JP4386854B2 - Optical information recording / reproducing apparatus - Google Patents

Description

  The present invention relates to an optical information recording / reproducing apparatus, and more particularly to an optical information recording / reproducing apparatus suitable for recording / reproducing of a three-dimensional multilayer optical disc and capable of increasing focus detection sensitivity and resolution as compared with a conventional optical information recording / reproducing apparatus.

  In a conventional device of this type, light from a light source is irradiated onto an optical disk through an objective lens, the reflected light is received by a focusing lens, and signal detection is performed by a light beam transmitted through a pinhole installed at the focal position. ing. As for the focal position error signal, astigmatism is generated in the convergent light by the astigmatism optical system and is detected by the photodetector (for example, see Patent Document 1).

  In the prior art, as shown in FIG. 1, only a high-resolution light beam that has passed through a pinhole is used as a detection signal. However, in this technique, since the normal astigmatism method is used for the focus servo method, there is a problem that it is necessary to provide a separate detection optical path for the focus servo.

  Further, in the above-mentioned prior art, when the layer interval of the reflective layer is reduced in the multilayer disc, the range of the S-curve for focus detection must be made less than the layer interval, and the sensitivity is relatively deteriorated. There was also a problem.

Japanese Patent Laid-Open No. 10-340468

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide optical information suitable for recording and reproduction of a three-dimensional multilayer optical disc and capable of increasing focus detection sensitivity and resolution as compared with the prior art. It is to provide a recording / reproducing apparatus.

In order to achieve the above object, an optical information recording / reproducing apparatus according to claim 1 of the present invention includes a light source, an optical system that irradiates a light spot, and a light spot position control device, and light that irradiates a recording medium. In the optical information recording / reproducing apparatus for controlling the position of the spot, the return light from the recording medium is divided into at least three parts and converged , respectively, and the pinholes arranged near the focal points of the respective divided return lights , and these and a pinhole of rearwardly disposed photodetector, wherein one of the pin holes in the return light focal position of slightly each before and after the focal position of at least two other pinholes return light They are spaced apart, from the differential outputs of the two pin holes behind which are positioned upstream and downstream of the focal position of the return beam two detectors, have lines control the position of the light spot, each pinhole Each of the photodetectors arranged at the rear of the signal is divided into two parts, and a tracking error signal is detected by taking a differential of outputs of these two divided photodetectors .

In the optical information recording / reproducing apparatus according to claim 1, only a light beam having a high resolution in the depth direction that has passed through the pinhole can be used as a detection signal, and before and after the focal position of the return light. A focus differential signal in the range of the light spot corresponding to the interval between two pinholes arranged slightly apart can be obtained.
For this reason, it is possible to apply the focus servo to each of a plurality of reflective layers with a narrow interval, which is suitable for three-dimensional optical recording / reproduction. In addition, the signal through the pinhole at the focal point of the return light is more reflected from the surrounding layers than the signal through the two pinholes arranged slightly apart before and after the focal point of the return light. There is little light and stray light, and the quality of the signal can be improved by using only this signal.

In addition to the above , a tracking error signal can be detected. Further, since the tracking signal is detected from the light passing through the pinhole, stray light from other layers can be minimized. Here, the focus error signal is obtained by taking the sum of the outputs of the two-divided photodetectors and taking the differential of each sum signal.

An optical information recording / reproducing apparatus according to claim 2 of the present invention, in addition to the configuration of the optical information recording / reproducing apparatus according to claim 1, further includes at least a periphery of an opening on the light incident side of each pinhole. A light reflecting surface is formed in part, and a light detector divided into two is arranged on the light incident side of each pinhole to control the position of the light spot, and A tracking error signal is detected by taking a differential between photodetectors arranged in front of each other.

According to the optical information recording and reproducing apparatus according to claim 2, in addition to the effects of the optical information recording and reproducing apparatus according to claim 1, for detecting a tracking error signal efficiently.

An optical information recording / reproducing apparatus according to a third aspect of the present invention is the optical information recording / reproducing apparatus according to the second aspect, wherein the light reflecting surface is a surface orthogonal to the optical axis of the return light from the recording medium. It is characterized in that it is disposed at an angle with respect to.

