Multilayer optical recording medium having plurality of reflecting units formed on parts recording layers

A multilayer optical recording medium includes a plurality of recording layers that are laminated and have recording layer forming units into which information is recorded. Reflective film forming units are formed on parts of the respective recording layers and have a reflectance ratio sufficient to make a servo loop of a focus servo into a servo close condition. Reflective film forming units of the respective recording layers are arranged at respectively different positions.

BACKGROUND OF THE INVENTION

1) Field of the Invention

The present invention relates to a multilayer optical recording medium having multilayer recording layers and an optical pickup device that records and replays the multilayer optical recording medium.

2) Description of the Related Art

In an optical recording medium such as a digital versatile disk (DVD), two layers of recording layer are formed, which allows for both a high recording density and a high capacity. To further increase the capacity of optical recording medium using an optical system of a higher NA (Numerical Aperture) and a light source of a short wavelength, a multilayer optical disk having three or four layers of recording layers has been proposed. In such an optical disk having several layers of recording layers, a spacer area is formed between a recording layer and another recording layer, and a semitransparent reflective film is formed on the entire surface of each recording layer.

Meanwhile, in recent years, to achieve still higher recording density and higher capacity in optical recording medium, the basic technology has been developed of a three-dimensional multilayer optical memory as a next generation optical recording medium having recording layers from around 10 layers to around 100 layers. As the recording layers of this three-dimensional multilayer optical memory, a photo polymer is employed that does not have a reflective film.

In the conventional multilayer optical memory, a structure is employed where a reflective film is not arranged on each recording layer, so as to reduce transmission loss of light for recording and reproducing at a maximum. Therefore, the reflectance ratio of each recording layer becomes the same as viewed from the side of a recording pickup. In addition, in this optical memory, to restrict as much as possible the influence of spherical aberration, the thickness is made extremely small of an intermediate layer (space area) that is formed between recording layers, i.e., interlayer space.

In the conventional optical memory with no reflective film in each recording layer, it is difficult to make a servo loop of a focus servo into a servo close condition at the side of a recording and reproducing device. Furthermore, because a reflective film is not formed on each recording layer and the interlayer space between recording layers is small, a focus error signal cannot be separated between layers, and it is difficult to make an interlayer jump that moves between layers (focus jump). Therefore, making a servo loop of a focus servo into a servo close condition and move control between layers are the issues that need consideration.

SUMMARY OF THE INVENTION

A multilayer optical recording medium according to an aspect of the present invention includes a plurality of recording layers formed as a laminate, each recording layer having a recording layer forming unit on which information is recorded. Reflective film forming units, which have a higher reflectance ratio than that of the recording layer forming units, are formed on parts of the recording layers.

An optical pickup device according to another aspect of the present invention irradiates light from a light source via an objective lens to the above multilayer optical recording medium and receives light reflected form the multilayer optical recording medium using a signal detecting unit. The optical pickup device includes a focus servo unit that controls focus servo of the objective lens on the basis of a focus error signal; and a controlling unit that controls making a servo loop of a focus servo into a servo close condition in each recording layer of the multilayer optical recording medium by use of the reflective film forming units of the respective recording layers.

An optical pickup device according to still another aspect of the present invention irradiates light from a light source via an objective lens to the above multilayer optical recording medium and receives light reflected form the multilayer optical recording medium using a signal detecting unit. The optical pickup device includes a focus servo unit that controls focus servo of the objective lens on the basis of a focus error signal; a tracking servo unit that controls tracking servo of the objective lens on the basis of a tracking error signal; and a controlling unit that changes over the focus servo gain in the focus servo control at the recording layer forming units of the multilayer optical recording medium and the tracking servo gain in the tracking servo control so that the respective servo gains are larger than the respective servo gains at the reflective film forming units.

An information reproducing device according to still another aspect of the present invention includes the above optical pickup device; and a demodulating unit that demodulates a detection signal of the signal detecting unit of the optical pickup device.

A method according to still another aspect of the present invention is a method for manufacturing a multilayer optical recording medium wherein a plurality of recording layers are laminated. The method includes depositing a reflective film onto an intermediate layer sheet where a mask pattern is laminated thereon to form reflective film forming units on part of the intermediate layer sheet; first laminating and jointing a recording layer sheet onto the intermediate layer sheet on which the reflective film has been formed; second laminating a plurality of sheets of the jointed intermediate layer sheet and the recording layer sheet so that the reflective film forming units thereof are in a specified arrangement relation between respective layers; and sandwiching the second laminated sheets between a substrate layer sheet and a protection layer sheet and jointing them.

DETAILED DESCRIPTION

Exemplary embodiments of a multilayer optical recording medium and an optical pickup device according to the present invention are explained in more detail in reference to the accompanying drawings.

FIG. 1is a schematic of a multilayer optical recording medium (hereinafter, “optical media”) according to an embodiment of the present invention. In this optical media, on a transparent substrate1, many recording and reproducing layers (hereinafter, referred to simply as recording layers) L1, L2, L3, . . . , Ln are formed. A first recording layer is referred to as L1, a second recording layer as L2, . . . , and a n-th recording layer is referred to as Ln. On parts of the respective recording layers L1to Ln of the optical media, reflective film forming units W1, W2, W3, . . . , Wn are formed of a circular shape, rectangular shape and the like, having a reflectance ratio sufficient to make a servo loop of a focus servo into a servo close condition. Making a servo loop of a focus servo into a servo close condition means an action to make the status where a focus servo is not working according to a focus error signal into the status where the focus servo is working.

The reflective film forming units W1to Wn are arranged at least at one unit (plural units also available) of each of the recording layers L1to Ln. In this case, when an X axis and a Y axis are set in the direction parallel with the recording layers L1to Ln, the respective reflective film forming units W1to Wn are arranged in the X and Y positions that do not overlap the reflective film forming units of other recording layers when viewed from an optical pickup. Namely, the reflective film forming units W1to Wn of each of the recording layers L1to Ln are arranged on respectively different X and Y positions.

In the optical media, markings or notches (not illustrated therein) are arranged to specify the standard position thereof, and the respective reflective film forming units W1to Wn are arranged, for example, according to a preset specific rule from the specific standard position of the optical media. Therefore, at the side of an optical pickup, the standard position is specified in recognition of the markings and notches, then the optical pickup is moved by specified amounts in the X and Y directions that are determined according to the specific rule from the standard position. As a result, it is possible to move the optical pickup to the position corresponding to the reflective film forming units W1to Wn of a desired recording layer.

