KR100243139B1 - An optical pickup device - Google Patents

Abstract

Disclosed is an optical pickup apparatus capable of reducing an offset of a track error signal generated by movement of an objective lens.

The disclosed optical pickup apparatus includes a light source, an objective lens for focusing incident light such that light spots are formed on a recording surface of the disk, and optical path converting means arranged on an optical path between the light source and the objective lens to convert a traveling path of the incident light; And four light receiving regions (E) (F) (G) (H) disposed on one side of the optical path converting means and respectively arranged to receive light through the objective lens and the optical path converting means and photoelectrically convert them. A first photodetector having a light emitting region, and four light receiving regions A formed in an L shape so as to be dividedly disposed to correspond to each of the light receiving regions E, F, G, and H, respectively; B) a second photodetector having (C) (D) and a track error signal detector for detecting a track error signal of the disc from the output signals of the first and second photodetectors, the track error signal detector comprising: Offset is offset by the phase difference method from the signals output from the first and second photodetectors. A first circuit part for outputting an included track error signal, a second circuit part for outputting a signal for correcting a track error signal including an offset from a signal output from the first or second photodetector, and first and second circuit parts And a first differential unit which differentially outputs a track error signal outputting a differential offset signal.

Description

Optical pickup device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus, and more particularly, to an optical pickup apparatus capable of reducing an offset of a track error signal generated by movement of an objective lens due to eccentricity of a disc.

In general, an optical pickup device is employed in a compact disc player, a digital video disc player, a CD-ROM drive, a DVD-ROM drive, or the like to perform recording / reproduction of information in a non-contact manner.

1 is a view schematically showing an optical arrangement of a conventional optical pickup device.

Referring to the drawings, a conventional optical pickup apparatus includes a light source 1 for generating and outputting light, an objective lens 12 for converging incident light so that an optical spot is formed on the recording surface of the disk 19, and incident divergent light. A collimating lens 18 for converting into parallel light, a beam splitter 13 for transmitting and / or reflecting incident light, and a photodetector 16 for detecting an error signal and an information signal.

The objective lens 12 is disposed between the light source 1 and the disk 19 to focus light incident from the light source 1 to form a light spot on the recording surface of the disk 19. At this time, the objective lens 12 is driven by an actuator (not shown) so that the optical spot formed by the objective lens 12 at the time of recording / reproducing the information signal can follow the correct track position of the disk 19. .

The beam splitter 13 reflects the light incident from the light source 1 toward the disk 19, and transmits the light incident from the objective lens 12 toward the photodetector 16. .

The collimating lens 13 is disposed between the objective lens 12 and the beam splitter 13 to convert the divergent light incident from the light source 1 into parallel light so as to be incident on the objective lens 12.

As shown in FIG. 2, the photodetector 16 includes four light receiving regions A, B, C, and D that independently photoelectrically convert and detect an information signal and an error signal.

In such an optical pickup device, the light spots formed on the disk 19 by the objective lens 12 are reflected by the disk 19. At this time, the reflected light is different from the 0th order diffracted light by the track of the disk 19 according to the position from the center of each track of the disk 19. ± 1 The differential diffracted light is interfered and detected by the photodetector 16 via the objective lens 12 and the beam splitter 13.

Therefore, as shown in the drawing, the detection signals of the light receiving area A and the light receiving area C are summed, the detection signals of the light receiving area B and the light receiving area D are summed, and if the two sum signals are differential, the track error is determined by the phase difference detection method. The signal can be detected.

On the other hand, such a disk 19 has an eccentricity of a predetermined size at the time of manufacture. Therefore, the objective lens 12 is provided to be moved within a predetermined range so that the above optical pickup apparatus can follow the correct track position when recording and reproducing the information signal.

Therefore, an offset is generated in the track error signal by the phase difference detection method of the photodetector 16 as described above, which makes it difficult to follow the correct track position of the disk 19.

