JP4585899B2 - Multi-layer disc carrier information recording / reproducing apparatus - Google Patents

Description

  The present invention relates to the field of apparatus for recording and reading signals on a multilayer disc information record carrier.

  In recent years, there has been a strong demand for an increase in capacity of an optical information record carrier (disc carrier) as the amount of information increases.

The recording density on the optical disc is
(NA / λ) ²
λ: Recording / reproducing light source wavelength
NA: Since it is proportional to the numerical aperture of the objective lens, in recent years, a 405 nm GaN laser is used as λ, and the objective lens NA is 0.85. Yes.

  However, the method of increasing the recording capacity by increasing the objective lens NA as much as possible and shortening the recording / reproducing light source wavelength as much as possible has almost reached the limit.

  If the light source wavelength is shorter than 405 nm, the light transmittance of a polycarbonate substrate conventionally used as a disk carrier resin substrate is rapidly reduced.

  Further, when the wavelength of the light source is shorter than 400 nm, the transmittance of the resin substrate is reduced, and compositional decomposition occurs when the light source is irradiated for a long time, and the light transmittance is further lowered.

  On the other hand, when the NA of the objective lens is further increased, the distance (WD) between the objective lens and the disk carrier is further reduced, so that the protective layer film produced on the recording film also has a WD limitation and a tilt margin of the disk carrier. From the viewpoint, it becomes 100 μm or less. Therefore, since the WD becomes smaller, the objective lens is more likely to collide with the disk carrier, and the protective layer is also less than 100 μm, so that the dirt on the disk protective layer is very close to the signal surface, and a little dirt on the disk protective layer is found on the disk. The playback signal will deteriorate.

  As described above, shortening λ and further increasing the objective lens NA to achieve higher capacity will cause various problems, and considerable technological development will be performed to overcome this problem. There is a need.

  Therefore, the method of laminating a large number of recording layers has relatively few problems for further increasing the capacity of the optical disk, and this method is considered to become the mainstream in the future.

  For this reason, a multilayer disk carrier as shown in FIG. 12 has been announced. This multi-layer disc carrier has a carrier substrate 56 having a control groove 53 consisting of a groove surface and a non-groove surface on one side as the lowermost layer, and a multi-layer recording film formed by repeating a recording film 51 on the separation layer 52 thereon. Have. Further, when this separation layer is formed by transfer using a conventional optical disk carrier manufacturing technique, control grooves similar to those of the carrier substrate are formed on the separation layer 52. After that, since the recording film 51 is formed, a concave and convex control groove 53 is formed in the recording film 51 of each layer.

  With such a structure, the recording film is multilayered to improve the recording capacity.

  The recording film 51 is completely different in principle from the conventional translucent one-photon absorption recording film that records a signal by utilizing phase transition or deformation of the film due to heat generation by absorption of one-photon light, or the conventional one-photon light absorption recording. A completely transparent multiphoton recording film that records signals using multiphoton absorption is used. Since the former translucent recording film absorbs light, when the total number of recording films is 4-5 layers or more, the attenuation of light increases, and recording cannot be performed on a recording film deeper than this, and the recording capacity is limited.

  In order to overcome this problem, multiphoton absorption recording using a complete transparent film has recently attracted attention (see, for example, Patent Document 1). In the case of multiphoton absorption recording, electrons where the optical electric field in the vicinity of the light condensing point 3 is extremely strong are excited to cause a light absorption reaction. Therefore, since the multiphoton absorption recording material is a completely transparent material in which light does not attenuate just by passing through the recording film 51 like a conventional translucent recording film, a very large number of recording films can be stacked. This is much more advantageous for higher capacity.

  In this way, the technology required for multi-layering is one major advance.

  However, there is an even greater problem with multi-layer disk carriers. The problem is how accurately the light condensing point 3 can be swept on the recording film 51 on the control groove 53. In order to easily solve this problem on the multi-layer disc carrier recording / reproducing apparatus side, as shown in FIG. 12, a concave / convex control groove is provided in each recording film 51 as in the conventional optical disc record carrier, and recording / reproducing condensing is performed on this. A method of following the point 3b can be considered. Although this method is certainly a conventional stack, it seems to be able to solve the problem easily, but it becomes a big problem for multilayering.

  Because, as described above, in order to form the control groove 53 in each recording film 51, a stamper is pressed against the surface of the separation layer 52 when the separation layer 52 is applied and cured, and if the separation layer is formed of UV resin, the stamper It is necessary to cure by irradiating UV light from the opposite side (usually the carrier substrate 56 side), and then peeling off the stamper.

  Therefore, each time the recording layer is constructed, a pressing and peeling operation by a stamper occurs, so that a large strain force remains in each separation layer, and when this transfer operation is repeated 10-30 times, the residual stress generated in the disc is: Become very large.

  The surface runout of the multi-layer disc carrier made in this way, or the surface runout amount of the present disc carrier in a high temperature and high humidity state is added by the square average of the disc runout amount even if simply considered. In the case of a multi-layer disc carrier consisting of 30 layers, a surface runout of √30 = 5.5 times occurs compared to a disc carrier consisting of one layer, and a very poor quality disc is produced.

