KR0176854B1 - Recording and reproducing apparatus adaptable disks in various thickness and optical pick-up thereof - Google Patents

Abstract

The present invention relates to a compatible recording / reproducing apparatus and an optical pickup apparatus for discs having different thicknesses, which can read various kinds of discs with one optical pickup apparatus using numerical aperture adjusting means. The optical pickup apparatus includes a light source; A beam splitter for separating light along a length from a light source; A focusing object lens for condensing parallel light passing through the beam splitter on the first and second disks; An optical detector positioned to receive from the sensor lens light incident through the beam splitter; Disk discriminating means for discriminating disks having different thicknesses through the reproduction signal processing means by the electrical signal output from the photodetector; A numerical aperture adjusting means provided between the beam splitter and the objective lens and configured to adjust at least two kinds of light from the beam splitter; A numerical aperture adjusting means driving device for driving the numerical aperture adjusting means corresponding to the type of the selected disk among the disks having different sizes by the disk discriminating means; A focus control device for performing a focus control function to adjust the focus position of the objective lens in accordance with the size of the selected disk; A motor controller for controlling the spindle motor in accordance with the selected disk; And a microcomputer for selectively controlling the numerical aperture adjusting means, the focus control device, the tracking control device, and the motor control device in accordance with the signal input from the disk discriminating means. The optical pickup device configured as described above can selectively reproduce both a CD disc of 1.2 mm in thickness and a high density DVD disc of 0.6 mm in thickness by using a simple numerical aperture adjusting means.

Description

Compatible recording / playback apparatus and optical pickup apparatus for discs of different thickness

1 is a diagram schematically showing the outline of a conventional optical pickup apparatus.

2 is a graph showing the beam intensity distribution on discs of different thicknesses.

3 is a diagram showing the outline of the optical pickup apparatus according to the first embodiment of the present invention;

4 is a schematic perspective view of an actuator which is a main part of the present invention.

(A) and (b) of FIG. 5 are perspective views of the liquid crystal shutter which is one of numerical aperture adjusting means.

FIG. 6A illustrates a case where a voltage is applied to an electrode of a liquid crystal shutter in N.W (Normal White) mode.

FIG. 6B is a diagram illustrating a case where a voltage is applied to an electrode of a liquid crystal shutter in N.B (Normal Block) mode.

Fig. 6C is a diagram showing a driving example for applying a voltage to the liquid crystal shutter.

(D) and (e) of FIG. 6 show changes in polarization direction in a TN liquid crystal.

6 (f) and (g) are diagrams showing a case where a voltage is applied to a liquid crystal shutter made of a PDLC liquid crystal layer.

7 (a) and 7 (b) show various embodiments of a liquid crystal pattern.

(A) of FIG. 8 is a graph showing the jitter amount with respect to the contrast ratio.

(B) of FIG. 8 schematically shows a glass plate on which a transparent electrode is formed.

(A) of FIG. 9 is a graph showing the change of the crosstalk according to the change of the numerical aperture of the objective lens.

(B) of FIG. 9 is a graph showing the change of the reproduction signal according to the change of the numerical aperture of the objective lens.

(C) of FIG. 9 is a graph showing the change of crosstalk with respect to contrast ratio.

(D) of FIG. 9 is a graph showing the relationship between the reproduction gain and the contrast ratio.

10 is a circuit diagram showing the entire circuit system of the optical pickup device applied to an embodiment of the present invention.

(A) of FIG. 11 schematically shows the interior of the photodetector.

Fig. 11B is a detailed circuit diagram of the reproduction signal processing means.

12 is a schematic flowchart of a disc discriminating means.

13 is a plan view of an optical pickup apparatus applied to an embodiment of the present invention.

14 is a perspective view of a pickup base.

FIG. 15 is a perspective view showing a carrier which is moved at the same time by installing the pickup base of FIG.

16 is an exploded perspective view showing an iris-type shutter which is one of the numerical aperture adjusting means.

(A) and (b) of FIG. 17 show a case where CD having a low numerical aperture and SD having a high numerical aperture are applied to an iris type shutter, respectively.

18 is a circuit diagram showing a changed state of the numerical aperture adjusting means when the iris type shutter is used instead of the liquid crystal shutter in the entire circuit system of the optical pickup apparatus applied to an embodiment of the present invention.

19 is a flow chart of the numerical aperture adjusting means shown in FIG.

20 is a diagram showing the outline of an optical pickup apparatus according to a second embodiment of the present invention.

21 is a perspective view showing a pickup base to be applied to the second embodiment of the present invention.

FIG. 22 is an exploded view showing the aperture means to be applied to the pickup base of FIG. 21;

FIG. 23 is a perspective view showing a carrier which is simultaneously moved by fixing a pickup base. FIG.

24 is a view showing an opening adjusting means configured in the pickup of the laser coupler method according to the third embodiment.

25 is a configuration diagram of the LD / PD used in the laser coupler pickup device.

Fig. 26 is a circuit diagram showing a focus error and tracking error signal detection circuit used in an optical pickup device of a laser coupler method.

* Explanation of symbols for main parts of the drawings

1, 21, 41: light source 3, 23, 43: beam splitter

8, 28, 48: photodetector 25: objective lens

30: numerical aperture adjusting means 470: actuator

44: liquid crystal shutter 100, 200: pickup base

160: iris shutter 210: aperture means

400: numerical aperture control means drive device 500: playback signal control means

550: disc discrimination means 600: tracking control device

650: focus control device 700: motor control device

750: digital signal processing apparatus 800: microcomputer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device and a control method thereof. In particular, the present invention relates to recording compatible discs having different thicknesses, which can read various types of discs by resolving the problem of spherical aberration caused by the disc thickness difference. And a reproduction device and an optical pickup device.

In general, a DVD (Digital Video Disk) employs a red semiconductor laser and an objective lens having a large aperture ratio (NA). Such a DVD has a recording capacity of 6-8 times that of a CD, uses video and audio data compression, and can record a movie having a quality of the same quality as a current TV broadcast on a disc having a diameter of 120 mm.

In order to read the signal recorded on the DVD, a red semiconductor laser beam having a wavelength of 635 nm or 650 nm is used.

On the other hand, when the wavelength of the laser emitted from the light source is shortened, both the track pitch and the shortest recording mark length can be reduced so that the spot diameter of the laser beam becomes smaller in proportion to the excitation. In general, the area of the recording mark can be reduced in proportion to the square of the wavelength.

On the other hand, the spot diameter of the laser beam is proportional to the wavelength of the light source and inversely proportional to the numerical aperture NA of the objective lens. Therefore, the recording density can be increased by increasing the numerical aperture NA without changing the wavelength. Therefore, the numerical aperture NA is about 0.45 in the optical system for CD, but can be increased to 0.6 in the optical system for DVD.

The following three methods are widely known as a method of protecting data reading in a conventional DVD.

First) simply increasing the numerical aperture (NA) by a relatively small amount.

Secondly, a method of employing a tilt angle correction mechanism called Tilt Servo for optical pickup instead of making the numerical aperture NA larger than 0.52.

Third) increasing the numerical aperture NA to 0.6 and shortening the distance that the laser beam penetrates the substrate of the disk.

Now, a configuration of an optical pickup apparatus generally used will now be described.

The conventional optical pickup apparatus as shown in FIG. 1 has a light source 1 and a diffraction which makes a beam from the light source 1 into a main beam and two sub beams for tracking servo. Grating 2 and beam splitter 3 and collimator lens 4 and the light source, which make the beams passing through the diffraction grating 2 into parallel beams. An object lens 5 for condensing the beam emitted from (1) on the optical disk 6, and a sensor lens 7 for condensing the reflected and transmitted beam again after condensing on the optical disk 6; And an optical detector 8 that receives the beam focused through the sensor lens 7 and detects a data signal recorded on the disk.

Referring to the operation of the conventional optical pickup device configured as described above are as follows.

Beams emitted from the light source 1 are converted into parallel light by a collimating lens 4 via a beam splitter 3, and then collected by an objective lens 5 to collect the optical disk 6. Reflected or diffracted on the information recording surface. The beam thus reflected returns to the same path and reaches the photo detector 8 to be transformed into an electrical signal. That is, the reflected beam is projected by the beam splitter 3 onto the photodetector 8 via the sensor lens 7 along an another course.

