 10 占 퐉 from the Gaussian plane.

6, the present embodiment basically includes components for DVD (LD 41, grating 42, etc.). Therefore, when this embodiment is applied to DVD 20 (point A , It can be seen that the feedback light has a good (sufficiently large) intensity as shown in Fig. 9, and almost spherical aberration does not occur, as shown in Fig. 11, both the radial direction of the disk (the curve of R in Fig. 11) and the tangential direction (the curve of T in Fig. 11) are all good.

On the other hand, when the intensity of the return light at a predetermined point between the optical axis and the point at which the wave-front aberration is minimized (point B in Fig. 8) when the present embodiment is applied to DVD and CD is calculated 12 to Fig. 12 shows the intensity distribution of the return light at the point on the Gaussian plane (the distance from the Gaussian plane is 0 μm). When the intensity of the return light at the time of DVD reading is 1, as shown in FIG. 12 Since the intensity is about 5%, it is difficult to read the record information at this point.

Figs. 13 to 17 show intensity distributions of the return light at distances of 4.0 占 퐉, 8.0 占 퐉, 10 占 퐉 (points C in Fig. 8), 12 占 퐉, and 16 占 퐉, respectively, along the optical axis from the Gaussian plane 18 shows the intensity distribution of the return light at a point of 24 占 퐉 from the Gaussian plane (point B in Fig. 8) at which the wavefront aberration is minimized.

As can be seen from Figs. 12 to 18, the point at which the intensity of the return light is maximized is not the point at which the wave front aberration is minimized (point B in Fig. 8) Therefore, the intensity at that time is about 15% of the intensity of the return light at the time of reading the DVD, and therefore, from the viewpoint of light intensity, Can be read.

At point B, as shown in Fig. 19, when the NA is about 0.15 or more, the spherical aberration becomes remarkably large. As shown by the MTF characteristic in Fig. 20, it is difficult to read the record information of the CD 10 having a resolution of about 100 lines / mm at the spatial frequency, and therefore, at the point B, about 2.5 tracks / mm .

21, the spherical aberration is relatively small as long as the NA is in the range of up to about 0.3, and as shown by the MTF characteristic of FIG. 22, Since the resolution capability in the disk radial direction (the curve of R in Fig. 22) and the tangential direction (the curve of T in Fig. 22) are about 1000 lines / mm in spatial frequency, It is possible to perform reading.

Therefore, by reading only the return light of NA up to about 0.3 at such a spot intensity maximum point, the recording information of the CD 10 is read.

Fig. 23 shows a normalized detector size in which one side has a square of 10 mu m, 15 mu m, and 20 mu m. The normalized detector size is a value obtained by dividing the length L of the actual detector (the light receiving portion of the photodiode 61) by the magnification m of the objective lens 44 (L / m). Therefore, the size of the actual detector is obtained by multiplying the dimension of the normalized detector size by the magnification of the objective lens 44. [ For example, when the magnification of the objective lens 44 is 7.2, the dimensions of the actual detectors are 72 (= 10 x 7.2), 108 (= 15 x 7.2), 144 do.

23, the shape of the return light of NA = 0.6, which is incident on the photodiode 61, becomes the largest circle in the concentric circle shown in Fig. 23. Therefore, when the photodiode 61 reads the DVD 20, A square normalized photodetector size of at least 10 mu m in each side is required.

FIG. 24 shows the relationship between the size of the normalized detector size and the range of the return light corresponding to each NA at the time of reading the CD. When the feedback light is detected at the maximum point of spot intensity, it is necessary to prevent detection of light (light having a large spherical aberration) having NA greater than 0.3 as much as possible, as described above. As shown in Fig. 24, when the normalized detector size is set to 20 占 퐉, all lights with an NA of 0.4 are detected. On the other hand, when the normalized detector size is 15 占 퐉 (particularly, when the upper left corner and the lower right corner of the normalized detector size of 20 占 퐉 are cut off), part of the light with NA of 0.4 is not received. Therefore, it is preferable that the normalized detector size is at most 16 mu m.

In summary, in order to be able to read the recorded information of the DVD and to prevent the return light having NA exceeding 0.3 at the time of reading the CD, the normalized detector size is set to 10 to 16 mu m It is appropriate. Thus, the photodetector has a normalized detector size larger than the diameter of the spot of the photodetector of the return light of the first numerical aperture N ₁ (0.6) from the DVD recording medium, and the second numerical aperture N _Is smaller than the diameter of the spot of the photodetector of the numerical aperture larger than ₂ (0.3).

25A to 25C show examples of such a specific shape of the photodiode 61. FIG. In this embodiment, as shown in Figs. 25A to 25C, a photodiode 61 having light receiving portions 61-1, 61-2, and 61-3 is used. The light receiving section 61-1 is used for the reading of the record information and the focus servo of the objective lens 44. The size of the light receiving section 61-1 is 90 占 85 占 (magnification of the objective lens 44 is 7.2 and thus the normalized detector size 12.5 占 11.8 占 퐉). The light receiving section 61-1 is divided into four regions A, B, C and D for focus servo by so-called astigmatism.

