JP2007141353A - Optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease signal deterioration in data transfer from a pickup to a main board and from the main board to the pickup. <P>SOLUTION: In an optical disk device, an optical pickup is equipped with: a light detection part for receiving reflected light from the optical disk, converting each of the light intensity into currents by a plurality of photo diodes, converting the currents into a voltage values, and outputting an RF signal, and the like, by calculation; an RF signal processing part for correcting frequency characteristics of the RF signal which is one of the output of the optical detection part; an A/D conversion part for A/D converting output of the RF signal processing part; an RF signal modulation part for superimposing the RF digital signal outputted from the A/D conversion part on a high frequency carrier; and a transmitting part for wirelessly transmitting the RF signal modulation part. The main board is equipped with: a receiving part for receiving a wireless signal transmitted from a transmitting part; an RF digital signal demodulating part for demodulating the RF wireless signal received in the receiving part; and an information signal reproduction part for processing the digital signal demodulated by the RF digital signal demodulating part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an apparatus for recording information on an optical disc or reproducing information from an optical disc, and more particularly to a method for transmitting a signal from an optical pickup unit to an electric circuit board unit.

  In the optical disk recording device market, recording and reproduction speeds are increasing year by year. With the increase in speed, an optical pickup unit (hereinafter referred to as pickup) and a flexible printed wiring board (hereinafter referred to as “pickup”) from the main board to the main board. FPC bandwidth is not enough for data transfer with FPC). Noise is likely to appear on weak electrical signals.

  As the recording speed increases, a high-power laser light source is required, and there are problems such as deterioration in performance of components due to heat generation of the laser drive circuit, deterioration of life, and malfunction. The following proposals have been made as means for solving these problems.

  In Patent Document 1, a clock for generating a recording clock from modulation data transferred from the main board to the pickup is suppressed to less than 4 ns in order to suppress the skew between the divided recording clock and the modulation data by transfer by FPC from the main board to the pickup. An apparatus having a recovery unit and a write strategy for generating recording timing from modulation data and a recording clock has been proposed.

  In Patent Document 2, noise is reduced due to crosstalk with respect to various signals such as a weak electric signal detected and output by a photodetector or a Hall element, which is transmitted through an FPC connecting a pickup and a main board. For this reason, there has been proposed a method in which an actuator driving IC is provided in the optical pickup without using an FPC as a driving signal for driving the objective lens.

  Patent Document 3 proposes a method in which a light source and an optical fiber are provided in the device fixing portion, and light from the light source is emitted to the device movable portion side through the optical fiber. Further, an RF light receiving element and an optical fiber are provided in the device fixing portion, and reflected light from the optical recording medium is guided to the RF light receiving element through the optical fiber in the device fixing portion. Although an optical fiber is used, a method has been proposed in which bending resistance or the like is not a problem because it is in the device fixing portion.

JP 2005-216356 A (pages 4 and 5) JP 2001-84624 A (page 2) JP 2002-342970 A (6th page)

  However, the conventional optical disc recording / reproducing apparatus has the following problems.

  The first problem is that, in the case of high-speed playback, the problem is that the FPC bandwidth is not enough, in addition to the signals of References 1 and 2, in addition to the weak electrical current detected by the photodetector of the optical pickup. The signal is transferred to the main board.

  In the DVD standard, 16 times speed is the upper limit, and the channel clock frequency of DVD-RAM is 466.88 MHz (= 29.18 MHz * 16). Furthermore, when the speed is increased in the future in the Blu-ray disc standard, the channel clock frequency is 660 MHz (= 66 MHz * 10) assuming about 10 times speed. The amplitude of the output waveform of the photodetector attenuates as the frequency component becomes higher due to interference as the recording density of recording data increases in the linear direction. It is necessary to transfer an analog signal whose amplitude is attenuated to the main board. In some optical disc recording / reproducing apparatuses, it is a very difficult condition considering that the length of the FPC reaches 30 cm. Problems such as electromagnetic interference, wiring delay, heat generation, crosstalk, and impedance mismatching are expected to be prominent.