On the other hand, the diffraction grating 2 and the sensor lens 7 are generally widely used for tracking by a three-beam method and focusing servo by an astigmatism method.

The DVD can be reproduced only by an objective lens having a recording density higher by four times or more than a conventional CD so that the numerical aperture NA of the objective lens 5 has a high value of about 0.6. In this case, the aberration caused by the inclination of the disk increases as the thickness of the disk substrate becomes thick. In order to prevent this, the DVD standard generally adopts a disk substrate thickness of 0.6 mm.

At this time, a DVD having a thickness of 0.6 mm and a CD having a thickness of 1.2 mm are composed and reproduced by an optical system as shown in FIG. However, the optical system has the following problems.

For example, the beam intensity distribution is as shown by the solid line in FIG. 2 in the state where the disk surface is focused with the objective lens 5 having a numerical aperture (NA) = 0.6 on a 0.6 mm thick disk by adopting an optimal design. When the beam is focused on the 1.2 mm thick disk through the objective lens 5, the beam intensity distribution becomes as shown by the dotted line in FIG. 2 due to the spherical aberration of the objective lens.

That is, not only the beam intensity ratio of the main lobe is significantly reduced, but also the beam intensities of the side lobes are relatively increased to increase crosstalk from signals recorded in adjacent tracks. .

In addition, when the 1.2 mm disc is read by the objective lens having NA = 0.6, the sensitivity to the disc tilt is so large that the 1.2 mm disc can be reproduced by the optical pickup apparatus as shown in FIG. There is no problem.

Accordingly, an object of the present invention is to provide an optical pickup apparatus capable of reading DVD regardless of the type of disc as well as playing a DVD by adjusting the effective opening number of the objective lens by using the numerical aperture adjusting means.

It is another object of the present invention to solve the problem of spherical aberration which may occur when reading discs having different thicknesses with one pickup device, and to provide an optical pickup device capable of reproducing regardless of CD or DVD.

An apparatus for recording / reproducing two or more kinds of discs having different thicknesses for achieving the object of the present invention, comprising: a light source; A beam splitter for transmitting or separating the light beam from the light source; An objective lens for condensing the beam passing through the beam splitter on a disk mounted among disks having different thicknesses and recording densities; Numerical aperture adjusting means arranged between the light source and the objective lens to adjust the numerical aperture of the objective lens to have an effective aperture of 0.27 to 0.56 so as to focus on the mounted disk; A compatible recording / reproducing apparatus for a disc having a different thickness is provided, including a signal reproducing unit for reproducing information from the light beam reflected from the disc.

Further, in order to achieve the object of the present invention, an apparatus for recording / reproducing two or more kinds of thicknesses, the optical system comprising: a light source; A beam splitter for transmitting or reflecting a light beam from the light source; An objective lens for condensing the light beam passing through the beam splitter on a disk mounted among disks having different thicknesses and recording densities; Numerical aperture adjusting means disposed between the light source and the objective lens and adjusting an effective numerical aperture of the objective lens so as to focus on the mounted disk; A disc discrimination unit having a signal reproducing unit for reproducing information from the light beam reflected from the disc, and determining a type of disc in accordance with a signal output from the signal reproducing unit to a circuit system; A microcomputer which receives a discriminant result of the disc discriminator and controls a system; A numerical aperture adjusting means control unit which receives the output of the signal reproducing unit and controls the numerical aperture adjusting means according to the control of the microcomputer; There is provided a compatible recording / reproducing apparatus for a disc having a different thickness, comprising a motor controller for controlling the rotational speed of the motor according to the type of the disc.

In addition, the optical pickup mechanism for adjusting the numerical aperture by installing a numerical aperture adjusting means in the pickup base provided on a predetermined portion on the deck to achieve the object of the present invention, the pickup transport motor provided on one side of the deck; A plurality of gears sequentially connected to the gear to be inserted into the shaft of the pickup transport motor; A rack gear connected to the gear and fixed to a carrier; A pickup base for mounting components constituting the optical system; A carrier which simultaneously moves by seating the pickup base; An optical pickup apparatus comprising an iris type shutter provided at a predetermined portion of the pickup base is provided.

Further, in order to achieve the object of the present invention, an optical pickup mechanism for adjusting the numerical aperture by installing a numerical aperture adjusting means in a pickup base provided at a predetermined portion on the deck, the pickup base for mounting the components constituting the optical system; A motor installed at the rear of the pickup base; A plurality of gears sequentially connected to the helical gear to be inserted into the shaft of the motor; An aperture means connected to the gear and fitted into a shutter insertion hole of a pickup base; There is provided an optical pickup mechanism comprising a carrier which is simultaneously moved by seating the pickup base.

In addition, in order to achieve the object of the present invention, a single optical pickup device composed of an optical system and an instrument system, the optical system comprising: a light source and a photodetector assembly in which a light source and a light detector are integrally formed; A prism that forms and transmits light from the light source of the light source and the photodetector assembly; An objective lens for condensing the light transmitted through the prism on any one of disks having different recording densities and thicknesses; It is provided on the optical path on the objective lens and the prism, and is composed of numerical aperture adjusting means for adjusting the numerical aperture of the objective lens in accordance with the shape of the disk, the mechanical system is installed integrally with the optical system and moved There is provided an optical pickup apparatus, which is composed of possible movers.

First, before explaining the embodiments of the present invention will be described with respect to the basic principles of the present invention.

An optical system having a performance close to that of an anhydrous meter used in an optical pickup apparatus or an optical pickup system according to the present invention will be described below.

The spot size formed by the optical system can be estimated by the following approximation by diffraction of the light beam.

In Equation (1), K is a constant determined by light intensity distribution characteristics (for example, Plain Wave, Gaussian Beam, Truncated Beam, etc.) in the bundle, λ is the wavelength of the light source used, NA ( Numerical Aperture) is a predetermined numerical aperture.

According to Equation (1), when N.A becomes large, the spot size becomes small, and when N.A becomes smaller, the spot size becomes large. For example, in the case of a high-density disc having a thickness of 0.6 mm, a small spot size is required because the distance between tracks and the size of the pit is small, so that an objective lens with a large numerical aperture is required. However, in the case of a low density disc having a thickness of 1.2 mm, the distance between the tracks and the pit is larger than the track interval and the size of the pit of the disc having a thickness of 0.6 mm. It is possible to use an objective lens with a smaller numerical aperture than when reading.

The relationship between the numerical aperture and the size of the incident ray bundle incident on the objective lens is as follows.

Where D is the diameter of the incident ray bundle and f is the focal length of the objective lens.

That is, in Equation (2), when the magnitude of the incident light beams to the objective lens having the same focal length is controlled, the effective aperture number of the objective lens can be changed.

On the other hand, an objective lens having a numerical aperture of 0.6 is an optical system configured to read a disk with a high recording density having a thickness of 0.6 mm, and has the following problems when reading an existing disk having a thickness of 1.2 mm without changing the numerical aperture. .

1) If focus compensation is not performed, there is a problem that focusing is not possible due to burring due to defocus,

2) As the spherical aberration occurs due to the change of the thickness of the disk, the distribution of light in the first side robe increases due to the decrease in the center intensity distribution, and the crosstalk There is a problem that the S / N ratio is reduced by the increase,

2) There is a problem that the system stability deteriorates due to the occurrence of Comma aberration and astigmatism on the inclination of the disk.

Therefore, when the low density disc is read by the optical pickup apparatus optimally designed for the high density disc, the optical performance deteriorates and the information recorded on the disc cannot be read.

On the other hand, the amount of spherical aberration caused by the change in disk thickness is as follows.

Where n is the refractive index of the disk, Δd is the thickness variation, and NA is the numerical aperture. In addition, when the amount of aberration generated by defocus is ΔZ as the amount of defocus, Equation (3) can be expressed as follows.

When reading a 1.2mm disc with an objective NA = 0.6 and changing the effective aperture NA = 0.3 of the same objective with the numerical aperture adjusting means, the focus is shifted to the information recording surface of a 1.2mm disc and defocused. After eliminating the influence on), the amount of aberration generated when reading the same disk and its central intensity distribution can be expressed as shown in the following table.

