JP3408016B2 - Disc thickness discrimination device for optical recording media - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus for an optical recording medium such as a compact disc (CD), a mini disc (MD), a laser disc (LD) which is an optical disc, and more particularly to an optical recording medium. The present invention relates to a disc thickness discriminating device.

[0002]

2. Description of the Related Art As a conventional technique of this kind, Japanese Patent Laid-Open No. 6-25
The technology of the recording / reproducing apparatus for an optical recording medium disclosed in Japanese Patent Publication No. 9804 can be mentioned.

In this technique, first and second light sources, a laser beam synthesizing means for synthesizing laser beams from the respective light sources into substantially the same optical path, and a laser beam from the first light source for the first optical disk are used. From the first and second optical discs, a converging light source system for converging light and converging laser light from the second light source for the second optical disc having a disc substrate thickness different from that of the first optical disc It is composed of a photodetector that receives the reflected light of the.

As a result, two disc substrates having different thicknesses are formed.
A thin optical disc that can support various types of optical discs and has a higher density by increasing the numerical aperture of the objective lens.
Recording / reproduction can be performed on a conventional 1.2 mm optical disc, and a single optical head can achieve high density without sacrificing compatibility, which enables downsizing and cost reduction.

[0005]

A conventional recording / reproducing apparatus for an optical recording medium of this type is, specifically, an independent optical system of two systems having an objective lens and a quarter wavelength plate in common. It has two types of optical discs with different disc substrate thicknesses. At this time, the disc substrate thicknesses of the two different types of optical discs are determined, and which of the two optical systems is to be selected is determined. There is a need to.

However, there is no disclosure of a technique for discriminating the disc substrate thicknesses of two different types of optical discs, and it is until the reproduction of two types of optical discs having different disc substrate thicknesses by one optical head. .

A technique for reproducing the disc substrate thicknesses of two different types of optical discs with one optical head is as follows.
JP-A-5-303766, JP-A-6-21540
Although the technology disclosed in Japanese Patent No. 6 can be mentioned, none of them has the ability to discriminate the disc substrate thicknesses of two different types of optical discs.

Therefore, an object of the present invention is to provide a disc thickness discriminating apparatus for an optical recording medium, which is easy to discriminate optical discs having different thicknesses.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention splits a laser beam focused and irradiated onto an optical recording medium into a 0th-order beam and a ± 1st-order beam by a diffraction grating.
Beam, the reflected light of the 0th order beam is received by a primary element to derive a reproduction signal, and the reflected light of the ± 1st order beam is received by a secondary element and a tertiary element to obtain a tracking signal. In the reproducing apparatus for the optical recording medium, the output level of the reproduction signal of the primary element is based on the output levels of the secondary element and the tertiary element at the timing when the output level of the reproduction signal of the primary element becomes substantially the peak value in the focus pull-in operation. The thickness of the substrate of the optical storage medium is identified.

Further, according to the present invention, the laser light focused and irradiated onto the optical recording medium is split into three beams by a diffraction grating into a 0th order beam and ± 1st order beams, and the reflected light of the 0th order beam is the first beam. In a reproducing apparatus for an optical recording medium, a secondary element receives light to derive a reproduction signal, and a secondary element and a tertiary element receive reflected light of the ± first-order beams to derive a tracking signal. In operation, the thickness of the substrate of the optical storage medium is identified based on the signals of the secondary element and the tertiary element at the timing when the output level of the autofocus signal is substantially zero cross.

Furthermore, in the present invention, the secondary element and the tertiary element are divided into a plurality of portions in a direction substantially orthogonal to the track direction, and the light is divided based on the output level difference of the plurality of divided light receiving elements. It is characterized in that the thickness of the substrate of the storage medium is identified.

Further, in the present invention, the output levels of the secondary element and the tertiary element are compared with a reference level,
The thickness of the substrate of the optical storage medium is identified.

Further, in the present invention, the timing at which the output level of the reproduction signal of the primary element reaches a substantially peak value is the timing of focus detection in focus control.

Further, in the present invention, the optical recording medium is an optical disk having a disk substrate thickness of 0.6 mm and 1.2 mm.
The optical recording medium according to any one of 1.

[0015]

[0016]

According to the first aspect of the present invention, the laser beam focused and irradiated onto the optical recording medium is split into three beams by the diffraction grating into the 0th order beam and the ± 1st order beams, and the reflected light of the 0th order beam is the first beam. The secondary element receives the light to derive a reproduction signal, and the reflected light of the ± first-order beams is received by the secondary element and the tertiary element to derive the tracking signal. Moreover, in the focus pull-in operation, the thickness of the substrate of the optical storage medium is identified based on the output levels of the secondary element and the tertiary element at the timing when the output level of the primary element reaches a substantially peak value. .

According to a second aspect of the present invention, the laser light focused and irradiated onto the optical recording medium is combined with the 0th-order beam ± 1 by the diffraction grating.
The primary beam is split into three beams, and the reflected light of the zero-order beam is received by the primary element to derive a reproduction signal.
The reflected light of the ± first-order beams is received by the secondary element and the tertiary element to derive the tracking signal. Moreover, during the focus pull-in operation, the thickness of the substrate of the optical storage medium is identified based on the output levels of the secondary element and the tertiary element at the timing when the output level of the autofocus signal becomes substantially zero cross.

