JP4549583B2 - Optical pickup, optical disc apparatus, and information processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical pickup used for recording / reproducing or erasing information on / from an optical disc, an optical disc apparatus using the optical pickup, and an information processing apparatus using them.
[0002]
[Prior art]
Optical memory technology using optical disks with pit-like patterns as high-density and large-capacity storage media has been put into practical use while expanding applications with digital audio disks, video disks, document file disks, and data files. . In recent years, high-density optical discs using a visible red laser having a wavelength of 630 nm to 670 nm as a light source, such as DVD-ROM, are becoming popular. In addition, high-density recordable optical disks (DVD-RAM) have been commercialized, and large-capacity digital data can be easily recorded on optical disks. In addition, CD-Rs having high compatibility with already widely used CDs have been widely used.
[0003]
In view of the above background, in a DVD information reproducing apparatus, it is important to reproduce DVD-RAM and CD-R in addition to DVD-ROM and CD. In the information recording / reproducing apparatus for DVD, in addition to the recording / reproducing function for DVD-RAM, reproduction of DVD-ROM, CD and CD-R is important.
[0004]
CD-R records and reproduces information using changes in the reflectance of the dye, but it is optimized for wavelengths around 800 nm, so it cannot reproduce signals at other wavelengths such as visible light. There is. Therefore, in order to reproduce the CD-R, it is desirable to use an infrared light source having a wavelength of about 800 nm. An optical pickup including a red semiconductor laser for DVD and an infrared semiconductor laser for CD and CD-R is provided. Has been developed. In order to simplify the optical system, and to realize a reduction in size and cost, it has been proposed to integrate the semiconductor lasers of the two types of wavelengths in one package.
[0005]
The optical pickup disclosed in Japanese Patent Laid-Open No. 10-289468 will be described with reference to FIGS. FIG. 20 is a schematic configuration diagram of the optical pickup 200. Assuming that the optical disk 7 is recorded / reproduced by using a plurality of types of transparent substrates 220 having different thicknesses. Here, recording / reproduction refers to recording information on the information recording surface 240 of the optical disc 7 or reproducing information on the information recording surface 240. In the conventional optical pickup device 200, as a light source, a first semiconductor laser 100a (wavelength λ = 610 nm to 670 nm) as a first light source and a second semiconductor laser 100b (wavelength λ = 740 nm to 830 nm) as a second light source are used. have. The first semiconductor laser 100a is a light source used for DVD recording / reproduction, and the second semiconductor laser 100b is a light source used for recording / reproduction of the second optical disk. These semiconductor lasers are properly used according to the optical disk to be recorded / reproduced.
[0006]
The synthesizing unit 210 synthesizes the light beam emitted from the first semiconductor laser 100a and the light beam emitted from the second semiconductor laser 100b, and condenses it on the optical disc 7 through one condensing optical system described later. In addition, the optical path is the same (may be substantially the same) optical path. A polarizing prism (birefringent plate) is used as the synthesizing unit 210, and the light beam emitted from the first semiconductor laser 100a is passed as an ordinary ray without changing the optical path, and the light beam emitted from the second semiconductor laser 100b is The optical path is changed as an extraordinary ray. As the combining means 210, a hologram may be used.
[0007]
The condensing optical system composed of the objective lens 60 and the collimating lens 50 is means for condensing the light beam emitted from the semiconductor laser onto the information recording surface 240 via the transparent substrate 220 of the optical disc 7 to form a spot. is there. The diaphragm 150 limits the luminous flux to a predetermined numerical aperture.
[0008]
The unit 160 includes a hologram 40, a photodetector 800, and the like in addition to the first semiconductor laser 100a and the second semiconductor laser 100b, the details of which are shown in FIG. In the unit 160, the first semiconductor laser 100a, the second semiconductor laser 100b, and the photodetector 800 are arranged on the same plane. An additional photodetector 230 is provided for detecting the back light of the semiconductor laser. The photodetector 230 uses an APC (auto power control) circuit to determine the amount of light emitted from the semiconductor laser so that the amount of light emitted from the semiconductor laser becomes a predetermined amount. Used for current control.
[0009]
The focus error signal is detected by the knife edge method. Therefore, eight light receiving elements (light receiving surfaces) A1 to D1 and A2 to D2 are provided on the light receiving surface of the light detection means 800. Further, the hologram 40 is used as the light branching means, and the hologram element is divided into four as A to D, and the light beams that have passed through the respective divided surfaces are arranged so as to form an image on the light receiving surface of the light detecting means 800. Yes.
[0010]
Similarly, for the purpose of realizing a small optical pickup capable of recording / reproducing DVD, CD and CD-R, a configuration in which a photodetector and two semiconductor laser chips having different wavelengths are accommodated in one unit. In addition to the above-mentioned JP-A-10-289468, JP-A-10-319318, JP-A-10-21577, JP-A-10-64107, JP-A-10-321961, and JP-A-10-134388. JP-A-10-149559, JP-A-10-241189, JP-A-1998-124918, JP-A-9-120568, JP-A-2000-11417, and the like.
[0011]
[Problems to be solved by the invention]
Within the DVD category, there are DVD-RAMs in addition to DVD-ROMs. Therefore, it is desirable that a DVD recording or reproducing apparatus can reproduce DVD-ROM, DVD-RAM, and CD-ROM and CD-R (CD-RECORDABLE), which are already widely used optical disks. Each of these optical discs has a standard, and a tracking error (TE) signal detection method capable of stably reproducing a signal is defined.
[0012]
The TE signal of the DVD-ROM is obtained by the phase difference method. The phase difference method is also called a differential phase detection (DPD) method. A TE signal can be obtained with one beam by using the intensity change of the far field pattern (FFP) reflected and diffracted from the optical disk. This is a method that utilizes a change in diffracted light by a two-dimensional arrangement of pits. A TE signal is obtained by detecting a change in the light amount distribution in diffraction due to the pit row by a quadrant photodetector and comparing the phase. This method is suitable for a read-only disc having a pit row.
[0013]
The TE signal of DVD-RAM is obtained by the push-pull (PP) method. The PP method is mainly used for write-once and rewritable optical disks. When the convergence spot is irradiated onto the guide groove on the optical disk recording surface, the reflected light is accompanied by diffracted light in a direction perpendicular to the extending direction of the guide groove. The FFP that has returned to the objective lens surface has a light intensity distribution due to the interference between the ± 1st order diffracted light and the 0th order diffracted light in the guide groove. Depending on the positional relationship between the guide groove and the convergence spot, one part is bright and the other part is dark or vice versa. By detecting such a change in light intensity with a two-divided photodetector, a TE signal of the PP method can be obtained.
[0014]
According to the standard, a TE signal can be obtained by CD-ROM (including audio CD) and CD-R by the PP method, but the TE signal intensity is smaller than that of DVD-RAM. Further, the PP method has a problem that a TE signal offset occurs due to lens shift. In the DVD-RAM, the offset correction section of the TE signal is provided on a part of the information recording surface for this problem, whereas in the CD-ROM and CD-R, such measures are taken on the optical disk. It is not done. Therefore, the 3-beam method is often used as the TE signal detection method.
[0015]
In the three-beam method, a diffraction grating is inserted in the forward path from the light source to the optical disc, and zero-order diffracted light (main beam) and ± 1st-order diffracted light (sub beam) of the diffraction grating are formed on the optical disc. When the main beam deviates from the track center, one of the sub beams approaches the track center and the other moves away from the track center, so that the amount of reflected return light can be different. The TE signal is obtained by detecting this difference.
[0016]
Thus, in order to record or reproduce DVD-ROM, DVD-RAM, CD-ROM, and CD-R, it is necessary to perform three types of TE signal detection methods: phase difference method, PP method, and three-beam method. There is. However, in the conventional example, there is no example of a specific configuration that can cope with all of the three types of TE signal detection methods such as the phase difference method, the PP method, and the three beam method.
[0017]
Also, the thickness of the transparent substrate that covers the information recording surface differs between DVD and CD. The standard substrate thickness for DVD is 0.6 mm, and the standard substrate thickness for CD is 1.2 mm. In this way, when light is converged on optical disks having different substrate thicknesses by a common condensing optical system, a symmetrical aberration occurs at the optical axis center called spherical aberration. Many methods for overcoming this aberration and recording / reproducing DVD and CD with a common condensing optical system have been proposed. Furthermore, DVD has a higher recording density than CD, and even if a short-wavelength red laser light source is used, the aperture diameter (NA) of the objective lens requires 0.6, which is larger than 0.45 used for CD. To do. A conventional example such as Japanese Patent Laid-Open No. 10-289468 also discloses a configuration in which the aperture 150 is used to further reduce the NA during CD reproduction.
[0018]
As described above, the CD and the DVD perform information reproduction under optical conditions that are remarkably different in the three items of the base material thickness, the light source wavelength, and the NA. Therefore, as in the conventional example, in the configuration in which the FE signal is detected from the common light receiving divided area during the reproduction of the CD and the DVD, the generation of the FE signal offset and the FE signal amplitude are caused by the difference in the optical characteristics of the three items. There is a problem that characteristic deterioration such as deterioration of (signal strength) occurs.
[0019]
Further, as shown in Japanese Patent Laid-Open No. 9-120568, as shown in FIG. 22 (FIG. 5A of Japanese Patent Laid-Open No. 9-120568), diffracted light (112E) incident on different positions on the photodetector due to the difference in wavelength. And 113E) are configured to receive light by a continuous photodetector region (for example, 800D), the area of each photodetector region is increased, the electrical capacity of the photodetector region is increased, and high-frequency signal detection is performed. This makes it difficult to perform high-speed signal reproduction.
[0020]
Further, on the premise of the difference in wavelength and the position of the light emitting point, a suitable configuration for obtaining a good signal for both DVD and CD playback has not been studied.
[0021]
[Means for Solving the Problems]
In order to solve the above-described conventional problems, the first optical pickup of the present invention includes a first semiconductor laser light source that emits a light beam having a wavelength λ1 and a second semiconductor beam that emits a light beam having a wavelength λ2. A semiconductor laser light source, a condensing optical system that receives light beams emitted from the first and second semiconductor laser light sources and converges them onto a small spot on the optical disk, and a diffractive means that diffracts the light beam reflected by the optical disk And an optical pickup comprising a light detector that receives each diffracted light diffracted by the diffracting means and outputs an electrical signal according to the amount of light,
The photodetection unit includes a photodetection unit PD0 that receives + 1st order diffracted light from the diffracting means, and a distance between the center of the photodetection unit PD0 and each light emitting point of the first and second semiconductor laser light sources. Are d1 and d2, respectively.
