KR19980014341A - Disc type automatic discriminator - Google Patents

Abstract

An optical disc reproducing apparatus for reproducing a plurality of types of discs having different thicknesses comprises a light emitting element for generating an optical signal and a sensor section composed of a light receiving element for receiving optical signals differently reflected by the difference in disc thickness, The type of the disc is determined according to the presence or absence of the optical signal detected from the light receiving elements of the sensor unit.

Description

Disc type automatic discriminator

The present invention relates to a disc recording / reproducing apparatus and method, and more particularly, to a disc reproducing apparatus capable of automatically discriminating the type of a disc to be inserted in an apparatus for reproducing a plurality of discs.

In general, an optical disc that performs noncontact reading using a laser beam is a typical disc is a compact disc (hereinafter referred to as CD). At present, however, not only high-speed and overwrite but also high density (large capacity) represented by the development of short-wavelength lasers and recording / reproducing technologies are required. On the other hand, a compression method called MPEG (Moving Picture Experts Group) is also put into practical use in the digital image compression technique. Accordingly, a digital moving picture disc media represented by a digital video disc (hereinafter referred to as DVD) will become a key medium for multimedia storage.

1 shows a block configuration of a DVD player. The disc 20 is a high-density optical disc, which can be a DVD. It is also assumed that the pickup unit 111 is a short wavelength optical head, the numerical aperture of the objective lens is 0.6, and the wavelength of the red semiconductor laser is used. The signal amplifier 113 converts an optical signal output from the pick-up unit 112 into an electrical signal and amplifies the optical signal. A demodulator and demodulator 113 demodulates the modulated signal output from the signal amplifier 113 and corrects errors generated during the reproduction process. A servo controller 114 controls the pickup unit 11 by receiving a focusing tracking error signal of the signal amplifier 112 and an output of a demodulation and correction unit 113. The system decoder 116 decodes a DVD system stream output from the demodulation and correction unit 113 and separately outputs the decoded data into a video elementary stream and an audio elementary stream. A video decoder 117 decodes the video data stream output from the system decoder 117 and converts the decoded video data stream into reproducible video data. The encoder 118 encodes the video data output from the video decoder 117 into a corresponding video display system (NTSC or PAL) and outputs the encoded video data to the display unit. An audio decoder 119 converts the encoded audio data stream output from the system decoder 116 into original audio data. A digital-to-analog (D / A) converter 120 converts the data output from the audio decoder 119 into an analog audio signal.

Since the DVD reproducing apparatus uses a modulation scheme, an error correction scheme, and an image coding scheme different from those of a general CD reproducing apparatus, the processing method of the signal system of the DVD and CD reproducing apparatus is completely different. In addition, the pit size and the track pitch of the DVD and the CD are different from each other, and the laser wavelength of the pickup unit 11 and the aperture of the objective lens are different.

In order to achieve high density in the recording and reproducing system of the DVD as described above, it is important to reduce the size of the focusing spot. As a method of performing this, it is necessary to shorten the wavelength of the first laser, (NA) is increased, and thirdly, a modulation scheme having an excellent coding efficiency is used. Of these three methods, the laser uses a red laser semiconductor laser (650 nm-635 nm), the numerical aperture (NA) of the objective lens is 0.6, and the EFM- (Eight to Fourteen Modulation plus).

In order to reproduce information on a high-density optical disc, the optical pickup unit 11 must be capable of forming a small-sized optical focus. The diameter of the optical focal point is proportional to the wavelength of light as shown in Fig. 2 and inversely proportional to the numerical aperture of the objective lens. The current semiconductor laser wavelength is the lower limit of 635 nm as described above. In general, DVD uses a laser wavelength of 650nm as a standard, and CD uses a laser wavelength of 780nm. Meanwhile, in the numerical aperture (NA) of the objective lens, the DVD is 0.6, whereas the CD is 0.45, so that the optical focal diameter of the DVD is about 60% or more of the optical focal diameter of the CD. Therefore, the DVD can acquire a reproduction signal equivalent to a CD on an optical disc having a surface recording density of about 2.6 times the CD. The DVD can realize the improvement of the reproduction waveform by the substance circuit processing, and as shown in FIG. 3, the DVD can have a surface recording density of about 4.2 times the CD.

