KR100607946B1 - Compatible optical recording and/or reproducing apparatus - Google Patents

Abstract

A light source for emitting light, an optical path converting means for converting a propagation path of incident light, an objective lens for focusing incident light to form a light spot on the recording medium, and incident through the objective lens and optical path converting means reflected from the recording medium An optical pickup including a photodetector for receiving the light, the optical pickup being adapted to record and reproduce a high density recording medium; And a signal converter configured to convert the analog detection signal input from the photodetector to a reference level and convert the analog detection signal into a digital signal, and calculate and output an information reproduction signal of the recording medium from the detection signal of the photodetector. In addition, it is possible to prevent the reproduction signal error caused by the amount of detection light in the center portion of the mark having a predetermined length or more in the reproduction of a low density recording medium whose reference level is relatively low than that of the high density recording medium. Disclosed is an optical recording / reproducing apparatus, which is set so that the high density recording medium and the low density recording medium having different formats can be used interchangeably.

Such an optical recording / reproducing apparatus adopts an optical pickup suitable for recording and reproducing a high-density recording medium such as HD-DVD, while recording a lower density such as a DVD that records relatively lower density information than a high-density recording medium without the addition of an additional optical component. Can adopt media compatible.

Description

Compatible optical recording and / or reproducing apparatus

1 is a graph showing a general eye-pattern signal for explaining Asymmetry of an eye-pattern signal;

2 is a view schematically showing the configuration of an optical recording and reproducing apparatus according to an embodiment of the present invention;

3 is a block diagram schematically showing the configuration of an embodiment of a circuit unit according to the present invention;

4 is a graph showing a pit reproduction signal when pits having a length of 3T are formed at equal intervals;

FIG. 5 is a graph illustrating a process of correcting a pit length error in a digitized reproduction signal slid with respect to the reference level R of FIG. 4;

FIG. 6 is a graph showing a detection signal of a photodetector compared with a detection signal of reproducing a low density recording medium with an optical pickup for low density recording medium when the low density recording medium is reproduced with the optical pickup for high density recording medium according to the present invention;

FIG. 7 is a graph showing an eye-pattern signal showing a slicing of a detection signal for reproducing a low density recording medium with respect to an intermediate level of a minimum pit signal using the optical pickup for the high density recording medium of FIG. 6;

FIG. 8 is an eye pickup of the optical signal for the high density recording medium of FIG. 6, which is shown by slicing a detection signal reproduced from a low density recording medium with respect to a reference level spaced toward the signal level in the interval between the pit and the pit rather than the middle level of the minimum pit signal; Graph showing pattern signal.

<Description of the symbols for the main parts of the drawings>

1.Recording medium 10 ... Optical pickup 11 ... Light source

20 Optical path changing means 30 Objective lens 40 Photodetector

50 Circuit unit 60 Signal converter 61 Comparator

70 ... Imitation 71 ... Delay 75 ... Logic Gate

80 ... Feedback

The present invention relates to an optical recording / reproducing apparatus, and more particularly, to a relatively low density recording medium such as a DVD (Digital Versatile Disk) having a different format, and an HD-DVD provided to enable higher density information recording than the low density recording medium. The present invention relates to a compatible optical recording / reproducing apparatus capable of interchangeably employing a relatively high density recording medium such as a high-definition digital versatile disk.

In general, an optical pickup is an apparatus which is employed in an optical recording / reproducing apparatus to record information of a recording medium such as an optical disk or to reproduce recorded information in a non-contact manner. In this optical pickup, a light source having a shorter wavelength and / or an objective lens having a higher number of apertures is used to reduce the size of optical spots formed on the recording medium, and a tilt tolerance of the recording medium by employing a high-number objective lens is employed. In order to increase the recording and reproduction density of information by developing a recording medium having a thinner thickness, the technology has been developed.

In other words, a player equipped with an optical lens adopting an objective lens with a numerical aperture of 0.45 and a light source with a wavelength of 780 nm to record and reproduce a CD having a protective layer thickness of 1.2 mm and the like has been widely used. A player for a series (hereinafter, referred to as DVD) is commercially available.