According to the optical information recording / reproducing apparatus of the third aspect , in addition to the function and effect of the optical information recording / reproducing apparatus of the second aspect , the tracking error signal can be detected more efficiently, and the optical system can be used. The degree of freedom of overall arrangement increases, and each element can be arranged spatially and efficiently.

An optical information recording / reproducing apparatus according to a fourth aspect of the present invention is the optical information recording / reproducing apparatus according to the second aspect , wherein the optical information recording / reproducing apparatus is formed on at least a part of the periphery of the light incident side opening of the pinhole. The light reflecting surface has a protruding shape.

According to the optical information recording / reproducing apparatus of the fourth aspect, in addition to the function and effect of the optical information recording / reproducing apparatus of the second aspect, the pinhole having the reflecting surface is made substantially perpendicular to the optical axis of the return light. And a plurality of photodetectors on the front surface of the pinhole can be arranged at optimum positions apart from the optical axis of the return light. For this reason, the pinhole arrangement 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.

An optical information recording / reproducing apparatus according to claim 5 of the present invention is the optical information recording / reproducing apparatus according to any one of claims 2 to 4 , wherein the photodetector is divided into two on the light incident side of the pinhole. Is arranged outside the optical path of the return light.

According to the optical information recording / reproducing apparatus of the fifth aspect, in addition to the function and effect of the optical information recording / reproducing apparatus according to any one of the second to fourth aspects, a pinhole having a reflecting surface is passed through the optical axis of the return light. Therefore, it is easy to arrange the pinhole and adjust the zero point of the tracking error signal. Also, the overall arrangement of the optical system can be made compact.

  According to the present invention, a number of effects as described above can be obtained. In short, it is possible to provide an optical information recording / reproducing apparatus suitable for recording / reproducing of a three-dimensional multilayer optical disc and capable of increasing the focus detection sensitivity and resolution as compared with the prior art.

  Hereinafter, the present invention will be described in more detail on the basis of preferred embodiments shown in the accompanying drawings.

[Example 1]
The first embodiment will be described with reference to FIGS. In FIG. 3, the light emitted from the light source 1 passes through the condenser lens 2, the polarization beam splitter 3, the quarter wavelength plate 4, and is condensed into the three-dimensional recording medium 6 by the objective lens 5. The reflected light from this is reflected by the polarizing beam splitter 3 through the objective lens 5 and the quarter wavelength plate 4, divided into two by the beam splitter 7, and the divided light beam is divided into the condenser lenses 8A, 8B and The light is irradiated on each of the two-split photodetectors 10A, 10A ′ and 10B, 10B ′ through the pinholes 9A, 9B.

  Here, the opening of each pinhole 9A, 9B needs to be as small as about the diameter of the condensed beam of the condenser lens. The positions of the pinholes 9A and 9B are different from the focal positions of the condensing lenses 8A and 8b, respectively. In the example of FIG. 3, the pinhole 9A corresponds to the condensing position of the condensing lens 8A. On the contrary, the pinhole 9B is disposed slightly forward with respect to the condensing position of the condensing lens 8B.

  In such an arrangement of the pinholes 9A and 9B, the light passing through the pinholes 9A and 9B is shifted slightly from the condensing position of the condenser lens. The portion is cut by each pinhole, and the amount of transmitted light decreases. Here, the sum of the outputs of the photodetectors 10A and 10A 'and the sum of the outputs of 10B and 10B' are A and B, respectively. When the condensing spot positions of the condensing lenses 8A and 8B are C on the horizontal axis of FIG. 2A, the horizontal positions A and B indicate the relative positions of the pinholes 9A and 9B. .

  2A shows a state in which the position of the focused spot corresponding to the reflection surface of the three-dimensional recording medium 6 is in front (position B) with respect to the reference position C of the light detection device. It shows the relationship between the position of the pinhole at and the light output transmitted through it. Furthermore, the intersection of the broken line and the solid line graph represents a set output of one set of each two-divided photodetector that has passed through each pinhole in that state. The sum outputs A and B of the photodetectors 10A + 10A ′ and 10B + 10B ′ corresponding to the positions A and B of the pinholes 9A and 9B are represented by □.