Further, if the control grooves 53 are provided in each recording layer in this manner, the transfer process is performed many times, so that the productivity is deteriorated and the cost of the multilayer disk carrier is increased.
Japanese Patent No. 2961126

  In order to solve this problem, as shown in FIG. 13, the control groove 53 is formed only on the surface of the carrier substrate 56 by using the conventional optical disk molding technique, and the control groove 53 is not attached to the other recording film 51. It is conceivable to simplify the manufacturing process of the multilayer disk carrier.

  FIG. 13 shows an optical system conventionally considered as a recording / reproducing apparatus for writing a signal on such a multilayer disk carrier.

  In the figure, the semiconductor laser 1a is an optical system constituting a control condensing point 3a for irradiating the control groove 53 on the carrier substrate. On the other hand, the recording / reproducing condensing point 3b is configured by condensing the light emitted from the semiconductor laser 1b having an oscillation wavelength of 650 nm by the objective lens 10.

  Although there are many recording films 51, the recording film 51 to be recorded is determined by moving the objective lens 10 in the 11 direction to move the position of the recording / reproducing condensing point 3b. When the objective lens 10 is moved in the 11 direction, the position of the control condensing point 3a to be accurately irradiated on the control groove 53 is also moved in the 11 direction. In order to correct this, the collimator lens 2a and the semiconductor laser 1a are moved in 12 directions, and control is performed so that the control light condensing point 3a is continuously focused on the control groove 53. However, it is very difficult to make the recording / reproducing light condensing point 3b and the control light condensing point 3a consistently stably on the optical axis 13 with such an optical configuration. For example, the central axis of the light beam of the semiconductor lasers 1a and 1b moves about 0.1 degrees with heat, and the objective lens 10 is moved in 11 directions to switch the recording film 51. The collimator lens 2a or the semiconductor laser 1a is moved in 12 directions. Therefore, it is difficult to always arrange the control condensing point 3a and the recording / reproducing condensing point 3b on the optical axis 13, since components in a direction perpendicular to these are inevitably mixed.

In order to solve the above problems, the first aspect of the present invention provides:
A carrier substrate having a control groove formed by a groove surface and a non-groove surface on one side, a separation layer formed on the control groove of the carrier substrate, and a multilayer having a repetition of a recording film formed on the separation layer With a recording film,
The recording film on which the signal is recorded has a signal groove formed from a recorded surface and an unrecorded surface,
The incident light that has passed through the multilayer recording film and has reached the carrier substrate, the reflected light from the groove surface is different in phase from the reflected light from the non-groove surface,
The reflected light from the recorded surface with respect to the incident light that has passed through a part of the multilayer recording film and reached the recording film has a phase different from that of the reflected light from the unrecorded surface. A multilayer disk carrier information recording / reproducing apparatus for reproducing,
One light source for irradiating the multilayer disc carrier with light for at least one of recording and reproduction;
An objective lens that is installed between the multilayer disc carrier and the light source and forms a recording / reproducing condensing point that is a condensing point for performing at least one of recording and reproduction of the signal;
Of the light that forms the recording / reproducing condensing point, the recording film transmitted light that has passed through the recording film on which the recording / reproducing condensing point is formed is applied to the recording film on which the recording / reproducing condensing point is formed. Multi-layer disc carrier information recording / reproduction comprising control means for controlling the position of the recording / reproducing condensing point in the left-right direction on the recording film using reflected light from the adjacent control groove or signal groove Device.

The second aspect of the present invention is
A two-part photodetector for receiving the reflected light;
A light transmission blocking grating composed of a plurality of linear portions disposed in front of the two-part photodetector for blocking light transmission;
It said control means moves said control signal obtained from the differential signal of each of the outputs of the two photodetectors of the two-divided photodetector, wherein the recording and reproducing condensing point is over the control groove or said signal groove The multilayer disc carrier information recording / reproducing apparatus according to the first aspect of the present invention performs control as described above.

The third aspect of the present invention
The light transmission blocking grating, said being created on one side of the plate is transparent to the reflected light, said one surface and said two-division photodetector surfaces are in close contact, multi-layer disk carrier of the second of the present invention An information recording / reproducing apparatus.

The fourth aspect of the present invention is
The control Mizowaka properly in position where the reflected light from the signal grooves are imaged after passing through the objective lens, the contact surface between the plate and the two-divided photodetector surfaces are arranged, the 3 is a multi-layer disc carrier information recording / reproducing apparatus according to the present invention.

The fifth aspect of the present invention is
The flat plate includes a liquid crystal provided as a central member, and two transparent electrodes provided so as to sandwich the liquid crystal,
The control means is the multilayer disc carrier information recording / reproducing apparatus according to the fourth aspect of the present invention, wherein an error is applied to the control signal by applying a potential between the transparent electrodes.

The sixth aspect of the present invention
A light detector having a lattice shape, installed at a position where the reflected light forms an image after passing through the objective lens;
The control means, a differential signal of the photodetector having the lattice shape, the recording reproducing condensing point is the control Mizowaka properly performs control to move the top of the signal grooves, first the It is the multilayer disk carrier information recording / reproducing apparatus of the invention.

The seventh aspect of the present invention
Photodetector having the lattice shape, the a photodetector of the plurality of rod-like longitudinal direction is arranged parallel to the parallel direction of the interference pattern is imaged, the sixth multi-layer disc of the present invention This is a carrier information recording / reproducing apparatus.