At this time, the total-root-mean-square wavefront aberration, which can be expressed as an approximate aberration in the relationship between wave aberration and central intensity distribution, is less than 0.07λ (center intensity distribution 80%). According to marechal's critertion, the refractive index of the disk is 1.55, and the center intensity distribution of the objective lens used for the disk having the wavelength of 0.635nm and 0.6mm is 100%.

In the above table, if the effective number of the objective lens is changed and the focus is moved to the information recording surface of the 1.2 mm disc to remove the influence on the defocus, the information can be sufficiently approximated to the aberration meter so that the information can be read.

In addition, if the effective numerical aperture NA of the objective lens is changed by using the numerical aperture adjusting means in this way, the following equation can be obtained.

Numerical example of the amount of aberration generated by the tilt of the disk when the refractive index n of the disk is set to 1.55, the thickness of the disk is 1.2 mm, the tilt of the disk is 0.6 ° and the wavelength of use is 635 nm based on the above formula (5). Is as follows.

However, as shown in Equation (1) above, decreasing the effective numerical aperture NA increases the beam spot size for diffraction. Therefore, when the beam spot size exceeds a certain value determined by the disc specification, crosstalk is generated by increasing the spot size rather than crosstalk due to a change in intensity distribution due to aberrations. There is a problem that the ratio is bad. Therefore, there is a change range of the effective numerical aperture, and the upper limit of the effective numerical aperture is restricted by the change condition of the intensity distribution due to the generated aberration as described above, and the lower limit is restricted by the increase of the spot size.

In the case of an optical system using an objective lens having a numerical aperture NA = 0.6 for a 0.6 mm disk used as the numerical example as a range satisfying the above constraints, an effective opening available for reading an existing CD of 1.2 mm under the above conditions. The range of numbers can be expressed as:

The range of the effective number of openings will be described later. Please refer to the ninth (a) and (b). (A) of FIG. 9 is a graph showing the change of the crosstalk according to the change of the numerical aperture of the objective lens, and (b) of FIG. 9 is a graph showing the change of the reproduction signal according to the change of the numerical aperture of the objective lens.

In the optical pickup apparatus having a large numerical aperture and a small thickness and reading information of a high density recording disk by the above principle, a method for giving backward compatibility to a case of reading a disk having a thick thickness and a low recording density is provided. The inventors have recognized that the numerical aperture adjusting means can be constituted by an operation of changing the effective opening number of the objective lens within the range of equation (6) and moving the focus to the information recording surface.

The configuration and operation of each embodiment of the optical pickup device of the present invention based on the basic principles as described above are as follows.

Hereinafter, a first embodiment of the present invention will be described in detail with reference to the accompanying drawings.

3 is a diagram showing an outline of an optical pick-up system according to an embodiment of the present invention.

The optical pickup system of the present invention is largely divided into an optical system A and a circuit system B, as indicated by dashed lines in FIG. 3.

First, as shown in FIG. 3, the optical system A according to the exemplary embodiment of the present invention includes a diffraction grating 24 and a beam splitter. It enters the objective lens 25 via the beam splitter 23. The effective numerical aperture of the objective lens 25 is changed between the objective lens 25 and the beam splitter 23 by adjusting the transmission beam diameter of the beam to enter the objective lens 25. The numerical aperture adjusting means 30 is installed. Although the numerical aperture control means 30 is shown to be able to move in the same manner by connecting to the actuator movable portion 26, between the objective lens 25 and the light source 21 or the objective lens 25 or the light source 21 It may be used as a component (not shown) integrally configured to each of the components.

Meanwhile, the ray bundle passing through the numerical aperture adjusting means 30 is focused on the disk 10 through the objective lens 23. The reflected beams from the disk 10 pass through the same course of the objective lens 25 and the beam splitter 23 for reading signals from the information recording surface of the disk 10. do. Further, the optical signal modulated by the signal on the disk information recording surface reaches the photo detector 28 via the sensor lens 27. The photodetector 28 serves to convert the modulated optical signal into an electrical signal by a photoelectric effect.

The electrical signal output from the photodetector 28 is input to the microcomputer 800 via the reproduction signal processing means 500 and the disc discrimination means 550 which will be described later in detail. At this time, the reproduction signal processing means 500 transmits the tracking control and focus reproduction signals to the tracking control device 600 and the focus control device 650, respectively, in accordance with the signal input from the photodetector 28. In the reproduction signal processing means 500, the high frequency signal (RF or HF) is directly connected to the disc discrimination means 550 or the digital signal processing apparatus 750.

The microcomputer 800 drives the numerical aperture adjusting means 30 for adjusting the numerical aperture suitable for each disk (ie, disks of different sizes and thicknesses) according to the signal output from the disk discriminating means 550. Different thicknesses of the numerical aperture control means driving device 400 and the focus servo circuit 650 having a focus control function while simultaneously adjusting the initial focus position of the objective lens 25 are provided. It provides a signal that conforms to the disk 10. In addition, the microcomputer 800 is connected to a motor controller 700 that is responsible for the control of a spindle motor (not shown) according to each disk 10. The motor controller 700 is connected to the digital signal processor 750.

On the other hand, the objective lens 25 is configured to be movable in accordance with the movement of the actuator movable portion having the actuator movable coils 26a and 26b and the yoke 26.

In FIG. 3, 10a shows an information recording surface of a DVD disc having a thickness of 0.6 mm, and 10b shows an information recording surface of a CD having a thickness of 1.2 mm.

Now, the case of using the liquid crystal shutter as an example of the numerical aperture adjusting means 30 in the optical system A configured as described above is as follows.

4 is a perspective view schematically showing an actuator provided with a liquid crystal shutter which is one of the numerical aperture adjusting means.

As shown in FIG. 4, the actuator 40 includes a tracking coil 26a and a focus coil 26b wound around the outer side of the mover 25a that accommodates the objective lens 25, and the mover 25a. And a yoke 26 in which the tracking coil 26a and the focus coil 26b are insertable, and an actuator base 29 on which the yoke 26 is seated. In addition, protrusions 34 are formed at both sides of the mover 25a so that the rear plate 32b installed at the rear side through the protrusions 32 and the opening 32a of the support frame 32 is connected to the wire 35. Connected. A hole 29a is formed in the center of the actuator base 29.

On the other hand, the lower portion of the mover (25a) is provided with a liquid crystal shutter 44 made of a combination of a plurality of plates which will be described later in detail with the objective lens 25.

The above-described numerical aperture control means 30 will be described with reference to the liquid crystal shutter which is one of the specific examples.

5 is an exploded perspective view of the liquid crystal shutter. As shown in FIG. 5, the liquid crystal shutter 44 has the size and shape of the light bundle to adjust the transparent electrodes 67a, 67b and 69 to the two plate-shaped transparent substrates 66 and 70, respectively. Is used as formed in (a) and (b) of FIG.

A gap d is determined between the transparent electrodes 67a, 67b and 69 provided on the transparent substrates 66 and 70 by the following conditions. And the refractive index of ordinary beams is No. 1 with respect to wavelength (lambda). When the difference between two refractive indices is δn in a liquid crystal having an index of refraction of an extraordinary beam of Ne, an arbitrary m order minimum condition is expressed as follows.

TN liquid crystal is injected into the TN liquid crystal layer 68 formed between the intervals determined by the above equation, and the polarizing plate 71 or 74 formed on the exit side transparent substrate 70 in the direction perpendicular to or equal to the polarization direction of the emitted light. ) To be bonded or installed by an instrument (not shown).

(A) of FIG. 5 is an exploded perspective view of the liquid crystal shutter 44 to which the polarizing plate 71 with the polarization pattern is horizontally applied, and (b) is the liquid crystal shutter 44 with the polarizing plate 71 with the polarization pattern formed vertically. The exploded perspective view of each is shown.

As shown in (a) and (b) of FIG. 5, the light bundle 72 that is incident on the incident-side transparent substrate 66 and linearly polarized passes through the transparent electrodes 67a and 67b, and then the TN liquid crystal layer. Pass (68). At this time, when the liquid crystal of the TN liquid crystal layer 68 is arranged to have 90 ° photoluminescence in a state in which no voltage is applied and the interval d represented by the above equation is adjusted, the incident polarization direction is 90 in the arrow direction indicated by 73. ° turn. (See Figure 6 (d).)