λ1 / λ2 = d1 / d2
The above relationship is substantially satisfied. According to the optical pickup as described above, the light detection unit can be used in common for both wavelengths, and the number of light detection units can be reduced. Accordingly, it is possible to realize a reduction in cost and a reduction in size due to a reduction in the area of the photodetector, a reduction in the number of circuit elements for converting the output into a current voltage.
[0022]
The second optical pickup of the present invention includes a first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2, and the first and second light sources. A condensing optical system that receives a light beam emitted from a semiconductor laser light source and converges it onto a small spot on an optical disk, a diffracting means that diffracts the light beam reflected by the optical disk, and a diffracted light diffracted by the diffracting means. And an optical pickup that outputs an electrical signal in accordance with the amount of light, wherein the optical detection unit includes a photodetection unit PD0 that receives + 1st order diffracted light from the diffracting means, and the optical detection unit The distance between the center of the part PD0 and the light emitting points of the first and second semiconductor laser light sources is d1 and d2, respectively, and the distance between the light emitting points of the first and second semiconductor laser light sources is When d12
d2 = d1 + d12
Satisfying the relationship
d1 = λ1 · d12 / (λ2-λ1)
d2 = λ2 · d12 / (λ2-λ1)
The above relationship is substantially satisfied. According to the optical pickup as described above, the light detector can be used in common for both wavelengths for a predetermined distance between light emitting points and wavelengths, and the number of light detectors can be reduced. The cost can be reduced and the size can be reduced by reducing the number of circuit elements for converting the output to current-voltage.
[0023]
The third optical pickup of the present invention includes a first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2, and the first and second light sources. A condensing optical system that receives a light beam emitted from a semiconductor laser light source and converges it onto a small spot on an optical disk, a diffracting means that diffracts the light beam reflected by the optical disk, and a diffracted light diffracted by the diffracting means. An optical pickup that outputs an electrical signal according to the amount of light, wherein the light detection unit--of the light beam having the wavelength λ1 among the diffracted light diffracted by the diffraction means A light detection unit PD1 that receives the first-order diffracted light; and a light detection unit PD2 that receives the −1st-order diffracted light of the light beam having the wavelength λ2. The light detection unit PD1 and the light detection unit PD2 each include It has been divided into a number of regions,
When information reproduction is performed using the light of the wavelength λ1, a focus error signal is detected by calculating a signal obtained from each region of the light detection unit PD1, and information reproduction is performed using the light of the wavelength λ2. A focus error signal is detected by calculating a signal obtained from each of the regions of the light detection unit PD2.
[0024]
According to the optical pickup as described above, since it has a light detection unit corresponding to each wavelength of the light source, different types of optical disks corresponding to each wavelength, for example, DVD (DVD-ROM, DVD-RAM), and Even when any one of CDs (CD-ROM, CD-R) is recorded or reproduced, the characteristic deterioration of the focus error signal can be prevented. Since each region is divided into a plurality of regions, a focus error signal can be obtained by differentially calculating the magnitude of the diffracted light in each divided region.
[0025]
In the third optical pickup of the present invention, it is preferable that the shapes of the light detection part PD1 and the light detection part PD2 are different. According to the optical pickup as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0026]
In addition, the light detection unit PD1 and the light detection unit PD2 are each divided into a plurality of regions by dividing lines, and a symmetrical center line parallel to the dividing line of the light detection unit PD2 and the light detection unit PD1. It is preferable that the symmetrical center line parallel to the dividing line is shifted in a direction orthogonal to the respective symmetrical center lines. According to the optical pickup as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0027]
A fourth optical pickup of the present invention includes a first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2, and the first and second light sources. A condensing optical system that receives a light beam emitted from a semiconductor laser light source and converges it onto a small spot on an optical disk, a diffracting means that diffracts the light beam reflected by the optical disk, and a diffracted light diffracted by the diffracting means. An optical pickup that outputs an electrical signal according to the amount of light, wherein the light detection unit--of the light beam having the wavelength λ1 among the diffracted light diffracted by the diffraction means A light detection unit PD1 that receives the first-order diffracted light; and a light detection unit PD2 that receives the −1st-order diffracted light of the light beam having the wavelength λ2. The center of the light detection unit PD1 and the first semiconductor laser The distance between the light emitting point sources d1, the distance between the light emitting point of the the center of the photo detecting portion PD2 second semiconductor laser light source when the d2,
λ1 / λ2 = d1 / d2
The above relationship is substantially satisfied. Since the optical pickup as described above has the light detection parts PD1 and PD2 corresponding to the respective wavelengths of the light source, the light detection parts PD1 and PD2 are provided with focus errors of different types of optical disks corresponding to the respective wavelengths. It can be used as a signal detector.
[0028]
In the fourth optical pickup of the present invention, when the distance between the light emitting points of the first and second semiconductor laser light sources is d12, the distance between the center of the light detector PD1 and the center of the light detector PD2. Is preferably approximately twice as large as d12. According to the optical pickup as described above, the center of each light detection unit and the center of the diffracted light can coincide with each other, and even if there is an error such as a wavelength variation, light can be received without any exception.
[0029]
In addition, the light detection unit PD1 and the light detection unit PD2 are each divided into a plurality of regions, and when information is reproduced using light of the wavelength λ1, signals obtained from the regions of the light detection unit PD1 are used. It is preferable to detect a focus error signal by calculating and detecting a focus error signal by calculating a signal obtained from each region of the light detection unit PD2 when information is reproduced using light having the wavelength λ2. According to the optical pickup as described above, since the focus error signal is detected by the light detection unit corresponding to each wavelength of the light source, the characteristic deterioration of the focus error signal can be prevented. Since each region is divided into a plurality of regions, a focus error signal can be obtained by differentially calculating the magnitude of the diffracted light in each divided region.
[0030]
Moreover, it is preferable that the light detection part PD1 and the light detection part PD2 have different shapes. According to the optical pickup as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0031]
In addition, the light detection unit PD1 and the light detection unit PD2 are each divided into a plurality of regions by dividing lines, and a symmetrical center line parallel to the dividing line of the light detection unit PD2 and the light detection unit PD1. It is preferable that the symmetrical center line parallel to the dividing line is shifted in a direction orthogonal to the respective symmetrical center lines.
[0032]
The fifth optical pickup of the present invention includes a first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2, and the first and second light sources. A condensing optical system that receives a light beam emitted from a semiconductor laser light source and converges it onto a small spot on an optical disk, a diffracting means that diffracts the light beam reflected by the optical disk, and a diffracted light diffracted by the diffracting means. An optical pickup that outputs an electrical signal according to the amount of light, wherein the light detection unit--of the light beam having the wavelength λ1 among the diffracted light diffracted by the diffraction means A light detector PD1 that receives the first-order diffracted light, a light detector PD2 that receives the -1st-order diffracted light of the light beam having the wavelength λ2, and a + 1st-order diffracted light of the light beams having the wavelengths λ1 and λ2. Characterized in that it comprises a detection unit PD0. According to the optical pickup as described above, the optical detector PD0 corresponding to both wavelengths and the photodetectors PD1 and PD2 corresponding to each wavelength are provided. The commonly used light detection unit PD0 can be used as a tracking error signal information signal detection unit, and the light detection units PD1 and PD2 can be used as focus error signal detection units for different types of optical disks corresponding to respective wavelengths.
[0033]
In the fifth optical pickup of the present invention, the distances between the center of the light detection unit PD0 and the light emitting points of the first and second semiconductor laser light sources are d1, d2, and the first and second, respectively. When the distance between the emission points of the second semiconductor laser light source is d12,
The distance between the center of the light detector PD1 and the light emitting point of the first semiconductor laser light source is d1, and the distance between the center of the light detector PD2 and the light emitting point of the second semiconductor laser light source is d2,
λ1 / λ2 = d1 / d2
Substantially satisfying the relationship
d2 = d1 + d12,
Satisfying the relationship
d1 = λ1 · d12 / (λ2-λ1)
d2 = λ2 · d12 / (λ2-λ1)
It is preferable that the above relationship is substantially satisfied. According to the optical pickup as described above, the light detection unit can be used in common for both wavelengths, and the number of light detection units can be reduced. When λ1 is shorter than λ2, the first semiconductor laser light source, the second semiconductor laser light source, the light detection part PD1, and the light detection part PD2 are arranged in the direction orthogonal to the optical axis in this order to reduce d1. However, the length of the light detection unit can be secured, and the light detector can be downsized.
[0034]
The light detection unit PD1, the light detection unit PD2, and the light detection unit PD0 are each divided into a plurality of regions. When information is reproduced using the light of the wavelength λ1, the light detection unit PD1 A signal obtained from each region is calculated to detect a focus error signal. When information is reproduced using light having the wavelength λ2, a signal obtained from each region of the light detection unit PD2 is calculated to obtain a focus error signal. It is preferable that a tracking error signal is detected by detecting and calculating a signal obtained from each region of the light detection unit PD0.
[0035]
According to the optical pickup as described above, since the focus error signal is detected by the light detection unit corresponding to each wavelength of the light source, the characteristic deterioration of the focus error signal can be prevented. In addition, since it has a photodetection unit PD0 that detects a dedicated tracking error signal divided into a plurality of regions, all three types of TE signal detection methods such as phase difference method, PP method, and three beam method are used. Yes.
[0036]
In addition, the light detection unit PD1 and the light detection unit PD2 are each divided into a plurality of regions, and when information is reproduced using light of the wavelength λ1, signals obtained from the regions of the light detection unit PD1 are used. The focus error signal is detected by calculation, and when the information is reproduced using the light of the wavelength λ2, the focus error signal is detected by calculating the signal obtained from each area of the light detection unit PD2.
It is preferable that the shapes of the light detection part PD1 and the light detection part PD2 are different. According to the optical pickup as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0037]
The light detector PD1 and the light detector PD2 are each divided into a plurality of regions by dividing lines. When information is reproduced using the light of the wavelength λ1, the light detector PD1 and the light detector PD2 are obtained from each region of the light detector PD1. A focus error signal is detected by calculating the obtained signal, and when performing information reproduction using the light of the wavelength λ2, the focus error signal is detected by calculating a signal obtained from each region of the light detection unit PD2,
The symmetrical center line parallel to the dividing line of the light detection unit PD2 and the symmetrical center line parallel to the dividing line of the light detection unit PD1 are shifted in a direction orthogonal to the respective symmetry center lines. preferable. According to the optical pickup as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0038]
A sixth optical pickup of the present invention includes a first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2, and the first and second light sources. A condensing optical system that receives a light beam emitted from a semiconductor laser light source and converges it onto a small spot on an optical disk, a diffracting means that diffracts the light beam reflected by the optical disk, and a diffracted light diffracted by the diffracting means. And an optical pickup that outputs an electrical signal in accordance with the amount of light, wherein the optical detector is diffracted light of the beam of wavelength λ1 among the diffracted light diffracted by the diffracting means. A light detector PD1 that receives the diffracted light of the light beam having the wavelength λ2, and a light detector PD0 that receives the diffracted light of the light beams having the wavelengths λ1 and λ2. ,
When information reproduction is performed using the light of the wavelength λ1, a signal obtained from the light detection unit PD1 is calculated to detect a focus error signal, and when information reproduction is performed using the light of the wavelength λ2, the light detection unit A focus error signal is detected by calculating a signal obtained from PD2, and a tracking error signal is detected by calculating a signal obtained from the light detection unit PD0.