For example, the present invention relates to an apparatus for recording and reproducing information on a multilayer disc information record carrier, wherein the multilayer disc information record carrier comprises a carrier substrate 56, a recording film 5 1 , a separation layer 52 which are not on the same plane, and The plane of the carrier substrate has a groove (control groove 53) that gives weak reflected light to the incident light that has passed through the recording film and the separation layer and gives a phase difference to the reflected light, while the recording film also reflects the incident light. On the other hand, the recording portion is made of a composition that gives a weak reflection whose phase is different from that of the recording film reflection light from the recorded portion, while the emitted light from the objective lens 10 of the recording / reproducing apparatus is One or more condensing points are formed, and one of these condensing points (recording / reproducing condensing point 3b) is placed on the recording film to record or reproduce information, and from the recording film by the condensing point. of The recording / reproducing condensing point is controlled by using a signal recorded in the recording layer adjacent to the excessive light as a control groove or by detecting a reflection signal from a control groove on the adjacent carrier substrate plane. A recording / reproducing apparatus.

  By using the present invention, it is not necessary to create a control groove in each recording layer of the multilayer structure information record carrier, the production method of the multilayer information record carrier is simplified, and low cost and high accuracy of the multilayer information record carrier are achieved. Is done. On the other hand, even when such an information record carrier is used, the control groove signal can be detected stably without losing the amount of light output from the objective lens.

  The present invention does not create the recording / reproducing condensing point 3b and the control condensing point 3a by using two separate semiconductor lasers as in the prior art of FIG. The recording film 51 is formed to control the position of the recording / reproducing light converging point 3b from the control groove 53 or the recording groove of the recorded pit signal to stably record the signal on the multilayer disc information record carrier. .

  In the present invention, the control groove 53 for controlling the position of the recording / reproducing condensing point is not formed on each recording film which has been conventionally performed to control the recording / reproducing condensing point 3b. Create only on the upper carrier substrate or protective layer.

  Therefore, it is very easy to manufacture as a multi-layer disk carrier, and it is inexpensive and a disk carrier without distortion can be manufactured. The present invention has been made to record a signal at an accurate position on each recording film 51 of such a multilayer disk carrier.

Further, the present invention forms a only the reproducing converging point 3 b in the light flux emitted from the objective lens 10 without creating a control focal point by using the recording film 51a adjacent to the control grooved carrier substrate 56 when the entire surface of the information recording of the recording film 51a to the adjacent performs information recording is completed, by moving the reproducing focal point 3b to the next recording layer 51b by moving the objective lens 10 to the protective layer 50 direction , Yuku performed recorded on the recording film 51b. By repeating the same method, an inexpensive optical system for obtaining a groove control signal for controlling a recording / reproducing condensing point for recording one after another on the recording film on the multilayer disk carrier at the same position as the control groove. It was made to provide.

(Embodiment 1)
One embodiment of the present invention is shown in FIGS. 1 and 2 and will be described in detail.

  First, a description will be given of recording information on the recording film 51a adjacent to the carrier substrate 56 shown in FIG.

  At this time, a part of the light at the recording / reproducing condensing point 3 b formed on the recording film 51 a passes through the recording film 51 a and irradiates the control groove 53 on the surface portion on the carrier substrate 56. Since the transmitted light spreads, the diameter of the spread circle is referred to as an irradiation circle 4.

  Now, since there is a slight difference in refractive index between the material forming the recording film separation layer 52 and the carrier substrate 56, for example, the refractive index of the carrier substrate 56 is 1.5 and the refraction of the recording film separation layer 52 resin. If the rate is 1.47, about 1% reflection occurs at this interface. In this case, as can be seen from FIG. 1, since there is an uneven control groove 53 on the surface of the carrier substrate 56, the recording film separation layer 52 resin enters the uneven groove. Therefore, a reflectance of about 1% also exists from the control groove 53. In this description, the reflection is calculated from the difference in refractive index between the resins. However, an intermediate refractive index material may be attached to the surface of the carrier substrate by vapor deposition or the like so that a reflectance of about 1% is positively generated. In this case, the light passing through the recording film 51a spreads and irradiates the surface of the carrier substrate 56 to the control groove 53 in the irradiation circle 4. Now, the light irradiating this groove is reflected by the reflectance of about 1% and passes through the objective lens 10 again. The light that has passed through the objective lens 10 is collected by the detection lens 11.

  As an optical system of this configuration, the irradiation light wavelength λ 405 nm, the NA of the objective lens 10 is 0.85, the focal length f1 is 3 mm, the focal length f2 of the detection lens 11 is 60 mm, the thickness of the recording separation layer 52 is 2 μm, and the control groove Consider a condensing point in the detection system when the pitch P of 53 is 0.35 μm.

  When there is a gap between the objective lens 10 and the detection lens 11 as in this example, it is necessary to calculate with the two-time lens formula. Even if calculation is performed assuming that the focal point of f1 is f1 and the focal length on the detection side is f2, almost no error occurs.

  Now, the recording / reproducing condensing point 3b condensed by the objective lens 10 is condensed at a position of 3 mm from the objective lens. Therefore, the light reflected from the recording / reproducing condensing point 3b by the recording film 51a forms the detection-side condensing point 9 at a position 60 mm behind the detection lens 11.