FIG. 2is a waveform of a focus error signal at the moment when the objective lens of the optical pickup is arranged on the position A in X and Y directions where there is the reflective film forming unit W3on the third recording layer L3, and the objective lens is moved from a position away from the optical media ofFIG. 1to a position close to the optical media.FIG. 3is a waveform of a focus error signal at the moment when the objective lens of the optical pickup is arranged on the position B where there is the reflective film forming unit W2on the second recording layer L2, and the objective lens is moved from a position away from the optical media ofFIG. 1to a position close to the optical media.

The optical pickup is arranged at the side of the first recording layer L1. The focus error signal basically shows zero level at a focused status where the focus of the objective lens is focused onto a recording surface (more precisely, in this case, at a zero cross point from the maximum point to the minimum point), and draws an S-shaped curve with the zero level from the maximum point to the minimum point as the focused point at the center thereof. Then, the area from the maximum point to the minimum point in one S-shaped curve is roughly the area where a focus servo is worked, namely, a focus servo loop is closed.

In the position A, the reflective film forming unit W3exists on the third recording layer L3. Therefore, in the focus error signal shown inFIG. 2, the signal level thereof and the level change becomes large when the focus position of the objective lens is near the third recording layer L3. In the position B, the reflective film forming unit W2exists on the second recording layer L2. Therefore, in the focus error signal shown inFIG. 3, the signal level thereof becomes large when the focus position of the objective lens is near the second recording layer L2.

Accordingly, by use of the S-shaped portion where the signal level change appears large, it is possible to easily make a servo loop of a focus servo into a servo close condition on the respective recording layers L1to Ln, by use of existing technologies employed in a DVD or a CD. Namely, when moved to a certain recording layer, the focus servo is released once, and the focus is moved to the position where there is a reflective film forming unit of a recording layer of the move destination. Spherical aberration that is supposed to occur at the targeted recording layer is compensated. Thereafter, a process is performed to set the focus servo on the recording layer of the move destination. InFIG. 2andFIG. 3, as for the focus error signal at the moment when the focus point of the objective lens is positioned on another recording layer where the reflective film forming unit W3does not exist, the level change thereof is extremely small. Therefore, it is very difficult to make a servo loop of a focus servo into a servo close condition by use of this unit.

FIG. 4illustrates another embodiment of an optical media. In this optical media, the reflective film forming units W1to Wn of the recording layers L1to Ln that are adjacent to each other are arranged so that parts thereof overlap each other when viewed from the side of the optical pickup. For example, the reflective film forming unit W1of the first recording layer L1and the reflective film forming unit W2of the second recording layer L2overlap each other in the area D12, the reflective film forming unit W2of the second recording layer L2and the reflective film forming unit W3of the third recording layer L3overlap each other in the area D23, and the reflective film forming unit W3of the third recording layer L3and the reflective film forming unit W4of the fourth recording layer L4overlap each other in the area D34.

FIG. 5is a waveform of a focus error signal at the moment when the objective lens of the optical pickup is arranged on the position A in the X and Y directions where there is the reflective film forming unit W3on the third recording layer L3, and the objective lens is moved from a position away from the optical media ofFIG. 4to a position close to the optical media.FIG. 6is a waveform of a focus error signal at the moment when the objective lens of the optical pickup is arranged on the position B corresponding to the area D23where the reflective film forming unit W2of the second recording layer L2and the reflective film forming unit W3of the third recording layer L3overlap each other, and the objective lens is moved to a position close to the optical media shown inFIG. 4.

As shown inFIG. 5, when the pickup is positioned at the position A, the reflective film forming unit W3only exists on the third recording layer L3. Therefore, in the same manner as inFIG. 2orFIG. 3, the signal level thereof and the level change becomes large when the focus position of the objective lens is near the third recording layer L3. Accordingly, by use of the S-shaped portion where the signal level change appears large, it is possible to easily make a servo loop of a focus servo into a servo close condition on the respective recording layers L1to Ln in the same manner explained previously.

Meanwhile, as shown inFIG. 6, when the pickup is positioned on the position B, because the reflective film forming unit W3of the third recording layer L3and the reflective film forming unit W4of the fourth recording layer L4are in the focus error signals, two S-shaped portions occur continuously where the signal level change appears large. Namely, in the case of the optical media shown inFIG. 4, because the respective reflective film forming units W1to Wn are arranged so that parts thereof overlap each other, by use of the overlapped units, even if the interlayer space between the respective recording layers is small, it becomes possible to separate the focus error signal between the respective recording layers. Accordingly, in this case, when an interlayer jump is made from the third recording layer L3to the fourth recording layer L4, the normal focus jump procedures that are used in a DVD may be employed. In the focus jump procedures, a series of processes is performed, such as opening the focus servo loop, output of a kick pulse for move to a target layer, detection of approach to the target layer on the basis of monitoring the focus error signal, output of a brake pulse, and closing the focus servo loop.

FIG. 7is a schematic of yet another optical media. In the optical media shown inFIG. 7, the reflective film forming units are almost completely overlapped in adjacent plural (several) recording layers. In this case, the reflective film forming unit W1of the first recording layer L1, the reflective film forming unit W2of the second recording layer L2, and the reflective film forming unit W3of the third recording layer L3are made into almost the same size and shape, and are arranged in almost the same X and Y positions. Further, the reflective film forming unit W4of the fourth recording layer L4, the reflective film forming unit W5of the fifth recording layer L5, and the reflective film forming unit W6of the sixth recording layer L6are made into almost the same size and shape, and are arranged in almost the same X and Y positions. The arranged positions of the reflective film forming units W1to W3are different from those of the reflective film forming units W4to W6.

More concretely, in the optical media shown inFIG. 7, with plural recording layers that are continuously adjacent as one group, the respective recording layers are divided into plural groups, so that the reflective film forming units of plural recording layers belonging to a same group should be arranged at the same position, and reflective film forming units belonging to different groups should be arranged at different positions.

FIG. 8is a waveform of a focus error signal at the moment when the objective lens of the optical pickup is arranged on the position A in X and Y directions where there are the reflective film forming units W4to W6, and the objective lens is moved closer to the optical media shown inFIG. 7.FIG. 9is a waveform of a focus error signal at the moment when the objective lens of the optical pickup is arranged on the position B in X and Y directions where there are the reflective film forming units W1to W3, and the objective lens is moved closer to the optical media shown inFIG. 7.

