JP4249145B2 - Optical memory device and optical reproducing device - Google Patents

Description

  The present invention relates to an optical memory device having a plurality of information units corresponding to recorded information.

Conventionally, in an optical disk such as a DVD or a CD, information is recorded by forming pits (phase pits) on the disk surface.
Conventionally, a technique for recording one information unit (information unit) using a plurality of pits has been developed (Patent Document 1). 21 (0) to 21 (F) are explanatory diagrams showing this technique.

As shown in this figure, in this technique, the information unit 100 is recorded by 0 to 4 pits 101.
The pit 101 is located at the apex of a square T having a center on the recording track 102 in the information unit 100.

  In this technique, the information (recording contents) of the information unit 100 is determined by a combination (pit arrangement) of the number and position of the pits 101. Accordingly, there are 16 types of information as shown in FIGS. 21 (0) to 21 (F).

Here, reproduction of the information unit 100 shown in FIGS. 21 (0) to (F) will be described. In reproduction, the light detector 103 having eight partial light receiving surfaces D1 to D8 shown in FIG. 22 is formed by dividing the light receiving surface into eight portions of the light beam irradiated to the information unit 100 from the pits. Receive at. And a pit arrangement | sequence is discriminate | determined based on the light reception state of the partial light-receiving surfaces D1-D8, and the information will be read.
Japanese Patent Laid-Open No. 7-21568 (Release Date; January 24, 1995)

  However, in the conventional technique described above, the pit 101 is arranged at the apex of the square T in the information unit 100. Therefore, information that can be recorded in one information unit 100 is limited to 16 types.

Further, in the prior art, in order to obtain reflected light from the information unit 100, an eight-divided photodetecting element in which the light receiving surface is divided into eight is used. For this reason, a complicated signal processing circuit having a large circuit scale for processing signals from the eight partial light receiving surfaces D1 to D8 is required.
Therefore, it is difficult to reduce the cost of the playback device, and the playback speed (information transfer speed) is reduced due to an increase in signal processing time.

  The present invention has been made in view of the conventional problems as described above. An object of the present invention is to provide an optical disc (optical memory element) that can be reproduced without requiring a complicated reproduction circuit and has a high recording density.

In order to achieve the above object, the optical memory element of the present invention (the present memory element)
In the optical memory element in which a plurality of information units having information corresponding to the pit arrangement is arranged along the information track,
The pit arrangement of the information unit is characterized by a combination of a center phase pit arranged on the information track and a surrounding phase pit formed around the center phase pit.

This memory element is a recording medium of a type that records information read by light irradiation, such as an optical disk such as a DVD (Digital Versatile Disc) / CD (compact disk), an optical card, or the like.
Information is recorded on the memory element by forming information units including phase pits along the information track.

  The phase pit is a depression (or protrusion) formed on the substrate of the memory element, and has a different reflectance from the flat portion of the substrate (portion where the phase pit is not formed). .

The information unit is a unit of recording in the present memory element, and is formed from a group of phase pits.
That is, in the present memory element, information represented by an information unit is determined by a combination (pit arrangement) of the number and position of phase pits belonging to one information unit.

  In addition, information is reproduced from the memory element by specifying a pit arrangement forming the information unit based on reflected light obtained by irradiating the information unit with light.

  In particular, in the present memory element, the pit arrangement of the information unit is composed of a combination of a central phase pit arranged on the information track and a peripheral phase pit formed around the central phase pit.

Therefore, in this memory element, it is possible to remarkably increase the recording density as compared with the case where the pit arrangement is constituted only by the surrounding phase pits.
In this memory element, the phase pit is arranged at the center of the surrounding phase pit. Accordingly, the density of the phase pits can be increased, so that the recording density can be further improved.

  Further, in the present memory element, the number of divisions (the number of partial light receiving surfaces) of the light receiving surface of the reproducing photodetector necessary for reproducing information can be made equal to the number of surrounding phase pits.

That is, for example, when the pit arrangement of the information unit is composed of only six surrounding phase pits, the reflection intensity distribution from the information unit corresponds to a hexagon (if there are all phase pits, Square).
For this reason, the light detector for reproduction used for reproducing information is divided into six light receiving surfaces corresponding to six surrounding phase pits, and a six-divided light detector having six partial light receiving surfaces. It becomes.

Further, normally, the six partial light receiving surfaces are divided by three dividing lines passing through the center of the reproduction photodetector, and thus have a sector shape extending radially from the center of the reproduction photodetector. .
In the reproducing photodetector, the presence or absence of six surrounding phase pits in the information unit (which surrounding phase pits are present) is determined according to the light intensity incident on each of the six partial light receiving surfaces. The pit arrangement is obtained based on the discrimination result.

  Further, with respect to the pit arrangement of the present memory element in which the central phase pit is arranged at the center of the six peripheral phase pits, a six-segment photodetector having six partial light receiving surfaces similar to the above can be used.

  In other words, the intensity distribution of the reflected light from the central phase pit becomes an intensity distribution that depends on the distance from the center of the reproducing photodetector (the intensity of light incident on the equidistant position from the center of the reproducing photodetector is equal). Become). Accordingly, the reflected light having the same intensity is incident on each of the six partial light receiving surfaces of the reproducing photodetector from the central phase pit.

Therefore, when reproducing this memory element using a six-divided photodetector, regarding the presence or absence of the central phase pit, the total amount of light received by the entire light receiving surface (total amount of reflected light from the entire information unit (pit array); total It can be determined from the intensity of the reflected light amount.
On the other hand, as described above, the presence or absence of the surrounding phase pits can be determined by the light intensity incident on each of the six partial light receiving surfaces.

As described above, since the memory element has the central phase pit, the information unit is configured by using n (integer) phase pits, but the photodetector having the light receiving surface divided into n−1 is used. Can be used to reproduce information.
Therefore, this memory element is an optical memory element that can record information with high density and does not require a complicated reproducing circuit for reproducing information.

Further, in the present memory element, it is preferable that the peripheral phase pits are arranged at an equal distance from the central phase pit.
With this configuration, all the phase pits can be arranged efficiently (with high density) in the light spot irradiated on the information unit for reproduction. Therefore, the light spot used for reproduction can be reduced.

In the present memory element, it is also preferable to arrange the peripheral phase pits at a hexagonal apex position centered on the central phase pit.
In this configuration, 128 (2 ⁷ ) types of information (7-bit data) can be multiplexed and recorded with respect to one information unit. For this reason, it is possible to remarkably increase the recording density as compared with the case where the pit arrangement is constituted by only six surrounding phase pits.

In addition, since the phase pits are arranged at the apex angle position and the center (center of gravity) position of the hexagon, the density of the phase pits can be maximized (closest packed).
Accordingly, since a large number of information units can be formed in the memory element, the recording density of the memory element can be further improved. Furthermore, the light spot used for reproduction can be made very small.

When phase pits are arranged at seven corners of a heptagon (when seven surrounding phase pits are used), the reflection intensity distribution from the information unit corresponds to the heptagon (when there are all phase pits). To a heptagon). For this reason, it is necessary to provide a partial light receiving surface according to each phase pit, and to determine the presence or absence of each phase pit based on the incident light intensity on each partial light receiving surface.
Therefore, the number of partial light receiving surfaces (number of divisions) of the reproducing photodetector needs to be seven. For this reason, a circuit for processing the intensity of incident light on each partial light receiving surface becomes complicated, resulting in an increase in cost.
In addition, since there are seven partial light receiving surfaces of the photodetector, the angle difference between adjacent light receiving surfaces is reduced, and the accuracy of determining the position of the phase pit is reduced, resulting in an increase in reproduction errors. .

In the present memory element, it is also preferable to arrange the peripheral phase pits at a rectangular apex position centered on the central phase pit.
In this configuration, the information unit is composed of a combination of five phase pits, that is, one central phase pit arranged on the information track and four surrounding phase pits positioned around the center phase pit.

In this configuration, 32 (2 ⁵ ) types of information (5-bit data) can be multiplexed and recorded with respect to one information unit. For this reason, it is possible to remarkably increase the recording density as compared with the case where the pit arrangement is constituted by only four surrounding phase pits.

In addition, when phase pits are arranged at five apex angles of a pentagon in order to multiplexly record 5-bit data, the reflection intensity distribution from the information unit corresponds to the pentagon (when there are all phase pits). And a pentagon). For this reason, it is necessary to provide a partial light receiving surface according to each phase pit, and to determine the presence or absence of each phase pit based on the incident light intensity on each partial light receiving surface.
Therefore, the number of partial light receiving surfaces (number of divisions) of the reproducing photodetector needs to be five. For this reason, a circuit for processing the intensity of incident light on each partial light receiving surface becomes complicated, resulting in an increase in cost.
In addition, since the number of the partial light receiving surfaces of the photodetector is five, the angle difference between the adjacent light receiving surfaces is reduced, and the accuracy of determining the position of the phase pit is reduced, resulting in an increase in reproduction errors. .

In the configuration in which the surrounding phase pits are arranged at the apex positions of the hexagon or the quadrangle, it is preferable that one of the diagonals passing through the center of the hexagon or the quadrangle overlaps the information track.
This makes it easy to set the pit arrangement to be line symmetrical about the information track.

That is, in the present memory element, it is preferable to use only the pit arrangement of the information unit that is axisymmetric about the information track.
Normally, in reproducing the memory element, light (reproducing light) irradiated on the memory element is scanned (tracked) on an information track. Such tracking is controlled by a push-pull method or the like based on the reflected light from the information unit.

  At this time, if the pit arrangement is asymmetric in the radial direction, the intensity of the reflected light from both sides of the information track becomes asymmetric, so that the push-pull signal is disturbed and accurate tracking control cannot be performed (tracking becomes unstable). )there is a possibility. If the tracking becomes unstable, it becomes impossible to measure the accurate total amount of reflected light from each information unit, and the pit arrangement cannot be accurately identified.

  On the other hand, when only the pit arrangement having line symmetry about the information track is used, it is possible to reliably prevent the push-pull signal disturbance as described above. Thereby, stable tracking can be realized.

  Further, in the configuration in which the surrounding phase pits are arranged at the vertex positions of the hexagon, it is preferable to use only those having an odd number of surrounding phase pits or only those having an even number of surrounding phase pits as the pit arrangement. .

Usually, in the reproduction of an optical memory element, when identifying the pit arrangement, the total reflected light quantity (total reflected light quantity) from the entire information unit (pit arrangement) is often an important clue. Further, the total amount of reflected light basically changes depending on the number of phase pits.
In addition, when phase pits are arranged at the apex position and the center position of the hexagon, there are nine types of total reflected light amounts.

On the other hand, when only those having an odd number (or even number) of surrounding phase pits are used as the phase pits, the total reflected light amount can be set to four types (or five types). Further, the difference in total reflected light amount (step width) can be increased.
Accordingly, the total reflected light amount can be easily and accurately specified during reproduction. Therefore, the configuration of the device for measuring the total reflected light amount can be simplified.

Further, in the configuration in which the peripheral phase pits are arranged at the apex position of the hexagon, it is preferable to use a pit arrangement of the information unit that is axisymmetric with respect to one of the diagonal lines passing through the center of the hexagon. .
With this configuration, accurate identification can be performed even when the intensity of light used for reproduction varies slightly. Reproduction costs can be reduced.
In this regard, please refer to [Best Mode for Carrying Out the Invention] to be described later.

In addition, when reproducing a memory element having an information unit composed of a plurality of pits, such as the present memory element, “timing at which the center of the light beam irradiated to the information unit is substantially coincident with the center of the information unit to be reproduced” Therefore, it is preferable to read the information unit.
Therefore, at the time of reproduction, it is preferable that the accuracy of the synchronization signal for controlling the reading timing of the information unit is as high as possible.
Therefore, it can be said that it is preferable to provide a plurality of synchronization units having the same shape on the information track of the memory element at equal intervals.

In the absence of such a synchronization unit, a synchronization signal synchronized with the light reception signal obtained from the information unit is generated (self-clock method).
However, in this case, since the pit arrangement differs for each information unit, a phase shift occurs in the light reception signal from each information unit. For this reason, an error occurs in the synchronization signal generated based on this light reception signal. Therefore, when reproduction is performed using such a synchronization signal, it is difficult to accurately measure the total amount of reflected light from the information unit, and the pit arrangement of the information unit cannot be accurately identified.

  On the other hand, when the synchronization unit as described above is provided, a synchronization signal for reproducing the information unit can be generated using the reflected light from the synchronization unit. Therefore, since a highly accurate synchronization signal can be generated, the information unit can be accurately identified, and the information can be reproduced accurately.

In addition, the synchronization unit in the present memory element is preferably formed with a pattern larger than the phase pit constituting the information unit.
As a result, the intensity change amount of the reflected light by the synchronization unit can be increased, so that the synchronization signal can be easily generated.

  In addition, as for the synchronization unit in the present memory element, one pattern having a large size may be used, or it may be constituted by a set of a plurality of patterns having a small size.

  When the synchronization unit is composed of a plurality of patterns, it is preferable to use phase pits similar to the information unit as the pattern. In this configuration, the phase pit (pattern) constituting the information unit and the pattern constituting the synchronization unit have the same size, so that there is an advantage that the synchronization unit can be easily formed.

When the phase pit of the information unit is used as the pattern of the synchronization unit, it is preferable that the pattern of the synchronization unit is composed of all the surrounding phase pits and the central phase pit.
As a result, the intensity change amount of the reflected light by the synchronization unit can be increased, so that the synchronization signal can be easily generated.

  The synchronization units are preferably formed at the same pitch as the “information unit formation pitch (information unit pitch) in the information track extending direction (information track direction)”. In this case, when the synchronization signal is generated using the light reception signal from the synchronization unit, the cycle of the synchronization signal can be the same as that of the light reception signal. Therefore, the circuit for generating the synchronization signal can be simplified. Therefore, the cost for reproducing the memory element can be reduced.

Further, the synchronization unit may be formed with a pitch twice as large as the information unit pitch described above.
Thereby, the intensity | strength change amount of the reflected light by a synchronous unit can be enlarged more. Therefore, it is possible to easily generate the synchronization signal using the light reception signal obtained by receiving the reflected light. Further, the information unit and the synchronization unit can be easily discriminated due to the difference in the period of the light reception signal. Therefore, information can be reproduced more reliably.
In this case, a synchronization signal having a half period of the light reception signal from the synchronization unit is generated and used for reproducing the information unit.

In addition, as described above, the memory element can be formed as an optical disk or an optical card.
Here, the optical disk is one in which information tracks are formed in a spiral shape (vortex) or concentric circles. An optical card has a linear information track.

Further, an optical reproducing apparatus (this reproducing apparatus) of the present invention is an optical reproducing apparatus that irradiates information units of the memory element with light and reproduces information based on the reflected light.
A reproducing photodetector that receives reflected light from the information unit and outputs a received light signal corresponding to the amount of received light;
A pit arrangement specifying circuit for specifying the pit arrangement of the information unit for reproduction based on the light reception signal output from the reproduction photodetector.

The reproducing apparatus is an apparatus for reproducing the memory element, and irradiates the information unit of the memory element with light, and performs reproduction by specifying the pit arrangement of the information unit based on the reflected light. It is.
That is, in this reproducing apparatus, the reproducing photodetector receives the reflected light from the information unit and outputs a light reception signal corresponding to the amount of light received. Based on this light reception signal, the pit arrangement specifying circuit is designed to specify the pit arrangement of the information unit (information unit irradiated with light) related to reproduction.

In addition, the reproducing apparatus may be provided with a control photodetector separate from the above-described reproducing photodetector. This control photodetector receives reflected light from the information unit and outputs a received light signal corresponding to the amount of received light to the light control circuit.
Here, the light control circuit is for performing control of the light irradiated to the optical memory element (control of the light irradiation position and the focal position) based on the light reception signal output from the control photodetector. .

  Normally, the reflected light applied to the control light detector is focused by the cylindrical lens, so that the wave front is disturbed. Therefore, when the control photodetector and the reproduction photodetector are combined with one photodetector, the reproduction photodetector is also irradiated with reflected light with a disturbed wavefront. For this reason, the light intensity distribution on the light receiving surface is disturbed, and it becomes difficult to accurately specify the pit arrangement of the information unit.

  Therefore, in the above configuration, by providing the control light detector separately from the reproduction light detector, it is possible to avoid irradiating the reproduction light detector with reflected light with a disturbed wavefront. ing. This makes it possible to achieve both accurate light control and information reproduction.

Further, when reproducing the present memory element having a configuration in which the surrounding phase pits are arranged at the apex angle position of the hexagon, as described above, the six-divided photodetector is used as the reproducing photodetector in the reproducing apparatus. Is possible.
Here, the six-divided photodetector has six partial light receiving surfaces formed by dividing the light receiving surface into six parts by three dividing lines.

In such a six-divided photodetector, each partial light receiving surface outputs a light reception signal corresponding to its own light reception amount to the pit arrangement specifying circuit.
Based on these six light reception signals, the pit arrangement specifying circuit is designed to specify the pit arrangement of the information unit related to reproduction.

  In the six-divided photodetector as described above, it is preferable that the three dividing lines that divide the light receiving surface of the reproducing photodetector are shifted from each other by 60 degrees. As a result, the sizes of the partial light receiving surfaces can be made equal, so that the light reception signal processing in the pit arrangement specifying circuit can be easily performed.

