JP2006244594A - Optical information recording and reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer optical disk recording and reproducing apparatus which can improve focal detection sensitivity and resolution. <P>SOLUTION: The optical disk recording and reproducing apparatus is provided with three pinhole filters arranged in the vicinity of the focal points of return light which is obtained by dividing return light from a recording medium into three beams and converging them respectively, and a photodetector arranged in rear of the pinhole filters for detecting light from the pinhole filters. One of the positions of the opening parts of the three pinhole filters serves as the position of the focal point of the return light, and one of the other is arranged with a prescribed distance forward or backward from the focal point position of the return light to detect a focal point error signal from the differential output of the photodetector. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical information recording / reproducing apparatus having a light source, an optical system, and a light spot position control device for recording and reproducing information by irradiating a recording medium with a light spot, and in particular, improves focus detection sensitivity and resolution. The present invention relates to an optical information recording / reproducing apparatus suitable for recording / reproducing a three-dimensional multilayer optical disc.

2. Description of the Related Art Generally, an optical information recording / reproducing apparatus having a light source, an optical system, and a light spot position control device for irradiating a recording medium with a light spot to perform information recording / reproducing is known.
An example of a conventional optical information recording / reproducing apparatus will be described with reference to FIG.
FIG. 7 is a schematic configuration diagram of an example of a conventional optical information recording / reproducing apparatus.
As shown in FIG. 7, this conventional optical information recording / reproducing apparatus has a semiconductor laser 80 as a light source, and the emitted light emitted from the semiconductor laser 80 is converted into parallel light by a collimator lens 81. A polarizing beam splitter 82 for separating the outgoing light and the reflected light, and a quarter-wave plate 83 for rotating the polarization plane of the light to enable separation of the outgoing light and the reflected light at the polarizing beam splitter 82. And is condensed on the optical disc medium 85 by the condenser lens 84.
The reflected light from the optical disk medium 85 is collimated by the condenser lens 84, passes through the quarter-wave plate 83, is separated from the optical path of the emitted light by the polarization beam splitter 82, and is half prism 86. Head for. In the half prism 86, a part of the reflected light is separated as light for detecting an error signal in the focus tracking control, and the separated light is condensed on the photodetector 88 by the detection lens 87, and there. A focus error signal and a tracking error signal for focus tracking control are detected.
On the other hand, the remaining light passing through the half prism 86 is again focused by the focusing lens 89 and passes through a pinhole region (light transmission region) 90A of the pinhole filter 90 formed integrally with the focusing lens 89. , Enters the photodetector 91. The photodetector 91 generates a reproduction signal based on this incident light.
In this prior art, only a high-resolution light beam transmitted through the pinhole region (light transmission region) 90A is used as a detection signal.
As a prior art, as Patent Document 1, a light source, a photodetector that generates a predetermined signal based on received light, and a light beam emitted from the light source are collected and applied to a predetermined reflecting member. An optical head comprising a condensing optical system for irradiating and a reproducing optical system that guides reflected light from the predetermined reflecting member to the photodetector, and the reproducing optical system focuses the light at a predetermined focusing point. A step of providing a film of a predetermined material in the vicinity of the focusing point, and irradiating the film of the predetermined material with light focused through at least a part of the reproducing optical system. And a step of forming a filter having a light transmission region that selectively transmits a portion in the vicinity of the center of the focused light.
Japanese Patent Laid-Open No. 10-340468

However, in the above prior art, since the focus servo method uses the normal astigmatism method, when the layer spacing of the reflective layer is reduced in a multilayer disk, the range of the S-curve must be less than the layer spacing. In other words, the sensitivity is relatively poor.
The present invention has been made to solve the above-described conventional problems, and an object thereof is to provide an optical information recording / reproducing apparatus suitable for recording / reproducing of a three-dimensional multilayer optical disc capable of improving focus detection sensitivity and resolution. That is.