As shown in Fig. 6, in this embodiment, in order to detect only the return light incident within a predetermined range (NA of about 0.3), a photodiode having a sufficiently small (12.5 x 11.8 m) It is possible to read the record information of the CD 10 as shown in Fig. 26 in the same optical system as when reading the record information of the DVD 20. Fig.

The light-receiving units 61-2 and 61-3 are for controlling the objective lens 44 by a so-called three-beam tracking servo, but also for controlling the tracking by a differential push- Are divided into regions E, F, and G and H, respectively, in order to enable the servo operation.

When the recording information of the CD 10 is to be read, the objective lens 44 is controlled by a three-beam type tracking servo so that the spot of the tracking laser light is irradiated on the inner and outer sides of the track currently reading And the light receiving section 61-2 receives, for example, the return light of the tracking laser light spot on the inner peripheral side of the track, and the light receiving section 61-3 receives the return light of the tracking laser light spot on the outer peripheral side do.

When the tracking is proper, that is, when there is no tracking error due to the information reproducing laser beam spot, the intensity of the two return beams from the tracking laser beam spot is the same, but for example, When a tracking error occurs from the track to the outer circumference side, the tracking laser beam spot on the outer circumference side of the track is less likely to be caught on the track, so that the tracking laser beam on the outer circumference side of the track, The intensity of the reflected light reflected from the light becomes strong (the track has a pit for diffracting the light, so that the intensity of the reflected light becomes strong when the portion of the track is small). At the same time, The light reflected by the tracking laser light spot on the inner circumferential side of the track, which is received by the light receiving portion 61-2, The strength becomes weak. Conversely, if a laser light spot for information reproduction deviates from the track to the inner circumferential side, that is, if a tracking error occurs from the track to the inner circumferential side, the outer and inner circumferential sides of the track, The intensity of the feedback light reflected from the laser light spot for tracking becomes weak or strong, respectively.

Therefore, the intensity of the return light of the laser beams on the inner and outer circumferential sides (that is, the electrical signals output from the light receiving portions 61-2 and 61-3) is compared to judge that the return light of the laser light on the outer peripheral side of the track is strong It is possible to know that the tracking is shifted to the inner circumferential side and the direction and amount of the tracking deviation can be known, The tracking can be adjusted.

If the objective lens 44 is to be controlled by the tracking servo according to the 3-beam method at the time of reproduction of the record information of the DVD 20, the interval of the three laser beams is set to the interval And the DVD 20 is narrower in track pitch than the CD 10, and therefore, as shown in Fig. 28, the position of the optical spot of the laser beam and the track of the three laser beams The tracking control of the objective lens 44 is difficult.

Thus, in the present embodiment, when reading the record information of the DVD 20, the objective lens 44 performs the tracking servo of the differential push-pull method. When the tracking is shifted, the amount of light incident on the left and right areas of the light receiving portions 61-1, 61-2, and 61-3 in the track direction changes. Therefore, in the differential push- And detects a tracking deviation from the difference between the amounts of light.

29 shows an electrical configuration example of an embodiment of the recording medium recording and reproducing apparatus of the present invention. 29, among the light receiving portions 61-1, 61-2, and 61-3 of the photodiode 61, the light receiving portion 61-1 is mainly used for reading recording information and for focus servo Partly used for tracking servo). The light-receiving unit 61-1 is divided into four areas A, B, C, and D, and converts the received light into electrical signals.

The region A is connected to the adders 72 and 95 and the region B is connected to the adders 71 and 96 to output the signal after photoelectric conversion. The region C is connected to the adders 72 and 96, and the region D is connected to the adders 71 and 95 to output the signals after photoelectric conversion, respectively.

The light-receiving units 61-2 and 61-3 are used for the tracking servo. The light-receiving unit 61-2 is divided into areas E and F, and the received light is converted into electric signals. The regions E and F are connected to an adder 88 and a subtractor 98, respectively, for outputting electric signals. The light-receiving unit 61-3 is divided into areas G and H, and converts the received light into electrical signals. The regions G and H are connected to an adder 89 and a subtractor 99, respectively, which output electric signals.

The adder 71 calculates the sum of the electric signals output by the regions B and D of the light receiving unit 61-1 and outputs the sum to the adder 73. [ The adder 72 calculates the sum of the electric signals output from the areas A and C of the light receiving unit 61-1 and outputs the sum to the adder 73. [

The adder 73 calculates the sum of the electric signals of the adders 71 and 72 (the sum of the electric signals output from the areas A, B, C and D) and outputs the sum to the equalizer 75 through the amplifier 74. [ (Equalizing means) and the smoothing circuit 76. [

The equalizer 75 emphasizes the electric signal read out from the recording medium detected by the light-receiving unit 61-1 in accordance with a predetermined equalization characteristic as compared with the low frequency band and outputs the amplified electric signal to the binarizing circuit 78 have. At this time, the equalizer 75 changes the equalization characteristic in accordance with the discrimination result (kind of the recording medium) of the type of the recording medium currently read out, which is outputted by the comparison circuit 77 (discrimination means) . Since the DVD 20 records information at a higher density than the CD 10, the equalizer 75 can reproduce the DVD 20 at a higher frequency than that at the time of reproduction of the CD 10 And emphasizes the signal.