According to a third aspect of the present invention, the secondary element and the third element according to the first aspect or the second aspect are divided into a plurality of portions in a direction orthogonal to the substantially track direction, and the plurality of divided light receiving portions are provided. The position of the spot focused on the optical recording medium is determined based on the output level difference of the element, and the thickness of the substrate of the optical storage medium is identified.

In a fourth aspect of the present invention, the output levels of the secondary element and the third element according to the first aspect or the second aspect are compared with a reference level, and the reference level is focused on an optical recording medium. The thickness of the substrate of the optical storage medium is identified by comparing the output level of the secondary element and the tertiary element with the reference level as the signal level of the boundary point according to the spot position. .

According to a fifth aspect of the present invention, the timing at which the output level of the primary element according to any one of the first to fourth aspects becomes a substantially peak value is the timing of focus detection in focus control. , Based on the focal position.

In a sixth aspect, the optical recording medium according to any one of the first to fifth aspects is an optical disc having a substrate thickness of 0.6 mm and 1.2 mm.

[0022]

[0023]

EXAMPLES Examples of the present invention will be described below.

It should be noted that, in the drawings, the same reference numerals and symbols indicate the same or corresponding components, and therefore, duplicated description will be omitted.

FIG. 1 is a block diagram showing an optical system pickup portion having a substrate thickness of 0.6 mm in a disc thickness discriminating apparatus for an optical recording medium according to an embodiment of the present invention. In addition, FIG.
Is an explanatory view showing a photodetector in a state of reproducing a disc having a designed disc thickness in a reproducing apparatus of an optical recording medium,
FIG. 2B is an explanatory view showing the photodetector in the state of reproducing a disc that does not match the designed disc thickness in the reproducing apparatus of the optical recording medium, and FIG. 2C is a disc thickness discrimination of the optical recording medium of this embodiment. It is explanatory drawing which shows the photodetector in an apparatus.

The disc thickness discriminating apparatus for an optical recording medium according to this embodiment includes a pickup for reproducing a high density disc standardized with a substrate thickness of 0.6 mm, a substrate thickness of 1.
A pickup for reproducing a high-density disc standardized by 2 mm is provided, and these two pickups are selectively driven according to the respective standards to enable reproduction of discs of any standard. It is a thing. The basic configuration of the optical system is common, and only a pickup designed for a substrate thickness of 0.6 mm as one optical system will be described.

A disc thickness discriminating apparatus for an optical recording medium, which is composed of a pickup designed for a substrate thickness of 0.6 mm, of the present embodiment is constructed as follows.

As shown in FIG. 1, the semiconductor laser 8 has 63
A laser beam of 5 (tolerance ± 15) nm is output. The diffraction grating plate 7 splits the light into three beams of 0th order light and ± 1st order light. The polarization beam splitter 6 allows the laser light from the semiconductor laser 8 to pass therethrough and totally reflects the reflected light from the disk substrate 2. The λ / 4 plate 5 makes linearly polarized light into circularly polarized light, and the laser beam converted into parallel light by the collimator lens 4 is focused by the objective lens 1 on the recording surface 3 of the disk. The detection lens 9 is a single lens or a plurality of lenses that focus the laser light on the photodetector 10.

As shown in FIG. 2C, the photodetector 10 has a first light receiving element 20 (4) that receives the 0th order light by dividing it into four.
Each of the divided first light receiving elements is indicated by 11, 12, 13, and 14) and the second inner light receiving element 15A for receiving the ± 1st order light.
And second outer light receiving element 15B, third inner light receiving element 16A
And a third outer light receiving element 16B.

The entire disc thickness discriminating apparatus for the optical recording medium of the present embodiment thus constructed operates as follows.

The laser light emitted from the semiconductor laser 8 having a wavelength of 635 (tolerance ± 15) is 0 at the diffraction grating plate 7.
The light is split into three beams of secondary light and ± first-order light, and is incident on the disc substrate 2 having a thickness of 0.6 mm through the polarization beam splitter 6, the λ / 4 plate 5, the collimator lens 4 and the objective lens 1, and the recording thereof. The surface 3 is focused and illuminated. On the recording surface 3, the condensed 0th order light is at the center of the recording track, and
The collected ± 1st order lights are radiated at positions slightly deviated on both sides of the recording track.

The laser light reflected from the recording surface 3 is separated by the polarization beam splitter 6 through the objective lens 1, the collimator lens 4 and the λ / 4 plate 5, and the detection lens 9 is used.
The light is collected by the photodetector 10 via.

Next, with respect to the operation of the photodetector 10, the technique of the conventional photodetector 10 and the technique of the photodetector 10 of this embodiment will be described in detail with reference to FIG.

As shown in FIGS. 2 (a) and 2 (b), the conventional photodetector 10 has a first light receiving element 20 (11, 12, 13, 14) and the second light receiving element 15 and the third light receiving element 16 which receive the ± 1st order light. First light receiving element 20 (11, 1
2, 13, 14) four-division light reception output is appropriately calculated and converted into an autofocus signal for performing autofocus control or a reproduction signal proportional to the light reception output level. Similarly, the second light receiving element 15 and the third light receiving element 1
The received light output obtained from 6 is used for tracking control for accurately tracing the laser light along a predetermined track.