On the other hand, a part of the light that has passed through the recording film 51 a at the recording / reproducing condensing point 3 b irradiates the control groove 53 formed on the carrier substrate 56. Since the light at this time is light away from the focal point, it has a spread defined by the NA of the objective lens. An irradiation circle 4 is formed on the carrier substrate by the spread and irradiated light. The detection side image plane formed by the objective lens 10 of the control groove 53 irradiated with the irradiation circle 4 on the carrier substrate is closer to the detection lens 11 than the detection side condensing point 9. 5 is imaged. Further, the light that has been narrowed and transmitted on the recording film 51a forming the irradiation circle is then reflected and diffracted by the control groove 53 on the carrier substrate. When the thickness of the separation layer 52 is 2 μm when viewed from the objective lens 10, the reflected diffracted light has a zero-order light source at a position 2 μm from the surface of the carrier substrate 56, and the light emitted from this is on the carrier substrate 56. It appears to be diffracted by the formed control groove 53. Meanwhile ± 1 order diffracted light appear to come above the 0-order light is the control groove by the diffracted light has a light source at a distance only diffraction angles thus generated to the grid by the cycle of the control groove from which ± 1-order diffracted light (This light source is hereinafter referred to as ± primary light source).

  Since the diffraction angle by the control groove 53 is given by λ / P, it becomes 66.3 degrees from the above-mentioned numerical value. Therefore, the ± 1st order light source of ± 1st order diffracted light is perpendicular to the 4.55 μm optical axis from the 0th order light source. It seems to exist in a distant position.

Now, when the optical configuration in FIG. 1 is used, the respective light source positions on the disk carrier side measured from the recording film 51a have a magnification (lateral magnification) of 60/3 = 20 in the direction perpendicular to the optical axis on the detection side. On the other hand, a deviation in the direction of the optical axis can be set at a position multiplied by a magnification of 20 ² = 400 (vertical magnification) on the connection side.

  Accordingly, the zero-order light source and the ± first-order light source formed in the disk carrier substrate are 4 μm apart in the axial direction and 4.55 μm in the axial perpendicular direction from the recording / reproducing condensing point 3b, respectively. Each light source image is formed at the position of the condensing surface 7 closer to the detection lens 11 than the detection side condensing point 9.

  Accordingly, the image 7b of the zero-order light source can be formed in the center 7b of the light collection surface 7 away from the detection side light condensing point 9 in the axial direction of 4 × 400 = 1600 μm, that is, 1.6 mm.

  Further, the ± first-order light source image is 4.55 × 20 = 91 μm away from the image 7b and can be made into images 7a and 7c.

  On the other hand, the image on the detection side by the objective lens 10 of the control groove 53 on the disk carrier is 2 μm away from the recording / reproducing condensing point 3b in the axial direction, so that 2 × 400 = 800 μm, that is, 0.8 mm away from the detecting side condensing point 9. An image is formed on the detection-side image plane 5.

  FIG. 2 shows a method of recording on the adjacent recording film 51b using the signal groove 57 continuous on the recording film 51a by the method described above. At this time, the recorded signal pit row on 51a is used as a signal groove, a track control signal is obtained using an image formed from this control groove instead of the above-mentioned control groove, and the recording / reproducing condensing point 3b is controlled by a control means (FIG. (Not shown).

  In order to move the recording / reproducing condensing point 3b on the recording film 51b which is now 2 μm away, the objective lens 10 is moved in the direction of the arrow by 2 μm, and the distance between the objective lens 10 and the detection lens 11 is only 2 μm. Although narrowed, the image position on the detection side described above for the above-mentioned reason is maintained. Accordingly, the detection side image position 5 does not move even if the objective lens moves.

  Let us consider what kind of image can be specifically formed on the detection-side image plane 5.

  Since the objective lens 10 uses NA of 0.85, the light taking-in angle is 58.2 degrees, while the diffraction angle of the light diffracted by the control groove 53 and the signal groove 57 is 66.3 degrees. A vignetting phenomenon occurs in which part of the light cannot be captured.

  Next, the vignetting phenomenon will be described with reference to FIG.

  A light source 15 is a zero-order or ± first-order light source formed in the carrier substrate described above. Accordingly, the optical axis center line 14a of the + 1st order light source by the + 1st order diffracted light forms an angle of 66.3 degrees with the optical axis center line 16 of the 0th order light source. On the other hand, the center line 14b indicates the optical axis center line of the −1st order light source. Since the + 1st order light source spreads around the optical axis center line 14a at a spread angle of 58.2 degrees, the range from the + 1st order diffracted light spreading limit 18a to the light beam 17a connecting the end of the objective lens 10 is taken into the objective lens 10. Will be. Similarly, the -1st order diffracted light is captured from the light beams 18b to 17b, but cannot be captured otherwise. Therefore, in this case, the control groove image 20 on the detection-side image surface 5 no longer overlaps the + 1st order diffracted light and the −1st order diffracted light as shown in FIG.

  In this case, the left half is overlapped with 0 and + 1st order diffracted light, and the right half is overlapped with 0 and −1st order light.

  Next, it will be considered how the interference image formed on the detection-side image plane 5 is.

  FIG. 9B shows the relationship between the condensing surface 7 that is the detection-side light source image surface and the detection-side image surface 5. In the figure, 5a and 5a 'represent points on the detection-side image plane 5. The more the current points 5a and 5a 'are outside, the greater the difference between the 0th-order light source and the -1st-order light source, and the greater the phase difference due to the optical path difference. The interference pattern is repeated every time the phase difference becomes 2π.