The smoothing circuit 76 smoothes the input signal and outputs a smoothed signal to the comparison circuit 77. [

The comparison circuit 77 compares the value of the output voltage of the smoothing circuit 76 at the time of reading the CD (the output level of the smoothing circuit 76 at the time of reading the CD and the smoothing circuit 76 at the time of reading the DVD) And the comparison circuit 77 compares the output of the smoothing circuit 76 (the output voltage value of the smoothing circuit 76 at the time of reading the DVD) with the approximate value at the time of reading the CD 3 times) and the level of the reference value are compared with each other to determine the type of the recording medium. The comparison circuit 77 outputs a signal indicating the type of the recording medium to the equalizer 75, the PLL (Phase Locked Loop) circuit 80, and the changeover switch 91.

The binarizing circuit 78 corrects the equalization signal outputted from the equalizer 75 and binarizes the binarized signal and outputs the binarized signal to the demodulation / ECC circuit 79 and the PLL circuit 80.

The demodulation / ECC circuit 79 demodulates the binarized data in accordance with the clock signal supplied by the PLL circuit 80 after error correction of the supplied signal, and outputs the image signal and the audio signal (in the case of CD, Signal only) to the processing circuit 81 as shown in Fig.

The PLL circuit 80 generates a clock signal from the signal supplied from the binarizing circuit 78 and outputs it to the demodulation / ECC circuit 79. At this time, since the frequency of the clock when demodulating the binarized data differs between the DVD 20 and the CD 10, the PLL circuit 80 outputs the frequency of the clock to demodulate the binarized data in accordance with the output signal of the comparison circuit 77 And supplies the clock signal of the corresponding frequency to the demodulation / ECC circuit 79.

The processing circuit 81 outputs an audio signal to the speaker 82 and an image signal to the CRT 83 when an image signal and an audio signal are supplied from the demodulation / ECC circuit 79. When only the audio signal is supplied from the demodulation / ECC circuit 79, the processing circuit 81 outputs the audio signal to the speaker 82. [

The subtractor 84 subtracts the difference between the sum of the output signals of the regions B and D of the light receiving portion 61-1 supplied from the adders 71 and 72 and the sum of the output signals of the regions A and C (B + d) - (a + c)) when the outputs of C and D are a, b, c and d, and outputs the calculated difference as a focus error signal through the amplifier 85 And outputs it to the servo circuit 86.

The focus servo circuit 86 controls the focus actuator 87 in response to the focus error signal so as to move the objective lens 44 in the optical axis direction so that the spot of light on the light receiving portion 61-1 becomes a circle.

The adders 88 and 89 calculate the sum of the electric signals output from the light receiving portions 61-2 and 61-3 and output the result to the subtracter 90. [ The subtracter 90 calculates the difference between the output signals of the adders 88 and 89 and outputs the result to the changeover switch 91 as a tracking error signal at the time of reading the CD.

When the electric signals corresponding to the amounts of light detected by the areas E, F, G and H are denoted by e, f, g and h at this time, the tracking error signal (the tracking error signal Error signal) becomes (e + f) - (g + h).

The subtracters 98 and 99 calculate the difference between the electric signals output from the light receiving portions 61-2 and 61-3 and output the result to the adder 100. [ The adder 100 calculates the sum thereof and outputs the result to the subtractor 102 via the amplifier 101. [

The amplifier 101 amplifies the signal supplied from the adder 100 by a predetermined factor K and outputs the amplified signal to the subtractor 102.

The adder 95 calculates the sum of the electric signals output from the areas A and D of the light receiving unit 61-1 and outputs the sum to the subtractor 97. [ The adder 96 calculates the sum of the signals output from the areas B and C, and outputs the sum to the subtractor 97. The subtracter 97 calculates the difference between the output signals of the adders 95 and 96 and outputs the result to the subtractor 102. [

The subtracter 102 calculates the difference between the signal from the amplifier 101 and the signal from the subtracter 97 and outputs the result as a tracking error signal (tracking error signal by the differential push-pull method) And is outputted to the changeover switch 91. [

The outputs of the regions A, B, C, D, E, F, G and H are denoted by a, b, c, d, The tracking error signal outputted to the changeover switch 91 becomes (b + c) - (a + d) -K {(ef) + (gh)}.

The changeover switch 91 switches the output signal of the subtractor 90 (the tracking error signal by the 3-beam method) to the output signal of the subtracter 90 when the currently read recording medium is the CD 10 (Tracking error signal by the differential push-pull method) of the subtracter 102 and supplies the selected signal to the tracking servo circuit (control means) through the amplifier 92. [ (93).

The tracking servo circuit 93 controls the tracking actuator 94 in accordance with the tracking error signal to move the objective lens 44 in the direction perpendicular to the track so that laser light is irradiated onto the track of the information recording layer .

