MXPA96002266A - Opt capture device - Google Patents

Abstract

An optical acquisition device including a light source for irradiating a light beam, a diffraction element for separating an irradiated light beam from the light source into at least three beams, namely a main beam and two side beams, a target lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a first four-segment light receiving portion for receiving the main beam reflected by the recording surface of the optical recording means and second and third light receiving portions positioned on either side of the first light receiving portion to receive the reflected side beams by the registration surface of the optical medium, and a calculation unit for generating a first tracking signal based on the respective outputs of the first light receiving portion to generate u a second tracking signal based on the outputs of the second and third receiving portions of the

Description

"OPTICAL CAPTATION DEVICE" BACKGROUND OF THE INVENTION Field of the Invention This invention relates to an optical pick-up device for recording and / or reproducing an optical recording medium, a reproduction apparatus and a recording apparatus for an optical recording medium. More particularly, it relates to an apparatus capable of recording and / or reproducing multiple classes of different optical discs in track inclination by one and the same apparatus.

DESCRIPTION OF THE RELATED TECHNIQUE Up to now, in an apparatus for reproducing an optical disk such as a compact disc, a three-beam method has been used as a system for detecting tracking error signals. This system divides a light beam irradiated by a semiconductor laser element by means of a diffraction grating in three beams, namely a main beam and both side beams. The main beam is irradiated on a recording track of an optical disc, while both side beams are irradiated at disc positions off-center by a quarter of a track on both sides of the recording track. The light beams irradiated in the optical disc are reflected by the recording surface of the recording medium to be received by a photodetector. This photodetector is constituted by a first portion of the photodetector to receive a main beam and second and third portions of the photodetector to receive both lateral beams. The tracking error signal is detected by finding the difference between the signals received by the second and third portions of the photodetector. Recently, this optical disk has been investigated where data can be recorded up to a high density to record the high precision data, such as stationary images or movable images. With this optical disc, it can be proposed to adjust the inclination of the track to approximately 0.8 micrometers instead of 1.6 micrometers that are conventionally used, or to form a recording layer of a narrower track inclination as multiple layers. The optical disk, recorded to a high density, is not limited to a re-production type only, but an optical disk capable of being rewritten, such as a disk of phase change type. This disc having a guide slot can also be visualized as an optical disc capable of being rewritten. However, it is difficult with an optical disk for high density recording to detect the tracking error signals by the aforementioned three-beam system. That is, since the inclination of the track is of limited width, the registration of the lateral zones of the three irradiated areas on the registration surface of the optical disc becomes difficult. Also, if the high density recording layer is formed as multiple layers, there is a problem of an offset which will occur in the tracking error signal due to leakage or escape of reflected light from the layer other than the layer that is being recorded or played. In addition, if the optical disk capable of being rewritten is a disk of phase change type and portions recorded and not recorded are produced on the disk, a noise is produced with the three-beam method due to the difference in reflectance in the Registered and unregistered portions, making it difficult in this way to detect the correct tracking error signals.

OBJECT AND SUMMARY OF THE INVENTION In view of the current state of the art illustrated above, an object of the present invention is to provide an apparatus capable of carrying out selective registration and / or reproduction in or from multiple classes of optical discs, such as optical discs with different track inclinations. An optical acquisition apparatus according to the present invention includes a light source for irradiating a light beam, a diffraction element for separating an irradiated light beam from the light source towards at least three beams, namely a main beam and two side beams, an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a first receiving portion of four segment light to receive the main beam reflected by the recording surface of the optical recording medium, and a second and third light receiving portions positioned on either side of the first light receiving portion to receive the side beams reflected by the surface registration of the optical recording medium, and a calculation unit for generating a first tracking signal based on the respective outputs of the first light receiving portion and for generating a second tracking signal based on the outputs of the second and third portions light receptors. A tracking servo system in an optical disc recording and / or reproducing apparatus according to the present invention includes a light source for irradiating a light beam and diffraction element to separate an irradiated light beam from the light source towards at least three beams, namely a main beam and two side beams, an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium, a light receiving unit having a first four segment light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium, and a second and third light receiving portions positioned on either side of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium, a calculation unit to find a plurality of tracking error signals based on the outputs of the first, second and third light receiving portions, a discrimination unit for discriminating the class of optical discs, a switching unit for selecting one of the calculated tracking error signals by the calculation unit based on a signal from the discrimination unit, and a driving unit for driving a target lens based on the tracking error signal selected by the switching means. The discrimination unit discriminates the classes of at least two kinds of optical discs with different track inclinations, and the signal processing unit responds to the results of the discrimination to change the calculation operations in order to obtain an error signal of tracking from a detection signal of the photodetector unit, so that at least two kinds of optical disc can be reproduced by simplified adjustment operations.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates a schematic structure of an optical disk recording and / or reproducing apparatus encompassing the present invention. Figure 2 illustrates a schematic structure of an optical pickup device encompassing the present invention. Figures 3 and 4 illustrate a bi-axial mechanism of a target lens in the optical pickup apparatus.

