JP2006351145A - Optical information recording medium and optical pickup device and optical memory device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a stabilized servo signal by compensating attenuation for a light flux circumference part produced in wavelength selection film. <P>SOLUTION: Transmittance of a wavelength selection film 5c varies in accordance with an incident angle. When light flux 8 for first wavelength vertically enters the wavelength selection film 5c as convergence light by an objective lens 11, the transmittance of the circumference part of the light flux 8 decreases, and light intensity distribution after transmitting the wavelength selection film 5c turns into the light intensity distribution to which the light intensity decreases in the circumference part of the light flux compared with prior to the transmittance. By means of a coupling lens and an optical element for compensating this attenuation, the light intensity in the outermost circumferential part is secured with 30% or more of the central light intensity, and a good servo signal is detected. Stabilized recording reproducing is performed by this servo signal. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an optical information recording medium, an optical pickup device, and an optical memory device that record information using holography.

  In recent years, information devices represented by personal computers (hereinafter referred to as personal computers) have been reduced in size, weight and price, and mobile personal computers are becoming increasingly popular. As a result, in order to meet the demands for downsizing, weight reduction, and cost reduction of optical disk devices, which are peripheral devices for personal computers, the downsizing and cost reduction of optical pickup devices, which are one of the components of optical disk devices. It is also widely distributed.

  The technology for recording information on an optical information recording medium using the holography used for this is generally such that light having image information and reference light are superimposed inside the recording medium, and interference fringes formed at that time are formed. This is done by writing to a recording medium. At the time of reproducing recorded information, the recording medium is irradiated with reference light, and is reproduced by diffraction by interference fringes.

  In order to perform stable servo detection on an optical information recording medium for recording information using this holography, for example, an optical information recording medium described in Patent Document 1 is shown in FIG. As described above, the lower substrate (transparent substrate) 1, the hologram recording layer 3 on which information is recorded by the interference pattern, and the lower substrate 1 and the hologram recording layer 3 are provided to transmit the first wavelength light beam, It comprises a filter layer (wavelength selection film) 5 that reflects the light beam of the second wavelength.

  According to this configuration, the filter layer 5 transmits a light beam having a first wavelength (for example, red light) and reflects a light beam having a second wavelength (for example, green light). Since it is possible to separate light beams of two types of wavelengths by this, it is disclosed that they are used for different purposes without being affected by each.

  Specifically, servo such as focusing and tracking is performed with red light that is a light beam with a first wavelength, and information is recorded and reproduced with green light that is a light beam with a second wavelength. This makes it possible to perform stable servo detection without affecting the recording layer on which information is recorded by the interference pattern, so that a servo system similar to a conventional optical disk can be used, and the recording capacity does not decrease. is there.

  In Patent Document 2, the interval t between the respective information recording surfaces is defined in the multilayer disc, and the reproduction level obtained when the reading light is on-focused on one of the information recording surfaces. On the other hand, the numerical aperture of the objective lens is set to NA, so that the reproduction level obtained when the reading light is defocused on another information recording surface of the information recording surface is 1/10 or less. The light source wavelength is λ, the refractive index between the information recording surfaces is n, the number of stacked layers is i, and the interval t is as follows

のように表されることが開示されている。
特開２００４−２６５４７２号公報 特許第３５６１７１１号公報 神谷武志，外78名，「光・薄膜技術マニュアル」，第１版，オプトロニクス社，平成元年10月９日，p.252

It is disclosed that they are expressed as follows.
JP 2004-265472 A Japanese Patent No. 3561711 Takeshi Kamiya, 78 others, “Optical / Thin Film Technology Manual”, 1st edition, Optronics, October 9, 1989, p.252

  However, the filter layer (wavelength selection film) that transmits the first wavelength light beam and reflects the second wavelength light beam described in Patent Document 1 has the following problems.

  The most effective method used as the wavelength selective film is to use a dielectric multilayer film. This dielectric multilayer film is an interference filter for extracting a specific wavelength by using interference of thin films stacked alternately. Such a dielectric multilayer film has an optical thickness of (Equation 2) where the refractive index is n, the optical path length is d, and the wavelength is λ0.

となる膜を重ねた構成となっているため、光路長ｄが変わってしまうと特定の波長を取り出す性能が劣化してしまう。

Therefore, if the optical path length d is changed, the performance of extracting a specific wavelength is deteriorated.