  The second problem is that in Reference 3, an electrical signal is sent from the optical pickup to the main board using an optical fiber. However, since both ends of the optical fiber are fixed to fixed portions, there is no degree of freedom in design. . In addition to the optical pickup, the optical part such as an optical fiber and a lens is attached to the fixed part, so that the adjustment of the optical part increases, which becomes a bottleneck in mass production.

  The present invention has been made to solve the above-described problems, and has a circuit configuration in which there is no crosstalk in the data transfer from the pickup to the main board and from the main board to the pickup and is not limited to the FPC band. An object of the present invention is to provide a digital data recording / reproducing apparatus. It is another object of the present invention to provide a digital data recording / reproducing apparatus having a circuit configuration that increases the degree of design freedom.

  The first problem is an optical disc apparatus for recording or reproducing information on an optical disc, the optical disc irradiating the optical disc with laser light, and the optical disc based on reflected light from the optical disc detected by the optical pickup And a main substrate having at least a recording signal processing unit for generating and processing recording data, and the optical pickup receives reflected light from the optical disc. A light detection unit that converts light intensity into current by a plurality of photodiodes, converts the current into a voltage value, and outputs an RF signal or the like by calculation, and an RF signal that is one of the outputs of the light detection unit An RF signal processing unit for equalizing high frequency components of the signal, and a first A / D conversion unit for converting the output of the RF signal processing unit from an analog value to a digital value; Wherein the main substrate can be solved by an optical disk apparatus, characterized in that it comprises an information signal reproducing section for processing the digital signal converted into digital data by the first A / D conversion unit.

  In the data transfer from the pickup to the main board and from the main board to the pickup, signal deterioration can be reduced.

  The first embodiment will be described below with reference to the drawings. FIG. 1 is a block diagram of a first embodiment showing an embodiment of an optical disk apparatus of the present invention.

  Here, 1 is a DVD or CD optical disk, 2 is an optical pickup unit, 3 is a DVD laser, 4 is a CD laser, 5 is an optical system (5a and 5b are lenses, and 5c is a half mirror (beam splitter). ) 5d is a beam splitter, 5e is a wide band quarter wave plate, 5f is a collimating lens, 5g is an objective lens, 5h is a diffraction grating), 6 is a light detection unit, 6-1 is a main beam receiving unit, 6- 2 and 6-3 are sub beam detectors, 7 is a front monitor light detector, 8 is an actuator, 9 is a main board, 10 is an RF signal receiver, 11 is an RF signal demodulator, 12 is a transmission signal generator, 14 Represents an information signal reproduction unit, 16 represents a host computer, and 17 represents a control unit.

  The optical disk 1 is held and rotated by a spindle motor (not shown), and an optical pickup unit 2 emits semiconductor lasers 3 and 4 that emit laser light for recording or reproducing information, and light from the semiconductor laser. Optical system 5 formed as a light spot on the disk surface, and light reception for detecting reflected laser light for performing light spot control such as information reproduction and automatic focus and track tracking using reflected light from optical disk 1 Unit 6, a front monitor light receiving unit 7 for monitoring the amount of laser light, and an actuator 8 for finely adjusting the objective lens in order to improve the light spot quality, record information on the optical disc 1, and information on the optical disc 1 Play back.

  The semiconductor laser 3 is for DVD, and the semiconductor laser 4 is for CD. A light source is selectively switched by either a CD system or a DVD system as a disk to be read.

  The light obtained by the light detection unit 6 is used for detection of an information signal recorded on the optical disc, and detection of a tracking error signal and a focus error signal.

  The light obtained by the front monitor light detection unit 7 is used to optimally write information on the optical disc by detecting the light amounts of the DVD laser 3 and the CD laser 4 and controlling the intensity of the laser light.