Figure 5 illustrates a first mode of a tracking servo system in accordance with the present invention. Figures 6A and 6B illustrate the radiation state of three beams in signal pits of an optical disk. Figure 7 illustrates a second embodiment of a tracking servo system in accordance with the present invention. Figure 8 illustrates a third embodiment of a tracking servo system in accordance with the present invention. Figure 9 illustrates a schematic structure of an optical disc recording and / or reproducing apparatus having a unit that varies the aperture ratio in accordance with one embodiment of the present invention. Figures 10A and 10B are perspective views showing a light shield ring used with the relative aperture varying unit of Figure 9 and the movement mechanism for the light shield ring. Figures HA and 11B show the manner in which the relative aperture is varied by the light shield ring shown in Figures 10A and 10B.

Figure 12 is a graph showing the relationship between the aperture ratio of the objective lens and the spatial frequency. Figure 13 is a perspective view showing a light shield plate used as the unit varying the aperture ratio of Figure 9 and a movement mechanism for the light shield. Figure 14 illustrates an objective lens and a movement mechanism for the objective lens, wherein the objective lens has lens portions having different aperture ratios and is used as the unit that varies the aperture ratio of Figure 9.

DESCRIPTION OF THE PREFERRED MODALITIES With reference to the drawings, the preferred embodiments of the optical pick-up device according to the present invention will be explained in detail. Figure 1 schematically shows an optical disc reproducing apparatus according to the present invention. An optical disc reproducing apparatus 10 is a so-called compatible optical disc reproducing apparatus for reading and reproducing information signals from an optical disc having a track inclination of 1.6 micrometers and a substrate thickness of 1.2 micrometers, such as a compact disc, and a dual layer optical disc 11 having a track inclination of approximately 0.8 micrometer and having two layers of information signal oriented in the same reading direction. An optical pickup device 13 irradiates a laser light beam towards these optical discs having different track inclinations and different substrate thicknesses to reproduce information signals from the tracks formed in the information signal layers. Referring to Figure 2, the optical pickup device 3 includes a light source 21 that radiates a laser beam, such as a laser diode and a target lens 25 to focus on the laser beam on the multi-class information signal layers of the laser. optical discs having different track inclinations, of which only the double-layer optical disc 11 is shown in Figure 2. The double-layer double optical disc 1 shown in Figure 2 has a first layer of information signal and a second layer 11b of information signal. The optical pickup device 13 also includes a photodetector 24 for receiving light reflected from the optical disk, for converting it into electrical signals, and a disk discrimination unit 27 for discriminating the optical disk class. The optical pickup device 13 further includes a detection signal processor 26 responsive to the class of optical disc discriminated by the disk discrimination unit 27 in order to change the calculation operations to calculate the tracking error signals from the Detected signals from the photodetector 24, to produce tracking error signals in addition to a focus error signal and main playback signals. The tracking error signals and the focus error signal obtained by the detection signal processor 26 of the optical pickup device 13 are supplied to a servo circuit 16 of Figure 1. The servo circuit 16 handles the tracking control and the servo control in response to these signals. Specifically, a focus driving signal is applied in the optical pickup unit 13 to a bi-axial mechanism 20 which retains the objective lens 25 for driving the objective lens 25 in a direction in and out of contact eg with the 11 double-layer optical disc to handle focus control. Also, a tracking drive signal is applied to the bi-axial mechanism 20 to drive the objective lens 25 radially for example from the double layer optical disk 11 in order to operate the focus control. A driving signal is generated by extracting the low frequency components from the tracking error signal to drive a thread mechanism to move the optical pickup device 13 in its entirety radially for example from the double layer optical disk 11. The main reproduction signal obtained by the detection signal processor 26 is processed with demodulation for EFM and decoding CIRC towards the digital reproduction data which is then converted by a D / A converter 14 into an analog signal which is sent to a 15 exit terminal. The servo circuit 16 controls the rotation of a spindle motor 18 based on the clocks obtained from the main reproduction signals. The detailed structure and operation of the optical pickup device 13 will now be explained. Referring to Figure 2, a diffuse laser beam, irradiated by the optical source 21, is diffractioned by a diffraction grating 22 and thus separated into three beams, namely a beam of order 0 and the beams of order + 1. The laser beams, diffracted by the diffraction grating 22, are reflected by the beam splitter 23 and collimated by the collimator lens 19 to enter the objective lens 25. The objective lens 25 is controlled by tracking and focusing by the bi-axial mechanism 20 to converge the laser beams on the information signal layers of the optical disc, such as the first information signal recording layer Ia and the second layers 11b. information signal of double layer optical disc 11 to form three points. The three reflected laser beams of the first information