FIG. 2A shows a state in which a disc having a design disc thickness is reproduced. When reproducing a disc having a design disc thickness, the first light receiving element 20 is used.
Main beam MB at the center of (11, 12, 13, 14)
Is located, and the four-divided light receiving output is the first light receiving element 20.
Assuming that each of the four light reception outputs of (11, 12, 13, 14) is I1, I2, I3, I4, the autofocus signal IF is expressed by IF = (I1 + I3)-(I2 + I4), IF = 0 at the focal point.

At this time, the first light receiving element 20 (1
1, 12, 13, 14) reproduction signal IS consisting of the sum of
Is expressed as IS = I1 + I2 + I3 + I4, and if IF = 0, then IS = Max.

The auto-tracking signal It is ±
Second light receiving element 15 and third light receiving element 1 for receiving the primary light
When the sub-beam SB is located at the center of 6 and the tracking signals thereof are I15 and I16, it is expressed as It = I15-I16, and when It = 0, it traces accurately along a predetermined track. It becomes a state.

Here, how the laser light L is incident on the disk substrate 2 through the objective lens 1 and is focused on the recording surface 3 formed on one surface of the disk substrate 2 will be described.

FIG. 3 is an explanatory view schematically showing how the laser light is incident on the disk substrate through the objective lens and is condensed at one point on the recording surface formed on the disk substrate, and FIG. FIG. 3 is an explanatory diagram schematically showing a state in which laser light is incident on a disk substrate via an objective lens and cannot be condensed at one point on a recording surface formed on the disk substrate. Also, FIG.
FIG. 3 is an explanatory diagram showing that even if the position of the objective lens is changed even slightly, the reflected beam path of the ± first-order light is changed to change the focal point in the photodetector.

As shown in FIG. 2A, when reproducing a disc that matches the designed disc thickness, as shown in FIG. 3, the thickness of the disc substrate 2, which is a recording medium, the wavefront aberration, the laser wavelength, etc. are considered. Designed to be 0.6mm
Laser light L having a wavelength of 635 nm on the disk substrate 2 of
Numerical aperture designed to irradiate the recording surface 3 with light.
The objective lens 1 of the pickup 6 can focus the laser light L on one point on the recording surface 3 only under the above-mentioned setting conditions.

However, when the thickness of the disk substrate 2 is doubled to 1.2 mm, theoretically, the recording surface 3
Even if the objective lens 1 is arranged at a position where the laser light L will be condensed on the recording surface 3 of the disk substrate 2,
Do not concentrate on FIG. 4 is a diagram schematically showing this state. The point where the laser light L is most concentrated due to the wavefront aberration of the laser light L indicates that the laser light L is displaced from the recording surface 3 toward the objective lens 1 side by α. That is, when the thickness of the disk substrate 2 becomes thicker than the design value, the effective focal point position where the reproduction signal level becomes maximum is the theoretical focal point position from the original focal point position. Move a certain distance to the side. Therefore, when reproducing the disc substrate 2 thicker than the designed value, if the focus control is performed so that the reproduction signal level is maximized, the objective lens 1 is moved from the original position to the disc substrate 2
It is kept in a position slightly close to. For example, the current 0.6
When reproducing the current 1.2 mm-standard disk substrate 2 by using the objective lens 1 designed for a mm-standard disk, the objective lens 1 must be closer to the surface of the disk substrate 2 by 20 μm from the original position. I won't.

Further, if the objective lens 1 comes close to the disc substrate 2 even slightly, the reflected beam path of the ± first-order light changes,
The focus points of the second light receiving element 15 and the third light receiving element 16 that receive the ± first-order light change.

FIG. 5 schematically shows this change.
The optical path of the reflected beam of the primary light, that is, the sub beam SB is shown. As is clear from the figure, when reproducing the 0.6 mm disk substrate 2, the sub-beam SB passes through the optical path indicated by the solid line. When the 1.2 mm disk substrate 2 is reproduced, the objective lens 1 moves to the disk substrate 2 side as shown by the broken line, and as a result, the sub beam SB passes through the optical path shown by the broken line.

As a result, the sub-beam SB of the reflected beam
Are condensed on the outside of the second light receiving element 15 and the third light receiving element 16. That is, when the 1.2 mm disc substrate 2 is reproduced by using the objective lens 1 designed to reproduce the 0.6 mm disc substrate 2, the sub beams SB of the ± first-order light are emitted from the second light receiving element 15 and the second light receiving element 15. 3 The light is moved to the outer side of the light receiving element 16 by 60 μm and focused and irradiated. At this time, as shown in FIG. 2B, the sub-beam SB is outside the conventional second light receiving element 15 and the third light receiving element 16 and cannot be detected.

Therefore, in this embodiment, the conventional second light receiving element 15 is the second inner light receiving element 15A and the second outer light receiving element 15B, and the conventional third light receiving element 16 is the third inner light receiving element 16A and the third inner light receiving element 16A. The third outer light receiving element 16B is used as the second
Inner light receiving element 15A, second outer light receiving element 15B, third
The light receiving outputs obtained from the inner light receiving element 16A and the third outer light receiving element 16B are I15A, I15B, I16A, and I16B.