The dividing lines of the reproducing photodetector are shifted from each other by 60 degrees, and one of these dividing lines is orthogonal to a straight line on the light receiving surface corresponding to one diagonal line of the hexagon. It is preferable.
In this case, the center of the partial light receiving surface can be arranged at a position corresponding to the surrounding phase pit of the present reproducing apparatus (a position where the reflected light from each surrounding phase pit becomes maximum). Accordingly, each of the six partial light receiving surfaces can have a one-to-one correspondence with the surrounding phase pits. For this reason, the presence or absence of six kinds of surrounding phase pits can be clearly determined by the six partial light receiving surfaces.

Further, when reproducing the present memory element having a configuration in which the peripheral phase pits are arranged at the rectangular apex positions, a quadrant photodetector can be used as the reproducing photodetector in the reproducing apparatus.
Here, the four-divided photodetector has four partial light-receiving surfaces formed by dividing the light-receiving surface into four by two dividing lines.

In such a four-divided photodetector, each partial light receiving surface outputs a received light signal corresponding to its own received light amount to the pit arrangement specifying circuit.
Based on these four received light signals, the pit arrangement specifying circuit is designed to specify the pit arrangement of the information unit related to reproduction.

  In the four-divided photodetector as described above, it is preferable that the two dividing lines that divide the light receiving surface of the reproducing photodetector are orthogonal to each other. As a result, the sizes of the partial light receiving surfaces can be made equal, so that the light reception signal processing in the pit arrangement specifying circuit can be easily performed.

The dividing lines of the reproducing photodetector are preferably orthogonal to each other and crossed at an angle of 45 ° with respect to a straight line corresponding to one diagonal line of the square on the light receiving surface.
In this case, the center of the partial light receiving surface can be arranged at a position corresponding to the surrounding phase pit of the present reproducing apparatus (a position where the reflected light from each surrounding phase pit becomes maximum). Therefore, the surrounding phase pits can be made to correspond one to one to each of the four partial light receiving surfaces. For this reason, the presence or absence of four types of surrounding phase pits can be clearly determined by the four partial light receiving surfaces.

Further, the pit arrangement specifying circuit of the reproducing apparatus can be constituted by a total light quantity comparison circuit and a partial light quantity comparison circuit.
Here, the total light amount comparison circuit specifies the total reflected light amount that is the total amount of light reflected by the information unit based on the light reception signals output from all the partial light receiving surfaces in the reproducing photodetector. .

Here, the amount of reflected light is smaller when phase pits are present than when they are not present. Therefore, the more phase pits make up the information unit, the smaller the amount of reflected light.
In addition, when laser light is used as the light irradiated to the memory element, the amount of reflected light tends to be smaller when one central phase pit is present than when there is one surrounding phase pit.
Therefore, the pit arrangement of the information unit can be roughly determined by specifying the total reflected light amount by the total light amount comparison circuit.

The partial light quantity comparison circuit compares (partial comparison) the magnitudes of light incident on the partial light receiving surfaces using light reception signals output from the partial light receiving surfaces.
The partial light quantity comparison circuit is designed to determine the content of the partial comparison (the type and number of partial comparisons) based on the determination result by the total light quantity comparison circuit.

  The partial light quantity comparison circuit determines the presence or absence of the surrounding phase pit and the center phase pit based on the comparison result, and specifies the pit arrangement of the information unit.

As described above, in this configuration, the pit arrangement is roughly determined by the total light amount comparison circuit before performing the partial comparison by the partial light amount comparison circuit.
Therefore, it is possible to reduce the type and number of partial comparisons necessary for specifying the pit arrangement by the partial light quantity comparison circuit.

In addition, when reproducing the memory element having the above-described synchronization unit, it is preferable that the reproduction apparatus includes a synchronization signal generation circuit.
The synchronization signal generation circuit generates a synchronization signal to be output to the pit arrangement specifying circuit based on the light reception signal from the synchronization unit.
In this case, it is preferable that the pit arrangement specifying circuit is designed to specify the pit arrangement of the information unit related to reproduction using this synchronization signal.

  Thereby, since the synchronization signal based on the synchronization unit can be generated, the pit arrangement of the information unit can be accurately determined. Therefore, it is possible to accurately reproduce information.

In addition, when the synchronization unit of the optical memory element is formed at the same pitch as the information unit pitch, the synchronization signal generation circuit may be designed to generate a synchronization signal having the same period as the light reception signal from the synchronization unit. preferable.
In this configuration, since the configuration of the synchronization signal generation circuit can be simplified, it is possible to suppress an increase in the cost of the reproducing apparatus by including the synchronization signal generation circuit.

  Further, when the synchronization unit of the optical memory element is formed with a pitch twice the information unit pitch, the synchronization signal generation circuit generates a synchronization signal having “a half period of the light reception signal from the synchronization unit”. It is preferable that it is designed.

  In this configuration, the amount of change in the intensity of reflected light by the synchronization unit can be further increased. Therefore, the synchronization signal generation circuit can easily generate the synchronization signal. Further, the information unit and the synchronization unit can be easily discriminated due to the difference in the period of the light reception signal. Therefore, more reliable information reproduction is possible.

As described above, the optical memory element of the present invention (the present memory element) is an optical memory element in which a plurality of information units having information corresponding to the pit arrangement is arranged along the information track. This is a configuration comprising a combination of a central phase pit arranged on the track and a peripheral phase pit formed around the central phase pit.

  In this memory element, the pit arrangement of the information unit is composed of a combination of a central phase pit arranged on the information track and a peripheral phase pit formed around the central phase pit.

Therefore, in this memory element, it is possible to remarkably increase the recording density as compared with the case where the pit arrangement is constituted only by the surrounding phase pits.
In this memory element, the phase pit is arranged at the center of the surrounding phase pit. Accordingly, the density of the phase pits can be increased, so that the recording density can be further improved. In this memory device, a plurality of synchronization units having the same shape are provided on the information track at equal intervals. Therefore, since a highly accurate synchronization signal can be generated, the information unit can be accurately identified, and the information can be reproduced accurately.

Further, in the present memory element, the number of divisions (the number of partial light receiving surfaces) of the light receiving surface of the reproducing photodetector necessary for reproducing information can be made equal to the number of surrounding phase pits.
That is, since this memory element has a central phase pit, an information unit is configured using n (integer) phase pits, but a photodetector having a light receiving surface divided into n-1 is used. Information can be reproduced.
Therefore, this memory element is an optical memory element that can record information with high density and does not require a complicated reproducing circuit for reproducing information.

An embodiment of the present invention will be described.
An optical disc apparatus (this disc apparatus; optical reproduction apparatus) according to the present embodiment is a reproduction apparatus for reproducing information recorded on an optical disk.

FIG. 2 is an explanatory diagram showing the configuration of the present disk device.
As shown in this figure, the disk device includes a spindle 10, an optical pickup 11, and a circuit board 12.

The spindle 10 rotates with the optical disk 1 to be reproduced fixed.
The configuration of the optical disc 1 will be described in detail later.

The optical pickup 11 irradiates a rotating optical disc 1 with laser light (light beam) L while moving in the radial direction. In the present disk device, information on the optical disk 1 is reproduced by the irradiation of the laser beam L.
The circuit board 12 is a board having a plurality of circuit groups for driving the spindle 10 and the optical pickup 11.

  As shown in FIG. 2, the optical pickup 11 includes a semiconductor laser light source 21, a collimator lens 22, a beam splitter 23, a condenser lens 24, an actuator 25, a beam splitter 26, a condenser lens 27, a cylindrical lens 28, and control light detection. A light-emitting device 29, a condenser lens 30, and a light detector (reproducing light detector) 31.

The semiconductor laser light source 21 is a light source that generates laser light L.
The collimator lens 22 collimates the light beam of the laser light L emitted from the semiconductor laser light source 21.
The beam splitter 23 transmits the laser light L that has passed through the collimator lens 22, while reflecting the laser light L incident from the optical disc 1 side (condenser lens 24 side), and bends its path at a right angle.

The condensing lens 24 condenses the laser light L transmitted through the beam splitter 23 and condenses and irradiates the recording surface of the optical disc 1. The condensing lens 24 also has a function of condensing the reflected laser light La reflected by the optical disc 1.
The actuator 25 adjusts the position of the condenser lens 24 (drives the condenser lens 24) in order to perform focusing adjustment and tracking adjustment.

The reflected laser beam La is returned by the optical disk 1 along the optical path upon incidence, reflected by the beam splitter 23, and guided to the beam splitter 26.
The beam splitter 26 transmits a part of the reflected laser light La and reflects a part thereof to the condenser lens 30 side.

The condensing lens 27 and the cylindrical lens 28 condense the reflected laser light La transmitted through the beam splitter 26 onto the control light detector 29.
The control light detector 29 outputs a light receiving signal for focusing and tracking control based on the reflected laser light La.

The condensing lens 30 condenses the reflected laser light La reflected by the beam splitter 26 on the photodetector 31.
The photodetector 31 receives the reflected laser light La and generates an electrical signal (light reception signal).
The configuration of the photodetector 31 will be described later.

  As shown in FIG. 2, the circuit board 12 includes a spindle control circuit 41, a laser control circuit 42, a total light quantity comparison circuit 43, a partial light quantity comparison circuit 44, a demodulation circuit 45, an error correction circuit 46, and a focusing / tracking circuit 47. It has.

The spindle control circuit 41 rotates the optical disk 1 fixed to the spindle 10 together with the spindle 10.
The laser control circuit 42 controls (drives) the semiconductor laser light source 21 to irradiate the laser beam L.

  The focusing / tracking circuit 47 generates a focusing signal by the astigmatism method and a tracking signal by the push-pull method based on the received light signal generated by the control photodetector 29. The actuator 25 is driven based on the focusing signal and the tracking signal to perform focusing and tracking.

The circuits 43 to 46 are a circuit group that generates a reproduction signal based on the light reception signal output from the photodetector 31.
The circuits 43 to 46 will be described later in detail.

  In addition, the disk device is provided with a control unit (not shown) for controlling all the operations of the disk device by controlling the circuit of the circuit board 12.

Here, the configuration of the optical disc 1 will be described.
FIG. 3 is a plan view showing the configuration of the optical disk (optical memory element) 1. The optical disc 1 has a disk shape with a diameter of 120 mm, and has an information track 2 for recording information on its recording surface (surface) in a spiral shape as shown in FIG. is there.

FIG. 4 is a cross-sectional view of the optical disc 1.
As shown in this figure, the optical disc 1 has a configuration in which a transparent substrate 7, a metal reflective film 8, and a protective film 9 are laminated in this order.

The transparent substrate 7 is made of a transparent material such as polycarbonate resin.
The metal reflection film 8 is a metal film that covers the surface of the transparent substrate 7, and as the material thereof, for example, aluminum can be used.
The protective film 9 is a protective film that covers the metal reflective film 8.

  Further, convex phase pits 3 and 4 are formed at the interface of the transparent substrate 7 with the metal reflection film 8. These phase pits 3 and 4 form an information unit 5 which is an information recording unit (recording information unit), and are formed along the information track 2 described above.

  FIG. 5 is an explanatory diagram showing the information track 2 in detail. As shown in this figure, the information track 2 has a configuration in which a plurality of information units 5 as information recording units are arranged along the direction in which the information track 5 extends.

  The information unit 5 is an information unit composed of a maximum of six phase pits 3 and a maximum of one phase pit 4, and is regularly (equally spaced) arranged on the information track 2.

The phase pit 3 is a phase pit arranged at the apex position of a regular hexagon whose center overlaps the information track 2 (each phase pit 3 is at an equidistant position from the center of the regular hexagon). In addition, this regular hexagon is designed so that one of the diagonal lines that bisect itself overlaps the information track 2.
The phase pit 4 is a phase pit arranged at the center position of the regular hexagon .

  The optical disc 1 is designed to determine information (recording contents) of the information unit 5 by a combination of the number and position of the phase pits 3 and 4 (phase pit arrangement state; pit arrangement).

FIG. 1 and FIG. 6 are explanatory diagrams showing types of pit arrangement (information types) of the information unit 5. As shown in this figure, in the optical disc 1, the information unit 5 is designed to have 128 pit arrangements 1a3 to 128i3.
That is, the information unit 5 is designed to have 128 kinds of information corresponding to the pit arrangements 1a3 to 128i3.

Here, the pit arrangement | sequence 1a3 is a state without a phase pit.
The pit arrays 2b1 to 8c3 are arrayed states having one phase pit.
Furthermore, the pit arrays 9c0 to 29d1 are an array state composed of two phase pits.

The pit arrangements 30d1 to 64e3 are arrangements formed by three phase pits.
Also, the pit arrangements 65e0 to 99f3 are arrangements composed of four phase pits.
Further, the pit arrays 100f1 to 120g3 are formed of five phase pits.

The pit arrangements 121g3 to 127h0 are arranged with six phase pits.
Finally, the pit array 128i3 is an array state composed of seven phase pits.

In addition, the code | symbol of pit arrangement | sequence 1a3-128i3 combines "the serial number, the light quantity identifier, and the symmetry identifier" of each pit arrangement | sequence.
That is, the serial number is a number (1 to 128 ) assigned to each of all 128 types of pit arrangements.

  The light quantity identifier corresponds to the total light quantity (total reflected light quantity) of the reflected laser light La that enters the photodetector 31 described later from the information unit 5 having the pit arrangement.

That is, in the reproduction of the optical disc 1 in this disc apparatus, the control unit controls the spindle control circuit 41 to rotate the optical disc 1. Further, the control unit controls the laser control circuit 42 to irradiate the optical disk 1 with the laser light L from the condenser lens 24, and as shown in FIG. 5, the beam spot 6 is generated along the information track 2 of the optical disk 1. Scan. At this time, the laser beam L is irradiated so that the center position of the beam spot 6 overlaps the center position of the information unit 5.
As a result, the laser beam L is reflected by the information unit 5 on the information track 2, and a reflected laser beam La is generated.

Further, the amount of the reflected laser beam La changes according to the pit arrangement of the information unit 5.
That is, the light quantity identifier is a value indicating the light quantity of the reflected laser light La corresponding to the pit arrangement in each information unit 5. In the optical disc 1, the total reflected light amount of each pit arrangement is classified by nine types of light amount identifiers a to i.
In the pit arrangement having the same light quantity identifiers a to i, the total reflected light quantity is almost equal. Further, the total amount of reflected light decreases in the order of a to i.

Here, the relationship between the number and position of the phase pits 3 and 4 and the total amount of reflected light will be described.
When the phase pits 3 and 4 are present, the amount of reflected light is smaller than when these are not present.
In addition, the intensity distribution of the beam spot 6 in the laser light L is a Gaussian distribution. Therefore, the light intensity at the center of the beam spot 6 is stronger than that of the surrounding area. Further, as described above, the laser beam L is irradiated so that the center position of the beam spot 6 overlaps the center position of the information unit 5.

  For this reason, the amount of reflected light tends to be smaller when the phase pit 4 is present at the center position than when the phase pit 3 is present at the apex angle position.

In each of the pit arrays 2b1 to 7b1, there is one phase pit 3 corresponding to the outer peripheral position of the beam spot 6, and the total reflected light amount is equal.
Further, in the pit array 8c3, there is one phase pit 4 corresponding to the center position of the beam spot 6, so that the total reflected light amount is smaller than that of the pit arrays 2b1 to 7b1.

Next, in 9c0 to 23c3 having two phase pits 3, the total reflected light amount becomes equal to the pit arrangement 8c3 due to the increase in the number of phase pits.
In addition, since the pit arrangements 24d1 to 29d1 have one phase pit 4 and one phase pit 3, the total amount of reflected light is smaller than that of the pit arrangements 9c0 to 23c3. Thereafter, in the same manner, the total amount of reflected light decreases as the number of phase pits increases.

The symmetry identifiers 0, 1, 3 of the pit arrangement are determined as follows.
That is, the hexagon in which the phase pit 3 is formed has six sides. These sides have opposite sides (a set of two sides facing each other is taken as an opposite side set).
The symmetry identifier represents the number of opposite side groups (symmetric opposite side groups) such that “the number of phase pits 3 belonging to each side is equal”.

For example, the pit arrangement 31d1 shown in FIG. 1 has phase pits 3 at three positions P2 to P4 among the apex angles P1 to P6 shown in FIG.
Therefore, the phase pit 3 belongs to one side H1, two sides H2 and H3, and one side H4. There is no phase pit 3 belonging to the sides H5 and H6.
In this case, of the three opposite side pairs H1, H4, H2, H5, H3, and H6, only H1 · H4 is the symmetrical opposite side set. Therefore, the symmetry identifier of this pit arrangement is 1.

Next, the configuration of the photodetector 31 will be described.
FIG. 8 is an explanatory diagram showing the configuration of the photodetector 31. As shown in this figure, the photodetector 31 includes six partial light receiving surfaces (photodetecting elements) D1 to D6 that are obtained by dividing the light receiving surface into six parts.

The partial light receiving surfaces D1 to D6 are formed by dividing the circular light receiving surface of the photodetector 31 by three dividing lines A to C, and are radially formed from the center of the light receiving surface of the photodetector 31. It has an extending fan shape.
Here, the dividing lines A to C pass through the center of the light receiving surface and are arranged in a state shifted by 60 degrees so as to divide the light receiving surface into six equal parts. Therefore, the partial light receiving surfaces D1 to D6 are designed to have the same area and shape.

The partial light receiving surfaces D1 to D6 respectively output voltage signals (light receiving signals) R1 to R6 having voltage values corresponding to the amount of reflected light received by the partial light receiving surfaces D1 to D6.
In the photodetector 31, one of the dividing lines A to C (A in FIG. 8) dividing the partial light receiving surfaces D1 to D6 is a straight line corresponding to the information track 2 of the optical disc 1 (the photodetector 31). Are arranged so as to be orthogonal to the line XX ′ corresponding to the information track.
Further, the other two dividing lines (B · C in FIG. 8) are arranged so as to form an angle of 30 degrees with the straight line XX ′.

