KR20000043525A - Method for setting optical wavelength of optical disc player - Google Patents

Abstract

PURPOSE: A method for setting an optical wavelength of an optical disc player is provided to improve a reflecting efficiency by using the optical wavelength of 650nm for a video disc group and a CD-RW and using the optical wavelength of 780nm for a compact disc group except the CD-RW. CONSTITUTION: A laser diode having a 650nm wavelength is predetermined. A focus is up/down by performing a regulating operation of focusing. A kind of optical disc is decided from a playing signal which is detected from the step of focus up/down. If the kind of optical disc is a digital videodisc group and a CD-RW, the laser diode having the 650nm wavelength predetermined at first is maintained. When the kind of optical disc is a compact disc group except the CD-RW, the laser diode is changed to a laser diode having the 780nm wavelength.

Description

Optical wavelength setting method of optical disc player

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for setting an optical wavelength of an optical disc reproducing apparatus, and more particularly, to determine an optical disc type and to set a wavelength of light generated by a laser diode having high reproduction efficiency according to the type of the optical disc. A method of setting the optical wavelength of a device.

In general, an optical disc reproducing apparatus is a device for reproducing information by detecting an amount of light reflected by a laser diode reflected on a pit of an optical disc. It can be divided into a video disc (DVD). In addition, a compact disc includes a CD in which an audio signal can be recorded and reproduced or only reproduced according to the information, or a CD-R (CD-Read or CD-ROM) and information in which various kinds of information are recorded by an encoding method. Can be divided into CD-RW (CD-Rewritable or CD-RAM), which can perform recording and playback operations. In addition, a digital video disc has a DVD-S (DVD-Single) having one layer on a track, and a DVD-D (DVD having two layers on a track and independently records information on each layer). -Dual).

In the optical disc, pits corresponding to the recorded information are formed in a structure having periodicity on the track. Then, the objective lens is configured to detect the amount of light reflected by the information recording surface of the optical disk after being emitted from the laser diode to reproduce the information.

Here, the method of determining the wavelength of the light emitted from the laser diode is as shown in Figures 1a and 1b. That is, when light is focused at a point where no pit is formed, as shown in Fig. 1A, the reflected light is detected by the light receiving sensor because the wavelength of the light matches the distance between the laser diode and the reflecting film.

However, when light is focused at the point where the pit is formed, as shown in Fig. 1B, since the pit is formed at a height corresponding to 1/4 wavelength from the reflective film, the reflected light reflected on the reflective film and the reflected light reflected on the pit are mutually The amount of light detected by the light receiving sensor is reduced due to interference. Therefore, the light receiving sensor can detect the presence or absence of the pit.

Conventionally, the wavelength of light is determined based on the height of the pit formed on the CD among compact discs and the height of the pit formed on the DVD among digital video discs. Another variable that determines the wavelength of light is the distance difference between the laser diode and the bottom surface of the optical disk. That is, in determining the wavelength of the light emitted from the laser diode, it is largely divided into compact discs and digital video discs. The wavelength of light is used to use the compact discs as 780 nm and the digital video discs as 650 nm. Prescribed. Therefore, only compact discs could be reproduced in the optical disc reproducing apparatus having a wavelength of 780 nm, and only digital video discs could be reproduced in the optical disc reproducing apparatus having a wavelength of 650 nm.

On the other hand, as an optical disc reproducing apparatus using a mixture of compact discs and digital video discs has recently been proposed, a laser diode generating light having a wavelength of 780 nm and a light having a wavelength of 650 nm are generated inside the apparatus. Sometimes laser diodes are used.

However, according to the conventional optical disc reproducing apparatus, the following problem occurs.

In other words, although CD-RW of compact discs is processed similarly to digital video discs in the form of the pit (that is, the height of the pit), the classification is classified as compact discs, so that the optical wavelength of 780 nm It is prescribed to use. As a result, the reflection efficiency is lowered, which causes noise or errors in the reproduction signal.

Accordingly, an object of the present invention is to solve such a problem, and an object of the present invention is to provide an optical disc reproducing apparatus capable of simultaneously reproducing compact discs and digital video discs. The optical wavelength setting method of the optical disk reproducing apparatus having improved reflection efficiency by using optical wavelength of 650 nm for discs and CD-RW and optical wavelength of 780 nm for optical discs other than CD-RW In providing.