In addition, when the PDLC liquid crystal is injected into the liquid crystal layer 68, unlike the TN liquid crystal, a change in the polarization direction of incident light passing through the liquid crystal layer does not appear on the emission side due to the characteristics of the PDLC. When using this property, in order to shield incident light according to the change in polarization direction in the TN liquid crystal, a separate polarizing plate should be attached and used, but the PDLC liquid crystal does not need this configuration. Thus, as shown in FIGS. 6A, 6B, and 6F, the transparent electrodes 67a, 67b, and 67c (a, b, and 6) of the liquid crystal layer 68 are shown. (f) (g) to 67b are not shown], and the PDLC liquid crystal is injected into the liquid crystal layer. As the voltage is turned on and off to the transparent electrode, incident light incident on the liquid crystal layer of the portion where no voltage is applied is scattered and is not transmitted to the exit side, and incident light incident on the liquid crystal layer of the portion where the voltage is applied is transmitted to the exit side. do.

FIG. 6A is a diagram showing a voltage applied to the transparent electrodes 67a, 67b and 69 of the liquid crystal shutter 44 in the NW (Normal White) mode, and FIG. When voltage is applied to the transparent electrodes 67a, 67b and 69 of (15), it is a figure which shows the change of the polarization direction in TN liquid crystal.

When the TN liquid crystal layer 68 shown in FIG. 6A is divided into 68a and 68c, respectively, and voltage is applied to the transparent electrodes 67a and 67b connected to the reference numerals 68a and 68c, the photorefractive property disappears. Since the incident polarization direction is maintained, the light beam is blocked by the polarizing plate 71 or 74 attached perpendicular to the incident polarization direction. However, since no voltage is applied to the transparent electrode 67c, the polarization direction is rotated by 90 ° so that the transparent electrode 67c passes through the polarizing plate 71 or 74 like an inclined arrow.

In more detail, the liquid crystal shutter 44 configured as described above is installed in the same direction as the polarization direction rotated in a voltageless state in installing the polarizing plate 71 or 74 on the TN liquid crystal layer 68. When the incident light is transmitted through the liquid crystal shutter 44 in a no-voltage state, if the voltage having the AC component adjusted as described above is applied from the waveform generator 144 (see FIG. Therefore, it is darkened by being blocked by the polarizing plate 71 or 74 on the emission side. In this case, the polarization direction of the finally emitted light bundle is rotated by 90 ° with respect to the polarization direction of the first incident light bundle, and is emitted by rotating by 90 °. This mode is converted into a positive mode or a normal white mode. Mode).

6B is a diagram showing a state in which voltage is applied to the transparent electrodes 67a, 67b, and 69 of the liquid crystal shutter 44 in the NB (Normal Block) mode. d) shows the change in the polarization direction in the TN liquid crystal without a voltage applied thereto.

As shown in FIG. 6B, when voltage is applied to the other transparent electrodes 67c without applying a voltage to the transparent electrodes 67a and 67b, the switches SW10 and SW20 must be controlled separately. . In other words, the transparent electrodes 67a and 67b simultaneously control the voltage on and off, while the other transparent electrodes 67c must perform the on-off control separately.

In detail, when the polarizing plate 71 is vertically attached to the polarization direction of the emitted light passing through the TN liquid crystal layer 68 to which no voltage is applied (reference is made from the waveform generator 144 to the transparent electrode 67a, 67b), when no voltage is applied, the same as in (d) of FIG. 6). In other words, as shown in (b) of FIG. 5, the polarizing plate 74 is attached in the same direction as the polarization direction of incident light. In this case, since the light emitted from the TN liquid crystal layer 68 is rotated by 90 ° according to the above conditions, the light is blocked by the polarizing plate 74 and darkened. Thus, the mode of the liquid crystal plate 68 in which the polarizing plate 74 is installed is called negative mode or normal black mode.

In the TN liquid crystal panel 68 having such characteristics, applying a voltage having an alternating current component such that frequency, waveform, duty, and bias to the liquid crystal shutter 44 is suitable for driving the liquid crystal shutter 44, the optical liquidity of the liquid crystal disappears. Since it has the same polarization component as the deflection direction of the incident light during the passage, the beam is emitted through the polarizing plate 71 or 74 which is bonded or bonded to the exit-side transparent substrate 70 by an object. Using the TN liquid crystal layer 68 having such a configuration, it can be seen that the polarization direction of the final transmission window can be the same as the initial incident polarization direction.

On the other hand, Fig. 6 (f) (g) shows an operation state when the PDLC liquid crystal layer 68 'is used as the liquid crystal layer 68. Figs.

When no voltage is applied to the transparent electrodes 67a and 67b as shown in FIG. 6 (f), the voltage is always applied to the transparent electrodes 67c, and the transparent electrodes 67a and 67b are simultaneously turned on. The switch (SW10, SW20) should be controlled to control / OFF.

In detail, the light incident on the PDLC liquid crystal layer 68'a of the portions of the electrodes 67a and 67b to which no voltage is applied is scattered, and thus is blocked from passing to the exit side. On the other hand, the light incident to the PDLC liquid crystal layer 68'c portion of the transparent electrode 67c portion to which the voltage is applied passes through to the exit side without being scattered.

At this time, the ratio of the amount of light passing through the liquid crystal layer and the amount of light passing around the scattered light satisfies Formula (I) described later.

On the contrary, when voltage is also applied to the transparent electrodes 67a and 67b to increase NA, as shown in (g) of FIG. 6, all incident light passes through the exit side.

In addition, the same effect as described above may be obtained by controlling the same driving circuit using the ECD (Electro Chromic Display) device instead of the liquid crystal layer.

The operation in this case is the same as the case of using the liquid crystal shutter liquid crystal layer described above, so a detailed description of the operation is omitted.

On the other hand, when reading a high-density disc, an objective lens having a large numerical aperture (NA) is required. Therefore, when the numerical aperture (NA) of the objective lens is large, the size of the formed beam is enlarged toward the polarization direction according to diffraction theory. In addition, when the objective lens made of a plastic resin is used, the astigmatism caused by the birefringence of the material appears in the polarization direction. Therefore, in the case of the optical pickup, the polarization direction needs to be aligned in the tangential direction of the track formed on the disk, so that the noise generated between adjacent tracks can be reduced to increase the S / N ratio. It is possible to select and use the mode according to the needs of the system.

In addition, in the liquid crystal shutter 44 having the TN liquid crystal layer 68, an error in polarization rotation angle due to a gap error between the transparent substrates 66 and 70, and the liquid crystal shutter 44 in the initial incident polarization direction The leakage of light may occur in the light blocking region of the two modes shown in the above example due to an error and an installation error of the polarizing plate 71 installed in the TN liquid crystal layer 68. In the case of such light leakage, the performance of the optical pickup is changed. Will occur. In addition, when PDLC (Polymer Dispersion Liquid Crystal) is injected, the scattered light is incident at the part where no voltage is applied, and thus the performance change occurs when compared with the complete blocking. Such a change in performance is defined as the intensity of the permeation of the transmissive portion A of the liquid crystal layer 68 as 1, as shown in FIG. 8B, and the transmittance of the transmissive portion A is It, the blocking portion or the scattering portion. If the transmission intensity of (B) is called Is, the contrast ratio is expressed as

(A) of FIG. 8 shows the change of the amount of jitter due to the peripheral pits to the contrast ratio, and (c) of FIG. 9 shows the change of the crosstalk with respect to the contrast ratio. (d) shows the relationship between the reproduction gain and the contrast ratio.

According to the above equation, the usable area for the breakthrough penetration ratio can be expressed as follows.

Since the light beams passing through the liquid crystal shutter 44 having the above-mentioned operation are incident on the objective lens 25 with different incidence diameters depending on whether the liquid crystal shutter 44 is driven or not, the effective numerical aperture NA ) Is changed and the objective lens 25 focuses the bundle of rays to form an optical spot on the information recording surface of the disk 10.