In order to achieve the above-mentioned object, the invention described in claim 1 is an optical information recording / reproducing apparatus that records and reproduces information by irradiating a recording medium with a light spot, and at least returns light from the recording medium. At least three pinhole filters arranged in the vicinity of the focal point of the return light divided into three and converged, and a photodetector arranged behind the pinhole filter to detect light from the pinhole filter Wherein one of the positions of the openings of the at least three pinhole filters is the focal position of the return light, and the positions of the openings of the other pinhole filters are the focal positions of the return light. The at least three pinhole filters are arranged so as to be separated from each other by a predetermined distance in front of and behind, and are separated from the focal position of the return light by the predetermined distance. A differential output of the photodetector which is arranged behind the other of the pinhole filter, and detects a focus error signal of the light spot.
According to a second aspect of the present invention, there is provided an optical information recording / reproducing apparatus for recording / reproducing information by irradiating a recording medium with a light spot, wherein the return light from the recording medium is divided into at least three parts and converged respectively. At least three pinhole filters arranged near the focal point of the returned light and having a reflecting surface around the opening, and the pinhole for detecting light from the pinhole filter Two types of photodetectors arranged in front and rear of the filter, respectively, the positions of the openings of the at least three pinhole filters, one being the focal position of the return light, and the other The at least three pinhole filters are arranged so that the position of the opening of the pinhole filter is a predetermined distance before and after the focal position of the return light. And detecting a focus error signal of the light spot from a differential output of the photodetector arranged behind the other pinhole filter arranged at a predetermined distance from the focal position of the return light. In addition, the photodetector arranged in front is divided into two, and a tracking error signal is detected by taking a differential of each of the two-divided photodetectors.

The invention according to claim 3 is the optical information recording / reproducing apparatus according to claim 1 or 2, wherein the photodetector disposed behind the pinhole filter at the focal position of the return light, and the return Calculate the number of reflecting surfaces through which the light spot passes from the differential output with the average output of the two detectors placed behind the two pinhole filters placed a predetermined distance away from the focal position of the light It is characterized by doing.
According to a fourth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the first to third aspects, a grating is used as means for dividing the return light from the recording medium into three. It is characterized by that.
According to a fifth aspect of the invention, in the optical information recording / reproducing apparatus according to the fourth aspect, a double grating is used as means for dividing the return light from the recording medium into three.
According to a sixth aspect of the present invention, in the optical information recording / reproducing apparatus according to any one of the first to fifth aspects, the pinhole filter has a projecting reflecting surface around the opening. It is characterized by.
According to a seventh aspect of the present invention, in the optical information recording / reproducing apparatus according to the sixth aspect, an opening is provided in the center of the two-divided photodetector on the front surface of the pinhole filter, and the return light is collected in the opening. The light beam is arranged so as to pass therethrough.
Further, in the optical information recording / reproducing apparatus according to any one of claims 1 to 6, a high-output light source is used as the recording light source and the recording wavelength is ½ of a recording wavelength. Recording is performed on a recording medium having a multilayer structure with energy corresponding to a wavelength.

According to the present invention, at least three pinhole filter opening positions are one of the return light focal positions, and the other pinhole filter opening positions are the return light focal positions. The at least three pinhole filters are arranged so as to be separated from each other by a predetermined distance before and after the other pinhole filter arranged at a predetermined distance from the focal position of the return light. Since the focus error signal of the light spot is detected from the differential output of the arranged photodetector, only the high-resolution light beam passing through the pinhole filter in the depth direction is used as the detection signal. Thus, an optical information recording / reproducing apparatus suitable for three-dimensional optical recording / reproducing can be obtained in which focus servo can be applied to each of a plurality of reflective layers having a narrow interval. It is.
According to the present invention, one of the positions of the openings of the at least three pinhole filters is the focal position of the return light, and the positions of the other openings of the pinhole filter are the positions of the return light. The at least three pinhole filters are arranged so as to be at a predetermined distance before and after the focal position, and the other pinhole filters arranged at a predetermined distance from the focal position of the return light. The focus error signal of the light spot is detected from the differential output of the photodetector arranged at the rear, and the photodetector arranged at the front is divided into two, each of the two-divided photodetectors Therefore, in addition to the above effects, the tracking error signal can be accurately detected.

