KR20000043286A - Optical pickup device converging secondary beams - Google Patents

Abstract

PURPOSE: An optical pickup device converging secondary beams is provided to improve playback efficiency and to easily detect an error signal. CONSTITUTION: Laser beam is emitted from a laser diode(10) for being irradiated to a diffractive grate(15). The laser beam is diffracted into three beams. The laser beam is irradiated toward a beam splitter(20) for changing the beam passage. The laser beam is collected on an optical disk(D) by a main beam object lens(32) for being diffracted. The diffracted beam passing through a duplex lens(30) is irradiated to the beam splitter for containing focus error signal by passing through a cylindrical lens unit(25) in the beam splitter. The laser beam passing through the main beam object lens is collected on a main beam detector(40). And, the laser beams passing through first and second auxiliary beam object lenses(34a,34b) are collected on first and second auxiliary beam detectors(42,44).

Description

Optical pickup device capable of secondary light

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup apparatus capable of performing secondary light convergence, and in particular, having a double lens for converging laser light reflected and scattered from an optical disk, thereby increasing the amount of light that is reduced to the photodetector, thereby improving reproduction efficiency and error signals. The present invention relates to an optical pickup apparatus capable of performing sub-light convergence, which can be easily detected.

In general, an optical pickup apparatus is used for condensing and diffracting laser light on a pit of an optical disk on which optical information is recorded to modulate the laser light, and converging the modulated laser light to a photodetector to reproduce the optical information.

As an example of such a conventional optical pickup apparatus, as shown in FIG. 1, a laser diode 100 in which a laser light having a predetermined wavelength is generated, and diffraction of a laser light formed and incident on the laser diode 100 is incident. The collimator which gives parallelism to the diffraction grating 105 which isolate | separates into 0th-order diffraction light and +/- 1st order diffraction light, ie, three beam using the phenomenon, and the laser beam which passed through this diffraction grating 105 A lens 110, a beam splitter 120 for partially reflecting and transmitting the parallel light to separate incident light and reflected light, a wavelength plate 125 for converting the polarization of the laser light transmitted through the beam splitter 120; And an objective lens 130 for condensing the laser light via the wavelength plate 125 on the optical disk D, and the laser light reflected by the beam splitter 120 to the photodetector 150, thereby focusing a signal. It consists of a converging lens unit 140 to give.

In operation of the conventional optical pickup apparatus having such a configuration, first, a laser beam having a predetermined oscillation wavelength is incident on the diffraction grating 105 in the laser diode 100, and the incident laser light passes the diffraction grating 105. Transmitted and separated into 0th and ± 1st light, i.e., three beams. This three-beam is used for focusing and tracking errors, and the linearity is imparted while passing through the collimating lens 110 through the diffraction grating 105. The laser beam that goes straight is incident on the beam splitter 120, and the three beams are reflected and transmitted at a constant rate by the beam splitter 120. The laser beam is transmitted through the beam splitter 120 to the wavelength plate 125, and the laser light is converted into circularly polarized light while passing through the wavelength plate 125. This laser light is collected by the objective lens 130 and irradiated to the pit signal surface on the optical disc D. The laser light is reflected almost as it is in the absence of the pit on the optical disc D and returns to the objective lens 130. Where there is a pit, the laser light is diffracted by the pit and emitted outside the range of the objective lens 130, thereby causing only a part of the incident light to be returned, thereby generating a light quantity difference in the photodetector 150.

The modulated reflected light reflected back from the optical disk D is converted into linearly polarized light which is inverted by 90 ° from the time of incidence while passing through the wave plate 125, so that the light splitter 120 can reflect the light. Is converted. The reflected light of which the optical path is converted is provided with a focus error signal via the converging lens unit 140 and received by the photodetector 150. The converged laser light is converted into an RF (RF), focus and tracking error detection signal by a photodetector, and the converted current is demodulated and reproduced by an original signal by a control circuit (not shown).