Therefore, in the above case, 0.6 mm
When reproducing the disk substrate 2 of, the sub beam SB
Is the second inner light receiving element 15A and the third inner light receiving element 16A
When reproducing the 1.2 mm disc substrate 2, the sub-beam SB is positioned on the second outer light receiving element 15B and the third outer light receiving element 16B.

As a result, the second sub-beam SB is detected.
Inner light receiving element 15A and third inner light receiving element 16A, second
The outer light receiving element 15B and the third outer light receiving element 16B can determine the thickness of the disk substrate 2.

Next, the signal processing of the disc thickness discriminating apparatus for the optical recording medium of this embodiment will be described.

FIG. 6 is a circuit diagram showing a disc thickness signal generating circuit in a disc thickness discriminating apparatus for an optical recording medium for carrying out the present invention. FIG. 7 is a characteristic diagram of the disc thickness signal generating circuit in the disc thickness discriminating apparatus for the optical recording medium of the embodiment of FIG.

As shown in FIG. 2C, the photodetector 10 of this embodiment receives the first-order light by dividing it into four light beams.
Light receiving element 20 (each of the four first light receiving elements divided into 11 and 1
2, 13 and 14) and a second inner light receiving element 15A and a second outer light receiving element 15B for receiving ± 1st order light, a third inner light receiving element 16A and a third outer light receiving element 16B, and
The four-divided light receiving outputs of the light receiving element 20 are I1, I2, I3,
It is I4. The second divided light receiving outputs of the second inner light receiving element 15A and the second outer light receiving element 15B, which receive the ± first-order light, and the third inner light receiving element 16A and the third outer light receiving element 16B,
I15A, I15B, I16A, I16B.

Here, the autofocus signal IF is expressed as follows: IF = (I1 + I3)-(I2 + I4) using the adder circuit 31, the adder circuit 32 and the subtractor circuit 34 as in the conventional case. The reproduced signal IS at this time is: IS = I1 + I2 + I3 + I4 using the adder circuit 31, the adder circuit 32, and the adder circuit 33, that is, each of the first light receiving elements 11, 12, 1 divided into four.
It is represented by the sum of 3,14.

Then, the auto-tracking signal It is
It is expressed by It = (I15A + I15B)-(I16A + I16B) using the adder circuit 41, the adder circuit 42, and the subtractor circuit 43, and when It = 0, traces accurately along a predetermined track. It becomes a state.

Further, the substrate thickness signal Dt is expressed as Dt = (I15B + I16B)-(I15A + I16A) using the adding circuit 44, the adding circuit 45 and the subtracting circuit 46.

Here, the adding circuits 31, 32, 33,
41, 42, 44, 45 and subtraction circuits 34, 43, 46
Is an operational amplifier that adds or subtracts an analog value.

As is known, the reproduction signal IS is added to the adder circuit 3
1 and the adder circuit 32 and the adder circuit 33.
As shown in (a), in relation to the lens position of the objective lens 1, the maximum value is obtained when the recording surface 3 in the disk substrate 2 has the focus of the laser light L. In addition, the auto-tracking signal It is recorded on the recording surface 3 of the disk substrate 2 by the addition circuit 41, the addition circuit 42, and the subtraction circuit 43 in relation to the lens position of the objective lens 1 as shown in FIG. When there is a focus of the laser light L, the zero cross occurs, and the characteristic becomes point symmetric with the zero cross as the center. The autofocus signal IF also has characteristics as shown in FIG. 7 (d).

Here, in the disc thickness discriminating apparatus for the optical recording medium of this embodiment, the disc substrate 2 has a substrate thickness of 0.6 mm.
Since it is designed as a pickup for reproducing a high density disc standardized in 1., as shown in FIG. 7C, the objective lens 1 has a disc substrate surface 2 with a substrate thickness of 0.6 mm and is standardized. When it is near the converted recording surface 3, the output of the substrate thickness signal Dt becomes minimum at the focus position, and even if the objective lens 1 changes from the recording surface 3 of the disk substrate surface 2, the value does not change greatly. However, the objective lens 1
When the disk substrate surface 2 is the recording surface 3 standardized to have a substrate thickness of 1.2 mm, the output of the substrate thickness signal Dt becomes maximum at the focal position, and the objective lens 1 moves as shown in FIG. 7B. Even if the recording surface 3 of the disk substrate surface 2 is slightly changed, the value thereof is largely changed.

It should be noted that the disc thickness discriminating apparatus for the optical recording medium of this embodiment may be designed as a pickup for reproducing a high density disc in which the substrate thickness of the disc substrate 2 is 1.2 mm. The output of the substrate thickness signal Dt becomes maximum at the focal position, and even if the objective lens 1 slightly changes from the recording surface 3 of the disk substrate surface 2, the value thereof changes greatly.

Therefore, the output of the disc thickness signal generating circuit shown in FIG. 6 is used as follows.

FIG. 8 is a circuit diagram of a disc thickness discriminating apparatus for an optical recording medium using the disc thickness signal generating circuit shown in FIG. 6, and FIG. 9 is another circuit diagram using the disc thickness signal generating circuit shown in FIG. It is a circuit diagram of a disc thickness discriminating apparatus of the optical recording medium.