In forming the optical spot on the information recording surface of the disk 10, the position of the focus is determined by discrimining the disk 10. Therefore, the actuator 40 and the disk including the liquid crystal shutter 44 and the objective lens 25 are required. In relation to (10), the distance L1 between the recording surface of the disk having a thickness of 0.6 mm and the objective lens 25 set to an initial position with respect to the disk when the side of the objective lens 25 in the disk 10 is referred to as the reference surface. Is closer than the distance L2 between the information recording surface of the disk having a thickness of 1.2 mm and the objective lens 25, the actuator including the objective lens 25 and the aperture adjusting means (i.e., the liquid crystal shutter 44) is movable. When the yoke 26, the tracking coil 26a, and the focusing coil 26b swing up and down from the initial position at the time of play, a position where RF is generated occurs in a disc having a thickness of 0.6 mm first. Afterwards the RF on the disk with a thickness of 1.2 mm Will appear.

The voltage applied to the focus coil 26b included in the actuator 40 is high when the amount of movement is high, so the voltage applied to the focus coil 26b at a position where RF is generated in a disk having a thickness of 0.6 mm. Vs. When the voltage applied to the focus coil 26b at the position where RF is generated in the disk having a thickness of 1.2 mm is Vc, the initial values according to different disks are set by setting Vc and Vs to OFFSET voltage values in the focus control device 650. The focus position can be controlled.

10 is a circuit diagram showing a circuit system B of an optical pickup apparatus applied to an embodiment of the present invention.

As shown in FIG. 10, when the play key (not shown) is pressed, the microcomputer 800 outputs a control signal of the switch SW1 so that Rc is the CD when the offset resistance of the amplifier Amp2 is CD. If it is SD, then Rs.

By this operation, DC-Offset is applied to the focus coil 26b in the focus control device 650, and the actuator 40 is moved to the disk 10 side.

After the actuator 40 is moved, the microcomputer 800 turns on the switch SW2 connected to the oscillation circuit 30a of the drive unit 400 of the numerical aperture adjusting means 30 to turn on the liquid crystal shutter 44. ) To lower the effective number NA. That is, the periphery of the liquid crystal shutter 44 becomes dark.

After lowering the effective number of openings as described above, when the microcomputer 800 recognizes the disk 10, the microcomputer 800 turns on the switch SW3 of the motor control apparatus 700 and changes the path of the variable resistor PL. The spindle motor 710 is rotated at a low speed. The spindle motor 710 is connected to a power amplifier 715, and the power amplifier 715 is connected to a motor control circuit 720.

On the other hand, the microcomputer 800 again turns on the switch SW4 of the focus control device 650, and applies the triangular wave generated by the oscillator 655 to the actuator 40 to apply the actuator ( 40) will swing. Here, the switch SW6 is turned off when the switch SW4 is ON, and the switch SW6 is turned on when the switch SW4 is OFF.

By the operation of the switch SW1, the switch SW5 of the reproduction signal processing means 500 is operated. In the reproduction signal processing means 500, in the case of CD, the gains G1 ', G2', and G3 'for outputting are adjusted, and in the case of SD, gains G1', G2 'and G3' for outputting. Will be adjusted.

Looking at the reproduction signal processing means 500 in detail as follows.

Fig. 11A shows the internal structure of the photodetector, and Fig. 11B shows a detailed circuit diagram of the reproduction signal processing means.

As shown in Fig. 11A, three segments 28a, 28b and 28c are formed inside the photodetector 28, and the segments 28a formed in the center are divided into four. The beams incident on the segments 28a, 28b and 28c are converted into electrical signals by the photoelectric effect, as shown in FIG. 11 (b). That is, the electrical signals a, b, c, d, e, and f are RF signals and focus errors through the RF signal calculator 555, the focus error calculator 560, and the tracking error calculator 565, respectively. The disk is discriminated by the logic of the disk discriminating means 550 calculated by the signal and the tracking error signal.

Analog switch array 570 (i.e., switch SW5 in FIG. 10) of reproduction signal processing means 500 which receives this signal by an operation signal applied from photodetector 27 to reproduction signal processing means 500 At the OP-Amp (Operational Amplifier) (not shown) output with gain G (corresponding to G1, G2, G3 in Figure 1 (b)) when switching the path to read a dense DVD disc. When output signals of the CD-based low density disc are read, output signals at the OP-AMP output terminal having gains G '(G1', G2 ', G3') are applied. At this time, the following relationship is established between the gains G and G '.

Each signal output from the OP-AMP is converted into an RF signal, a focus error signal, and a tracking error signal through an RF signal calculator 555, a focus error calculator 560, and a tracking error calculator 565, respectively. The signal processor 750, the focus controller 650, and the tracking controller 600 are transferred to the signal processor 750 and used to control the signal.

12 is a schematic flowchart of the disc discriminating means.

In forming an optical spot on the information recording surface (not shown) of the disk 10, since the position of the focus is determined by discriminating the disk 10, as shown in FIG. 12, the microcomputer 800 The actuator 40 is moved toward the disk 10, the numerical aperture is reduced by driving the liquid crystal shutter 44, and the spindle motor 710 of the motor controller 700 is rotated at a constant speed.

Under the above conditions, the actuator 40 is swinged to determine whether RF is generated. In this case, it can be classified into a case where an RF signal is generated (that is, a disk having a thickness of 1.2 mm) and a case where an RF signal is not generated (that is, a disk having a thickness of 0.6 mm).

1) When an RF signal is generated: The spindle motor 710 is controlled by CLV (Constant Linear Velocity), and the reference speed is controlled by the motor control circuit 720. Thereafter, the predetermined focus control and tracking control signals are transmitted to the focus control apparatus 650 and the tracking control apparatus 600 via the reproduction signal processing means 500. Under this condition, the pickup will read the signal.

2) When no RF signal is generated: The actuator 40 is returned to its original position, and the effective number of openings is increased by stopping the driving of the liquid crystal shutter 44. Then, the actuator 40 is swinged again. Then, it is again determined whether the RF signal is generated. In this case, when no RF signal is generated, the disk is in error or there is no disk. When the RF signal is generated, the spindle motor 710 is controlled by CLV and the reference rotation is performed by the motor control circuit 720. To control the number. After that, the gain is adjusted to perform the focus control and the track control to read the signal.

A case where the RF signal is generated and a case where it is not generated will be described in detail with reference to FIG. 10 as follows.

If the microcomputer 800 controls the switch SW1 so that the OFFSET resistance becomes Rc, the initial position of the actuator 40 is set, and the high frequency RF is generated during the swing of the actuator 40 to discriminate the disk. When a voltage is applied to the comparator C1 through a DC detection circuit consisting of R1, D1, C1, C2 in the means 550, and the signal is higher than the reference voltage set by the resistors Rt, R2, the high frequency RF is effective. It is recognized that the error occurred more than the value of the microcomputer to recognize that the disk is a CD.

When the disc is recognized by the above operation, the microcomputer 800 drives the focus control device 650, the tracking control device 600, the motor control device 700, the numerical aperture control means 30, and the numerical aperture control means. The switches SW1, SW2, SW5 in the apparatus 400 and the reproduction signal control means 500 are fixed as they are, the switch SW4 is turned off, and the switch SW3 is switched to control the motor control circuit 720. A signal is applied, and a focus error signal FES output from the reproduction signal processing means 500 is applied to the focus control device 650 with the switch SW6 turned on, and a tracking error signal (TES) is added to the tracking control device 600 to achieve focusing and tracking. In addition, when the switch SW3 is switched in the motor controller 700, the motor control signal output from the digital signal processor 750 is applied to the motor controller 700 to perform the CLV control.

However, if a high frequency (RF) is not generated during the swing of the actuator 40, the microcomputer 800 controls the switch SW1 and controls the offset resistance to be Rs so that the position of the actuator 40 is changed. Is recovered and the switch SW2 is turned off to release the drive of the liquid crystal shutter 44 to increase the effective numerical aperture. Then, the switch SW4 is turned ON to apply the triangular wave generated by the oscillation device 655 to the actuator 40 again to swing the actuator 40.

By the above operation, a control signal is given to select a path having a gain corresponding to the high density disk.

As described above, when RF is generated during the swing, the disc recognition signal is sent to the microcomputer 800 by the comparator C1, and the microcomputer 800 fixes the switches SW1, SW2, and SW5. The motor control circuit 720 is controlled to perform CLV control by a sink signal, the switch SW3 is switched, and the FES signal is turned on by the switch SW6 ON. The TES signal is applied to the tracking control device 600 to perform focusing and tracking control.