According to the present invention, in addition to the above-described effects, when the light spot moves in the vertical direction on a plurality of reflecting surfaces, the photodetector disposed behind the pinhole filter at the focal position of the return light And a reflection surface through which a light spot passes from the differential output of the average output of two detectors arranged behind two pinhole filters arranged at a predetermined distance from the focal position of the return light Can be calculated.
Further, according to the present invention, in addition to the above-described effects, the use of a grating as means for dividing the return light from the recording medium into three makes it possible to make the return light split compact and to make the entire apparatus compact. Can be.
Further, according to the present invention, in addition to the above-described effects, the use of double gratings can prevent fluctuations in the focal position even when the light source has wavelength fluctuations, thereby reducing the intensity of the photodetector. Is avoided, and the stability of the optical system is improved.
According to the present invention, in addition to the above-described effects, the pinhole filter has a projection-like reflection surface around the opening, so that the pinhole filter having the reflection surface is connected to the optical axis of the return light. The plurality of photodetectors on the front surface of the pinhole filter can be arranged at an optimum position apart from the optical axis of the return light. Therefore, the arrangement of the pinhole filter and the zero point adjustment of the tracking error signal are facilitated, and the degree of freedom of the entire arrangement of the optical system is increased, so that each element can be arranged spatially and efficiently.
Further, according to the present invention, in addition to the above-described effects, an opening is provided in the central portion of the two-divided photodetector on the front surface of the pinhole filter, and the return light condensing beam is disposed therethrough. Therefore, the pinhole filter having a reflecting surface can be arranged substantially perpendicular to the optical axis of the return light, and the arrangement of the pinhole filter and the zero adjustment of the tracking error signal are facilitated. Also, the overall arrangement of the optical system can be made compact.
Further, according to the present invention, in addition to the above-described effects, a high-output light source is used as the recording light source, and recording is performed on a recording medium having a multilayer structure with energy corresponding to a half wavelength of the recording wavelength. Therefore, since recording can be performed shallower in the depth direction at the time of recording, the repeated layer spacing can be further reduced in the multilayer structure in which the recording medium and the reflective layer are combined.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
(Example)
FIG. 1 is a schematic diagram of a first embodiment relating to the main part of an optical information recording / reproducing apparatus according to the present invention.
As shown in FIG. 1, this optical information recording / reproducing apparatus has a light source 1, and light emitted from the light source 1 passes through a condenser lens 2, a polarization beam splitter 3, and a quarter wavelength plate 4. The light is condensed into the three-dimensional recording medium 6 by the objective lens 5. The reflected light from the three-dimensional recording medium 6 passes through the objective lens 5 and the quarter wavelength plate 4 and is reflected by the polarization beam splitter 3, and is divided into three by the beam splitters 7A and 7C. The light passes through the condenser lenses 8A, 8B, and 8C and the pinhole filters 9A, 9B, and 9C and is irradiated onto the photodetectors 10A, 10B, and 10C.
In addition, the light detection output of each photodetector 10A, 10B, 10C is sent to the light spot position control apparatus 20, and the position control of a light spot is performed based on it.
Here, the pinhole filters 9A, 9B, and 9C are arranged so as to come to the approximate focal positions of the condenser lenses 8A, 8B, and 8C, respectively. It is essential that the aperture of each pinhole filter is as small as the diameter of the focused beam of the focusing lens.