The characteristics between DVD and CD having the above characteristics are shown in Table 1 below.

CD DVD Disk diameter 120mm 120mm DVD is a double-sided multi layer Disc thickness 1.2 mm 0.6mm Recording capacity 640Mbyte 4.7 Gbyte For single-sided single layer Laser wavelength 780 nm 650 nm The numerical aperture of the objective lens 0.45 0.6 Minimum foot size 09.μm 0.4μm Track pitch 1.6 袖 m 0.74 μm Modulation method EFM EFM-plus Error correction method CIRC RS-PC

In Table 1, it can be seen that the CD and the DVD have many differences. Here, it can be seen that the DVD is determined as a result of obtaining the optimum solution from the keyword of high-density recording, digital processing, and CD size. However, since the accumulation of the vast amount of soft assets of the CD can not be ignored, compatibility with CD and DVD is very important. One of the main reasons that the compatibility between the DVD and the CD is obstructed is that the thickness of the disc is different. That is, in order to reproduce the information on the disc, a part of the optical system is formed according to the thickness of the disc, so that the objective lens is designed according to the thickness of the disc. Therefore, if the thickness of the disk deviates from the designed value, spherical aberration occurs and the number of optical focal points deteriorates. In other words, the DVD has a thickness of 0.6 mm, whereas the CD has a thickness of 1.2 mm, which means that two discs can not be reproduced by one pickup unit. Therefore, a separate optical pickup unit must be used for compatibility between the CD reproducing apparatus and the DVD reproducing apparatus.

In order to solve the above problems, a bipolar optical pick-up unit as shown in FIG. 4 has been proposed. The optical pick-up unit shown in FIG. 4 has both the optical focus for DVD and the optical focus for CD at a distance in the optical axis direction, thereby solving the problem caused by the thickness difference of the disc. The principle of the two-way optical pickup as shown in FIG. 4 is to overlap two kinds of lens action by using a hologram. The numerical aperture of the objective lens of the pickup apparatus is set to 0.6 in conformity with the DVD standard, but a hologram for refracting a part of the light at the central portion thereof by the diffraction is arranged. Therefore, the light not diffracted in the hologram is converged at the objective lens having the numerical aperture of 0.6 to form the optical focal point of the DVD, and the diffracted light is a CD having a composite lens numerical aperture of 0.4 of the hologram and the objective and a thickness of 1.2 mm A hologram is formed.

Therefore, when the optical pickup as shown in FIG. 4 is used, the optical focus for CD is formed at a position farther than the optical focus for DVD. At this time, the photodetector is disposed on the photodetector so that a reflection image of the optical focussed on the disk can be formed. Therefore, when the DVD is reproduced, the optical focus for DVD converges on the disc, and the optical focus for CD becomes a blurred image that is misaligned with the focus. Therefore, an image of the optical focus for DVD is formed on the optical detector, but the reflected light in the optical focus for the CD is diffused over a wide range, so that no external shock is given to the reproduction of the DVD. And is opposite to the DVD at the time of reproducing the CD.

However, in the case where the optical disc player has a pickup device capable of simultaneously reproducing DVD and CD, or a system having a pickup device capable of independently reproducing DVD and CD, To be able to operate in a mode of operation. As a method of discriminating a disc to be inserted in the optical disc reproducing apparatus, there is a method of comparing the magnitude of the focus error detection signal of the optical focus reproduced by the optical pickup as described above, or comparing the magnitude of the RF signal according to the pit size, It is necessary to determine whether the disc being played is a DVD or a CD. However, the conventional method of discriminating the type of the disc as described above inspects the focus error and the RF signal of the optical signal received from the pick-up unit 111, so that it takes much time to determine the type of the loaded disc. Further, in the case of discriminating the disc type using the focus error detection and the magnitude of the RF signal as described above, the reproduction signal is set to the initial set value due to the state of the disc (dirt adherence, eccentricity, warping, etc.) There is a problem that an error in disc discrimination may occur.