[0039]
In the first to sixth optical pickups, it is preferable that the first semiconductor laser light source and the second semiconductor laser light source are monolithically formed on one semiconductor chip. According to the optical pickup as described above, the number of assembling steps can be reduced, and the distance between the light emitting points of the two light sources can be determined accurately.
[0040]
In addition, when the wavelength λ1 is in the range of wavelengths 610 nm to 670 nm and the wavelength λ2 is in the range of 740 nm to 830 nm, the main beam and ±± are received by receiving the light beam of the wavelength λ2 emitted from the second semiconductor laser light source. A diffraction grating that forms a secondary beam that is first-order diffracted light;
The diffraction grating has a substantially rectangular cross-sectional shape and has concave and convex portions, and the concave and convex portions have substantially the same width. When the refractive index of the diffraction grating material for the wavelength λ1 is n1, the concave portion has a cross-sectional shape. And the step h of the convex part,
h = λ1 / (n1-1)
It is preferable that the optical path difference between the concave portion and the convex portion is set to be one wavelength with respect to the light having the wavelength λ2. According to the optical pickup as described above, the phase difference due to the optical path difference becomes 2π. By design, the light beam having the wavelength λ1 is not diffracted by the diffraction grating, and light can be used effectively without loss of light quantity. In the case of a light beam with a wavelength λ2, the wavelength is longer than the wavelength λ1, so the optical path difference caused by the step h is smaller than one wavelength and the phase difference is smaller than 2π, so that diffraction occurs and a secondary spot can be generated. become.
[0041]
In addition, regarding both the light beam having the wavelength λ1 and the light beam having the wavelength λ2, the light beam that is not diffracted by the diffraction grating and is incident on the objective lens that constitutes the light collecting system is an NA required for reproducing the optical disk. It is preferable to form lattice fringes over the entire range that satisfies the above.
[0042]
Further, it is preferable that the wavelength λ1 is smaller than the wavelength λ2, and the light emitting point of the first semiconductor laser light source is disposed on the substantially optical axis of the condensing optical system. According to the optical pickup as described above, the laser light from the short wavelength laser element that is easily affected by the lens aberration passes through the vicinity of the optical axis of the condensing optical system having a small degree of lens aberration. Occurrence of aberration can be effectively prevented.
[0043]
Moreover, it is preferable that the diffraction means has a focus error offset reduction region. According to the optical pickup as described above, the focus offset can be suppressed, and a stable and accurate focus servo operation can be realized. Further, if a plurality of focus error offset reduction regions corresponding to both the light beams of λ1 and λ2 are provided in the diffractive means, the focus error offset can be suppressed when the light beams of both λ1 and λ2 are emitted.
[0044]
Next, an optical disc apparatus according to the present invention is characterized by comprising any one of the first to sixth optical pickups, a moving means for the optical pickup, and a rotating means for rotating the optical disc.
[0045]
Next, the optical disc type recognition method of the present invention is an optical disc type recognition method for discriminating whether an optical disc is present in an optical disc apparatus and whether the existing optical disc is a CD or a DVD,
When an optical disk device having an optical pickup using an infrared light source and a red light source is used and the optical disk device is turned on, or when an optical disk is newly installed in the optical disk device, the red A light source of external light is emitted, the presence or absence of the optical disk is determined using an infrared light beam, and when the optical disk is present, the type of the optical disk is determined using reflected light from the optical disk. Features. According to the optical disc type recognition method as described above, it is possible to prevent unnecessary writing or erasing information accidentally even if the optical disc loaded is an optical disc for infrared light such as a CD-R. it can.
[0046]
Next, the optical disc recording / reproducing method of the present invention emits infrared light as it is when it is determined that the inserted optical disc is a CD as a result of discriminating the optical disc type by the optical disc type recognition method of the present invention. Then, the process proceeds to information recording or reproduction, and if it is determined that the inserted optical disk is a DVD, the infrared light is extinguished and the red light is turned on to record or reproduce the DVD. To do.
[0047]
Next, an information processing apparatus according to the present invention includes an optical disc device that records or reproduces information on or from an optical disc, and image information reading means that reads image information of a document,
The image information read by the image information reading means can be recorded on the optical disc apparatus.
[0048]
The information processing apparatus further includes information copying means. At least the image information read by the image information reading means is copied by the copying means, and the image information recorded on the optical disk device is copied. It is preferable that any of the above-mentioned copying is possible.
[0049]
Next, the video projection apparatus of the present invention is characterized by including video projection means for projecting an image on a windshield of an automobile.
[0050]
Preferably, the video projection device further includes an optical disc device that records or reproduces information on the optical disc or performs recording and reproduction, and projects the information reproduced from the optical disc device onto the windshield. .
[0051]
It is preferable that a conversion circuit that converts information reproduced from the optical disk device into an image that matches the curvature of the windshield is provided, and information output from the conversion circuit is projected onto the windshield. According to the image projection apparatus as described above, image distortion due to the curvature of the windshield can be prevented.
[0052]
Next, a first semiconductor laser device of the present invention includes a first semiconductor laser light source that emits a light beam with a wavelength λ1, a second semiconductor laser light source that emits a light beam with a wavelength λ2, and a light beam. A semiconductor laser device comprising a light detection unit that receives and outputs an electrical signal according to the amount of light,
When the distance between the center of the light detection unit PD0 included in the light detection unit and the light emitting points of the first and second semiconductor laser light sources is d1 and d2, respectively.
λ1 / λ2 = d1 / d2
The above relationship is substantially satisfied. According to the semiconductor laser device as described above, the photodetection unit can be used in common for both wavelengths, and the number of photodetection units can be reduced. Accordingly, it is possible to realize a reduction in cost and a reduction in size due to a reduction in the area of the photodetector, a reduction in the number of circuit elements for converting the output into a current voltage.
[0053]
A second semiconductor laser device according to the present invention includes a first semiconductor laser light source that emits a light beam with a wavelength λ1, a second semiconductor laser light source that emits a light beam with a wavelength λ2, A semiconductor laser device comprising a light detection unit that outputs an electrical signal according to the amount of light,
The distances between the center of the light detection unit PD0 included in the light detection unit and the light emitting points of the first and second semiconductor laser light sources are d1 and d2, respectively, and the first and second semiconductors When the distance between the light emitting points of the laser light source is d12,
d2 = d1 + d12
Satisfying the relationship
d1 = λ1 · d12 / (λ2-λ1)
d2 = λ2 · d12 / (λ2-λ1)
The above relationship is substantially satisfied. According to the semiconductor laser device as described above, the photodetector can be used in common for both wavelengths for a predetermined distance between the emission points and wavelengths, and the number of photodetectors can be reduced. Cost reduction and downsizing can be realized by reducing the area and the number of circuit elements for converting the output to current-voltage.
[0054]
In the first or second semiconductor laser device, the light detection unit includes a light detection unit PD1 that receives light having the wavelength λ1 and a light detection unit PD2 that receives light having the wavelength λ2. The light detection part PD1 and the light detection part PD2 are each divided into a plurality of regions, and the light detection part PD1 and the light detection part PD2 are preferably different in shape. According to the semiconductor laser device as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0055]
In addition, the light detection unit includes a light detection unit PD1 that receives light of wavelength λ1 and a light detection unit PD2 that receives light of wavelength λ2, and the light detection unit PD1 and the light detection unit PD2 respectively A symmetric center line parallel to the dividing line of the light detection unit PD2 and a symmetric center line parallel to the dividing line of the light detection unit PD1 are divided into a plurality of regions by dividing lines. It is preferable that they are shifted in a direction perpendicular to the center line. According to the semiconductor laser device as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0056]
A third semiconductor laser device according to the present invention includes a first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2, and a light beam that is received. A semiconductor laser device comprising a light detection unit that outputs an electrical signal according to the amount of light,
The photodetection unit includes a photodetection unit PD1 that receives light with the wavelength λ1 and a photodetection unit PD2 that receives light with the wavelength λ2, and the center of the photodetection unit PD1 and the first semiconductor laser When the distance between the light emitting point of the light source is d1, and the distance between the center of the light detection unit PD2 and the light emitting point of the second semiconductor laser light source is d2,
λ1 / λ2 = d1 / d2
The above relationship is substantially satisfied. According to the semiconductor laser device as described above, since the light detection portions PD1 and PD2 corresponding to the respective wavelengths of the light source are provided, the light detection portions PD1 and PD2 are focused on different types of optical disks corresponding to the respective wavelengths. It can be used as an error signal or tracking error signal detector.
[0057]
In the third semiconductor laser device of the present invention, at least one of the light detection portion PD1 and the light detection portion PD2 includes five strip-shaped regions, four strip-shaped regions, and six strips. It is preferably divided into any of strip-like regions. According to the semiconductor laser device as described above, the diffracted light in the divided regions can be appropriately separated, and each diffracted light as the conjugate light is also appropriately separated. For this reason, in the light detection unit, each diffracted light can be reliably separated and detected, and a better TE signal of the phase difference method can be obtained.
[0058]
A fourth semiconductor laser device of the present invention includes a first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2, and the amount of light received by the light. A semiconductor laser device comprising a light detection unit that outputs an electrical signal according to
The photodetection unit includes a photodetection unit PD1 that receives light with the wavelength λ1, a photodetection unit PD2 that receives light with the wavelength λ2, and a photodetection unit PD0 that receives both light with the wavelengths λ1 and λ2. Including
The distances between the center of the light detector PD0 and the light emitting points of the first and second semiconductor laser light sources are d1 and d2, respectively, and the distance between the light emitting points of the first and second semiconductor laser light sources is d12. And when
The distance between the center of the light detector PD1 and the light emitting point of the first semiconductor laser light source is d1, and the distance between the center of the light detector PD2 and the light emitting point of the second semiconductor laser light source is d2,
λ1 / λ2 = d1 / d2
Substantially satisfying the relationship
d2 = d1 + d12,
Satisfying the relationship
d1 = λ1 · d12 / (λ2-λ1)
d2 = λ2 · d12 / (λ2-λ1)
The above relationship is substantially satisfied. According to the semiconductor laser device as described above, the photodetection unit can be used in common for both wavelengths, and the number of photodetection units can be reduced. When λ1 is shorter than λ2, the first semiconductor laser light source, the second semiconductor laser light source, the light detection part PD1, and the light detection part PD2 are arranged in the direction orthogonal to the optical axis in this order to reduce d1. However, the length of the light detection unit can be secured, and the light detector can be downsized.