The pinhole filters 9A, 9B, and 9C are arranged such that the positions of the openings are different from the focal positions of the condenser lenses 8A, B, and C, respectively. That is, in the embodiment shown in FIG. 1, the opening of the pinhole filter 9B is correctly arranged at the condensing position of the condensing lens 8B, whereas the pinhole filter 9A has the opening. Is disposed slightly rearward of the condensing position of the condensing lens 8A. On the contrary, the opening of the pinhole filter 9C is disposed slightly forward of the condensing position of the condensing lens 8C. ing. That is, one of the positions of the openings of the three pinhole filters 9A, 9B, and 9C is the focal position of the return light, and the positions of the openings of the other pinhole filters are the focal positions of the return light. The at least three pinhole filters are arranged so as to be located at a predetermined distance before and after.
In such an arrangement of the pinhole filters 9A, 9B, 9C, the amount of light transmitted through the opening of the pinhole filter 9B is maximized as compared to other cases. That is, if the output of the photodetector 10B is B, B is the maximum.
In comparison, the light passing through the pinhole filters 9A and 9C is slightly shifted from the condensing position of the condensing lens, so that a part of the light is transmitted through the pinhole filters 9A and 9C. , 9C, and the amount of transmitted light decreases. That is, the outputs A and C of the photodetectors 10A and 10C are smaller than the output B of the photodetector 10B.

Here, FIG. 2 shows the relationship between the position of each pinhole filter in the optical axis direction of the corresponding condensing lens and the output of each photodetector.
In FIG. 2, A, B, and C on the horizontal axis indicate the positions of the pinhole filters 9A, 9B, and 9C. The dotted lines of the positions A, B, and C on the vertical axis and the three states described below. The intersections with the solid line graphs 1, 2, and 3 represent the outputs of the photodetectors 10A, 10B, and 10C.
FIG. 2 shows three states 1, 2, and 3 based on the relationship between the position of the beam by the condenser lens on the reflection surface of the three-dimensional recording medium 6 and the positions of the pinhole filters 9A, 9B, and 9C. It is shown.
That is, in FIG. 2, the state 1 indicates the light detection output in a state where the reflection surface of the three-dimensional recording medium 6 is in front of the reference position of the light detection device (upper side in FIG. 1). The light detection outputs of the photodetectors 10A, 10B, and 10C at the positions A, B, and C of the filters 9A, 9B, and 9C are represented by □.
In FIG. 2, a state 2 indicates a light detection output in a state where the reflection surface of the three-dimensional recording medium 6 is at the reference position of the light detection device, and each position A, B of the pinhole filters 9A, 9B, 9C. , C, the photodetection outputs of the photodetectors 10A, 10B, and 10C are represented by ◯.
In FIG. 2, a state 3 indicates a light detection output in a state where the reflection surface of the three-dimensional recording medium 6 is behind (lower side in FIG. 1) with respect to the reference position of the light detection device. The light detection outputs of the photodetectors 10A, 10B, and 10C at the positions A, B, and C of 9A, 9B, and 9C are represented by Δ.
Here, when the light detection outputs of the light detectors 10A, 10B, and 10C are a, b, and c, the focus error signal SE is given by SE = ac. If the outputs of the optical system and the photodetector are adjusted so that SE = 0 at the time of focusing, the focal position can be determined by the sign of SE. The determination of the focal position and the position control of the light spot based on the focus error signal SE are performed by the light spot position control device 20.
That is, as shown in FIG. 2, in the state 2 (at the time of focusing), if the adjustment is made so that SE = 0, for example, the reflection surface of the three-dimensional recording medium 6 is the reference of this photodetection device. In the case of the state 1 that is in front of the position (upper side in FIG. 1), SE> 0, and the reflecting surface of the three-dimensional recording medium 6 is behind (lower in FIG. In state 3 on the side), SE <0.
Therefore, accurate position control of the light spot can be performed by the sign and value of the SE. In other words, the focus error signal SE is obtained from the differential output of the photodetector behind the other pinhole filter arranged by a predetermined distance from the focal position of the return light from the reflecting surface of the three-dimensional recording medium 6 at a predetermined distance. Since the position of the light spot is accurately controlled based on the focus error signal SE, the three-dimensional light that can apply the focus servo to each of the plurality of reflection layers with a narrow interval is obtained. An optical information recording / reproducing apparatus suitable for recording / reproducing can be obtained.