  Specifically, when convergent light is incident on the dielectric multilayer film, the light at the center of the light beam passes through the dielectric multilayer film almost vertically (θ = 0), whereas the light at the periphery of the light flux is Since the dielectric multilayer film is transmitted obliquely (θ ≠ 0), the optical path length is different from the designed original optical path length d. Therefore, when the light beam having the first wavelength is made incident on the dielectric multilayer film as convergent light, the transmittance of the light beam in the peripheral portion is lowered.

  In the configuration of Patent Document 1, since the light beam having the first wavelength passes through the dielectric multilayer film twice, the transmittance of the light around the light beam is significantly reduced. FIG. 13 shows the relationship between the incident angle and the transmittance (see Non-Patent Document 1). As shown in FIG. 13, a light beam is made incident at an angle of 30 ° (θ = 30) on a dielectric multilayer film designed to transmit light with a wavelength of 555 nm at nearly 100% when perpendicularly incident (θ = 0). And the transmittance | permeability will fall to about 20 to 35%.

  Therefore, when the convergent light from the objective lens having an NA of 0.65 is incident on the dielectric multilayer film, the light intensity distribution has a shape in which the intensity of the peripheral portion of the light beam is reduced. Furthermore, the light intensity distribution of the light beam reflected by the reflective layer having the servo pit pattern or the wobble groove and again transmitted through the dielectric multilayer film has a form in which the intensity at the peripheral portion is further lowered.

  If the light intensity distribution at the periphery of the light beam decreases, a sufficiently small spot cannot be formed on the surface with the servo pit pattern or wobble groove, or the push-pull signal decreases and a stable servo signal cannot be obtained. A malfunction will occur.

  The present invention is directed to solving the above-described problems of the prior art, and provides an optical pickup device and an optical memory device that can obtain a stable servo signal by correcting the attenuation of the peripheral portion of the light beam generated in the wavelength selection film. The purpose is to provide.

  In order to achieve the above object, an optical information recording medium according to claim 1 of the present invention is an optical information recording medium for recording information using holography, and has a servo pit pattern or wobble groove. A reflective layer, a recording layer on which information is recorded by an interference pattern, and a wavelength selection unit that is provided between the transparent substrate and the recording layer and transmits a light beam having a first wavelength from a light source and reflects a light beam having a second wavelength. And the wavelength selection film is made of a dielectric multilayer film, the transmittance of the first wavelength light beam can be increased, and the reflectance of the second wavelength light beam can be increased.

  The optical information recording medium described in claims 2 and 3 is the optical information recording medium according to claim 1, wherein the distance t between the wavelength selection film and the surface having the servo pit pattern or wobble groove is equal to that of the objective lens. Assuming that the numerical aperture is NA, the light source wavelength is λ, the refractive index between the surface having the servo pit pattern or wobble groove and the wavelength selection film is n, the following (Expression 3)

の条件を満たすこと、さらに、波長選択膜を透過する第１波長の光束が、波長６５０±５ｎｍの赤色光であることよって、サーボピットパターンまたはウォブル溝の面と波長選択膜の間隔を一定の間隔より大きくして波長選択膜を反射した第１波長の光がフレアとして受光素子に影響を及ぼすことがなく、さらに、第１波長をＤＶＤと同じ６５０ｎｍとすることで、ホログラム記録層を感光させることなく、かつ従来の回路構成を利用でき、安定したサーボ信号を得ることができる。

In addition, since the first wavelength light beam transmitted through the wavelength selective film is red light having a wavelength of 650 ± 5 nm, the distance between the surface of the servo pit pattern or wobble groove and the wavelength selective film is constant. The light having the first wavelength that is larger than the interval and reflected from the wavelength selection film does not affect the light receiving element as a flare, and the hologram recording layer is exposed by setting the first wavelength to 650 nm, which is the same as DVD. In addition, a conventional circuit configuration can be used and a stable servo signal can be obtained.

  According to a fourth aspect of the present invention, there is provided an optical pickup device that couples the optical information recording medium according to any one of the first to third aspects, a plurality of light sources having different wavelengths, and light emitted from at least one light source. Light that has an objective lens that is captured by a ring lens and irradiates the optical information recording medium and a light receiving element that receives reflected light from the optical information recording medium, and performs recording, erasing, or reproducing information on the optical information recording medium A wavelength selection film comprising a pickup device, comprising: means for correcting attenuation of light intensity generated in a peripheral portion of a light beam when the light beam having a first wavelength from the light source is transmitted through the wavelength selection film of the optical information recording medium. The light intensity distribution in the light beam having the first wavelength that passes through the light can be increased in intensity at the peripheral portion, and a good spot can be obtained on the surface of the servo pit pattern or wobble groove.