signal recording layer Ia and the second information signal layers 11b of the double layer optical disk 11 arrive at a light receiving surface of the photodetector 24 through the objective lens 25 and the 23 beam splitter. The bi-axial mechanism 20 is of the axial sliding type as shown in Figures 3 to 5, wherein a movable part 30 is constituted by a coil 30A formed of a non-magnetic material. In the intermediate position of the coil 30A a bearing is formed 31 tubular adjusted axially. A coil is wound on the end peripheral surface of the coil 30A. 32 to form a ring around the bearing 31. The focusing coil 32 is used to move the movable part 30 in the focusing direction, ie, in a direction perpendicular to the surface of the disk. On the surface of the focusing coil 32 two sets of tracking coils 33A, 33B are formed in sealing contact with the focusing coil 32 to move the movable part 30 in the tracking direction, ie, along the radius of the disk. These tracking coils 33A, 33B are wound around an axis extending perpendicular to the winding axis of the focusing coil 32, so that four rings are formed on the outer peripheral surface of the coil 30A. The intermediate portion of the bi-axial mechanism 20 is traversed by a supporting arrow 39. A stepped hole 43 is formed parallel to the central axis of the supporting arrow 39 in the coil 30A in an off-centered position with respect to the supporting arrow 39. Within this hole 43, a tubular body 35 of the lens is mounted within which the objective lens 25 is secured. The movable part 30, constructed in this way, has the support arrow 39 positioned vertically in the intermediate portion of a stationary yoke 38 of a magnetic material guided and inserted into a central hole of the bearing 31, so that the movable part 30 is sustained to slide along and for rotation about the support arrow 39. On the lower surface of the stationary yoke 38 an annular permanent magnet 40 is secured in intimate contact therewith around the support arrow 39 as the center. A first yoke 42 having a projection 41 is secured to the lower end face of the permanent magnet 40. In the stationary yoke 38, a second yoke 44 is formed in a protruding manner so as to face the projection 41 of the first yoke 42; inner side of coil 30A. The stationary yoke 38, the permanent magnet 40, the first yoke 42 and the second yoke 44 constitute a magnetic circuit. The focusing coil 32 and the tracking coils 33A, 33B are placed in a magnetic space defined between the first yoke 42 and the second yoke 44. The stationary yoke 38 has the hole 43 larger in diameter than the outer diameter of the tubular body 35 of the lens retained by the coil 30A. An upper end of the tubular body 35 of the lens is guided and inserted into this hole 43. Figures 5 and 6 show a first mode of servo tracking to play multiple discs having different track inclinations. With the first present embodiment of the optical disk recording and / or reproducing apparatus, it is possible to reproduce an optical disk having a substrate thickness of 1.2 millimeters and a track inclination of 1.6 microns, an optical disk having a substrate thickness of 1.2 millimeters and a track inclination of 0.8 micrometer, and an optical disk having a substrate thickness of 0.6 millimeter and a track inclination of 0.8 micrometer. In addition, it is possible to register a write-capable phase change optical disc having a substrate thickness of 0.6 millimeter and a track inclination of approximately 0.8 micrometer. Referring to Figure 5, the optical disc recording and / or reproducing apparatus of the first embodiment has a light receiver 24 for receiving the irradiated light beam from the light source 21 and reflected from the surface of the disk signal. optic through the objective lens 25, the collimator lens 19 and the beam splitter 23 after irradiation of the optical disk 11 through the diffraction grating 22, the beam splitter 23, the collimator lens 19 and the objective lens 25 , and a signal detector 26 for generating two kinds of tracking error signals based on the light volume detection signal from the receiver 24. The optical disc recording and / or reproducing apparatus also includes a discrimination unit 27. of disk to discriminate the classes of registered or reproduced optical discs, a switch 28 for selecting the error signals from the tracking of the signal detector 26 and a driving unit 29 of the objective lens for driving the objective lens 25 based on the selected tracking error signal. The light receiver 24 has from first to third receivers 51 to 53 of light to receive the light beams separated by the diffraction grating 22 in three portions and reflected by the optical disk 11. The first light receiver 51 receives the main beam (light of order 0) of the three separate light beams and devide at least two areas Al and Bl. The second and third light receivers 52, 53 receive two lateral beams (light beams of order +1) of the three separate light beams and have two separate portions each of which is divided into the areas El, Gl and Fl, Hl . From the outputs of the receivers 51 to 53, the outputs El, Gl of the receiver 52 and the outputs Fl, Hl of the receiver 53 are respectively summed in the summing apparatuses 54 and 58, the outputs of which are supplied to a comparator 61 to generate a first trace error signal. The outputs El, Gl of the receiver 52 are supplied to a comparator 55, while the outputs Fl, Hl of the receiver 53 are supplied to a comparator 57. A difference output of the comparator 55 and a difference output of the comparator 57 that are fed through a variable gain amplifier 59 they are summed together and a resulting summation output is further supplied via a variable advance amplifier 60 to a comparator 62. A difference output of the comparator 62 provides a second tracking error signal .

