KR100636124B1 - Optical pickup apparatus and method for reproducing signal detecting using its apparatus - Google Patents

Abstract

While using a light source for emitting short wavelength light suitable for a high density recording medium and an objective lens having a numerical aperture, the light reflected / diffracted on the recording medium is moved to the first to third light regions in a direction corresponding to the track tangential direction of the recording medium. In the case of adopting the recording medium which is divided into light-receiving and having a lower density than the high density recording medium, the phase difference between the first and third detection signals and the second detection signal of the first to third detection signals from the first to third optical areas Disclosed are an optical pickup apparatus and a method of detecting a reproduction signal using the same, which have a structure for detecting a reproduction signal and are capable of accurately detecting a pit signal of a predetermined length or more, so that a high density recording medium and a low density recording medium can be used interchangeably.

Description

Optical pickup apparatus and method for reproducing signal detecting using its apparatus

1 is a view schematically showing an embodiment of an optical configuration of an optical pickup apparatus according to the present invention,

2 is a view schematically showing an embodiment of a light detection unit according to the present invention;

3 is a diagram schematically illustrating a circuit configuration of a reproduction signal detection unit according to an embodiment of the present invention;

4 is a graph showing an eye pattern of a reproduction signal according to a conventional method;

5 and 6 are sum signals p1 + p3 of the first and third detection signals of the first to third detection signals from the first to third optical regions detected by the light detection unit according to the present invention, respectively. And a graph showing an eye-pattern of the second detection signal p2,

FIG. 7 is a graph showing the sum signal p1 + p3 of the first and third detection signals of FIG. 5 and the second detection signal of FIG. 6 as the light spot moves in the track direction.

8 and 9 are graphs showing an eye pattern of a reproduction signal (RFS) detected by a reproduction signal detection unit according to an embodiment of the present invention;

10 is a view schematically showing a circuit configuration of a playback signal detection unit according to another embodiment of the present invention;                 

FIG. 11 is a graph showing an eye pattern of a reproduction signal RFS ′ detected by the reproduction signal detector of FIG. 10;

12 is a schematic view of a circuit configuration of a playback signal detection unit according to another embodiment of the present invention;

FIG. 13 is a graph showing an eye pattern of a reproduction signal (RFS ") detected by the reproduction signal detection unit of FIG. 12;

FIG. 14 is a graph showing a playback signal (RFS ") detected by the playback signal detector of FIG. 12 as the light spot moves in the track direction.

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

1 ... light source 5 ... optical conversion means 7 ... objective lens

10 ... Recorder 20 ... Photodetector 31,39,131,237 ... Adder

33,37 ... 1st and 2nd gain regulator 35 ... Differential

231 ... switch controller 233 ... switch 235 ... holder

The present invention relates to an optical pickup apparatus and a method of detecting a reproduction signal using the same, and more particularly, to an optical pickup apparatus having an optical configuration suitable for a relatively high density recording medium and employing a relatively low density recording medium. And a reproduction signal detection method for reproducing a low density recording medium using the same.                         

The optical pickup device for the high-density recording medium (i.e., HD-DVD: High-Definition Digital Versatile Disk), which is higher density than the DVD and is being developed, has a light source emitting blue light for high-density recording / reproducing and a numerical aperture of 0.6 or more. The objective lens having is going to be adopted. The high-density optical pickup device employs a photodetector having a four-division structure for focusing and tracking error signal detection like a conventional optical pickup device. The reproduction signal is detected by summing all detection signals of the four-segment photodetector.

Such a high-density optical pickup device must be compatible with not only HD-DVD but also DVD having an optimized standard for the numerical aperture 0.6 of the red light and the objective lens having a wavelength of 650 nm.

However, the high-density optical pickup device as described above uses a conventional reproduction signal detection method that adds all the detection signals of the four-segment photodetector as in the general optical pickup device. By use, the pit reproduction signal of a predetermined length or more is greatly distorted, and the distortion signal overlaps with the center level of the detection signal Pmin of the minimum length pit which is a binarization reference value, making it difficult to accurately reproduce the information recorded on the DVD.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has a structure capable of accurately detecting a reproduction signal when reproducing a relatively low density recording medium while using short wavelength light suitable for a relatively high density recording medium. In particular, it is an object of the present invention to provide an optical pickup apparatus which is capable of adopting a DVD) and a recording medium having a higher density, and a reproduction signal detecting method for reproducing a low density recording medium using the same.