Here, the relationship between the phase pits 3 and 4 and the partial light receiving surfaces D1 to D6 will be described.
Reflected light from the individual phase pits becomes diffracted light and enters the entire surface of the partial light receiving surfaces D1 to D6. When there are a plurality of phase pits, the diffracted light from each phase pit interferes and enters the partial light receiving surfaces D1 to D6. That is, the reflected light from each phase pit is incident on all but not one of the partial light receiving surfaces D1 to D6.

However, the reflected light from one phase pit 3 has a relatively high intensity incident on any of the partial light receiving surfaces D1 to D6 at a position corresponding to the phase pit 3 (far from the phase pit 3). The intensity of light incident on the element at the position is relatively small).
For example, in the pit arrangement 2b1, the intensity of light incident on the partial light receiving surface D3 is relatively large, and the intensity of light incident on the partial light receiving surface D6 is relatively small.

Further, the reflected light from the phase pit 4 located at the center of the hexagon is uniformly incident near the center of all the partial light receiving surfaces D1 to D6.
Therefore, in the pit array 8c3 having only one phase pit 4, the intensity of light incident near the center of all the partial light receiving surfaces D1 to D6 is relatively large, and the intensity of light incident on the peripheral area is relatively large. Becomes smaller.

Next, the circuits 43 to 46 of the circuit board 12 shown in FIG. 2 will be described.
These circuits 43 to 46 are a circuit group that identifies the pit arrangement of the information unit 5 related to reproduction based on the light reception signal output from the photodetector 31 and generates a reproduction signal according to the identification result.

  The total light amount comparison circuit 43 adds the light reception signals R1 to R6 output from all the partial light receiving surfaces D1 to D6 of the photodetector 31 to obtain the total reflected light amount. And from the value, it has the function to derive | lead-out the light quantity identifier ai in the pit arrangement | sequence of the information unit 5 concerning reproduction | regeneration.

  In the pit arrangements 1a3 and 128i3, there is no other pit arrangement having the same total reflected light amount. For this reason, when the information unit 5 related to reproduction has the above pit arrangement, the identification of the pit arrangement is completed only by the total light quantity comparison circuit 43.

The partial light quantity comparison circuit 44 identifies the pit arrangement of the information unit 5 related to reproduction based on the light quantity identifiers a to i derived by the total light quantity comparison circuit 43.
Tables 1 to 3 show the identification conditions by the partial light quantity comparison circuit 44.

X1 to X6, Y1 to Y6, and Z1 to Z3 shown in these tables are results obtained by adding the received light signals R1 to R6 from the partial light receiving surfaces D1 to D6, respectively.
Table 4 shows the relationship between the light reception signals R1 to R6 and each addition result.

  As shown in this table, the partial light quantity comparison circuit 44 calculates the magnitude relationship of the addition results obtained by adding a plurality of light reception signals R1 to R6 according to the light quantity identifiers a to i. And it is designed to identify the pit arrangement of the information unit 5 based on the calculation result.

That is, first, the partial light quantity comparison circuit 44 compares Y1 and Y4 under the discrimination condition I.
As a result of this comparison, the partial light quantity comparison circuit 44 has a line symmetry with respect to the information track 2 in the pit arrangement of the information unit 5 (radial line symmetry; whether or not the information track 2 is line symmetric). ).

Next, the partial light quantity comparison circuit 44 compares X2 and X5 under the identification condition II.
As a result of this comparison, the partial light quantity comparison circuit 44 has a line symmetry in the circumferential direction in the pit arrangement of the information unit 5 (line symmetry about a straight line passing through the center of the information unit 5 and perpendicular to the information track 2). ).
At this stage, identification is completed for the pit arrangement having the light quantity identifier b · h corresponding to the total reflected light quantity.

Next, the partial light quantity comparison circuit 44 checks the magnitude relationship between Z1 to Z3 in the identification condition III. The relationship to be examined is determined based on the type of the light quantity identifier and the result of the identification conditions I and II.
For example, when the light quantity identifier of the pit arrangement is c · g, the partial light quantity comparison circuit 44 compares Z1 and Z2. Thereby, for the pit arrangement having the light quantity identifier c · g, the identification of the pit arrangement is completed when Z1 <Z2, Z1> Z2.
On the other hand, when Z1 = Z2, the pit arrangement is any one of 23c3, 8c3, 118g3, and 121g3. In this case, the partial light quantity comparison circuit 44 identifies the magnitude relationship between Z2 and Z3 as the identification condition IV. Thereby, the identification in all the pit arrangements having the light quantity identifier c · g is completed.

For the pit arrangement having the light quantity identifiers d, e, and f, the partial light quantity comparison circuit 44 determines the magnitude relationship between Z1 and Z2, Z2 and Z3, and Z1 and Z3 based on the result of the identification conditions I and II. Investigate.
For example, regarding the pit arrangement of the light quantity identifier d, when Y1> Y4 and X2> X5, Z1 and Z3 are compared.

Thereafter, as shown in Tables 1 to 3, the partial light quantity comparison circuit 44 performs the comparison shown in the identification conditions IV and V. For example, when the light quantity identifiers d, Y1> Y4, X2> X5, Z1 = Z3. The partial light quantity comparison circuit 44 identifies the pit arrangement based on “whether or not the difference between X1 and X4 is greater than the reference value S1” (identification condition IV).
The reason for using such a reference value S1 is that 25d1 and 30d1 cannot be distinguished only from the symmetry of the phase pit.
Here, the reference value (reference signal) S1 is a fixed value preset in advance in the present disk device.

  As described above, the partial light quantity comparison circuit 44 can identify all 128 types of pit arrangements by comparing the intensities of the light reception signals R1 to R6 based on the light quantity identifier.

The demodulation circuit 45 generates a demodulated signal (demodulated data) based on the identification result of the pit arrangement by the partial light quantity comparison circuit 44.
Tables 1 to 3 show demodulated signals corresponding to each pit arrangement.
As shown in FIG. 1, in this disc apparatus, there are 128 types of pit arrangements of the information unit 5. Accordingly, 128 types of information can be multiplexed and recorded using one information unit 5, and therefore, a 7-bit demodulated signal can be obtained from one information unit.

The error correction circuit 46 performs error correction on the demodulated signal generated by the demodulation circuit 45 to generate a reproduction signal.
In this disc apparatus, the reproduction signal is converted into a video signal (video information) or an audio signal (audio information) by a conversion circuit (not shown). These signals are displayed on a display device (not shown) such as a display screen or a speaker.

As described above, in the optical disc 1, the pit arrangement of the information unit 5 includes seven phase pits, that is, one phase pit 4 arranged on the information track and six phase pits 3 positioned around the phase pit 4. It consists of a combination.
Here, the phase pit 3 is a phase pit arranged at the apex position of the hexagon where one diagonal passing through the center overlaps the information track 2.
The phase pit 4 is a phase pit arranged at the center position of the hexagon.

  As described above, the optical disc 1 is designed so that the pit arrangement of the information unit 5 is formed by the six phase pits 3 and the one phase pit 4 at the center.

Therefore, the optical disk 1 can multiplex-record 128 (2 ⁷ ) types of information (7-bit data) with respect to one information unit 5. For this reason, it is possible to remarkably increase the recording density as compared with the case where the pit arrangement is constituted by only six phase pits 3.

Further, in the optical disc 1, since the phase pits 3 and 4 are arranged at the apex angle position and the center (center of gravity) position of the hexagon, the density of the phase pits can be maximized (closest packing is possible). Yes.
Accordingly, since a large number of information units 5 can be formed on the optical disc 1, the recording density of the optical disc 1 can be further improved. Furthermore, the beam spot 6 used for reproduction can be made very small.

  Further, in the optical disc 1, the number of divisions (the number of partial light receiving surfaces) of the light receiving surface of the photodetector 31 necessary for information reproduction can be made six.

That is, when the pit arrangement of the information unit 5 is composed of only six phase pits 3, the reflection intensity distribution from the information unit 5 corresponds to a hexagon (if there are all phase pits, Square).
For this reason, the photodetector 31 used for information reproduction has its light receiving surface divided into six parts corresponding to the six phase pits 3, and is divided into six divided light parts having six partial light receiving surfaces D1 to D6. It becomes a detector.
In the photodetector 31, the presence or absence of six phase pits 3 in the information unit 5 (which phase pit 3 has) according to the intensity of reflected light incident on each of the six partial light receiving surfaces D1 to D6. And the pit arrangement is obtained based on the discrimination result.

  Further, regarding the pit arrangement of the optical disc 1 in which the phase pit 4 is arranged at the center of the six phase pits 3, the six-divided photodetector 31 having the six partial light receiving surfaces D1 to D6 can be used.

  That is, the intensity distribution of the reflected light from the phase pit 4 becomes an intensity distribution that depends on the distance from the center of the photodetector 31 (the intensity of light incident at an equidistant position from the center of the photodetector becomes equal). Therefore, the reflected light having the same intensity is incident on each of the six partial light receiving surfaces D1 to D6 of the photodetector 31 from the phase pit 4.

Therefore, when the optical disc 1 is reproduced using the photodetector 31 that is a six-divided photodetector, the presence or absence of the phase pit 4 is determined based on the total amount of light received by the entire light receiving surface (from the entire information unit 5 (pit array)). The total reflected light amount; the total reflected light amount) can be determined.
On the other hand, as described above, the presence or absence of the phase pit 3 can be determined by the intensity of light incident on each of the six partial light receiving surfaces D1 to D6.

As described above, in the optical disc 1, the information unit 5 is configured using the seven phase pits 3 and 4, but information can be reproduced using a six-divided photodetector such as the photodetector 31. .
Therefore, the optical disk 1 is an optical disk that can record information with high density and does not require a complicated reproduction circuit for reproducing information.

  When phase pits are arranged at seven corners of the heptagon, the reflection intensity distribution from the information unit 5 corresponds to the heptagon (when there are all phase pits, it becomes a heptagon). For this reason, it is necessary to provide a partial light receiving surface according to each phase pit, and to determine the presence or absence of each phase pit based on the incident light intensity on each partial light receiving surface.

Therefore, the number of partial light receiving surfaces (number of divisions) of the photodetector needs to be seven. For this reason, a circuit for processing the intensity of incident light on each partial light receiving surface becomes complicated and the cost becomes high (particularly, the partial light quantity comparison circuit 44 for judging symmetry is complicated).
In addition, since the number of the partial light receiving surfaces of the photodetector 31 is seven, the angle difference between the adjacent light receiving surfaces is reduced, and the accuracy of determining the position of the phase pits is reduced to increase the reproduction error. is there.

Further, the present disk device includes a total light amount comparison circuit 43 and a partial light amount comparison circuit 44 in order to specify the pit arrangement of the information unit 5 to be reproduced according to the reflected laser light La.
Then, the total reflected light amount is specified by the total light amount comparison circuit 43, and the pit arrangement of the information unit 5 is roughly determined (for each light amount identifier).
Thereafter, the partial light quantity comparison circuit 44 compares (partial comparison) the magnitudes of the light incident on the partial light receiving surfaces D1 to D6 according to the specified total reflected light quantity, and specifies the pit arrangement of the information unit 5. It is like that.

As described above, in this configuration, the pit arrangement is roughly determined by the total light amount comparison circuit before performing the partial comparison by the partial light amount comparison circuit.
Therefore, it is possible to reduce the type and number of partial comparisons necessary for specifying the pit arrangement by the partial light quantity comparison circuit.

  Further, in the present disc device, one of the dividing lines A to C that divide the partial light receiving surfaces D1 to D6 in the photodetector 31 is orthogonal to the straight line X-X ′ corresponding to the information track 2 of the optical disc 1.

Here, the photodetector 31 may be arranged so that one of the dividing lines A to C overlaps (is parallel to) the straight line XX ′ corresponding to the information track 2. Even in this configuration, the pit arrangement of the information unit 5 can be identified by a similar identification process.
However, in this case, there is a dividing line at the position where the light intensity change is the largest (the position corresponding to each phase pit 3). For this reason, the detection accuracy of the light intensity distribution by the partial light receiving surfaces D1 to D6 is lowered.

Therefore, in order to improve the detection accuracy, it can be said that the dividing lines A to C are preferably arranged so as to be orthogonal to the information track 2 of the optical disc 1.
In this case, the centers of the partial light receiving surfaces D1 to D6 can be arranged at positions corresponding to the respective phase pits 3 (positions where reflected light from the respective phase pits 3 becomes maximum). Accordingly, the phase pits 3 can be made to correspond one-to-one with each of the six partial light receiving surfaces D1 to D6. For this reason, the presence or absence of the six types of phase pits 3 can be clearly determined by the six partial light receiving surfaces D1 to D6.

In this way, an effective effect can be obtained by making the dividing lines A to C orthogonal to the straight line XX ′. This is because one diagonal passing through the center of the hexagon formed by the six phase pits 3 is information. This is because it overlaps track 2.
That is, the above effects can be obtained by making the dividing lines A to C orthogonal to a straight line on the light receiving surface corresponding to the hexagonal diagonal. If this diagonal line and one of the dividing lines A to C are orthogonal, the same effect can be obtained even when one of the dividing lines A to C is not orthogonal to the straight line XX ′.

  Note that, when one hexagonal diagonal line overlaps the information track 2 as in the present disk device, it is easy to make the pit arrangement of the information unit 5 symmetrical with respect to the information track 2 as an axis. .

  Further, in the present disk device, the dividing lines A to C of the photodetector 31 are arranged in a state shifted by 60 degrees so that the light receiving surface is divided into six equal parts. Thereby, since the size of each partial light-receiving surface D1-D6 can be made equal, the comparison process of light reception signal R1-R6 by the partial light quantity comparison circuit 44 can be performed easily.

  Further, the present disk device includes a control photodetector 29 that is separate from the photodetector 31. The reflected light applied to the control light detector 29 is focused by the cylindrical lens 28, so that the wave front is disturbed. Therefore, if the control light detector 29 and the light detector 31 are shared by a single light detector, the light detector 31 is irradiated with reflected light with a disturbed wavefront. For this reason, the light intensity distribution on the partial light receiving surfaces D1 to D6 is disturbed, and it becomes difficult to accurately specify the pit arrangement of the information unit 5.

  Therefore, in the present disk device configuration, by providing both the photodetectors separately, it is possible to avoid irradiating the photodetector 31 with the reflected light with a disturbed wavefront. This makes it possible to achieve both accurate light control and information reproduction.

In this embodiment, 128 types shown in FIGS. 1 and 6 are listed as the pit arrangement of the information unit 5 formed on the optical disc 1.
However, the number of pit arrangement types may be set to less than 128 types.

For example, the information unit 5 of the optical disc 1 may be set so as to form only a pit array having the light quantity identifiers b, d, f, and h.
In this case, there are 64 types of pit arrangements, and 6-bit data is multiplexed and recorded in one information unit 5.

  Further, identification of these pit arrangements is performed under the conditions shown in Tables 1 to 3 above. Table 5 shown below extracts only the identification conditions related to the light quantity identifiers b, d, f, and h from Tables 1 to 3.

  The pit arrangements shown in this table all have an odd number of phase pits 3. In this case, the difference in total reflected light amount reflected from the information unit 5 can be increased.

That is, when all the pit arrangements shown in FIGS. 1 and 6 are used, there are nine types of total reflected light amounts to be identified.
On the other hand, when only the pit arrangement of the light quantity identifiers b, d, f, and h is used, there are four types of total reflected light quantity to be identified, and the pit arrangement of the light quantity identifiers a, c, e, and g between these. Since there is no (pit arrangement having an even number of phase pits 3), the difference in the total amount of reflected light increases.

  Therefore, the total reflected light amount can be easily and accurately specified by the total light amount comparison circuit 43. Therefore, since the circuit configuration of the total light quantity comparison circuit 43 can be made simpler, the cost of the present disk device can be reduced.

Similarly, as the information unit 5 of the optical disc 1, only a pit array having a light quantity identifier a, c, e, g, i (a pit array having an even number (including 0) of phase pits 3) is formed. May be set.
Also in this case, there are 64 types of pit arrangements, and 6-bit data is multiplexed and recorded in one information unit 5.

  Further, identification of these pit arrangements is performed under the conditions shown in Tables 1 to 3 above. Table 6 shown below extracts only the identification conditions related to the light quantity identifiers a, c, e, g, and i from Tables 1 to 3.

Alternatively, the information unit 5 of the optical disc 1 may be set so as to form only the pit arrangement shown in Table 7.
Also in this case, there are 64 types of pit arrangements, and 6-bit data is multiplexed and recorded in one information unit 5.

In these pit arrangements, the phase pits 3 are arranged symmetrically with respect to one of the diagonal lines that bisect the hexagon forming the information unit 5.
Here, there is a pit arrangement which has the symmetry as described above but is not shown in Table 7 (111g1 and 108g1). This is a result of selecting a pit arrangement that is relatively easy to identify because there are 64 types of pit arrangements.

Here, some of the pit arrangements shown in FIGS. 1 and 6 cannot be identified only from the magnitude relationship of the received light signals R1 to R6, but can be identified using the reference value S1. For example, the pit arrays 26d1 and 31d1 are identified from the comparison result between X2-X3 and the reference value S1 (Table 1).
This is because these pit arrangement shapes (pit arrangement state) are similar, and cannot be identified only from the symmetry of the pit arrangement.

In this case, since the value of X2-X3 is compared with the fixed reference value S1 (reference signal) , the intensity of the laser beam L needs to be controlled with high accuracy in order to reproduce without causing an error. . Therefore, a complicated (high accuracy) circuit is used as the laser control circuit 42 for controlling the semiconductor laser light source 21.