Figures 6A and 6B illustrate the state of irradiation of the different track inclination discs with the three separate light points. Figure 6A illustrates an example of an optical disc having a track inclination of about 0.84 micrometer, wherein the side beams are illuminated in the off-center positions by half the slope of the track with respect to the main beam. Figure 6B shows an example of an optical disc having a track inclination of 1.6 micrometers where the side beams are illuminated in off-center positions by a quarter of the track inclination with respect to the main beam. With the optical disc of Figure 6A, since the track inclination is half that of the optical disc of Figure 6B, decentration frequently occurs due to the deviation of the optical axis of the objective lens from decentering due to the inclination of the optical disc. If judged by the disk discrimination unit 27 that an optical disk which is an optical disk having a track inclination of 1.6 microns, a first tracking error signal is selected, which is a differential output of the comparator 61. another part, if judged by the disk discrimination unit 27 that an optical disk is a disk-1. optical one having a track inclination of 0.8 micrometer, a second tracking error signal is selected which is a differential output of the comparator 62. By detecting the tracking error signals as described above, a method of three beams for the reproduction of a compact disc, while a differential symmetric mounting method is applied, removing unnecessary decentering for the reproduction of a record-only high-density disc, or a record / playback disc. Therefore, a compatible optical disc recording and / or reproducing apparatus can be obtained, using a common optical system and simply switching calculation operations. Figure 7 shows a second mode of the tracking service for recording or playing multiple discs having different track inclinations. The optical disc recording and / or reproducing apparatus in the second present mode is similar to that of the first embodiment with the exception of the structures of the light receiver 24 and the signal detector 26. The light receiver 24 has first or third receivers 71 to 73 of light to receive the three light beams separated by the diffraction grating 22 and reflected by the optical disk 11. The first light receiver 71 receives the main beam (light of order 0) of the three separate light beams and is divided into four areas of A2, B2, C2 and D2. The second and third receivers 72, 73 light receive two lateral beams (light beams of order +1) of the three separate light beams and have portions E2, F2 to receive the side beams of the order +1 of the three separate light beams. From the outputs of the light receivers 71 to 73, the outputs of the light receivers 72 and 73, that is, the outputs of the areas E2 and F2, are supplied to a comparator 74 where an EF difference output is produced. , that is, the first signal of tracking error. From the outputs of the first light receiver 71, the outputs of the areas A2 and C2 are summed by an adder 75, while the outputs of the areas B2 and D2 are summed by an adder 76. The phase differences of the outputs of the summers 75, 76 are compared by a phase comparator 77 to produce a second tracking error signal. If judged by the disk discrimination portion 27 and a disk is an optical disk having a track inclination of 1.6 microns, the first tracking error signal, which is a difference output of the comparator 74, is selected. judge that a disc is an optical disc that has a track inclination of 0.8 micrometer, the second tracking error signal is selected, which is a difference output of the comparator 77. In the second mode, similar to the first mode, a three-beam method is applied to reproduce, for example a compact disc, while a tracking error detection system is applied based on the phase difference, advantageous for removing the off-center, in order to register or reproduce an optical disc of high recording density. Figure 8 shows a third mode for a follow-up service to record and play multiple discs with different track inclinations. The optical disk recording and / or reproducing apparatus in the third present mode is similar to that of the first and second modes with the exception of the structures of the light receiver 24 and the signal detector 26. The light receiver 24 has first to third light receivers 81 to 83 to receive the three light beams separated by the diffraction grating 22 and reflected by the optical disk 11. The first light receiver 81 receives the main beam (light of order 0) of the three separate light beams and is divided into four areas of A3, B3, C3 and D3. The second and third light receivers 82, 83 receive two side beams (light beams of order +1) of the three separate light beams and have two portions each of which is divided into E3, G3 and F3, H3. From the outputs of the light receivers 81 to 83, the outputs E3 and G3 of the light receiver 82 and the outputs F3 and H3 of the light receiver 83 are summed by the adders 84, 92, respectively. The outputs of the adders 84, 92 (E3 + G3, F3 + H3) are supplied to a comparator 95 to produce a first tracking error signal. From the outputs of the first light receiver 81, the outputs A3, C3 are summed by an adder 86, while the outputs B3 and D3 are summed by an adder 89. The phase differences of the outputs of the summers 86 and 89 are they compare by a comparator 96 to produce a second tracking error signal. The outputs E3, G3 of the light receiver 82 are sent to a comparator 85, while the outputs F3, H3 of the light receiver 83 are supplied to a comparator 91. A difference output of the comparator 85 is added to a difference output. of the comparator 91 which has passed through a variable gain amplifier 93, and the resulting summation output is supplied through a variable gain amplifier 94 to a comparator 97.