In addition, in order to solve the problem of offset of the track error signal by the phase difference detection method as described above, the incident light between the light source 1 and the beam splitter 13 is converted into zero order diffracted light, ± 1 A grating (not shown) is further provided for branching into differential diffracted light or the like. When the track error signal is detected by the three-beam method, the use efficiency of light for recording / reproducing the information signal is reduced. Therefore, the optical pickup device having such a structure is difficult to be employed in DVD_RAM or the like which requires a large light intensity.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical pickup apparatus capable of detecting a track error signal having a high offset while reducing light use efficiency.

1 is a view schematically showing an optical arrangement of a conventional optical pickup device;

2 is a plan view schematically showing the photodetector of FIG.

3 is a view schematically showing an optical arrangement of an optical pickup apparatus according to a first embodiment of the present invention;

4 is a plan view schematically showing the photodetector of FIG.

FIG. 5 is a schematic view of a track error signal detector for detecting a track error signal with respect to the photodetector of FIG. 4; FIG.

6 is a graph for explaining a process of detecting a track error signal from which an offset is removed from the track error signal detector of FIG. 3;

7 is a view schematically showing another example of the track error signal detection unit of FIG. 5;

8 is a plan view schematically showing a photodetector according to a second embodiment of the present invention;

FIG. 9 is a schematic view of a track error signal detector for detecting a track error signal with respect to the photodetector of FIG. 7; FIG.

<Explanation of symbols for main parts of drawing>

50 ... light source 51 ... light path conversion means

55 ... Objective lens 57 ... Astigmatism lens

59 ... disc 60 ... photodetector

61, 63 ... first and second photodetector 80 ... track error signal detector

90,120 ... First circuit part 97 ... Summer part

100,130 ... 2nd circuit part 101,131 ... 1st total amplification part

103,133 ... 2nd total amplification part 105,135 ... 2nd differential part

107,137 ... Filter section 110,140 ... Secondary differential section

In order to achieve the above object, the present invention provides a light source for generating and emitting light; An objective lens for focusing incident light such that a light spot is formed on the recording surface of the disk; Optical path converting means disposed on an optical path between the light source and the objective lens to convert a traveling path of incident light; Four light receiving regions (E) (F) (G) disposed on one side of the optical path converting means for receiving and photoelectrically converting light through the objective lens and the optical path converting means, respectively. A first photodetector having H); Four light-receiving areas (A) (B) and (C) which are positioned around the first photodetector and are L-shaped so as to be dividedly disposed corresponding to each of the light-receiving areas (E), (F), (G) and (H). A second photodetector having (D); A track error signal detector for detecting a track error signal of the disc from the output signals of the first and second photodetectors, wherein the track error signal detector comprises: the first and second photodetectors A first circuit unit for outputting a track error signal including an offset by a phase difference detection method from the signal output from the signal; A second circuit unit for outputting a signal for correcting a track error signal including an offset from a signal output from the first or second photodetector; And a first differential part which differentially outputs the signals output from the first and second circuit parts and outputs a track error signal from which the offset is removed.

The present invention also provides a light source for generating and emitting light; An objective lens for focusing incident light such that a light spot is formed on the recording surface of the disk; Optical path converting means disposed on an optical path between the light source and the objective lens to convert a traveling path of incident light; Four light receiving regions (A) (B) and (C) disposed on one side of the optical path converting means to receive and photoelectrically convert light through the objective lens and the optical path converting means, respectively. A photodetector having D); A track error signal detector for detecting a track error signal of the disc from an output signal of the photodetector, wherein the track error signal detector comprises: a light receiving area (A) and a light receiving area (C); A first circuit section for generating a track error signal including an offset by a phase difference detection method by differentially combining the sum signal of the detection signal and the sum signal of the detection signals of the light receiving area (B) and the light receiving area (D); A second circuit unit outputting a signal for correcting a track error signal including an offset from the signal output from the photodetector; And a first differential part which differentially outputs the signals output from the first and second circuit parts, and outputs a track error signal from which offsets are removed.