In the optical media shown inFIG. 7, the reflective film forming units are overlapped in plural recording layers that are continuously adjacent (in a unit of one group). Therefore, as shown inFIG. 8andFIG. 9, in a focus error signal, plural pieces (three pieces in this case) of S-shaped portions occur continuously where the signal level change appears large. Accordingly, in this case, when to carry out recording and reproducing to, for example, the fifth recording layer L5or the sixth recording layer L6, the focus is moved from an away position to a position close to the recording surface, the focus is positioned once near the fourth recording layer L4, and thereafter, the focus servo is closed. Then, the focus jump procedures explained previously are carried out, so that an interlayer jump may be made from the fourth recording layer L4to the adjacent fifth recording layer L5or the sixth recording layer L6. As mentioned above, in the optical media shown inFIG. 7, by making the most of the efficient focus jump procedures, access may be made to each recording layer. The reflective film forming units W1to Wn formed on partial areas of layers may be arranged at the same X and Y positions through all the layers, and movement to each recording layer may be made by use of the focus jump procedures. Further, as the shapes of the optical disk, arbitrary shapes may be employed such as a rectangular shape, circular shape, other polygonal shape, oval shape and so forth.

A first embodiment of the present invention is explained hereinafter in reference toFIGS. 10 to 16. In this first embodiment, an optical media10of a card type in a rectangular shape is employed.

FIG. 10is a schematic of the optical media10according to the first embodiment. In this optical media10, between a substrate layer11and a protection layer12, many recording layers L1to L6(six layers in this case) and intermediate layers13are laminated. On partial areas of the respective recording layers L1to L6, reflective film forming units (hereinafter, index units) W1to W6are formed having a rectangular shape of a specified size and having a reflective characteristic of a high reflectance ratio. In the respective recording layers L1to L6, areas other than the reflective film forming units W1to W6include a recording film forming unit14where information recording and reproducing are performed. The reflective film forming units W1to W6have a higher reflectance ratio than that of the recording layer forming unit14.

In this case, the reflective film forming units W1to W6are arranged like tabs in a line at the edge unit of the optical media10. The reflective film forming units W1to W6of the adjacent recording layers L1to Ln are arranged so that parts thereof are overlapped when viewed from the side of the optical pickup. In this first embodiment, the reflective film forming units W1to W6adopt the arrangement method similar to that of the optical media of the embodiment shown inFIG. 4. Because the reflective film forming units W1to W6are arranged at the edge unit of the optical media10, at the moment of access to the recording layers, the reflective film forming units W1to W6will not become obstacles. Therefore, the recording areas of the recording layers may be used effectively.

In the respective index units W1to W6, layer identification address information, which shows on which layer the index unit concerned is located, various information concerning any one of recording and reproducing or both (spherical aberration precise compensation information, light strategy information, and optimized recording and reproducing laser output information) and so forth are memorized. Therefore, by use of this record information, it becomes possible to confirm the recording layers, finely adjust and set the spherical aberration of the pickup, focus servo target value and so forth.

Spherical Aberration Precise Compensation Information

When the compensation of spherical aberration is carried out at the moment of determination of a target recording layer by use of a compensation value memorized previously in a memory of a pickup device, an aberration correcting device is driven, such as a beam expander or a liquid crystal element. However, in some cases, the cover layer thickness to the target record layer may be different owing to manufacturing fluctuations of an optical media. Therefore, if the spherical aberration precise compensation information per each optical media is recorded into the index units, and at the moment of spherical aberration compensation, compensation is performed by use of this spherical aberration precise compensation information. As a consequence, a precise spherical aberration compensation may be carried out.

Layer Identification Address Information

If the optical pickup is moved to the position where there are the index units W1to W6in an optical media, and then action control to work a focus servo is carried out, the focus servo may always be worked onto a required recording layer. In some cases, however, the focus servo cannot be worked onto a required layer owing to vibration or some external disturbance. In such a case, by use of the layer identification address information recorded in the index units W1to W6, it is possible to confirm whether the current layer is the required recording layer.

Optimized Recording and Reproducing Laser Output Information

Because this optical media10is a multilayer structure, there may be a case where laser output necessary for optimized recording and reproducing varies in the recording layers. This may occur owing to different recording sensitivity in the layers resulting from production unevenness, or owing to a different transmission ratio difference of the laser beam between a layer at the depth and a layer at the front when viewed from the side of the pickup. Therefore, optimized recording and reproducing laser output information showing the optimized recording and reproducing laser output per layer is recorded in the index units W1to W6, and at recording and reproducing, on the basis of the optimized recording and reproducing laser output information per layer recorded in the index units W1to W6, laser power is controlled per layer. Thereby, it is possible to perform recording and reproducing at high precision in each recording layer.

Light Strategy Information

In optical recording (especially in the case where a phase change medium or a pigment medium is used), to reduce distortion of a record mark owing to heat, and to reduce jitters, multi pulse modulation called light strategy is carried out and thereby thermal distribution control of record marks is carried out. A multi-pulse modulation pattern (light strategy information) varies with the sensitivity and recording power of the optical media. Therefore, it is necessary to have light strategy information per layer. Namely, at recording, multi-pulse modulation control of the laser is carried out per layer on the basis of the light strategy information per layer recorded in the index units W1to W6. Thereby, mark recording may be carried out at high precision in each recording layer.

The layer identification address information, optimized recording and reproducing laser output information, and light strategy information are respectively information peculiar to each layer. Therefore, it is useful to form a stamper peculiar to each layer, and a mark peculiar to each layer.

In addition, as the spherical aberration precise compensation information, a mark or a pit having no information may be formed on an index unit, and this pit may be replayed at the side of an optical pickup. Further, the amplitude information and error rate, jitters and so forth thereof may be measured, and on the results of this measurement, evaluation information as spherical aberration precise compensation information may be created. By use of this evaluation information, precise compensation of spherical aberration may be carried out. In this case, since this spherical aberration precise compensation information becomes information not particular to each recording layer, by use of what is formed previously on a stamper or so, a same mark or pit may be formed on each layer. Further, to create evaluation information of the spherical aberration precise compensation information, the layer identification address information, light strategy information, and optimized recording and reproducing laser output information may be replayed, and the amplitude information, error rate, jitters and so forth thereof may be measured. Thereby, the evaluation information may be prepared.