On the other hand, none of the pit arrangements shown in Table 7 requires the reference value S1. Therefore, all the pit arrangements can be identified only by the magnitude relationship of the light reception signals R1 to R6.
As a result, even when the intensity of the laser beam L slightly varies, accurate identification can be performed. Accordingly, since a simpler circuit can be used as the laser control circuit 42, the cost of the present disk device can be reduced.

Alternatively, the information unit 5 of the optical disc 1 may be set to form only the pit arrangement shown in Table 8.
In this case, there are 32 types of pit arrangements, and 5-bit data is multiplexed and recorded in one information unit 5.

  In these pit arrangements, the phase pits 3 are arranged symmetrically with respect to the information track 2 (the pit arrangement is symmetrical in the radial direction).

  As described above, in the present disk device, the control photodetector 29 generates a focusing signal by the astigmatism method based on the reflected laser light La from the information unit 5, and generates a tracking signal by the push-pull method. It is designed to generate.

  Therefore, when the pit arrangement is asymmetric in the radial direction, the push-pull signal is disturbed, and there is a possibility that the beam spot 6 of the laser light L cannot be scanned on the central axis of the information track 2 (tracking becomes unstable). is there. If the tracking becomes unstable, it becomes impossible to measure the accurate total amount of reflected light from each information unit 5, resulting in an increase in reproduction errors.

  On the other hand, when only 32 types of pit arrangements as shown in Table 8 are used, since all the pit arrangements are symmetrical in the radial direction, the above-described disturbance of the push-pull signal can be reliably prevented. Thereby, stable tracking can be realized.

  In the present embodiment, the dividing lines A to C of the photodetector 31 are arranged so as to be shifted from each other by 60 degrees. However, the present invention is not limited to this, and the crossing angle of the dividing lines A to C may be shifted from 60 degrees. In this case, since the sizes of the partial light receiving surfaces D1 to D6 are different from each other, it is preferable to change the comparison processing of the received light signals R1 to R6 by the partial light quantity comparison circuit 44.

  In the present embodiment, the number of divisions of the light receiving surface of the photodetector 31 is six. However, the number of divisions of the light receiving surface of the photodetector 31 is not limited to this, and may be doubled to 12 (12-divided photodetector). And it is also possible to identify the information unit 5 based on the light reception signals from the 12 partial light receiving surfaces by using the photodetector 31. However, the calculation process for identifying the information unit 5 can be simplified by using the six-divided photodetector as described above. Accordingly, the total light quantity comparison circuit 43 and the partial light quantity comparison circuit 44 can be configured with simpler circuits, so that the cost of the disk device can be reduced.

  Here, specific examples relating to the manufacture and reproduction of the optical disc 1 will be described as Examples 1 to 4.

[Example 1]
The information units 5 having the pit arrangement shown in FIGS. 1 and 6 are regularly arranged at a pitch of 350 nm on the information track 2 formed in a spiral shape on the optical disc 1.
Further, the phase pits 3 and 4 were formed in the shape of depressions having a depth of 40 nm by injection molding on the recording surface of the transparent substrate 7 made of polycarbonate.

  The diameter of the phase pits 3 and 4 was set to 60 nm, and the formation pitch of the phase pits 3 and 4 was set to 100 nm.

  Patterning of the master for forming the transparent substrate 7 having such phase pits 3 and 4 was performed using an electron beam exposure apparatus.

  Next, an optical disk stamper was formed from the master, and a transparent substrate 7 was formed by performing injection molding using the stamper.

  Next, a metal reflective film 8 made of aluminum was formed to a thickness of 50 nm on the transparent substrate 7 on which the information unit 5 was formed by sputtering. Further, a 0.1 mm thick polycarbonate sheet was bonded to the metal reflective film 8 as a protective film 9 with an ultraviolet curable resin.

  Such an optical disc 1 was mounted on the disc apparatus shown in FIG. 3 and played back.

Here, a semiconductor laser element having a wavelength of 405 nm was used as the semiconductor laser light source 21. Further, a lens having a numerical aperture (NA) of 0.85 was used as the condensing lens 24 for condensing the laser light L onto the optical disc 1.
Further, the laser beam L was incident from the protective film 9 side of the optical disc 1.

  In reproduction, focusing was performed by the control unit and the focusing / tracking circuit 47 so that the laser beam L was condensed on the metal reflection film 8, and tracking was performed along the information track 2.

  Further, the received light signals R1 to R6 of the detection elements D1 to D6 of the photodetector 31 were processed by the total light quantity comparison circuit 43 and the partial light quantity comparison circuit 44 according to the identification conditions as shown in Tables 1 to 3. As a result, 128 types (7 bits) of pit arrangements in the information unit 5 could be identified, and 7 bits of data could be demodulated.

[Example 2]
In addition, in the configuration of the optical disc 1 shown in Example 1, the optical disc 1 having only the pit arrangement shown in Table 5 was formed and mounted on the disc apparatus for reproduction. Further, for the discrimination processing / identification processing of the total light quantity comparison circuit 43 and the partial light quantity comparison circuit 44, the method shown in Table 5 was used.
As a result, 64 types (6 bits) of pit arrangements in the information unit 5 can be identified, and 6-bit data can be demodulated.

In addition, in the configuration of the optical disc 1 shown in Example 1, the optical disc 1 having only the pit arrangement shown in Table 6 was formed and mounted on the disc apparatus for reproduction. Further, for the discrimination processing / identification processing of the total light quantity comparison circuit 43 and the partial light quantity comparison circuit 44, the method shown in Table 6 was used.
As a result, 64 types (6 bits) of pit arrangements in the information unit 5 can be identified, and 6-bit data can be demodulated.

Example 3
In addition, in the configuration of the optical disc 1 shown in Example 1, the optical disc 1 having only the pit arrangement shown in Table 7 was formed and mounted on the disc apparatus for reproduction. Further, for the discrimination processing / identification processing of the total light quantity comparison circuit 43 and the partial light quantity comparison circuit 44, the method shown in Table 7 was used.
As a result, 64 types (6 bits) of pit arrangements in the information unit 5 can be identified, and 6-bit data can be demodulated.

Example 4
In addition, in the configuration of the optical disc 1 shown in Example 1, the optical disc 1 having only the pit arrangement shown in Table 8 was formed and mounted on the disc apparatus for reproduction. Further, for the discrimination processing / identification processing of the total light quantity comparison circuit 43 and the partial light quantity comparison circuit 44, the method shown in Table 8 was used.
As a result, 32 types (4 bits) of pit arrangements in the information unit 5 can be identified, and 4 bits of data can be demodulated.

Here, the manufacture of the optical disc 1 will be briefly described.
In the production of the transparent substrate 7 having the phase pits 3 and 4 constituting the information unit 5, the position of the phase pits 3 and 4 is synchronized with the rotation of the master with respect to the master for forming the transparent substrate 7. Then, exposure is performed by irradiating an electron beam or a light beam.

  Here, in the case of electron beam exposure, the movement of the electron beam is stopped for a certain period of time at a position where a phase pit should be formed in synchronization with the rotation of the master. Thereby, the phase pit is exposed and formed on the master. Thereafter, the electron beam is moved at a high speed to the position of the next phase pit, and the next phase pit is exposed.

For example, when the pit array 34d1 is formed, the phase pit 3 (vertical angle P6; see FIG. 7) at the left end of the hexagon is exposed and formed, and then the electron beam is moved at high speed to escape outside the range of the master.
Next, in synchronism with the rotation of the master, the electron beam is moved at a high speed to the position of the apex angle P1 which is the second upper side from the left, and the electron beam is stopped at that position for a certain period of time to form a phase pit.
Next, the electron beam is moved at a high speed to the position of the apex angle P5 which is the second lower side from the left, and the electron beam is stopped at that position for a certain period of time to form a phase pit by exposure.

When using a light beam, the light beam is divided into three. Then, the condensing position of each light beam is set to the phase pit position (vertical angle P1, P2) above the information track, the phase pit position (vertical angle P3, P6, center) on the information track 2, the information track It is assumed that the phase pit position (vertical angle P4, P5) is lower than 2.
Then, the light beam is irradiated with pulses at the position where each phase pit is formed.

In the present embodiment, the phase pit 3 is arranged at the apex position of a regular hexagon. However, the arrangement position of the phase pit 3 is not limited to this.
For example, the phase pit 3 may be arranged at the apex angle of another hexagon (a regular hexagon compressed in the circumferential direction or the radial direction) symmetrical in the circumferential direction and the radial direction. Even in this configuration, the pit arrangement of the information unit 5 can be identified by the present disk device in the same manner as described above.

  Further, the phase pits 3 may be arranged at a rectangular apex position. Even in this case, the pit arrangement can be specified by appropriately setting the processing (identification condition) by the partial light quantity comparison circuit 44.

  FIG. 9 shows the type of pit arrangement (information information) when the phase pit 3 is arranged at the apex position (position equidistant from the center of the square) of a square (regular tetragon) where one of the diagonal lines overlaps the information track 2. It is explanatory drawing which shows a kind.

  In this case, in the optical disc 1, the information unit 5 is designed to take 32 pit arrangements 1ax to 32jx. That is, the information unit 5 is designed to have 32 kinds of information corresponding to the pit arrangements 1ax to 32jx.

  Here, the pit array 1ax is in a state where there is no phase pit. The pit arrangements 2by, 3by, 4by, 5by, and 6cx are arrangement states having one phase pit. Furthermore, the pit arrangements 7dx, 8dx, 9dy, 10dy, 11dy, 12dy, 13ey, 14ey, 15ey, and 16ey are arrangement states composed of two phase pits. The pit arrangements 17fy, 18fy, 19fy, 20fy, 21gy, 22gy, 23gy, 24gy, 25gx, and 26gx are arrangement states formed by three phase pits. The pit arrays 27hx, 28iy, 29iy, 30iy, and 31iy are an array state including four phase pits. Finally, the pit array 32jx is an array state composed of five phase pits.

  The symbols of the pit arrangements 1ax to 32jx are combinations of “serial number, light quantity identifier, symmetry identifier” as described above. That is, the serial numbers are numbers (1 to 32) assigned to all 32 types of pit arrangements.

  The light quantity identifier corresponds to the total light quantity (total reflected light quantity) of the reflected laser light La incident on the photodetector 31 from the information unit 5 having the pit arrangement. In this case, the total reflected light quantity of each pit arrangement is classified by 10 kinds of light quantity identifiers a to j. In the pit arrangement having the same light quantity identifiers a to j, the total reflected light quantity is almost equal. Further, the total amount of reflected light decreases in the order of a to j.

Here, the relationship between the number and position of the phase pits 3 and 4 and the total amount of reflected light will be described.
As described above, when the phase pits 3 and 4 are present, the amount of reflected light is smaller than when the phase pits 3 and 4 are not present. In addition, the intensity distribution of the beam spot 6 in the laser light L is a Gaussian distribution. Therefore, the light intensity at the center of the beam spot 6 is stronger than that of the surrounding area.

  Further, as described above, the laser beam L is irradiated so that the center position of the beam spot 6 overlaps the center position of the information unit 5. For this reason, the amount of reflected light tends to be smaller when the phase pit 4 is present at the center position than when the phase pit 3 is present at the apex angle position.

  In each of the pit arrays 2by to 5by, one phase pit 3 corresponding to the outer peripheral position of the beam spot 6 exists, and the total reflected light amount becomes equal. Further, in the pit arrangement 6cx, since one phase pit 4 corresponding to the center position of the beam spot 6 exists, the total reflected light amount becomes smaller than that of the pit arrangements 2by to 5by.

Next, in 7dx to 12dy having two phase pits 3, the total reflected light amount becomes smaller than the pit arrangement 6cx due to the increase in the number of phase pits.
Further, the pit sequence 13 gy ~16ey, because it has a phase pit 4 and the phase pit 3 one by one, the total amount of reflected light becomes smaller than the pit sequence 7Dx～12dy. Thereafter, in the same manner, the total amount of reflected light decreases as the number of phase pits increases.

Also, the symmetry identifier of the pit arrangement is a pit arrangement with respect to the direction in which the information track 2 extends (circumferential direction) and the radial direction of the optical disc 1 (the direction perpendicular to the information track 2 and passing through the center of the pit arrangement (radial direction)). Is an identifier (x or y) indicating the symmetry of.
That is, when the pit arrangement is line symmetric in the circumferential direction (when it is line symmetric with respect to the axis along the radial direction) and when it is also line symmetric in the radial direction (in the information track 2) The symmetry identifier is x).
On the other hand, if it is not line symmetric with respect to any direction, the symmetry identifier is y.

Next, the configuration of the photodetector 31 when the phase pits 3 and 4 are arranged as shown in FIG. 9 will be described.
FIG. 10 is an explanatory diagram showing the configuration of the photodetector 31 used in this case. As shown in this figure, the photodetector 31 includes four partial light receiving surfaces (light detecting elements) D1 to D4 obtained by dividing the light receiving surface into four parts.

  The partial light receiving surfaces D1 to D4 are formed by dividing the circular light receiving surface in the photodetector 31 by two dividing lines A and B that pass through the center of the light receiving surface and are orthogonal to each other. The fan 31 has a fan shape extending radially from the center of the light receiving surface of the vessel 31.

The partial light receiving surfaces D1 to D4 respectively output voltage signals (light receiving signals) R1 to R4 having voltage values corresponding to the amount of reflected light received by the partial light receiving surfaces D1 to D4.
Further, in the photodetector 31, the dividing lines A and B dividing the partial light receiving surfaces D1 to D4 correspond to straight lines corresponding to the information track 2 of the optical disc 1 (corresponding to information tracks on the light receiving surface of the photodetector 31). It is arranged so as to form an angle of 45 ° with XX ′.

Here, the relationship between each phase pit 3 * 4 and the partial light-receiving surfaces D1-D4 is demonstrated.
As described above, the reflected light from the individual phase pits becomes diffracted light and enters the entire surface of the partial light receiving surfaces D1 to D4. When there are a plurality of phase pits, the diffracted light from each phase pit interferes and enters the partial light receiving surfaces D1 to D4. That is, the reflected light from each phase pit is incident on all but not one of the partial light receiving surfaces D1 to D4.

  However, the reflected light from one phase pit 3 has a relatively high intensity incident on any of the partial light receiving surfaces D1 to D4 at the position corresponding to the phase pit 3 (far from the phase pit 3). The intensity of light incident on the element at the position is relatively small). For example, in the pit arrangement 2by, the intensity of light incident on the partial light receiving surface D2 is relatively large, and the intensity of light incident on the partial light receiving surface D4 is relatively small.

  Further, the reflected light from the phase pit 4 located at the center of the quadrangle is uniformly incident near the center of all the partial light receiving surfaces D1 to D4. Therefore, in the pit arrangement 6cx having only one phase pit 4, the intensity of light incident near the center of all the partial light receiving surfaces D1 to D4 is relatively large, and the intensity of light incident on the peripheral area is relatively high. Becomes smaller.

Next, the operation of the circuits 43 to 46 of the circuit board 12 when the phase pits 3 and 4 are arranged as shown in FIG. 9 will be described.
As described above, these circuits 43 to 46 identify the pit arrangement of the information unit 5 related to reproduction based on the received light signal output from the photodetector 31, and generate a reproduction signal according to the identification result. It is a circuit group.

  In this case, the total light quantity comparison circuit 43 adds the light reception signals R1 to R4 output from all the partial light receiving surfaces D1 to D4 of the photodetector 31 to obtain the total reflected light quantity. And the light quantity identifier aj in the pit arrangement | sequence of the information unit 5 concerning reproduction | regeneration is derived | led-out from the value.

  In the pit arrangements 1ax, 6cx, 27hx, and 32jx, there is no other pit arrangement having the same total reflected light amount. For this reason, when the information unit 5 related to reproduction has the above pit arrangement, the identification of the pit arrangement is completed only by the total light quantity comparison circuit 43.

  The partial light quantity comparison circuit 44 identifies the pit arrangement of the information unit 5 related to reproduction based on the light quantity identifiers a to j derived from the total light quantity comparison circuit 43. Table 9 shows identification conditions by the partial light quantity comparison circuit 44.

As shown in this table, the partial light quantity comparison circuit 44 calculates the magnitude relationship of the light reception signals R1 to R4 according to the light quantity identifiers a to j. That is, the partial light quantity comparison circuit 44 first calculates (compares) the magnitude relationship between R2 and R4 (identification condition I).
Next, the partial light quantity comparison circuit 44 calculates the magnitude relationship between R1 and R3 (identification condition II), and finally calculates the magnitude relationship between R1 and R2 (identification condition III). As a result, all the information units 5 can be identified.

  In this way, the partial light quantity comparison circuit 44 can identify all 32 types of pit arrangements by comparing the intensities of the received light signals R1 to R4 based on the light quantity identifier.

  The demodulating circuit 45 generates a demodulated signal (demodulated data) based on the identification result of the pit arrangement by the partial light quantity comparing circuit 44. Table 9 shows the demodulated signal corresponding to each pit arrangement.

  As described above, when the phase pits 3 and 4 are arranged as shown in FIG. 9, there are 32 types of pit arrangements in the information unit 5. Therefore, 32 types of information can be multiplexed and recorded using one information unit 5. Therefore, a 5-bit demodulated signal can be obtained from one information unit 5.

As described above, in the optical disc 1 in which the phase pits 3 and 4 are arranged as shown in FIG. 9, the pit arrangement of the information unit 5 is five phase pits, that is, one phase pit 4 arranged on the information track 2. And a combination of the four phase pits 3 positioned around it.
Here, the phase pit 3 is a phase pit arranged at a rectangular apex position where one diagonal line overlaps the information track 2. The phase pit 4 is a phase pit arranged at the center position of the rectangle.