The recording signal S is detected as S = a + b + c. When the reflectance changes on the reflecting surface of the three-dimensional recording medium 6, the value of S varies, but the recording signal S can be detected by the above method. Further, with respect to each pinhole filter 9A, 9B, 9C, it is only necessary to maintain the positional relationship described above with respect to the condensing position of each condensing lens 8A, 8B, 8C, and each pinhole filter 9A, 9B and 9C are interchangeable. Moreover, as a material of the photodetector 10, a semiconductor detector such as Si or Ge can be applied, but other materials may be used. Further, the pinhole filter 9 is an object provided with an opening in a light shielding material, and a part of the light shielding material may be transparent even if it is a hole.
Further, when SC = (a + c) / 2−b is used as an inter-layer count signal, as shown in FIG. 2, the reference of the photodetectors 10A, 10B, and 10C of the pinhole filters 9A, 9B, and 9C is used. By changing the relative position with respect to the position, the SC value changes to ± every time the reference positions of the photodetectors 10A, 10B, and 10C pass vertically through the reflective layer of the three-dimensional recording medium 6. Therefore, if the number of ± changes in this value is counted, the number of layers through which the condensing spot passes vertically through the reflective layer of the three-dimensional recording medium 6 can be counted.
That is, here, the photodetector arranged behind the pinhole filter at the focal position of the return light and the two pinhole filters arranged apart from the focal position of the return light by a predetermined distance are arranged. The number of reflecting surfaces through which the light spot passes is calculated from the differential output with the average output of the two detectors.

Next, a second embodiment will be described.
FIG. 3 is a schematic view of a second embodiment relating to the main part of the optical information recording / reproducing apparatus according to the present invention.
The second embodiment of FIG. 3 has substantially the same configuration and operation as the first embodiment described in FIG. 1, and only the configuration and operation of the pinhole filters 19A, 19B, and 19C are different.
That is, in each pinhole filter 19A, 19B, 19C of the second embodiment, the periphery of the pinhole filter opening on the front surface is a reflective surface instead of the light shielding surface, and each condensing lens 8A , 8B, 8C are slightly inclined with respect to the optical axis. For this reason, of the light incident on the pinhole filters 19A, 19B, and 19C from the condenser lenses 8A, 8B, and 8C, the light does not pass behind the pinhole filters 19A, 19B, and 19C, but is reflected around it. There is light, and these lights avoid the light fluxes of the respective condensing lenses 8A, 8B, and 8C, and are respectively divided into the two-split photodetectors 11A, 12A, which are disposed in front of the pinhole filters 19A, 19B, and 19C. Detected by 11B, 12B, 11C, and 12C, respectively. The light transmitted through each pinhole filter 19A, 19B, 19C is irradiated and detected on each photodetector 10A, 10B, 10C.
Therefore, the focal point of the light spot is obtained from the differential output of the photodetectors 10A and 10C arranged behind the other pinhole filters 19A and 19C arranged at a predetermined distance from the focal position of the return light. An error signal SE is detected.
Here, the outputs of the two-split photodetectors 11A, 12A, 11B, 12B, 11C, and 12C are a1, a2, b1, b2, c1, and c2, respectively, and the difference between the split-split photodetectors 11A and 12A, When the difference between 11B and 12B and the difference between 11C and 12C are SA, SB, and SC, respectively, SA = a1-a2, SB = b1-b2, and SC = c1-c2.