An optical pickup apparatus according to the present invention for achieving the above object comprises: a light source for emitting short wavelength light suitable for a relatively high density recording medium; An objective lens for converging the light incident from the light source to form a light spot on the recording medium; Optical path converting means disposed on an optical path between the light source and the objective lens to convert an advancing path of incident light; A light detection unit reflecting / diffracting the recording medium and dividing / receiving light incident through the objective lens and the optical path changing means into first to third light regions in a direction corresponding to the track tangential direction of the recording medium; Wow; When employing a low density recording medium adapted for light having a longer wavelength than the short wavelength light, the phase difference between the detection signal of the first and third optical areas located outside and the detection signal of the second light area located in the center is utilized. And a reproduction signal detection unit configured to detect a reproduction signal, so that the high density recording medium and the low density recording medium can be used interchangeably.

Here, the short wavelength light is blue light, the objective lens has a numerical aperture of about 0.6 or more, the low density recording medium is a DVD series recording medium, and the high density recording medium is denser than the low density recording medium.

The photodetecting unit may further include first to third light receiving regions for splitting / receiving light reflected / diffracted from the recording medium into first to third light regions in a direction corresponding to the track tangential direction of the recording medium. It is preferable that it consists of a photodetector provided.                     

According to an aspect of the present invention, when the detection signals of the first to third optical regions are p1, p2, and p3, respectively, the reproduction signal detection unit may be represented by the equation RFS = (p1 + p2 + p3) + (p1). The reproduction signal RFS is provided by + p3-k1xp2xk2 and k1 and k2 are gains.

According to another feature of the invention, the reproduction signal detection unit is provided to detect the sum signal of the detection signals of the first and third optical regions as the reproduction signal.

According to still another aspect of the present invention, when the detection signals of the first to third optical regions are p1, p2, and p3, respectively, the reproduction signal detector may include a sum signal (p1 + p3) of the p1 and p3 signals. A switch controller for detecting whether a value is below a predetermined level; A switch turned on / off under the control of the switch controller; And an adder for adding a sum signal p1 + p3 of the p1 and p3 signals and a signal input from the switch to output a reproduction signal.

The reproduction signal detector may further include a holder for holding the p2 signal such that a pre-value of the p2 signal is input to the adder when the switch is turned off between the switch and the input terminal of the adder.

In order to achieve the above object, the present invention provides a method for detecting a reproduction signal by reproducing a low density recording medium with an optical pickup apparatus having an optical configuration suitable for recording / reproducing a high density recording medium, which is emitted from a light source and applied to an objective lens. The light reflected and diffracted by the recording medium after being focused on the recording medium by splitting and receiving the light into the first to third light regions in a direction corresponding to the track tangential direction of the recording medium, thereby the first to third detection signals p1. (p2) outputting p3; The phase difference between the first and third detection signals p1 and p3 from the first and third zones located outside and the second detection signal p2 from the second light zone located in the center is used. Detecting a playback signal.

In this case, it is preferable that the light source emits blue light, the objective lens has a numerical aperture of 0.6 or more, the low density recording medium is a DVD-based recording medium, and the high density recording medium is denser than the low density recording medium.

The reproduction signal detecting step may include applying a gain k1 to the second detection signal p2 from the second light region located in the center; Differentiating a sum signal p1 + p3 of the first and third detection signals p1 and p3 from the first and third optical regions located outside the signal k1 × p2 obtained in the above step; ; Applying a gain (k2) to the differential signal; And adding the differential signal and the first to third detection signals p1, p2, and p3 to output a reproduction signal.

The detecting of the reproduction signal may include adding the first and third detection signals p1 and p3 from the first and third light regions located outside to output the reproduction signal. .