Optical pickup for recording and reproducing DVD is almost standardized by adopting an objective lens having a numerical aperture of 0.6 and a light source having a wavelength of 650 nm, and considering the mechanical disc tilt tolerance as the numerical aperture of the objective lens increases, Alternatively the protective layer has a thickness of 0.6 mm.

Furthermore, a high density recording medium capable of recording information at a higher density than the DVD and an optical pickup for recording and reproducing the same have been developed. Here, the high density recording medium is defined as a recording medium such as HD-DVD (High Definition-Digital Versatile Disk) capable of recording high density information of several to several tens of GB or more.

On the other hand, the information recording / reproducing density of the recording medium is determined by the size of the light spot which is formed on the recording medium by optical pickup. In general, the size S of the light spot, i.e., the diameter, becomes smaller as light having a shorter wavelength? Is used, as shown in Equation 1, and smaller as the numerical aperture NA of the objective lens becomes larger.

S ∝ λ / NA

Therefore, in optical pickups for high density recording media requiring higher recording and reproduction density, short wavelength light sources such as, for example, blue semiconductor lasers that emit light of a shorter wavelength range than in the case of DVD optical pickups in order to reduce the size of the optical spots and 0.6, It is necessary to employ the objective lens having the above high numerical aperture.

In addition, the optical pickup for recording and reproducing the high density recording medium should be capable of employing a DVD as well as the high density recording medium as described above.

When the emission wavelength of the light source is 400 nm and the numerical aperture of the objective lens is 0.6, the condensed light spot has a diameter of approximately 0.67 μm. On the other hand, in the case of an optical pickup for DVD employing a light source having a wavelength of 650 nm and an objective lens having a numerical aperture of 0.6, the condensed light spot has a diameter of approximately 1.08 μm.

Substantially, the width of the pit is optimized for the 1.08 μm optical spot diameter as described above, and the Asymmetry of the eye-pattern signal is reproduced in the standard book when reproduced by the optical pickup for DVD. It is designed to come in within% to 15%.

Here, the asymmetry of the eye-pattern signal is represented by the eye-pattern signal tracing the reproduction signals of the maximum length pit 14T and the minimum length pit 3T at the same starting position as shown in FIG. If the lowest and highest points from the zero level of the playback signal are I _14L , I _14H , and 3T feet, the lowest and highest points from the zero level of the playback signal are I _3L and I _3H , respectively. Is defined.

However, when DVDs are played back using optical pickups for high-density recording media employing an objective lens with a numerical aperture of 0.6 and a light source with a wavelength of 400 nm, the asymmetry of the reproduction signal is out of specification due to the difference in the optimum diameter of the optical spots, which makes normal playback impossible. Become.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and employs an optical pickup suitable for recording and reproducing high density recording media such as HD-DVD, but has relatively lower density information than the high density recording media without the addition of additional optical components. It is an object of the present invention to provide an optical recording and reproducing apparatus that can adopt a low-density recording medium such as a DVD for recording.

An optical recording and reproducing apparatus according to the present invention for achieving the above object comprises: a light source for emitting light, an optical path converting means for converting a traveling path of incident light, an objective lens for focusing the incident light to form an optical spot on the recording medium; And an optical pickup that is reflected from the recording medium and receives a light incident through the objective lens and the optical path changing means, the optical pickup being adapted to record and reproduce a high density recording medium; A circuit unit configured to compare the analog detection signal input from the photodetector to a reference level and convert the analog detection signal into a digital signal, and calculate and output an information reproduction signal of a recording medium from the detection signal of the photodetector; And a reproducing caused by an increase in the amount of detection light in the center portion at the beginning and the end of a mark having a predetermined length or more during reproduction of a low density recording medium in which the reference level is configured to record information of lower density relative to the high density recording medium. It is set so as to prevent signal errors, and it is possible to use a high density recording medium and a low density recording medium having different formats.

Here, the reference level is preferably a level spaced apart from the intermediate level of the minimum mark reproduction signal amplitude of the recording medium by a predetermined magnitude in the level direction of the signal reproduced in the section between the mark and the mark of the recording medium.