1A and 1B are diagrams for explaining a principle of reading information by using an interference principle of light by a pit,

2 is a schematic block diagram of an optical disk reproducing apparatus applied to the present invention;

FIG. 3 is experimental data obtained by measuring the reflection efficiency of each type of optical disk when using an optical wavelength of 780 nm and an optical wavelength of 650 nm.

4 is a flowchart illustrating an operation of the optical wavelength setting method of the optical disk reproducing apparatus according to the present invention.

<Description of the code | symbol about the principal part of drawing>

101: light receiving sensor 102: regeneration amplifier

103: waveform equalizer 104: shaper

105: sync signal generator 106: discriminator

107: phase comparator 108: low pass filter

109: voltage controlled oscillator 110: decoder

111: central processing unit

A feature of the present invention for achieving the above object is an optical disc reproducing apparatus comprising a laser diode having a wavelength of 780 nm and a laser diode having a wavelength of 650 nm: setting a laser diode having a wavelength of 650 nm; Perform focusing adjustment operations to raise and lower the focus; Determining the type of optical disc from the detected playback signal; If the types of optical discs are digital video discs and CD-RW, the laser diode is initially kept at a wavelength of 650 nm; If the type of optical disc is compact discs other than CD-RW, it is set to change to a laser diode having a wavelength of 780 nm.

Here, if the duty value of the focus error signal detected as the focus adjustment operation is larger than the first reference value is determined as a compact disc, if the duty value of the focus error signal is smaller than the first reference value, the digital video disc If the level of the focus error signal is smaller than the preset second reference value, it is determined by the CD-RW.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, in adding reference numerals to the elements of each drawing, it should be noted that the same elements are denoted by the same reference numerals as much as possible even if they are displayed on different drawings. In addition, in the following description, many specific details are shown, such as specific blocks or components of circuits, which are provided to help a more general understanding of the present invention, and the present invention may be practiced even if these specific details are removed or modified. It will be obvious to those of ordinary skill in the art. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

2 shows a schematic block diagram of an optical disk reproducing apparatus applied to the present invention, and FIG. 3 shows experimental data measuring reflection efficiency for each type of optical disk when using an optical wavelength of 780 nm and an optical wavelength of 650 nm. FIG. 4 is a flowchart showing the operation of the optical wavelength setting method of the optical disc reproducing apparatus according to the present invention.

2, the light receiving sensor 101 receives the reflected light reflected by the information recording surface of the optical disk, and converts the received light amount into an electrical signal.

The reproduction amplifier 102 amplifies the reproduction signal converted by the light receiving sensor 101 to a size suitable for signal processing. Also, the reproduction amplifier 102 may be used to increase the signal-to-noise ratio (SN ratio) of the output by limiting the high frequency band of the signal and noise frequency spectrum, or in some cases, to stabilize the amplitude of the reproduction output. Performs Automatic Gain Control (AGC).

The waveform equalizer 103 modifies the waveform of the reproduction signal amplified by the reproduction amplifier 102 to reduce the interference between the waveforms, thereby achieving higher density.

The shaper 104 shapes the playback signal corrected by the waveform equalizer 103 and converts it into a pulse signal indicating the presence or absence of a playback signal.

The synchronizing signal generator 105 generates a synchronizing signal synchronized with the basic period of the pulse signal converted by the shaper 104 and outputs the synchronizing signal to the discriminator 106. Here, the synchronization signal generator 105 is composed of a phase comparator 107, a low pass filter 108, and a voltage controlled oscillator 109. Since the operation of the synchronization signal generator 105 corresponds to a well-known technique, Detailed description will be omitted.

The discriminator 106 detects whether a pulse signal exists in a predetermined time period (that is, a detection window) by using the synchronization signal provided from the synchronization signal generator 105.

The decoder 110 demodulates the detection code string detected by the discriminator 106 into a data bit string.

The central processing unit 111 controls the respective components above. In particular, the central processing unit 111 determines the type of the optical disk according to the optical information received by the light receiving sensor 101 and drives a laser diode having an optical wavelength corresponding thereto.

Referring to Figures 3 and 4 with respect to the operation of the present invention configured as described above are as follows.

