BRPI0717000A2 - OPTICAL HEAD AND DIFFERENT ELEMENT DEVICE, OPTICAL INFORMATION DEVICE, COMPUTER, DISC PLAYER, CAR NAVIGATION SYSTEM, OPTICAL DISC RECORDER AND VEHICLE - Google Patents

Description

Report of the Invention Patent for "OPTICAL HEAD DEVICE AND DIFFRACTIVE ELEMENT, OPTICAL INFORMATION DEVICES, COMPUTER, DISC PLAYER, CAR NAVIGATION SYSTEM, OPTICAL DISK RECORDER 5 AND VEHICLE".

TECHNICAL AREA

The present invention relates to an optical information apparatus for reproducing information from an information recording medium represented by optical discs, or recording information on the information recording medium; an optical head device for reproducing or recording information in the optical intelligence apparatus; and information equipment and system that uses the same. The present invention also relates to a diffractive element used therein.

TECHNICAL BACKGROUND How a versatile digital disc (DVD) can record information

digital media at a recording density of about six times the compact disc (CD), DVD is known as an optical disc that can record a large amount of data. Recently, larger volume optical discs are desirable, with increasing amount of information being written to the optical disc. In order to obtain a large volume optical disc, the information recording density needs to be increased by reducing the optical point formed by the radiated light on the optical disc when recording information on the optical disc and playing back information recorded on the optical disc. Specifically, the optical point can be reduced by having the light source laser light reduced by keeping the light source laser light at a short wavelength and increasing the numerical apertures (NA) of an objective lens. The wavelength of 660 nm (red) is used for the wavelength of the light source, and the objective lens is used with a numerical aperture (NA) of 0.6. In addition, in BD, a 405 nm wavelength light source is used, and the objective lens is used with an NA of 0.85 in order to obtain a recording density of five times the recording density of the Current DVD In the optical information apparatus for performing high density recording and playback using the blue laser short wavelength laser, the utility of the device is further enhanced by providing a compatibility function with an existing optical disc, and also the performance of cost is increased.

DVD-R with a track slope degree of 0.74 μηι and DVDRAM to perform both full-space (L) and groove (G) recording at 1.3 μΓη coexist on the DVD using red light source. Therefore, it is important to perform stable track control on the optical disc of different 10 degree track inclination, even for DVD devices, and CD and BD compatibility is also desirable.

To perform track control, the amount of track change needs to be detected and the alignment error signal is a push-pull differential (DPP) method. The push-pull differential method is described in patent document 1 (Japanese Published Patent No. 7-272303), and is briefly described using the figure.

Figure 19 shows a configuration of an optical head device according to the prior art. The radiated light beam 210 from a light source 201 is transmitted through a diffraction grating 204. The diffraction grating 204 produces a conjugated diffracted light. The transmitted main radius and the diffracted sub-ray are converted to parallel light by a collimating lens 203. An objective lens 205 converges the main ray and pair of parallel light rays to a recording surface of the optical disc. 227. The light reflected from the optical disc follows the same optical path in the opposite direction and enters a light detector 266. The objective lens is moved in the alignment direction based on the alignment error signal obtained from the light detector 266. , to perform track control.

The diffraction grating configuration used in FIG. 19 is shown in frame view in FIGS. 20A and 20B. Figure 20A is a front view and Figure 20B is a cross-sectional view. The diffraction grating 204 is obtained by periodically forming concave-convex portions on a surface of a transparent base material, such as glass, as shown in Figure 20B. For simplicity, only the centerline of a convex portion is shown in the front view of figure 20A. In the present application, unless specifically indicated, only the centerline of the convex part is shown in other figures, for simplicity, when the concave-convex shape is shown in front view. When the light ray is transmitted through a diffraction grating 204, a diffracted ± one-dimensional, conjugated light is generated and converged on the recording surface of the optical disc 227 as the main beam 211 and a pair of sub-rays 212, 213 by the lens. 205, as shown in Figure 21. The recordable optical disc, such as DVD-RAM, has concave concave grooves on the recording surface thereof. The concave-convex is designated as full space (L) and groove (G). The diffraction grating 204 is rotationally adjusted, as shown by the arrow in Fig. 20A, so that when the main radius 211 converges on a given juice, the sub15 radii 212, 213 converge on the adjacent full spaces. When the push-pull signal generated by the disc groove diffraction is detected by the main radius and the reflected and retransmitted sub-rays of the disc, the positive and negative push-pull signals become opposite to the main radius and for the lightning rods. The alignment error signal of the push-pull method 20 is detected by differential calculation of the push-pull signal of the lightning bolts and the push-pull signal of the main radius. In this method, the distance in the alignment direction (T) of the main radius and the subbeams must be equal to the distance between the centers of the full space and the groove, ie half the slope of the track, and thus , the amplitude of the alignment error signal 25 is reduced when applied to the optical disc with different track tilt degrees, such as DVD-RAM and DVD-R, to become a problem.