However, such a conventional optical pickup apparatus converges only the 0th order diffracted light into the objective lens among the light diffracted upon modulation in the optical disc D and discards the modulated light diffracted by ± 1st order, thereby significantly reducing the light efficiency, thereby reproducing the RF signal. Since the signal is poor, and the tracking and focus error signals are detected in the 0th order diffraction light, the circuit configuration of the error signal detection becomes difficult, thereby deteriorating the reliability of the optical pickup apparatus.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and improves the optical signal deteriorated during modulation on an optical disc to improve the reproduction signal, and receives the modulated light diffracted out of the lens range to improve the detection amount of the reproduction signal. SUMMARY OF THE INVENTION An object of the present invention is to provide an optical pickup apparatus capable of easily detecting a sub-light.

The present invention for achieving the above object, the primary light objective for converging the zero-order diffraction light diffracted in the optical disk, and the secondary light objective to be integrally formed on both sides of the main light objective lens to converge ± 1 light A double lens configured; A main light detector configured to collect the laser light converged by the main light objective lens and convert it into a current signal; and a plurality of photo detectors configured to collect the laser light converged by the sub-light objective lens and convert the laser light into a current signal. This is achieved by providing an optical pickup apparatus capable of performing sub-light convergence.

1 is a block diagram of a conventional optical pickup device;

2 is a block diagram of an optical pickup apparatus according to an embodiment of the present invention.

<Explanation of symbols for main parts of drawing>

10: laser diode 15: diffraction grating

20 beam splitter 25 cylindrical lens portion

30: double lens 32: daylight objective lens

34a: First secondary light objective 34b: Second secondary light objective

40: daylight detector 42: the first light detector

44: second light detector

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

According to the present invention, as shown in FIG. 2, the laser diode 10 emitting the laser light and the laser light emitted from the laser diode 10 are separated into a three-beam beam which is 0-order light and ± 1-order light for error detection. A diffraction grating (15) to be made, a beam splitter (20) for reflecting the laser light passing through the diffraction grating (15) and converting the path toward the optical disk (D) side, and a laser light passing through the beam splitter (20). A double lens 30 condensing on the optical disc D and simultaneously converging the multi-diffraction light diffracted on the optical disc D, and a plurality of photodetectors 40 and 42 on which the laser light converged on the double lens 30 is collected. 44).

The double lens 30 is integrally formed at both sides of the main light objective lens 32 for converging the zero-order diffracted light diffracted by the optical disk D, and converges ± 1 order light on both sides of the main light objective lens 32. It consists of a 1st sub-light objective 34a and a 2nd sub-light objective 34b.

The photodetectors 40, 42, and 44 may include a main light detector 40 for collecting the laser light converged by the main light objective lens 32 and converting the laser light into a current signal, the first sub-light objective 34a, and The laser beam converged by the second secondary light objective lens 34b is composed of a first sub-light detector 42 and a second sub-light detector 44 for condensing and converting the laser light into a current signal.

On the other hand, on the bottom surface of the beam splitter 20 is formed a cylindrical lens portion 25 for generating astigmatism in the laser light converged by the photodetectors 40, 42, 44. Thus, in the optical system, since the astigmatism method is used as the focus error detection and the three beam method is used as the tracking error detection, the six detectors can be used as the photodetectors 40, 42 and 44.

Next will be described the operation of the present invention made as described above.

First, laser light of a predetermined wavelength is emitted from the laser diode 10 and irradiated to the diffraction grating 15, and the laser light is diffracted by the diffraction grating 15 into three beams of zero order light and ± 1 order light. When the three-beams form an optical spot on the optical disk D, the three-beams are spotted on the tracks as the negative beams of +1 order light and the negative beams of -1 order light on the basis of the main beam which is the 0th order light, so that the tracking error signal is detected by the respective light quantity difference. Be sure to Therefore, these three beams are light that can converge to the main light detector while sharing the optical axis with the main beam both upon diffraction in the optical disk D. FIG.