In FIG. 8, the disc thickness discriminating section 50
When the substrate thickness signal Dt and the reproduction signal IS of FIG. 6 are received, and the substrate thickness signal Dt is the peak value of the reproduction signal IS, the substrate thickness of the disc substrate surface 2 is, for example, It is determined whether it is 0.6 mm. When the substrate thickness of the disc substrate surface 2 is 1.2 mm, for example, it has a predetermined peak value as shown in FIG. 7B. At this time, the disc thickness can be discriminated by determining whether the substrate thickness signal Dt has increased above a predetermined threshold value, or whether the peak value is convex upward by the determination of differential or maximum / minimum.

Then, when the output of the substrate thickness signal Dt has the maximum peak value at the focus position, the command section 51 standardizes the optical system of which disc substrate thickness, for example, the substrate thickness is 1.2 mm. The selected optical disc is selected. The optical system switching unit 52 uses a pickup designed for a substrate thickness of 0.6 mm in FIG. 1 when the optical disc is recognized as an optical disc with a substrate thickness of 0.6 mm standardized. If it is recognized as an optical disc standardized by 1.2 mm, the substrate thickness not shown is 1.2 m.
Use a pickup designed for m.

The pickup designed for a substrate thickness of 1.2 mm is basically the same as the configuration shown in FIG.
The photodetector 10 has the configuration shown in FIG.
As described above, since these are publicly known, the description thereof will be omitted.

Further, as is well known, the signal processing section 53 appropriately processes the reproduction signal IS to convert it into a reproduction signal proportional to the light reception output level. The auto-tracking signal It is used for tracking control for accurately tracing the laser light along a predetermined track by the auto-tracking servo. The autofocus signal IF moves the objective lens 1 and is used for autofocus control.

In FIG. 9, the disc thickness discriminating section 60 is
When the substrate thickness signal Dt is a zero cross of the autofocus signal IF, it is determined whether the substrate thickness of the disc substrate surface 2 is, for example, 0.6 mm, depending on whether it is larger than a predetermined threshold value. That is, the disc thickness discriminating unit 50 shown in FIG. 8 and the disc thickness discriminating unit 60 shown in FIG. 9 use the peak value of the reproduction signal IS or the autofocus signal IF as the timing for confirming the value of the substrate thickness signal Dt. The difference is whether to use the zero value of.

Therefore, the disc thickness discriminating portion 60 of FIG.
When the substrate thickness signal Dt is zero cross of the autofocus signal IF, the substrate thickness of the disc substrate surface 2 is, for example, 0.6 mm depending on whether it is larger than a predetermined threshold value.
Or not. When the substrate thickness of the disc substrate surface 2 is 1.2 mm, for example, it has a predetermined peak value as shown in FIG. 7B. At this time, the disc thickness can be discriminated by determining whether the substrate thickness signal Dt has increased above a predetermined threshold value, or whether the peak value is convex upward by the determination of differential or maximum / minimum.

Similarly to the former, when the output of the substrate thickness signal Dt has the maximum peak value at the focus position, the command section 51 has an optical system of any disc substrate thickness, for example, a substrate thickness of 1. Decide whether to select an optical disc standardized by 2 mm. The optical system switching unit 52 uses a pickup designed for a substrate thickness of 0.6 mm in FIG. 1 when the optical disc is recognized as an optical disc with a substrate thickness of 0.6 mm standardized. When it is recognized as an optical disc standardized by 1.2 mm, a pickup (not shown) designed for a substrate thickness of 1.2 mm is used.

As is well known, the signal processing section 63 appropriately calculates the reproduction signal IS and converts it into a reproduction signal proportional to the received light output level. Further, the auto-tracking signal It is used for tracking control for accurately tracing the laser beam along a predetermined track by the auto-tracking servo, and the auto-focus signal IF moves the objective lens 1 for auto-focus control. used.

Therefore, the disc thickness discriminating section 50 receives the substrate thickness signal Dt and the reproduction signal IS and receives the substrate thickness signal Dt.
Is the peak value of the reproduction signal IS, the substrate thickness of the disc substrate surface 2 is determined by whether it is larger than a predetermined threshold value. Further, the disc thickness discriminating unit 60, when the substrate thickness signal Dt is a zero cross of the autofocus signal IF,
Whether or not the substrate thickness of the disc substrate surface 2 is, for example, 0.6 mm is determined depending on whether or not it is larger than a predetermined threshold value. As a result, the disc thickness discriminating unit 5
0 and 60 are objective lenses 1 for pulling the focus.
In the initial state in which the disk is forcedly vibrated, the level of the substrate thickness signal Dt is detected at the timing of the peak value of the reproduction signal IS, and the thicknesses of the two types of disk substrates 2 are discriminated based on the detected level. When it is determined that the disc is another disc, the other pickup, that is, 1.2 m
A discriminant output is generated to drive a pickup designed for m.

In this embodiment, two pickups, a pickup designed for 0.6 mm and a pickup designed for 1.2 mm, are prepared and switched.
When carrying out the present invention, for 0.6 mm or 1.
It can also be implemented as a configuration in which an objective lens designed for 2 mm is exchanged. Needless to say, the present invention can be applied to a configuration in which a correction lens is selectively inserted in the optical system or a configuration in which the diaphragm is controlled, and it is possible to selectively reproduce the thicknesses of the two types of disk substrates described above. If so, it can be used.