The diffraction grating developed to overcome this problem is shown in Figure 22A (patent document 2: Japanese Published Patent Publication No. 9-81942). As shown in Fig. 22A, the diffraction grating 224 is halved by a dividing line parallel to the Y-groove direction. Assuming that the grating phase of the first diffraction grating region 2241 on the left side of the figure is reference (0 degree), the grid phase of the second diffraction grating region 2242 on the right side of the figure is 180 degrees. A change of the network phase in direction T is assumed to be positive. At this point, the sub rays are divided symmetrically in half, as shown in figure 22B. The sub-rays 222 and 5 223 are arranged in the same groove as the main radius 221. In this case, the push-pull signals obtained by the sub-rays 222 and 223 have signals opposite the main radius 221. Therefore, the error signal of Push-pull signal method alignment is detected by the differential calculation of the push-pull signal of the lightning bolts and the push-pull signal of the main radius. In this method, a provision is made so that the distance in the alignment direction (T) of the main radius and the subbeams is 0, and thus the amplitude of the alignment error signal is not reduced by the difference in the disks, even when applied to optical discs with different track tilt degrees, such as DVD-RAM and DVD-R. But there is the problem that when the objective lens 15 moves in the T (T) alignment direction by track tracking, the amplitude of the destination alignment error signal decreases.

In addition, a method configured to prevent reduction in the amplitude of the alignment error signal by the objective lens movement is described in patent document 3 (Japanese Patent Publication No. 2000-145915) and patent document 4 (Patent Publication Published Japanese No. 2006-4499). As shown in Fig. 23A, a third 90 degree phase network region 2343 is disposed between the first 0 degree phase diffraction network 2341 and the second diffraction network region 2342 with a 90 degree phase. 180 degree phase. Signal amplitude in a state in which the objective lens is not moved by track accompaniment is decreased in advance, and reduction in the alignment error signal amplitude in a state in which the objective lens is moved is avoided. relatively, with a different region in between.

Patent Document 1: Japanese Published Patent Publication No. H7-272303

Patent Document 2: Japanese Published Patent Publication No. H9-081942 Patent Document 3: Japanese Published Patent Publication No. 2000-145915

Patent Document 4: Japanese Published Patent Publication No. 2006-4499 Patent Document 5: International Published Publication No.

WO 2004/094/097815 (brochure)

Patent Document 6: Japanese Published Patent Publication No. H7-098431 DESCRIPTION OF THE INVENTION Problem to Be Solved by the Invention

But in the diffraction grating shown in figure 23A, the phase is shifted into a 0 degree, 90 degree, and 180 degree graduation form, in order on the left side of the figure. The diagonal diffraction grating shown with a double current dashed line in figure 24 becomes the main component 15, and the sub-rays have uneven left-right intensity as shown in figure 23B. As shown in Fig. 24B, the positional relationship of the part where the sub radius intensity is strong and the track juice needs to be optimally adjusted in order to maximize the DPP signal. That is, similar to the method using the diffraction grating shown in FIGS. 20A and 20B, there is the problem that the optimum adjustment position (angle of rotation) of the diffraction grating differs depending on the degree of slope of the track. degree of optical tilt, and a stable alignment error signal becomes difficult to obtain.

Therefore, at the present time, there is no proposed method 25 that satisfies both the alignment error signal obtainment by an optimal DPP method with respect to optical discs with different track slope grades using a single diffraction grating, how to suppress reducing the amount of alignment error signal amplitude in a state in which the objective lens is moved by track accompaniment.