[0059]
In the first or second semiconductor laser device, the light detection part PD1 and the light detection part PD2 are each divided into a plurality of regions, and the shapes of the light detection part PD1 and the light detection part PD2 Are preferably different. According to the semiconductor laser device as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0060]
The light detection unit PD1 and the light detection unit PD2 are each divided into a plurality of regions by dividing lines, and a symmetrical center line parallel to the dividing line of the light detection unit PD2 and the light detection unit PD1. It is preferable that a symmetric center line parallel to the dividing line is shifted in a direction perpendicular to the symmetric center lines. According to the semiconductor laser device as described above, the offset of the focus error signal can be prevented even when recording / reproducing optical disks having different substrate thicknesses.
[0061]
In the first to fourth semiconductor laser devices, it is preferable that the first semiconductor laser light source and the second semiconductor laser light source are formed monolithically on one semiconductor chip. According to the semiconductor laser device as described above, the number of assembling steps can be reduced, and the distance between the light emitting points of the two light sources can be determined accurately.
[0062]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0063]
(Embodiment 1)
FIG. 1 is a configuration diagram of an optical pickup according to Embodiment 1 of the present invention. In FIG. 1, the semiconductor laser light source is composed of a red laser 1a and an infrared laser 1b. Reference numerals 81, 82, and 83 denote light detection units (PD0, PD1, PD2) that receive a light beam and photoelectrically convert it into an electric signal such as a current. 3 is a diffraction grating.
[0064]
Reference numeral 4 denotes a diffractive means, which uses an optical element having a periodic structure in phase and transmittance.
In the diffracting means 4, the period and direction, that is, the lattice vector may vary depending on the location. The diffracting means 4 is typically a hologram, for example, a phase type hologram. In the following description, the diffracting means 4 will be described as the hologram 4. A collimating lens 5 and an objective lens 6 constitute a condensing optical system. Reference numeral 7 denotes an optical disk.
[0065]
In the optical pickup shown in the figure, the portion having the semiconductor laser light source and the light detection portion corresponds to the semiconductor laser device. The same applies to the following embodiments.
[0066]
As will be described later, as the optical disc 7, the substrate thickness (thickness from the surface on which the light beam emitted from the objective lens is incident on the optical disc to the information recording surface) is a CD or CD-R having about t1 = 1.2 mm, etc. It includes both DVDs (DVD-ROM, DVD-RAM, etc.) having a substrate thickness of about t2 = 0.6 mm. Hereinafter, an optical disk having a substrate thickness of about 1.2 mm and a recording density similar to that of a CD-ROM is collectively referred to as a CD optical disk, and a substrate thickness of about 0.6 mm and a recording density similar to that of a DVD-ROM. The optical disc is generically called a DVD optical disc.
[0067]
As an example, the red laser 1a and the infrared laser 1b can have separate semiconductor laser chips arranged in a hybrid. In that case, each semiconductor laser chip can be manufactured with a minimum size and by an optimal manufacturing method, so that low noise, low current consumption, and high durability can be realized. As another example, the red laser 1a and the infrared laser 1b may be monolithically formed on a single semiconductor laser chip. In that case, the number of assembling steps can be reduced and the distance between the two light emitting points can be determined accurately. Any of these configurations can be applied to the following optical pickups and all the embodiments.
[0068]
The photodetectors 81, 82, and 83 correspond to the photodetectors PD0, PD1, and PD2 described in the section “Means for Solving the Problems”, respectively. Although the photodetecting portions 81, 82, and 83 are illustrated separately in FIG. 1, by forming them on a single silicon substrate, the relative positional relationship between them can be accurately determined.
[0069]
An operation when information is recorded on or reproduced from the optical disc will be described with reference to FIGS. FIG. 2 is an explanatory diagram when recording or reproducing is performed on a DVD (DVD-ROM, DVD-RAM, etc.) optical disc 71 having a base material thickness t2 of about 0.6 mm using the red laser 1a.
[0070]
The red light beam 2 emitted from the red laser 1 a passes through the diffraction grating 3 and the hologram 4, is made substantially parallel light by the collimator lens 5, and is converged on the optical disk 71 by the objective lens 6. Further, the red light beam 2 is diffracted and reflected by the pits and track grooves on the recording surface of the optical disc 71, then returns almost the same optical path, and is incident again on the hologram 4 through the objective lens 6 and the collimator lens 5. + 1st order diffracted light 10 and −1st order diffracted light 11 are generated.
[0071]
The + 1st order diffracted light 10 and the −1st order diffracted light 11 enter the light detection unit 81 and the light detection unit 82, respectively, and are photoelectrically converted. Here, if the distance between the center of the light detection unit 81 and the emission point of the red laser 1a is d1, the center of the light detection unit 82 that receives the −1st order diffracted light 11 conjugate with the + 1st order diffracted light 10 and the red laser 1a. The distance from the light emitting point must also be approximately d1.
[0072]
FIG. 3 is an explanatory diagram when recording or reproducing is performed on a CD (CD-ROM, CD-R, etc.) optical disk 72 having a base material thickness t1 of about 1.2 mm using the infrared laser 1b.
[0073]
The infrared light beam 25 emitted from the infrared laser 1b is diffracted when passing through the diffraction grating 3 to generate a ± 1st order sub-spot, and passes through the hologram 4 together with the 0th order diffracted light (main spot). The collimating lens 5 makes the light substantially parallel, and the objective lens 6 converges it on the optical disk 71. Further, the infrared light beam 25 is diffracted and reflected by the pits and track grooves on the recording surface of the optical disc 71, then returns almost the same optical path, and is incident on the hologram 4 again through the objective lens 6 and the collimator lens 5. Then, + 1st order diffracted light 12 and −1st order diffracted light 13 are generated. The + 1st order diffracted light 12 and the −1st order diffracted light 13 enter the light detection unit 81 and the light detection unit 83, respectively, and are photoelectrically converted.
[0074]
Here, if the distance between the center of the light detection unit 81 and the light emitting point of the infrared laser 1b is d2, the center of the light detection unit 83 that receives the −1st order diffracted light 13 conjugate with the + 1st order diffracted light 12 and the infrared laser. The distance from the light emitting point 1b also needs to be approximately d2.
[0075]
The grating cross-sectional shape of the diffraction grating 3 is shown in FIG. The grating cross section of the diffraction grating 3 is substantially rectangular, and the width W1 of the concave portion and the width W2 of the convex portion are substantially equal. When the wavelength of the red light beam 2 is λ1, and the refractive index of the diffraction grating material for the wavelength λ1 is n1, the step h between the concave portion and the convex portion of the cross-sectional shape is
h = λ1 / (n1-1) (1)
As described above, the optical path difference between the concave portion and the convex portion is set to be one wavelength with respect to red light. By doing so, the phase difference due to the optical path difference becomes 2π, and, by design, red light is not diffracted by the diffraction grating 3, and light can be used effectively without loss of light quantity. In the case of infrared light, since the wavelength is longer than that of red light, the optical path difference caused by the step h is smaller than one wavelength and the phase difference is smaller than 2π. Can be generated.
[0076]
When reproducing a CD optical disk with an infrared light beam, NA needs to be 0.45 or more, but diffracted light is generated from the entire range where the NA of the sub beam is 0.45 in the objective lens 6. Thus, it is necessary to produce diffraction fringes in the diffraction grating 3 in a sufficiently wide range.
[0077]
In addition, as described above, it is desirable to design the red light beam 2 so that diffraction does not occur, but it is conceivable that slight diffraction occurs due to manufacturing errors. When a part of the red light beam 2 passes through a part of the diffraction grating 3 having no diffraction grating fringes and enters the objective lens 5, intensity and phase unevenness (difference depending on the location) with the light passing through the diffraction fringes occurs, and the optical disc 71 Convergence performance on the recording surface may deteriorate. Therefore, with respect to the red light beam 2 as well, lattice fringes are formed in the entire range where the light beam that is not diffracted by the diffraction grating 3 and enters the objective lens 6 satisfies the NA (0.6) necessary for DVD optical disk reproduction. Is desirable.
[0078]
However, the light reflected and returned from the CD optical disk 72 is incident on the hologram 4 and diffracted. When the diffracted light 12 or the diffracted light 13 is incident on the lattice stripe, it is further diffracted and a light amount is lost. Therefore, it is necessary to limit the range of the grating stripes on the diffraction grating 3 with respect to the diffracted light 12 or the diffracted light 13.
[0079]
For example, by producing grating stripes in the portion where the diffraction grating 3 is shown in FIG. 1, it is possible to ensure the convergence spot performance during reproduction of a DVD optical disk and to prevent light loss during reproduction of a CD optical disk. Although not shown, the diffraction grating 3 includes a lattice pattern, and has a transparent substrate over a wider range, and the diffracted light 12 and the diffracted light 13 pass through the transparent portion (where no lattice pattern is formed). The configuration.
[0080]
In addition, the DVD optical disk is a higher density optical disk than the CD optical disk and needs to be reproduced (or recorded) with a convergent spot with less aberration than the CD optical disk, so that the red laser 1a emission point is within the assembly tolerance range. Therefore, it is desirable to arrange on the optical axis of the condensing optical system (in this embodiment, the optical axis of the collimating lens 5). As a result, the laser light from the short wavelength laser element that is easily affected by the lens aberration passes through the vicinity of the optical axis of the collimating lens 5 having a small degree of lens aberration. For this reason, off-axis aberration does not occur during DVD optical disk reproduction, and high-density DVD optical disks can be reproduced (or recorded) more stably.
[0081]
Further, consider the relationship between the distance d1 between the center of the light detection unit 81 and the emission point of the red laser 1a, the distance d2 between the center of the light detection unit 81 and the emission point of the infrared laser 1b, and the wavelength. Since the diffraction distance is almost proportional to the wavelength, if the wavelength of the red laser is λ1 and the wavelength of the infrared laser is λ2,
d1: d2 = λ1: λ2 (2)
To satisfy the relationship of
d1 / d2 = λ1 / λ2 (2 ′)
Arrange to satisfy the relationship. As a result, the light detection unit 81 can be used in common for both wavelengths, and the number of light detection units can be reduced. Accordingly, it is possible to realize a reduction in cost and a reduction in size due to a reduction in the area of the photodetector, a reduction in the number of circuit elements for converting the output into a current voltage.