  Graph 2 in FIG. 2A shows a pin in a state in which the position of the condensing spot corresponding to the reflecting surface of the three-dimensional recording medium 6 is rearward (position A) with respect to the reference position C of the light detection device. The relationship between the position of the hole and the light output transmitted through it is shown. In this state, the sum outputs A and B of the photodetectors 10A + 10A ′ and 10B + 10B ′ corresponding to the positions A and B of the pinholes 9A and 9B are represented by Δ. Further, the intersection of the broken line and the solid line graph at this position represents a set of sum outputs of each of the two-divided photodetectors that have passed through each pinhole in that state.

  At this time, the focus error signal FE is given by FE = A−B in the optical system of FIG. If the outputs of the optical system and the photodetector are adjusted so that FE = 0 at the time of focusing, the focal position can be determined by the sign of FE.

  That is, in FIG. 2A, adjustment is made so that FE = 0 in the middle of the state 1 (state shown in the graph 1) and the state 2 (state shown in the graph 2) 2 (at the time of focusing). For example, the reflection surface of the three-dimensional recording medium 6 is located above the medium 6 in FIG. 3 with respect to the reference position of the light detection device, and the position of the corresponding focused spot is the reference position C of the light detection device. 3 (close to the state shown in graph 2), FE <0, and the reflection surface of the three-dimensional recording medium 6 is below the medium 6 in FIG. When the position of the corresponding condensing spot is in front of the reference position C of this photodetection device (close to the state shown in the graph 1), FE> 0.

Regarding the tracking error signal (TE), when the outputs of the photodetectors 10A, 10A ′, 10B, and 10B ′ are A, A ′, B, and B ′,
TE = (A−B) + (A′−B ′).
Here, if the optical system and the photodetector are adjusted so that TE = 0 when the position of the focused spot is at the center of the groove of the track, the tracking error signal TE can be obtained by the push-pull method. The position of the focused spot can be determined by the sign of, and tracking becomes possible.

  Further, when the reflectance changes on the reflecting surface of the three-dimensional recording medium 6, the value of S varies, and the signal can be detected. As for the positions of the pinholes 9A and 9B, the positions of the pinholes 9A and 9B can be exchanged with each other if the relative positional relationship is maintained with respect to the condensing position C of the condenser lenses 8A and 8B. is there. As a material for the photodetector 10, a semiconductor detector such as Si or Ge can be used, but other materials may be used. The pinhole 9 is 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.

The recording signal S is detected as S = A + B.
Furthermore, if S is monitored as an inter-layer count signal and the variation in the value is counted, the number of layers through which the condensed spot has passed through the reflective layer of the three-dimensional recording medium 6 can be counted.

  According to the present embodiment, it is possible to easily control the position of the light spot and to easily obtain a tracking error signal.

[Example 2]
The following embodiment will be described with reference to FIG. In this embodiment, condensing lenses 13A and 13B are respectively provided between the pinholes 9A and 9B and the photodetectors 10A and 10A ′ and 10B and 10B ′ in the configuration of FIG. 3 of the first embodiment. It is. Regarding other configurations, there is no difference from the first embodiment.

  According to the present embodiment, the distance between the pinholes 9A, 9B and the photodetectors 10A, 10A ′ and 10B, 10B ′ can be made smaller than in the case of the first embodiment, so that the apparatus configuration can be made compact. The effect that it can be obtained.

Example 3
A third embodiment will be described with reference to FIGS. In FIG. 5, the emitted light from the light source 1 passes through the condenser lens 2, the polarization beam splitter 3, the quarter wavelength plate 4, and is condensed by the objective lens 5 into the three-dimensional recording medium 6. The reflected light from here is reflected by the polarizing beam splitter 3 through the objective lens 5 and the quarter wavelength plate 4, and is divided into three by the beam splitters 7A, 7B, and 7C. The light is irradiated onto the photodetectors 10A, 10B, and 10C through the lenses 8A, 8B, and 8C and the pinholes 9A, 9B, and 9C. Here, the pinholes 9A, 9B, and 9C are arranged so as to come to the approximate focal positions of the condenser lenses 8A, 8B, and 8C, respectively. The opening of each pinhole needs to be as small as the diameter of the focused beam of the focusing lens.