However, if RF is not generated by the above-described operation, a disk error or disk is not present. Therefore, an error signal is output and the operation ends.

Now, the case of using the iris type shutter instead of the liquid crystal shutter 44 as the numerical aperture adjusting means 30 is as follows.

13 is a schematic plan view of an optical pickup apparatus according to an embodiment of the present invention.

As shown in FIG. 13, reference numeral 130 is a deck of a player. On one side of the deck 130, a pickup transport motor 132 for transporting the pickup is installed. The first gear 136 is formed on the upper end of the shaft 134 of the pickup transport motor 132. The second gear 138 is engaged with the first gear 136. A third gear 139 is formed on the second gear 138. The third gear 139 is engaged with the rack gear 140 to transfer the power of the motor 132 to the rack gear 140 fixed to the carrier 122.

The pickup base 100 is seated on the carrier 222, and the carrier 122 is supported by the shaft 124. And both sides of the pickup base 100 is formed with a shaft 110 protruding to the outside.

FIG. 14 is an enlarged perspective view of the pickup base shown in FIG.

As shown in FIG. 14, a space 105 is formed at the center of the pickup base 100. In the center of the space portion 105, a stair-shaped seating portion 108a is formed inward, and a beam splitter 23 is placed on the seating portion 108a.

On the left side of the beam splitter 23, a protrusion 115 for fixing the sensor lens 27 at a predetermined distance is formed. The sensor lens 27 is fitted to the cylindrical sensor lens holder 127a, and a hole 127b is formed in the lower portion of the sensor lens holder 127a to be detachably fitted to the protrusion. A through hole 107a is formed at a predetermined position on the sidewall 100a of the pickup base 100. The photodetector 28 is fitted into the through hole 107a to be fixed.

On the other hand, the shutter coupling hole 108 in the longitudinal direction is formed in the inner wall (100b) of the space portion 105.

15 is a perspective view showing a carrier to be connected to the pickup base.

As shown in FIG. 15, a carrier 122 is installed on the bottom surface of the pickup base 100, and the carrier 122 mounts and transports the pickup base 100. The carrier 122 is a U-shaped bent plate, the leaf spring 124 for inserting and fixing the shaft 110 of the pickup base 100 on the upper side of each side wall 122a of the carrier 122 ) Is installed. An upper portion of the sidewall 122a is formed in a stepped shape, and a screw hole 128 is formed in a surface 123 having a low level. In addition, a screw through hole 124a is formed at a predetermined portion of the leaf spring 124 to correspond to the screw hole 128. In addition, the leaf spring 124 is fixed to the side wall 122a of the carrier 122 by a screw 126, wherein the step is fastened under a state in which the shaft 110 is fitted to the lower surface 123. In addition, a through hole 125a is formed at a predetermined portion in the central base 125 of the carrier 122. In the through hole 125a, a shutter base fixing part 174 (see FIG. 16), which will be described later, is installed in an upright position and fixed by a screw 127.

Now, with reference to the iris-type shutter to be fitted to the shutter coupling hole 108 shown in FIG.

16 is an exploded perspective view of the iris type shutter.

As shown in FIG. 16, the iris type shutter 160 includes first and second blades 162 and 164, a shutter base 166 on which the first and second blades 162 and 164 are installed, and the shutter base. It consists of a shutter cover 168 that is integrally fitted to the top of the (166). The shutter base 162 includes a pair of long holes 170 and a hole 172. In addition, a plurality of small holes 173 are formed at regular intervals between the pair of long holes 170.

The first and second blades 162 and 164 are formed with guide holes 162a and 164a and holes 162b and 164b, respectively. In addition, the first blade 162 has a hat-shaped space 162c having one surface open at one side thereof, and the second blade 164 has a hat-shaped space 164c formed therein.

On one side of the shutter base 166, a bent fixing part 174 for fixing to a predetermined carrier 122 (FIG. 15) is formed to protrude outward. Projections 175 for guiding the guide holes 162a and 164a of the first and second blades 162 and 164 are formed in upper and lower portions of the hole 172 of the shutter base 166. A pair of projections 166d are formed on the outer wall 166c of the shutter base 166, respectively. The projection 166d is inserted into the hole 168d of the fastening portion 168c of the shutter cover 168 which will be described later.

Meanwhile, the motor 180 is inserted below the shutter base 166. That is, the motor 180 is formed so that the motor shaft 182 protrudes in the center thereof, and a pair of support pillars 184 are fixed to both sides of the motor shaft 182 at regular intervals. The motor shaft 182 is fitted into the central hole 185a of the rotor 185. The rotor 185 has a pair of protruding support shafts 186 formed at both sides thereof. The support shaft 186 is first fitted into the long hole 170 formed in the shutter base 166, and then inserted into the holes 162b and 164b of the first and second blades 162 and 164, respectively. Therefore, since the first and second blades 162 and 164 may be moved left and right by the operation of the motor 180, the numerical aperture may be adjusted.

On the other hand, the shutter cover 168 is formed with a hole 169 and a pair of long holes 167 in a predetermined portion corresponding to the shutter base 166. A plurality of small holes 163 are formed at regular intervals between the long holes 167. In addition, a pair of fastening portions 168c are formed at both sides of the shutter cover 168 so as to be integrally coupled with the shutter base 166. The fastening part 168c has a rectangular hole 168d formed therein, respectively. The hole 168d is fitted into the projection 166d formed on the outer wall 166c of the shutter base 166.

(A) and (b) of FIG. 17 are top views respectively showing the case where the shutter is applied to the CD and the case where the shutter is applied to the DVD.

When the low numerical aperture NA is to be used, as shown in FIG. 17A, light as much as the area A may be used. When the high numerical aperture NA is to be used, As shown in (b) of FIG. 17, the light corresponding to the area B may be used.

1) For low numerical aperture (see Figure 17 (a)):

First, when the motor 180 is driven, the rotor 185 fitted to the motor shaft 182 is rotated. At this time, the support shafts 186 provided on both sides of the rotor 185 are movable left and right within the range of the long hole 170. In the case of a low numerical aperture, when the support shaft 186 fitted into the hole 162b of the first blade 162 is moved about 1/2 of the right along the long hole 170, the second blade 164 is also a hole ( The support shaft 186 fitted to the 164b is moved to the left by about 1/2 along the opposed long hole 170. Here, since the support shaft 186 is moved in the opposite direction as the rotor 185 moves, the above-described first and second blades 162 and 164 move opposite to each other in correspondence with the movement of the support shaft 186. .

2) For high numerical aperture (see Figure 17 (b)):

First, when the motor 180 is driven, the rotor 185 fitted to the motor shaft 182 is rotated. At this time, the support shafts 186 provided on both sides of the rotor 185 are movable left and right within the range of the long hole 170. In the case of a high numerical aperture, when the support shaft 186 fitted into the hole 162b of the first blade 162 is completely moved to the right along the long hole 170, the second blade 164 is also inserted into the hole 164b. The fitted support shaft 186 moves completely to the left along the opposed long hole 170. In this case, the first and second blades 162 and 164 move in opposite directions to correspond to the movement of the support shaft 186 as described above.

Although the shapes of the first and second blades 162, 164 are limited to the shape of wings as shown in FIG. 16 only in the above-described embodiment, the shapes of the first and second blades 162, 164 are not shown. It may be configured in various forms (for example, a circular fan which is sequentially folded in a camera aperture or a fan shape, etc.), and may be any one simply adjusting the amount of light according to the movement of the manufactured article.

18 is a diagram showing a circuit diagram of the optical pickup apparatus when the iris type shutter is applied as the numerical aperture adjusting means.

FIG. 18 illustrates only the numerical aperture adjusting means in the circuit diagram shown in FIG. 10, and thus only the numerical aperture adjusting means will be described. Therefore, please refer to the description of the above-described FIG. 19 is a flowchart illustrating a motor control method when an iris type shutter is used.

18 and 19, when the iris type shutter 160 is used as the numerical aperture adjusting means 30, when the positive voltage is applied to the motor control apparatus 700, the iris type shutter 160 is applied. ) Is opened and the iris type shutter 160 is closed when a reverse polarity voltage is applied. For reference, the current i0 flowing in the sensing resistor R10 is + i0 for forward rotation but -i0 for reverse rotation.