  As described above, the optical disc 1 is designed so that the pit arrangement of the information unit 5 is formed by the four phase pits 3 and the one phase pit 4 at the center.

  Accordingly, 32 (25) types of information (5-bit data) can be multiplexed and recorded with respect to one information unit 5. Therefore, a large-capacity optical disk having a remarkably high recording density can be configured as compared with the case where the pit arrangement is configured by only four phase pits 3.

  Further, in this configuration, the number of divisions (the number of partial light receiving surfaces) of the light receiving surface of the photodetector 31 necessary for reproducing information can be made four. That is, when the pit arrangement of the information unit 5 is composed of only four phase pits 3, the reflection intensity distribution from the information unit 5 corresponds to a quadrangle (when there are all phase pits, Become).

  For this reason, the light detector 31 used for information reproduction has its light receiving surface divided into four so as to correspond to the four phase pits 3, and has four partial light receiving surfaces D1 to D4. It becomes a detector. In the photodetector 31, the presence or absence of the four phase pits 3 in the information unit 5 (which phase pit 3 has) according to the intensity of the reflected light incident on each of the four partial light receiving surfaces D1 to D4. And the pit arrangement is obtained based on the discrimination result.

Further, with respect to the pit arrangement of the optical disc 1 in which the phase pit 4 is arranged in the center of the four phase pits 3, the same photodetector 31 having the four partial light receiving surfaces D1 to D4 can be used.
That is, the intensity distribution of the reflected light from the phase pit 4 becomes an intensity distribution that depends on the distance from the center of the photodetector 31 (the intensity of light incident at an equidistant position from the center of the photodetector becomes equal). Therefore, the reflected light having the same intensity is incident on each of the four partial light receiving surfaces D1 to D4 in the photodetector 31 from the phase pit 4.

Therefore, when the optical disc 1 is reproduced using the photodetector 31 that is a four-divided photodetector, the presence or absence of the phase pit 4 is determined based on the total amount of light received by the entire light receiving surface (from the entire information unit 5 (pit array)). The total reflected light amount; the total reflected light amount) can be determined.
On the other hand, as described above, the presence or absence of the phase pit 3 can be determined by the light intensity incident on each of the four partial light receiving surfaces D1 to D4.

  As described above, in the optical disc 1, the information unit 5 is configured using the five phase pits 3 and 4, but it is possible to reproduce information using a quadrant photodetector such as the photodetector 31. . Therefore, the optical disk 1 is an optical disk that can record information with high density and does not require a complicated reproduction circuit for reproducing information.

  When phase pits are arranged at the five corners of the pentagon, the reflection intensity distribution from the information unit 5 corresponds to the pentagon (when there are all phase pits, it becomes a pentagon). For this reason, it is necessary to provide a partial light receiving surface according to each phase pit, and to determine the presence or absence of each phase pit based on the incident light intensity on each partial light receiving surface. Therefore, the number of partial light receiving surfaces (number of divisions) of the photodetector needs to be five. For this reason, a circuit for processing the intensity of incident light on each partial light receiving surface becomes complicated and the cost increases (particularly, the partial light quantity comparison circuit 44 becomes complicated).

  Further, in the optical disk 1 having the pit arrangement shown in FIG. 9, phase pits 3 and 4 are arranged at the apex and center of a quadrangle. Accordingly, the density of the phase pits in the optical disc 1 can be increased, so that the recording density can be further improved.

  Also in this configuration, the total light amount comparison circuit 43 and the partial light amount comparison circuit 44 are provided in order to specify the pit arrangement of the information unit 5 to be reproduced according to the reflected laser light La. Then, the total reflected light amount is specified by the total light amount comparison circuit 43, and the pit arrangement of the information unit 5 is roughly determined (for each light amount identifier). Thereafter, the partial light quantity comparison circuit 44 compares (partial comparison) the magnitudes of the light incident on the partial light receiving surfaces D1 to D4 according to the specified total reflected light quantity, and specifies the pit arrangement of the information unit 5. It is like that.

  As described above, even in this configuration, the pit arrangement is roughly determined by the total light amount comparison circuit before performing the partial comparison by the partial light amount comparison circuit. Therefore, it is possible to reduce the type and number of partial comparisons necessary for specifying the pit arrangement by the partial light quantity comparison circuit.

  When reproducing the optical disk 1 having the pit arrangement shown in FIG. 9, in this disk apparatus, the dividing lines A and B for dividing the partial light receiving surfaces D1 to D4 in the photodetector 31 are the information tracks 2 of the optical disk 1. And an angle of 45 ° with the straight line XX ′ corresponding to.

Here, the photodetector 31 may be arranged so that one of the dividing lines A and B overlaps with the straight line XX ′ corresponding to the information track 2 (in parallel). Even in this configuration, the pit arrangement of the information unit 5 can be identified by a similar identification process.
However, in this case, there is a dividing line at the position where the light intensity change is the largest (the position corresponding to each phase pit 3). For this reason, the detection accuracy of the light intensity distribution by the partial light receiving surfaces D1 to D4 is lowered.

  Therefore, in order to improve the detection accuracy, it can be said that the dividing lines A and B are preferably arranged at an angle of 45 ° with the straight line X-X ′ corresponding to the information track 2 of the optical disc 1.

  In this case, the centers of the partial light receiving surfaces D1 to D4 can be arranged at positions corresponding to the respective phase pits 3 (positions where reflected light from the respective phase pits 3 becomes maximum). Accordingly, the phase pits 3 can be made to correspond one-to-one with each of the four partial light receiving surfaces D1 to D4. Therefore, the presence / absence of the four types of phase pits 3 can be clearly determined by the four partial light receiving surfaces D1 to D4.

Thus, an effective effect can be obtained by intersecting the dividing lines A and B with the straight line XX ′ at an angle of 45 °. This is because one diagonal line of the quadrangle formed by the four phase pits 3 is This is because it overlaps with the information track 2. That is, the above-described effects can be obtained by intersecting the dividing lines A and B with a straight line on the light receiving surface corresponding to one diagonal line of the square at an angle of 45 degrees.
With such a configuration, the same effect can be obtained even when the dividing lines A and B do not intersect the straight line XX ′ at an angle of 45 °.

  When one of the diagonal lines of the quadrangle overlaps the information track 2, it is possible to obtain an effect that the pit arrangement of the information unit 5 can be easily line-symmetrical about the information track 2.

  In the configuration shown in FIG. 10, the dividing lines A and B of the photodetector 31 are orthogonal to each other. Thereby, since the size of each partial light-receiving surface D1-D4 can be made equal, the comparison process of light reception signal R1-R4 by the partial light quantity comparison circuit 44 can be performed easily.

  In the present embodiment, as shown in FIG. 2, the total light quantity comparison circuit 43 is positioned in front of the partial light quantity comparison circuit 44. When reproducing the optical disk 1 having the pit arrangement shown in FIG. 9, after determining the light quantity identifier by the total light quantity comparison circuit 43, the partial light quantity comparison circuit 44 uses the light quantity identifier and the received light signals R1 to R4. Based on this, the pit arrangement of the information unit 5 is identified.

  However, the present invention is not limited to this, and the partial light quantity comparison circuit 44 may be arranged before the total light quantity comparison circuit 43. Table 10 shows a method for identifying the pit arrangement in this configuration.

As shown in Table 10, in this configuration, the partial light quantity comparison circuit 44 performs symmetry determinations I to III of the pit arrangement of the information unit 5 based on the light reception signals R1 to R4.
In Table 10, T1 and T2 are (R1 + R3) and (R2 + R4), respectively. S1 to S4 are (R1 + R2), (R2 + R3), (R3 + R4), and (R4 + R1), respectively.

  That is, in this case, the partial light quantity comparison circuit 44 calculates the magnitude relationship between T1 and T2 in the symmetry determination I. Then, in the symmetry determination II, the magnitude relationship between S1 and S3 is calculated. Further, the partial light quantity comparison circuit 44 calculates the magnitude relationship between S2 and S4 in the symmetry determination III.

By such calculation (comparison), the partial light quantity comparison circuit 44 determines which of the 15 types of small groups classified by the symmetry determinations I to III the pit arrangement of the information unit 5 belongs to.
Thereafter, the total light quantity comparison circuit 43 specifies the pit arrangement based on the type of the small group to which the pit arrangement belongs and the total reflected light quantity of the pit arrangement.

  In this configuration, the total light amount comparison circuit 43 can use the information of the small group to which the pit arrangement belongs in addition to the total reflected light amount. For this reason, there are two or four types of total reflected light amounts to be identified. Therefore, the accuracy of identification of the total reflected light amount by the total light amount comparison circuit 43 can be improved as compared with the case of Table 9 where it is necessary to identify the ten types of total reflected light amounts a to j.

Further, the total light quantity comparison circuit 43 can be constituted by a simple circuit (a relatively simple comparison circuit). That is, when there are many types of total reflected light amounts to be identified by the total light amount comparison circuit 43, a slight change in the laser light L may change the total reflected light amount, which may make it difficult to arrange the pits in the information unit 5.
Therefore, in this case, it is preferable to increase the control accuracy of the laser control circuit 42 and the control accuracy (tracking and focusing accuracy) of the focusing / tracking circuit 47.

On the other hand, when the number of types of total reflected light amount identification by the total light amount comparison circuit 43 is reduced as in the configuration using Table 10, the difference between the light amounts to be identified by the total light amount comparison circuit 43 can be made relatively large.
For this reason, it is possible to accurately specify the light quantity identifier for the pit arrangement for reproduction without increasing the control accuracy of the laser control circuit 42 and the focusing / tracking circuit 47.

Here, focusing control and tracking control in this disk apparatus will be described.
In the present disk device, the control light detector 29 and the focusing / tracking circuit 47 perform focusing control and tracking control using the reflected light from the information unit 5 shown in FIG. 1, FIG. 6 or FIG. Designed to.

  FIG. 11 is an explanatory diagram showing the configuration of the control photodetector 29. As shown in this figure, the control light detector 29 is a four-divided detection element including four partial light-receiving surfaces (light detection elements) D5 to D8, which are obtained by dividing the light-receiving surface into four.

  The partial light receiving surfaces D5 to D8 are formed by dividing the circular light receiving surface in the control photodetector 29 by two dividing lines C and D that pass through the center of the light receiving surface and are orthogonal to each other. The control light detector 29 has a fan-like shape extending radially from the center of the light receiving surface.

  The partial light receiving surfaces D5 to D8 output voltage signals (light receiving signals) R5 to R8 having voltage values corresponding to the amount of reflected light received by the partial light receiving surfaces D5 to D8, respectively. Further, in the control light detector 29, the dividing line D dividing the partial light receiving surfaces D5 to D8 is a straight line corresponding to the information track 2 of the optical disc 1 (information track on the light receiving surface of the control light detector 29). A straight line corresponding to 2) is arranged so as to overlap (match) XX ′.

  The focusing / tracking circuit 47 generates a focusing signal by the astigmatism method and a tracking signal by the push-pull method based on the received light signals R5 to R8 generated by the control photodetector 29. is there. The focusing / tracking circuit 47 has a function of driving the actuator 25 based on the focusing signal and the tracking signal to perform focusing control and tracking control.

In the following, focusing control and tracking control operations in this disk apparatus will be described.
In the reproduction of the optical disk 1 in this disk apparatus, the control unit controls the spindle control circuit 41 to rotate the optical disk 1. Further, the control unit controls the laser control circuit 42 to irradiate the optical disk 1 with the laser light L from the condenser lens 24, and as shown in FIG. 12, the beam spot 6 is generated along the information track 2 of the optical disk 1. Scan. At this time, the laser beam L is irradiated so that the center position of the beam spot 6 overlaps the information track 2.

  Then, the information unit 5 reflects the laser beam L, generates a reflected laser beam La, and irradiates the control photodetector 29. Thereby, the partial light receiving surfaces D5 to D8 of the control light detector 29 output received light signals R5 to R8 having voltage values corresponding to the amount of reflected light received by the control light detector 29 to the focusing / tracking circuit 47, respectively.

  The focusing / tracking circuit 47 to which the light reception signals R5 to R8 are input performs focusing control and tracking control according to instructions from the control unit. That is, the focusing / tracking circuit 47 first generates a focusing signal using the astigmatism method using the cylindrical lens 28 in order to focus the laser beam L on the recording surface of the optical disc 1 (to perform focusing control). .

  At this time, the focusing / tracking circuit 47 receives the received light signals R5 to R8 from the control photodetector 29 and calculates (R5 + R7) − (R6 + R8). Then, a focusing signal for controlling the position of the focusing lens 24 in the focus direction (direction perpendicular to the surface of the optical disc 1) is generated so that the calculated value becomes zero (0). And it outputs to the actuator 25 which controls the position of the condensing lens 24. FIG. As a result, the laser beam L can be focused on the recording surface of the optical disc 1.

Further, the focusing / tracking circuit 47 generates a tracking signal using a push-pull method in order to make the center of the laser light L follow the information track 2 (tracking control).
At this time, the focusing / tracking circuit 47 receives the received light signals R5 to R8 from the control photodetector 29 and calculates (R5 + R6) − (R7 + R8). Then, a tracking signal for controlling the position of the condensing lens 24 in the tracking direction (the radial direction of the optical disc 1) is generated and output to the actuator 25 so that the calculated value becomes zero (0).
As a result, the center position of the beam spot 6 can be overlapped with the center position of the information unit 5.

Further, in the configuration of the optical disc 1 shown in FIG. 1, FIG. 6 or FIG. 9, as shown in FIG. 13, a synchronization unit 61 for generating a synchronization signal may be provided.
As shown in FIG. 13, in this configuration, the information track 2 includes sectors including a synchronization area (synchronization signal area) DA and a recording area KA continuously and periodically along its extending direction. Is formed.
The recording area KA is an area having a plurality of information units 5.

The synchronization area DA is an area arranged at the head position of the sector, and a plurality of synchronization units 61 having the same shape are arranged at equal intervals.
That is, as shown in FIG. 13, the optical disk 1 is provided with a synchronization area DA so as to precede the recording area KA in which the information unit 5 is formed. In the synchronization area DA, a plurality of synchronization units 61 provided at equal intervals are formed on the information track 2.

The synchronization unit 61 is a pattern having a larger area than the phase pits 3 and 4 constituting the information unit 5 and the same depth as the phase pits 3 and 4.
Further, the synchronization area DA having such a synchronization unit 61 is provided at 20 to 40 locations per circumference of the information track 2. In each synchronization area DA, 16 to 64 synchronization units 61 are formed at the same formation pitch as the information unit 5 in the information track direction.

When reproducing the optical disk 1 including such a synchronization area DA, it is preferable to use a disk apparatus having the structure shown in FIG.
In this configuration, the circuit board 12 includes the synchronization signal generation circuit 48 in the configuration of the present disk device shown in FIG.

  The synchronization signal generation circuit 48 generates a synchronization signal S for reproducing an information signal based on the light reception signal output from the photodetector 31.

FIG. 15 is an explanatory diagram showing a configuration of the synchronization signal generation circuit 48.
The synchronization signal generation circuit 48 is an oscillation circuit generally called a PLL circuit (phase synchronization circuit).
That is, the synchronization signal generation circuit 48 has an oscillator that outputs a signal (synchronization signal) in its own loop. The synchronizing signal S is oscillated while performing feedback control so that the phase difference between the output of the oscillator and the received light signal output from the photodetector 31 is constant (zero).

  As shown in this figure, the synchronization signal generation circuit 48 includes a binarization circuit 71, a phase comparator 72, a low pass filter (LPF) 73, and a voltage controlled oscillator (VCO) 74.

The binarization circuit 71 converts the received light signal output from the photodetector 31 into a digital signal and outputs it to the phase comparator 72.
The phase comparator 72 compares the phase of this digital signal with the output signal (VCO signal) of the VCO 74. Then, a voltage signal (phase difference signal) proportional to the phase difference is output to the LPF 73.
The LPF 73 blocks a high-frequency component of the phase difference signal, smoothes the phase difference signal, and outputs it to the VCO 74.

The VCO 74 outputs a VCO signal at a certain free-running frequency. In addition, the free-running frequency (and phase) of the VCO signal is designed to change according to the voltage of the phase difference signal output from the LPF 73.
That is, the VCO 74 controls the frequency and phase of the VCO signal so that the phase difference between the light reception signal output from the photodetector 31 and the VCO signal becomes zero by this phase difference signal.
As a result, a VCO output signal (that is, the synchronization signal S) that is synchronized with the light reception signal (having the same frequency and phase as the reception signal) can be obtained.

Hereinafter, a method for generating the synchronization signal S in the present disk device shown in FIG. 14 will be described.
In the reproduction of the optical disk 1 in this disk apparatus, the control unit controls the spindle control circuit 41 to rotate the optical disk 1. Further, the control unit controls the laser control circuit 42 to irradiate the optical disc 1 with the laser light L from the condenser lens 24, and as shown in FIG. 13, the beam spot 6 is generated along the information track 2 of the optical disc 1. Scan. At this time, the laser beam L is irradiated so that the center position of the beam spot 6 overlaps the information track 2.

  Then, the laser beam L is reflected by the information unit 5 or the synchronization unit 61 to generate a reflected laser beam La, which is irradiated to the photodetector 31. In response to this, the partial light receiving surfaces D1 to D4 of the photodetector 31 generate light receiving signals R1 to R4 having voltage values corresponding to the amount of reflected light received by the partial light receiving surfaces D1 to D4.