FIG. 11is a schematic of a holding and driving mechanism of a card type optical media10in a recording and reproducing device. The media holding and driving mechanism adopts an X-Y driving table method, and a ball screw22is interconnected with a pair of frame bodies20A and20B that are fixed onto the device main body, and a guide bar21is fixed thereto. At one end of the ball screw22, the rotating shaft of a step motor23is interconnected. One card holder24A is engaged to the ball screw22, and the other card holder24B is inserted to the guide bar21. The card holders24A and24B support the card type optical media10.

Meanwhile, in between a pair of supporting bodies25A and25B fixed to the device main body, a ball screw26is interconnected, and a guide bar27is fixed thereto. To one end of the ball screw26, the rotating shaft of a step motor28is interconnected. In between the ball screw26and the guide bar27, a pickup holding unit29is arranged. The pickup holding unit29supports an optical pickup30.

According to this media holding and driving mechanism, when the step motor23is rotated, the card type optical media10supported by the card holders24A and24B moves in the X direction. Meanwhile, when the step motor28is rotated, the optical pickup30moves in the Y direction.

FIG. 12is a block diagram of the entire structure of a recording and reproducing device that records and replays the card type optical media10. This recording and reproducing device has an optical pickup30, a pickup driving unit31that drives the optical pickup in the Y direction, a pickup position detecting circuit32that detects the position of the optical pickup30in the Y direction and inputs the detection signal to a controller40, and a slider servo circuit33that servo controls the movement of the optical pickup30in the Y direction according to instructions from the controller40. The step motor28, the ball screw26, the guide bar27, the pickup holding unit29, and the like inFIG. 11correspond to the pickup driving unit31.

In addition, the recording and reproducing device has a media driving unit34that drives the card type optical media10in the X direction, a position sensor35that detects the position of the card type optical media10in the X direction, a media position detecting circuit36that detects the position of the card type optical media10in the X direction on the basis of detection output of the position sensor35, and a media move servo circuit37that controls the movement of the card type optical media10in the X direction according to instructions from the controller40. The step motor23, the ball screw22, the guide bar21and the like inFIG. 11correspond to the media driving unit34.

The optical pickup30has a light source41such as a laser diode (LD), a spherical aberration compensating unit42, an objective lens driving unit43, a signal detecting unit44, and so forth. The objective lens driving unit43has a focus actuator that moves an objective lens48in the optical axis direction thereof, and a tracking actuator that moves the objective lens48in the tracking direction.

FIG. 13is a schematic of an example of the structure of an optical system in the optical pickup30. As shown inFIG. 13, the optical pickup30has a light source41that outputs light beams for recording and reproducing, a polarized beam splitter45that outputs light beams output from the light source41to a spherical aberration compensating lens42and outputs return light from the optical media10to a detector44, a spherical aberration compensating lens42(corresponding to the spherical aberration compensating unit42inFIG. 12) that may move in the optical axis direction to compensate for the spherical aberration of light beams output from the light source41, a rise prism46that polarizes light beams coming from the spherical aberration compensating lens42by 90 degrees, a quarter wavelength plate47, an objective lens48that collects incoming light beams to the optical media10, a light collecting lens49that collects return light from the optical media10output from the beam splitter45, a pin hole50, and a detector44(corresponding to the signal detecting unit44inFIG. 12) such as for example a known four-division detector that receives return light from the optical media10.

The recording and reproducing device has a focus servo circuit51, a tracking servo circuit52, an LD power adjusting circuit53, a spherical aberration compensating circuit54, a replay signal detection processing circuit55, which may be implemented as a demodulating unit, a memory56, an operating unit57, a display unit58and a controller40, which may also be referred to as a controlling unit.

Spherical aberration compensation values, which correspond to the cover layer thickness of the respective recording layers of the optical media10, are stored previously in the memory56. The cover layer thickness means the distance from the surface of the optical media10at the side of the objective lens48to a target recording layer. In the memory56, spherical aberration compensation values corresponding to the cover layer thickness are stored for the respective recording layers. The operating unit57has buttons and the like for carrying out various operations for recording and reproducing. On the display unit58, various information items are displayed.

The replay signal detection processing circuit55generates a focus error signal and a tracking error signal on the basis of the detection signal of return light output from the signal detecting unit (detector)44, and demodulates and replays record information and outputs the record information as a replay signal. The replay signal detection processing circuit55deciphers the spherical aberration precise compensation information, layer identification address information, light strategy information, and optimized recording and reproducing laser output information on the basis of the detection signal of the signal detecting unit44at the moment when a light beam is irradiated to the index units W1to W6of the optical media10. The focus error signal, tracking error signal, replay signal, spherical aberration precise compensation information, layer identification address information, light strategy information, and optimized recording and reproducing laser output information and so forth are input to the controller40.

The controller40uses the detection output of the pickup position detecting circuit32as feedback information to drive and control the slider servo circuit33, thereby moving and controlling the optical pickup30in the Y direction. The controller40also uses the detection output of the media position detecting circuit36as feed back information to drive and control the media move servo circuit37, and moves and controls the optical media10in the X direction, thereby controlling the relative position of the optical pickup30to the optical media10in the X-Y direction. The controller40outputs a focus error signal to the focus servo circuit51, outputs a tracking error signal to the tracking servo circuit52, and outputs to the LD power adjusting circuit53the optimized recording and reproducing laser output information and the light strategy information obtained from the index units. The controller40outputs to the spherical aberration compensating circuit54the spherical aberration compensation value memorized in the memory56and the spherical aberration precise compensation information obtained from the index units. The controller40carries out various controls concerning recording and reproducing.

The focus servo circuit51executes a focus servo that servo controls the focus actuator of the objective lens driving unit43on the basis of the focus error signal input from the controller40. The focus actuator of the objective lens driving unit43changes the position of the objective lens48in the direction perpendicular to the surface of the optical media10according to the level and polarity of the focus servo signal output from the focus servo circuit51.

In addition, when the focus servo circuit51, after completion of reading information at the index units W1to W6, moves from the index units W1to W6to the recording film forming unit14and carries recording and reproducing, the focus servo circuit51carries out a control so as for the focus servo not to come off by changing the gain of the focus servo into a high value. Thereby, it is possible to maintain the focus servo even in the recording film forming unit14whose reflectance ratio is low. Changeover instructions of the focus servo gain are input from the controller40. The focus servo circuit51and the focus actuator of the objective lens driving unit43correspond to a focus servo unit.