  Light from the light detection unit 6 and the front monitor light detection unit 7 is converted into a current corresponding to the intensity of the light, and converted into a voltage by a current-voltage conversion unit (not shown) 9. The signal converted into the voltage is converted into a radio signal by the transmission signal generator 12 and wirelessly transmitted to the RF signal receiver 10 of the main board 9. The RF signal receiving unit 10 receives an RF radio signal, and the RF signal demodulating unit demodulates the RF signal. The light detection unit 6 and the transmission signal generation unit 12 will be described later. The demodulated RF signal is subjected to reproduction processing by the information signal reproduction unit 14 and a reproduction signal is output. Further, the information signal reproducing unit 14 outputs a tracking error signal and a focus error signal to control the spindle motor and the actuator 8. Information on the light intensity from the front monitor light detector 7 is also processed by the information signal reproducing unit, a laser power control signal is output, and the laser control unit (not shown) performs the DVD laser 3 or the CD laser. The light intensity of 4 is optimally set.

  The optical disk apparatus is connected to a host computer (hereinafter referred to as “host”) 16 such as a personal computer or a workstation, and receives instructions and information data from the host 16 through a control unit 17 constituted by a microcomputer or the like. Perform recording, playback, and seek operations (moving the head to the target track). At the time of recording, signals such as recording data and a recording clock are transferred from a recording signal processing unit (not shown) to a laser control unit (not shown).

  The DVD optical system will be described. A DVD light beam having a wavelength of about 660 nm is emitted as divergent light from the DVD laser 3, and is reflected by a half prism (beam splitter) 5d via a diffraction grating (not shown). The light beam is split into three beams by the diffraction grating, and the main beam (0th order diffracted light) and the laser beam are diffracted to generate two sub beams (± 1st order diffracted light). These lights are used for tracking error detection by a differential push-pull method (hereinafter referred to as “DPP method”).

  Subsequently, the light passes through the wideband quarter-wave plate 5e, is guided to the collimator lens 5f, is converted into a parallel light beam, is reflected in the direction of the optical disk by a rising mirror (not shown), and is mounted on the actuator 8. The light is focused on the optical disk by the objective lens 5g. The DVD light beam is reflected by the optical disk, passes through the objective lens 5g, the rising mirror (not shown), the collimator lens 5f, the half mirror (beam splitter) 5c, and the detection lens 5a, and reaches the light detection unit 6.

  The light beam is given a predetermined astigmatism when passing through the half mirror 5c, and is used for detecting a focusing error signal of the optical disc by the astigmatism method.

  The light detection unit 6 includes a four-divided light receiving unit 6-1 for receiving a main beam, and sub beam receiving units 6-2 and 6-3 disposed so as to sandwich the light receiving unit 6-1. Details of the light detection unit 6 will be described later.

  In order to increase the reliability of the detection error signal, the light detection unit 6 may have four (upper and lower two) sub-beam light receiving units and eight (upper and lower four). As the number of light receiving portions increases, the calculation becomes more complicated, but the reliability of the detection error signal increases.

  Further, a part of the DVD light beam is reflected by a DVD front monitor mirror (not shown) above the half prism 5 d and guided to the DVD front monitor light detection unit 7.

  Next, the CD optical system will be described. A CD light beam having a wavelength of about 780 nm is emitted from the CD laser 4 as divergent light, and is reflected by a half prism (beam splitter) 5d and a dichroic half mirror (beam splitter) 5c through a correction lens and a diffraction grating 5b. The light passes through the band quarter-wave plate 5e, is guided to the collimator lens 5f, and is converted into a substantially parallel CD light beam. The CD light beam emitted from the collimator lens 5f is reflected in the direction of the optical disk by a rising mirror (not shown), and is condensed on the optical disk by the objective lens 5g mounted on the actuator 8. The CD light beam is reflected by the optical disc, and passes through the objective lens 5g, the rising mirror (not shown), the collimating lens 5f, the wideband quarter wavelength plate 5e, the dichroic half mirror 5c, and the detection lens 5a, and the light detection unit Reach 6 A part of the light is reflected by a CD front monitor mirror (not shown) on the upper part of the dichroic half mirror 5 c and guided to the front monitor light detection unit 7.