In this case, the reference level is a level spaced apart from the intermediate level toward the reproduction signal level of the mark-to-mark interval by approximately half of the approximately rhombic width shown in the eye-pattern signal formed using the detection signal of the photodetector. It is preferable.

On the other hand, the circuit unit further comprises an addition and subtraction unit for adding and subtracting and outputting the digital signal input from the signal conversion unit, the reproduction signal error generated by slicing the detection signal to the reference level during recording medium reproduction It is preferable that it is provided to correct.

The circuit unit may further include: a feedback unit converting a digital signal output from the signal converter or the controller into approximately a direct current signal between the output terminal of the signal converter or the controller and the reference level signal input terminal of the signal converter; More preferably, it is arranged to automatically adjust the level of the reference level signal.

The high density recording medium is an HD-DVD recording medium, and the low density recording medium is a DVD recording medium.

On the other hand, the optical recording and reproducing apparatus according to the present invention for achieving the above object is to focus a light source for emitting light having a wavelength of approximately 500 nm or less, optical path conversion means for converting the traveling path of the light emitted from the light source, and incident light An optical pickup including an objective lens having a numerical aperture of 0.6 or more so as to form an optical spot on the recording medium, and a photodetector for receiving light reflected from the recording medium and incident through the objective lens and the optical path changing means; And a signal converter for converting the analog detection signal input from the photodetector into a digital signal by comparing it with a reference level, wherein the circuit unit calculates and outputs an information reproduction signal of a recording medium from the detection signal of the photodetector. And the reference level is set to deviate from an intermediate level of the minimum mark signal amplitude of the recording medium.

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

2 is a view schematically showing the configuration of an optical recording and reproducing apparatus according to an embodiment of the present invention.

Referring to the drawings, an optical recording / reproducing apparatus according to an embodiment of the present invention includes an optical pickup 10 and an information of the recording medium 1, which are adapted to record and reproduce a relatively high density recording medium such as HD-DVD. And a circuit unit 50 for generating a reproduction signal.

The optical pickup 10 includes a light source 11 for emitting light, an optical path converting means 20 for converting a traveling path of incident light, an objective lens 30 for focusing incident light, and a recording medium 1 And a photodetector 40 for receiving the reflected light. In addition, the collimating lens 15 and the condenser lens 35 are provided on the optical path between the light source 11 and the objective lens 30, and between the optical path changing means 20 and the photodetector 40, respectively.

The light source 11 is preferably a semiconductor laser for emitting blue laser light having a wavelength of 500 nm or less, preferably 400 nm. The light emitted from the light source 11 is converted into parallel light by the collimating lens 15 and then incident to the optical path converting means 20.

The optical path converting means 20 includes, for example, a polarizing beam splitter 21 having a mirror surface 21a for transmitting and reflecting incident light according to its polarization component, and a wavelength plate 25 for converting polarized light of the incident light. do.

The polarization beam splitter 21 is disposed on an optical path between the light source 11 and the objective lens 30 to transmit light of one polarization component among the light incident from the light source 11 and reflects the rest. . The wave plate 25 is disposed on the optical path between the polarization beam splitter 21 and the objective lens 30, and is preferably a quarter-wave plate with respect to the emitted light wavelength of the light source 11. Do. The wave plate 25 converts the polarized light of the incident light so that the light reflected from the recording medium 1 is reflected on the mirror surface 21a of the polarization beam splitter 21 and directed toward the photodetector 40.

In the present embodiment, the objective lens 30 preferably has a high aperture number of about 0.6 or more. The present embodiment shows an example in which the objective lens 30 is provided with a single focusing lens, but any one of two focusing lenses, a solid immersion lens (SIL), and a solid immersion lens (SIM) can be realized to realize a desired high aperture number. One may be employed.

The optical pickup 10 according to the present invention as described above forms an optical spot suitable for recording and reproducing a relatively high density recording medium such as HD-DVD.

For example, when the emission light wavelength of the light source 11 is 400 nm and the numerical aperture of the objective lens 30 is 0.6, the diameter of the light spot condensed on the recording surface of the recording medium 1 is approximately 0.67 μm, Higher-density information is recorded and reproduced compared to an optical pickup for DVD (not shown) which uses a light source 11 having a wavelength of 650 nm and an objective lens 30 having a numerical aperture of 0.6 to form an optical spot having a diameter of 1.08 µm.