In addition, the playback signal detection step,

Comparing the sum signal p1 + p3 of the first and third detection signals p1 and p3 from the first and third optical regions located outside the predetermined level or less, and Detecting a switch control signal for selectively passing a second detection signal p2 from the two light regions; Turning the switch on / off with the control signal detected in the step; And detecting the reproduction signal by adding the sum signal p1 + p3 and the signal input from the switch side.

The detecting of the reproduction signal may further include: holding the second detection signal p2 such that a pre-value of the second detection signal p2 is input to the adder when the switch is turned off. desirable.

Hereinafter, preferred embodiments of the optical pickup apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a view schematically showing an embodiment of an optical configuration of an optical pickup apparatus according to the present invention.

Referring to the drawings, the optical pickup apparatus according to an embodiment of the present invention forms a light spot on the recording medium 10 by condensing the light source 1 for emitting short wavelength light and the light incident from the light source 1 side An objective lens 7, an optical path converting means 5 disposed on an optical path between the light source 1 and the objective lens 7, and converting a traveling path of incident light, and reflected from the recording medium 10. And a light detection unit for splitting / receiving the light into the first to third light regions, and a reproduction signal detection unit for detecting a reproduction signal from the detection signal of the light detection unit. Further, a collimating lens 3 for converting the divergent light emitted from the light source 1 into parallel light between the light source 1 and the optical path changing means 5, the optical path converting means 5 and the photodetector ( A photodetecting lens 9 is further provided between the two.

The light source 1 preferably emits blue light having a wavelength range of approximately 400 nm, and the objective lens 7 has a numerical aperture of 0.6 or more and preferably approximately 0.65.                     

The optical pickup apparatus according to the present invention preferably has an optical configuration suitable for a relatively high density recording medium (hereinafter, HD-DVD) than a relatively low density DVD-based recording medium (hereinafter, DVD). Here, the optical system configuration of the optical pickup device according to the present invention is not limited to FIG. 1, and various optical system configurations known in the art may be adopted.

As shown in FIG. 2, the photodetecting unit includes first to third light receiving regions 21, 23 and 25 divided in a direction corresponding to a track tangential direction of the recording medium 10. The photodetector 20 can be provided. The first to third light receiving regions 21 and 23 and 25 split and receive the light reflected / diffracted from the recording medium 10 into the first to third light regions so that the first to third detection signals p1 may be used. (p2) (p3) is output.

The division ratios of the first to third light receiving regions 21, 23 and 25 are optimized by the mark conditions such as the numerical aperture of the objective lens 7 and the pit recorded on the recording medium 10. The second light receiving region 23 positioned at the center is preferably sized to receive approximately 10-50% of the zeroth order diffracted light reflected / diffracted by the recording medium 10.

Substantially, the photodetector 20 has a structure in which the first to third light receiving regions 21, 23 and 25 are divided into four parts in total so that the focus and track error signals can be detected. Since the structure is well known, its detailed description and illustration are omitted.

On the other hand, the photodetecting unit includes a diffraction element (not shown) for dividing / diffracting the light reflected / diffracted by the recording medium 10 into the first to third light regions, and the first to the second divided by the diffraction element. The first to third photodetectors (not shown) may be configured to receive the three light regions, respectively, and output the first to third detection signals p1 ', p2', and p3 '. In this case, the first to third detection signals p1 ′, p2 ′, and p3 ′ from the first to third light regions are respectively received from the first to third light receiving regions 21, 23, 25. Are substantially the same as the first to third detection signals p1, p2, and p3.

The reproduction signal detector according to the present invention generates a reproduction signal of the recording medium 10 from the first to third detection signals p1, p2, and p3 detected by the light detection unit as described above. When the reproduction signal detection unit adopts a relatively low density DVD, the first and third detection signals p1 and p3 from the first and third light receiving regions 21 and 25 located on the outside and the center located in the center are used. By using the phase difference of the second detection signal p2 from the second light-receiving region 23, it is provided to detect a reproduction signal in which the conventional signal distortion problem is improved. Further, when the HD-DVD having a relatively high density is adopted, the reproduction signal detection unit first to third detection signals p1 (p2) (p3) of the first to third light receiving regions 21 (23) and 25 (25). It is preferable to further have a structure (not shown) for detecting the reproduction signal using the sum signal p1 + p2 + p3.