  The pinholes 9A, 9B, and 9C are different from the focal positions of the condenser lenses 8A, 8B, and 8C, respectively. In the example of FIG. 5, the pinhole 9B is located at the condenser position of the condenser lens 8b. In contrast to this, the pinhole 9A is disposed slightly behind the condensing position of the condensing lens 8A, and on the contrary, the pinhole 9C is condensing position of the condensing lens 8C. Is arranged slightly forward. In such an arrangement of the pinholes 9A, 9B, 9C, the amount of light transmitted through the pinhole 9B is maximized as compared to other cases.

That is, assuming that the output of the photodetector 10B is B, B is maximized at the position of the pinhole 9B. Compared to this, the light that has passed through the pinholes 9A and 9C is slightly shifted from the condensing position of the condensing lens, respectively. To do.
That is, the outputs of the photodetectors 10A and 10C (which are referred to as A and C, respectively) are smaller than the output B of the photodetector 10B. FIG. 2B shows the relationship between the position of each pinhole corresponding to that of the condensing lens in the optical axis direction and the output of each photodetector.

  A, B, and C on the horizontal axis indicate the positions of the pinholes 9A, 9B, and 9C. The intersection of the broken line and the solid line graph at this position represents the output of the photodetector. FIG. 2 shows three states 1, 2, and 3 based on the relationship between the beam position of the condenser lens and the pinhole position.

  Here, the state 1 (state shown in the graph 1) is a state where the reflecting surface of the three-dimensional recording medium 6 is in front of the reference position of the light detection device (upper side in FIG. 3), and the photodetectors 10A, 10A, Each output A, B, C of 10B, 10C is represented by □. State 2 (state shown by graph 2) is a case where the reflection surface of the three-dimensional recording medium 6 is at the reference position of the light detection device, and the outputs A, B, and C of the light detectors 10A, 10B, and 10C are It is represented by a circle.

  In the state 3 (state shown in the graph 3), the photodetectors 10A and 10B are in a state where the reflection surface of the three-dimensional recording medium 6 is behind (lower side in FIG. 5) with respect to the reference position of the photodetector. , 10C, outputs A, B, C are represented by Δ marks. Here, when the output of each photodetector is A, B, and C in FIG. 5, the focus error signal FE is given by FE = A−C. If the outputs of the optical system and the photodetector are adjusted so that FE = 0 at the time of focusing, the focal position can be determined by the sign of FE.

  That is, as shown in FIG. 2, in the state 2 (at the time of focusing), if the adjustment is made so that FE = 0, for example, the reflection surface of the three-dimensional recording medium 6 is at the reference position of the light detection device. On the other hand, in the case of the state 1 that is in front (upper side in FIG. 5), FE> 0, and the reflection surface of the three-dimensional recording medium 6 is rearward (lower side in FIG. 5) with respect to the reference position of the light detection device. In state 3 in which FE <0, FE <0.

  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, and a signal can be detected. With respect to the positions of the pinholes 9A, 9B, and 9C, the positions of the pinholes 9A, 9B, and 9C are as long as the relative positional relationship is maintained with respect to the condensing positions of the condenser lenses 8A, 8B, and 8C. They are interchangeable. As a material for the photodetector 10, a semiconductor detector such as Si or Ge can be used, but other materials may be used.

  The pinhole 9 is 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. 2B, the relative positions of the pinholes 9A, 9B, 9C with respect to the reference position of the photodetector. Changes, the value of SC changes to ± every time the reference position of the light detection device passes vertically through the reflective layer of the three-dimensional recording medium 6.