Here, when a push-pull groove is provided on the reflection surface inside the three-dimensional recording medium 6, it is possible to detect a change in the intensity distribution of the light beam caused by the diffraction.
That is, when the tracking error signal is TE, the tracking error signal TE can be obtained by TE = SA + SB + SC = (a1 + b1 + c1) − (a2 + b2 + c2). If the output of the optical system and the photodetector is adjusted so that TE = 0 when tracking is in focus, the focal position with respect to the groove can be determined by the sign of TE. Other configurations and detection principles are the same as those in the first embodiment.
The openings of the pinhole filters 19A, 19B, and 19C are preferably arranged so as to be parallel to the light beams in order to transmit the light beams from the condenser lenses 8A, 8B, and 8C.
For the reflection surface of each pinhole filter 19A, 19B, 19C, a metal surface, a dielectric reflection film or the like can be applied. In addition to the method of forming the opening in the metal, a method of metal plating, vapor deposition, dielectric vapor deposition, sputtering, or the like is also conceivable. In these openings, it is necessary to set the size of the openings so that most of the total light amount of the light beam condensed there is transmitted and a part of the light is reflected around the openings.
In this embodiment, since the pinhole filter has a projecting reflecting surface around the opening, the pinhole filter having the reflecting surface can be arranged substantially perpendicular to the optical axis of the return light. In addition, a plurality of photodetectors on the front surface of the pinhole filter can be arranged at optimum positions apart from the optical axis of the return light. Therefore, the arrangement of the pinhole filter and the zero point adjustment of the tracking error signal are facilitated, and the degree of freedom of the entire arrangement of the optical system is increased, so that each element can be arranged spatially and efficiently.

Next, a third embodiment will be described.
FIG. 4 is a schematic diagram of a third embodiment relating to the main part of the optical information recording / reproducing apparatus according to the present invention.
The third embodiment in FIG. 4 has substantially the same configuration and operation as the second embodiment described in FIG. 3, and only the configuration and operation of each pinhole filter 29A, 29B, and 29C is different.
That is, instead of each pinhole filter 19A, 19B, 19C, each pinhole filter 29A, 29B, 29C having a projecting reflection mirror around the opening is used, and each two-split photodetector 11A, 12A, Instead of 11B, 12B, 11C, and 12C, the respective two-divided photodetectors 21A, 22A, 21B, 22B, 21C, and 22C having openings are used. Here, it is also possible to use the individual photodetectors 11A, 12A, 11B, 12B, 11C, and 12C.
In the third embodiment, each pinhole filter 29A, 29B, 29C having a projecting type reflecting mirror around the opening is arranged substantially opposite to the optical axis of each condenser lens 8A, 8B, 8C. Has been. Of the light incident on the projection type pinhole filters 29A, 29B, and 29C from the condenser lenses 8A, 8B, and 8C, do not transmit the light to the rear of the projection type pinhole filters 29A, 29B, and 29C. There is light reflected by the surrounding protrusions, and these lights pass through the openings arranged in front of the pinhole filters 29A, 29B, and 29C while avoiding the light beams of the condenser lenses 8A, 8B, and 8C. Each of the two-divided photodetectors 21A, 22A, 21B, 22B, 21C, and 22C has detection. That is, an opening is provided at the center of the two-divided photodetector on the front surface of the pinhole filter so that the condensed light beam passes through the opening.
Therefore, since an opening is provided in the center of the two-divided photodetector on the front surface of the pinhole filter so that the condensed beam of the return light passes therethrough, the pinhole filter having a reflective surface is placed over the return light. Since it can be arranged substantially perpendicular to the optical axis, it is easy to arrange a pinhole filter and to adjust the zero point of the tracking error signal. Also, the overall arrangement of the optical system can be made compact.

Each detector needs to be arranged around the condensed beam of each condenser lens 8A, 8B, 8C as shown in FIG. Here, the outputs of the two-split photodetectors having the openings or the individual photodetectors 21A, 22A, 21B, 22B, 21C, and 22C are a1, a2, b1, b2, c1, and c2, respectively. When SA, SB, and SC are the differences between the two-divided photodetectors 21A and 22A, 21B and 22B, and 21C and 22C, respectively, SA = a1-a2, SB = b1-b2, SC = C1-c2.
At this time, the tracking error signal TE may be TE = SA + SB + SC = (a1 + b1 + c1) − (a2 + b2 + c2) as in the previous embodiment. If the output of the optical system and the photodetector is adjusted so that TE = 0 when tracking is in focus, the focal position with respect to the groove can be determined by the sign of TE. Other configurations and detection principles are the same as those in the first and second embodiments.
A metal surface, a dielectric reflection film, or the like can be applied to the reflection surface of each protruding pinhole filter 29A, 29B, 29C. In addition to the method of forming the opening in the metal, a method of metal plating, vapor deposition, dielectric vapor deposition, sputtering, or the like is also conceivable. As for the shape of the reflective surface around the opening of each of the projection type pinhole filters 29A, 29B, 29C, a convex shape centering on the opening is conceivable, but not limited to this, a polyhedron in combination with a plane is also applicable. Is possible. However, the size and the like of the opening need to be set so that most of the total amount of the light beam collected at the opening is transmitted and part of the light beam is reflected around the light.