[0082]
Further, if the distance between the emission point of the red laser 1a and the emission point of the infrared laser 1b is d12, as is apparent from FIGS. 2 and 3,
d2 = d1 + d12 (3)
It is. From Equation (2) and Equation (3),
d1 = λ1 · d12 / (λ2-λ1) (4)
d2 = λ2 · d12 / (λ2-λ1) (5)
By arranging in this way, the light detector 81 can be used in common for both wavelengths for a predetermined distance between light emitting points and wavelengths, and the number of light detectors can be reduced. Reduction in cost and reduction in size can be realized by reducing the number of circuit elements for converting the output to current-voltage.
[0083]
Here, the two laser light sources 1a and 1b and the light detectors 82 and 83 provided separately from each other are light corresponding to the red laser 1a, the infrared laser 1b, and the red laser in order from the left side of FIG. The detector 82 and the light detector 83 corresponding to the infrared laser are arranged in this order. In this way, when d12 is, for example, about 100 μm to 120 μm and d1 is about 500 μm, the length of the light detection portions 82 and 83 in the left-right direction in FIG. 2 can be secured to 50 μm or more, and the photodetector can be made compact. There is an effect that can be realized. On the other hand, JP-A-1998-124918 has a configuration in which the order of the photodetector 82 and the photodetector 83 is reversed. Therefore, if d1 is not set to 1 mm or more, the length of the photodetection unit can be ensured to be 50 μm or more. The size of the entire photodetection unit cannot be increased and cannot be reduced in size. That is, the effect that the photodetection part of this application can be reduced in size cannot be obtained.
[0084]
In addition, in said Formula (2 '), (4), and (5), the value of the both sides of each formula should just be in agreement. That is, it includes not only the case where the values on both sides completely match, but also the case where the effects of satisfying each of the above expressions are substantially matched to such an extent that they can be achieved with no practical problem.
[0085]
(Embodiment 2)
5 and 6 show a case where a thin optical pickup is configured by using a rising mirror in the second embodiment. FIG. 5 shows a case where the DVD optical disk is reproduced by emitting the red light beam 2. FIG. 6 shows a case where a DVD optical disk is reproduced by emitting an infrared light beam 25.
[0086]
The light that has been made substantially parallel by the collimator lens 5 is reflected by the rising mirror 17 and changes the traveling direction. Thereby, the size (thickness) of the optical pickup in the direction perpendicular to the plane of the optical disc 7 is reduced.
[0087]
As shown in FIG. 5, the wavelength selective diaphragm 18 is configured so that it acts as a simple transparent plate for the red light beam 2 and does not act at all. As shown in FIG. 6, with respect to the infrared light beam 25, the light beam away from the optical axis is shielded by the wavelength selective diaphragm 18. The wavelength selective stop 18 can be realized by a method such as forming dielectric multilayer films having different wavelength characteristics or forming phase gratings having different phase modulation amounts in the vicinity of the optical axis and the outer peripheral portion away from the optical axis. Since the DVD optical disk has a high recording density, it is necessary to perform reproduction with a NA larger than that of the CD optical disk. Therefore, by using such means for changing the NA according to the wavelength, the NA during CD optical disk reproduction is minimized. Aberration due to substrate thickness and disc tilt can be reduced.
[0088]
5 and 6, reference numeral 15 denotes a package, which contains at least the red laser 1a, the infrared laser 1b, and the photodetector in which the light detection portions 81 to 83 shown in FIG. 1 are formed. A unit in which the light source and the photodetector are integrated and integrated into one part is hereinafter referred to as a unit. The hologram 4 may be arranged near the collimating lens 5, but if the hologram 4 is also integrated in the unit 16, components necessary for generating a servo signal can be fixed close to each other. Servo signal detection that is less affected and stable is possible.
[0089]
The hologram 4 may be fixed to the objective lens 6 and driven integrally. At the time of DVD-RAM reproduction, diffracted light generated from the hologram 4 is received by the divided region of the photodetector, the output is subjected to differential calculation, and a push-pull (PP) tracking error (TE) signal is obtained. At this time, if the far field image (FFP) moves with respect to the hologram 4 by the movement of the objective lens 6, a TE signal offset is generated. If the objective lens 6 and the hologram 4 are integrally driven, even if the objective lens 6 moves, the relative position between the FFP that has passed through the objective lens 6 and the hologram 4 does not change, thus eliminating unstable factors such as the occurrence of TE offset. it can.
[0090]
(Embodiment 3)
FIG. 7 shows the photodetector 8 in the third embodiment. The photodetector 8 has a configuration in which a red laser 1a, an infrared laser 1b, and light detection units 81 to 83 are integrated. The photodetector 8 includes photodetectors 81 to 83 formed on a silicon substrate or the like. Thus, by forming all the photodetecting portions on a single substrate, the number of electrical connection steps can be reduced, and the relative position between the photodetectors can be determined with high accuracy. Reference numeral 1 denotes a laser light source such as a semiconductor laser, in which a red laser and an infrared laser are monolithically integrated. As described above, by integrally forming lasers of two types of wavelengths in the one-chip semiconductor laser light source 1, the distance between the emission points of the red laser and the infrared laser can be determined with an accuracy of the order of μm or sub-μm. . Therefore, good characteristics can be obtained for both detection signals when light of both wavelengths is used.
[0091]
A small reflection mirror 14 is formed in the direction in which the red light beam 2 and the infrared light beam 25 are emitted from the laser light source 1, and the red light beam 2 is perpendicular to the plane formed by the light detection units 81 to 83. Or the optical axis of the infrared light beam 25 is bent. This mirror 14 can be realized by anisotropically etching the silicon of the substrate or attaching a small prism mirror to the photodetector 8. By forming a light detection unit 89 on the opposite side of the laser light source 1 from the mirror 14, the amount of light emitted from the laser light source 1 in that direction is detected and used as a signal for controlling the light emission amount. it can.
[0092]
Next, detailed configurations of the light detection units 81 to 83 and the hologram 4 will be described with reference to FIGS. The overall configuration of the optical pickup is the same as that shown in FIG. 1, and the basic operation is the same as that described with reference to FIGS.
[0093]
FIG. 8 is a view of the photodetector 8 as seen from a direction perpendicular to the surface thereof. The red light spot 4R indicates the effective diameter of the red light beam on the hologram 4 (that is, the projection of the effective diameter of the objective lens 5) when the red laser 1a emits light, that is, when a DVD optical disk is reproduced. P4A to P4D and M4A to M4D indicate projections of the diffracted light generated from the hologram 4 on the photodetector 8. The infrared light spot 4R corresponds to a part of the hologram 4, and the hologram 4 is formed in a wider range than the infrared light spot 4R. 1aL indicates the emission point of the red laser 1a, and the red light spot 4R on the hologram 4 spreads around the emission point 1aL.
[0094]
The light detection units 81, 82, and 83 are formed on a common substrate, and therefore the positional relationship with each other can be easily determined with high accuracy. Further, by forming the semiconductor laser on the same substrate, the relative positional relationship with the light detection unit becomes stable, and the servo signal can be obtained stably. Note that the light detection units 81, 82, and 83 may be independently formed on a Si substrate or the like and assembled into a hybrid, or some of them may be formed on a common substrate.
[0095]
P4A, P4B, P4C and P4D are + 1st order diffracted light diffracted from the hologram 4, and M4A, M4B, M4C and M4D are -1st order diffracted light diffracted from the hologram 4. The hologram 4 is divided into at least four by the xy axis, and P4A and M4A are diffracted from the region 4A, P4B and M4B are from the region 4B, P4C and M4C are from the region 4C, and P4D and M4D are diffracted from the region 4D. To design.
[0096]
The focus error signal (FE signal) can be obtained by receiving the first-order diffracted light M4A, M4B, M4C, and M4D diffracted from the hologram 4 by the light detection unit 82. For example, M4A and M4D focus on the opposite side of the collimating lens 5 (FIG. 1) with respect to the surface of the light detection unit 82 (referred to as a rear pin), and M4B and M4C The wavefront is designed to focus on the same side as the collimating lens 5 (this is called the front pin).
[0097]
That is, it is designed to generate wavefronts having different focal positions in the optical axis direction. Therefore, when the distance between the DVD optical disk 71 and the objective lens in the optical axis direction is shifted, that is, before and after the position where the convergence spot is in focus on the information recording surface by defocusing, the diffracted light on the light detection unit 82 The size of each changes. This change is a movement opposite to the difference in focus position (for example, M4A and M4D are large and M4B and M4C are small).
[0098]
Therefore, as shown in FIG. 8, the divided areas are connected, and the signals of F1 and F2 obtained by adding the output of each strip-shaped area are
FE = F1-F2 (6)
The FE signal can be obtained by performing a differential operation.
[0099]
The TE signal is obtained as follows. That is, the y direction of the photodetector 8 is set to the projection direction of the track extending direction (tangential direction) of the DVD optical disc 71, and the x direction is set to the radiation direction (radial direction) extending from the disc center toward the outer periphery. As shown in FIG. 9, a recordable optical disc such as a DVD-RAM has a guide groove and is strongly diffracted by the guide groove. In FIG. 9, for convenience of explanation of the operation, the upper half is shown in an elevation view and the lower half is shown in a plan view. In FIG. 9, 25, 26, and 27 indicate 0th-order, + 1st-order, and −1st-order diffracted lights by the guide grooves on the optical disc recording surface 24, respectively. Reference numeral 84 denotes a two-divided photodetector used for explanation. The photodetector 84 is shown in a state viewed from the optical axis direction perpendicular to the optical disc surface 24 and the objective lens 6.
[0100]
When the convergence spot is irradiated onto the guide groove of the optical disk recording surface 24, the reflected light is diffracted in a direction perpendicular to the extending direction of the guide groove. The FFP (far-field image) 28 that has returned to the objective lens surface generates a light intensity distribution in the A and B portions due to the interference between the ± 1st order diffracted light and the 0th order diffracted light in the guide groove. Depending on the positional relationship between the guide groove and the convergence spot, A is bright and B is dark, or A is dark and B is bright. By detecting such a change in light intensity with a two-divided photodetector, a PP method TE signal is obtained.
[0101]
In the embodiment shown in FIG. 8, the hologram 4 (only the red light 4R on the hologram is shown in FIG. 8) is located at the position of the two-divided photodetector 84 in FIG. In consideration of the divided area of the light detection unit where the diffracted light from the area reaches, the signal intensity is displayed by area name (the same applies below),
TE = (TA + TB) − (TC + TD) (7)
Thus, a tracking error (TE) signal by the push-pull method can be obtained.