According to an embodiment of the present invention, the playback signal detection unit is provided to detect the playback signal of the DVD by the equation (1).

Playback signal = (p1 + p2 + p3) + ((p1 + p3)-k1 × p2) × k2

Here, the gain k1 is a gain that is applied so that the center values of the sum signal p1 + p3 of the first and third detection signals p1 and p3 and the second value of the second detection signal p2 are similar to each other. This gain k1 is varied depending on the degree of distortion of the signal generated during the reproduction of the DVD, which is a low density recording medium, with short wavelength blue light. The gain k2 is equal to the differential signal, that is, the gain k1, by the sum signal p1 + p2 + p3 of the first to third detection signals p1, p2, and p3 corresponding to a normal reproduction signal. It is a gain value that determines how much the differential signal between the sum signal p1 + p3 and the second detection signal p2 of the applied first and third detection signals p1 and p3 is applied. This gain k2 varies depending on the degree of distortion of the signal generated in the process of reproducing the DVD with short wavelength light, which is a blue wavelength region, and a value of 0.1 to 0.5 is preferably applied.

3 is a diagram illustrating an embodiment of a configuration of a playback signal detector that satisfies Equation 1 above. Referring to the drawings, the reproduction signal detection unit includes a first adder 31 that adds the first to third detection signals p1, p2, and p3, and a gain k1 to the second detection signal p2. Differential between the first gain regulator 33 to which the signal is applied, the sum signal p1 + p3 of the first and third detection signals p1 and p3, and the signal input from the first gain regulator 33; From the differential 35, the second gain regulator 37 for applying a gain k2 to the differential signal output from the differential 35, and the first adder 31 and the second gain regulator 37. And a second adder 39 for summing up the input signals.

The optical pickup device according to the embodiment of the present invention as described above satisfies the light detection unit and Equation 1 as illustrated in FIG. 2 while having an optical configuration suitable for relatively high density HD-DVD using blue light. Since a playback signal detection section is provided, the detection signal Pmin of the minimum length pit at which the distortion signal is the binarized reference value of the playback signal when the pit is reproduced over a predetermined length of a relatively low-density DVD standardized for red light having a wavelength of 650 nm is provided. Is separated from the center level. Accordingly, the optical pickup apparatus according to the present invention can accurately reproduce a signal of a relatively low density DVD, and thus can adopt a relatively high density recording medium such as HD-DVD and a relatively low density recording medium such as DVD.

Hereinafter, with reference to Figs. 4 to 9, the principle that the DVD can be compatible with the optical pickup apparatus according to the embodiment of the present invention having an optical configuration suitable for HD-DVD.

4 to 6 respectively show reproduction signals Pall according to a conventional reproduction method when the DVD is reproduced with blue light, and first and third light receiving regions 21 and 25 of the photodetector 20 according to the present invention. The sum of the first and third detection signals p1 and p3 from the sum signal p1 + p3 and the second detection signal p2 are graphs. FIG. 7 is a graph showing the sum signal p1 + p3 and the second detection signal p2 as the light spot moves in the track direction. Here, the eye-pattern is a signal represented by tracing a detection signal of minimum length pit (eg, 3T) to maximum length pit (eg, 14T) at the same start position.

The reproduction signal Pall is a reproduction signal according to a conventional method, that is, first to third detections from the first to third light receiving regions 21, 23 and 25 of the photodetector 20 according to the present invention. It is the sum signal p1 + p2 + p3 of the signals p1, p2 and p3.

Referring to Fig. 4 showing the eye-pattern of the reproduction signal Pall, as shown in the lower side of the graph, signals d having a smaller amplitude than the actual pit detection signal are detected by the signal distortion. These small signals d reproduce the DVD standardized to be suitable for red light as blue light, thereby increasing the amount of detection light at the central portion than at the beginning and end of the pit when playing a pit longer than a certain length, for example, 6T or more. It is caused by the phenomenon.