Next, the operation of discriminating the recording medium reproduced by the apparatus shown in Fig. 29 will be described.

First, the return light of the reading laser light of the record information is received by the four regions A, B, C, and D of the light receiving unit 61-1 and converted into the electric signals a, b, c, and d, respectively. The sum (a + b + c + d) of the electric signals of the electric signals is calculated by the adders 71, 72 and 73 and the intensity of the returned light is supplied to the smoothing circuit 76 through the amplifier 74 .

The smoothing circuit 76 smoothes the supplied signal and outputs it to the comparison circuit 77. Since the level of the signal after smoothing at the time of reading the DVD is about three times that at the time of CD reading, the comparison circuit 77 compares the signal after smoothing with a predetermined reference value (level of the signal after smoothing at the time of reading the CD, For example, a positive signal when the recording medium currently being read is the DVD 20, and a negative signal when the recording medium is the CD 10, And outputs a signal.

Next, the operation of the focus servo in the present embodiment shown in Fig. 29 will be described.

The four regions A, B, C, and D of the light receiving unit 61-1 convert the received return light into electric signals a, b, c, and d. Next, the sum (b + d) of the outputs of the regions B and D and the sum (a + c) of the outputs of the regions A and C are calculated by the adders 71 and 72, ((B + d) - (a + c)) is calculated. Then, the result is outputted to the focus servo circuit 86 through the amplifier 85 as a focus error signal.

When the shape of the spot of the return light irradiated to the light receiving portion 61-1 is a circle, the focus error signal supplied to the focus servo circuit 86 becomes zero (zero). The focus error signal supplied to the focus servo circuit 86 becomes a positive predetermined level when the shape of the spot of the return light irradiated to the light receiving portion 61-1 is an ellipse having long sides in the directions of the regions B and D, When the shape of the spot of the return light is an ellipse having long sides in the directions of the areas A and C, the focus error signal becomes a negative predetermined level.

The focus servo circuit 86 controls the focus actuator 87 in correspondence with the sign and level of the focus error signal so that the objective lens 44 is moved in the optical axis direction so that the spot of the return light on the light- .

Thus, by comparing the amount of light detected in the areas B and D of the light receiving unit 61-1 with the amounts of light detected in the areas A and C according to the principle of the astigmatism method, the direction and amount of the focus error can be detected, Accordingly, the objective lens 44 is moved to perform focus servo control.

Next, the operation of the tracking servo in this embodiment shown in Fig. 29 will be described.

The light receiving portions 61-2 and 61-3 convert the amounts of return light received in the regions E and F and the regions G and H into electric signals e, f and g and h, respectively, . (E + f) and (g + h) added by the adders 88 and 89 are supplied to the subtractor 90. The subtractor 90 subtracts the difference (e + f) - (g + h)), and outputs it to the changeover switch 91 as a tracking error signal by the 3-beam method.

The subtracters 98 and 99 subtract the difference (ef and gh) of the amount of return light received from the areas E and F of the light-receiving units 61-2 and 61-3 and the areas G and H .

The regions B and C of the light receiving section 61-1 output the electric signals b and c converted from the received light quantity of received light to the adder 96 and the areas A and D of the light receiving section 61-1 are the light quantity To the adder 95. The adder 95 adds the electric signals a and d. These adders 95 and 96 calculate the sum ((b + c), (a + d)) of the electric signals of the regions B and C or the regions A and D respectively and outputs them to the subtractor 97 Output.

The subtracter 97 calculates the difference (b + c) between the sum (b + c) of the electric signals of the regions B and C in the light receiving unit 61-1 and the sum (a + d) + c) - (a + d), and outputs it to the subtractor 102. [

The subtracter 98 calculates the difference ef between the light quantity of the area E in the light receiving section 61-2 and the light quantity of the area F and outputs the difference ef to the adder 100. The subtracter 99 receives the difference ef from the light receiving section 61 -3) and the light amount of the area H and outputs the difference gh to the adder 100. The adder 100 adds the sum (ef + (gh) And outputs it to the amplifier 101.

The amplifier 101 amplifies a signal supplied at a predetermined gain K and outputs the amplified signal K ((e-f) + (g-h)) to the subtractor 102.

The subtracter 102 subtracts the difference between the output ((b + c) - (a + d)) of the subtractor 97 and the output signal K ((ef) + (gh) and outputs the result as a tracking error signal by the differential push-pull method to the change-over switch 91. In this case, the difference ((b + c) - (a + d) do.

On the other hand, as described above, the output signal of the comparison circuit 77 is supplied to the changeover switch 91. The changeover switch 91 selects the output of the subtractor 102 (tracking error signal by the differential push-pull method) when the output of the comparison circuit 77 is positive (when the recording medium is a DVD) To the tracking servo circuit 93. [

On the other hand, when the output of the comparing circuit 77 is negative (when the recording medium is CD), the changeover switch 91 selects the output of the subtractor 90 (tracking error signal by the 3-beam method) (92) to the tracking servo circuit (93).