  The optical pickup device according to claim 5 is the optical pickup device according to claim 4, wherein the first wavelength is the same as that of the DVD by the configuration in which the light beam having the first wavelength is red light having a wavelength of 650 ± 5 nm. By setting the thickness to 650 nm, the conventional circuit configuration can be used without exposing the hologram recording layer.

  The optical pickup device according to claims 6 and 7 is the optical pickup device according to claims 4 and 5, wherein the correcting means adjusts the light intensity at the outermost peripheral portion of the first wavelength light beam emitted from the light source. By reducing the light intensity in the peripheral part due to the transmission of the wavelength selective film, the light intensity at the central part is larger than 30% of the light intensity, and the correction means is a coupling lens that takes in the light beam of the first wavelength emitted from the light source. In addition, a good spot can be formed on the surface of the servo pit pattern or the wobble groove, the push-pull signal can be prevented from being lowered, and a good spot can be obtained at the same time as a good servo signal.

  Further, the optical pickup device according to any one of claims 8 to 10 is the optical pickup device according to claims 4 to 6, wherein the correcting means is disposed between the optical paths for guiding the first wavelength light beam emitted from the light source to the objective lens. The optical element that changes the light intensity distribution of the light beam, the optical element has a light transmittance greater than that of the central part, and the optical element has a polarization direction that transmits the light beam. Due to the different configurations in the central part and the peripheral part, a good spot can be formed on the surface of the servo pit pattern or the wobble groove, and the decrease of the push-pull signal can be suppressed.

  Further, the optical memory device according to claim 11 can obtain an optical memory device capable of highly reliable servo control by the configuration in which the optical pickup device according to any one of claims 4 to 10 is mounted. .

  According to the present invention, it is possible to correct a decrease in light intensity generated in the peripheral portion of the light beam by transmitting through the wavelength selection film, and to form a good spot on the surface of the servo pit pattern or the wobble groove of the reflective layer. It is possible to suppress the drop of the push-pull signal for detecting the signal and to perform stable recording and reproduction.

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

  FIG. 1 is a diagram showing a schematic configuration of an optical information recording medium according to Embodiment 1 of the present invention. Here, components having substantially the same functions corresponding to the components described in FIG. 12 showing the conventional example are denoted by the same reference numerals.

  In the optical information recording medium 10 shown in FIG. 1, 1 is a lower substrate of a transparent substrate, 2 is a reflective layer on which servo pit patterns or wobble grooves are formed, 3 is a hologram recording layer for recording information, and 4 is a cover layer. The upper substrate, 5 is a filter layer, 5a is a gap A layer, 5b is a gap B layer, and 5c is a wavelength selection film. Reference numeral 8 denotes a first wavelength light beam, 9 denotes a second wavelength light beam, and 11 denotes an objective lens. 2A shows a state in which a light beam having the first wavelength is incident on the optical information recording medium. FIG. 2A shows a state before transmission through the wavelength selection film, FIG. 2B shows a case after transmission through the wavelength selection film, and FIG. It is a figure which shows the light intensity of the light beam after having been reflected and transmitted through the wavelength selection film again.

  The first embodiment will be described with reference to FIGS. In the optical information recording medium shown in FIG. 1, the optical information recording medium 10 is irradiated with the light beam 8 having the first wavelength (λ1 = 650 nm) and the light beam 9 having the second wavelength (λ2 = 532 nm) which are converged by the objective lens 11. Consider the case.

  The light beam 8 having the first wavelength passes through the upper substrate (cover layer) 4, the hologram recording layer 3, the gap A layer 5a, the wavelength selection film 5c, and the gap B layer 5b, and is reflected with a servo pit pattern or wobble groove formed. Focused on layer 2. The reflective layer 2 is provided with a reflective film, and the reflected light beam 8 having the first wavelength (λ1 = 650 nm) reads the servo pit pattern or wobble groove information of the reflective layer 2 to obtain the gap B layer 5b. The wavelength selection film 5c, the gap A layer 5a, the hologram recording layer 3, and the upper substrate 4 are returned. Servo signals such as a focus signal and a track signal are obtained by this light beam, and it is possible to know at which position on the optical information recording medium 10 the information is recorded.