In this embodiment, the pickup designed for 0.6 mm is used for the determination, but the pickup designed for 1.2 mm can also be used for the determination. When reproducing a 0.6 mm standard disc, the ± 1st order light changes from the second outer light receiving element 15B and the third outer light receiving element 16B to the second inner light receiving element 15A and the third inner light receiving element 16A side.

In the present embodiment, the determination can be made at the timing of the peak value of the reproduction signal Is or at the zero-cross timing of the autofocus signal IF exhibiting the S-shaped characteristic.

Further, in this embodiment, the second light receiving element and the third light receiving element for receiving the ± 1st order light are divided into two, and the second inner light receiving element 15A, the second outer light receiving element 15B, and the third inner light receiving element. 16A and the third outer light receiving element 16B, in the case of practicing the present invention, when reproducing a disc of a different standard, the converging point of the ± 1st order light is moved to each light receiving element. If the optical system is designed so that the disc type can be discriminated by the presence / absence of a plurality of light reception outputs.
As a matter of course, if the optical system is designed so that the converging point of the ± 1st order light is separated from each light receiving element, the disc type can be discriminated by the presence or absence of the light reception output.

In addition, the reference for the peak value or the zero cross is an item for which the thickness of the disk substrate 2 is determined by the standard, and is an item determined in relation to the threshold value or the design value. It is not limited to the exact peak value or zero crossing point, but can be roughly determined.

As described above, the disc thickness discriminating apparatus for the optical recording medium of the above embodiment optically discriminates the thickness of the disc substrate 2 and, according to the discriminated thickness of the disc substrate 2,
The reproduction system of the optical recording medium is switched, and this can be the embodiment of claim 1. Therefore, the recording density of the disc substrate 2 can be discriminated without reading or manual operation, and the reproduction of the optical recording medium can be started quickly.

In the disc thickness discriminating apparatus for the optical recording medium of the above-mentioned embodiment, the laser beam focused and irradiated on the optical recording medium is split into the 0th order beam and the ± 1st order beams by the diffraction grating composed of the diffraction grating plate 7. The reflected light of the 0th-order beam is received by the primary element 20 to derive the reproduction signal Is, and the reflected light of the ± 1st-order beams is converted into three beams.
5A, second outer light receiving element 15B, third inner light receiving element 1
In the reproducing apparatus of the optical recording medium which receives the tracking signal It by receiving light by the 6A and the third outer light receiving element 16B,
At the timing when the output level of the reproduction signal Is of the primary element reaches a substantially peak value, the second inner light receiving element 15A and the second outer light receiving element 15B, the third inner light receiving element 16A and the third outer light receiving element 16B The thickness of the substrate of the optical storage medium is identified based on the output level, which can be the embodiment of claim 2.

Therefore, the recording density of the disk substrate 2 can be discriminated without reading or manual operation, and the reproduction of the optical recording medium can be started quickly. The thickness of the substrate of the optical storage medium is adjusted based on the output levels of the second inner light receiving element and the third inner light receiving element at the timing when the output level of the reproduction signal Is of the primary element reaches a substantially peak value. For the purpose of identification, a circuit for identifying the thickness of the substrate of the optical storage medium can be easily constructed by adding an adding circuit or the like.

In particular, in the present embodiment, the second inner light receiving element 15A, the second outer light receiving element 15B, and the third inner light receiving element are arranged at the timing when the output level of the reproduction signal Is of the primary element reaches a substantially peak value. The thickness of the substrate of the optical storage medium is identified based on the output levels of the element 16A and the third outer light receiving element 16B.
By omitting the third outer light receiving element 16B, the conventional photodetector 10 shown in FIG. 2A for receiving the reflected light of the 0th order beam and the reflected light of the ± 1st order beams can be used. It can be done at low cost.

In the disc thickness discriminating apparatus for the optical recording medium of the above-mentioned embodiment, the laser light focused and irradiated on the optical recording medium is split into the 0th order beam and the ± 1st order beams by the diffraction grating composed of the diffraction grating plate 7. The primary element 20 receives the reflected light of the 0th-order beam to derive a reproduction signal Is, and the output level of the autofocus signal IF of the primary element is substantially zero cross at the timing of the zero crossing. The thickness of the substrate of the optical storage medium is identified based on the output levels of the second inner light receiving element 15A and the second outer light receiving element 15B, the third inner light receiving element 16A, and the third outer light receiving element 16B. The embodiment of claim 3 can be made.

Therefore, it is possible to determine without reading the recording density of the disk substrate 2 or without the need for manual operation, and the reproduction of the optical recording medium can be started quickly. Further, the thickness of the substrate of the optical storage medium is identified based on the output levels of the second inner light receiving element and the third inner light receiving element at the timing when the output level of the autofocus signal IF of the primary element is substantially zero crossing. Therefore, a circuit for identifying the thickness of the substrate of the optical storage medium can be easily configured by adding an adding circuit or the like.

In particular, in the present embodiment, the second inner light receiving element 15A, the second outer light receiving element 15B, and the third inner light receiving element are arranged at the timing when the output level of the reproduction signal Is of the primary element reaches a substantially peak value. The thickness of the substrate of the optical storage medium is identified based on the output levels of the element 16A and the third outer light receiving element 16B.
By omitting the third outer light receiving element 16B, the conventional photodetector 10 shown in FIG. 2A for receiving the reflected light of the 0th order beam and the reflected light of the ± 1st order beams can be used. It can be done at low cost.