These small signals d, i.e., the distortion signal d, overlap with the center level of the minimum length pit reproduction signal Pmin, which is the binarization reference value v1 for digitizing the reproduction signal, so that the accurate reproduction signal Pall is correct. Make binarization impossible. Therefore, when the reproduction signal Pall according to the conventional reproduction method is binarized with respect to the reference value v1, for example, a pit having a length of 6T or more is detected as a mirror area without a pit, that is, two or more portions. There is a problem that the pit signal cannot be reproduced correctly because it is detected as being made of a pit.

However, the optical pickup apparatus according to an exemplary embodiment of the present invention considers a signal distortion generated when playing a pit of a predetermined length or more of a DVD, so that the light reflected / diffracted by the recording medium 10 is tracked on the recording medium 10. The first to third light regions are divided / received in a direction corresponding to the tangential direction, and the reproduction signal (RFS) is detected by the equation (1) from the first to third detection signals p1, p2, and p3. Therefore, a pit signal of a predetermined length or more can be accurately reproduced.

More specifically, the small signals shown in FIG. 4, that is, the signal distortion (d) when the pit is reproduced over a predetermined length of the DVD by blue light, can be seen in the comparison of FIGS. 5 and 6 and region A of FIG. This is mainly due to the second detection signal p2 detected in the second light receiving region 23 located at the center.

At this time, the sum signal p1 + p3 and the second detection signal p2 of the first and third detection signals p1 and p3 differ greatly from each other in the amount and tendency of the signal distortion. Accordingly, as shown in the eye-pattern graphs of FIGS. 8 and 9 through the calculation process of Equation 1, the distorted signal d ₀ is _equal to the reference value v1 for binarizing the reproduction signal RFS. Since separated, the pit reproduction signal (RFS) of a predetermined length or more can be detected accurately. Therefore, the optical pickup apparatus according to the present invention can detect a reproduction signal (RFS) of good quality during DVD reproduction.

8 shows Equation 1 when a DVD having a track pitch of 0.74 μm is reproduced by the optical pickup apparatus according to the present invention in which the emission light wavelength of the light source 1 is 400 nm and the numerical aperture of the objective lens 7 is 0.65. The eye-pattern of the reproduction signal (RFS) detected through a satisfactory calculation process is shown, where k1 = 1.49 and k2 = 0.2. FIG. 9 illustrates a case where the reproduction signal RFS of FIG. 8 passes through a waveform equalizer. When the reproduction signal detection unit according to the present invention further includes a waveform equalizer, a clearer reproduction signal RFS may be obtained. have.

As can be seen from the above, for example, when a DVD having a track pitch of 0.74 mu m is reproduced with an optical pickup apparatus using the blue light having a wavelength of 400 nm and the objective lens 7 having a numerical aperture of 0.65, the reproduction signal according to the conventional reproduction method ( Pall) represents the jitter value of the unmeasurable state as shown in FIG. 4. On the other hand, the reproduction signal RFS according to the reproduction method according to the present invention exhibits jitter values of 7.5 to 11% according to the k1 and k2 values, as shown in Figs. Therefore, according to the present invention, it is possible to detect a reproduction signal (RFS) of good quality.

On the other hand, the playback signal detector according to the present invention adds only the first and third detection signals p1 and p3 with relatively small signal distortion in the adder 131, as shown in FIG. RFS ') may be arranged to detect. The reproduced signal (RFS ') detected by the reproduction signal detector according to this embodiment of the present invention is that children - as can be seen in Figure 11 showing the pattern, the distorted signal (d _0') component is for binarizing It is separated from the reference value v1. Therefore, a pit signal of a predetermined length or more can be accurately reproduced. Of course, the reproduction signal detection unit according to the present embodiment has a slightly lower quality than the reproduction signal RFS obtained by the reproduction signal detection unit according to an embodiment of the present invention, although the quality of the reproduction signal RFS 'obtained therefrom is rather simple. The circuit configuration has the advantage of detecting the reproduction signal RFS '.

On the other hand, according to another embodiment of the present invention, the reproduction signal detection unit adds the first to third detection signals p1, p2, and p3 to detect the reproduction signal RFS " p2) may not be summed over a certain period of severe distortion, or may be provided to maintain a transpose value of the second detection signal p2 in a period of severe distortion of the second detection signal p2.