  On the other hand, the light beam 9 having the second wavelength (λ2 = 532 nm) passes through the upper substrate 4, the hologram recording layer 3, and the gap A layer 5a and is reflected by the wavelength selection film 5c. The light reflected by the wavelength selection film 5c returns to the gap A layer 5a, the hologram recording layer 3, and the upper substrate 4, and is recorded and reproduced by receiving light with a CCD or CMOS sensor (not shown). Can do.

  At the time of data recording, information light and reference light are irradiated, and information is recorded on the hologram recording layer 3. Further, at the time of data reproduction, reference light is irradiated and data recorded on the hologram recording layer 3 is reproduced.

  As described above, since the light beam 8 having the first wavelength (λ1 = 650 nm) and the light beam 9 having the second wavelength (λ2 = 532 nm) can be completely separated by the wavelength selection film 5c, the light beam having the first wavelength (λ1 = 650 nm) can be obtained. A servo signal can be obtained from the light beam 8, and a recording / reproducing signal can be obtained from the light beam 9 having the second wavelength (λ2 = 532 nm). Therefore, the optical information recording medium 10 that records information using holography can handle information in the same manner as a conventional optical disc (BD (Blu-ray Disc), HD-DVD, DVD, CD, etc.).

  However, the wavelength selection film 5c has the above-described drawback that the transmittance varies depending on the incident angle. When the light beam 8 having the first wavelength becomes convergent light by the objective lens 11 and is vertically incident on the wavelength selection film 5c, the transmittance of the peripheral portion of the light beam 8 decreases, so the light intensity distribution after passing through the wavelength selection film 5c is The intensity distribution is such that the light intensity is reduced at the periphery of the light beam compared to before transmission (see FIG. 2B). When the light is further reflected by the reflective film of the reflective layer 2 and transmitted through the wavelength selection film 5c again, the light intensity distribution becomes an intensity distribution in which the light intensity at the peripheral portion is further reduced (see FIG. 2C).

  Since the light beam is separated by the above-described wavelength selection film, the transmittance of the light in the peripheral portion of the light beam is remarkably reduced. Similarly to the relationship between the incident angle and the transmittance shown in FIG. When a dielectric multilayer film that transmits nearly% is formed and a light beam is incident at an angle of 30 °, the transmittance is reduced to about 20 to 35%.

  If the light intensity at the periphery of the luminous flux is reduced, a good spot cannot be formed on the servo pit pattern or the reflection layer 2 of the wobble groove, or the push-pull signal component becomes small when detecting the servo signal. This causes a problem that stable signal detection cannot be performed (see FIGS. 3A and 3B).

  The amount of decrease in the light intensity at the periphery of the luminous flux is 30% or more of the center light intensity as the light intensity at the outermost periphery in accordance with the DVD system when using light of λ1 = 650 nm (Strength: Rim 30% or more), it is considered that a good signal can be secured.

A semiconductor laser (λ1 = 650 nm) as a light source has an elliptical intensity distribution, and the intensity distribution is brighter at the center and becomes darker toward the periphery, and the light intensity (brightness) at the center is 100%. The outermost light intensity (brightness) is 0%.
In order to use light from this light source without waste, a state where a coupling lens having a size capable of capturing even the outermost light is Rim 0%, and light having such an intensity distribution is applied to an optical disk by an objective lens. When the light is focused on, the intensity distribution of the focused spot becomes a spot where the central part is strong (100%) and the peripheral part is weak (0%), and there is uneven intensity of light in the spot. When recording data on the camera, it becomes impossible to record cleanly. In order to record data neatly, it is necessary that the intensity distribution of the focused spot has the same intensity at both the central part and the peripheral part.

  For this reason, there is a contradiction between using light from the light source without waste and recording the data neatly. As a condition obtained to satisfy both conditions, the light from the light source is not wasted and the data is saved. We sought experimentally the conditions that can record beautifully. The result is Rim 30% or more.

  Therefore, the light beam incident on the objective lens is light with the light intensity at the outermost peripheral portion being the center so that the light intensity at the outermost peripheral portion of the light flux after passing through the wavelength selection film can ensure 30% or more of the light intensity at the central portion What is necessary is just to enter the light beam larger than 30% of intensity | strength.