The circuit unit 50 includes a signal converter 60 for converting an analog signal input from the photodetector 40 into a digital signal in comparison with a reference level signal.

The reference level signal is the amount of light detected in the center portion at the beginning and at the end at a pit of a predetermined length or more, for example, 4T or more, during reproduction of a low density recording medium such as a DVD, which is configured to record relatively lower density information than the high density recording medium. In order to prevent an increase in the reproduction signal error that occurs, the signal level is set to a level spaced from the signal level of the center portion of the pit toward the reproduction signal level in the mirror area between the pit and the pit.

Preferably, the reference level is outside the intermediate level of the pit 3T reproduction signal amplitude having the minimum length of the low density recording medium, and the signal level reproduced in the interval between the pit and the pit of the recording medium 1 from the intermediate level. Direction is set at a level spaced apart by a predetermined size.

At this time, when the low-density recording medium having the DVD standard is reproduced by the optical pickup 10 according to the present invention, the distance from the intermediate level of the reference level is shown in FIGS. 7 and 8 to be described later. It is preferable to correspond to about half of the width of the approximate rhombus shape which appears in the eye-pattern signal formed by triggering the detection signal of 40).

The setting of the reference level is that when a pit having a predetermined length or more is reproduced on a low density recording medium, the signal is increased in the center portion as if there is no pit, so that two short pit are positioned at the pit position at predetermined intervals. This is to prevent a recognized playback signal error.

As illustrated in FIG. 3, the signal converter 60 includes, for example, a comparator 61. The detection signal of the photodetector 40 is input to one input terminal of the comparator 61, and the reference level signal is input to the other input terminal.

The comparator 61 slices the reproduction signal of the recording medium 1 with respect to the reference level signal, so that the reproduction signal region higher than the reference level is "1" and the reproduction signal region lower than the reference level is "0". Output a digital signal.

At this time, since the reference level is set to deviate from the intermediate level as described above, the pit reproduction signal is longer than the actual pit length, and the mirror region reproduction signal between the pit is detected shorter than the actual length.

Therefore, it is preferable that the circuit unit 50 according to the present invention further includes an addition / decrease unit 70 for adding and subtracting and outputting the digital signal output from the comparator 61.

As shown in FIG. 3, the subtractor 70 includes a retarder 71 such as a D flip-flop for delaying a digital signal input from the comparator 61, the comparator 61 and a retarder ( A logic gate (OR-GATE) 75 may be configured to receive a signal output from the signal 71) and logically combine the digital signal with the delay signal.

In this case, if the reference level has a size spaced about half of the width of the diamond shape with respect to the intermediate level as described above, the pit reproduction signal is detected to be approximately as long as the pit length unit T, and thus the subtraction unit 70 Preferably, the digital signal input from the comparator 61 is added or subtracted in approximately pit length units T based on a signal reproduced shorter than the minimum length pit 3T of the recording medium 1. Of course, if the magnitude of the separation from the intermediate level of the reference level is an integer multiple of half of the rhombic width, the pit reproduction signal is also detected as long as an integer multiple of the pit length unit, so that the digital part is approximately pit length What is necessary is to add or subtract by the integer multiple of a unit.

For example, if the recording medium 1 has pit lengths of 3T arranged at intervals of −3T, the photodetector 40 outputs an analog signal as shown in FIG. 4. In this case, C represents an intermediate level, and R represents a reference level spaced apart from the intermediate level toward the signal level of the mirror region between the pits. Here, -3T represents the mirror area between the pit and the pit, and likewise below, the section between the pit and the pit is represented by "-" so as to be distinguished from the pit area.

When the comparator 61 compares the reference level signal with the analog signal and outputs a digital signal of "1" in an area higher than the reference level and "0" in an area lower than the reference level, FIG. As in, a signal having a pit length of 4T and an area length of 2T between pit is output. That is, the pit length is detected 1T longer than the actual one.