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

3 is a view schematically showing an optical arrangement of an optical pickup apparatus according to a first embodiment of the present invention.

Referring to the drawings, the optical pickup apparatus according to the present invention includes a light source 50 for generating and emitting light, an objective lens 55 for focusing incident light to form an optical spot on the recording surface of the disk 59, and advancing incident light. And a track error signal detector 80 for detecting a track error signal of the disc 59. The light path converting means 51 converts the path, the light detecting means 60 for receiving the incident light, and the track error signal of the disc 59.

The light source 50 includes a surface light laser or an edge emitting laser that generates and emits light in a stacking direction of the semiconductor material layer.

The objective lens 55 is disposed between the light source 50 and the disk 59 to focus light incident from the light source 50 so as to form a light spot on the recording surface of the disk 59.

The light path converting means 51 is disposed on the light path between the light source 50 and the objective lens 55. It is preferable to include a beam splitter so that most of the light incident from the light source 50 toward the light path converting means 51 passes straight through and most of the light incident from the objective lens 55 reflects.

Here, it is also possible to include a polarizing beam splitter (not shown) for transmitting or reflecting the incident light to the optical path converting means 51 according to the polarization state. When the polarizing beam splitter is provided as described above, a quarter wave plate (not shown) for changing the polarization of incident light is further provided on the optical path between the polarizing beam splitter and the disk 59.

On the other hand, on the optical path between the light source 50 and the objective lens 55, it is preferable to further include a collimating lens 53 for converting the divergent light incident from the light source 50 side into parallel light. 3 shows an example in which the collimating lens 53 is disposed between the optical path converting means 51 and the objective lens 55.

Further, an astigmatism lens 57 is further provided on the optical path between the optical path converting means 51 and the light detecting means 60 to cause astigmatism so that a focus error signal can be detected by the astigmatism method. It is desirable to.

The light detecting means 60 is reflected from the disk 59 and receives the light passing through the objective lens 55 and the light path converting means 51 and converts the light into an electric signal. In this case, as shown in FIG. 4, the photodetector 60 includes a first photodetector 61 disposed on one side of the optical path converting means 51 and a circumference of the first photodetector 61. A second photodetector 63 located.

The first photodetector 61 is divided into four neighboring regions and consists of four light receiving regions E, F, G, and H which receive incident light and independently photoelectrically convert the light. The second photodetector 63 is disposed to correspond to each of the light receiving regions E, F, G, and H, and has four L-type light receiving regions A for photoelectric conversion of incident light. (B) (C) (D).

The track error signal detector 80 detects a track error signal of the disc 59 from the output signals of the first and second photodetectors 61 and 63.

The track error signal detecting unit 80 includes a first circuit unit 90 for detecting a track error signal including an offset by a phase difference detection method, and a second circuit unit 100 for outputting a signal for correcting a track error signal including an offset. And a first differential unit 110 for outputting the track error signal from which the offset is removed.

The first circuit unit 90 detects a track error signal including an offset from the detection signals of the first and second photodetectors 61 and 63 by a phase difference detection method. To this end, the first circuit unit 90 includes first and second differential amplifiers for differentially amplifying the light received by the first and second photodetectors 61 and 63, respectively, and the first and second amplifiers. And an adder 97 for summing output signals of the differential amplifiers.

In the first differential amplifier, for example, differential detection 91 of detection signals of the light receiving region A and the light receiving region B is performed. The detection signals of the light receiving region C and the light receiving region D are differentially amplified 92. Then, the two differential signals are summed (93). Therefore, the output signal of the second differential amplifier can be expressed as Equation (1). Here, each of the light receiving regions and their detection signals are indicated by the same symbol for convenience.

t1 = (A-B + C-D)

In the second differential amplifier, for example, differential detection 94 of the detection signals of the light receiving region E and the light receiving region F is performed. The detection signals of the light receiving region G and the light receiving region H are differentially amplified 95. Then, the two differential signals are summed (96). Therefore, the output signal of the first differential amplifier may be expressed as Equation 2. Here, each of the light receiving regions and their detection signals are indicated by the same symbol for convenience.

t2 = (E-F + G-H)

When the summation unit 97 adds the output signals of the first and second differential amplifiers, a track error signal including an offset is detected by a phase difference detection method, and the track error signal including the offset ( α ) May be expressed as in Equation 3.