  By counting the number of ± changes in this value, the number of layers through which the condensed spot has passed through the reflective layer of the three-dimensional recording medium 6 can be counted. In this embodiment, each of the photodetectors 10A, 10B, and 10C is a single photodetector, but a two-divided photodetector can be applied as in the first and second embodiments. Tracking is possible as in Examples 1 and 2.

  In this embodiment, the signal passing through the pinhole at the focal position of the return light is more peripheral than the signal passing through two pinholes arranged slightly apart before and after the focal position of the return light. Since the reflected light and stray light from the layer are reduced, the quality of the signal can be improved by using only this signal.

Example 4
A fourth embodiment will be described. FIG. 6 shows a configuration that operates substantially the same as the embodiment described in FIG. However, unlike the above-described embodiment, each of the pinholes 9A, 9B, 9C is not a light-shielding surface but a reflecting surface around the front-side pinhole opening. Further, in this embodiment, each pinhole 9A, 9B, 9C The condenser lenses 8A, 8B, and 8C are arranged slightly inclined with respect to the optical axis.

  For this reason, out of the light incident on the pinholes 9A, 9B, and 9C from the condenser lenses 8A, 8B, and 8C, the light reflected around the pinholes 9A, 9B, and 9C is not transmitted behind the pinholes 9A, 9B, 9C. These light beams are disposed in front of the pinholes 9A, 9B, and 9C while avoiding the light fluxes of the condenser lenses 8A, 8B, and 8C. Detected by 12B, 11C, and 12C, respectively.

  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, Sa = A1-A2, Sb = B1-B2, and Sc = C1-C2 when the difference between 11B and 12B and the difference between 11C and 12C are Sa, Sb, and Sc, respectively.

  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, TE = Sa + Sb + Sc = (A1 + B1 + C1) − (A2 + B2 + C2).

  Further, 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 above-described embodiment. The openings of the pinholes 9A, 9B, and 9C are preferably arranged in parallel to the light beams so as to transmit the light beams from the condenser lenses 8A, 9B, and 9C.

  For the reflection surface of each pinhole 9A, 9B, 9C, a metal surface, a dielectric reflection film or the like can be applied. As a manufacturing method, in addition to a method of manufacturing an opening in a metal, methods such as metal plating, vapor deposition, dielectric vapor deposition, and sputtering are also conceivable. In these openings, it is necessary to set the size of the openings so that most of the total amount of the light beam condensed there is transmitted and a part of the light is reflected around the openings.

According to this embodiment, the tracking error signal can be detected efficiently.
In the present embodiment, the reflecting surface is arranged slightly inclined with respect to the optical axis of each of the condenser lenses 8A, 8B, 8C, but is not limited to this.

Example 5
Another embodiment will be described with reference to FIG. FIG. 7 shows, in place of the pinholes 9A, 9B, and 9C in FIG. 6 of the fourth embodiment, the pinholes 9A, 9B, and 9C having protrusion-type reflecting mirrors around the openings. Instead of the two-divided photodetectors 11A, 12A, 11B, 12B, 11C, and 12C, the two-divided photodetectors 11A, 12A, 11B, 12B, 11C, and 12C having openings or the individual photodetectors 11A are used. , 12A, 11B, 12B, 11C, 12C are used.

  In this embodiment, the pinholes 9A, 9B, 9C each having a projection-type reflecting mirror around the opening are arranged substantially facing each other with respect to the optical axes of the condenser lenses 8A, 8B, 8C. . Of the light incident on the protruding pinholes 9A, 9B, and 9C from the condenser lenses 8A, 8B, and 8C, do not transmit the light to the rear of the protruding pinholes 9A, 9B, and 9C. There is light reflected by the protrusions, and these lights are arranged in front of the pinholes 9A, 9B, 9C while avoiding the light beams of the condenser lenses 8A, 8B, 8C. Detection is performed by the two-divided photodetectors 11A, 12A, 11B, 12B, 11C, and 12C or the individual photodetectors 11A, 12A, 11B, 12B, 11C, and 12C, respectively.