  For this purpose, the focal length of the coupling lens 14 that takes in the emitted light from the light source of the first wavelength may be increased as in the optical pickup device shown in FIG. As an example, FFP (Far Field Pattern) indicating an elliptical intensity distribution of the light source 12 which is a semiconductor laser is 10 ° in the horizontal direction and 20 ° in the vertical direction (θ // = 10 °, θ⊥ = 20). In the case of (°), if the focal length of the coupling lens 14 is 20 mm, the light intensity at the outermost peripheral portion is 42% of the light intensity at the center. By making this light beam incident on the wavelength selection film 5c, it is possible to secure Rim 30% or more even if the light intensity in the peripheral portion is lowered.

  5A is a front view, FIG. 5B is a side view, and FIG. 5C is a diagram showing input / output characteristics of a configuration example of an optical element according to Embodiment 2 of the present invention. In the first embodiment described above, it has been shown that a light beam having a high light intensity at the periphery of the light beam may be incident on the objective lens 11 in advance for the wavelength selection film whose transmittance varies depending on the incident angle. As a second embodiment, a configuration of an optical pickup device including an optical element that reduces the light intensity at the central portion and improves the light intensity at the peripheral portion is proposed.

  The optical element 18a shown in FIG. 5 is an ND (Neutral Density) filter in which the transmittance at the center is small and the transmittance increases at the periphery. When the light beam is transmitted through such an optical element 18a, the light intensity is weakened in the central part, and the peripheral part is transmitted without being weakened. As a result, a light beam having a light intensity distribution with a stronger intensity at the periphery than at the center (light intensity distribution indicated by a broken line in FIG. 5C), and the transmittance of the light beam at the periphery was lowered by the wavelength selection film. However, the light intensity at the outermost peripheral portion can be 30% or more of the light intensity at the center.

  As another example of the optical element, FIG. 6A is a front view, FIG. 6B is a side view, and FIG. 6C is a diagram showing input / output characteristics. A polarizing filter may be used. A polarizing filter orthogonal to the polarization direction emitted from the light source blocks the light beam, but a polarizing filter parallel to the polarization direction transmits light. By utilizing this, if the direction of the polarizing filter is changed concentrically so that the transmittance at the central portion is small and the transmittance increases toward the peripheral portion, the light intensity at the central portion can be reduced. The optical element 18b, which reduces the light intensity at the central portion and improves the light intensity at the peripheral portion, is desirably disposed at a position where the light beam from the light source passes but the reflected light from the optical recording medium does not pass. For example, like the optical pickup device shown in FIG.

  Next, the light beam having the first wavelength that could not pass through the wavelength selection film will be described. Of the first wavelength light beam that should have been transmitted through the wavelength selective film, for example, the light beam 8 ′ having a large incident angle that cannot be transmitted is reflected by the wavelength selective film (see FIG. 8). ). The reflected light flux returns to the objective lens 11, returns to the optical system of the optical pickup device shown in FIG. Since this light beam is not the light reflected by the surface of the reflective layer 2 of the original servo pit pattern or wobble groove, it becomes flare light and adversely affects the signal. Therefore, it is desirable that the light beam 8 ′ reflected by the wavelength selection film 5 c is weakened as much as possible and enters the light receiving element 17.

  For this purpose, it is desirable that the distance t between the wavelength selection film 5c and the surface having the servo pit pattern or the wobble groove is separated. Since this is the same state as flare from a two-layer medium having two reflective layers, the distance between the wavelength selective film and the reflective layer is equal to the thickness of the intermediate layer disclosed in Patent Document 2. It is desirable to do.

  Specifically, the reproduction level at the time of defocus (light intensity reflected from the wavelength selection film) is, for example, 1/10 or less of the reproduction level at the time of on-focus (light intensity reflected from the reflection layer of the servo pit pattern or wobble groove). To achieve this, NA is the numerical aperture of the objective lens, λ is the light source wavelength, and n is the refractive index between the information recording surfaces, and the distance t between the wavelength selection film and the reflective layer is given by

のようにすればよい。なお、前述した波長選択膜と反射層との層間の距離ｔは大きいほど波長選択膜で反射された光束は弱められて受光素子に入ることになりフレアは小さくなるが、ホログラム記録層などの光情報記録媒体の構成に必要な領域を確保できる範囲とする。

Like this. As the distance t between the wavelength selective film and the reflective layer increases, the light beam reflected by the wavelength selective film is weakened and enters the light receiving element, and the flare is reduced. The area required for the configuration of the information recording medium can be secured.