α = (A-B + C-D) + (E-F + G-H)

As such, the track error signal including the offset output from the first circuit unit 90 ( α ) Is shown as shown in FIG. 6 as the objective lens 55 moves. This track error signal ( α As shown in the figure, as the amount of movement of the objective lens 55 increases, the track error signal ( α ) Has an offset in which the center potential increases.

Here, the x axis represents the objective lens shift amount (mm), and the y axis represents the detection signal amount at the predetermined step of the track error signal detection unit 80.

The second circuit unit 100 is the track error signal ( α Outputs a signal for correcting the offset included in. To this end, the second circuit unit 100 includes first and second summing amplifiers 101 and 103 for summing and amplifying detection signals of the first photodetector, and the first and second summing amplifiers 101. And a second differential unit 105 for differentially outputting the signal of the 103, and a filter unit 107 for outputting an offset correction signal by filtering the output signal of the second differential unit.

As illustrated in FIG. 5, the first summation amplifier 101 receives a detection signal of the light receiving area E and the light receiving area G by a predetermined gain. G ₁ Sum and amplify The second summing amplifier 103 receives the detection signals of the light receiving area F and the light receiving area H by a predetermined gain ( G ₂ Sum and amplify The second differential part 105 differentials the output signals of the first and second summing amplification parts 101 and 103. Therefore, the output signal t3 of the second differential unit 105 is expressed by Equation 4.

t3 = G1 * (E + G)-G2 * (F + H)

The output signal t3 is a track error signal (1) of the first circuit unit as the objective lens 55 moves. α Like), it is an AC signal.

The filter unit 107 may include a low pass filter for low-pass filtering the output signal t3 of the second differential unit 105 or a high frequency rejection filter for blocking high frequency components of the output signal t3.

Therefore, when the output signal t3 of the second differential part 105 passes through the filter part 107, the DC signal ( β Is converted to). At this time, the DC signal ( β ) May be expressed as in Equation 5. Here, Equation 5 shows an example in which the output signals of the first and second summation amplifiers 101 and 103 are respectively low pass filtered (LPF).

β = LPF {G1 * (E + G)-G2 * (F + H)}

At this time, the DC signal ( β ) Is changed as shown in FIG. 6 as the objective lens 55 moves.

The DC signal ( β That is, the offset correction signal ( β ) Gain G ₁ and G ₂ When properly adjusted, the inclination of the offset correction signal (indicated by the dotted line) is changed, and as shown in FIG. 6, the track error signal ( α ) Will match the offset contained in).

Therefore, the track error signal (by the phase difference detection method as described above in the first differential unit 110) α ) And the correction signal ( β ), The track error signal (detected by the first circuit unit 90) α The offset included in) is removed.

Therefore, the track error signal TES according to the present invention, from which the offset is removed, may be expressed as shown in Equation 6.

TES = (A-B + C-D) + (E-F + G-H)-LPF {G1 * (E + G)-G2 * (F + H)}

The track error signal TES is converted as shown in FIG. 6 according to the movement of the objective lens 55.

Here, the correction signal ( β As shown in FIG. 7, the light receiving area A and the light receiving area C, and the light receiving area B and the light receiving area D may be obtained in the same manner as described above. It may represent an error signal TES.

FIG. 8 is a view schematically showing a photodetector according to a second embodiment of the present invention employed in the optical pickup device of FIG. 3, and FIG. 9 is a second embodiment of the present invention employed in the optical pickup device of FIG. The track error signal detection unit 80 according to the drawings is schematically shown. This embodiment is the same as the optical pickup device of the first embodiment described with reference to FIG. 3, wherein the light detecting means 60 are arranged to be adjacent to each other, and four light receiving regions for receiving the incident light and independently photoelectrically converting them ( A) (B) (C) (D) is a photodetector 80, and the track error signal detecting unit 80 is provided correspondingly.