When the reflected light reflected from the information recording surface of the optical disc is received by the light receiving sensor 101, the light receiving sensor 101 outputs an electrical reproduction signal corresponding to this light amount. The reproduction signal is amplified by the reproduction amplifier 102 and then input to the waveform equalizer 103. The waveform equalizer 103 corrects the waveform of the input reproduction signal. The shaper 104 determines the presence or absence of a reproduction signal from the reproduction signal waveform corrected by the waveform equalizer 103 and converts it into a digitized pulse signal, and the synchronization signal generator 105 corresponds to the period of the converted pulse signal. The synchronizing signal synchronized with the pulse signal is outputted to the discriminator 106.

The discriminator 106 determines whether a pulse signal exists in units of a predetermined period in response to the synchronization signal provided from the synchronization signal generator 105, and the detected result is transmitted to the data bit string by the decoder 110. By the conversion, the user can grasp the reproduced information.

In this case, when the light emitted from the laser diode is reflected from the information recording surface of the optical disk and received by the light receiving sensor 101, that is, the reflectance is experimentally calculated, as shown in FIG. 3, CD and CD-R are 780 nm. The reflectance is high when the optical wavelength is used, and the reflectance is high when the optical wavelength of 650 nm is used for CD-RW and digital video discs.

Therefore, the central processing unit 111 initially sets the optical wavelength of the optical disc reproducing apparatus to 650 nm (S1).

Then, when the playback mode is selected by the user (S2), the central processing unit 111 up / down the focus to perform the focusing adjustment operation on the mounted optical disk (S3). Accordingly, the CPU 111 determines the type of the optical disc currently mounted (S4) based on the detected various information. Here, when the type of the optical disc is roughly described, the reproduction signals A, B, C, and D provided from the four-segmented light receiving sensor 101 are synthesized by performing the focus adjustment operation. A high frequency reproduction signal RF Sum is generated. The duty values of the reproduction signals generated by this process are compared to distinguish compact discs and digital video discs. In other words, if the duty value of the focus error signal is large, it can be discriminated as a compact disc, and if the duty value of the focus error signal is small, it can be discriminated as a digital video disc.

In addition, when a CD-RW is played back in the digital video disc playback mode, the focus error signal is detected to be extremely small compared to other optical discs, and the DVD-D is characterized by detecting two peak portions of the focus error signal. .

In step 4 (S4), if the type of the optical disk is determined to be a digital video disk (S5) or CD-RW (S6), the central processing unit 111 sets the optical wavelength of the optical disk reproducing apparatus to an initial value ( In other words, if the type of the optical disk is determined to be CD or CD-R (S7), the optical wavelength of the optical disk reproducing apparatus is changed to 780nm (S8).

In this way, when the setting operation of the optical wavelength for each type of optical disc is completed, the reproduction operation is performed (S9).

Therefore, the reproduction efficiency of the CD-RW can be increased.

As described above, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As a result, according to the optical wavelength setting method of the optical disc reproducing apparatus according to the present invention, the following advantages occur.

In other words, by determining the type of the optical disc mounted, if the optical disc is a digital video disc and CD-RW, an optical wavelength of 650 nm is used, and if the optical disc is a compact disc except CD-RW, an optical wavelength of 780 nm is used. The reflection efficiency is improved, and accordingly the reproduction efficiency is also improved.

Claims (2)

In an optical disc reproducing apparatus comprising a laser diode having a wavelength of 780 nm and a laser diode having a wavelength of 650 nm: Setting a laser diode having a wavelength of 650 nm; Performing focusing operation to up / down the focus; Determining the type of optical disc from the playback signal detected from the focus up / down steps; Maintaining the laser diode having a wavelength of 650 nm initially selected if the type of the optical disc is digital video discs and CD-RW in the determining step; And And changing the setting to a laser diode having a wavelength of 780 nm if the type of the optical disc is a compact disc other than the CD-RW in the discriminating step. The method of claim 1, wherein the determining step, If the duty value of the focus error signal detected as the focus adjustment operation is larger than the first reference value is determined, the compact disc is determined; If the duty value of the focus error signal is smaller than the first reference value, the digital video disc is determined; And determining the CD-RW if the level of the focus error signal is smaller than a second preset reference value.