Therefore, in order to solve the above problems and to quickly and accurately determine the type of inserted disc, it is necessary to determine the type of disc by detecting the thickness of the loaded disc.

It is therefore an object of the present invention to provide an apparatus for automatically discriminating the type of inserted disc in an apparatus for reproducing a plurality of disc types.

It is another object of the present invention to provide an apparatus for automatically discriminating the type of a disc by sensing the thickness of a disc inserted in an apparatus for reproducing digital video discs and compact discs.

According to an aspect of the present invention, there is provided an optical disc reproducing apparatus for reproducing a plurality of types of discs having different thicknesses, the optical disc reproducing apparatus comprising: And a sensor unit formed of a light receiving element for receiving optical signals, and the type of the disk is determined according to the presence or absence of an optical signal detected from the light receiving elements of the sensor unit.

1 is a diagram showing the configuration of a disk recording / reproducing apparatus

2 is a diagram for explaining the relationship between the wavelength of light and the numerical aperture of the objective lens and the optical focal diameter in the disk recording / reproducing apparatus

3 is a diagram for explaining the relationship between bits and optical focal point for a digital video disk and a compact disk

4 is a view for explaining the principle of a two-focal point positive optical pickup

Figures 5A-5C are cross-sectional views of a digital video disk and a compact disk

6 is a view for explaining a mounting position of a sensor for discriminating the type of a disc according to an embodiment of the present invention;

7 is a view for explaining the sensor body configuration of Fig. 6

8A to 8C are diagrams for explaining an operation of detecting an optical signal sensed by a sensor according to the type of a disc in the embodiment of the present invention

9 is a diagram showing a configuration of an apparatus for discriminating the type of a disc by analyzing an optical signal sensed by a sensor according to an embodiment of the present invention

5A is a plan view of the optical disk, which is composed of a region 25 for recording data in the inner circumferential direction of the disk, a boundary region 26 of the data recording region 25, and a transparent surface portion 27 in which data is not recorded. 5B and 5C are sectional views of the disc, FIG. 5B is a sectional view of the DVD, and FIG. 5C is a sectional view of the CD. As shown in FIGS. 5B and 5C, CD and DVD have different thicknesses.

FIG. 6 is a view showing a mounting position of the sensor unit 10 for discriminating the inserted disc according to the embodiment of the present invention. The sensor unit 10 is installed on a deck chassis, 10 in the inner side of the disk 10 so that an optical signal can be generated and received on the surface of the disk 10. The reason why the sensor unit 10 is provided on the deck chassis at the lower end of the disk surface portion 27 as described above is that the reflectance of the optical signal is good in the transparent portion of the disk 20 and the inner circumferential direction of the disk becomes the center position upon rotation, This is because the influence of the tilt of the disk is small.

7 is a view showing an external shape of the sensor unit 10, in which a light emitting element 11 and a light receiving element 12 are provided on the body of the sensor unit 10. [ The body of the sensor unit 10 is fixed to the inside of the deck chassis so as to generate and receive optical signals on the surface portion 27 of the disk 20 as described above.

8A is a diagram showing a state in which an optical signal generated in the light emitting element 11 during DVD reproduction is reflected by the DVD 21 and reaches the light receiving element 12. [ 8B is a diagram showing a state in which the optical signal generated in the light emitting element 11 during CD reproduction is reflected by the CD 22 and does not reach the light receiving element 12. [ 8C shows that the light receiving positions are different due to different reflection distances of optical signals generated in the light emitting device 11 depending on the thickness difference of the DVD 21 and the CD 22. Therefore, the spacing distance between the light emitting element 11 and the light receiving element 12 is determined by measuring the distance and angle at which the optical signal is reflected according to the distance between the sensor unit 10 and the disk 20 and the thickness of the DVD 21. This is because the optical signal generated in the light emitting element 11 is reflected according to the thickness of the DVD 21 to reach the light receiving element 12 and the optical signal generated in the light emitting element 11 is reflected according to the thickness of the CD 22 and reaches the light receiving element 12 The interval is determined. 8A to 8C, the light emitting device 11 may be a light emitting diode (LED), and the light receiving device 12 may be a photo detector.