  When the distance t between the wavelength selection film and the reflection layer is set to a certain value or more in this way, the light beam having the first wavelength reflected by the wavelength selection film has less light entering the light receiving element than the signal light. Signal degradation due to flare can be suppressed.

  FIG. 10 is a block diagram showing a schematic configuration of the optical memory device according to the third embodiment of the present invention. An optical memory device 20 shown in FIG. 10 includes a spindle motor 22, an optical pickup device 23, a laser control circuit 24, an encoder 25, a motor driver 26, a reproduction signal processing circuit 27, and the like for rotationally driving an optical disc 10 as an optical information recording medium. A servo controller 28, a buffer RAM 29, a buffer manager 30, an interface 31, a read only memory (ROM) 32, a central processing unit (CPU) 33, a random access memory (RAM) 34, and the like are provided. Note that the arrows in FIG. 10 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block.

  The optical pickup device 23 is a device for irradiating the optical disc 10 with laser light and receiving diffracted light from the recording surface to record or reproduce information. For example, although it demonstrated in each embodiment mentioned above, it has a structure like FIG.

  The reproduction signal processing circuit 27 converts a current signal that is an output signal of the optical pickup device 23 into a voltage signal, and based on the voltage signal, a wobble signal, an RF signal including reproduction information, and a servo signal (focus error signal, track error) Signal).

  Then, the reproduction signal processing circuit 27 extracts address information and a synchronization signal from the wobble signal. The address information extracted here is output to the CPU 33, and the synchronization signal is output to the encoder 25. Further, the reproduction signal processing circuit 27 performs error correction processing or the like on the RF signal and then stores it in the buffer RAM 29 via the buffer manager 30. The servo signal is output from the reproduction signal processing circuit 27 to the servo controller 28. The servo controller 28 generates a control signal for controlling the optical pickup device 23 based on the servo signal and outputs it to the motor driver 26.

  The buffer manager 30 manages input / output of data to / from the buffer RAM 29, and notifies the CPU 33 when the accumulated data amount reaches a predetermined value. The motor driver 22 controls the optical pickup device 23 and the spindle motor 22 based on a control signal from the servo controller 28 and an instruction from the CPU 33.

  The encoder 25 takes out the data stored in the buffer RAM 29 through the buffer manager 30 based on the instruction of the CPU 33, adds an error correction code, etc., creates the write data to the optical disc 10 and reproduces it. Write data is output to the laser control circuit 24 in synchronization with the synchronization signal from the signal processing circuit 27. The laser control circuit 24 controls the output of the laser light from the optical pickup device 23 based on the write data from the encoder 25.

  In the optical memory device 20 configured as described above, the optical pickup device described in each of the above-described embodiments transmits only the light beam having the first wavelength, and light that is greatly inclined from the vertical is incident on the wavelength selection film. Since it is configured to compensate for the deterioration of transmittance that sometimes occurs, by using this optical pickup device as appropriate, a good spot can be obtained on the surface of the reflective layer having a servo pit pattern or wobble groove and stable Thus, a highly reliable servo signal can be obtained. As a result, an optical memory device that performs stable recording and reproduction can be realized.

  An optical information recording medium, an optical pickup device, and an optical memory device according to the present invention correct a decrease in light intensity that occurs in a peripheral portion of a light beam by passing through a wavelength selection film, and provide a servo pit pattern or wobble groove surface of a reflective layer An optical information recording medium capable of forming a good spot on the surface, suppressing a decrease in push-pull signal for detecting a servo signal, performing stable recording and reproduction, and recording information using holography, and It is useful for an optical pickup device and an optical memory device to be used.