  In addition, the interference pattern on the detection-side image plane 5 is obtained by multiplying the repetition pitch of the control grooves and signal grooves on the multilayer disk carrier by the lateral magnification by the optical system described above.

  Accordingly, if the pitch on the disk is now 0.35 μm, repeated fringes of vertical stripes are generated at a pitch of 0.35 × 20 = 7 μm.

  Further, since the irradiation circle 4 formed by passing through the recording film 51a by the objective lens 10 is 6.4 μm, about 18 control grooves 53 are inserted therein. Since the image in this detection system has an image magnification of 20 times, one control groove has a width of 7 μm, and the diameter of the image is 128 μm.

  FIG. 7 shows a pattern that can be seen on the detection-side image plane 5 by collecting the above information.

  Next, it will be considered how the interference pattern becomes if the control groove and signal groove move laterally.

  When the lateral movement of the control groove and signal groove occurs, the phase relationship between the 0th order light source and the ± 1st order light source changes.

  FIG. 9A shows the phase relationship between the ± first-order light source and the zero-order light source generated in the control groove and the signal groove.

  Here, the axial lengths of the 0th-order light and the ± 1st-order diffracted lights represent the respective light intensities.

  The angle θ formed by the 0th order light and the ± 1st order light varies depending on the depth of the diffraction groove. When the groove depth is λ / 4, it is 90 degrees, and when the groove depth is λ / 2, it is 180 degrees. Therefore, the phase difference of ± first-order diffracted light is 180 degrees and 0 degrees, respectively.

  As described above, the angle θ is determined by the phase difference between the control groove and the signal groove, but a multilayer disk carrier generally cannot take a sufficient phase difference. This is because, if a sufficient phase difference is taken, the diffraction loss of light increases in the recording layer, so that the necessary recording light power does not reach the inner recording film.

  Therefore, the value of θ shown in FIG. 9A is sufficiently smaller than 45 degrees.

Now, when the control groove or the signal groove moves left and right, the ± first-order light rotates while maintaining the angle 2θ with respect to the zero-order light. Now, the control groove, or by a signal groove to cause transverse movement from the center of the recording and reproducing focal point, for example, + 1-order diffracted light in FIG. 9 (a) is a shifted towards zero order light and the phase is small, Fig. From 9 (b), in 5a ′, the interference pattern moves toward the direction where the optical path difference between the 0th-order light and the + 1st-order light is small, that is, toward the center.

On the other hand, in terms of 5a interference pattern in the opposite direction to move the 0-order light and the direction in which the optical path difference is larger phase difference of -1 order light from the size Kunar 0 order light and -1 order light, that is, the center portion .

  Accordingly, since the interference pattern on the image formation is laterally moved by the movement of the control groove and the signal groove in this way, the groove control signal can be obtained from this lateral movement.

  By obtaining this groove control signal, it is possible to control the recording / reproducing light condensing point and to accurately run on the control groove on the adjacent surface or the signal groove.

  Next, a method for obtaining the groove control signal from the interference pattern will be described.

  FIG. 4 shows a specific configuration for obtaining the groove control signal.

  In the case of this figure, the light-receiving surface of the two-divided light detector 31 is disposed substantially at the position of the detection side image surface 5. A glass plate 32 is installed so as to be in close contact with the photodetector, and a grating 33 is formed on one surface with a light absorbing material or a metal reflecting film.

  The two-part photodetector 31 includes two photodetectors 31a and 31b. The groove control signal is obtained from this differential output. By using the differential output, it is possible to reduce the influence of fluctuations in reflected light from the disk carrier and fluctuations in light quantity due to the light source itself. FIG. 7 shows the positional relationship between the grating element 33 according to the present invention and the interference pattern generated by the 0th and ± 1st order light sources formed by the control groove and signal groove in order to obtain the groove control signal by the two-divided photodetector 31.

  As shown in the figure, the diffraction pattern is symmetric and moves in the left-right joint direction as described above for the movement of the control groove and signal groove, and the groove control signal must be output differentially as the signal. In addition, the grating must be arranged symmetrically with respect to the center line of the photodetector.

Control groove by placing a grid 33 in this manner, or the signal grooves laterally moved, interference bright photodetector 31a disposed on the left side of FIG. 7 when the interference pattern on the detector side, for example, cause leftward movement Wataru pattern 10 0, the output of 31a will be a lot deviates from the grating 33 enters the optical detector 31a is increased.

On the other hand, since many bright interference patterns 100 are superimposed on the photodetector 31b by the grating 33, the light output is reduced .

  Thus, by arranging the grating 33 and the interference pattern, the groove control signal can be accurately obtained from the output of the two-divided photodetector 31.

  As described above, the present invention intends to detect a groove control signal by forming an interference pattern on the detection-side image surface 5 and moving the groove image 20 left and right. Next, the case where recording on the recording film 51a is completed over the entire surface as shown in FIG. 2 and recording is performed on the recording film 51b will be described. When recording the recording layer of the recording film 51b, the objective lens 10 moves to the right by 2 μm (when the disc inner layer interval is 3 μm) from FIG. By this movement, the recording / reproducing condensing point 3b moves onto the recording film 51b. A part of the light at the recording / reproducing condensing point 3b formed on the recording film 51b passes through the recording film 51a and irradiates the recorded recording film 51a. In this recorded recording layer, a recording signal is recorded as a difference in refractive index of the recording film by the recording signal light, and this functions exactly like the control groove 53. Since the groove control signal is generated based on the principle described above, the recording / reproducing light condensing point 3b can be controlled based on this signal. Therefore, the next signal can be recorded immediately above the recorded recording film 51a. It becomes possible.