  Next, wireless transmission of an RF signal from the light detection unit 6 to the main board 9 will be described. The main beam to which astigmatism is given is received by the four-divided light unit 6-1, and a focus error signal is obtained by multiplying the four received light amounts. Further, the two sub beams generated by the DPP method are received by the sub beam light receiving units 6-2 and 6-3, and a tracking error signal is obtained from the difference between the two received light amounts. The focus error signal and the tracking signal are transferred to the main board 9 by FPC.

  The signals from the four regions of the light receiving unit 6-1 are added together, and the RF processing unit 121 generates an RF (Radio Frequency) signal. The RF signal is superposed on the RF signal by the RF signal modulator 123, the analog data is converted to digital data by the A / D converter 122, and is wirelessly transmitted from the transmitter 124. The frequency of the carrier signal is set to a frequency that does not adversely affect the housing.

  The wirelessly transmitted signal is received by the RF signal receiving unit 10 of the main board unit 9. The RF signal demodulator 11 demodulates the RF signal.

  As the recording density of recording data increases in the linear direction, the amplitude decreases as the frequency component becomes higher due to interference. Therefore, the RF signal processing unit 121 performs an equalizer process for lifting the high frequency component. The information signal reproducing unit 14 can perform a process in which the PLL that regenerates the clock from the data is easily locked. Further, the information signal reproducing unit 14 equalizes the reproduced RF signal to a partial response characteristic by an equalizer, performs Viterbi decoding processing, binarizes the reproduced RF signal, and outputs the reproduced signal.

Next, the RF signal will be described. As shown in FIG. 2, the light detection unit 6 includes a four-divided light receiving unit 6-1 for receiving a main beam, sub-beam light receiving units 6-2 and 6-3 disposed therebetween, and respective light receiving units. Photodiodes (A_PD to F_PD) corresponding to the amount of light, and a current-voltage conversion circuit (hereinafter referred to as an IV conversion circuit) that converts a current detected by the photodiode into a voltage. The output of each IV conversion circuit is Ao to Fo. The signals from the four divided areas of the light receiving unit 6-1 are added together to generate an RF (Radio Frequency) signal. Ao + Bo + Co + Do in FIG. 2 is an RF signal.

光学特性を示すMTF(Mutual Transfer Function)特性を図３（ｂ）に示す。光スポットが絞れないのは、MTFのような周波数特性をもつからである。

FIG. 3B shows MTF (Mutual Transfer Function) characteristics indicating optical characteristics. The reason why the light spot cannot be narrowed is that it has frequency characteristics like MTF.

  Usually, in order to sample the channel bit frequency f at the sampling frequency fs, according to the sampling theorem that "in order to sample an analog signal, the frequency higher than twice the maximum frequency must be the sampling frequency" fs needs a frequency twice as high as f. In the case of the MTF characteristic of a code in which the minimum run length is limited to 2 as in the case of 8-16 modulation code used in DVD shown in FIG. , And distributed in a band of approximately 1/4 or less of the channel bit frequency. According to the sampling theorem, demodulation is possible by using a recovered clock having a frequency component that is half the channel bit frequency. For example, since the channel bit frequency of DVD-RAM 16 times speed is 466.88 MHz, sampling should be performed at 233.44 Mhz or more of 1/2.

  The output of the photodetector is connected to the main board by FPC, and when the RF signal becomes high frequency, it was limited by the band of FPC, but it was transmitted to the main board wirelessly, received by the main board, and demodulated By doing so, there is no electrical wiring from the photodetector to the information signal reproduction unit, and it is difficult to be affected by noise. By transmitting a high-frequency RF analog signal to the main board, a highly reliable reproduction signal can be generated.