The tracking servo circuit 93 controls the tracking actuator 94 in accordance with the supplied tracking error signal so as to move the objective lens 44 in an appropriate position and in a direction perpendicular to the optical axis.

In this manner, the objective lens 44 is controlled to perform the tracking servo, so that laser light is always irradiated on a predetermined track to obtain good return light.

Next, the operation of reading recorded information in this embodiment will be described.

As described above, the return light of the laser light for data reading is received by the four regions A, B, C, and D of the light receiving unit 61-1 and converted into electric signals a, b, c, and d, respectively. The sum (a + b + c + d) of the electric signals of the electric signals is calculated by the adders 71, 72 and 73, , ≪ / RTI >

The equalizer 75 equalizes the signal supplied through the amplifier 74 with the equalizing characteristic corresponding to the recording medium in accordance with the output of the comparing circuit 77 and outputs the equalized signal to the binarizing circuit 78 . The binarizing circuit 78 performs a predetermined correction on the signal and outputs it to the demodulation / ECC circuit 79 and the PLL circuit 80 as binarized data.

The PLL circuit 80 generates a clock of a frequency according to the type of recording medium according to the output of the comparison circuit 77 from the output of the binarization circuit 78 and outputs it to the demodulation / ECC circuit 79. The demodulation / ECC circuit 79 performs error correction of the signal read from the recording medium in accordance with the clock supplied from the PLL circuit 80, and demodulates the binarized data. When the recording medium is CD, the demodulated / ECC circuit 79 supplies the demodulated audio signal to the processing circuit 81. When the recording medium is the DVD, the demodulated image signal and audio signal are supplied to the processing circuit 81 .

The processing circuit 81 outputs the supplied audio signal to the speaker 82 and outputs the image signal to the CRT 83 when the image signal is also supplied.

In this way, the CD and DVD data are read, and subjected to a predetermined equalizing process, correction, and error correction. Then, the read data is demodulated and reproduced by the speaker 82 and the CRT 83.

As described above, data is selectively read from the CD 10 or the DVD 20 while the focus servo and the tracking servo are performed, and the image and audio are reproduced and output.

The shape of the light receiving portion 61-1 of the photodiode may be a tetragonal shape as shown in Fig. 30A as well as a shape of a substantially octagonal shape as shown in Fig. 25B. In addition, as shown in Fig. 30B, in order to detect such light in correspondence with the shape of unnecessary light (for example, light of NA 0.4 or more) as shown in Fig. 24, a hexagonal- Or may be circular as shown in Fig. 30C.

In the embodiment of Fig. 29, the tracking control is performed by the 3-beam method or the differential push-pull method, but it is also possible to perform the tracking control by the phase difference (Differential Phase Detection (DPD)) method. 31, the outputs of the regions A and C are added by the adder 72 among the four divided regions A to D of the light receiving unit 61-1, and the outputs of the regions B and D are supplied to the adder 71). The phases of the outputs of the adders 71 and 72 are compared by the phase comparator 101 and the phase error signal can be used as the tracking error signal.

According to the phase difference method, since the tracking error signal can be generated only by the reflected light from the information reproducing laser beam spot, the tracking spot, and thus the light receiving portions 61-2, 61-3, the changeover switch 91, . Therefore, the output of the phase comparator 101 can be output to the amplifier 92 as it is.

The principle of generation of the tracking error signal by the phase difference method is disclosed in, for example, Japanese Patent Application Laid-Open No. 5 (1993) -800535.

When the tracking error signal is generated by the phase difference method and the focus error signal is generated by the astigmatism method in this manner, both the CD 10 and the DVD 20 The tracking control and the focus control of the recording information of the optical disc 1 can be realized.

As described above, in order to actually reproduce information from the CD 10 and the DVD 20, it is necessary not only to receive reflected light of a predetermined level with a small aberration, but also to meet other conditions.

For example, as shown in FIG. 32, when the CD is reproduced, jitter changes when the normalized detector size is changed.

32, the focus control is performed by the astigmatism method, and the tracking control is performed by the phase difference method to show how the jitter changes when the normalized detector size is changed. 32. The solid line in FIG. 32 shows the calculated values of the simulation processing by the computer, and the circle indicates experimental values.

As shown in Fig. 32, if the size of the normalized detector is made too large, as described above, light containing a large amount of aberration (light with a large NA) is received, and jitter increases.

If the size of the normalized detector is too small, it is difficult to always form a spot of reflected light at a predetermined position on the light receiving unit due to tracking control, focus control, attachment accuracy, etc., The jitter increases.

If the jitter is larger than 8%, it becomes difficult to substantially reproduce the data, so it is preferable to set the jitter to 8% or less. Thus, for example, in order to suppress the jitter to 8% or less, the normalized detector size should be about 16 탆 or less and at the same time about 1.8 탆 or more.

In order to suppress the jitter value to 7% or less, it is preferable that the normalized detector size is about 14 탆 or less, and more preferably about 2 탆 or more.