  By repeating this, only the control groove formed on the carrier substrate is started by controlling the recording / reproducing condensing point while forming an accurate track with an accurate track pitch on the multilayer recording film 51. A signal can be recorded on each recording film.

  In the case of this method, since nothing is added to the exit side of the objective lens 10, there is a feature that no light loss occurs and there is a feature that no load is applied to the recording light source. Also, since the recorded signal groove of the immediately adjacent recording film 51 is used as the control groove 53, the track deviation due to the disc tilt can be almost ignored.

  As shown in Fig. 1, the image position is 0.8mm in the air length from the condensing point of the 0th and ± 1st order light, but when the glass plate is inserted as in this example, the image is behind by sinθ / n1. A so-called spherical aberration occurs. Accordingly, it is necessary to correct the distortion due to the spherical aberration and correct the grating 33. However, since the NA of the detection system is small, this correction is extremely small, and in this example, a grating having a pitch ratio of 6 μm and an aspect ratio of 1 is basically formed on the glass surface. It only has to be done. This pattern is shown in FIG. What is necessary is just to install the 2-part dividing photodetector 31 shown in FIG.6 (c) so that this glass surface may be contacted.

  FIG. 5 shows an example of the invention that positively utilizes the fact that the optical path length changes and the groove width changes due to the refractive index change in the flat plate.

The method for obtaining the groove control signal by irradiating the adjacent control groove and signal groove with the transmitted light from the recording film at the recording / reproducing condensing point and using the movement of the interference pattern of the diffracted light from these grooves is as follows. When the distance between the surfaces fluctuates, there is a disadvantage that an error occurs in the groove control signal due to a change in the period of the interference pattern.

  The present invention is an example made to reduce this drawback.

  In this example, liquid crystal is used inside instead of the transparent substrate on which the lattice is formed. By forming the transparent electrodes 41a and 41b on both sides and changing the voltage to ignite on both sides, the position of the detection-side image plane 5 can be equivalently changed. It is possible to suppress changes in the width of the.

(Embodiment 2)
In the first embodiment, an example is described in which a grating is formed and the groove control signal is obtained by closely attaching the grating to the two-divided photodetector. In this embodiment, the photodetector is divided into a grating instead of inserting the grating. Thus, a groove control signal is to be obtained.

  This embodiment is shown in FIG. Usually, the separation interval and the photodetector width of the photodetector are required to be 6 μm or more due to manufacturing problems, and therefore, in the present example, the width is increased. In this example, the widths of the photodetectors are 9 μm, and the intervals between the photodetectors are 9 μm.

  Accordingly, the right end of the light detector is located at the center of the bright portion 100 of the interference pattern in the block of the light detection output −31, and the right end of the light detector is arranged at the center of the dark portion 101 of the interference pattern in the block of the light detection output +31. ing. When the recording / reproducing light condensing point is deviated from the center of the control groove or signal groove on the adjacent surface from this state, the interference pattern moves. For example, when the interference pattern moves to the left due to the occurrence of the deviation from the groove center, the interference pattern on the detection-side image plane 5 moves 1.5 μm (when the recording / reproducing condensing point runs from the groove center to the center between the grooves). Think. In this case, the output of the light detector 31a gives the highest light detection output +31 since only one dark portion 101 is included in the light detector. On the other hand, since the light detector 31b includes two dark portions 101, the lowest light detection output -31 is given. From such a signal change, the movement of the control groove or signal groove can be detected, and the groove control signal of the recording / reproducing condensing point can be obtained.

  With this device, the photodetector width and interval are 9 μm, so that there is no problem in manufacturing the photodetector.

(Embodiment 3)
An embodiment of the present invention will be described with reference to FIG. In the example of the present invention attempts to create a control focal point 3a to actively control groove 53 by putting the hologram element 201 not only formed by the objective lens 10 simply reproducing condensing point 3b as the the invention To do. The recording / reproducing condensing point 3b is formed by the light passing through the hologram element 201 as it is, and the control condensing point 3a is formed by using the first-order diffracted light generated by the hologram element 201 (assuming that the diffraction lens is a concave lens) .

  Next, the light reflected from the control groove 53 returns to the objective lens 10 again. At this time, the diffracted light is condensed by the hologram element 201 on a surface farther than the detection lens 11 that is 0.4 mm away from the diffraction image surface 6 shown in the first embodiment. On the other hand, as described in the embodiment, on the diffraction image surface, the recording / reproducing light condensing point 3b is transmitted through the recording film 51b and the light reflected by the recording film 51a is condensed, and the ± first-order diffracted light is collected at a distance of ± 91 μm. Is done. When the control condensing point 3a is separately formed to obtain the groove control signal as in the present invention, this ± first-order diffracted light becomes an obstacle. Therefore, in this case, as shown in FIG. 10, a light shielding plate 211 for shielding ± first-order diffracted light is required. At this time, the conventional fur-field push-pull detection can be used as the groove control signal. The position of the photodetector at this time may be arranged at an appropriate position away from the detection lens from the diffraction image plane 6.