In order to solve the above problems, it is an object of the

The present invention provides an optical head device and a diffraction grating capable of obtaining the alignment error signal by the optimal DPP method with respect to optical discs of varying track inclination using a single diffractive element and suppressing reducing the amount of alignment error signal amplitude in a state in which the objective lens is moved by track accompaniment; an optical information apparatus; a computer; a disc player; a car navigation system; an optical disc recorder; and a vehicle. Means to Solve the Problem

In order to achieve the above objectives, the present invention has the following configurations. The first aspect of the present invention provides an optical head device comprising a light source, a diffractive element for branching a light output of the light source into at least three light streams, including a main beam, which is transmitted. non-diffracted and two diffracted sub-rays, an objective lens for converging the three light streams onto a recording surface of an optical disc, and a light detector for receiving the converged light on the recording surface of the disc. optical by the objective lens and reflected by the optical disc and photoelectric device, converting the Iuz into an electrical signal; being that

the diffractive element is divided into a first diffraction grating region 20, a second diffraction grating region formed with a second diffraction grating, with a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first diffraction grating region, and a central region nested between the first diffraction grating region and the second diffraction grating region;

the central region is further divided into a plurality of regions

divided by a virtual dividing line; and

the central region has different grid phases or vectors than the first diffraction grating region and the second diffraction grating region, and the regions divided by the dividing line are formed with phase diffraction grids and different grating vectors.

The second aspect of the present invention provides the optical head device of the first aspect, wherein the dividing line for dividing the central region extends in an orthogonal direction to an extension direction of a track groove of the optical disc.

The third aspect of the present invention provides the optical head device of the first aspect, the central region being divided into three or more divided regions.

The fourth aspect of the present invention provides the optical head device of the third aspect, wherein the diffraction networks with different phases are formed in two divided regions of the three or more divided regions of the central region; and

A diffraction grating of the same grating vector and of the same phase as the diffraction grating formed in one of the two divided regions is formed in at least one divided region of a remaining divided region.

The fifth aspect of the present invention provides the optical head device of the first aspect, wherein the phase of the first diffraction grating formed in the first region of diffraction grating is 0 degree as a reference, the phase of a third The diffraction grating, formed in the divided region, obtained by dividing the central region, and the phase of a fourth diffraction grating, formed in another divided region, have opposite polarities, but the same absolute value.

The sixth aspect of the present invention provides the optical head device of the fifth aspect, wherein the phase of the first diffraction grating formed in the first divided region is 0 degree as a reference, the phase of the third diffraction grating is 90. degrees, and the phase of the fourth diffraction grating is -90 degrees.

The seventh aspect of the present invention provides the optical head device of the first aspect, where when the phase of the first diffraction grating formed in the first region of the diffraction grating is 0 degree as a reference, the phase of each The diffraction grating, formed in each divided region of the central region, is substantially 0 degree on average.

The eighth aspect of the present invention provides the optical head device of the third aspect, wherein the phase of the first diffraction grating formed in the first divided region is 0 degree as a reference, the central region is divided into four or more. split regions, to form a -120 degree phase diffraction grating, a -60 degree phase diffraction grating, a +60 degree phase diffraction grating, and a one-phase diffraction grating. +120 degrees.

The ninth aspect of the present invention makes available the provision

Optical head device comprising a light source, a diffractive element for branching an Iuz output of the light source into at least three light streams, an objective lens for converging the three Iuz streams onto a recording surface of an optical disc. and a light detector 10 for receiving the light converged on the recording surface of the optical disc by the objective lens and reflected by the optical disc and photoelectrically converting the light into an electrical signal; being that

the diffractive element is divided into a first diffraction grating region, a second diffraction grating region formed with a second diffraction grating with a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first region diffraction grating, and a central region nested between the first diffraction grating region and the second diffraction grating; and

a diffraction grating with a different direction from the first diffraction grating and the second diffraction grating is formed in the central region.

The tenth aspect of the present invention provides the ninth aspect optical head device, wherein a third diffraction grating formed in the split region obtained by dividing the central region, and a fourth diffraction grating formed in another divided region are grating networks. diffraction with a different direction from the first diffraction grating and the second diffraction grating and at an angle formed with an extension direction of an optical disc track groove of opposite signals relative to one another.

The eleventh aspect of the present invention provides an optical head device comprising a light source, a diffractive element for branching a light output of the light source into at least three light streams, an objective lens for converging the three streams. of Iuz on a recording surface of an optical disc, and a light detector, to receive the light converged on the recording surface of the optical disc by the objective lens and reflected by the optical disc and photoelectrically converting the light to an electrical signal; being that

the diffractive element is divided into a first diffraction grating region, a second diffraction grating region formed with a second diffraction grating with a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first diffraction grating region, and a central region nested between the first diffraction grating region and the second diffraction grating region; and 10 a diffraction grating with a degree of grating differing from

of the first diffraction grating and the second diffraction grating is formed in the central region.

The twelfth aspect of the present invention provides the twelfth aspect optical head device, wherein a diffraction grating formed in the central region is a diffraction grating with a lesser degree of inclination than the first diffraction grating and the second diffraction grating.