Next, a fourth embodiment will be described.
FIG. 5 is a schematic diagram of a fourth embodiment relating to the main part of the optical information recording / reproducing apparatus according to the present invention.
The fourth embodiment in FIG. 5 has substantially the same configuration and operation as the first embodiment described in FIG. 1, and instead of the two beam splitters 7A and 7C in the first embodiment, FIG. As shown in FIG. 5, the grating beam splitter 17 is used.
The grating beam splitter 17 divides incident light into zero-order light and ± first-order light by diffraction. The three divided light beams are irradiated on the photodetectors 10A, 10B, and 10C through the condenser lenses 8A, 8B, and 8C and the pinhole filters 9A, 9B, and 9C. Other configurations and signal detection principles are the same as those in the first embodiment.
Further, the configuration of the grating beam splitter 17 of the fourth embodiment can be applied not only to the first embodiment but also to the configurations of the second and third embodiments shown in FIGS. is there. As for the grating beam splitter 17, a blazed or volume hologram can be applied in addition to the concavo-convex shape shown in FIG. 5.
By using the grating beam splitter 17, the division of the return light can be made compact, and the entire apparatus can be made compact.

Next, a fifth embodiment will be described.
FIG. 6 is a schematic view of a fifth embodiment relating to the main part of the optical information recording / reproducing apparatus according to the present invention.
The fifth embodiment of FIG. 6 has substantially the same configuration and operation as the fourth embodiment described with reference to FIG. 5, and is shown in FIG. 6 instead of the grating beam splitter 17 of the fourth embodiment. Thus, the difference is that a double grating of three combinations of the grating beam splitter 17B and the gratings 17A and 17C is used. Therefore, even when the light source has a wavelength variation, the focal position variation can be prevented, a decrease in the intensity of the photodetector can be avoided, and the stability of the optical system is improved.
As shown in FIG. 6, the grating beam splitter 17B diffracts the incident light into zero-order light and ± first-order light by diffraction, and further, the gratings 17A and 17C convert ± first-order light from the grating beam splitter 17B. Further, the respective diffracted configurations are different from those of the fourth embodiment. The operation is almost the same as that of the fourth embodiment shown in FIG. Further, each configuration other than this part and the signal detection principle are the same as those in the first embodiment.
Further, similarly to the fourth embodiment, the configuration of the grating beam splitter is not only applied to the first embodiment shown in FIG. 1 but also the configurations of the respective embodiments shown in FIGS. Is possible. For the grating beam splitter 7B and the gratings 7A and 7C, a blazed or volume hologram can be similarly applied in addition to the concave and convex type shown in FIG.
In the first to fifth embodiments thus far, a high-power pulse laser or the like is used as the light source 1 and the three-dimensional recording medium 6 is a two-layer structure composed of a two-photon recording material layer and a high reflection layer. A multilayer structure can be used. Therefore, since recording can be performed shallower in the depth direction during recording, the repeated layer spacing can be further reduced in a multilayer structure of a combination of a recording medium and a reflective layer.
In this case, the method of the configuration of the first to fifth embodiments can be applied to the focusing or tracking signal detection. It is necessary to change the light output of the light source 1 during recording and during reproduction and to decrease during reproduction. Further, as the two-photon recording material, a diarylethene photochromic material or the like can be applied.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic of 1st Embodiment regarding the principal part of the optical information recording / reproducing apparatus by this invention. The graph figure which shows the position regarding the optical axis direction of the condensing lens corresponding to it of each pinhole filter shown in FIG. 1, and the output of each photodetector. Schematic of 2nd Embodiment regarding the principal part of the optical information recording / reproducing apparatus by this invention. Schematic of 3rd Embodiment regarding the principal part of the optical information recording / reproducing apparatus by this invention. Schematic of 4th Embodiment regarding the principal part of the optical information recording / reproducing apparatus by this invention. Schematic of 5th Embodiment regarding the principal part of the optical information recording / reproducing apparatus by this invention. 1 is a schematic configuration diagram of an example of a conventional optical information recording / reproducing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source, 2 Condensing lens, 3 Polarization beam splitter, 4 Wave plate, 5 Objective lens, 6 Three-dimensional recording medium, 7 Grating, Beam splitter, 8 Condensing lens, 9 Pinhole filter, 10 Photo detector, 11 Division Light detector, 17 grating, beam splitter, 19 pinhole filter, 20 light spot position control device, 21 split light detector, 29 protruding pinhole filter