When the control signal of the microcomputer 800 sets the switch SW8 to high and the switch SW10 to low, the output of the differential amplifier Amp4 outputs a + V value, and the NPN transistor Q1 becomes conductive. A positive voltage is applied to the 330 to perform a forward rotation. At this time, the iris type shutter 160 is completely moved and opened. Thereafter, when the iris-type shutter 160 comes to a position where it cannot be moved by a restricting jaw (not shown), the motor 330 is overloaded and the current flowing in the motor 330 becomes larger than a normal value. At this time, if the high (=) voltage of the detection resistor (R10) is greater than the threshold voltage of the diode (D1), the diode (D1) conducts a current flows through the resistor (R8), the + of the differential amplifier (Amp5) A positive voltage is applied to the input terminal, so the output of the differential amplifier (Amp5) becomes high. Then, the microcomputer 800 recognizes this by the S signal, and completes the operation by setting the switch SW8 to low.

On the other hand, to open the iris shutter 160 (i.e., read CD), when the switch SW8 is set low and the switch Sw10 is set high, the output of the differential amplifier Amp4 becomes -V and the transistor ( Q2) becomes conductive, and the motor 330 reverses while the motor 330 receives a negative voltage. At this time, the microcomputer 800 checks the output voltage S of the differential amplifier Amp5, and if it is Low, the microcomputer 800 maintains the current state, and the iris-type shutter 160 is completely opened and the motor 330 is no longer rotated in reverse. If it becomes impossible, the motor 330 is overloaded, the resistor R10 is subjected to a high voltage of (-), and a current flows through the diode D2 so that a negative voltage is applied to the input terminal of the differential amplifier Amp5. I get caught.

Therefore, when the output is increased, the micro-on computer 800 detects this to stop the power supply to the motor 330 by setting the switch Sw8 to Low.

20 is a diagram illustrating an outline of the optical pickup system according to the second embodiment of the present invention.

The optical pickup system applied to the second embodiment of the present invention is composed of an optical system AA different from the optical system A of the first embodiment described above, and the circuit system B is the same. See one first embodiment.

In Fig. 20, 10a is an information recording surface of a DVD disk having a thickness of 0.6 mm, and 10b is an information recording surface of a CD having a thickness of 1.2 mm.

Then, the optical system AA will be described with reference to FIG. 20.

As shown in FIG. 20, the optical system AA applied to the second embodiment of the present invention rotates a light source 41 such as a laser diode and a light beam emitted from the light source 41 to read a signal. A diffraction grating 54 for forming ± 1st order diffracted light for the main beam and the track servo, a colliminating lens 55 for advancing the beam passing through the diffraction grating 54 into parallel light, and a disc ( 10. A beam splitter 43 for passing a beam incident on the disk 10 and being modulated by the recording signal formed on the disk 10 to the sensor lens 47, and a beam width of the beam incident on the disk. The numerical aperture control means 30 and the incident beam are focused on the disk 10 so as to change the effective aperture NA of the objective lens 345 by the above principle. An objective lens 45 for receiving an optical signal modulated by the recorded signal and an aperture A conventional focus control movement and tracking, which includes a male adjustment means 30 and an objective lens 45, and a movement for shifting the focus according to the type of the disk 10, and other movements of the position of the disk 10. an actuator movable portion 46 including an actuator movable coil 46a for a control movement, a disk 10 having different thicknesses and recording densities of at least two or more kinds, and a recording signal recorded on the disk 10. And a collimating lens 47 which transmits the optical signal received by the objective lens 43 by the objective lens 43 to the beam splitter 43 and generates astigmatism necessary for focus control. It consists of a photo detector 48 that converts the electrical signal modulated by the effect.

Meanwhile, the numerical aperture adjusting means 30 according to the second embodiment of the present invention may use the same liquid crystal shutter as in the above-described embodiment, or may use an iris type shutter. However, in the second embodiment of the present invention, the aperture means described later can be used.

21 is a perspective view of a pickup base to be applied to the second embodiment of the present invention.

As shown in FIG. 21, reference numeral 200 is a pickup base. The pick-up base 200 is configured as a rectangular parallelepiped box in which one top surface is opened and the other top surface is formed with a semicircular opening 204. In addition, an outwardly projecting shaft 209a for fixing to a predetermined portion on the deck 130 (see FIG. 13) is installed in the protrusion 209 formed at the center of the outside of the pickup base 200.

A predetermined portion of the open portion of the pickup base 200 is provided with a seat portion 202 in the form of a square plate, and a beam splitter 43 is seated on the seat portion 202. At the rear of the beam splitter 43, a cylindrical holder 205 for fixing a collimating lens 55 is provided. Since an opening 205a is formed at one lower side of the holder 205, the holder 205 is fitted to the protrusion 215 provided at the rear of the seating portion 202 on the pickup base 200. The collimator lens 55 is detachably fitted to the holder 205.

A protrusion 216 is installed at one left side of the seating portion 202, and an opening 226a of the holder 226 for fixing the sensor lens 47 is fitted into the protrusion 216. The sensor lens 47 is detachably fitted to the holder 226.

The shutter insertion hole 219 is formed in the center of the pickup base 200 in the vertical direction. An aperture means 110 (FIG. 22) shown in FIG. 22, which will be described later, is inserted into the shutter insertion hole 219. A through hole 248a is provided at a predetermined portion of the side wall 248 of the pickup base 200. FIG. ) Is formed, and a photodetector 48 is inserted into the through hole 248a. In addition, a through hole 258a is formed in the front sidewall 258 of the pickup base 200. The light source 41 is inserted closely into the through hole 258a.

On the other hand, on the pickup base 200, the user can be installed at a suitable position according to the numerical aperture of the numerical aperture adjusting means 30, that is, a predetermined portion between the collimation lens 55 and the light source 41, the diffraction grating 54 Not shown. In addition, a predetermined portion of the semicircular opening 204 may be a folding mirror 208a that is not shown on the optical system AA but seated on a rectangular plate-shaped seating portion 208.

FIG. 22 is an exploded perspective view showing a connection relationship between an aperture means and a driving means to be applied to the second embodiment of the present invention, and FIG. 23 is a perspective view showing a carrier on which the pickup base is to be moved.

As shown in FIG. 22, the aperture means 210 has a cramped shape, and an opening 114 is formed at the center of the vertical plane 212, and a rack is disposed on the horizontal plane 213 formed perpendicular to the vertical plane 112. 216 is formed outward.

A carrier 250 (see FIG. 23) is installed at a lower predetermined portion of the pickup base 200 (see FIG. 21), and the carrier 250 mounts and transports the pickup base 200. As shown in FIG. 23, the U-shaped plate of the carrier 250 is formed on the upper side of each sidewall 252 of the carrier 250 to fix the pickup base 200 to the carrier 250. A leaf spring 254 is provided, and an upper portion of the side wall 252 is formed in a stepped shape, and a screw hole 252a is formed in a surface 253 having a low step height. The part has a threaded through hole 256 formed at a position corresponding to the screw hole 252a formed at the lower surface 253. The leaf spring 254 is formed of a carrier 250 by a screw 258. Is fixed to the side wall 252, wherein the axis 209a of the pickup base 200 is between the leaf spring 254 and the low step surface 253. Is inserted into the installation.

Meanwhile, a motor fixing plate 260 is installed at an inner predetermined portion of the side wall 252 of the carrier 250 to which the pickup base 200 is inserted and moved at the same time, and the motor fixing plate 260 is illustrated in FIG. 22. Motor 220 is installed. The motor fixing plate 260 is fixed with a plurality of screws 260a, as shown in FIG. As illustrated in FIG. 22, the motor 220 is integrally rotatably fitted with the helical gear 224 on the shaft 222. The helical gear 224 is interconnected with the rack 216 of the aperture means 210 described above by placing a plurality of first to third gears 227, 228, 229. The first to third gears 227, 228, and 229 have a plurality of washers 227a, 228a, and 229a and a plurality of rings 227b, 228b and 229b to place the upper and lower shafts 227c, 228c, and 229c ( (See also FIG. 23). The shafts 227c, 228c and 229c are fitted into the plurality of holes 237c, 238c and 239c formed on the carrier 250. Reference numeral 218a denotes a seating portion 218a of the diaphragm means 210.