  Here, when the beam spot 6 is in the synchronization area DA, the control unit outputs these light reception signals R1 to R4 to the synchronization signal generation circuit 48 (and the total light amount comparison circuit 43).

  FIG. 16 is a graph showing the sum (R1 + R2 + R3 + R4; total light reception signal) of all the light reception signals output from the photodetector 31 when the beam spot 6 scans (moves) on the information track 2. Here, DT is the amplitude of the total light reception signal obtained when passing through the synchronization unit 61.

In the synchronization signal generation circuit 48, when the beam spot 6 passes through the synchronization unit 61, a total light reception signal that is the sum of all the light reception signals R <b> 1 to R <b> 4 is output to the binarization circuit 71.
Then, the synchronization signal generation circuit 48 generates a synchronization signal S based on this signal and transmits it to the control unit. And a control part outputs this synchronizing signal S to the circuits 43-46 which produce | generate a reproduction signal.

Further, the circuits 43 to 46 start their operations at the timing of receiving this signal S. For example, the total light quantity comparison circuit 43 adds the light reception signals R1 to R4 output from all the partial light receiving surfaces D1 to D4 of the photodetector 31 at the timing when the synchronization signal S is received, and obtains the total reflected light quantity. .
The partial light quantity comparison circuit 44 compares (holds and compares and calculates) the intensity of the total reflected light quantity at the timing when the synchronization signal S is received.

  When the beam spot 6 is in the recording area KA, the control unit does not generate the synchronization signal S to be output to the circuits 43 to 46 but is generated by the synchronization signal generation circuit 48, and the synchronization area DA immediately before that is generated. The value of the synchronization signal S output at the time of reproduction is used (the synchronization signal S is in a latched state).

  As a result, in the present disc apparatus, the reproduction signal can be generated by discriminating the pit arrangement at the timing when the center of the beam spot 6 and the pattern center of the information unit 5 (pit arrangement center) coincide. Therefore, it is possible to accurately reproduce information.

  Note that the synchronization signal S generated at the time of reproducing the recording area KA includes an error due to a difference in pit arrangement for each information unit 5. That is, when there is no synchronization area DA, a synchronization signal synchronized with data (light reception signal from the information unit 5) obtained by reproducing the recording area KA is generated (self-clock system).

  However, in this case, as shown in FIG. 17, a phase shift occurs in the light reception signal from the information unit 5 due to the difference in the pit arrangement of the information unit 5. For this reason, an error occurs in the synchronization signal generated based on this light reception signal.

In the above description, the number of phase pits 3 of the information unit 5 in the optical disc 1 having the synchronization area DA is four. However, as shown in FIG. 18, the synchronization area DA can be similarly formed on the optical disc 1 having the information unit 5 (see FIG. 1) having six phase pits 3.
The synchronization unit 61 in the configuration shown in this figure is the same as that shown in FIG.

  Also in the optical disc 1 shown in FIG. 18, the synchronization signal S can be generated using the synchronization unit 61 as in the optical disc 1 shown in FIG. 13. Further, by comparing the total reflected light amount by the total light amount comparison circuit 43 and identifying or determining the symmetry by the partial light amount comparison circuit 44, it is possible to specify the pit arrangement of the information unit 5 and reproduce the recorded information.

  In the present embodiment, the synchronization unit 61 has a larger area than the phase pits 3 and 4 constituting the information unit 5 and has the same depth as the phase pits 3 and 4. However, the present invention is not limited to this, and the area and depth of the synchronization unit 61 can be set to values desired by the user.

  Further, as shown in FIGS. 19 and 20, the pattern of the synchronization unit 61 can be composed of phase pits similar to those of the information unit 5. That is, in the synchronization area DA in the optical disc 1 shown in FIGS. 19 and 20, a plurality of synchronization units 61 having the same configuration as the information unit 5 are arranged at equal intervals. Even when such a synchronization unit 61 is used, the synchronization signal S can be generated.

  In this case, since the phase pits 3 and 4 constituting the information unit 5 and the phase pit (pattern) constituting the synchronization unit 61 have the same size, there is an advantage that the synchronization unit 61 can be easily formed.

  That is, when the information unit 5 and the synchronization unit 61 shown in FIG. 13 are formed using the electron beam exposure apparatus, the electron beam is narrowed down to a size that allows the phase pits 3 and 4 of the information unit 5 to be formed. The phase pits 3 and 4 are exposed.

  On the other hand, in order to expose the synchronization unit 61 larger than the phase pits 3 and 4, the electron beam narrowed down similarly is continuously irradiated and moved at a high speed in a direction perpendicular to the information track 2, thereby being relatively large. Form phase pits. Therefore, since the formation methods of the phase pits 3 and 4 of the information unit 5 and the synchronization unit 61 are different, it is necessary to control the electron beam so that each can be formed optimally.

  On the other hand, as shown in FIGS. 19 and 20, the synchronization unit 61 having the same phase pit as the phase pits 3 and 4 of the information unit 5 can be formed under exactly the same conditions as the information unit 5. For this reason, since the control conditions for forming the master for the optical disk 1 can be reduced, the master and the optical disk 1 can be manufactured more easily (more stably).

  The synchronization unit 61 shown in FIGS. 19 and 20 has a pit arrangement including all the phase pits 3 and the phase pits 4. However, the synchronization unit 61 may have any pit arrangement. In the pit arrangement of the synchronization unit 61, it is preferable that the number of the phase pits 3 is equal on both sides of the “straight line that crosses the center of the information unit 5 perpendicularly to the information track 2”.

  Further, the larger the total reflected light amount change by the synchronization unit 61 is, the more accurately the synchronization signal S can be generated. Therefore, it can be said that it is preferable to use a pit arrangement including all phase pits 3 and phase pits 4 as shown in FIGS.

  Further, the synchronization unit 61 may be formed at a formation pitch that is twice the “formation pitch of the information unit 5 in the direction in which the information track 2 extends”. As a result, the signal amplitude DT of the total signal amount obtained when passing through the synchronization unit 61 can be further increased, so that the synchronization signal S can be easily generated.

Further, due to the difference in the period of the light reception signal, the information unit 5 and the synchronization unit 61 can be easily discriminated (reproduction area (DA / KA) discrimination by the control unit), and more accurate generation of the synchronization signal and more Reliable information reproduction can be realized.
In this case, by adding a frequency dividing circuit to the synchronization signal generation circuit 48, a synchronization signal S having a half period of the light reception signal from the synchronization unit 61 is generated and used for reproduction of the information unit 5. .

  Further, the formation pitch of the synchronization unit 61 is not necessarily limited to the same as or twice the “formation pitch of the information unit 5 in the extending direction of the information track 2”. The formation pitch of the synchronization unit 61 can be set to a number desired by the user as long as it is an integer multiple of the pitch of the information unit 5.

  Also, the number of synchronization units 61 in the synchronization area DA need not be limited to 16 to 64. Further, the number of synchronization areas DA in the information track 2 need not be limited to 20 to 40 locations per circle. The number of synchronization units 61 and synchronization areas DA can be set as desired by the user.

In the present embodiment, focusing and tracking are performed using the information unit 5. However, the present invention is not limited to this, and focusing and tracking may be performed using the synchronization unit 61.
In addition, the optical disk 1 includes an information unit 5 that is asymmetric with respect to the information track 2, such as pit arrays 9dy and 13ey shown in FIG. For this reason, the push-pull signal obtained from such an asymmetric information unit 5 may prevent accurate tracking. Therefore, focusing and tracking may be performed using only the synchronization unit 61.

In the present embodiment, when the beam spot 6 is in the recording area KA, the control unit outputs to the circuits 43 to 46 the synchronization signal S output at the time of reproduction of the immediately preceding synchronization area DA. At this time, the control unit may stop the operation of the synchronization signal generation circuit 48 or may be in a driven state.
In addition, the determination of the reproduction area by the control unit may be performed by any method.

  In the present embodiment, the phase pit 3 is arranged at the apex angle position of a square or a regular hexagon. However, the arrangement position of the phase pit 3 is not limited to these. For example, the phase pit 3 may be arranged at the apex angle of another quadrangle that is symmetrical in the circumferential direction and the radial direction (a rhombus obtained by compressing a regular square in the circumferential direction or the radial direction). Even in this configuration, the pit arrangement of the information unit 5 can be identified by the present disk device in the same manner as described above.

  Further, the phase pits 3 may be arranged at the apex positions of other polygons (pentagons and octagons). Even in this case, the pit arrangement can be specified by appropriately setting the processing (identification condition) by the partial light quantity comparison circuit 44.

  Further, it is preferable that the phase pits 3 of the optical disc 1 are arranged at an equal distance from the phase pits 4. Thereby, all the phase pits 3 and 4 can be arranged efficiently (with high density) in the substantially circular beam spot 6 in the laser beam L. Therefore, the recording density of the optical disc 1 can be further improved and the beam spot 6 can be reduced.

  Further, in the present embodiment, the collimator lens 22 is assumed to make the light beam of the laser light L emitted from the semiconductor laser light source 21 parallel. Here, when the laser light emission from the semiconductor laser light source 21 has an elliptical shape, the beam shape may be appropriately shaped by the collimator lens 22 (or other beam shaping member).

  Further, in the present embodiment, the optical disk 1 is assumed to have a disk shape with a diameter of 120 mm. However, in the present disk device, it is also possible to reproduce the optical disk 1 having other sizes by changing the movable range of the optical pickup 11 (actuator 25).

  In the present embodiment, the optical disk 1 has a spiral information track 2. However, the present invention is not limited to this, and a plurality of information tracks 2 may be provided concentrically on the optical disc 1.

  In this embodiment, the optical disk 1 is shown as a medium (optical memory element) to be played back by the present disk device. However, the present invention is not limited to this, and the present disk device may be designed to reproduce an optical card having information tracks arranged in a straight line. In this case, it is preferable to form an information unit 5 having a pit arrangement as shown in FIG. 1, FIG. 6 or FIG. 9 on the information track of the optical card.

  Further, in the present disk device, when a transparent material is used as the protective film 9, a laser beam is irradiated from the protective film 9 side to form a beam spot 6 on the metal reflective film 8, and reproduction is executed. Is possible. It is also possible to perform reproduction by irradiating the laser beam L from the transparent substrate 7 side of the optical disc 1.

In the present embodiment, the amount of light required by the total light amount comparison circuit 43 is the total amount of light reflected from the information unit 5 (total reflected light amount). However, strictly speaking, the light amount required by the total light amount comparison circuit 43 is the total amount of incident light (total incident light amount) with respect to the photodetector 31 (partial light receiving surfaces D1 to D4 or D1 to D6).
The total incident light amount is obtained by subtracting light (control light) traveling toward the control light detector 29 by the beam splitter 26 from the total reflected light amount, and is proportional to the total reflected light amount.

  In the configuration shown in FIG. 10, the dividing lines A and B of the photodetector 31 are arranged so as to be shifted from each other by 90 degrees. However, the present invention is not limited to this, and the crossing angle of the dividing lines A and B may be shifted from 90 degrees. In this case, since the sizes of the partial light receiving surfaces D1 to D4 are different from each other, it is preferable to change the comparison processing of the received light signals R1 to R4 by the partial light quantity comparison circuit 44.

  In the present embodiment, the light receiving surface of the photodetector 31 has a circular shape. However, the shape is not limited to this, and the shape of the light receiving surface of the photodetector 31 may be any shape as long as the entire reflected laser beam La can be received. Similarly, the light receiving surface of the control light detector 29 need not be circular.

  In the configuration shown in FIG. 10, the number of divisions of the light receiving surface of the photodetector 31 is four. However, the number of divisions of the light receiving surface of the photodetector 31 is not limited to this, and may be doubled into eight (eight division photodetector). And it is also possible to identify the information unit 5 based on the light receiving signals from the eight partial light receiving surfaces by using the photodetector 31. However, the calculation process when identifying the information unit 5 can be simplified by using the above-described quadrant photodetector. Accordingly, since the total light quantity comparison circuit 43 and the partial light quantity comparison circuit 44 can be configured with simpler circuits, the cost of the disk device can be reduced.

  If a signal based on the reflected light from the phase pits 3 and 4 constituting the information unit 5 is mixed in the focusing signal (focus servo signal) generated by the focusing / tracking circuit 47, the focusing (focus servo) is disturbed. Will be. For this reason, it is preferable to remove the high-frequency signal component corresponding to the phase pits 3 and 4 from the focusing signal through a low-pass filter. As a result, stable focusing can be performed.

  Further, the present disk apparatus shown in FIG. 14 indicates that “the light reception signals R1 to R4 (R1 to R6) obtained from the photodetector 31 are in accordance with the synchronization unit 61” (the beam spot 6 is the synchronization unit). It may be designed such that the control section transmits the information to the synchronization signal generation circuit 48 (or the synchronization signal generation circuit 48 detects itself).

  In this case, it is preferable to form a special pattern (a pattern that generates special reflected light) that does not exist as the information unit 5 (or the synchronization unit 61) before the synchronization area DA in the optical disc 1. Thereby, the control unit or the synchronization signal generation circuit 48 can acquire the scanning timing of the synchronization area DA by detecting the special pattern based on the reflected light from the photodetector 31.

  Examples of the pattern include three blank areas (areas where no pits exist) of the information unit 5 set so as not to exist as the information unit 5.

  In the present embodiment, the control photodetector 29 and the photodetector 31 are configured separately. However, the present invention is not limited to this, and the photodetector 31 may have the function of the control photodetector 29. In this case, the focusing / tracking circuit 47 generates a servo signal based on the light reception signal output from the photodetector 31.

  Here, specific examples relating to the manufacture and reproduction of the optical disc 1 shown in FIG. 13 will be described as Examples 5 to 9.

Example 5
The information units 5 having the pit arrangement shown in FIG. 9 (FIG. 13) are regularly arranged at a pitch of 350 nm on the recording area KA of the information track 2 formed in a spiral shape on the optical disc 1.

  Further, the phase pit 4 arranged on the information track 2 and the phase pit 3 arranged at a square apex position centered on the phase pit 4 are injection-molded with respect to the recording surface of the transparent substrate 7 made of polycarbonate. By the method, it was formed into a depression shape with a depth of 40 nm. The diameter of the phase pits 3 and 4 was set to 60 nm, and the formation pitch of the phase pits 3 and 4 was set to 100 nm.

Further, the synchronization unit 61 shown in FIG. 1 is formed on the synchronization area DA of the information track 2. The synchronization units 61 were circular pits each having a width (length in the radial direction) of 160 nm, a length (length in the circumferential direction) of 160 nm, and a depth of 40 nm, and arranged at equal intervals at a pitch of 350 nm.
The synchronization unit 61 is provided in front of 12800 information units 5.

  Patterning of the master for forming the transparent substrate 7 having the information unit 5 (phase pits 3 and 4) and the synchronization unit 61 was performed using an electron beam exposure apparatus.

Here, when the synchronization unit 61 was formed, a relatively large phase pit was formed by reciprocating the focused electron beam in a direction (radial direction) perpendicular to the information track 2. On the other hand, at the time of forming the information unit 5, a relatively small phase pit was formed by irradiating the position where the phase pits 3 and 4 should be formed with a condensable electron beam that can be exposed.
Then, an optical disc stamper was formed from this master, and the transparent substrate 7 was formed by performing injection molding using this stamper.

  Next, the metal reflective film 8 made of aluminum was formed to a thickness of 50 nm on the transparent substrate 7 on which the information unit 5 and the synchronization unit 61 were formed by sputtering. Further, a 0.1 mm thick polycarbonate sheet was bonded to the metal reflective film 8 as a protective film 9 with an ultraviolet curable resin.

  Such an optical disc 1 was mounted on the disc apparatus shown in FIG. 14 and played back. Here, a semiconductor laser element having a wavelength of 405 nm was used as the semiconductor laser light source 21. Further, a lens having a numerical aperture (NA) of 0.85 was used as the condensing lens 24 for condensing the laser light L onto the optical disc 1. Further, the laser beam L was incident from the protective film 9 side of the optical disc 1.

  In reproduction, focusing by the astigmatism method is performed by the control unit, the control photodetector 29, and the focusing / tracking circuit 47 so that the laser light L is condensed on the metal reflection film 8 in accordance with the received light signals R5 to R8. went. Further, the beam spot 6 was tracked along the information track 2 by the push-pull method.

  The synchronization signal S is generated by the synchronization signal generation circuit 48 based on the total signal amount output from the photodetector 31 when passing through the synchronization unit 61. Then, the information unit 5 was reproduced using the generated synchronization signal S.

  The total light quantity comparison circuit 43 and the partial light quantity comparison circuit 44 processed the light reception signals R1 to R4 of the partial light reception surfaces D1 to D4 of the photodetector 31 according to the identification conditions as shown in Table 9. As a result, 32 types (5 bits) of pit arrangements in the information unit 5 can be identified, and 5 bits of data can be demodulated.

  Also, according to the identification method shown in Table 10, the pit arrangement in the information unit 5 can be similarly identified. In this case, at the final identification stage by the total light quantity comparison circuit 43, at most four types of total reflected light quantities are identified. For this reason, the information unit 5 can be easily identified, and information reproduction can be stably realized as compared with the identification method shown in Table 9.

Example 6
Further, in the configuration of the optical disc 1 shown in Example 5, the optical disc 1 having the information unit 5 having the pit arrangement shown in FIG. 18 was formed.
In this configuration, the phase pit 3 is arranged at the apex position of a regular hexagon centered on the phase pit 4, and one of the diagonal lines that bisect the hexagon is arranged so as to overlap the information track 2. . Similarly to Example 5, the diameter of the phase pits 3 and 4 was 60 nm, the formation pitch was 100 nm, and the depth was 40 nm.