For example, as illustrated in FIG. 12, the reproduction signal detection unit according to the present embodiment may determine whether the sum signal p1 + p3 of the first and third detection signals p1 and p3 is equal to or less than a predetermined level. The switch controller 231 for detecting a signal, the second detection signal p2 is input, the switch 233 turned on / off under the control of the switch controller 231, and the first and third detection signals p1. an adder 237 for adding a sum signal p1 + p3 of the p3 and a signal input from the switch 233 to output the reproduction signal RFS ", and the switch 233 and the adder 237. And a holder 235 holding the second detection signal p2 so that the pre-value of the second detection signal p2 can be input to the adder 237 when the switch 233 is turned off between the input terminals. The holder 235 may include a capacitor having a predetermined capacity capable of repeatedly charging and discharging.

In the region where the second detection signal p2 is greatly distorted as shown in FIG. 7A, the sum signal p1 + p3 of the first and third detection signals p1 and p3 represents a predetermined level or less. Therefore, as in the present embodiment, the switch 233 is controlled according to the sum signal p1 + p3 to thereby add the transpose value of the second detection signal p2 and the second detection signal p2 with the adder 237. When selectively inputted, as shown in Fig. 13, the distortion signal (d ₀ &_quot;) is separated from the binarization reference value v1 of the reproduction signal RFS &quot;. Therefore, according to the reproduction signal detection unit according to the present embodiment, In this case, the reproduction signal RFS " of good quality can be detected. At this time, the second detection signal p2 input to the adder 237 and the signal p2 'corresponding to the transposition signal are shown in FIG. As described above, the distortion signal component is remarkably reduced in the pit area B of the predetermined length or more corresponding to the area A in FIG.

On the other hand, in the case of the structure without the holder 235 in Figure 12, the switch 233 is turned off for a certain period of severe distortion of the second detection signal (p2), so that the second detection signal (p2) in the adder Since it is not summed with the first and third detection signals p1 and p3, the distortion signal component is likewise separated from the mood value for binarization. Therefore, even in this case, the distortion signal component is remarkably reduced in the pit area of a predetermined length or more, so that the accurate reproduction signal RFS " can be detected.

In the above description, although the optical pickup device according to the present invention has an optical configuration suitable for a high-density recording medium such as HD-DVD, it is provided to be compatible with relatively low-density DVD, but the present invention is not limited thereto. Of course, DVD and CD-based recording media can be applied to the compatible adoption. That is, the optical pickup device according to the present invention employs a light source for emitting red light having a wavelength of about 650 nm and an optical configuration suitable for a DVD, and divides the zero-order light reflected / diffracted from the recording medium into first to third light regions. You can optimize the ratio. In addition, when the reproduction signal detection unit is provided to detect the CD-based recording medium reproduction signal by Equation 1, the optimized gains k1 and k2 may be set.

According to the present invention as described above, while using a light source and an objective lens having a numerical aperture that emits short wavelength light suitable for a relatively high density recording medium, the light reflected / diffracted on the recording medium is in the track tangential direction of the recording medium. The first and third detection signals and the first and third detection signals from the first to the third optical region are divided into first and third optical regions in the corresponding direction, and when the recording medium having a relatively low density is employed. Since the reproduction signal is detected using the phase difference of the two detection signals, a pit signal of a predetermined length or more can be detected accurately, and a high density recording medium and a low density recording medium can be used interchangeably.

Claims (17)