When the digital signal is delayed by 1T in the delayer 71 as shown in FIG. 5B, the 1T delayed signal and the output signal of the comparator 61 are inputted to the OR gate 75. In Fig. 5 (c), a pit signal having a length of 3T is output.

Accordingly, the subtraction unit 70 outputs a reproduction signal in which an error occurring, for example, by an integer multiple of approximately a pit length unit is corrected as follows.

On the other hand, the circuit unit 50 according to the present invention between the output terminal of the subtraction unit 70 and the reference level signal input terminal of the signal conversion unit 60 so that the level of the reference level signal can be automatically adjusted. It is preferable to further include a feedback unit 80 for converting the digital signal output from the unit 70 into a direct current signal and feeding back.

The feedback unit 80 includes an integrator 81 for integrating the digital signal output from the adder and subtractor 70, and a low pass filter for passing only low frequency components of the signal output from the integrator 81. Filter: 85).

The low pass filter 85 outputs a substantially DC signal. When the DC signal is differentially inputted to the reference level signal and inputted to the signal conversion unit 60, for example, pits having the same length are equal to the pit length. The reference level signal level is automatically adjusted so that the digital sum value of the digital signal output from the subtractor 70 becomes zero if it is arranged as.

The optical pickup 10 of the optical recording and reproducing apparatus according to the embodiment of the present invention as described above forms an optical spot of a size suitable for recording and reproducing a high density recording medium, that is, an HD-DVD.

When a high density or low density recording medium is employed, the signal conversion unit 60 may be configured with respect to a reference level set to a level spaced apart in a direction in which a signal level increases in an intermediate level of a minimum pit 3T reproduction signal of the recording medium 1. The detection signal of the photodetector 40 is sliced, and the reference level signal and the detection signal are compared and converted into a digital signal. At this time, since the digital signal output from the signal converter 60 is generated with respect to the reference level signal out of the intermediate level, the pit reproduction signal is detected to be longer by, for example, an integer multiple of the pit minimum unit.

The digital signal output from the signal converter 60 is added or subtracted by, for example, the shortest pit minimum integer multiple of the shortened pit based on the signal reproduced shorter than the minimum foot. Therefore, the digital signal outputted from the subtractor 70 is a reproduced signal in which the pit length error caused by setting the reference level out of the intermediate level of the reproduced signal of the minimum pit is corrected.

On the other hand, the reproduction signal output from the subtraction unit 70 is fed back to the signal conversion unit 60 via the feedback unit 80 to automatically adjust the reference level.

Here, the circuit unit 50 according to the present invention has been described and illustrated to generate a reproduction signal through the same process when employing a high density and low density recording medium, but is not limited thereto. That is, when the low density recording medium is employed and when the high density recording medium is employed, different reference levels are selectively used, and a switch (not shown) is added between the signal conversion unit 60 and the subtraction unit 70 so that the signal conversion unit 60 can be used. The output signal may be provided to selectively pass through the subtractor 70. In this case, when employing a low density recording medium, a reproduction signal is generated through the above-described process. When employing a high density recording medium, when the reference level signal is set to the intermediate level of the minimum pit signal, the digital signal output from the signal converter 60 is used. Becomes a playback signal.

In the following, a more specific example will be described with the principle that the optical recording / playback apparatus according to the embodiment of the present invention can adopt a relatively low density recording medium such as DVD.

6 is a graph showing a detection signal of the photodetector 40 when the DVD is reproduced by the HD-DVD optical pickup 10 according to the present invention.

When the DVD is reproduced by the optical pickup 10 for HD-DVD according to the present invention, the detection signal (solid line) output from the photodetector 40 is the same as the light source 11 having a wavelength of 650 nm and the numerical aperture 0.6. Compared to the detection signal (dotted line) when the DVD optical pickup employing the objective lens 30 is reproduced, the pit reproduction signal of 6T or more is increased in the central portion than at the beginning and end of the pit. Phenomenon occurs.

This is because the pit width ratio of the DVD standard to the optical spot diameter is about 40% for the optical spot formed by the optical pickup for DVD, whereas the optical spot formed by the optical pickup for HD-DVD 10 according to the present invention is used. That's about 60%, so the center of pit over 4T sees it as a mirror area without pit.