In the disc thickness discriminating apparatus for the optical recording medium according to the above-mentioned embodiment, the secondary element and the tertiary element are divided into a plurality of portions in the direction substantially orthogonal to the track direction, and the plurality of divided second inner sides. The thickness of the substrate of the optical storage medium is identified based on the output level difference between the light receiving element 15A, the second outer light receiving element 15B, the third inner light receiving element 16A, and the third outer light receiving element 16B. It is possible to detect three or more types of substrate thickness without being limited to these two types of substrate thickness. This can be an embodiment corresponding to claim 4.

In the disc thickness discriminating apparatus for the optical recording medium of the above-mentioned embodiment, the output levels of the secondary element and the tertiary element are compared with the threshold value serving as the reference level, and the thickness of the substrate of the optical storage medium is compared. Is used to identify the
Can be an example corresponding to. Therefore, it is possible to eliminate the influence of a plurality of substrate thicknesses, the temporal change (deterioration, etc.) of the disc substrate, and the influence of scratches.

In the disc thickness discriminating apparatus for the optical recording medium of the above embodiment, the timing at which the output level of the reproduction signal of the primary element reaches a substantially peak value is the focus control formed based on the output of the first light receiving element. The focus detection timing obtained by the above is used, and this can be used as an embodiment corresponding to claim 6. Therefore, the thickness of the substrate of the optical storage medium is identified by the focus control included in a normal reproducing device, and does not complicate the special circuit configuration.

In the disc thickness discriminating apparatus for the optical recording medium of the above-mentioned embodiment, the optical recording medium is an optical disc having a disc substrate 2 having a thickness of 0.6 mm and 1.2 mm. It can be a corresponding example. Therefore, it is possible to automatically identify the thickness of a thickness that is difficult to recognize artificially.

[0085]

As described above, the disc thickness discriminating apparatus for an optical recording medium according to the first aspect of the invention splits the laser beam focused and irradiated onto the optical recording medium into a 0th order beam and a ± 1st order beam by a diffraction grating. 3 beams and the reflected light of the 0th order beam is
The secondary element receives the light to derive a reproduction signal, and the reflected light of the ± first-order beams is received by the secondary element and the tertiary element to derive the tracking signal. Moreover, in the focus pull-in operation, the thickness of the substrate of the optical storage medium is identified based on the output levels of the secondary element and the tertiary element at the timing when the output level of the primary element reaches a substantially peak value. It is a thing.

Therefore, the disc density can be discriminated without reading the recording density of the disc substrate or the manual operation, and the reproduction of the optical recording medium can be started quickly. Further, during the focus pull-in operation, the first
The thickness of the substrate of the optical storage medium is identified based on the output levels of the second inner light receiving element and the third inner light receiving element at the timing when the output level of the reproduction signal of the next element reaches a substantially peak value. A circuit for identifying the thickness of the substrate of the optical storage medium can be easily configured by adding a circuit, a subtraction circuit, etc., and can be implemented at low cost.

According to a second aspect of the present invention, there is provided a disc thickness discriminating apparatus for an optical recording medium, wherein the laser beam focused and irradiated on the optical recording medium is split into a 0th order beam and a ± 1st order beam by a diffraction grating to obtain 3 beams, The reflected light of the next beam is received by the primary element to derive the reproduction signal, and the reflected light of the ± 1st order beam is received by the secondary element and the tertiary element to derive the tracking signal. Moreover, in the focus pull-in operation, the thickness of the substrate of the optical storage medium is identified based on the output levels of the secondary element and the tertiary element at the timing when the output level of the autofocus signal becomes substantially zero cross. .

Therefore, it is possible to judge without reading the recording density of the disk substrate or without the need for manual operation, and it is possible to quickly start the reproduction of the optical recording medium. Further, during the focus pull-in operation, the first
An adder circuit for identifying the thickness of the substrate of the optical storage medium based on the output levels of the second light receiving element and the third light receiving element at the timing when the output level of the autofocus signal of the next element becomes substantially zero crossing. By adding a subtracting circuit or the like, a circuit for identifying the thickness of the substrate of the optical storage medium can be easily configured and can be implemented at low cost.

According to a third aspect of the present invention, in addition to the effect of the first or second aspect, the disc thickness discriminating device for an optical recording medium has a plurality of the secondary elements and the tertiary elements in a direction substantially orthogonal to the track direction. Since it is divided, the position of the spot focused on the optical recording medium is determined based on the output level difference of the plurality of divided light receiving elements, and the thickness of the substrate of the optical storage medium is identified. It is possible to detect three or more types of substrate thickness.

In addition to the effect of claim 1 or claim 2, the disc thickness discriminating apparatus for an optical recording medium of claim 4 compares the output level of the secondary element and the tertiary element with a reference level. The reference level is set as a signal level at a boundary point corresponding to a spot position focused on the optical recording medium, and the output levels of the secondary element and the tertiary element are compared with the reference level to obtain the optical storage medium. Since the thickness of the substrate is identified, it is possible to eliminate the influence of the thicknesses of the plurality of substrates, the temporal change (deterioration, etc.) of the disc substrate, and the influence of scratches and the like.