  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 respective two-divided photodetectors having openings or the individual photodetectors 11A, 12A, 11B, 12B, 11C, and 12C are A1, A2, B1, B2, C1, and C2, respectively. Sa = A1-A2, Sb, where Sa, Sb, and Sc are the differences between the two-split photodetectors or the single photodetectors 11A and 12A, the differences between 11B and 12B, and the differences between 11C and 12C, respectively. = B1-B2, Sc = C1-C2.

At this time, if the tracking error signal is set to TE = Sa + Sb + Sc = (A1 + B1 + C1) − (A2 + B2 + C2) as in the previous embodiment, the optical system and the photodetector are set so that TE = 0 when tracking is in focus. If the output is adjusted, 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 9A, 9B, 9C. 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. Concerning the shape of the reflection surface around these openings, a convex shape centering on the openings is conceivable, but the present invention is not limited to this, and a polyhedron or the like in combination with a flat surface is also applicable. However, it is necessary that the size of the opening is set so that most of the total amount of the light beam condensed at the opening is transmitted and a part of the light beam is reflected around the light.

  According to the present embodiment, the pinhole with the reflecting surface can be arranged substantially perpendicular to the optical axis of the return light, and the plurality of photodetectors in front of the pinhole are arranged with respect to the optical axis of the return light. Since it can be placed at an optimum position apart from each other, pinhole placement and tracking error signal zero point adjustment become easy, and the optical system also has a higher degree of freedom in overall placement, making each element spatial Can be arranged efficiently.

Example 6
Another embodiment will be described with reference to FIG. 8 has substantially the same configuration as that of the third embodiment of FIG. 5, but uses the grating beam splitter 7 in FIG. 8 instead of the two beam splitters 7A and 7C in FIG. The grating beam splitter 7 can divide incident light into zero-order light and ± first-order light by diffraction. The three divided light beams are irradiated onto the photodetectors 10A, 10B, and 10C through the condenser lenses 8A, 8B, and 8C and the pinholes 9A, 9B, and 9C.

  The other components, spot positions, and tracking error signal detection principles are the same as in the first embodiment. This configuration is applicable not only to the first embodiment but also to the configurations of the fourth and fifth embodiments shown in FIGS. As for the grating beam splitter 7, in addition to the concavo-convex type shown in the drawing, a blazed or volume hologram can be applied.

  According to the present embodiment, the tracking error signal can be detected more efficiently, the optical system can be made compact as a whole, the degree of freedom of arrangement is increased, and each element is spatially arranged efficiently. Can do.

Example 7
Still another embodiment will be described with reference to FIG. This embodiment is substantially the same as the sixth embodiment, but using a combination of a grating beam splitter 7B and gratings 7A and 7C as shown in FIG. 9 instead of the grating beam splitter 7 in FIG. Yes. The grating beam splitter 7B divides incident light into zero-order light and ± first-order light by diffraction.

  That is, this embodiment is different from the sixth embodiment in that the ± first-order light from the grating beam splitter 7B is further diffracted by the gratings 7A and 7C. The operation based on this configuration is substantially the same as that of the sixth embodiment shown in FIG. 8, but has an advantage that it is less affected by wavelength fluctuations due to temperature fluctuations of the light source.

  The other components and the signal detection principle are the same as in the third embodiment. Similar to the sixth embodiment, this configuration is applicable not only to the third embodiment shown in FIG. 5 but also to the configurations of the fourth and fifth embodiments shown in FIGS. . As for the grating beam splitter 7B and the gratings 7A and 7C, in addition to the concavo-convex type shown in FIG. 9, a blazed or volume hologram can be similarly applied.

    According to the present embodiment, the same effect as that of the sixth embodiment can be obtained, and in addition to this, there is an advantage that it is not easily affected by the wavelength variation caused by the temperature variation of the light source.

[Examples 8 and 9]
Further examples 8 and 9 will be described with reference to FIGS. These embodiments have substantially the same configuration as the first and sixth embodiments. In the first embodiment shown in FIG. 3, two condenser lenses 8A and 8B are used. However, in the eighth and ninth embodiments shown in FIGS. 10 and 11, the condenser lens 8 is arranged in front of the grating beam splitter 7. 1 is different.