A light source for emitting short wavelength light suitable for a relatively high density recording medium; An objective lens for converging the light incident from the light source to form a light spot on the recording medium; Optical path converting means disposed on an optical path between the light source and the objective lens to convert an advancing path of incident light; A light detection unit reflecting / diffracting the recording medium and dividing / receiving light incident through the objective lens and the optical path changing means into first to third light regions in a direction corresponding to the track tangential direction of the recording medium; Wow; When employing a low density recording medium adapted for light having a longer wavelength than the short wavelength light, the phase difference between the detection signal of the first and third optical areas located outside and the detection signal of the second light area located in the center is utilized. And a reproduction signal detection unit configured to detect a reproduction signal, wherein the high density recording medium and the low density recording medium can be used interchangeably. The method of claim 1, wherein the short wavelength light is blue light, the objective lens has a numerical aperture of about 0.6 or more, And the low density recording medium is a DVD-based recording medium, and the high density recording medium is denser than the low density recording medium. The apparatus of claim 1, wherein the photodetecting unit comprises: first to third splitting / receiving light reflected / diffracted from the recording medium into first to third light regions in a direction corresponding to a track tangential direction of the recording medium; An optical pickup apparatus comprising a photodetector having a third light receiving region. The optical pickup apparatus of claim 1, wherein the second optical region is sized to receive approximately 10-50% of the zeroth order diffracted light reflected / diffracted on the recording medium. The method according to any one of claims 1 to 4, wherein the detection signals of the first to third optical regions are p1, p2, and p3, respectively. The reproduction signal detector is provided to detect the reproduction signal (RFS) by the following equation. Equation RFS = (p1 + p2 + p3) + (p1 + p3-k1 × p2) × k2, where k1 and k2 are gain The optical pickup apparatus of claim 5, wherein the gains k1 and k2 are variable. The optical pickup apparatus according to any one of claims 1 to 4, wherein the reproduction signal detector is provided to detect a sum signal of detection signals of the first and third optical regions as a reproduction signal. The method according to any one of claims 1 to 4, wherein the detection signals of the first to third optical regions are p1, p2, and p3, respectively. The reproduction signal detector, A switch controller for detecting whether a sum signal p1 + p3 of the p1 and p3 signals is equal to or less than a predetermined level; A switch turned on / off under the control of the switch controller; And And an adder for adding a sum signal (p1 + p3) of the p1 and p3 signals and a signal input from the switch to output a reproduction signal. The method of claim 8, wherein the playback signal detector, And a holder holding the p2 signal such that a pre-value of a p2 signal is input to the adder when the switch is turned off between the switch and an input terminal of the adder. A method of detecting a reproduction signal by reproducing a low density recording medium with an optical pickup apparatus having an optical configuration suitable for recording / reproducing a high density recording medium, After the light is emitted from the light source and focused on the recording medium by the objective lens, the light reflected / diffracted by the recording medium is split into and received in the first to third light regions in a direction corresponding to the track tangential direction of the recording medium. Outputting a third detection signal p1, p2, p3; The phase difference between the first and third detection signals p1 and p3 from the first and third optical regions located outside and the second detection signal p2 from the second optical region located in the center is used. Detecting a playback signal; and a playback signal detection method. The method of claim 10, wherein the light source emits blue light, the objective lens has a numerical aperture of 0.6 or more, The low density recording medium is a DVD-based recording medium, and the high density recording medium is higher density than the low density recording medium. The method of claim 10 or 11, wherein the reproducing signal detection step comprises: Applying a gain (k1) to the second detection signal (p2) from the second optical region located at the center; Differentiating a sum signal p1 + p3 of the first and third detection signals p1 and p3 from the first and third optical regions located outside the signal k1 × p2 obtained in the above step; ; Applying a gain (k2) to the differential signal; And adding the differential signal and the first to third detection signals (p1) (p2) (p3) to output a reproduction signal. The reproduction signal of claim 12, wherein the gain k1 is varied so that the center value of the second detection signal p2 is similar to the center value of the first and third detection signals p1 and p3. Detection method. 13. The method of claim 12, wherein the gain k2 varies in a range of approximately 0.1 to 0.5. The method of claim 10 or 11, wherein the reproducing signal detection step comprises: And summing the first and third detection signals (p1) (p3) from the first and third optical regions located outside to output a reproduction signal. The method of claim 10 or 11, wherein the reproducing signal detection step comprises: Comparing the sum signal p1 + p3 of the first and third detection signals p1 and p3 from the first and third optical regions located outside the predetermined level or less, and Detecting a switch control signal for selectively passing a second detection signal p2 from the two light regions; Turning the switch on / off with the control signal detected in the step; And adding the sum signal (p1 + p3) and the signal input from the switch to detect a reproduction signal. The method of claim 16, wherein the detecting of the reproduced signal comprises: And holding the second detection signal (p2) such that a pre-value of the second detection signal (p2) is input to the adder when the switch is turned off.

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