According to the disk thickness discriminating apparatus for an optical recording medium of the fifth aspect, in addition to the effect of any one of the first to fourth aspects, the output level of the primary element has a substantially peak value. This timing is the timing of focus detection in focus control and is based on the focus position. Therefore, the thickness of the substrate of the optical storage medium can be identified by the focus control included in an ordinary reproducing device. Yes, it does not complicate the special circuit configuration.

According to a sixth aspect of the present invention, there is provided a disk thickness discriminating apparatus for an optical recording medium, wherein the optical recording medium has a substrate thickness of 0.6 mm, in addition to the effect according to any one of the first to fifth aspects. Since the optical disc is a 1.2 mm optical disc, it is possible to automatically discriminate the thickness of a substrate having a thickness that is difficult to recognize artificially.

[0093]

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an optical system pickup portion in a disc thickness discriminating apparatus for an optical recording medium according to an embodiment of the present invention.

2A is an explanatory view showing a photodetector in a state of reproducing a disc having a designed disc thickness in a reproducing apparatus of an optical recording medium, and FIG. 2B is a design of the reproducing apparatus of an optical recording medium. FIG. 6 is an explanatory diagram showing a photodetector in a state of reproducing a disc that does not match the disc thickness, and FIG. 7C is an explanatory diagram showing the photodetector in the disc thickness discriminating apparatus for the optical recording medium of the present embodiment.

FIG. 3 is an explanatory diagram schematically showing how laser light is incident on a disk substrate via an objective lens and is condensed at one point on a recording surface formed on the disk substrate.

FIG. 4 is an explanatory view schematically showing a state in which a laser beam is incident on a disk substrate through an objective lens and cannot be condensed at one point on a recording surface formed on the disk substrate.

FIG. 5 is an explanatory diagram showing that even if the position of the objective lens is changed even slightly, the reflected beam path of the ± first-order light is changed to change the focal point in the photodetector.

FIG. 6 is a circuit diagram showing a disc thickness signal generating circuit in a disc thickness discriminating apparatus for an optical recording medium for carrying out the present invention.

FIG. 7 is a characteristic diagram of a disc thickness signal generating circuit in the disc thickness discriminating apparatus for the optical recording medium of the embodiment of FIG.

8 is a circuit diagram of a disc thickness discriminating apparatus for an optical recording medium using the disc thickness signal generating circuit shown in FIG.

9 is a circuit diagram of a disc thickness discriminating apparatus for another optical recording medium using the disc thickness signal generating circuit shown in FIG.

[Explanation of symbols]

1 Objective lens 2 disk substrate 4 Collimating lens 5 λ / 4 plate 6 Polarizing beam splitter 7 Diffraction grating plate 8 Semiconductor laser 9 Detection lens 10 Photodetector 20 (11, 12, 13, 14) First light receiving element 15A Second inner light receiving element 15B Second outer light receiving element 16A Third inner light receiving element 16B Third outer light receiving element

Continuation of front page (56) Reference JP-A-5-54406 (JP, A) JP-A-6-282866 (JP, A) JP-A-8-227552 (JP, A) JP-A-8-203115 (JP , A) JP-A-8-87760 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B ^7/ 00-7/013 G11B 7/09-7/22 G11B 19/00 -19/18

Claims (6)

(57) [Claims] 1. A laser beam for converging and irradiating an optical recording medium,
The diffraction grating splits the 0th-order beam and the ± 1st-order beams into three beams, and the reflected light of the 0th-order beam is received by the 1st-order element to derive a reproduction signal. In a reproducing apparatus for an optical recording medium in which a secondary element and a tertiary element receive light to derive a tracking signal, a timing at which an output level of a reproduced signal of the primary element becomes substantially a peak value during a focus pull-in operation. 3. A disc thickness discriminating apparatus for an optical recording medium, characterized in that the thickness of the substrate of the optical storage medium is discriminated based on the output levels of the secondary element and the tertiary element in. 2. A laser beam focused and irradiated onto an optical recording medium,
The diffraction grating splits the 0th order beam and the ± 1st order beams into three beams, the reflected light of the 0th order beam is received by the 1st order element to derive a reproduction signal, and the reflected light of the ± 1st order beam In a reproducing apparatus for an optical recording medium, in which a secondary element and a tertiary element receive light to derive a tracking signal, the secondary element at the timing when the output level of the autofocus signal is substantially zero cross during the focus pull-in operation. And a disc thickness discriminating device for an optical recording medium, which discriminates the thickness of the substrate of the optical storage medium on the basis of the signal from the tertiary element. 3. A substrate of the optical storage medium, wherein the secondary element and the tertiary element are divided into a plurality of pieces in a direction substantially orthogonal to the track direction, and based on an output level difference of the plurality of divided light receiving elements. 3. The disc thickness discriminating apparatus for an optical recording medium according to claim 1, wherein the thickness of the disc is discriminated. 4. The thickness of the substrate of the optical storage medium is identified by comparing the output levels of the secondary element and the tertiary element with a reference level. A disc thickness discriminating apparatus for an optical recording medium according to. 5. The timing when the output level of the reproduction signal of the primary element reaches a substantially peak value is the timing of focus detection in focus control.
The disc thickness discriminating apparatus for an optical recording medium according to claim 4. Wherein said optical recording medium, an optical recording medium according to any one of claims 1 to 5, wherein the thickness of the disc substrate is an optical disk of 0.6mm and 1.2mm Disc thickness discriminating device.