[0102]
In addition, it is necessary to use a TE signal based on the phase difference method during DVD-ROM reproduction. In this case, a phase difference TE signal can be obtained by phase comparison between the (TA + TC) and (TB + TD) signals. The phase difference TE signal can also be obtained by phase comparison between TA and TB or TC and TD.
[0103]
Note that, as described above, the FE signal detection diffracted light received by the light detection unit 82, for example, M4A and M4D are focused on the opposite side of the collimating lens 5 (FIG. 1) with respect to the surface of the light detection unit 82, M4B and M4C are focused on the same side as the collimating lens 5 (FIG. 1) with respect to the surface of the light detection unit 82. That is, the characteristics of the diffracted light diffracted from the region 4A of the hologram 4 and the diffracted light diffracted from the region 4D of the hologram 4 are the same.
[0104]
As described above, when the characteristics of the diffracted light diffracted from the region symmetric with respect to the y-axis corresponding to the tangential direction of the optical disc 7 of the hologram 4 are made the same, the A described with reference to FIG. And B light intensity changes cancel each other with diffracted light diffracted from a region symmetric with respect to the y-axis. For example, if the amount of light increases at A due to tracking deviation, the amount of light at B decreases by this increase, and becomes zero when the changes in the amount of light of A and B are summed. For this reason, even if the TE signal changes, the FE signal is not affected, and mixing of the TE signal into the FE signal, that is, generation of a so-called groove crossing signal can be prevented.
[0105]
The information (RF) signal is then
RF = TA + TB + TC + TD (8)
Can be obtained by: Or
RF = TA + TB + TC + TD + F1 + F2 (9)
As described above, the signal / noise ratio (S / N) with respect to electrical noise can be increased by obtaining the RF signal by using all ± first-order diffracted lights.
[0106]
As shown in FIG. 8, the diffracted light M4D and the diffracted light M4A can be appropriately separated by configuring the region 82 from five strip-shaped divided regions. Further, the diffracted light M4B and the diffracted light M4C can be separated appropriately. For this reason, the diffracted light P4D and the diffracted light P4A, which are the conjugate lights, are appropriately separated. Similarly, the diffracted light P4B and the diffracted light P4C are also appropriately separated. For this reason, the light detection unit 81 can reliably separate the four diffracted lights and detect the signal, and can obtain a better TE signal of the phase difference method.
[0107]
FIG. 10 shows a state of recording or reproducing a CD optical disc by emitting infrared light in the unit having the same configuration as FIG. As shown in FIG. 3, the infrared light beam 25 is partially diffracted by the diffraction grating 3 to form a sub beam. This sub beam is converged and reflected on the CD optical disk 72 in the same manner as the main beam, and is incident on the photodetector 8. Unlike the case of the red light beam in FIG. 8, the infrared light beam is incident on the light detection unit 81 and the light detection unit 83. The region of the light detection unit 81 on which the main beam is incident is the same as in the case of FIG. 8, and the operation is also the same.
[0108]
The region where the main beam is incident on the light detection unit 83 corresponds to the case of the light detection unit 82, and the operation is the same. The sub beams are incident on the divided regions TF and TG of the light detection unit 81 and the divided regions TH and TI of the light detection unit 83. Note that the infrared light spot 4IR in FIG. 10 shows the main beam in the same manner as the red light spot 4R in FIG. 1bL indicates the emission point of the infrared laser 1b, and the infrared light spot 4IR on the hologram 4 spreads around the emission point 1bL.
[0109]
First, generation of the FE signal will be described. Basically, this is the same as in FIG. When the distance in the optical axis direction between the CD optical disk 72 and the objective lens is shifted, that is, due to defocusing, the magnitude of the diffracted light on the light detection unit 83 changes. This change is a movement opposite to the difference in focal position. Therefore, the signals of F3 and F4 obtained by connecting the divided areas of the light detection unit 83 and adding the output of each strip-shaped area as shown in FIG.
FE = F3-F4 (10)
The FE signal can be obtained by performing a differential operation. Since the hologram 4 is divided into four by the xy axis, the magnitudes of the four diffracted lights for detecting the signals of F3 and F4 are not equal to each other, but there is no problem in detecting the FE signal. This is because areas A and D and areas B and C of hologram 4 are a combination of large and small, respectively.
[0110]
Further, for example, by connecting F1 and F3 and F2 and F4 in the photodetector 8, the number of IV amplifiers for converting a current signal obtained from the photodetector to a voltage signal, or from the unit to the outside It is possible to reduce the number of electrical terminals from which signals are output and to reduce the size of the unit.
[0111]
By the way, DVD and CD have different substrate thicknesses. For this reason, when the FE signal detection is performed by the light detection unit having the same shape, an offset may occur in the FE signal due to the influence of spherical aberration. Therefore, as shown in FIG. 10, the symmetry line (center line) along the x axis of the light detection unit 83 is shifted from the symmetry line along the x axis of the light detection unit 82. FIG. 10 shows that the distances a and b between the two dividing lines in the x-axis direction forming the central strip region of the light detection unit 83 and the symmetry line of the light detection unit 82 are a ≠ b. Show. Also, since the size of the diffracted light is different due to the influence of the wavelength and the spherical aberration, an FE signal having a high sensitivity and a wide dynamic range can be obtained by changing the width of the strip between the light detection unit 82 and the light detection unit 83.
[0112]
The TE signal at the time of CD reproduction can be detected by the phase difference method as in the case of DVD reproduction, but the CD-R guarantees the three-beam method. Therefore, the TE signal is detected so that sub-beams incident on the divided regions TF, TG, TH, and TI of the photodetector 8 can also be used. TE signal by 3 beam method is
TE = (TF + TH) − (TG + TI) (11)
It can be obtained by the operation.
[0113]
It is also possible to obtain the effect that the number of output terminals to the outside can be reduced and the unit can be miniaturized by internally connecting TF and TH with an aluminum wiring or the like in the photodetector 8. The same applies to TG and TI.
[0114]
Also,
TE = TF-TG (12)
Or
TE = TH-TI (13)
The TE signal can be detected by the 3-beam method, the number of output terminals to the outside can be reduced, and the unit can be downsized.
[0115]
The information (RF) signal is then
RF = TA + TB + TC + TD (14)
Can be obtained by: Or
RF = TA + TB + TC + TD + F3 + F4 (15)
As described above, the signal / noise ratio (S / N) with respect to electrical noise can be increased by obtaining the RF signal by using all ± first-order diffracted lights.
[0116]
As is clear from the equations (4) and (5) and FIG. 8 or FIG. 10, the distance between the center of the light detection unit 82 and the center of the light detection unit 83 is twice as long as d12. The center of the light detection unit and the center of the diffracted light can be made coincident, and even if there is an error such as wavelength variation, light can be received without omission.
[0117]
In addition, F1, F2, F3, and F4 are described as being independent in the above-described drawings and the like. For example, the number of output terminals to the outside is reduced by internally connecting F1 and F3, and F2 and F4. The unit can be downsized.
[0118]
(Embodiment 4)
The fourth embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a view of the photodetector 801 viewed from a direction perpendicular to the surface thereof. The red light spot 401R indicates the effective diameter of the light beam on the hologram (that is, the projection of the effective diameter of the objective lens 5) when the red laser 1a emits light, that is, when reproducing a DVD optical disk. P401A to P401D and M401A to M401D represent projections on the photodetector 801 of diffracted light generated from the hologram. The light detector 801 corresponds to the light detector 8 in the third embodiment, and the shape is changed. The light detection units 811, 821, and 831 correspond to the light detection units 81, 82, and 83 in the third embodiment, respectively, and have different shapes. Similarly, the hologram and its divided areas 401A, 401B, 401C and 401D correspond to the hologram 4 and its divided areas 4A, 4B, 4C and 4D in the third embodiment, respectively, and the shapes thereof are changed.
[0119]
The FE signal when the red laser 1a is emitted is obtained from the light detection unit 821. The light detection unit 821 is composed of four regions. Therefore, the projections M401D and M401B are made incident on the same region. By reducing the number of regions compared to the third embodiment, the area of the light detection unit can be reduced, and the influence of stray light on the FE signal due to scattered light or the like can be reduced. As shown in FIG. 11, the signals of F11 and F21 obtained by connecting the divided areas of the light detection unit 821 and adding the outputs of the two areas are obtained.
FE = F11−F21 (16)
The FE signal can be obtained by performing a differential operation. A TE signal and an RF signal can also be obtained in the same manner as in the third embodiment.
[0120]
FIG. 12 shows the time when the infrared laser 1b is emitted, that is, when the CD optical disk is reproduced. The infrared light spot 401IR is the same as the infrared light spot 4IR in FIG.
[0121]
The FE signal at the time of emitting the infrared laser 1b is obtained from the light detection unit 831. The central portion of the light detection unit 831 corresponding to the light detection unit 821 is composed of four regions. Thereby, the area of the light detection unit can be reduced, and the influence of stray light on the FE signal due to scattered light or the like can be reduced. As shown in FIG. 12, the signals of F31 and F41 obtained by connecting the divided regions of the light detection unit 831 and adding the outputs of the two regions are obtained.
FE = F31−F41 (17)
The FE signal can be obtained by performing a differential operation. A TE signal and an RF signal can also be obtained in the same manner as in the third embodiment.
[0122]
Since the configuration other than that described above is the same as that of the third embodiment, description thereof is omitted.
[0123]
(Embodiment 5)
The fifth embodiment will be described with reference to FIGS. FIG. 13 is a view of the photodetector 802 viewed from a direction perpendicular to the surface thereof. The red light spot 402R indicates the effective diameter of the light beam on the hologram (that is, the projection of the effective diameter of the objective lens 5) when the red laser 1a is emitted, that is, when the DVD optical disk is reproduced. Further, the state of the diffracted light generated from the hologram on the light detection units 812 and 822 is shown. The photodetector 802 corresponds to the photodetector 8 in the third embodiment, and the shape is changed. The light detection units 812, 822, and 832 correspond to the light detection units 81, 82, and 83 in Embodiment 3, respectively, and have different shapes. Similarly, the hologram and its divided areas 402A, 402B, 402C, and 402D correspond to the hologram 4 and its divided areas 4A, 4B, 4C, and 4D, and the photodetector 8 in Embodiment 3, respectively, and the shapes thereof are changed. It is.