(Embodiment 4)
In the above embodiment, the method of obtaining the groove control signal using the adjacent control groove 53 or using the adjacent recorded signal as the control groove has been described. The above method has the great advantage that the optical system is simple and has little optical loss. On the other hand, if signal pits and meandering of the recorded signal occur due to some disturbance, this is gradually accumulated and the top surface (carrier substrate groove control signal When a signal is recorded on the recording film 51 (farthest from the head), it is conceivable that a disadvantage that the meandering of the groove is too large occurs. In such a case, it is considered that a method of constantly referring to the control groove 53 formed on the carrier substrate 56 is effective. The present embodiment has been made in consideration of adapting to such a situation.

  An embodiment of the present invention will be described with reference to FIG.

  The first-order diffracted light 24 generated by the hologram element 201 inserted in the reciprocating optical path 26 has a concave lens characteristic. If the focal position of the concave lens coincides with the focal position of the condenser lens 23, the first-order diffracted light becomes parallel light after passing through the condenser lens 23, enters the objective lens 10 and irradiates the control groove 53 on the carrier substrate. To do. On the other hand, the 0th-order diffracted light 25 that passes through the hologram element 201 passes through the condenser lens 23 and then becomes convergent light as shown in FIG. Therefore, this light constitutes the recording / reproducing condensing point 3b.

  An operation method when the recording / reproducing condensing point 3b is moved from the recording film 51a of this example to the recording film 51b will be described. In order to move the recording / reproducing condensing point 3b to the recording film 51b, the objective lens 10 is first moved to the 2 μm carrier substrate 56 side as usual. This operation not only moves the recording / reproducing light condensing point 3b from the recording film 51a to 51b, but also moves the control light condensing point 3a by 2 μm into the carrier substrate. The hologram element 201 is moved away from the condenser lens 23 in order to restore the moved control condensing point 3a. By this operation, the first-order diffracted light 24 is slightly converged, so that the control condensing point 3a is pulled back to the recording film 51b side, and the control groove 53 is irradiated again accurately.

  In such an operation, only one light source is separated by the hologram element 201, and the two condensing points (recording / reproducing condensing point 3b, control condensing point 3a) are shifted from the optical axis center by the movement of the hologram element 201. Such an error does not occur.

  In this description, the distance between the hologram element 201 and the condenser lens 23 is changed (moving 27), and the two focal positions are changed. However, the spherical aberration generated in the objective lens 10 is very large only by this action. May be larger. Therefore, in order to reduce this problem, the problem can be reduced if the block of the hologram element 201 and the condenser lens 23 is moved 28.

(Embodiment 5)
In the first and second embodiments, the present invention is applied to an optical system for generating a control signal for controlling the recording / reproducing light condensing point 3b from a control signal on a control groove on an adjacent carrier substrate or a recorded signal sequence formed on an adjacent recording layer. An example was given. In the third embodiment, the embodiment of the present invention has been described with respect to an optical system for generating a control signal for controlling the recording / reproducing light condensing point 3b from the control groove on the carrier substrate which is not adjacent. However, in the first and second embodiments, when signal recording is sequentially performed on the recording film 51 that is separated from the carrier substrate 56, the more the vibration or the like enters when the signal is recorded on the recording film 51 until then, the more the influence is. Accumulated and mixed. Also in the embodiment 3 it would cause a Re not a position if the inclination enough information recording medium further away is responsible body substrate 56 and the recording film 51.

  An embodiment of the present invention will be described in detail with reference to FIG.

  Conventionally, since the innermost peripheral portion of the information record carrier is unlikely to have a tilt error of the information record carrier, recording and reproduction should be started from the innermost peripheral portion.

  As an embodiment of the present invention, a signal is written to the recording film 51 for one round of the inner circumference by the method described in the first, second, and third embodiments. Next, a groove control signal is obtained based on Examples 1, 2, and 3 while sending the optical head 106 to the outer peripheral portion of the information record carrier 105. The obtained detection signal and an example of the detection circuit of the present invention are used. When a large difference occurs between two signals while comparing voltages generated from a certain feed accuracy, a method of writing on the basis of a signal generated from the feed accuracy is used.

  In this embodiment, as a feed signal, a reference pulse signal 109 sent to the pulse motor 108 and the detected groove control signal 110 are input to the comparison circuit 107, and when there is a large difference between the feed signals, the optical head 106 is used. In this case, it is determined that the vibration is caused by external vibration, and only the electric signal is sent to the pulse motor 108 at that time. When this difference is small, the groove control signal 110 is sent. By using this embodiment, the meandering of the recording signal due to the disturbance generated during recording on a certain recording layer was greatly reduced.

  The present invention is an information carrier comprising a carrier substrate, at least one recording film, and a recording film separation layer, wherein one side of the carrier substrate has a control groove partially, and the one side is A part of the incident light that has passed through and reached the light incident surface of the information carrier is reflected, the control groove gives a reflection having a phase different from that of the reflected light on the one surface, and the recording film has the incident light. It can be used in an information recording / reproducing apparatus for recording and reading signals on an information carrier having a material that reflects a part of the incident light and gives a reflected signal having a phase different from that of the reflected light from the recording film. is there.