8A to 8C, the optical signal generated by the light emitting device 11 of the sensor unit 10 is reflected from the disk 20 mounted on the disk-mounted turntable. At this time, when the inserted disc 20 is the DVD 21, the optical signal detected by the light receiving element 12 exists. As described above, when the optical signal is detected by the light-receiving element 12, the optical signal is analyzed by current-voltage conversion, so that it can be determined that the inserted disc 20 is the DVD 21. However, when the light receiving element 12 can not detect the optical signal reflected from the disc 20 in the state that the disc 20 is mounted, the control unit 40 determines that the mounted disc 20 is CD22.

In the embodiment of the present invention, the optical signal irradiated from the light emitting device 11 may be irradiated at 90 degrees from the front, and a method of receiving an optical signal dispersed at a specific angle may be used. However, in order to receive a more precise optical signal, the light emitting element 11 may be inclined so as to be irradiated at an angle with a specific angle without irradiating the optical signal on the surface of the disk at 90 degrees from the front.

In the embodiment of the present invention, the light receiving element 12 detects the reflected optical signal of the DVD 21, but the same function can be performed even when the light receiving element 12 detects the reflected optical signal of the CD 22.

9 shows a configuration of an apparatus for automatically discriminating a disc 20 mounted in an optical disc reproducing apparatus having a sensor unit 10 according to an embodiment of the present invention. First, the light receiving element 12 of the sensor unit 10 is installed close to the inner center of the deck chassis as described above, and receives an optical signal reflected by the surface portion 27 of the disk 20 to generate an A signal converted into an electrical signal. The amplifier 31 amplifies and outputs the fine level A signal output from the light receiving element 12. The comparator 32 compares the A signal output from the amplifier 31 with the set reference signal REF and generates a logic high signal indicating that the disc loaded when the reference signal REF is higher than the set reference signal REF is DVD21. The amplifier 31 and the comparator 32 are discriminators 30 for discriminating the type of the disc by analyzing the received light signals. In the exemplary embodiment of the present invention, the determination unit 30 may include an analog-to-digital converter (ADC).

The control unit 40 receives a comparison signal output from the comparator 32 and generates a signal CTL1 for controlling the DVD drive unit 50 or a signal CTL2 for controlling the CD drive unit 60. [ That is, when the comparator 32 outputs a logic high signal, the control unit 40 detects that the loaded disc 20 is the DVD 21 and drives the DVD driving apparatus 50. When the comparator 32 outputs a logic low signal, the control unit 40 determines that the loaded disc 20 is not the DVD 21, and drives the CD drive unit 60.

When the determination unit 30 is configured by an A / D converter, the control unit 40 sets and stores a reference value for determining the type of the disc in advance, and compares the data output from the A / D converter with the set reference value Thereby discriminating the type of the disc 20.

In the embodiment of the present invention, the types of discs having different thicknesses of the discs are exemplified by DVD and CD, but they may be used equally to discs having different thicknesses.

It is possible to automatically determine the type of the inserted disc in the apparatus for reproducing a plurality of discs as described above. Particularly, it is possible to quickly identify the type of the disc by sensing the thickness of the disc and discriminating the type of the disc, and furthermore, since the sensor part is fixed to the inner transparent part of the disc, can do. Therefore, there is an advantage that the type of the loaded disc can be quickly and accurately discriminated in the DVD reproducing apparatus capable of CD playback.

Claims (2)

There is provided an optical disc reproducing apparatus for reproducing a plurality of types of discs having different thicknesses including a light emitting element for generating an optical signal and a sensor section composed of a light receiving element for receiving optical signals differently reflected by the disc thickness difference And discriminates the type of the optical disc based on the presence or absence of an optical signal detected from the light receiving elements of the sensor unit. The optical disc reproducing apparatus as claimed in claim 1, wherein the light emitting element is installed to be inclined to irradiate an optical signal to the disc at a specific angle.