The detailed description and operation relationship of each component of the optical pickup apparatus according to the second embodiment of the present invention configured as described above will be described in detail as follows.

First, a light beam bundle that can be approximated by linearly polarized light emitted from a light source 41 such as a laser diode passes through the diffraction grating 54 and is tracked by the main beam and the three beam method, which are zero-order diffracted light. It is divided into sub-beams, which are the first-order diffracted light required when using a servo. However, the diffraction grating 54 can be omitted when using the tracking servo by the One-beam method.

Each beam passes through collimating lens 55 and proceeds to parallel light and is incident on the aperture means 210 (see FIG. 22), which is one of numerical aperture adjusting means.

In the second embodiment of the present invention, a liquid crystal shutter and an iris type shutter used as the numerical aperture adjusting means in the above-described first embodiment may be applied. However, the numerical aperture can be adjusted using the aperture means as described above.

24 is a perspective view showing an optical pickup system of a laser coupler type according to a third embodiment of the present invention.

As shown in FIG. 24, the third embodiment of the present invention shows a laser coupler type optical pickup system in which the optical system is integrally formed with the mover 360. As shown in FIG.

In the third embodiment of the present invention, the optical system (see section A in FIG. 3) of the first embodiment is integrally installed in the pickup base 100 (see FIG. 14) which simultaneously performs the function of the mover. First, a photodetector and laser diode assembly 355 shown in FIG. 24, a light source 321 such as a laser diode, as shown in FIG. 25, is installed at a predetermined portion, and an inclined surface 323 is formed of the beam splitter. It will play a role. In addition, the laser coupler includes two photo detectors 326 and 324. That is, as shown in FIG. 25, the light source 321, the inclined surface 323, and the photodetectors 326, 324 are integrally formed in the photo detector and the laser diode assembly 355.

The light emitted from the light source 321 of the photo detector and the laser diode assembly 355 is incident from the optical path by the prism 357 (for example, the liquid crystal shutter or the iris type shutter of the above-described embodiment). After adjusting the numerical aperture of the objective lens to adjust the light beam mirror diameter, the focus is focused on the disk information recording surface to read the information through the photodetector in the inverse of the optical path.

Here, the driving of the numerical aperture adjusting means is the same as that of the first embodiment described above. In addition, the tracking servo and focusing servo method of the pickup device of the laser coupler type is performed by a circuit system as shown in FIG. That is, since the output of the photodetector 326 is B- (A + C) and the output of the photodetector 324 is B '-(A' + C '), the output difference of the photodetectors 326,324 is shown in FIG. As noted, 326-324.

The optical pickup apparatus of the present invention configured as described above can read a low density disc or a high density disc for CD and DVD regardless of thickness by using a simple numerical aperture adjusting means.

Claims (18)

An apparatus for recording / reproducing two or more kinds of discs having different thicknesses, the apparatus comprising: a light source; A beam splitter for transmitting or separating the light beam from the light source; An objective lens for condensing the beam passing through the beam splitter on a disk mounted among disks having different thicknesses and recording densities; Numerical aperture adjusting means arranged between the light source and the objective lens to adjust the numerical aperture of the objective lens to have an effective aperture of 0.27 to 0.56 so as to focus on the mounted disk; And a signal reproducing unit for reproducing information from the light beam reflected from the disc. An apparatus for recording / reproducing two or more kinds of thicknesses, the apparatus comprising: a light source; A beam splitter for transmitting or reflecting a light beam from the light source; An objective lens for condensing the beam passing through the beam splitter on a disk mounted among disks having different thicknesses and recording densities; Numerical aperture adjusting means disposed between the light source and the objective lens and adjusting an effective numerical aperture of the objective lens so as to focus on the mounted disk; A disc discrimination unit having a signal reproducing unit for reproducing information from the light beam reflected from the disc, and determining a type of disc in accordance with a signal output from the signal reproducing unit to a circuit system; A microcomputer which receives a discriminant result of the disc discriminator and controls a system; A numerical aperture adjusting means control unit which receives the output of the signal reproducing unit and controls the numerical aperture adjusting means according to the control of the microcomputer; And a motor controller for controlling the rotational speed of the motor in accordance with the type of the disc. The recording / playback apparatus of claim 1, wherein a diffraction grating is provided between the beam splitter and the light source, and a sensor lens is provided between the beam splitter and the photodetector in the optical system. The recording / playback apparatus of claim 1, wherein the objective lens and the numerical aperture adjusting means are provided at predetermined portions of the actuator, and are connected to each other so as to be movable at the same time. The recording / playback apparatus of claim 1, wherein the disk is either a compact disk having a thickness of 1.2 mm or a high density digital video disk having a thickness of 0.6 mm. The recording / playback apparatus of claim 1, wherein the numerical aperture adjusting means is provided integrally with the light source. The recording / playback apparatus of claim 1, wherein the numerical aperture adjusting means is provided integrally with the objective lens. The recording / playback apparatus of claim 1, wherein the numerical aperture adjusting means is a liquid crystal shutter. 10. The disk of claim 8, wherein the liquid crystal shutter comprises a plurality of transparent substrates, a liquid crystal layer provided between the transparent substrates, a liquid crystal plate on which the plurality of transparent electrodes are patterned, and a polarizing plate. Compatible recording / playback devices. 10. The recording / playback apparatus of claim 9, wherein the liquid crystal plate is formed with an arc-shaped band in order to increase light efficiency and light. 11. The liquid crystal shutter of claim 10, wherein the liquid crystal shutter comprises a light blocking portion provided with a transparent electrode and a light transmitting portion through which light is transmitted, thereby controlling the light blocking portion on / off by applying or blocking a voltage to the transparent electrode. Compatible recording / playback apparatuses for discs of different thicknesses. 12. The liquid crystal shutter according to claim 11, wherein the liquid crystal shutter is composed of a light blocking portion and a light transmitting portion, the light intensity of the light transmitting portion is defined as 1, and the transmission intensity of the transmission portion A is It and the transmission intensity of the blocking portion B is set. If Is, the Contrast Ratio is Compatible recording / playback apparatuses for discs of different thicknesses, characterized in that they are within range. Where CONTRAST RATIO (C.R) = Is / It 3. A compatible recording / playback apparatus for discs of different thicknesses according to claim 2, wherein the numerical aperture adjusting means is an iris type shutter. The shutter of claim 13, wherein the iris-type shutter comprises: first and second blades, a shutter base on which the first and second blades are movably seated, and a shutter cover integrally fitted over the shutter base; And a motor for driving the first and second blades. An optical pickup mechanism for adjusting a numerical aperture by installing a numerical aperture adjusting means in a pickup base provided at a predetermined portion on a deck, the optical pickup mechanism comprising: a pickup transport motor provided at one side of the deck; A plurality of gears sequentially connected to the gear to be inserted into the shaft of the pickup transport motor; A rack gear connected to the gear and fixed to a carrier; A pickup base for mounting components constituting the optical system; A carrier which simultaneously moves by seating the pickup base; And an iris-type shutter installed at a predetermined portion of the pickup base. An optical pickup mechanism for adjusting the numerical aperture by providing a numerical aperture adjusting means in a pickup base provided on a predetermined portion on a deck, the optical pickup mechanism comprising: a pickup base for mounting components constituting an optical system; A motor installed at the rear of the pickup base; A plurality of gears sequentially connected to the helical gear to be inserted into the shaft of the motor; An aperture means connected to the gear and fitted into a shutter insertion hole of a pickup base; Optical pickup device comprising a carrier that is moved at the same time seating the pickup base. A single optical pickup device composed of an optical system and an instrument system, the optical system comprising: a light source and a photodetector assembly in which a light source and a light detector are integrally formed; A prism that forms and transmits light from the light source of the light source and the photodetector assembly; An objective lens for condensing the light transmitted through the prism on any one of disks having different recording densities and thicknesses; It is provided on the optical path on the objective lens and the prism, and is composed of numerical aperture adjusting means for adjusting the numerical aperture of the objective lens in accordance with the shape of the disk, the mechanical system is installed integrally with the optical system Optical pickup device, characterized in that configured as possible Mover (Mover). The optical pickup apparatus of claim 9, wherein the liquid crystal layer is formed of an electrochromic display (ECD).