  In addition, after A / D conversion, since it is converted to a digital value, noise is less likely to appear than an analog value. For this reason, the optical pickup and the main board may be connected by wire instead of flying wirelessly. The influence of high frequency on the inside of the housing by the wireless signal is eliminated.

  Next, a second embodiment of the present invention will be described. In FIG. 4, not only the RF signal but also the signal used for servo adjustment and laser light adjustment is A / D converted, frequency-multiplexed by the frequency multiplexing unit 125, superimposed on the high-frequency carrier, and modulated by the modulation unit 123 This is an embodiment in which modulation is performed and the data is transmitted wirelessly from the transmission unit 124.

  Photodetector and light receiving unit of front monitor, photodetector 6 including current-voltage converter, internal configuration of front monitor 7, A / D converters 122a to 122e obtained by A / D conversion of respective outputs, A / A different clock is used for each of the D conversion sampling clocks, a frequency multiplexing unit 125 that frequency-multiplexes the A / D conversion output, a modulation unit 123 that superimposes the high frequency carrier, and a transmission unit 124 that wirelessly transmits the signal output from the modulation unit 123. Consists of.

  In this embodiment, the data is transmitted wirelessly, but after A / D conversion, it may be preferentially connected to the main board. Since the signal detected by the photodetector is weak, it is A / D converted before being transferred to the main board, and converted to a digital signal, so that it is resistant to noise.

  Next, a third embodiment of the present invention will be described. FIG. 5 shows an embodiment in which an analog signal equalized by the RF signal processing unit 121 is superimposed on a high frequency carrier, modulated by the modulation unit 123, and transmitted wirelessly by the transmission unit 124. The difference from the first embodiment is that the optical pickup unit does not convert it into digital data. By not having an A / D converter in the optical pickup, the number of parts to be mounted on the optical pickup and the size of the parts can be reduced, and the design flexibility on the optical pickup side can be expanded.

  In this embodiment, an A / D converter is provided on the main board side. The RF signal is wirelessly transmitted from the transmission unit 124 with the carrier signal superimposed on the RF signal by the RF signal modulation unit 123. The wirelessly transmitted signal is received by the RF signal receiving unit 10 of the main board unit 9 and the RF signal demodulating unit 11 reproduces an analog RF signal. The analog RF signal is converted from an analog value to a digital value by the A / D converter in the information signal reproducing unit 14 and converted into digital data. As a clock used for A / D conversion, a clock generated by a PLL (not shown) in the information signal reproduction unit 14 is used.

  FIG. 5 also shows the exchange of data between the optical pickup and the main board.

  The temperature data detected by the temperature sensor 2a and the hall element 2b and the magnetic detection signal are transferred to the main board 9 and processed, and used for the operation of the actuator 8.

  The signal obtained by the front monitor light detector 7 detects the amount of laser light, is transferred to the main board 9, and is used for control of the laser controller 15. In the light detection unit 6, signals such as focus and tracking used for controlling the actuator are detected, processed by the main substrate 9, and transferred to the laser control unit 15 of the optical pickup 2 as serial data and a serial clock for laser control. Used for. A write gate signal indicating recording data, a recording clock, and writing is also transferred from the main board 9 to the laser controller 15. These signals are transferred by FPC as usual.

  In order to prevent low-power radio signals with high-frequency superposition from being placed on the FPC and the casing, shields are used except for the radio signal transmitter and the input unit to strengthen the ground and the like. As a shielding method, for example, an electromagnetic shielding paint, a shielding material, or the like is used.

  Further, except for the radio signal transmission unit and the radio signal input unit, a shield plate or the like that does not pass electromagnetic waves is provided between the optical pickup unit and the main board.

  In the above embodiments, DVD and CD discs have been described as examples. However, the scope of the present invention is not limited to DVD, CD discs, etc., and HD DVDs, blu-ray discs, etc. A similar method can be employed in the recording / reproducing apparatus.