However, as shown in FIG. 32, when the normalized detector size is set to a value in the vicinity of 2 占 퐉, the jitter increases rapidly even if there is some unevenness in the normalized detector size. Thus, from a practical point of view, it is preferable to set the normalized detector size to 4 탆 or more.

It is also assumed that the RF signal (the sum of the outputs of the regions A to D of the light-receiving portion 61-1 in Fig. 29) when the normalized detector size is changed and the change of the focus error signal by the astigmatism method The results are shown in FIG. 33 to FIG. 38 by simulation.

33 to 36 show changes in the RF signal and the focus error signal when the CD is reproduced by a normalized detector size photodiode having a size of 16 mu m, 10 mu m, 4 mu m, or 2 mu m, respectively, And FIG. 38 show changes in the RF signal and the focus error signal when the DVD is reproduced by a photodiode having a normalized detector size of 6 占 퐉 or 8 占 퐉.

33, when the normalized detector size is set to 16 占 퐉 at the time of CD reproduction, the so-called S curve characteristic of the focus error signal is not obtained (particularly, in the positive polarity range, Shaped grooves) are formed), making it difficult to perform stable focus servo.

On the other hand, as shown in Fig. 34, when the normalized detector size is set to 10 mu m, the positive level of the focus error signal becomes large to some extent, and practically, the characteristic capable of operating the focus servo can be obtained.

In addition, as shown in Fig. 35, when the normalized detector size is 4 mu m, a comparatively clear S curve characteristic of the focus error signal can be obtained. On the other hand, as shown in Fig. 36, when the normalized detector size is 2 mu m, the S curve characteristic of the focus error signal is confused.

From the above facts, when reproducing the CD 10, in order to satisfy the S-characteristic of the focus error signal, the normalized detector size is set to 15 mu m as a value smaller than 16 mu m, Preferably 14 mu m, and more preferably 10 mu m or less. Conversely, the lower limit value is preferably 3 m, more preferably 4 m, larger than 2 m.

On the other hand, when the S curve characteristic of the focus error signal in the case of reproducing the DVD 20 is observed, as shown in Fig. 38, when the normalized detector size is 8 mu m, a clear S curve characteristic is obtained . On the other hand, when the normalized detector size is 6 占 퐉, a dead zone (a portion with a small slope) is generated in the vicinity of the zero cross point as shown in Fig.

From this fact, when reproducing the DVD 20, it is preferable to set the normalized detector size to a value larger than 7 mu m, preferably 8 mu m or more, in order to obtain an S curve characteristic of a good focus error signal.

In summary, in the case of reproducing the information recorded in the information recording layer from the output of the light receiving section, the normalized detector size is about 1.8 탆 to about 16 Mu] m. Particularly, from a practical viewpoint, it is preferable that the normalized detector size is in the range of about 4 탆 to 14 탆. In order to obtain a sufficient amount of light at the time of reproduction of the DVD 20, it is preferable to be 10 mu m or more.

From the viewpoint of obtaining a good S-shaped characteristic of the focus error signal of the CD 10 when generating a focus error signal from the output of the light receiving section, the normalized detector size is in the range of 3 탆 to 15 탆 And more preferably in the range of 4 탆 to 14 탆.

From the viewpoint of obtaining a good S-shaped characteristic of the focus error signal when reproducing the DVD 20, the normalized detector size is preferably 7 占 퐉 or more, and preferably 8 占 퐉 or more.

In the case of obtaining both the RF signal (information reproduction signal) and the focus error signal from the output of the light receiving section, the normalized detector size is a condition for obtaining the reproduction signal and a condition for obtaining the focus error signal It is sufficient to satisfy both of them. That is, it is preferable to set the normalized detector size in the range of 8 탆 to 14 탆.

While the present invention has been described with respect to the case where the two types of discs of CD and DVD are selectively reproduced, the present invention can be applied to a case of reproducing discs of more types (three or more) It can also be applied to the case of reproducing a medium. Further, the present invention can be applied not only to the case where the record information is reproduced but also when the record information is recorded.

According to the present invention, the optical pick-up apparatus selectively reproduces a plurality of recording media having substrates of different thicknesses, which makes it unnecessary to mechanically change parts and can be used even in a place with a lot of vibration, . In addition, it is possible to reduce the size and cost of the apparatus.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It will be understood that various modifications and changes may be made without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing a configuration example of a conventional optical pickup device for a compact disc (CD). Fig.

2 is a cross-sectional view showing a configuration example of a conventional optical pickup device for a digital video disk (DVD).

3 is a sectional view showing an embodiment in which the configuration example of FIG. 2 is applied to a CD.

4 is a cross-sectional view showing a configuration example of a conventional optical pickup device for both CD and DVD.

5 is a cross-sectional view showing an embodiment in which the configuration example of FIG. 4 is applied to a CD.

6 is a sectional view showing a configuration example of an embodiment of an optical pickup device of a recording medium recording and reproducing apparatus of the present invention.

Fig. 7 is a diagram showing an example of light ray tracing of return light in the embodiment of Fig. 6; Fig.