The outputs A3, D3 of the light receiver 81 are summed by an adder 88, while the outputs B3, C3 of the light receiver 81 are summed by an adder 87. The outputs of the summers 87 and 88 are supplied to a comparator 90 , an output from which a comparator 97 is sent. With an output of the comparator 97, a third tracking error signal is detected. With the third embodiment present, the three-beam method is applied to play a compact disc, for example, while the method of detecting tracking error signal based on phase difference is applied, advantageous for removing the off-center, for the reproduction record of a high-density optical disk. In addition, in the present embodiment, detection of the tracking error signal of the differential symmetric mounting system is applied to register or reproduce, for example, an optical disk capable of being rewritten of the phase change type. Therefore, the same optical pickup device can be used to record or reproduce multiple classes of optical discs. Then, with the optical disk recording and / or reproducing apparatus of the present invention, an optical disk with a substrate thickness of 0.6 millimeter can be recorded or reproduced, such as a first optical disk, for example with a track inclination of 0.8. micrometer. For this recording or reproduction, it is used as the light source 21, a semiconductor laser that radiates a laser beam with a wavelength, for example, of 635 nm. The objective lens 25 has an aperture ratio of, for example, 0.52. Therefore, if a second optical disc having a substrate thickness of 1.2 millimeters such as a compact disc is used, a spherical aberration is generated due to errors in the thickness of the substrate, so that correct reproduction of the substrate can be achieved. Registered data Accordingly, with the present embodiment of the optical disk recording and / or reproducing apparatus, the disk discrimination unit 27 sends an optical disk detection output to both the changeover switch 28 which selects the desired tracking error signal as a variable aperture control unit 100, of relative aperture, as shown in Figure 9. If fed with a detection output specifying a first optical disk with a substrate thickness of 1.2 millimeters, the relative aperture variable control unit 100 it forms a pulse that excites the corresponding motor and sends the pulse to a stepper motor 102 of a unit 101 which varies the variable ratio shown in FIG. 10a. This rotates the variable speed motor 102 in one direction to move a light shield ring 103 towards a light path of the laser beam, so that the rotational force of the variable speed motor 102 is transmitted through a gear portion 105a. which meshes with a gear 104a of a rotary gear 104 towards a ring slider 105. Therefore, the light shield ring 103 is controlled to move above the objective lens 25 together with the ring slider 105 as shown in Figure 10B. The light shield ring 103 therefore protects a portion of the irradiated laser beam from the objective lens 25 by its light shield portion 103b to vary the relative aperture of the objective lens 25 to 0.37 (corresponding to 70 percent of the relative aperture 0.52) for the first optical disc. The protected portion of the laser beam is through the outer peripheral portion and corresponds to 30 percent of the entire laser beam. Therefore, during the reproduction of the second optical disc, the light shield ring 103 is controlled to move above the objective lens 25 so that a portion of the laser beam from the objective lens 25 is protected as the laser beam is illuminated towards the second optical disk as shown in FIG. This prohibits spherical aberration during reproduction of the optical disk having a substrate of increased thickness due to errors in substrate thicknesses. Specifically, if the second optical disk having the objective lens 25 with the relative aperture maintained at 0.52 is reproduced, an aberration in the wavefront of approximately 0.3 rms occurs - due to the error of the substrate thickness of 0.6 mm, producing from this Thus, a significant distortion in the spatial frequency characteristics, as indicated by the circle signals O in the graph of Figure 12. Conversely, if the relative aperture of the objective lens 25 is controlled to 0.37 by the protective ring 103 of light, the aberration of the wavefront decreases by approximately 0.07 rms -, thereby eliminating the distortion in spatial frequency characteristics, as shown by the marks or signals | ~ | in the graph of Figure 12. Meanwhile, the marks or signals indicate the characteristics of the spatial frequency in case the reproduction is carried out using the optical system dedicated to the second optical disk. Comparison of signs or marks <; > and \ ~~ reveals that the two characteristics are similar to each other at approximately 1100 / millimeters. If the relative aperture of the objective lens 25 is controlled by the light shield ring 