The tracking servo circuit52executes a tracking servo that servo controls the tracking actuator of the objective lens driving unit43on the basis of the tracking error signal input from the controller40. The tracking actuator of the objective lens driving unit43changes the radiation position of light beam on the optical media10so as to make the objective lens follow the track set in accordance to the level and polarity of the tracking servo signal output from the tracking servo circuit52.

In addition, when the tracking servo circuit52, after completion of reading information at the index units W1to W6, moves from the index units W1to W6to the recording film forming unit14and carries out recording and reproducing, the tracking servo circuit52carries out a control so as for the tracking servo not to come off by changing the gain of the tracking servo into a high value. Thereby, it is possible to maintain the tracking servo even in the recording film forming unit14whose reflectance ratio is low. Changeover instructions of the tracking servo gain are input from the controller40. The tracking servo circuit52and the tracking actuator of the objective lens driving unit43correspond to a tracking servo unit.

The LD power adjusting circuit53controls the power and light strategy of the light source41on the basis of the optimized recording and reproducing laser output information and the light strategy information input from the controller40.

The spherical aberration compensating circuit54controls the spherical aberration compensating unit42(spherical aberration compensating lens42) on the basis of the spherical aberration compensation value and the spherical aberration precise compensation information input from the controller40. The spherical aberration compensating lens42shown inFIG. 13changes the relative position to the objective lens48to change the dissipation degree or the convergence degree of an incoming beam of the light beam to the objective lens48, thereby compensating for the spherical aberration. The spherical aberration compensating lens42can be, for example, a collimator lens or an expander lens. Therefore, in this case, the spherical aberration compensating circuit54moves the spherical aberration compensating lens42in the optical axis direction, thereby compensating for the spherical aberration.

As another example of the spherical aberration compensating unit42, there is a liquid crystal element panel. As for liquid crystal molecules, when voltage is applied, the direction of liquid crystal molecules changes and the refracting index thereof changes. Accordingly, light that passes through a liquid crystal panel to a part whose area voltage has been applied becomes a transmission wave surface having a specific phase difference only in that area. This phase difference may be controlled by the size of the voltage to be applied. Accordingly, by applying voltage onto the liquid crystal element panel so that a phase difference is formed to set off the wave surface aberration that the light beam that has passed the polarized beam splitter45, it is possible to compensate for the spherical aberration.

Next, actions of the recording and reproducing device at recording and reproducing are explained hereinafter in reference toFIG. 14. The controller40first selects a recording layer to record and replay from plural recording layers of the optical media10(step S101). Then, the controller40outputs a move instruction to the media move servo circuit37and the slider servo circuit33, and relatively moves the optical media10and the optical pickup30in the X-Y directions so that the optical pickup30is positioned at the X-Y position where the index unit of the selected recording layer exists (step S102). In the optical media10, markings or notches for specifying a standard position (not shown) are arranged, and the respective index units W1to W6are arranged on the recording layers according to a prescribed rule from this standard position. Therefore, at the recording and reproducing device, if the optical pickup30is relatively moved by a specific distance in a specific direction from the standard position, it is possible to make the optical pickup30reach the index unit of the target recording layer.

Next, the controller40reads the spherical aberration compensation value corresponding to the cover layer thickness of the selected recording layer from the memory56, and outputs the read spherical aberration compensation value to the spherical aberration compensating circuit54. The spherical aberration compensating circuit54controls the spherical aberration compensating unit42of the optical pickup30according to the input spherical aberration compensation value, thereby compensating in advance for a spherical aberration that occurs before reaching the target recording layer (selected recording layer) (step S103). By this compensation, it is possible to make a servo loop of a focus servo into a servo close condition in a stable manner.

Next, procedures are performed to activate the focus servo to the index unit of the target recording layer (step S104). In the first embodiment, the reflective film forming units W1to W6of the optical media10adopt the arrangement method similar to that of the optical media of the embodiment shown inFIG. 4. Accordingly, in the case of an interlayer jump from a certain recording layer to another recording layer adjacent thereto, the focus jump method mentioned previously is adopted. In cases other than the interlayer jump to an adjacent layer, the procedures to activate the normal focus servo are carried out. The focus servo circuit51monitors the focus error signal input from the controller40, and on the basis of this monitoring, the focus servo circuit executes the procedures to activate the focus servo to the index unit of the target recording layer.

At completion of making the servo loop of the focus servo into the servo close condition to the index unit of the target recording layer, the controller40reads the information prerecorded in this index unit. In this record information, as mentioned previously, there are layer identification address information, spherical aberration precise compensation information, light strategy information, optimized recording and reproducing output information, and so forth. Then, the controller40, by use of the read record information, carries out the fine adjustment of spherical aberration compensation, adjustment of focus servo target value, adjustment of recording and reproducing laser output, setting of light strategy pattern and so forth (step S105). In addition, the controller40, by use of the read layer identification address information, may also confirm on which layer the current layer is located.

At the completion of these fine adjustment processes, the controller40moves the optical pickup30or the optical media10so that the optical pickup30should move from the status facing the index unit into the status facing the reflective film forming units14, and at this moment, the controller40changes over the focus servo gain and the tracking servo gain (step S106). Namely, the reflective film forming units14has a reflectance ratio lower than that of the index units W1to W6. Accordingly, the light receiving amount of the optical pickup30at the signal detecting unit44becomes small. As a result, the possibility increases that the focus servo and the tracking servo may come off.

Therefore, when the controller40moves from the index units to the reflective film forming units14by giving a specific command to the focus servo circuit51and the tracking servo circuit52, the controller40changes the setting of the focus servo gain of the focus servo circuit51and the tracking servo gain of the tracking servo circuit52into a value larger than the servo gain at the index units (step S106). Namely, the servo gains are changed over so that the focus servo gain and the tracking servo gain at the reflective film forming units14become larger than the respective servo gains at the index units W1to W6. By this changeover setting of the servo gains, even in the reflective film forming units14whose reflectance ratio is low, the focus servo and the tracking servo will not come off, and it is possible to maintain the focus servo and the tracking servo.

At the completion of the adjustment of servo gains, the controller40moves the optical pickup30to a required position of the reflective film forming units14, and executes recording and reproducing actions (step S107).