8 is a diagram showing a relationship between an increase in thickness of a substrate of a recording medium and a distance from a Gaussian plane of a predetermined point.

Fig. 9 is a diagram showing an example of intensity distribution of return light when the embodiment of Fig. 6 is applied to a DVD. Fig.

10 is a view showing an example of characteristics of spherical aberration when the embodiment of Fig. 6 is applied to a DVD. Fig.

11 is a diagram showing an example of MTF (Modulation Transfer Function) characteristics when the embodiment of Fig. 6 is applied to DVD. Fig.

Fig. 12 is a view showing an example of intensity distribution of return light when the distance from the Gaussian plane when the embodiment of Fig. 6 is applied to CD is 0 mu m; Fig.

Fig. 13 is a view showing an example of intensity distribution of return light when the distance from the Gaussian plane when the embodiment of Fig. 6 is applied to CD is 4.0 m. Fig.

14 is a view showing an example of the intensity distribution of return light when the distance from the Gaussian plane when the embodiment of Fig. 6 is applied to CD is 8.0 mu m.

FIG. 15 is a view showing an example of intensity distribution of return light when the distance from the Gaussian plane when the embodiment of FIG. 6 is applied to CD is 10 μm; FIG.

Fig. 16 is a view showing an example of the intensity distribution of the return light when the distance from the Gaussian plane when the embodiment of Fig. 6 is applied to CD is 12 占 퐉. Fig.

Fig. 17 is a view showing an example of the intensity distribution of the return light when the distance from the Gaussian plane when the embodiment of Fig. 6 is applied to CD is 16 mu m; Fig.

Fig. 18 is a view showing an example of the intensity distribution of the return light when the distance from the Gaussian plane when the embodiment of Fig. 6 is applied to CD is 24 m; Fig.

Fig. 19 is a view showing an example of characteristics of spherical aberration when the embodiment of Fig. 6 is applied to CD; Fig.

FIG. 20 shows an example of MTF characteristics when the embodiment of FIG. 6 is applied to a CD; FIG.

FIG. 21 is a view showing an example of characteristics of spherical aberration when the embodiment of FIG. 6 is applied to a CD. FIG.

FIG. 22 is a diagram showing an example of MTF characteristics when the embodiment of FIG. 6 is applied to a CD; FIG.

23 is a view showing an example of a normalized photodetector size in the embodiment of Fig. 6;

24 is a view showing a relationship between a normalized photodetector size and a range of return light;

25A to 25C are diagrams showing a configuration example of a photodiode in the embodiment of Fig.

26 is a cross-sectional view showing an embodiment in which the embodiment of FIG. 6 is applied to a CD;

FIG. 27 is an enlarged view showing an example of a position of irradiation (irradiation) of a laser beam at the time of reading a CD. FIG.

28 is an enlarged view showing an example of the irradiation position of a laser beam at the time of reading a DVD.

29 is a block diagram showing an example of an electrical configuration of an embodiment of the recording medium recording and reproducing apparatus of the present invention.

30A to 30C are views showing examples of other shapes of the light-receiving portion in the embodiment of Fig. 29;

31 is a block diagram showing a configuration for generating a tracking error signal by a phase difference method;

32 is a diagram showing a change in jitter when the normalized detector size is changed in the case of reproducing a CD.

Fig. 33 is a diagram showing characteristics of a focus error signal and an RF signal at the time of CD reproduction when the normalized detector size is set to 16 mu m. Fig.

34 is a diagram showing the characteristics of a focus error signal and an RF signal at the time of CD reproduction when the normalized detector size is 10 mu m.

Fig. 35 is a diagram showing characteristics of a focus error signal and an RF signal at the time of CD reproduction when the normalized detector size is 4 mu m. Fig.

36 is a view showing characteristics of a focus error signal and an RF signal at the time of CD reproduction when the normalized detector size is 2 mu m.

37 is a view showing characteristics of a focus error signal and an RF signal at the time of DVD reproduction when the normalized detector size is set to 6 mu m.

FIG. 38 is a diagram showing the characteristics of a focus error signal and an RF signal at the time of DVD reproduction when the normalized detector size is 8 μm; FIG.

Description of the Related Art

1: Laser diode (LD) 2: Grating 3: Beam splitter 4: Object lens 5: Photodiode (PD) 10: Compact disc (CD) A laser diode (LD) is a laser diode (LD). The laser diode (LD) is a laser diode (LD). The laser diode And a photodetector (PD) 61-1, 61-2, 61-3: a light receiving portion, a light receiving portion, and a beam splitter. The present invention relates to a focus servo circuit and a focus servo circuit, and more particularly, to a focus servo circuit, a focus servo circuit, and a focus servo circuit, , 87: focus actuator, 91: changeover switch, 93: tracking servo circuit, 94: tracking actuator, 101: phase comparator.