103 to 0.37, the spherical aberration can be decreased to a fourth relative aperture power ie approximately 25 percent, as compared to the spherical aberration generated at reproducing the second objective lens with the relative aperture of the objective lens 25 remaining unchanged at 0.52. Therefore, it becomes possible to sufficiently reproduce the second optical disk having a different substrate thickness than that of the first disk, using the optical system for the first optical disk. If fed with a detection output specifying a first optical disk with a substrate thickness of 0.6 millimeter, the relative aperture variable control unit 100 forms a corresponding motor exciter pulse and sends the pulse to the stepper motor 102 of a unit 101 varying the variable ratio shown in Figure 10a. This rotates the stepper motor 102 in one direction to move the light shielding ring 103 out of the light path of the laser beam, so that the rotational force of the variable speed motor 102 is transmitted through the meshing gear 105a. with the gear portion 103a of the rotary gear 104a towards the ring slider 105. Therefore, the light shield ring 103 moves away from the objective lens 25 together with the ring slider 105. Therefore, the laser beam of the objective lens 25 can be removed on the first optical disk with the thickness from the substrate of 0.6 millimeter, without being protected as shown in Figure 11B. In this case, the wavelength of the laser beam is 635 nm, and the relative aperture of the objective lens 25 is 0.52 so that the spatial frequency is equal to 1500 / millimeters, as shown by the x-signals in the Figure 12, and therefore, the first optical disk having a small log hole size can be reproduced satisfactorily. It will be seen from the foregoing that, with the optical disc recording and / or reproducing apparatus according to the present invention, the light shielding ring 103, which protects a portion of the laser beam from the objective lens 25, is provided in FIG. the optical system for the first optical disk having a substrate thickness of 0.6 millimeter, and is used only for reproduction of the second optical disk having a substrate thickness of 1.2 millimeters to protect a portion of the irradiated laser beam from the objective lens 25 for variablely controlling the relative aperture of the objective lens 25 to conform to the second optical disk to allow the reproduction of two different kinds of optical discs having different substrate thicknesses. Since the two kinds of optical discs with different substrate thicknesses can be reproduced in this way, the optical disc reproducing apparatus can be improved in application universality. A second embodiment of the present invention related to varying the relative aperture in the registration and / or reproduction of the optical disc according to the present invention will now be explained. In the first prior embodiment, the relative aperture of the objective lens 25 is variablely controlled by the light shield ring 103 and the ring slider 105. In the second present embodiment of the optical disc recording and / or reproducing apparatus, a pair of light protection plates 106, 109 as shown in the sample in Figure 13 is used to protect a portion of the laser beam. of the objective lens 25, using a pair of light shielding plates 106, 109 as shown in Figure 13, to variably control the relative aperture of the objective lens. With the exception of the mechanism related to this construction, the recording and / or reproducing apparatus of the optical disc of the second present mode is similar in structure to the optical disc recording and / or reproducing apparatus of the first previous embodiment, only the aforementioned mechanism is explained in relation to the apparatus of recording and / or reproducing the optical disc of the second present mode, while a detailed description of the remaining portion is omitted for reasons of clarity. The unit 101 varying the relative aperture provided in the second present embodiment of the optical disc recording and / or reproducing apparatus, is constituted by the stepper motors 107, 110 for controlling the movement of the plates 106, 109, protective of light as shown in Figure 13. The light shielding plates 106, 109 are placed in a straight line perpendicular to an irradiated laser beam of the objective lens so that one end of the plates is facing each other. Part of the portions of the interior surface consecutive to the facing ends of the light protection plates 106, 109 is designated as light protection portions 106b, 109b to protect a portion of the irradiated laser beam from the objective lens. The undersides of the light protection plates 106, 109 provided with rack gears 106a, 109a are designed to mesh with the gear portions 108a, Illa of the rotary gears 108, 111 provided in the arrows 107a, 110a. rotating motors 107, 110, of gradual speed, respectively.