Next, an example of the manufacturing method of a card type optical media10is explained hereinafter in reference toFIGS. 16A to 16F. As shown inFIG. 16A, first, an intermediate layer sheet60is prepared of a band shape made of photo polymer or the like. The intermediate layer sheet60becomes an intermediate layer13of the optical media10shown inFIG. 10. By use of a stamper61having pit shapes in which the layer identification address information, spherical aberration precise compensation information, light strategy information, optimized recording and reproducing laser output information, and so forth are recorded, pit information (concave and convex) is transferred to respective units where the reflective film forming units of the intermediate layer sheet60are formed.

Next, as shown inFIG. 16B, a mask62(for example, a metallic mask) for forming a reflection forming film is laminated onto the intermediate layer sheet60. In this case, on the mask62, notches62aare formed at units where reflective film forming units are formed.

Next, as shown inFIG. 16C, by spattering, reflective film forming units63of a metal such as aluminum are deposited on the intermediate layer sheet60.

Next, as shown inFIG. 16D, a recording layer sheet64made of photo chromic materials or so is attached onto the intermediate layer sheet60where the reflective film forming units63have been deposited, and the attached recording layer sheet64is hardened by use of ultraviolet ray or the like. Thereby, the intermediate layer sheet60and the recording layer sheet64are joined with each other.

Next, as shown inFIG. 16E, a required number of the sheets65are piled in which the intermediate layer sheet60and the recording layer sheet64have been attached in the previous process. At this moment, piling is made so that the reflective film forming units63should not overlap, for example, between the respective recording layers. Of course, by use of the methods explained inFIGS. 1,4, and7, the sheets65may be piled so as to arrange the reflective film forming units63(W1to Wn) of the respective recording layers. At the completion of the piling processes, the laminated sheets65are cut into a specific size.

Next, as shown inFIG. 16F, the laminated sheets65that have been cut into the specific size are sandwiched by a substrate layer66(corresponding to the substrate layer11inFIG. 10) and a protection layer67(corresponding to the protection layer12inFIG. 10) and jointed with them. A card type optical media10is then complete.

According to the manufacturing method explained above, it is possible to manufacture card type optical media10with a fewer number of processes.

As explained heretofore, according to the card type optical media10in accordance with the first embodiment, the index units W1to W6of a high reflectance ratio are arranged on the respective recording layers L1to L6, and for the respective recording layers L1to L6, the index units W1to W6of the adjacent recording layers are arranged so that parts thereof are overlapped when viewed from the side of the optical pickup. As a result, it is possible to easily make a servo loop of a focus servo into a servo close condition, and also to use the focus jump procedures. Further, the layer identification address information, light strategy information, and optimized recording and reproducing laser output information are recorded previously into the index units W1to W6. Therefore, at the side of the recording and reproducing device, by use of these record information items, it is possible to carry out the fine adjustment of spherical aberration compensation, adjustment of focus servo target value, adjustment of recording and reproducing laser output, setting of light strategy pattern, identification of the current layer, and so forth.

Furthermore, according to the recording and reproducing device of the first embodiment, when moving from the index units to the reflective film forming units, any one of the focus servo gain and the tracking servo gain or both are changed into a value larger than the servo gain at the index units. Accordingly, even in the recording film forming units whose reflectance ratio is low, the focus servo and the tracking servo will not come off, and it is possible to maintain the focus servo and the tracking servo. Furthermore, spherical aberration compensation values corresponding to the cover layer thickness of the respective recording layers of the optical media10are stored previously in the memory56, and by use of the spherical aberration compensation values, spherical aberration compensation is carried out per recording layer. Accordingly it is possible to carry out a highly precise spherical aberration compensation, and also to perform highly precise recording and reproducing in the respective recording layers.

Moreover, according to the recording and reproducing device of the first embodiment, making a servo loop of a focus servo into a servo close condition at the respective recording layers of the optical media10is made by use of the index units W1to Wn of the respective recording layers. Accordingly, it is possible to carry out making a servo loop of a focus servo into a servo close condition to the optical media10in simple and precise manners.

When the thickness error in the respective recording layers of the optical media is very small, without using the focus servo, the objective lens actuator (objective lens driving unit)43of the optical pickup30may be fixed to the focus direction and controlled, thereby enabling recording and reproducing to be carried out. In this case, as shown inFIG. 15, a position sensor59that detects the position of the objective lens48in the optical axis direction is loaded to the objective lens driving unit43that drives the objective lens48. The procedures to make a servo loop of a focus servo into a servo close condition to the target recording layer are the same as those mentioned previously, and by use of the index units, the focus servo is activated to the target recording layer. Then, the position of the objective lens48in the optical axis direction at the moment when the focus servo has been activated to the target recording layer is memorized. When moving the optical pickup30from the index units to the recording film forming unit14and carry out recording and reproducing actions, a control is carried out so that, with the memorized position as a target value and by carrying out a feedback control with output as feedback information, the position sensor59is fixed to the memorized target position.

In the first embodiment, the optical media10is moved in the X direction, and the optical pickup30is moved in the Y direction. It is also possible in another structure that the optical media10is fixed, and the optical pickup30is movable in the X-Y directions.

Next, a second embodiment of the present invention is explained hereinafter in reference toFIGS. 17 to 20andFIG. 21A to 21F. In the second embodiment, an optical media70having a disk shape is employed.

FIG. 17is a schematic of the optical media70in the second embodiment. The optical media70is structured by laminating many recording layers L1to Ln and intermediate layers73between a substrate layer71and a protection layer72. At the internal circumferential areas of the respective recording layers L1to L6, reflective film forming units having reflection characteristics of a high reflectance ratio (referred to also as index units) W1to Wn are formed along the circumferential direction.

In this case, in the further inside of the reflective film forming units W1to Wn, a positioning unit75is formed where a marking to specify the standard position. In the respective recording layers L1to Ln, the area other than the internal circumferential areas where the reflective film forming units W1to Wn are formed includes a recording film forming unit74where recording and reproducing of information is carried out. The reflective film forming units W1to Wn have a higher reflectance ratio than that of the recording layer forming unit74. Because the reflective film forming units W1to W6are arranged in the most internal circumferential side of the optical media70, it is possible to use effectively the recording area of the recording film forming unit74of the respective recording layers L1to Ln.