Claims (22)

A first recording medium having an information recording layer on a substrate having a first thickness and a recording medium for selectively recording or reproducing information on a second recording medium having an information recording layer on a substrate having a second thickness, In the medium recording and reproducing apparatus, Generating means for generating light for irradiating the information recording layer of the first or second recording medium, Irradiating means for converging light from the generating means to irradiate the information recording layer of the first or second recording medium, and And light receiving means for receiving return light from the information recording layer of the first or second recording medium, Wherein the light receiving means has a normalized detector size of 3 占 퐉 or more and 16 占 퐉 or less. The recording medium according to claim 1, wherein the normalized size based on the magnification (magnification) of the irradiating means of the light receiving means is 4 m or more. The recording medium according to claim 2, wherein the light receiving means outputs a focus servo signal. The recording medium according to claim 1, wherein the normalized size of the light receiving means on the basis of the magnification of the irradiating means is 14 μm or less. The recording medium according to claim 4, wherein said light receiving means outputs a focus servo signal. The recording medium according to claim 1, wherein the normalized size of the light receiving means on the basis of the magnification of the irradiating means is 8 占 퐉 or more. The recording medium according to claim 6, wherein said light receiving means outputs a focus servo signal. The recording medium according to claim 1, wherein the normalized size of the light receiving means on the basis of the magnification of the irradiating means is 10 m or more. The recording medium according to claim 8, wherein the light receiving means outputs a reproduction signal from the information recording layer of the first or second recording medium. The recording medium according to claim 1, wherein the size normalized based on the magnification of the irradiating means of the light receiving means is 8 탆 or more and 14 탆 or less. The recording medium according to claim 10, wherein said light receiving means outputs a focus servo signal and a reproduction signal from an information recording layer of said first or second recording medium. The recording medium according to claim 1, wherein the normalized size of the light receiving means based on the magnification of the irradiating means is 10 占 퐉 or more and 14 占 퐉 or less. The recording medium according to claim 12, wherein said light receiving means outputs a focus servo signal and a reproduction signal from an information recording layer of said first or second recording medium. The recording medium according to claim 1, wherein the recording density of the first recording medium is larger than the recording density of the second recording medium. The method according to claim 1, Discrimination means for discriminating between the first recording medium and the second recording medium, Further comprising equalizing means for equalizing the output of the light receiving means with different characteristics in the case of reproducing the first recording medium and the case of reproducing the second recording medium in correspondence with the discrimination result of the discriminating means And the recording medium is recorded on the recording medium. 16. The recording medium according to claim 15, wherein the discriminating means discriminates the first recording medium and the second recording medium from the level of the output of the light receiving means. The method according to claim 1, Discrimination means for discriminating between the first recording medium and the second recording medium, And control means for controlling the irradiating means by a different tracking control method in the case of reproducing the first recording medium and the case of reproducing the second recording medium in correspondence with the discrimination result of the discriminating means Wherein the recording medium is a recording medium. A light source for generating light to be irradiated to the information recording layer of the first or second recording medium through the substrate; a light source for irradiating the information recording layer of the first or second recording medium And a light receiving means for receiving return light from the information recording layer of the first or second recording medium, the optical pickup device having the information recording layer with the first thickness A recording medium recording and reproducing method for selectively recording or reproducing information on a first recording medium or a second recording medium having an information recording layer on a substrate of a second thickness thicker than the first thickness , And receiving the return light from the information recording layer with the light receiving means having a size of the normalized detector of 3 탆 or more and 16 탆 or less. A first recording medium having an information recording layer on a substrate having a first thickness and a recording medium for selectively recording or reproducing information on a second recording medium having an information recording layer on a substrate having a second thickness, In the medium recording and reproducing apparatus, Generating means for generating light to be irradiated on the information recording layer of the first or second recording medium, Irradiating means for irradiating the light from the generating means to the information recording layer of the first or second recording medium, And light receiving means for receiving return light from the information recording layer of the first or second recording medium, Wherein the light receiving means is arranged so that the normalized detector size is larger than the diameter of the spot on the light receiving means of the return light when the _first numerical aperture from the first recording medium is N ₁ , 2 is smaller than the diameter of the spot of light on the light-receiving means of the return light when the numerical aperture of the recording medium is larger than N ₂ . The recording medium according to claim 19, wherein the first numerical aperture N ₁ is 0.6 and the second numerical aperture N ₂ is 0.3. 20. The recording medium according to claim 19, wherein the normalized detector size is a normalized size ranging from 10 m to 16 m by dividing the length of the light receiving means by the magnification of the irradiating means. A light source for generating light to be irradiated to the information recording layer of the first or second recording medium through the substrate; a light source for irradiating the information recording layer of the first or second recording medium And a light receiving means for receiving return light from the information recording layer of the first or second recording medium, the optical pickup device comprising: a substrate having a first thickness; 1. A recording medium recording and reproducing method for selectively recording or reproducing information on a second recording medium having an information recording layer on a first recording medium or a substrate having a second thickness larger than the first thickness, Wherein the normalized detector size is larger than the diameter of the spot on the light receiving means of the return light when the _first numerical aperture from the first recording medium is N ₁ and the second aperture from the second recording medium Receiving light from said information recording layer by said light receiving means which is smaller than the diameter of a spot of light on said light receiving means of return light when the number is larger than N ₂ .