The figure which shows schematic structure of the optical information recording medium in Embodiment 1 of this invention (A) when the light beam is incident on the optical information recording medium, before transmission through the wavelength selection film, (b) after transmission through the wavelength selection film, (c) is reflected by the reflection layer and retransmitted through the wavelength selection film. Diagram showing light intensity FIG. 5A shows a light intensity distribution, a spot, and a push-pull signal when a spot is formed on a reflection layer of an incident light beam, FIG. The figure which shows schematic structure of the optical pick-up apparatus in this Embodiment 1. (A) of the structural example of the optical element in Embodiment 2 of this invention is a front view, (b) is a side view, (c) is a figure which shows the input-output characteristic. In the configuration example of another optical element in the second embodiment, (a) is a front view, (b) is a side view, and (c) is a diagram showing input / output characteristics. The figure which shows schematic structure of the optical pick-up apparatus which showed the example of arrangement | positioning of the optical element shown in FIG. The figure explaining the light beam which could not be permeate | transmitted in the transmitted light beam through a wavelength selection film | membrane The figure explaining the optical path in the optical pick-up apparatus of the light beam which could not permeate | transmit a wavelength selection film | membrane FIG. 3 is a block diagram showing a schematic configuration of an optical memory device according to a third embodiment of the present invention. FIG. 3 is a block diagram showing a schematic configuration of an optical pickup device used in the optical memory device according to the third embodiment. The figure which shows schematic structure of the conventional optical information recording medium The figure which shows the relationship between the incident angle of the light beam which permeate | transmits a dielectric multilayer, and the transmittance | permeability

Explanation of symbols

1 Lower substrate (transparent substrate)
2 Reflective layer 3 Hologram recording layer 4 Upper substrate (cover substrate)
5 Filter layer 5a Gap A layer 5b Gap B layer 5c Wavelength selection film 8 First wavelength beam 8 ′ First wavelength beam 9 reflected by wavelength selection film 9 Second wavelength beam 10 Optical information recording medium (optical disk)
DESCRIPTION OF SYMBOLS 11 Objective lens 12 Light source 13 Polarizing beam splitter 14 Coupling lens 15 Dichroic mirror 16 Detection lens 17 Light receiving element 18, 18a, 18b Optical element 20 Optical memory device 22 Spindle motor 23 Optical pick-up device 24 Laser control circuit 25 Encoder 26 Motor driver 27 Playback Signal processing circuit 28 Servo controller 29 Buffer RAM
30 Buffer manager 31 Interface 32 ROM
33 CPU
34 RAM

Claims (11)

An optical information recording medium for recording information using holography,
A reflective layer having a servo pit pattern or a wobble groove, a recording layer on which information is recorded by an interference pattern, a light beam having a first wavelength from a light source provided between the transparent substrate and the recording layer; A wavelength selective film that reflects light beams of two wavelengths,
The optical information recording medium, wherein the wavelength selection film comprises a dielectric multilayer film. The distance t between the wavelength selection film and the surface having the servo pit pattern or wobble groove is NA of the numerical aperture of the objective lens, λ the light source wavelength, and the space between the surface having the servo pit pattern or wobble groove and the wavelength selection film. Where n is the refractive index of the following (Equation 1)

The optical information recording medium according to claim 1, wherein the following condition is satisfied.   3. The optical information recording medium according to claim 1, wherein the first wavelength light beam transmitted through the wavelength selection film is red light having a wavelength of 650 ± 5 nm. The optical information recording medium according to any one of claims 1 to 3, a plurality of light sources having different wavelengths, and light emitted from at least one of the light sources is captured by a coupling lens and irradiated to the optical information recording medium. An optical pickup device that includes an objective lens and a light receiving element that receives reflected light from the optical information recording medium, and records, erases, or reproduces information on the optical information recording medium,
An optical pickup apparatus, comprising: means for correcting attenuation of light intensity generated in a peripheral portion of the light beam when the light beam having the first wavelength from the light source passes through the wavelength selection film of the optical information recording medium.   5. The optical pickup device according to claim 4, wherein the light beam having the first wavelength is red light having a wavelength of 650 ± 5 nm.   6. The optical pickup device according to claim 4, wherein the correcting means makes the light intensity at the outermost peripheral portion of the light beam having the first wavelength emitted from the light source larger than 30% of the light intensity at the central portion.   6. The optical pickup device according to claim 4, wherein the correcting means is a coupling lens that takes in a light beam having a first wavelength emitted from a light source.   7. The optical element for changing the light intensity distribution of the light beam provided between the optical paths for guiding the light beam having the first wavelength emitted from the light source to the objective lens. The optical pick-up apparatus of any one of Claims.   9. The optical pickup device according to claim 8, wherein the optical element makes the light transmittance of the light beam larger in the peripheral part than in the central part.   9. The optical pickup device according to claim 8, wherein the optical element has different polarization directions for transmitting a light beam between a central portion and a peripheral portion.   An optical memory device comprising the optical pickup device according to claim 4.

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