As illustrated in FIG. 9, the track error signal detection unit 80 includes a first circuit unit 120 for detecting a track error signal including an offset by a phase difference detection method, and a second circuit unit 130 for outputting a correction signal. And a first differential part 140 that differentials the output signals of the first circuit part 120 and the second circuit part 130.

In the first circuit unit 120, a phase difference detection method is performed by differentially adding a sum signal of detection signals of the light receiving area A and the light receiving area C and a sum signal of detection signals of the light receiving area B and the light receiving area D. Track error signal with offset by α ).

Therefore, the track error signal containing this offset ( α ) May be expressed as in Equation 8. Here, each light receiving area and its detection signal are indicated by the same symbol for convenience.

α = (A-B + C-D)

At this time, the track error signal ( α ) Is the track error signal of FIG. 6 according to the first embodiment of the present invention. α Similarly, the center potential is offset in accordance with the movement amount of the objective lens 55.

The second circuit unit 130 includes a track error signal including an offset from the signal output from the photodetector 60 ( α Outputs a signal to calibrate).

To this end, the second circuit unit 130 is a second to differential the output signal of the first and second summing amplifiers (131, 133) and the first and second summing amplifier (131, 133) And a differential filter 135 and a filter 137 for filtering the output signal of the second differential 135 to output an offset correction signal.

The first summing amplifier 131 receives a detection signal of the light receiving area A and the light receiving area C by a predetermined gain ( G ₁ Sum and amplify The second summing amplifying unit 133 may be configured to obtain a detection signal of the light receiving area B and the light receiving area D by a predetermined gain. G ₂ Sum and amplify

The filter unit 137 filters the output signal of the second differential unit 135. Here, since the filter unit 137 is substantially the same as the filter unit 107 according to the first embodiment of the present invention described with reference to FIG. 5, a detailed description thereof will be omitted.

The output signal of the second circuit unit 130 as described above is a direct current signal ( β ) Can be expressed as Equation (8).

β = LPF {G1 * (A + C)-G2 * (B + D)}

Therefore, this DC signal ( β , That is, the correction signal ( β Benefit of G ₁ and G ₂ If properly adjusted, the correction signal of Fig. 6 according to the first embodiment of the present invention ( β Like the track error signal () α A correction signal can be obtained that matches the offset at which the center potential of e) increases.

The first differential unit 140 includes a track error signal including an offset by a phase difference detection method ( α ) And the correction signal ( β ) Is differentially outputted, and according to the first embodiment of the present invention, the track error signal TES from which the offset is removed from the output signal of the first circuit unit 120 is output.

Therefore, the track error signal TES according to the present embodiment in which the offset is removed may be represented by Equation 9.

TES = (A-B + C-D)-LPF {G1 (A + C)-G2 (B + D)}

The track error signal TES is changed as shown in FIG. 6 in accordance with the movement of the objective lens 55 as in the first embodiment of the present invention.

The optical pickup apparatus according to the present invention as described above can remove the offset of the track error signal by using the correction signal detected by the second circuit portion, so that the correct track position of the disk can be followed, thereby Information signals can be recorded / reproduced accurately.

In addition, since the light received by the photodetector according to the present invention is used when recording / reproducing the information signal, the light utilization efficiency is high.