As described above, the laser beam separated into the three beams by the diffraction grating 15 is irradiated from the diffraction grating 15 to the beam splitter 20, and the three beams are converted into the optical path by the beam splitter 20. Such a change of the optical path is reflected and transmitted at a constant rate according to the oblique plane treatment of the beam splitter 20, and the laser light reflected from the oblique plane is irradiated toward the double lens 30 side.

As described above, the laser light passing through the beam splitter 20 is focused on the optical disk D by the main light objective lens 32 formed at the center of the double lens 30, and the focused laser light is fit into the optical disk D. It is modulated according to the presence and absence of diffraction.

The laser light modulated in this way is diffracted and scattered by multi-order diffracted light such as 0th, ± 1st, ± 2nd, .. etc., and this diffraction order is accompanied by the same amount of modulation of light. Since it is distributed and scattered by the number of procedures, optical information is accompanied by diffracted light in which all of the multiple diffraction lights are individually modulated.

In this laser beam, the amount of incident incident light back to the main light objective lens 32, where only the zeroth order diffracted light is returned, is about 30%. When the other ± diffraction light is returned and reduced, the amount of diffracted light is increased to reduce When amplifying, the amount of light can be amplified even with a small amount of input, and the noise ratio is reduced by the amount of light to be reduced, thereby improving the S / N ratio, thereby improving the reproduction of optical information.

Of the laser light diffracted as described above, the zero-order diffraction light is again irradiated onto the main light objective lens 32, and the ± first order diffraction light is formed on both sides of the main light objective lens 32. And the second secondary light objective 34b. This is because the + 1st diffraction light and the −1st diffraction light are symmetrically diffracted around the 0th diffraction light, so that the first sub-light objective 34a and the symmetrically formed on both sides of the main light objective lens 32 are formed. Each of the two secondary light objective lenses 34b is irradiated.

As described above, the multi-diffraction light passing through the double lens 30 is irradiated to the beam splitter 20, and the laser beam passes through the cylindrical lens portion 25 of the beam splitter 20 while the focus error signal is received. Is given.

As described above, the laser light passing through the main light objective lens 32 of the laser light passing through the beam splitter 20 is received by the main light detector 40 and at the same time, the laser light passing through the first sub-light objective 34a is removed. The laser light, which is irradiated to the first sub-light detector 42 and passes through the second sub-light objective 34b, is received by the second sub-light detector 44, respectively.

Therefore, the RF signal converted from the RF signal converted into the electrical signal in the main light detector 40 is converted into the electrical signal in the first and second sub-detector 42 and 44, and a single signal is calculated from the calculated signal. RF signal is output.

In addition, the tracking error signal and the focus error signal can be individually output from the laser light converged on the first and second sub-detectors 42 together with the output of the RF signal.

As described above, the present invention recondenses the laser light that is diffracted and scattered by ± 1 order out of the laser light that is collected and scattered from the optical disk D, and then reduced to the first and second negative light detectors 42 and 44 to provide an electrical signal. Since the amount of light to be reduced is increased to reduce the signal amplification ratio, the reproduction of optical information is improved, and the photodetectors 40, 42, and 44 are separately provided for each converging light. To improve.

In the present invention, the optical pickup apparatus capable of sub-light convergence reduces the laser light scattered according to whether the optical information accompanies and condenses the light through a separate lens unit, thereby increasing the amount of converged light, thereby increasing the reproduction efficiency of the optical pickup device. Each laser beam is received by the plurality of photodetectors, thereby making it easy to detect an error signal, thereby improving the reliability of the optical pickup apparatus.

Claims (1)

In the optical pickup device, A primary light objective lens 32 for converging the zero-order diffracted light diffracted by the optical disk D, and a secondary light objective lens 34 which is integrally formed on both sides of the main light objective lens 32 to converge ± 1 primary light A configured double lens 30; And A primary light detector 40 which is reflected by the optical disk D and is focused on the zeroth order diffracted light via the double lens 30 and is converted into a current signal, and the first order diffracted light is focused and converted into a current signal An optical pickup apparatus capable of sub-light convergence, characterized in that consisting of a negative light detector (42,44).