[0124]
For example, the regions 402A and 402D of the hologram 4 are collectively treated as one region, and diffracted light (front pin and rear pin) having focal points on the front side and the rear side in the optical axis direction with respect to the photodetector 802 is selected from these regions. generate. And then. The light detection unit 822 in FIG. 13 makes the light incident on the divided regions for obtaining the signals F12 and F22. In order to generate the diffracted light of the front pin and the rear pin from the regions 402A and 402D, for example, the region is further divided into a plurality of parts by a dividing line extending in parallel with the y axis, and the diffracted light of the front pin and the rear pin is generated alternately. It is sufficient to form a grid for this purpose. Note that the diffracted light of the front pin and the rear pin may be focused on the front side and the rear side of the photodetector 802 with respect to the direction along the y axis. Further, the focusing on the front side and the rear side does not have to be focused at one point, but is focused in the x-axis direction and unfocused in the y-axis direction, that is, the focus extending in the y-axis direction. You may focus on the line.
[0125]
Diffracted light incident on the divided regions TA2 and TB2 of the light detection unit 822 is generated from the regions 402B and 402C of the hologram 4, respectively.
[0126]
All of the diffracted light is diffracted to the light detection unit 822, but the conjugate light is incident on the divided region RF2 of the light detection unit 812.
[0127]
In the above configuration, the FE signal when the red laser 1a is emitted is obtained from the light detection unit 822.
F12 and F22 signals
FE = F12−F22 (18)
The FE signal can be obtained by performing a differential operation. TE signal is
TE = TA2-TB2 (19)
Thus, a push-pull TE signal can be obtained. Further, the phase difference method TE can be obtained by comparing the phases of TA2 and TB2.
[0128]
The RF signal can be obtained from the signal in region RF2. In the present embodiment, since the RF signal can be obtained from the signal only in the region RF2, only one IV conversion amplifier for the RF signal requiring the highest frequency characteristics and S / N ratio can be obtained. The cost for the V conversion amplifier can be minimized.
[0129]
FIG. 14 shows the time when the infrared laser 1b is emitted, that is, when the CD optical disk is reproduced. The infrared light spot 402IR is the same as the infrared light spot 4IR in FIG.
[0130]
The diffracted light generated from the divided regions 402A and 402D of the hologram 4 becomes the light spot of the front pin and the rear pin as in the case of red laser light emission. Then, the light is incident on the divided regions F32 and F42 of the light detection unit 832. Diffracted light generated from the divided regions 402B and 402C of the hologram 4 (the boundary line is the y-axis) enters the region RF1. All the diffracted light enters the light detection unit 832, but the conjugate diffracted light enters the divided region RF <b> 2 of the light detection unit 812.
[0131]
Further, as shown in FIG. 3, the sub-beam generated by the diffraction grating 3 in the outward path is divided into the divided areas TF2 and TG2 of the light detection unit 812 and the divided areas TH2 and TI2 of the light detection unit 832 as shown in FIG. The light beam reflected by the light beam and further diffracted by the hologram 4 enters.
[0132]
In the above configuration, the FE signal when the infrared laser 1b is emitted is obtained from the light detection unit 832.
Signals in regions F32 and F42 are
FE = F32−F42 (20)
The FE signal can be obtained by performing a differential operation. TE signal is
TE = (TF2 + TH2) − (TG2 + TI2) (21)
Thus, a TE signal of the three beam method can be obtained. The RF signal can again be obtained from the signal in region RF2.
[0133]
Since the configuration other than that described above is the same as that of the third embodiment, description thereof is omitted.
[0134]
In the above embodiment, the DVD optical disk and the CD optical disk have been described as examples. However, as the optical disk 7, a first optical disk having a transparent substrate thickness t1 and a second optical disk having a thickness t2 different from t1 are reproduced or recorded. It is applicable when When t1 is set to 0.6 mm and t2 is set to 1.2 mm, the present invention can be widely applied to DVD optical disks and CD optical disks that are currently on the market, but is not limited to this, and can be applied to various combinations. Further, the wavelength has been described as λ1 is red light of 610 nm to 680 nm and λ2 is red light of 740 nm to 830 nm. However, the present invention can also be applied to the case where one is violet light of about 400 nm. That is, λ1 and λ2 can be combined other than the above.
[0135]
The main part of the present invention described in the above embodiment is, for example, in the unit 16 shown in FIG.
[0136]
Further, the optical pickup of the present invention can detect a TE signal by the three-beam method during CD reproduction, thereby obtaining a stable TE signal that does not cause an offset even when the setting position of the hologram element is different from the normal position. Therefore, information reproduction can be performed accurately and stably, which is also due to the characteristics of the unit.
[0137]
(Embodiment 6)
Embodiment 6 will be described with reference to FIG. FIG. 15 is a schematic plan view showing a hologram configuration according to the sixth embodiment. In the sixth embodiment, a spot size detection method (SSD method) is used to detect a focus servo signal.
[0138]
As disclosed in Japanese Patent Laid-Open No. 2-185722, the SSD method can remarkably reduce the assembly tolerance of the optical head device, and can obtain a servo signal stably even with respect to wavelength fluctuations, and further tracking. This is a focus error signal detection method that has the effect of reducing the amount of error signals mixed into the focus error signal.
[0139]
In order to realize the SSD method, the + 1st order diffracted light in the return path generated from the hologram is designed to be two types of spherical waves having different curvatures. Each spherical wave is focused on the front side or the back side of the surface of the light detection unit 82 or the light detection unit 83 in FIG. 1 (even a focal line extending in the direction perpendicular to the dividing line direction of the light detection region, that is, the y direction in FIG. 8). In the following, it is designed to have a spherical wave front focus and back focus for simplicity.
The focus error signal FE is
FE = F2-F1. . . (22)
It is obtained by the operation. Here, F2 and F1 are electric signals obtained from several photodetection regions as shown in FIG. 8, for example.
[0140]
As described above, in order to realize the spot size detection method, it is necessary to generate wavefronts of the front focus and the back focus. Also, in order to prevent the occurrence of focus offset due to lens shift or manufacturing error in red light emission, and to reduce the amount of tracking error signal mixed into the focus error signal, the red light emission point is used as the optical axis. The holograms in the four quadrants of the xy coordinate system (four regions divided by the xy axis) with the origin of the intersection of the optical axis and the hologram surface are respectively converted into a front focal wavefront generation region and a rear focal wavefront generation region (for example, FIG. It is desirable to form Bb and Bf).
[0141]
Furthermore, in order to reduce the amount of tracking error signal mixed into the focus error signal as described above during infrared light emission as well, the infrared light emission point is taken as the optical axis, and the intersection of the optical axis and the hologram surface is determined. It is desirable to form a front focal wavefront generation region and a rear focal wavefront generation region in a hologram in four quadrants (four regions divided by the xy axis) of the xy coordinate system as the origin.
[0142]
Therefore, for the red light, in addition to forming the front focal wavefront generation region and the rear focal wavefront generation region in each quadrant of the hologram surface, in order to suppress the occurrence of offset when emitting infrared light, one more A hologram area (for example, Bb2 in FIG. 15) is added.
[0143]
Here, for example, a hologram for generating the back focal wavefront is formed in the hologram areas Bb and Bb2, and a hologram for generating the front focal wavefront is formed in the hologram area Bf.
[0144]
This embodiment is characterized in that the focus offset suppression region is formed on the hologram surface as described above, and can be combined with any other embodiment of the present application. In addition, the focus offset can be suppressed both when red light is emitted and when infrared light is emitted, so that a stable and accurate focus servo operation can be realized.
[0145]
(Embodiment 7)
FIG. 16 shows an optical disc apparatus according to Embodiment 6 using the optical pickup of the present invention. In FIG. 16, the optical disk 7 is rotated by the optical disk drive mechanism 32. The optical pickup 20 is coarsely moved (seek operation) by the optical pickup driving device 31 to the position of a track on the optical disc 7 where desired information exists.
[0146]
The optical pickup 20 also sends a focus error signal and a tracking error signal to the electric circuit 33 in accordance with the positional relationship with the optical disc 7. In response to this signal, the electric circuit 33 sends a signal for finely moving the objective lens to the optical pickup 20. In response to this signal, the optical pickup 20 performs focus servo and tracking servo on the optical disc 7, and reads, writes, and erases information on the optical disc 7.
[0147]
The optical disk apparatus according to the present embodiment uses an optical pickup that can obtain an information signal having a small S / N ratio and a good S / N ratio according to the present invention as described in the above embodiment. The reproduction of information can be executed accurately and stably, and it is advantageous in that it is small in size and low in cost.
[0148]
In addition, since the optical pickup of the present invention is small and light, the optical disk device of the present embodiment using the optical pickup has a short access time.
[0149]
(Embodiment 8)
With reference to FIG. 17, the optical disc type recognition method in the seventh embodiment will be described. In this embodiment, there is no optical disk in the optical disk device after power-on or after replacement of the optical disk, and whether the optical disk is a CD or a DVD is not yet recognized by the optical disk device. This is a method of recognizing the optical disc type.
[0150]
In the optical disc apparatus having an optical pickup using infrared light and red light as light sources as in the above embodiments, when the power is turned on or a new optical disc is inserted, the infrared light is first signaled. Light is emitted at a low output equivalent to that during reproduction (step S1). As a result, even if the optical disc is a CD-R, it is possible to prevent unnecessary writing or erasure of information by mistake. Here, the reason why red light is not emitted first is as follows. CD-R has a controlled reflectance with respect to infrared light, but the reflectance with respect to red light is not controlled, and the absorptance may be very high with respect to red light. Because.
[0151]
As described above, the presence or absence of the optical disk is determined based on the presence or absence of the reflected infrared light (step S2), and when there is no optical disk, the light emission is stopped (step S3), thereby realizing power saving. If there is an optical disk, the type of the optical disk is determined using the reflected light from the optical disk (step S4). In the present embodiment, the type of the optical disc is determined by detecting the thickness t of the transparent substrate. Since a known method can be used to determine the thickness, a specific description is omitted. In the present embodiment, the type of the optical disc is determined based on whether or not the thickness t is 0.6 mm. The method of discriminating the optical disc type may be appropriately selected according to the combination of the types of optical discs.
[0152]
If the thickness t of the transparent substrate of the inserted optical disk is not 0.6 mm, it is determined that the CD is a CD, and infrared light is continuously emitted (step S5), and information recording and reproduction are started (step S6). ). If the thickness t of the transparent substrate is 0.6 mm, it is determined that the DVD is a DVD, the infrared light is extinguished (step S7), the red light is turned on (step S8), and the DVD is recorded or reproduced (step S7). Step S9).
[0153]
The optical disc type recognition method of the present embodiment is preferably performed in combination with the optical pickup described in the above-described embodiment or the optical disc apparatus of the above-described embodiment, but is not limited to this. The present invention can be applied to an optical disc apparatus having an optical pickup using a plurality of light sources of wavelengths, and can prevent unnecessary writing or erasing information accidentally even if the optical disc is a CD-R. .