  Such an optical disc 1 was mounted on the disc apparatus shown in FIG. 14 in the same manner as in Example 5, and the synchronization signal S was generated by the synchronization signal generation circuit 48, and the information unit 5 was reproduced. As a result, by using a six-divided photodetector as the photodetector 31, the pit arrangement in each information unit 5 can be identified and 7-bit data can be demodulated according to the same procedure as in the fifth embodiment.

Example 7
Further, in the configuration of the optical disc 1 shown in the fifth and sixth embodiments, the optical disc 1 in which the synchronization units 61 are arranged at regular intervals with a pitch of 700 nm was formed.

In this case, the synchronization signal generation circuit 48 generates the synchronization signal S having a period that is half the period of the light reception signal based on the total light reception signal output from the photodetector 31 when passing through the synchronization unit 61. .
As a result of reproducing these optical discs 1 using the generated synchronization signal S, the pit arrangement in each information unit 5 could be identified as in the fifth and sixth embodiments.

Example 8
Further, in the configuration of the optical disc 1 shown in the fifth and sixth embodiments, the optical disc 1 having the synchronization unit 61 shown in FIGS. 19 and 20 was formed. In these optical discs 1, a pit array (having all the phase pits 3 and the phase pits 4) having the same configuration as that of the information unit 5 was formed as the synchronization unit 61.
In addition, the synchronization units 61 are designed to be arranged at equal intervals with a pitch of 350 nm.

  As a result of reproducing these optical discs 1 in the same manner as in the fifth and sixth embodiments, the synchronization signal S can be generated based on the reflected light from the synchronization unit 61, and in each information unit 5 as in the fifth and sixth embodiments. The pit arrangement could be identified.

Example 9
In addition, in the configuration of the optical disc 1 shown in Example 8, the optical disc 1 in which the synchronization units 61 are arranged at equal intervals with a pitch of 700 nm was formed.

  As a result of reproducing these optical discs 1 in the same manner as in the seventh embodiment, the synchronization signal S can be generated based on the reflected light from the synchronization unit 61, and the pit arrangement in each information unit 5 is identified as in the eighth embodiment. did it.

  In addition, the optical memory device of the present invention includes an optical memory in which a recording area KA including a plurality of information units 5 having information corresponding to a pit arrangement and a synchronization area DA used for generating a synchronization signal S are arranged on an information track 2. In the element, the pit arrangement of the information unit 5 in the recording area KA is composed of a combination of a central phase pit 4 disposed on the information track 2 and a peripheral phase pit 3 formed around the central phase pit 4, It can also be expressed that the synchronization area DA has a plurality of synchronization units 61 arranged at equal intervals.

  The present invention also relates to an optical memory element in which information is recorded by phase pits, and an optical memory element reproducing apparatus capable of reproducing at least the information by a light beam. It can also be said that an object of the present invention is to provide an optical disc (optical memory element) having a high recording density that can be reproduced stably and accurately without requiring a complicated reproducing circuit.

Further, in the conventional optical disc, there are recording units (information units) that are asymmetric in the radial direction of the optical disc across the information track. In this case, since the push-pull signal for tracking is disturbed, the tracking is disturbed every time an asymmetric recording unit is passed, and it can be said that this causes an increase in reproduction errors.
Conventionally, in order to realize a higher-density optical disc, the phase pit arrangement method in the information unit is an important issue in order to stably reproduce information from the information unit in which information is recorded. Become.

  In addition, with respect to the photodetector 31, reproduction light detection is arranged such that one of the dividing lines that bisect the six-divided photodetector elements D1 to D6 intersects the straight line XX ′ corresponding to the information track 2 at right angles. It can be said that it is a vessel.

  Conventionally, when reproducing the information unit 100 composed of a plurality of pits 101, when the center of the light beam applied to the information unit 100 substantially coincides with the center of the information unit 100 to be reproduced, the light receiving surfaces D1 to D8 It is possible to determine the pit arrangement based on the light receiving state and read the information. For this reason, it can be said that it is preferable to use a highly accurate synchronization signal during reproduction.

  Further, the control photodetector 29 shown in FIG. 2 may generate a focusing signal by the astigmatism method and a tracking signal by the push-pull method based on the reflected laser light La. . In this case, the focusing / tracking circuit 47 drives the actuator 25 based on the focusing signal and tracking signal generated by the control photodetector 29 to perform focusing and tracking.

  Further, as shown in FIG. 9, when the phase pits 3 are arranged at the rectangular apex positions, it is preferable to set so that one of the diagonal lines of the quadrangle overlaps the information track. This makes it easy to set the pit arrangement to be line symmetrical about the information track. Also, when tracking is controlled by the push-pull method or the like based on the reflected light from the information unit, if the pit arrangement becomes asymmetric in the radial direction, the reflected light intensity from both sides of the information track becomes asymmetric and the push-pull signal is It is disturbed and accurate tracking control cannot be performed (tracking becomes unstable). When the pit arrangement is set in such a line symmetry, it is possible to reliably prevent the push-pull signal disturbance as described above. Accordingly, tracking control of the memory element can be stably realized.

  Further, the symmetry identifier of the pit arrangement shown in FIG. 1 can be described as follows. In other words, the symmetry identifier is an identifier indicating the symmetry between the vertex angle position of a hexagon where two adjacent phase pits are arranged and the vertex angle position symmetric with respect to the center position of the hexagon. For example, as shown in FIG. 7, the symmetry between the apex angle P1 and the apex angle P2 and the apex angle P4 and the apex angle P5 is considered, and there is a phase pit 3 at both the apex angle P1 and the apex angle P2. It is determined that the phase pit 3 exists in both the apex angle P4 and the apex angle P5, and the phase pit 3 exists in one of the apex angle P1 and the apex angle P2, and the apex angle P4 and the apex angle When the phase pit 3 is present on one side of P5, it is determined to be symmetric, and when there is no phase pit 3 at both the apex angle P1 and the apex angle P2, the phase is present at both the apex angle P4 and the apex angle P5. If the pit 3 does not exist, it is determined to be symmetric. The number consisting of 0, 1, 3 of the symmetry identifier indicates how many such symmetry exists in the information unit 5, and is an important identifier for identifying the information unit 5. It becomes.

The optical disc 1 is provided with a plurality of information units along an information track, and the information units are arranged at a phase pit arranged at the center position of the information unit and a hexagonal position with the center position as the center of gravity. The symmetry of the arrangement of the phase pits 3 and 4 in the information unit 5 is identified by arranging so that one of the diagonal lines that bisect the hexagon overlaps the information track. By doing so, the information unit 5 can be easily identified, and 128 types of information (7-bit data) can be multiplexed and recorded in one information unit 5, thereby realizing a large-capacity optical disk. It can be said that it is possible.

  Further, this disk apparatus has one of dividing lines for dividing the light irradiation means for irradiating the information unit 5 of the optical disk 1 with laser light and the six-divided light detection element for detecting the reflected light from the information unit 5. Based on the optical system arranged so as to intersect at right angles with the straight line corresponding to the information track, and the light detection signal of the six-divided light detection element, the information unit 5 is identified and the recorded information is reproduced. Means. In the present invention, the information unit 5 is easily identified by arranging the six-divided photodetecting elements as described above and comparing the photodetection signals of the respective detecting elements using a simple comparison circuit. be able to.

  Here, as an arrangement method of the six-divided photodetecting elements, a configuration has been described in which one of the dividing lines that bisect the six-divided photodetecting elements is arranged so as to intersect with a straight line corresponding to the information track. Even when one of the dividing lines is arranged so as to coincide with a straight line corresponding to the information track, the information unit 5 can be identified by the same identification process. However, when the dividing line is arranged so as to coincide with the straight line corresponding to the information track, the dividing line exists at a position corresponding to the phase pit. In this case, there is a dividing line at a position corresponding to the phase pit where the change in the light intensity is the largest, and the detection accuracy is deteriorated when detecting the light intensity distribution on the light detection element. . Therefore, in order to perform more accurate reproduction light detection, one of the dividing lines that bisect the six-divided light detecting element is arranged so as to intersect at right angles with a straight line corresponding to the information track. Is desirable.

  Further, the information unit 5 is identified based on the output of each photodetection element using a 12-divided photodetection element in which the number of divisions of the light receiving surface of the reproducing photodetector 31 is 12 times. However, as shown in the present invention, the calculation process when identifying the information unit 5 is simplified by using the six-divided photodetector, and the identification unit 5 can be identified by a simpler comparison circuit. Thus, the cost of the playback device can be reduced.

The present invention also relates to an optical memory element in which information is recorded by phase pits 3 and 4 and an optical memory element reproducing apparatus capable of reproducing at least the information by a light beam.
Conventionally, when reproducing the information unit 5 composed of a plurality of pits, when the center of the light beam applied to the information unit 5 substantially coincides with the center of the information unit 5 to be reproduced, the pit arrangement is determined, Information can be read. Therefore, a high-accuracy synchronization signal S is required during reproduction. In order to realize a higher-density optical disc, the phase pit arrangement method in the information unit is an important issue in order to stably reproduce information from the information unit in which the information is recorded.

  Moreover, FIG. 13 can also be described as follows. That is, in the example shown in this figure, a plurality of phase pits 3 arranged at equidistant positions from the center position are arranged at regular square positions with the center position as the center of gravity, and the diagonal of the regular square A configuration is shown in which one is arranged so as to overlap the information track 2. Further, a plurality of synchronization units 61 provided at equal intervals are provided on the information track 2 at a position preceding the recording area KA in which the information unit 5 of the information track 2 is formed. In FIG. 13, the synchronization unit 61 constituted by phase pits larger than the phase pits 3 and 4 constituting the information unit 5 is illustrated.

  In the disk apparatus shown in FIG. 14, the photodetector 31 receives the reflected light from the information unit 5, and detects the reflected light intensity distribution on each of the light detection elements (partial light receiving surfaces) D1 to D4. It can be said that the information unit 5 is identified using the signal strengths of the output signals (light reception signals) R1 to R4 from the respective light detection elements.

  In addition, the optical disk 1 having the configuration shown in FIG. 13 is arranged at a central position of a regular square, with a plurality of phase pits 3 arranged at the apex position of a regular square, one of the diagonal lines of which is on the information track 2. The information units 5 constituted by the phase pits 4 are regularly arranged on the information track 2 formed in a spiral shape, whereby 32 types of information (5-bit data) are stored in one information unit 5. Thus, it can be said that a large-capacity optical disk can be realized. Further, in the present disk apparatus shown in FIG. 14, the light irradiating means for irradiating the information unit 5 of the optical disk 1 with laser light, the reflected light from the information unit 5 and its dividing line correspond to the information track 2. An optical system configured to be incident on a reproducing photodetector (photodetector 31) including a four-divided photodetecting element arranged to form an angle of 45 ° with the straight line XX ′. It can be said that the information unit 5 is identified on the basis of the light detection signal of the split light detection element, and the recording information is reproduced. In the present disk device, the information unit 5 can be easily identified by arranging the four-part photodetecting elements as described above, and comparing the photodetection signals of the respective detecting elements using a simple comparison circuit. It can be carried out.

  Moreover, regarding Table 10, it can also be described as follows. That is, the partial light quantity comparison circuit 44 is a circuit that performs symmetry discrimination I, symmetry discrimination II, and symmetry discrimination III. In the symmetry discrimination I, the magnitude relationship between T1 and T2 is compared to determine the symmetry discrimination. In II, the magnitude relation between S1 and S3 is compared, and in magnitude symmetry III, the magnitude relation between S2 and S4 is compared. As a result of the comparison, the total reflected light amount is identified by the total light amount comparison circuit 43 for the information units 5 classified into the small groups, and the identification of the individual information units 5 is completed. In this case, the total amount of reflected light to be identified in each small group is two types or four types. In the identification method shown in Table 9, it is necessary to first identify 10 types of total reflected light amounts from a to j, and a highly accurate comparison circuit is necessary. Further, although the total reflected light amount changes due to a slight change in the laser light amount, it becomes difficult to identify the information unit 5. However, according to the identification method shown in Table 10, the total reflected light amount to be compared is reduced. The information unit 5 can be identified by a comparatively simple comparison circuit, the cost of the reproduction apparatus can be reduced, and the reproduction apparatus capable of accurately identifying the information unit 5 even when the laser light quantity change occurs. Can be provided.

Further, the generation of the synchronization signal S in the present disk device shown in FIG. 14 can be described as follows. That is, the generation of the synchronization signal S is performed using a plurality of synchronization units 61. The synchronization unit 61 is arranged on the information track 2 at equal intervals, and the light beam spot 6 detects the state of the reflected light when passing through the synchronization unit 61 by the photodetector 31, thereby synchronizing signal. Is generated. FIG. 16 shows a signal change of (R1 + R2 + R3 + R4) when the light beam spot 6 moves on the information track 2. Here, DT is the signal amplitude of the total signal amount obtained when passing through the synchronization unit 61. Here, the synchronization signal generation circuit 48 includes a binarization circuit, a phase comparator, an LPF, and a VCO, and is based on the total signal amount output from the photodetector 31 when passing through the synchronization unit 61. The synchronization signal S can be generated.
Further, it can be said that the synchronization unit 61 shown in FIGS. 19 and 20 is composed of a plurality of phase pits arranged at specific positions.

  Usually, the synchronization unit 61 is provided in a specific area in the disc. As described in Patent Document 2, the circumference of the information track provided in a spiral shape is further divided into fine sectors to provide sectors having recording information unit rows, and a synchronization unit 61 is provided at the head position of each sector. It is done. The synchronization unit 61 generates a synchronization signal S, and the information unit 5 is reproduced accurately. In general, focusing is always performed. At this time, the focus servo is disturbed due to signal mixing into the focus servo signal from the phase pit constituting the recording information unit, but by removing the high-frequency signal component corresponding to the phase pit through the low-pass filter, Stable focusing can be performed. In general, tracking is always performed, but for tracking, the tracking signal is obtained only at the position of the synchronization unit 61, and the position of the condenser lens is fixed at the position of the information unit 5 to reproduce information. It is also possible.

  Further, in order to distinguish the reflected light from the synchronization unit 61 and the reflected light from the phase pits of the information unit 5, a pattern that does not exist as a recording information unit row is arranged in front of the synchronization unit 61. 61 can be recognized. For example, by providing three blank areas (areas where pits do not exist) of information units 5 set so as not to exist as recording information unit columns, the synchronization unit 61 exists following this blank area. Can be confirmed.

  In the optical reproducing apparatus according to the present invention, the information unit of the memory element is irradiated with light, and information is reproduced based on the reflected light. The optical reproducing apparatus receives reflected light from the information unit and the synchronization unit. A photodetector that outputs a light reception signal corresponding to the amount of received light, a pit arrangement specifying circuit that specifies the pit arrangement of the information unit for reproduction based on the light reception signal from the information unit, and a light reception signal from the synchronization unit Based on this, it can also be expressed as a configuration including a synchronization signal generation circuit that generates a synchronization signal for information unit reproduction.

The present invention can also be expressed as the following first to thirteenth optical memory elements and first to seventh optical memory element reproducing devices. That is,
The first optical memory element is an optical memory element in which a plurality of information units are provided along an information track, wherein the information unit is positioned equidistant from the phase pit arranged at the center position of the information unit. And a plurality of phase pits. According to the first optical memory element, the phase pits constituting the information unit are arranged at the center position of the information unit and the equidistant position from the center position, and are substantially circularly shaped and irradiated for reproduction. In this light beam spot, a plurality of phase pits can be efficiently arranged, and both stable reproduction and large capacity can be realized.

  In the first optical memory element, the second optical memory element includes a plurality of phase pits arranged at equidistant positions from the center position in the information unit, arranged at hexagonal positions with the center position as the center of gravity, and One of the diagonal lines that bisect the hexagon is arranged so as to overlap the information track. According to the second optical memory element, the plurality of phase pits arranged at equidistant positions from the center position are arranged at hexagonal positions with the center position as the center of gravity, thereby irradiating light for reproduction. In the beam spot, a plurality of phase pits are arranged in a close-packed state, the information multiplicity of one information unit is maximized, and the capacity of the optical memory element is increased.

  The third optical memory element includes a specific phase pit arrangement pattern selected from all arrangement patterns determined by the presence or absence of the phase pit in the first optical memory element. It is the structure which is done. According to the third optical memory element, the phase pit arrangement pattern is composed of a specific phase pit arrangement pattern selected by an appropriate selection unit, so that the information unit by the total reflected light amount comparison in the reproduction photodetector is obtained. Identification and identification of information units by comparison of light intensity distribution on the reproduction photodetector, the identification unit can be identified by a simpler comparison means, and the identification accuracy can be improved and the comparison can be made. Simplification of the circuit, that is, cost reduction of the optical memory element is realized.

  The fourth optical memory element has a configuration in which, in the third optical memory element, the arrangement pattern is selected based on the total reflected light amount of the light beam condensed and irradiated on the information unit. According to the fourth optical memory element, the array pattern is configured by an array pattern selected based on the total reflected light amount, and information having substantially the same total reflected light amount is not used because an information unit having a specific total reflected light amount is not used. The number of unit groups can be reduced, and the difference in total reflected light amount between groups of information units having substantially the same total reflected light amount can be increased. Therefore, it is possible to perform highly accurate identification using a simpler total reflected light amount comparison circuit.

  The fifth optical memory element has a configuration in which, in the third optical memory element, the arrangement pattern is selected based on the symmetry of the arrangement pattern. According to the fifth optical memory element, the array pattern is constituted by an array pattern selected based on the symmetry of the array pattern, and the symmetry of the array pattern, that is, the light intensity distribution on the reproducing photodetector. By determining the magnitude relationship, it becomes possible to identify information units. Therefore, the information unit can be accurately identified by a simple comparison circuit that can determine only the magnitude relationship.