Claims (10)

A light source for generating and emitting light; An objective lens for focusing incident light such that a light spot is formed on the recording surface of the disk; Optical path converting means disposed on an optical path between the light source and the objective lens to convert a traveling path of incident light; Four light receiving regions (E) (F) (G) disposed on one side of the optical path converting means for receiving and photoelectrically converting light through the objective lens and the optical path converting means, respectively. A first photodetector having H); Four light-receiving areas (A) (B) and (C) positioned around the first photodetector, each of which is L-shaped so as to be dividedly disposed corresponding to each of the light-receiving areas (E), (F), (G), and (H). A second photodetector having (D); An optical pickup apparatus comprising: a track error signal detector for detecting a track error signal of the disc from output signals of the first and second photodetectors. The track error signal detector, A first circuit unit for outputting a track error signal including an offset from the signals output from the first and second photodetectors by a phase difference detection method; A second circuit unit for outputting a signal for correcting a track error signal including an offset from a signal output from the first or second photodetector; And a first differential part which differentially outputs the signals output from the first and second circuit parts, and outputs a track error signal from which offsets are removed. The method of claim 1, wherein the first circuit portion, A first differential amplifier for differentially amplifying the sum signal of the detection signals of the light receiving area (A) and the light receiving area (C) and the sum signal of the detection signals of the light receiving area (B) and the light receiving area (D); A second differential amplifier for differentially amplifying a sum signal of the detection signals of the light receiving area E and the light receiving area G, and a sum signal of the detection signals of the light receiving area F and the light receiving area H; And an adder configured to add the output signals of the first and second differential amplifiers to detect a track error signal including an offset by a phase difference detection method. The method of claim 1, wherein the second circuit portion, The detection signals of the light receiving area E and the light receiving area G G ₁ A first summing amplifying unit for summing and amplifying with s); The detection signal of the light receiving area F and the light receiving area H is G ₂ A second summing amplification unit for summing amplified by); A second differential part which differentials an output signal of the first and second summing amplification parts; And a filter unit for filtering an output signal of the second differential unit and outputting an offset correction signal. The method of claim 1, wherein the second circuit portion, The detection signals of the light receiving area A and the light receiving area C G ₁ A first summing amplifying unit for summing and amplifying with s); The detection signal of the light receiving area B and the light receiving area D is G ₂ A second summing amplifying unit for summing and amplifying with s); A second differential part which differentials an output signal of the first and second summing amplification parts; And a filter unit for filtering an output signal of the second differential unit and outputting an offset correction signal. The optical pickup apparatus of claim 3 or 4, wherein the filter unit comprises a low pass filter for low pass filtering the output signal of the second differential unit. The optical pickup apparatus of claim 3 or 4, wherein the filter unit comprises a high frequency elimination filter that blocks high frequency components of an output signal of the second differential unit. A light source for generating and emitting light; An objective lens for focusing incident light such that a light spot is formed on the recording surface of the disk; Optical path converting means disposed on an optical path between the light source and the objective lens to convert a traveling path of incident light; Four light receiving regions (A) (B) and (C) disposed on one side of the optical path converting means to receive and photoelectrically convert light through the objective lens and the optical path converting means, respectively. A photodetector having D); An optical pickup apparatus comprising: a track error signal detector for detecting a track error signal of the disc from an output signal of the photodetector. The track error signal detector, A track error including an offset by a phase difference detection method by differentially combining the sum signal of the detection signals in the light receiving area A and the light receiving area C and the sum signal of the detection signals in the light receiving area B and the light receiving area D. A first circuit unit for outputting a signal; A second circuit unit outputting a signal for correcting a track error signal including an offset from the signal output from the photodetector; And a first differential part which differentially outputs the signals output from the first and second circuit parts, and outputs a track error signal from which offsets are removed. The method of claim 7, wherein the second circuit portion, The detection signals of the light receiving area A and the light receiving area C G ₁ A first summing amplifying unit for summing and amplifying with s); The detection signal of the light receiving area B and the light receiving area D is G ₂ A second summing amplifying unit for summing and amplifying with s); A second differential part which differentials an output signal of the first and second summing amplification parts; And a filter unit for filtering an output signal of the second differential unit and outputting an offset correction signal. The optical pickup apparatus of claim 8, wherein the filter unit comprises a low pass filter for low pass filtering the output signal of the second differential unit. The optical pickup apparatus of claim 8, wherein the filter unit comprises a high frequency elimination filter that blocks high frequency components of an output signal of the second differential unit.

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