The above-described structure of the unit 101 varying the relative aperture is controlled to be driven by a motor driver pulse supplied from the relative aperture variation control unit 100 in response to a detection output of the discriminating unit 27. disk. That is, if it is powered from a disk discrimination circuit 27 with a detection output that specifies the reproduction of the first optical disk hg the substrate thickness of 1.2 millimeters, the control unit 100 would remain the relative aperture generating excitation pulses of motor for rotating the motors 107, 110 of gradual speed in one direction to reduce the space delimited between the facing ends of the light protection plates 106, 109. These motor drive pulses are supplied to the stepper motor 107, 110. This drives the motors 107, 110 of gradual speed toward rotation. The rotational force of the stepper motors is transmitted through the gear portions 108a, gear wheel I of the gears 108, 111 to the rack gear portions 106a, 109a as the light protection portions 106, 109. The light protection plates 106, 109 are controlled to move to hide part of the objective lens. The scale for concealing the objective lens 25 by the light protection plates 106, 109 is scaled to a scale which will provide a relative aperture of the objective lens 25 of 0.37 equal to the relative aperture for the second objective lens 25. By controlling the movement of the light protection plates 106, 109 in this manner, part of the irradiated laser beam of the objective lens 25 is protected by the light protection portions 106b, 109b of the plates. 106, 109 of light protection to graduate the relative aperture of 0.37 lens objective 25. Therefore, the second optical disk with the substrate thickness of 1.2 millimeters can be reproduced correctly, such as in the first embodiment described above. Then, if it is fed from the disk discrimination circuit 27 with a detection output which specifies the reproduction of the first optical disk hg the substrate thickness of 0.6 millimeter, the control unit 100 which varies the relative aperture generates excitation pulses of motor to spin the motors 107, 110 of gradual speed in one direction to enlarge the space delimited between the facing ends of the light protection plates 106, 109. The drive pulses of the motor are supplied to the stepper motor 107, 110. This drives the motors 107, 110 of gradual speed toward rotation. The rotational force of the stepper motors is transmitted through the gear portions 108a, Illa of the gears 108, 111 to the rack gear portions 106a, 109a of the light protection portions 106, 109. The light protection plates 106, 109 are controlled to move to positions that do not protect the irradiated laser beam from the objective lens. This provides the relative aperture of the objective lens 25 of 0.52 which is equal to the relative aperture for the first optical disk. Therefore, the first optical disc can be reproduced correctly. A third embodiment of the present invention related to the variation of the relative aperture in the registration and / or reproduction of the optical disc according to the present invention will now be explained. With the optical disc recording and / or reproducing apparatus according to the present third embodiment, an optical lens hg two kinds of relative aperture is used as shown in Figure 14 instead of the objective lens 25 and the unit 101 of variable control in relative aperture and the objective lens hg a relative aperture corresponding to the substrate thickness of the optical disc being reproduced and used by switching. Since the recording and / or reproduction apparatus of the optical disc of the third embodiment present is similar in structure to the optical disc reproduction apparatus of the first and second embodiments except for the objective lens, the following description of the third embodiment is centered around the objective lens, while it is not done for reasons of clarity, no explanation of the remaining portions. That is, the aforementioned objective lens has a first portion 112 of light condensation having a relative aperture (0.52) for the first optical disk having a substrate thickness of 0.6 millimeter and a relative aperture (0.37) for the second disk optical that has a substrate thickness of 1.2 millimeters. The objective lens has a slider 114 for moving the objective lens in an optical path of the laser beam. The lower portion of the slide 114 has a rack gear which meshes with a rotary gear formed in the stepper motor. The rotational force of the stepper motor is transmitted through the rotary gear and the rack gear to the slide 114 to control the movement of the objective lens. If it is supplied with a detection output from the disk discrimination unit 27 with a detection output specifying the reproduction of the first optical disk with a substrate thickness of 0.6 mm, the control unit 100 varying the relative aperture supplies a motor exciter pulse towards the stepper motor to control the movement of the first portion 112 of light condensation towards the light path of the laser beam. This drives the stepper motor to rotate so that the first light condensation portion 112 of the objective lens is moved by the slider 114 in the light path of the laser beam. Since the first light condensing portion 112 has a relative aperture of 0.52 for the first optical disk, the first optical disk can be reproduced correctly by controlling the movement of the first portion 112 of light condensation in the light path of the laser beam. If it is powered with a detection output from the disk discrimination unit 27 with a detection output specifying the reproduction of the second optical disk with the substrate thickness of 1.2 millimeters, the control unit 100 varying the relative aperture supplies the motor exciter pulse towards the stepper motor to control the movement of the second portion 113 of light condensation towards the light path of the laser beam. This drives the stepper motor to rotate so that the second light condensing portion 113 of the objective lens is moved by the slider 114 in the light path of the laser beam. Since the second light condensing portion 113 has the relative aperture of 0.37 for the second optical disk, the second optical disk can be reproduced correctly by controlling the movement of the second portion 113 of light condensation in the light path of the laser beam. In the aforementioned embodiments, the relative aperture is variablely controlled for the first and second optical discs having different substrate thicknesses. However, since it is sufficient in the case of the light protection plates 106, 109 shown in Figure 13 to control the light protection scale of the laser beam variably, depending on the thickness of the substrate of the optical disk, it is possible to control variably three or more relative openings of the light protection scales of the objective lens, allowing the reproduction of three or more optical discs having different substrate thicknesses. In the embodiment of Figure 14 of an objective lens having the use compensation portions 112, 113 with two different relative openings, the light condensing portions with three or more different relative openings can be provided to allow the reproduction of three or more optical discs that have different substrate thicknesses. In the foregoing description, of the third modality, the light condensing portions 112, 113 are controlled to move by the slider 114. However, it is possible to provide a rotary arrow between the light condensation portions 112, 113, using the biaxial sliding type arrow mechanism shown in FIG. Figure 3, and controlling the objective lens to be rotated about the rotary arrow as the center of rotation to control the movement of the light condensation portions 112, 113 of the light path of the laser beam.