  The first optical memory element reproducing device is an optical disk reproducing device for reproducing recorded information from the first to fifth optical memory elements, and a light irradiating means for irradiating a recording unit of the optical memory element with reproducing light, and from the recording unit In an optical memory element reproducing apparatus having an optical system for guiding reflected light to a reproducing photodetector, the reproducing detector is composed of a photodetector element divided into a plurality of regions, and each light of the photodetector element The information unit is identified based on the detection signal, and the information is reproduced. According to the first optical memory element reproducing device, the optical memory element is irradiated with reproducing light, and the reflected light is incident on the light detecting element divided into a plurality of regions, and based on the individual light detection signals of the light detecting element. By identifying the information unit, it is possible to identify the information unit in which a plurality of pieces of information are recorded in a multiplexed manner, and to reproduce the information recorded in the optical memory element.

  The second optical memory element reproducing device according to the first optical memory element reproducing device, wherein the optical system includes a control photodetector for obtaining a focusing signal and a tracking signal separately from the reproducing photodetector. The configuration is such that the reflected light from the unit is separated into reflected light applied to the reproducing detector and reflected light applied to the control photodetector. According to the second optical memory element reproducing device, by providing the control photodetector separately from the reproducing photodetector, an appropriate reflected light is emitted to the photodetector elements divided into the plurality of regions of the reproducing detector. Therefore, it is possible to provide an optical memory device that suppresses the occurrence of errors when specifying information units and has few reproduction errors. The reflected light applied to the control photodetector is irradiated through a cylindrical lens for focusing. In this case, the wavefront of the reflected light applied to the control photodetector is disturbed. Therefore, when the reproducing photodetector and the control photodetector are shared, the reproducing photodetector is also irradiated with reflected light having a distorted wave front through the cylindrical lens. Disturbance occurs in the light intensity distribution on the photodetector, and the information unit cannot be specified accurately. By separating the reproducing photodetector from the controlling photodetector, there is no disturbance in the light intensity distribution on the reproducing photodetector, and an accurate information unit can be specified.

  The third optical memory element reproducing device is configured such that in the first optical memory element reproducing device, the reproducing detector is a six-divided photodetecting element. According to the third optical memory element reproducing device, by making the reproducing detector into six-divided photodetector elements, the determination process necessary for specifying the information unit is simplified, and the total incident light to the reproducing photodetector is made. It is possible to simplify the circuit configuration for comparing the signals and the circuit configuration for comparing the light amounts of the respective photodetectors of the reproducing photodetector, and the specific time of the information unit can be shortened. At the same time, the cost of the optical memory element reproducing apparatus can be reduced by reducing the circuit scale.

  The fourth optical memory element reproducing device has a configuration in which, in the third optical memory element reproducing device, one of the dividing lines that bisect the six-divided photodetector element intersects with a straight line corresponding to the information track. . According to the fourth optical memory element reproducing device, one of the dividing lines that bisect the six-divided photodetecting element is arranged so as to intersect at right angles with the straight line corresponding to the information track, thereby the position corresponding to the phase pit. In addition, since there is no dividing line, it is possible to more accurately detect the light intensity distribution on the reproducing photodetector due to the presence or absence of the phase pit, and the accuracy of identification of the total reflected light amount and the individual detection elements Comparison accuracy of incident light intensity is increased. As a result, information unit detection errors can be suppressed.

  In the fifth optical memory element reproducing device, in the first optical memory element reproducing device, the means for identifying the information unit compares a total signal obtained by adding the photodetection signals of the plurality of photodetecting elements, and After the division, the information unit is identified by comparing the magnitudes of the light detection signals from the plurality of light detection elements. According to the fifth optical memory element reproducing device, the total signals obtained by adding the photodetection signals of the plurality of photodetection elements are compared, the information units are grouped, and then the light from the plurality of photodetection elements is compared. By comparing the magnitudes of the detection signals, it is possible to provide an optical memory element reproducing apparatus capable of identifying the information unit according to the present invention and reproducing the recorded information.

In addition, the sixth optical memory element is an optical memory element in which information units composed of a plurality of phase pits arranged at specific positions are arranged at equal intervals along the information track. In this configuration, a plurality of synchronization units arranged in the above are provided. Thereby, it is possible to generate a synchronization signal for the information track by the reflected light from the synchronization unit. Therefore, a stable synchronization signal can always be obtained, and the information unit can be accurately identified by using this synchronization signal.

  The seventh optical memory element is the sixth optical memory element, wherein the information unit is composed of a phase pit arranged at the center position of the information unit and a plurality of phase pits arranged at equidistant positions from the center position. It is a configuration. Thereby, in addition to being able to realize accurate identification of the information unit, the phase pits constituting the information unit are arranged at the center position of the information unit and the equidistant position from the center position, It is possible to efficiently arrange multiple phase pits within a roughly circular light beam spot that is focused and irradiated for reproduction, and to realize both stable reproduction and large capacity of information units. Can do.

  The eighth optical memory element is the seventh optical memory element, wherein in the information unit, a plurality of phase pits arranged at equidistant positions from the center position are arranged at a rectangular position with the center position as the center of gravity, and In this configuration, one of the diagonal lines of the rectangle is arranged so as to overlap the information track. As a result, accurate identification of information units can be realized, and a plurality of phase pits arranged at equidistant positions from the center position are arranged at rectangular positions with the center position as the center of gravity. As a result, a plurality of phase pits are arranged in the light beam spot irradiated for reproduction, the information multiplicity of one information unit is maximized, and the capacity of the optical memory device is increased. .

  The ninth optical memory element is the seventh optical memory element, wherein in the information unit, a plurality of phase pits arranged at equidistant positions from the center position are arranged at hexagonal positions with the center position as the center of gravity, and The diagonal line that bisects the hexagon is arranged so as to overlap the information track. Thereby, in addition to realizing accurate identification of information units, a plurality of phase pits arranged at equidistant positions from the center position are arranged at hexagonal positions with the center position as the center of gravity. As a result, a plurality of phase pits are arranged in a close-packed state within the light beam spot irradiated for reproduction, and the multiplicity of information of one information unit is maximized, which increases the size of the optical memory device. Capacitance is realized.

  The 10th optical memory element reproducing | regenerating apparatus is a structure in which the said synchronous unit is a several phase pit arranged at equal intervals larger than the phase pit which comprises an information unit in a 6th optical memory element. Thereby, the state change of the reflected light from the synchronization unit becomes large, and it becomes possible to realize more accurate identification of the information unit.

  The eleventh optical memory element is the sixth optical memory element, wherein the synchronization unit is composed of a plurality of phase pits arranged at specific positions. This makes it possible to use phase pits having the same shape for the phase pits constituting the synchronization unit and the phase pits constituting the information unit. In this case, when forming an optical memory element master, both can be formed under the same conditions, and the control conditions for forming the optical memory element master can be reduced. Therefore, it becomes possible to form an optical memory element master and an optical memory element more stably.

  The twelfth optical memory element is the same as the eleventh optical memory element, in which the phase pits forming the synchronization unit are the same synchronization units arranged at the same positions as the phase pits forming the information unit. As a result, when forming the master for the optical memory element, both can be formed under the same conditions, and the control conditions for forming the master for the optical memory element can be reduced. Therefore, it becomes possible to form an optical memory element master and an optical memory element more stably.

  The thirteenth optical memory element is configured such that, in the twelfth optical memory element, the synchronization unit has phase pits arranged at all phase pit arrangement positions of the information unit. Thereby, in addition to the above effects, the state change of the reflected light from the synchronization unit is increased, and it becomes possible to realize more accurate identification of the information unit.

  The sixth optical memory element reproducing device is an optical disk reproducing device that reproduces recorded information from any of the sixth to thirteenth optical memory elements, the light irradiating means for irradiating the information unit of the optical memory element with the reproducing light, and the information unit An optical memory element reproducing apparatus having an optical system for guiding reflected light from a reproducing light detector to a reproducing light detector, wherein the reproducing detector is composed of a light detecting element divided into a plurality of regions, and each of the light detecting elements The information unit is identified on the basis of the photodetection signal, and means for reproducing the information is provided. Thereby, the individual information units are identified by the state of the reflected light incident on the light detection element divided into a plurality of regions, and the recorded information can be stably reproduced from the optical memory element of the present invention. An optical memory element reproducing device can be provided.

  The seventh optical memory element reproducing device is an optical disk reproducing device for reproducing recorded information from the optical memory element, and is configured to generate a synchronization signal based on the reflected light from the synchronization unit. Thus, the optical memory element reproducing apparatus of the present invention is provided, which can generate a synchronizing signal based on the reflected light from the synchronizing unit, and can more accurately reproduce the recorded information from the optical memory element of the present invention. It becomes possible.

  The present invention can be suitably used for optical discs such as DVDs and CDs, and optical disc apparatuses that reproduce optical discs.

It is explanatory drawing which shows the kind (information type) of the pit arrangement | sequence of an information unit formed in the optical disk concerning one Embodiment of this invention. It is explanatory drawing which shows the structure of the optical disk apparatus concerning one Embodiment of this invention. It is a top view of an above-mentioned optical disk. It is sectional drawing of the optical disk shown in FIG. It is explanatory drawing which shows the information unit formed in the optical disk shown in FIG. It is explanatory drawing which shows the kind (pit type of information) of the pit arrangement | sequence of an information unit formed in the optical disk shown in FIG. It is explanatory drawing which shows the formation position of the phase pit in the information unit of the optical disk shown in FIG. It is explanatory drawing which shows the structure of the photodetector with which the optical disk apparatus shown in FIG. 2 was equipped. It is explanatory drawing which shows the kind (information type) of the other pit arrangement | sequence in an information unit formed in the optical disk shown in FIG. It is explanatory drawing which shows the other structure of the photodetector with which the optical disk apparatus shown in FIG. 2 is equipped. FIG. 3 is an explanatory diagram showing a configuration of a control photodetector provided in the optical disc apparatus shown in FIG. 2. It is explanatory drawing which shows the other information unit formed in the optical disk shown in FIG. It is explanatory drawing which shows the information unit and synchronization unit which are formed in the optical disk shown in FIG. It is explanatory drawing which shows the other structure of the optical disk apparatus concerning one Embodiment of this invention. FIG. 15 is an explanatory diagram illustrating a configuration of a synchronization signal generation circuit provided in the optical disc apparatus illustrated in FIG. 14. It is a graph which shows the sum (R1 + R2 + R3 + R4; total light reception signal) of all the light reception signals output from a photodetector when a beam spot scans (moves) on the information track of the optical disk shown in FIG. It is explanatory drawing which shows the phase shift of the received light signal which generate | occur | produces when reproducing | regenerating the information unit of an optical disk. It is explanatory drawing which shows the kind (information type) of the other pit arrangement | sequence in an information unit formed in the optical disk shown in FIG. It is explanatory drawing which shows the other structure of the synchronous unit formed in the optical disk shown in FIG. It is explanatory drawing which shows the other structure of the synchronous unit formed in the optical disk shown in FIG. It is explanatory drawing which shows the pit arrangement | sequence of the information unit formed in the conventional optical disk. It is explanatory drawing which shows the structure of the photodetector with which the conventional optical disk apparatus is equipped.

Explanation of symbols

1 Optical disk (optical memory device)
2 Information track 3 Phase pit (Ambient phase pit)
4 Phase pit (center phase pit)
5 Information unit 6 Beam spot 7 Transparent substrate 8 Metal reflecting surface 9 Protective film 10 Spindle 11 Optical pickup 12 Circuit board 21 Semiconductor laser light source 22 Collimator lens 23 Beam splitter 24 Condensing lens 25 Actuator 26 Beam splitter 27 Condensing lens 28 Cylindrical lens 29 control light detector 30 condensing lens 31 light detector 41 spindle control circuit 42 laser control circuit 43 total light quantity comparison circuit (pit arrangement specifying circuit)
44 Partial light quantity comparison circuit (pit array identification circuit)
45 Demodulation circuit 46 Error correction circuit 47 Focusing / tracking circuit (light control circuit)
48 Sync signal generation circuit 51 Symmetry determination circuit (pit arrangement specifying circuit)
61 Synchronizing unit 71 Binary circuit 72 Phase comparator 73 Low pass filter (LPF)
74 Voltage Controlled Oscillator (VCO)
D1 to D6 Partial light receiving surfaces H1 to H6 Hexagonal side L Laser light La Reflected laser light P1 to P6 Apex angle R1 to R6 Light receiving signal S Sync signal S1 Reference value a to i Light quantity identifier 1a3 to 128i3 Pit array 1ax to 32jx Pit Array

Claims (21)

In the optical memory element in which a plurality of information units having information corresponding to the pit arrangement is arranged along the information track,
The pit arrangement of the information unit is
Composed of a combination of a central phase pit arranged on the information track and a peripheral phase pit formed around this central phase pit,
A plurality of synchronization units having the same shape are provided at equal intervals on the information track ,
The optical memory element, wherein the synchronization unit is composed of a set of a plurality of patterns, and the pattern of the synchronization unit is a phase pit similar to that of the information unit .   2. The optical memory device according to claim 1, wherein the surrounding phase pits are located at an equal distance from the central phase pit.   3. The optical memory element according to claim 2, wherein the peripheral phase pits are arranged at a vertex angle position of a hexagon centered on the central phase pit.   4. The optical memory element according to claim 3, wherein one of the diagonal lines passing through the center of the hexagon overlaps the information track.   4. The optical memory element according to claim 3, wherein only one having an odd number of surrounding phase pits or only one having an even number of surrounding phase pits is used as the pit arrangement of the information unit.   4. The optical memory device according to claim 3, wherein the pit arrangement of the information unit is axisymmetric with respect to one of diagonal lines passing through the center of the hexagon.   2. The optical memory device according to claim 1, wherein the pit arrangement of the information unit is axisymmetric about the information track.   2. The optical memory device according to claim 1, wherein the information track is an optical disk formed in a spiral shape or a concentric shape.   2. The optical memory element according to claim 1, wherein the peripheral phase pits are arranged at quadrangle apex positions centering on the central phase pit.   10. The optical memory device according to claim 9, wherein one diagonal line in the quadrangle overlaps with the information track. 2. The optical memory device according to claim 1 , wherein the synchronization unit is composed of all surrounding phase pits and a central phase pit.   2. The optical memory element according to claim 1, wherein the synchronization unit is formed at the same pitch as the information unit formation pitch in the direction in which the information track extends.   2. The optical memory device according to claim 1, wherein the synchronization unit is formed at a pitch twice as large as a formation pitch of the information units in the direction in which the information track extends. In the optical reproducing device which irradiates light to the information unit of the optical memory element according to claim 3 and reproduces information based on the reflected light,
A reproducing photodetector that receives reflected light from the information unit and outputs a received light signal corresponding to the amount of received light;
An optical reproducing apparatus comprising: a pit arrangement specifying circuit for specifying a pit arrangement of an information unit related to reproduction based on a light reception signal output from a reproduction photodetector. A control photodetector separate from the reproducing photodetector, which receives reflected light from the information unit in the optical memory element and outputs a received light signal corresponding to the amount of received light;
The optical reproducing apparatus according to claim 14 , further comprising: an optical control circuit that controls light applied to the optical memory element based on a light reception signal output from the control photodetector. Said photodetector has six parts receiving surface which is formed by 6 divides the light receiving surface by three division lines, characterized in that it is composed of 6-divided photodetector, claim 14 An optical regenerator described in 1. The three dividing lines that divide the light receiving surface of the reproducing photodetector described above are arranged so as to be shifted from each other by 60 degrees, and one of these dividing lines is one diagonal line of the hexagon on the light receiving surface. 17. The optical regenerator according to claim 16 , wherein the optical regenerator is orthogonal to a straight line corresponding to. The above pit arrangement specifying circuit is
A total light amount comparison circuit for specifying a total reflected light amount that is a total amount of light reflected by the information unit based on light reception signals output from all partial light receiving surfaces;
Using the light reception signal output from each partial light receiving surface, the size of the light incident on each partial light receiving surface is compared, and a partial light quantity comparison circuit that identifies the pit arrangement of the information unit is provided.
17. The optical reproducing apparatus according to claim 16 , wherein the partial light quantity comparison circuit is designed to determine the content of the comparison based on the total reflected light quantity. In the optical reproducing apparatus is irradiated with light, to reproduce the information based on the reflected light to the optical memory device according to any one of claims 1,9～ 11,
A photodetector that receives reflected light from the information unit and the synchronization unit and outputs a received light signal corresponding to the amount of received light;
Based on the light reception signal from the information unit, a pit arrangement specifying circuit for specifying the pit arrangement of the information unit related to reproduction,
A synchronization signal generation circuit that generates a synchronization signal to be output to the pit arrangement specifying circuit based on the light reception signal from the synchronization unit;
An optical reproducing apparatus, wherein the pit arrangement specifying circuit is designed to specify a pit arrangement of an information unit related to reproduction by using this synchronization signal. The synchronization unit of the optical memory element is formed at the same pitch as the formation pitch of the information units in the direction in which the information track extends,
20. The optical regenerator according to claim 19 , wherein the synchronization signal generation circuit is designed to generate a synchronization signal having the same cycle as the light reception signal from the synchronization unit. The synchronization unit of the optical memory element is formed at a pitch twice the formation pitch of the information units in the direction in which the information track extends,
20. The optical regenerator according to claim 19 , wherein the synchronization signal generation circuit is designed to generate a synchronization signal having a period half that of the light reception signal from the synchronization unit.

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