In the respective index units W1to W6, in the same manner as in the first embodiment, layer identification address information, various information concerning any one of recording and reproducing or both (spherical aberration precise compensation information, light strategy information, optimized recording and reproducing laser output information) and so forth are memorized. Therefore, by use of this record information, it becomes possible to confirm the recording layers, and finely adjust and set the spherical aberration of the pickup, the focus servo target value and so forth.

FIG. 18is a schematic of the holding and driving mechanism of a disk type optical media70in the recording and reproducing device. The media holding and driving mechanism shown inFIG. 18has a supporting base76that supports the optical media70, a spindle motor77that rotates and drives the supporting base76, an encoder78that detects the rotation position of the spindle motor, and an optical pickup80that is driven in the radial direction (tracking direction) of the optical media70.

FIG. 19is a block diagram of the entire structure of the recording and reproducing device that records and replays the disk type optical media70. This recording and reproducing device has an optical pickup80, a pickup driving unit81that drives the optical pickup80in the tracking direction, a pickup position detecting circuit82that detects the position of the optical pickup80in the tracking direction and inputs the detection signal to a controller90, and a slider servo circuit83that servo controls the movement of the optical pickup80in the tracking direction according to instructions from a controller90.

In addition, the recording and reproducing device has a media position detecting circuit91that detects the rotation position of optical media70on the basis of the detection output of the encoder78and inputs the detection signal to the controller90, and a media move servo circuit92that rotates and servo drives the optical media according to instructions from the controller90.

The optical pickup80has a light source93such as a laser diode (LD), a spherical aberration compensating unit94, an objective lens driving unit95, a signal detecting unit96, and so forth. The objective lens driving unit95has a focus actuator that moves an objective lens97in the optical axis direction thereof, and a tracking actuator that moves the objective lens97in the tracking direction. The optical pickup80has an optical system, for example, one as shown in the previousFIG. 13.

The recording and reproducing device has a focus servo circuit100, a tracking servo circuit101, an LD power adjusting circuit102, a spherical aberration compensating circuit103, a replay signal detection processing circuit104, a memory105, an operating unit106, a display unit107, and a controller90.

In the same manner as in the first embodiment, spherical aberration compensation values corresponding to the cover layer thickness of the respective recording layers are stored in the memory105. The operating unit106has buttons and the like for carrying out various operations for recording and reproducing. On the display unit107, various information items are displayed.

The replay signal detection processing circuit104generates a focus error signal and a tracking error signal on the basis of the detection signal of return light output from the signal detecting unit96, and demodulates and replays record information and outputs the record information as a replay signal. The replay signal detection processing circuit104acquires the spherical aberration precise compensation information, layer identification address information, light strategy information, and optimized recording and reproducing laser output information, on the basis of the detection signal of the signal detecting unit96at the moment when a light beam is irradiated to the index units W1to Wn of the optical media70. The focus error signal, tracking error signal, replay signal, spherical aberration precise compensation information, layer identification address information, light strategy information, and optimized recording and reproducing laser output information and so forth are input to the controller90.

The controller90uses the detection output of the pickup position detecting circuit82as feedback information and drives and controls the slider servo circuit83, thereby moving and controlling the optical pickup80in the tracking direction. The controller90also uses the detection output of the media position detecting circuit91as feed back information, drives and controls the media move servo circuit92, and moves and controls the optical media70, thereby controlling the relative position of the optical pickup80to the optical media70. The controller90outputs a focus error signal to the focus servo circuit100, outputs a tracking error signal to the tracking servo circuit101, and outputs to the LD power adjusting circuit102the optimized recording and reproducing laser output information and the light strategy information obtained from the index units. Further, the controller90outputs to the spherical aberration compensating circuit103the spherical aberration compensation value memorized in the memory105and the spherical aberration precise compensation information obtained from the index units. Further, the controller90carries out various controls concerning recording and reproducing.

The focus servo circuit100executes a focus servo that servo controls the focus actuator of the objective lens driving unit95on the basis of the focus error signal input from the controller90. The focus actuator of the objective lens driving unit95changes the position of the objective lens97in the direction perpendicular to the surface of the optical media70according to the level and polarity of the focus servo signal output from the focus servo circuit100.

When the focus servo circuit100moves from the index units W1to Wn to the recording film forming unit74and carries recording and reproducing after completion of reading information at the index units W1to Wn, the focus servo circuit100carries out a control so as for the focus servo not to come off by changing the gain of the focus servo into a high value. Thereby, it is possible to maintain the focus servo even in the recording film forming unit74whose reflectance ratio is low. Changeover instructions of the focus servo gain are input from the controller90.

The tracking servo circuit101executes a tracking servo that servo controls the tracking actuator of the objective lens driving unit95on the basis of the tracking error signal input from the controller90. The tracking actuator of the objective lens driving unit95changes the radiation position of light beam on the optical media70so as to make the objective lens97follow the track concerned according to the level and polarity of the tracking servo signal output from the tracking servo circuit101.

When tracking servo circuit101moves from the index units W1to Wn to the recording film forming unit74and carries recording and reproducing after completion of reading information at the index units W1to Wn, the tracking servo circuit101carries out a control so as for the tracking servo not to come off by changing the gain of the tracking servo into a high value. Thereby, it is possible to maintain the tracking servo even in the recording film forming unit74whose reflectance ratio is low. Changeover instructions of the tracking servo gain are input from the controller90.

The LD power adjusting circuit102controls the power and light strategy of the light source93on the basis of the optimized recording and reproducing laser output information and the light strategy information input from the controller90. The spherical aberration compensating circuit103controls the spherical aberration compensating unit94on the basis of the spherical aberration compensation value and the spherical aberration precise compensation information input from the controller90.

Next, actions of the recording and reproducing device at recording and reproducing are explained hereinafter in reference toFIG. 20. The controller90first selects a recording layer to record and replay from plural recording layers of the optical media70(step S201). Then, the controller90outputs a move instruction to the slider servo circuit83, and moves the optical pickup80in the tracking direction so that the optical pickup80is positioned where the index unit of the selected recording layer exists. The controller90outputs a move instruction to the media move servo circuit92and rotates the optical media70by a required angle and then stops the optical media so that the optical pickup80is positioned where the index unit of the selected recording layer exists (step S202). When the control to rotate the optical media70by the required angle and then stop the optical media is carried out, the positioning unit75formed in the internal circumferential side of the optical media70is confirmed, and on the basis of this confirmation, the rotation angle to the required index unit is determined.