Claims (12)

CLAIMS:

1. An optical acquisition device comprising: a light source for irradiating a light beam; a diffraction element for separating an irradiated light beam from the light source into at least three beams, namely a main beam and two side beams; an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium; a light receiving unit having at least a first two-segment light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions positioned on either side of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium; a calculation means for generating a first tracking signal based on the respective outputs of the first light receiving portion and for generating a second tracking signal based on the outputs of the second and third light receiving portions. The optical pick-up device according to claim 1, wherein the calculating means calculates the first tracking error signal by calculating the phase differences between the signals obtained by adding two desired outputs of the four outputs of the first section receiving light, the calculation means calculates the second tracking signal by calculating the differences of the signals of the second and third light receiving portions. 3. The optical pickup device according to claim 1, further comprising means for varying the relative aperture of the optical lens. 4. The optical pickup device according to claim 1, wherein the objective lens has multiple lens portions having different relative apertures. 5. An optical pick-up device comprising: a light source for irradiating a light beam; a diffraction element for separating an irradiated light beam from the light source into at least three beams, namely a main beam and two side beams; an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium; a light receiving unit having a first four segment light receiving portion for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions of two segments positioned on either side of the first light receiving portion for receiving the side beams reflected by the recording surface of the optical recording medium; and a computing means for generating a first tracking signal based on the respective outputs of the first light receiving portion, a second tracking signal based on the differential outputs of the first, second and third light receiving portions, and a third tracking error signal by a differential output between the output of the second light receiving portion and an output of the third light receiving portion. 6. The optical pickup device according to claim 5, further comprising means for varying the relative aperture of the objective lens. 7. A tracking system for an optical disk recording and / or reproducing apparatus comprising: a light source for irradiating a light beam; a diffraction element for separating the irradiated light beam from the light source into at least three beams, namely a main beam and two side beams; an objective lens for converging the light beams separated by the diffraction element on a signal recording surface of the optical recording medium; a light receiving unit having a first four-segment light receiving position for receiving the main beam reflected by the recording surface of the optical recording medium and second and third light receiving portions positioned on either side of the first receiving portion of the light to receive the side beams reflected by the recording surface of the optical recording medium; a calculation means for finding a plurality of tracking error signals based on the outputs of the first, second and third light receiving portions; a means to discriminate the kinds of optical discs; a switching means for selecting one of the tracking error signals that is calculated by the calculation means based on a signal of a discrimination means; and means for driving a target lens based on the tracking error signal that is selected by the switching means. The monitoring servo system in the optical disk recording and / or reproducing apparatus according to claim 7, wherein the calculation means produces a first tracking error signal by calculating the phase difference between the signals obtained in addition to the two desired outputs of the four outputs of the first light receiving portion, the second calculation means produces a second tracking error signal based on the outputs of the second and third light receiving portions. The tracking servo system in the optical disk recording and / or reproducing apparatus according to claim 7, wherein the calculation means calculates the phase differences of the signals produced by adding two desired outputs of the four outputs of the first light receiving portion for producing a first tracking error signal, the calculation means, also calculates the differences of the signals of the second and third light receivers to produce a second tracking error signal. The monitoring servo system in the optical disc recording and / or reproducing apparatus according to claim 7, wherein each of the second and third light receiving portions is a two-segment light receiving portion, the medium calculation produces a first tracking error signal based on the respective outputs of the first light receiving portion and also producing a second tracking error signal based on the respective differential outputs of the first to third light receiving portions, the medium The calculation also produces a third tracking error of a differential output between an output of the second light receiving portion and an output of the third light receiving portion. The monitoring servo system according to claim 7, further comprising means for varying the relative aperture of the optical lens. The tracking servo system according to claim 7, wherein the objective lens has multiple lens portions having different relative apertures.