[0154]
(Embodiment 9)
FIG. 18 shows a copying machine 50 according to the ninth embodiment. The copying machine 50 includes an optical disk device 30 that records and reproduces an optical disk using the optical pickup and the optical disk type recognition method described in the above embodiment. The copying machine 50 includes a mechanism provided in a normal copying apparatus, such as a scanner mechanism for reading a document and a copying paper feeding mechanism, but illustration thereof is omitted. 51 is an information input / output terminal for exchanging information with other devices via a cable or a network, 52 is a mechanism for feeding a document (sheet feeder), and 53 is a paper discharge tray for storing copy paper after copying.
[0155]
The copying machine 50 has a function of copying a copy sheet as a normal copying machine. However, the copying machine 50 sends document information to the optical disk device 30 by an operation of the switch 54 or a command sent through an information input / output terminal. Can also be recorded. At this time, it is also possible to perform a copy at the same time. By copying a large amount of originals by the original feeding mechanism 52 and storing information printed on both sides as electronic information in the optical disc apparatus 30 at high speed, the information storage space can be compressed in a short time.
[0156]
(Embodiment 10)
FIG. 19 shows a video projection apparatus according to the tenth embodiment. This video projection apparatus includes an optical disc device 30 that uses the optical pickup or the optical disc type recognition method described in the above embodiments. In FIG. 19, reference numeral 62 denotes a windshield of an automobile, and 61 denotes a video projection unit that projects characters and pictures on the windshield 62.
[0157]
Information reproduced by the optical disk device 30 is displayed on the windshield 62 by the video projection unit 61. The windshield 62 is basically transparent, but has a reflectance of several percent, so that an image can be projected. Further, since the windshield 62 is not flat but has a curvature, the image is distorted. Therefore, it is desirable to process the information by the conversion circuit 63 that converts the information and compensate for this distortion because an image without distortion can be seen.
[0158]
The display video is not limited to characters and pictures, and may be a moving image. In particular, the present embodiment includes the optical disc device 30 and can reproduce an optical disc capable of recording a large amount of data, which is suitable for reproducing a moving image.
[0159]
【The invention's effect】
According to the present invention, the following effects can be obtained.
(1) Any of CD (CD-ROM, CD-R, etc.) and DVD (DVD-ROM, DVD-RAM, etc.) under optical conditions that are markedly different in the three factors of substrate thickness, light source wavelength, and NA Good reproduction is also possible.
(2) With respect to the difference in wavelength and the position of the light emitting point, a good signal can be obtained at the time of both DVD and CD reproduction.
(3) All three types of TE signal detection methods such as a phase difference method, a PP method, and a three beam method necessary for recording or reproducing a DVD-ROM, DVD-RAM, CD-ROM, and CD-R are the same. It can be implemented in the device.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an optical pickup according to a first embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view showing the operation of the optical pickup shown in FIG.
3 is a schematic cross-sectional view showing the operation of the optical pickup shown in FIG.
4 is a cross-sectional view of a diffraction grating used in the optical pickup shown in FIG.
FIG. 5 is a schematic cross-sectional view showing the operation of the optical pickup in the second embodiment.
FIG. 6 is a schematic sectional view showing the operation of the optical pickup in the second embodiment.
FIG. 7 is a schematic perspective view showing a photodetector in the third embodiment.
FIG. 8 is a schematic plan view showing the configuration and operation of a photodetector in the third embodiment.
9 is a diagram for explaining the operation of the photodetector in Embodiment 3. FIG.
FIG. 10 is a schematic plan view showing the operation of the photodetector in the third embodiment.
11 is a schematic plan view showing the configuration and operation of the photodetector in Embodiment 4. FIG.
12 is a schematic plan view showing the operation of the photodetector in Embodiment 4. FIG.
FIG. 13 is a schematic plan view showing the configuration and operation of the photodetector in the fifth embodiment.
FIG. 14 is a schematic plan view showing the operation of the photodetector in the fifth embodiment.
FIG. 15 is a schematic plan view showing a hologram configuration in the sixth embodiment.
FIG. 16 is a schematic cross-sectional view of an optical disc device according to a seventh embodiment.
FIG. 17 is a flowchart showing the procedure of an optical disc type recognition method according to the eighth embodiment.
FIG. 18 is a schematic sectional view of a copying machine according to a ninth embodiment.
FIG. 19 is a schematic cross-sectional view of a video projector according to Embodiment 10.
FIG. 20 is a schematic cross-sectional view of a conventional optical pickup.
FIG. 21 is a schematic perspective view showing a main part of a conventional optical pickup.
[Explanation of symbols]
1 Laser light source
1a Red laser
1b Infrared laser
2 Red light beam
3 Diffraction grating
4 Hologram
6 Objective lens
7 Optical disc
8 Photodetector
10, 12 + 1st order diffracted light
11, 13-1st order diffracted light
16 units
20 Optical pickup
25 Infrared light beam
30 Optical disk device
50 copier
62 Windshield

Claims (12)

An optical disc type recognition method for discriminating whether or not an optical disc exists in an optical disc apparatus and the type of the existing optical disc,
The optical disc apparatus includes a first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2 longer than the wavelength λ1 , and the first and second semiconductors. A condensing optical system that receives a light beam emitted from a laser light source and converges it onto a small spot on an optical disk, a diffracting means that diffracts the light beam reflected by the optical disk, and each diffracted light diffracted by the diffracting means. ; and a light detector for outputting an electrical signal in response to the light quantity Te,
The light detection unit receives a + 1st order diffracted light from the diffracting unit, and a light detection unit PD0 that receives the + 1st order diffracted light of the light beam having the wavelength λ1 among the diffracted light diffracted by the diffracting unit. Part PD1, and light detection part PD2 which receives -1st order diffracted light of the light beam of the above-mentioned wavelength lambda 2 ,
The distance between the center of the PD0 and the PD1 is d1, where d1 and d2 are the distances between the center of the light detection unit PD0 and the light emitting points of the first and second semiconductor laser light sources, respectively . The distance between the centers of PD0 and PD2 is formed at a distance twice as large as d2, and λ1 / λ2 = d1 / d2
Is substantially satisfied with the relationship
After the optical disk device is turned on or after a new optical disk is mounted on the optical disk device, the second semiconductor laser light source is caused to emit light, and the presence / absence of the optical disk is determined using the light beam having the wavelength λ2. An optical disc type recognition method characterized by discriminating and, when the optical disc is present, discriminating an optical disc type by using reflected light from the optical disc. The optical disc type recognition method according to claim 1, wherein the light beam having the wavelength λ1 is red light, and the light beam having the wavelength λ2 is infrared light. The optical disc type recognition method according to claim 1 or 2, wherein the second semiconductor laser light source emits light with substantially the same intensity as when the signal recorded on the optical disc is reproduced using the second semiconductor laser. If it is determined that the inserted optical disk is a CD, it continues to emit infrared light as it is to move to recording or reproduction of information, and if it is determined that the inserted optical disk is a DVD, the infrared light is 4. The optical disc type recognition method according to claim 2, wherein the DVD is recorded or reproduced by quenching and turning on red light. The diffracting means has a plurality of dividing lines in a direction perpendicular to the direction formed by the center of the light beam having the wavelength λ1 on the diffracting means and the center of the light beam having the wavelength λ2 on the diffracting means. The optical disc type recognition method according to any one of claims 1 to 4, wherein the optical disc type is recognized. The light detection unit PD1 and the light detection unit PD2 are each divided into a plurality of regions by dividing lines, and a symmetrical center line parallel to the dividing line of the light detection unit PD2 and the light detection unit PD1 of the light detection unit PD1. The optical disc type recognition method according to any one of claims 1 to 5 , wherein a symmetric center line parallel to the dividing line is shifted in a direction orthogonal to each symmetric center line . A first semiconductor laser light source that emits a light beam having a wavelength λ1, a second semiconductor laser light source that emits a light beam having a wavelength λ2 longer than the wavelength λ1, and the first and second semiconductor laser light sources. A condensing optical system that receives a light beam that converges on a small spot on the optical disc, a diffractive means that diffracts the light beam reflected by the optical disc, and receives each diffracted light diffracted by the diffracting means according to the amount of light An optical pickup comprising a light detection unit that outputs an electrical signal.
The light detecting unit receives a + 1st order diffracted light from the diffracting unit, and a light detecting unit that receives -1st order diffracted light of the light beam having the wavelength λ1 among the diffracted light diffracted by the diffracting unit. Part PD1, and light detection part PD2 which receives -1st order diffracted light of the light beam of the above-mentioned wavelength lambda 2,
The distance between the center of the PD0 and the PD1 is d1, where d1 and d2 are distances between the center of the light detection unit PD0 and the light emitting points of the first and second semiconductor laser light sources, respectively. Formed at a distance of twice, and the distance between the centers of PD0 and PD2 is set at a distance twice as large as d2.
λ1 / λ2 = d1 / d2
Is substantially satisfied with the relationship
After the optical disk device is turned on or after a new optical disk is mounted on the optical disk device, the second semiconductor laser light source is caused to emit light, and the presence / absence of the optical disk is determined using the light beam having the wavelength λ2. An optical disc apparatus comprising: discriminating and discriminating an optical disc type using reflected light from the optical disc when the optical disc exists. 8. The optical disc apparatus according to claim 7, wherein the light beam having the wavelength λ1 is red light, and the light beam having the wavelength λ2 is infrared light. 9. The optical disk device according to claim 7, wherein the second semiconductor laser light source emits light with substantially the same intensity as when a signal recorded on the optical disk is reproduced using the second semiconductor laser. If it is determined that the inserted optical disk is a CD, it continues to emit infrared light as it is to move to information recording or reproduction, and if it is determined that the inserted optical disk is a DVD, the infrared light is The optical disk apparatus according to claim 8 or 9, wherein the optical disk apparatus performs quenching and turning on red light to record or reproduce a DVD. The diffracting means has a plurality of dividing lines in a direction perpendicular to the direction formed by the center of the light beam having the wavelength λ1 on the diffracting means and the center of the light beam having the wavelength λ2 on the diffracting means. The optical disc device according to claim 7, wherein the optical disc device is formed. The light detection unit PD1 and the light detection unit PD2 are each divided into a plurality of regions by dividing lines, and a symmetrical center line parallel to the dividing line of the light detection unit PD2 and the light detection unit PD1. The optical disc apparatus according to any one of claims 7 to 11, wherein a symmetric center line parallel to the dividing line is shifted in a direction orthogonal to each symmetric center line.

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