The figure which shows the 1st Example of the optical disk apparatus of this invention. The figure which shows the 1st Example of the optical disk apparatus of this invention. Light distribution intensity and MTF characteristics. The figure which shows the 2nd Example of the optical disk apparatus of this invention. The figure which shows the 3rd Example of the optical disk apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Optical disk, 2 ... Optical pick-up part, 3 ... DVD laser, 4 ... CD laser, 5 ... Optical system, 6 ... Light detection part, 7 ... Front monitor light detection part, 8 ... Actuator, 9 ... Main board | substrate, DESCRIPTION OF SYMBOLS 10 ... Signal receiving part, 11 ... RF signal demodulation part, 12 ... Transmission signal production | generation part, 14 ... Information signal reproduction | regeneration part, 16 ... Host computer, 17 ... Control part, 18 ... Recording signal processing part

Claims (6)

An optical disc apparatus for recording or reproducing information on an optical disc,
An optical pickup for irradiating the optical disc with laser light;
Based on the reflected light from the optical disc detected by the optical pickup,
A reproduction signal processing unit that reproduces data recorded on the optical disc, or a main board that includes at least a recording signal processing unit that generates and processes recording data;
The optical pickup receives reflected light from the optical disk, converts light intensity into current by a plurality of photodiodes, converts current into voltage value, and reproduces data recorded on the optical disk by calculation. (Hereinafter referred to as an RF signal) etc.
An RF signal processing unit that corrects a frequency characteristic of an RF signal that is one of the outputs of the light detection unit;
A first A / D converter for converting the output of the RF signal processor from an analog value to a digital value;
With
The optical disc apparatus, wherein the main substrate includes an information signal reproducing unit that processes a digital signal converted into digital data by the first A / D conversion unit. In claim 1,
The optical pickup is
An RF signal modulation unit that superimposes an RF digital signal output from the first A / D conversion unit on a high-frequency carrier;
A transmitter that wirelessly transmits the RF signal modulator;
The main board has a receiver that receives a radio signal transmitted from the transmitter;
An RF digital signal demodulator that demodulates an RF radio signal received by the receiver;
An optical disc apparatus comprising an information signal reproducing unit for processing the digital signal demodulated by the RF digital signal demodulating unit. In claim 2,
A plurality of A / D converters for converting the focus error signal and the tracking error signal, which are one of the outputs of the light detection unit, from analog values to digital values,
A frequency multiplexing unit that frequency-multiplexes the signals A / D converted by the plurality of A / D conversion units;
The optical disk apparatus, wherein the modulation unit modulates a signal frequency-multiplexed by the frequency multiplexing unit. An optical disc apparatus for recording or reproducing information on an optical disc,
An optical pickup for irradiating the optical disc with laser light;
Based on the reflected light from the optical disc detected by the optical pickup,
A reproduction signal processing unit that reproduces data recorded on the optical disc, or a main board that includes at least a recording signal processing unit that generates and processes recording data;
The optical pickup receives reflected light from the optical disc, and converts a light intensity into a current by a plurality of photodiodes, converts a current into a voltage value, and outputs an RF signal or the like by calculation; ,
An RF signal processing unit that corrects the frequency characteristics of the light detection unit output;
An RF signal modulating unit for superimposing the RF signal processing unit output on a high frequency carrier;
A transmitter that wirelessly transmits the RF signal modulator;
The main board has a receiver that receives a radio signal transmitted from the transmitter;
An RF signal demodulator that demodulates an RF radio signal received by the receiver;
A second A / D converter that converts the RF analog signal demodulated by the RF signal demodulator into digital data;
An optical disc apparatus comprising an information signal reproducing unit for processing a signal. 3. The optical disc apparatus according to claim 2, wherein the optical pickup and the main board other than the wireless transmission unit and the wireless reception unit have a shield structure so as not to be affected by electromagnetic waves of the wireless signal. 3. The optical disk apparatus according to claim 2, wherein a space between the optical pickup and the main board is provided with a shield structure so as not to be affected by electromagnetic waves of the radio signal.

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