Therefore, slicing the detection signal with respect to the intermediate level (0.187) of the minimum pit (3T) signal, as shown in Table 1, the detection signal of the pit area having the length of 6T, 7T, 8T and 9T is different from the actual one. There is a problem that is outputted with two signals. This is also confirmed when the detection signal is triggered at the intermediate level (0.187) of the minimum pit 3T signal and represented as an eye-pattern signal as shown in FIG. That is, it can be seen that signals having a smaller amplitude than the actual pit signal (shown in the center of the signal magnitude axis) are detected. At this time, jitter is also large at 11.4%. Here, the horizontal axis of FIG. 7 is a time axis expressed in T / 100 units with respect to the pit length unit, and the vertical axis is an axis indicating the magnitude of the reproduction signal in arbitrary units.

However, as in the present invention, when the detection signal is sliced at a level outside the intermediate level, that is, a level larger than the intermediate level by 1/2 of the rhombic width appearing in the eye-pattern signal as the reference level (0.245) As shown in Table 1, there are no pit regions in which two or more signals are detected. This is also confirmed when the detection signal is triggered at the reference level (0.245) and represented as an eye-pattern signal as shown in FIG. In other words, signals with an amplitude smaller than the actual fit signal are not detected. Of course, jitter is also greatly reduced to approximately 10% or less, thereby improving jitter characteristics.

At this time, since the slicing level is out of the intermediate level (0.187), when slicing the detection signal with respect to the reference level (0.245) as described above, as shown in Table 1 and FIG. It is detected uniformly longer by about 1T than the pit signal recorded on the medium, and the interval reproduction signal between the pit is uniformly detected by about 1T uniformly.

Therefore, when the digital signal detected by the signal converter 60 of the present invention is inputted to the subtractor 70 and compensated by, for example, 1T, a reproduction signal identical to the signal recorded on the low density recording medium can be obtained.

On the other hand, when the high density recording medium is reproduced with the optical pickup 10 according to the present invention, as in the case of reproducing the low density recording medium, a phenomenon in which the amount of detected light increases at the center portion than at the beginning and end of the pit reproduction signal of 4T or more is increased. Does not occur. However, it is a matter of course that a reproduction signal can be generated by the same process as that of a low density recording medium.

The optical recording and reproducing apparatus according to the present invention as described above uses an optical pickup (10) using a blue-based short wavelength laser and an objective lens 30 having a high numerical aperture so as to be suitable for recording and reproducing high-density recording media such as HD-DVD. By adopting a proper reference level, a low density recording medium such as a DVD can be used interchangeably without additional optical components.

Here, the optical pickup 10 structure shown in Fig. 2 has a protective layer having a thickness of 0.6 mm, like a digital multi-function disc, such that a high-density recording medium, such as HD-DVD, is formed on the recording surface of the high-density recording medium and the digital multi-function disc. The case where the light spot with the same aberration characteristic can be formed is illustrated.

If the high-density recording medium has a protective layer thickness of less than 0.6 mm, for example, 0.4 mm or 0.1 mm, and the low-density and high-density recording medium have different protective layer thicknesses, the optical pickup 10 according to the present invention is a type of recording medium. At least one of changing the size and the incident angle of the light beam incident to the objective lens 30 on the optical path between the light source 11 and the objective lens 30 so as to correct the difference in the protective layer thickness according to It may further employ a correction means (not shown) consisting of a focusing lens of.

In the present embodiment, on the other hand, by setting the reference level to a level higher than half of the minimum pit signal amplitude by half the width of the rhombus shape of the eye-pattern signal shown in Figs. Although uniformly described and illustrated as being extended by an integer multiple of the minimum pit length unit T, it may of course vary depending on how far the intermediate level is set from the intermediate level.

In the above, although the optical recording and reproducing apparatus according to the present invention has been described and illustrated to be compatible with high density and low density recording media, it can be used exclusively for high density recording media.

The optical recording and reproducing apparatus according to the present invention as described above employs optical pickup suitable for recording and reproducing high density recording media such as HD-DVD, and provides relatively lower density information than the high density recording media without the addition of additional optical components. A low density recording medium such as a DVD to be recorded can be used interchangeably.