  Further, in the case of the embodiment 8 shown in FIG. 10, one opening and a transparent portion or another portion are respectively provided on the upper portions of the two sets of photodetectors 10A, 10A ′, 10B, and 10B ′ formed in the substrate 15. Two pinhole layers 9A and 9B having large openings are sequentially stacked, and a grating beam splitter 7 is further stacked thereon with a spacer 14 interposed therebetween.

  Here, the openings of the two pinhole layers 9A and 9B are adjusted and arranged so as to be directly above the two sets of photodetectors 10A and 10A 'and 10B and 10B', respectively. Further, the pinhole layer 9B below the opening of the pinhole layer 9A is a transparent portion or another larger opening so as not to block light that has passed through the pinhole layer 9A.

  Similarly, the pinhole layer 9A immediately above the opening of the pinhole layer 9B is a transparent portion or another larger opening so as not to block light passing through the opening of the pinhole layer 9B. It has become. Further, the light beam is divided into two by the grating beam splitter 7 so as to be condensed at the position of the opening of each pinhole layer.

  The present embodiment is characterized in that each element from the grating beam splitter 7 to the substrate 15 is integrated as described above. In the case of the ninth embodiment shown in FIG. 11, a pinhole layer 9 having two openings is stacked on top of two sets of photodetectors 10A, 10A ′, 10B, and 10B ′ formed in the substrate 15. The grating beam splitter 7 is laminated on the spacer 14 via the spacer 14.

  Here, the two openings of the pinhole layer 9 are adjusted and arranged so as to be directly above the two sets of photodetectors 10A, 10A 'and 10B, 10B', respectively. The rest is the same as in the case of Example 8 in FIG. In the case of FIG. 10, the difference between the eighth and ninth embodiments can be dealt with when the pinhole layer 9 is composed of two layers and the condensing positions of the two light beams are different in the direction perpendicular to the substrate 15. It is in the point which can expand the range of design more.

  The operation of the eighth and ninth embodiments is almost the same as that of the first embodiment of FIG. Here, since one condenser lens 8 is disposed in front of the grating beam splitter 7, the light beam from the beam splitter 3 is focused by the condenser lens 8 and then divided into two by the grating beam splitter 7. Is different.

  In FIG. 10, the zero-order light is arranged on the photodetectors 10A and 10A ', and the first-order diffracted light is collected on the photodetectors 10B and 10B'. Each component other than this part and the signal detection principle are the same as those in the first embodiment. As for the grating beam splitter 7, in addition to the volume hologram shown in FIG. 9, a concavo-convex type and a blaze type can be similarly applied.

  If the condensing type grating beam splitter 7 is used, the functions of the condensing lens 8 and the grating beam splitter 7 can be combined. As in the previous embodiments, this configuration can be applied not only to the first embodiment shown in FIG. 3 but also to the configuration of the third embodiment.

  According to the above-described embodiment, pinholes can be easily produced and arranged, and the cost can be reduced. In addition, the divided optical path length in the optical system can be greatly reduced, and the entire apparatus can be configured compactly. The effect is obtained.

Example 10
Still another embodiment 10 will be described with reference to FIG.
This embodiment has almost the same configuration as the eighth and ninth embodiments. In the eighth and ninth embodiments of FIGS. 10 and 11, the grating beam splitter 7 and the spacer 14 are used, but in the embodiment 10 shown in FIG. 12, a birefringent crystal 14A is used instead. It is different.

  The light beam from the beam splitter 3 is focused by the condensing lens 8 and then divided into two by the birefringent crystal 14, passing through the opening of the pinhole layer 9, and two sets of photodetectors 10A, 10A ′, Condensed to 10B and 10B ′. Here, it is necessary to align the incident light polarization plane with a crystal orientation that can be divided into two by the birefringent crystal 14A. Each configuration other than this part and the signal detection principle are the same as in the eighth and ninth embodiments.

  According to the present embodiment, the configuration of the optical system is further simplified by disposing the birefringent crystal 14A in the space where the spacer 14 was used in the above-described embodiment. It is possible to reduce the number of components.