The figure which shows 1st Example concerning this invention The figure which controls the recording-reproducing condensing point using the recorded signal in 1st Example concerning this invention. Figure showing vignetting by the objective lens of ± 1st order diffracted light Arrangement of grating and two-divided photodetector in the first embodiment of the present invention The figure which shows the structure made in order to reduce the groove | channel control signal error when the space | interval of a surface changes by forming the flat plate inside by the liquid crystal in 1st Example concerning this invention, and forming a transparent electrode on both surfaces. FIG. 3 is an assembly diagram showing an interference pattern on the detection-side image plane 5 according to the first embodiment of the present invention and the arrangement of the grating and the two-divided photodetector according to the present invention. The top view which shows the arrangement | positioning of the interference pattern on the detection side image surface 5 by the 1st Example concerning this invention, the grating | lattice concerning this invention, and a 2-part dividing photodetector The figure which shows the 2nd Example concerning this invention. The figure explaining the interference pattern on the detection side image surface 5 The figure which shows the 3rd Example concerning this invention. The figure which shows the 4th Example concerning this invention. Conventional structure of multilayer disk carrier The figure which shows the prior art example of the recording / reproducing optical system of a multilayer optical information record carrier The figure which shows Example 5 concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Semiconductor laser 2a Collimator lens 3 Light condensing point 3a Control groove condensing point 3b Recording / reproducing condensing point 4 Irradiation circle 5 Detection side image surface 6 Diffraction image surface 7 Condensing surface 9 Detection side condensing point 10 Objective lens DESCRIPTION OF SYMBOLS 11 Detection lens 12 Direction 13 Optical axis 14a Optical axis center line 14b Center line 15 Light source 16 Optical axis center line 17a, 17b Light beam 18a Spreading limit 18b Light beam 20 Control groove image 23 Condensing lens 24 First order diffracted light 25 0th order diffracted light 26 Reciprocating Optical path 27 Movement 28 Movement 31 Two-part photo detector 31a Right photo detector 31b Left photo detector 32 Glass plate 33 Grating 41a, b Transparent electrode 50 Protective layer 51 Recording film 51a Recording film 51b Recording film 52 Separating layer 53 Control groove 56 Carrier substrate 57 Signal groove

Claims (7)

A carrier substrate having a control groove formed by a groove surface and a non-groove surface on one side, a separation layer formed on the control groove of the carrier substrate, and a multilayer having a repetition of a recording film formed on the separation layer With a recording film,
The recording film on which the signal is recorded has a signal groove formed from a recorded surface and an unrecorded surface,
The incident light that has passed through the multilayer recording film and has reached the carrier substrate, the reflected light from the groove surface is different in phase from the reflected light from the non-groove surface,
The reflected light from the recorded surface with respect to the incident light that has passed through a part of the multilayer recording film and reached the recording film has a phase different from that of the reflected light from the unrecorded surface. A multilayer disk carrier information recording / reproducing apparatus for reproducing,
One light source for irradiating the multilayer disc carrier with light for at least one of recording and reproduction;
An objective lens that is installed between the multilayer disc carrier and the light source and forms a recording / reproducing condensing point that is a condensing point for performing at least one of recording and reproduction of the signal;
Of the light that forms the recording / reproducing condensing point, the recording film transmitted light that has passed through the recording film on which the recording / reproducing condensing point is formed is applied to the recording film on which the recording / reproducing condensing point is formed. Multi-layer disc carrier information recording / reproduction comprising control means for controlling the position of the recording / reproducing condensing point in the left-right direction on the recording film using reflected light from the adjacent control groove or signal groove apparatus. A two-part photodetector for receiving the reflected light;
A light transmission blocking grating composed of a plurality of linear portions disposed in front of the two-part photodetector for blocking light transmission;
The control means is a control signal obtained from a differential signal output from each of the two photodetectors of the two-divided photodetector, and the recording / reproducing focusing point moves on the control groove or the signal groove. The multi-layer disc carrier information recording / reproducing apparatus according to claim 1, wherein the control is performed so that   3. The multilayer disc carrier information according to claim 2, wherein the light transmission blocking grating is formed on one surface of a flat plate transparent to the reflected light, and the one surface and the two-divided photodetector surface are in close contact with each other. Recording / playback device.   The contact surface between the two-split photodetector surface and the flat plate is disposed at a position where the reflected light from the control groove or the signal groove is imaged after passing through the objective lens. The multilayer disc carrier information recording / reproducing apparatus as described. The flat plate includes a liquid crystal provided as a central member, and two transparent electrodes provided so as to sandwich the liquid crystal,
5. The multilayer disc carrier information recording / reproducing apparatus according to claim 4, wherein the control means reduces an error of the control signal by applying a potential between the electrodes of the transparent electrode. A light detector having a lattice shape, installed at a position where the reflected light forms an image after passing through the objective lens;
2. The multilayer according to claim 1, wherein the control means performs control so that the recording / reproducing condensing point moves on the control groove or the signal groove with a differential signal of the photodetector having the lattice shape. 3. Disc carrier information recording / reproducing apparatus.   The multi-layer disc carrier according to claim 6, wherein the photodetector having the lattice shape is a plurality of rod-like photodetectors arranged in a longitudinal direction so as to be parallel to a parallel direction of the interference pattern as the image. Information recording / reproducing apparatus.

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