Next, the controller90reads from the memory105the spherical aberration compensation value corresponding to the cover layer thickness of the selected recording layer, and outputs the read spherical aberration compensation value to the spherical aberration compensating circuit103. The spherical aberration compensating circuit103controls the spherical aberration compensating unit94of the optical pickup80according to the input spherical aberration compensation value, thereby compensating in advance for a spherical aberration that occurs before reaching the target recording layer (step S203). By this compensation, it is possible to make a servo loop of a focus servo into a servo close condition in a stable manner.

Next, procedures are performed to activate the focus servo to the index unit of the target recording layer on the basis of the focus error signal and the like (step S204). At completion of making the servo loop of the focus servo into the servo close condition to the index unit of the target recording layer, the controller90reads the information prerecorded in this index unit. In this record information, as mentioned previously, there are layer identification address information, spherical aberration precise compensation information, light strategy information, optimized recording and reproducing laser output information, and so forth. Then, the controller90, by use of the read record information, carries out the fine adjustment of spherical aberration compensation, adjustment of focus servo target value, adjustment of recording and reproducing laser output, setting of light strategy pattern and so forth (step S205). The controller90, by use of the read layer identification address information, may also confirm on which layer the current layer is located.

At the completion of these fine adjustment processes, the controller90changes over the focus servo gain and the tracking servo gain (step S206). Namely, when the controller40moves from the index units to the reflective film forming units74, by giving a specific command to the focus servo circuit100and the tracking servo circuit101, the controller changes the setting of the focus servo gain of the focus servo circuit100and the tracking servo gain of the tracking servo circuit101into a value larger than the servo gain at the index units (step S206). By this changeover setting of the servo gains, even in the reflective film forming units74whose reflectance ratio is low, the focus servo and the tracking servo will not come off, and it is possible to maintain the focus servo and the tracking servo.

At the completion of the adjustment of servo gains, the controller90moves the optical pickup80to a required position of the reflective film forming units74, and executes recording and reproducing actions (step S207).

Next, an example of the manufacturing method of a disk type optical media70is explained hereinafter in reference toFIG. 21. As shown inFIG. 21A, first, an intermediate layer sheet120is prepared having a disk shape made of photo polymer or the like. The intermediate layer sheet120corresponds to an intermediate layer73of the optical media70shown inFIG. 17. By use of a stamper121having pit shapes in which are recorded the layer identification address information, spherical aberration precise compensation information, light strategy information, optimized recording and reproducing laser output information, and so forth, pit information (concave and convex) is transferred to the position at the internal circumferential side where the reflective film forming units of the intermediate layer sheet120are formed.

Next, as shown inFIG. 21B, a mask122(for example, a metallic mask) for forming a reflection forming film is laminated onto the intermediate layer sheet120. In this case, on the mask122, notched holes122aare formed at the position at the internal circumferential side where reflective film forming units are formed.

Next, as shown inFIG. 21C, by spattering, reflective film forming units123of a metal such as aluminum are deposited on the intermediate layer sheet120.

Next, as shown inFIG. 21D, a recording layer sheet124made of photo chromic materials or the like is attached onto the intermediate layer sheet120where the reflective film forming unit123has been deposited, and the attached recording layer sheet124is hardened by use of ultraviolet ray or the like. Thereby, the intermediate layer sheet120and the recording layer sheet124are joined with each other.

Next, as shown inFIG. 21E, a required number of the sheets125are piled in which the intermediate layer sheet120and the recording layer sheet124have been attached in the previous process. At this moment, piling is made so that the reflective film forming units123should not overlap, for example, between the respective recording layers. Of course, by use of the methods explained inFIGS. 1,4, and7, the sheets125may be piled so as to arrange the reflective film forming units123(W1to Wn) of the respective recording layers.

Next, as shown inFIG. 21F, the laminated sheets125are sandwiched by a substrate layer126(corresponding to the substrate layer71inFIG. 17) and a protection layer127(corresponding to the protection layer72inFIG. 17) and jointed with them. Thereby, a disk type optical media70is complete.

According to the manufacturing method explained above, it is possible to manufacture disk type optical media70with a fewer number of processes.

As explained heretofore, according to the disk type optical media70of the second embodiment, the index units W1to Wn of a high reflectance ratio are arranged on the respective recording layers L1to Ln. Accordingly it is possible to execute making the servo loop of the focus servo into the servo close condition in simple and easy manners. Further, as for the respective index units W1to W6, when the index units W1to Wn of the adjacent recording layers are arranged so that parts thereof are overlapped when viewed from the side of the optical pickup, it is possible to use the focus jump procedures. Furthermore, the layer identification address information, light strategy information, and optimized recording and reproducing laser output information are recorded previously into the index units W1to Wn. Therefore, at the side of the recording and reproducing device, by use of these record information items, it is possible to carry out the fine adjustment of spherical aberration compensation, adjustment of focus servo target value, adjustment of recording and reproducing laser output, setting of light strategy pattern, identification of the current layer, and so forth.

Furthermore, according to the recording and reproducing device of the second embodiment, when moving from the index units to the reflective film forming units, any one of the focus gain and the tracking servo gain or both are changed into a value larger than the servo gain at the index units. Accordingly, even in the recording film forming units whose reflectance ratio is low, the focus servo and the tracking servo will not come off, and it is possible to maintain the focus servo and the tracking servo. Still further, spherical aberration compensation values corresponding to the cover layer thickness are stored in the memory105per recording layer, and by use of the spherical aberration compensation values, spherical aberration compensation is carried out per recording layer. Accordingly it is possible to carry out a highly precise spherical aberration compensation, and also to perform highly precise recording and reproducing in the respective recording layers.

Moreover, according to the recording and reproducing device of the second embodiment, making the servo loop of the focus servo into the servo close condition at the respective recording layers of the optical media70is made by use of the index units W1to Wn of the respective recording layers. Accordingly, it is possible to carry out making a servo loop of a focus servo into a servo close condition to the optical media70in simple and precise manners.

In the recording and reproducing device according to the second embodiment, when the thickness error in the respective recording layers of the optical media70is very small, as explained previously in reference toFIG. 15, the objective lens actuator (objective lens driving unit)95of the optical pickup80is fixed to the focus direction and controlled without using the focus servo. Thereby, recording and reproducing may be carried out.