[Reference example]
In Examples 1 to 10 so far, a high-power pulse laser or the like is used as the light source 1, and a three-dimensional recording medium 6 has a multilayer structure composed of a two-layer structure consisting of a two-photon recording material layer and a partial reflection layer. Can be used. In this case, the methods having the configurations of the first to tenth embodiments can be applied to the focusing or tracking signal detection.

  In this reference example, the light output of the light source 1 is changed during recording and during reproduction. It is necessary to lower the light output of the light source 1 during reproduction as compared with recording. In this reference example, other configurations and detection principles of various signals are the same as those in the first to tenth embodiments. As the two-photon recording material, a diarylethene-based photochromic material or the like is applicable.

  Each of the above-described embodiments is merely an example of the present invention, and the present invention is not limited to these examples, and appropriate modifications and improvements may be made without departing from the scope of the present invention. Needless to say, it is good.

It is a figure explaining the principal part structure of the optical head which concerns on a prior art. (A), (B) is a figure explaining the effect | action of the optical head based on one Example of this invention. It is a figure explaining the principal part structure of the optical head which concerns on one Example of this invention. It is a figure explaining the principal part structure of the optical head which concerns on another Example. It is a figure explaining the principal part structure of the optical head which concerns on another Example. It is a figure explaining the principal part structure of the optical head which concerns on another Example. It is a figure explaining the principal part structure of the optical head which concerns on another Example. It is a figure explaining the principal part structure of the optical head which concerns on another Example. It is a figure explaining the principal part structure of the optical head which concerns on another Example. It is a figure explaining the principal part structure of the optical head which concerns on another Example. It is a figure explaining the principal part structure of the optical head which concerns on another Example. It is a figure explaining the principal part structure of the optical head which concerns on another Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 2 Condensing lens 3 Polarizing beam splitter 4 1/4 wavelength plate 5 Objective lens 6 Three-dimensional recording medium 7, 7A, 7B, 7C Beam splitter (grating beam splitter)
8A, 8B, 8C Condensing lens 9A, 9B, 9C Pinhole 10A, 10A ', 10B, 10B', 10C Photodetector 11A, 11B, 11C Photodetector 12A, 12B, 12C Photodetector 13A, 13B Lens 14 Spacer 14A Birefringent crystal (beam splitter)
15 Substrate

Claims (5)

In an optical information recording / reproducing apparatus having a light source and an optical system for irradiating a light spot, and a position control device for the light spot, and performing position control of the light spot irradiating the recording medium
Pinholes arranged in the vicinity of the focal points of the divided return lights, each of which converges the return light from the recording medium by dividing into at least three parts, and a photodetector arranged behind these pinholes. Have
One of the pinholes is arranged at the focal position of the return light, and at least the other two pinholes are arranged slightly apart before and after the focal position of the return light, and are arranged before and after the focal position of the return light. was from the differential output of the two detectors of the two pinholes rear, have lines control the position of the light spot,
The photodetectors arranged behind the pinholes are each divided into two parts, and the tracking error signal is detected by taking the differential of the outputs of the two divided photodetectors. An optical information recording / reproducing apparatus. A light reflecting surface is formed on at least part of the periphery of the light incident side opening of each pinhole,
Further, a photodetector divided into two is also arranged on the light incident side of each pinhole,
Performs position control of the light spot, by taking the differential optical detectors disposed respectively in front of each pin hole, the light according to claim 1, characterized in that to detect the tracking error signal Information recording / reproducing apparatus. 3. The optical information recording / reproducing apparatus according to claim 2 , wherein the light reflecting surface is disposed at an angle with respect to a surface orthogonal to the optical axis of the return light from the recording medium. The optical information recording / reproducing apparatus according to claim 2 , wherein a light reflecting surface formed at least part of the periphery of the light incident side opening of the pinhole has a protruding shape. 5. The optical information recording / reproducing apparatus according to claim 2 , wherein the two-divided photodetectors on the light incident side of the pinhole are arranged outside the optical path of the return light.

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