Claims (12)

A light source for emitting light, an optical path converting means for converting a propagation path of incident light, an objective lens for focusing incident light to form a light spot on the recording medium, and a reflection of the recording medium through the objective lens and optical path converting means An optical pickup including a photodetector for receiving the incident light, the optical pickup being adapted to record and reproduce a high density recording medium; A circuit unit configured to compare the analog detection signal input from the photodetector to a reference level and convert the analog detection signal into a digital signal, and calculate and output an information reproduction signal of a recording medium from the detection signal of the photodetector; Including; To prevent a reproduction signal error caused by the detection light amount at the center portion of the mark having a predetermined length or more at the time of reproduction of the low density recording medium whose reference level is to record information of lower density relative to the high density recording medium than at the beginning and the end thereof. It is set to be able to use a high density recording medium and a low density recording medium of different formats. And the reference level is a level spaced apart from the intermediate level of the minimum mark reproduction signal amplitude of the recording medium by a predetermined magnitude in the level direction of the signal to be reproduced in the section between the mark and the mark of the recording medium. delete The method of claim 1, wherein the reference level, And a level spaced apart from the intermediate level toward the reproduction signal level of the mark-to-mark interval by half of the width of the rhombus shape shown in the eye-pattern signal formed by using the detection signal of the photodetector. The method of claim 1, wherein the circuit unit, And a subtraction unit for subtracting and outputting a digital signal input from the signal conversion unit to correct a reproduction signal error generated by slicing a detection signal with respect to the reference level when reproducing a recording medium. Optical recorder. The method of claim 4, wherein the regulating unit A delay unit for delaying the digital signal input from the signal conversion unit; And a logic sum gate configured to receive the signals output from the signal converter and the delay, respectively, and to logically combine the digital signal and the delayed signal, which is generated by slicing a detection signal with respect to the reference level when the recording medium is reproduced. An optical recording and reproducing apparatus, characterized in that for outputting a reproduction signal with error correction. The method of claim 4, wherein the regulating unit, And a digital signal input from the signal converting section on the basis of a signal reproduced shorter than the minimum mark length of a recording medium by a predetermined integer multiple of the mark length unit (T). The circuit unit according to claim 1 or 4, wherein the circuit unit comprises: And a feedback unit converting and feeding back a digital signal output from the signal converter or the controller to a DC signal between an output terminal of the signal converter or the controller, and a reference level signal input terminal of the signal converter. An optical recording and reproducing apparatus, characterized in that for adjusting a level of a reference level signal. The method according to any one of claims 1 or 3 to 6, The high density recording medium is an HD-DVD recording medium, and the low density recording medium is a DVD recording medium. The method according to any one of claims 1 or 3 to 6, And the light source emits light having a wavelength of 500 nm or less, and the objective lens has a numerical aperture of 0.6 or more. A light source for emitting light having a wavelength of 500 nm or less, an optical path converting means for converting a traveling path of the light emitted from the light source, an objective lens having a numerical aperture of 0.6 or more so as to focus the incident light to form a light spot on the recording medium, and a recording medium. An optical pickup including a photodetector which is reflected by the optical detector and receives light incident through the objective lens and the optical path changing means; And a signal converter for converting the analog detection signal input from the photodetector into a digital signal by comparing it with a reference level, wherein the circuit unit calculates and outputs an information reproduction signal of a recording medium from the detection signal of the photodetector. Include, And the reference level is set so as to deviate from an intermediate level of the minimum mark signal amplitude of the recording medium. The method of claim 10, wherein the circuit unit, And a subtraction unit for subtracting and outputting a digital signal input from the signal conversion unit to correct an error of a reproduction signal generated by slicing a detection signal with respect to the reference level during reproduction of a recording medium. Optical recording and reproducing apparatus. The method of claim 10 or 11, wherein the circuit unit, And a feedback unit converting and feeding back a digital signal output from the signal conversion unit or the subtraction unit to a DC signal between an output terminal of the signal conversion unit or the subtraction unit and an input terminal of the signal conversion unit. Optical recording and reproducing apparatus, characterized in that for adjusting the level of.

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