Claims (8)

An optical information recording / reproducing apparatus that records and reproduces information by irradiating a recording medium with a light spot,
Return light from the recording medium is divided into at least three parts, and at least three pinhole filters arranged near the focal point of the converged return light, and the pinhole filter for detecting light from the pinhole filter And a photodetector disposed behind
One of the positions of the openings of the at least three pinhole filters is the focal position of the return light, and the positions of the other openings of the pinhole filter are a predetermined distance before and after the focal position of the return light. The at least three pinhole filters are arranged so as to be separated from each other,
Detecting a focus error signal of the light spot from a differential output of the photodetector disposed behind the other pinhole filter disposed at a predetermined distance from the focal position of the return light. An optical information recording / reproducing apparatus. An optical information recording / reproducing apparatus that records and reproduces information by irradiating a recording medium with a light spot,
At least three pinhole filters configured to divide the return light from the recording medium into at least three parts and to be arranged in the vicinity of the focal points of the converged return lights and to have a reflecting surface around the opening. And two types of photodetectors arranged respectively in front and rear of the pinhole filter for detecting light from the pinhole filter,
One of the positions of the openings of the at least three pinhole filters is the focal position of the return light, and the positions of the other openings of the pinhole filter are a predetermined distance before and after the focal position of the return light. The at least three pinhole filters are arranged so as to be separated from each other,
While detecting the focus error signal of the light spot from the differential output of the photodetector arranged behind the other pinhole filter arranged away from the focal position of the return light by the predetermined distance, An optical information recording / reproducing apparatus, wherein the photodetector arranged in front is divided into two, and a tracking error signal is detected by taking a differential of each of the two-divided photodetectors.   3. The optical information recording / reproducing apparatus according to claim 1 or 2, wherein a photodetector disposed behind a pinhole filter at a focal position of the return light is separated from the focal position of the return light by a predetermined distance. Optical information recording / reproducing characterized in that the number of reflecting surfaces through which a light spot passes is calculated from a differential output with an average output of two detectors arranged behind two arranged pinhole filters apparatus.   4. The optical information recording / reproducing apparatus according to claim 1, wherein a grating is used as means for dividing the return light from the recording medium into three. .   5. The optical information recording / reproducing apparatus according to claim 4, wherein a double grating is used as means for dividing the return light from the recording medium into three.   6. The optical information recording / reproducing apparatus according to claim 1, wherein the pinhole filter has a projecting reflecting surface around an opening.   7. The optical information recording / reproducing apparatus according to claim 6, wherein an opening is provided in a central portion of the two-divided photodetector on the front surface of the pinhole filter so that a condensed light beam passes through the opening. An optical information recording / reproducing apparatus. 7. The optical information recording / reproducing apparatus according to claim 1, wherein a high-output light source is used as the recording light source, and recording with a multilayer structure is performed at an energy equivalent to a half wavelength of the recording wavelength. An optical information recording / reproducing apparatus for recording on a medium.

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