The thirteenth aspect of the present invention provides the optical head device of one of the first, ninth and eleventh aspects, with the width of the central region being 10% to 40% of a projection diameter over the diffractive element of a effective diameter of the objective lens.

The fourteenth aspect of the present invention provides the optical head device of one of the first, ninth and eleventh aspects, the light source being a two wavelength light source for emitting a red light and an infrared light. .

The fifteenth aspect of the present invention provides the fourteenth aspect optical head device, with the width of the central region being less than or equal to 30% of a projection diameter over the diffractive element of an effective lens diameter. objective.

The sixteenth aspect of the present invention provides the optical head device of one of the first, ninth and eleventh aspects, which further comprises a blue light source.

The seventeenth aspect of the present invention provides a diffractive element mounted on an optical head device, which includes a light source, an objective lens for converging a 5 æl output of the light source onto an recording surface of an optical disc, and a light detector for receiving the light converged on the recording surface of the optical disc by the objective lens and reflected by the optical disc and photoelectrically converting the light into an electrical signal, the diffractive element branching the light output from the light source into at least three light streams, including a main beam, which is transmitted without being diffracted and two sub-rays, which are diffracted; being that

the diffractive element is divided into a first diffraction grating region, a second diffraction grating, formed with a second diffraction grating with a phase differing substantially 180 degrees from a first diffraction grating arranged in the first grating region. diffraction, and a central region nested between the first diffraction grating region and the second diffraction grating region;

the central region has different network phases or vectors than the first diffraction network region and the second diffraction network region, and the divided regions, divided by the dividing line, are formed with different phase and network vector diffraction networks. on the other.

The eighteenth aspect of the present invention provides the diffractive element of the 17th aspect, the dividing line for dividing the central region extending in an orthogonal direction to an extension direction of a track groove of the optical disc.

The nineteenth aspect of the present invention provides the diffractive element of the 17th aspect, the central region being divided into three or more divided regions.

The twentieth aspect of the present invention provides the diffractive element of the nineteenth aspect, wherein diffraction networks with different phases from one another are formed in two divided regions of the three or more divided regions of the central region; and a diffraction grating of the same grating vector and the same phase as the diffraction grating formed in one of the two divided regions is formed in at least one divided region of a remaining divided region.

The twenty-first aspect of the present invention provides the diffractive element of the seventeenth aspect, wherein the phase of the first diffraction grating, formed in the first region of the diffraction grating, is 0 degree as a reference, the phase of a The third diffraction grating, formed in the divided region, obtained by dividing the central region, and the phase of a fourth diffraction grating, formed in another divided region, have opposite polarities, but the same absolute value.

The twenty-second aspect of the present invention provides the diffractive element of the twenty-first aspect, wherein the phase of the first diffraction grating, formed in the first divided region, is 0 degree as a reference, the phase of the third diffraction grating is 90. degrees, and the phase of the fourth diffraction grating is -90 degrees.

The twenty-third aspect of the present invention provides the diffractive element of the seventeenth aspect, wherein the phase of the first diffraction grating formed in the first region of the diffraction grating is 0 degree as a reference, the phase of each grating. The diffraction rate, formed in each divided region of the central region, is substantially 0 degree on average.

The twenty-fourth aspect of the present invention provides the diffractive element of the twentieth aspect, wherein the phase of the first diffraction grating formed in the first divided region is 0 degree as a reference, the central region divided into three or more regions. 25 are equipped with a -120 degree phase diffraction grating, a -60 degree phase diffraction grating, a +60 degree phase diffraction grating, and a one-phase diffraction grating. +120 degrees.

The twenty-fifth aspect of the present invention provides a diffractive element mounted on an optical head device including a light source, an objective lens for converging a light output from the light source onto an optical disc recording surface, and a light detector to receive the light converged on the recording surface of the optical disc by the objective lens and reflected by the optical disc and photoelectrically converting the light to an electrical signal, with the diffractive element branching the light output of the light source by at least three streams of light, including one main beam, which is transmitted without being diffracted, and two sub-rays, which are diffracted; being that

the diffractive element is divided into a first diffraction grating region, a second diffraction grating, formed with a second diffraction grating, with a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first grating region. diffraction, and a central region, nested between the first diffraction grating region and the second diffraction grating region;

a diffraction grating with a different direction from the first diffraction grating and the second diffraction grating is formed in the central region.

The twenty-eighth aspect of the present invention provides the diffractive element of the twenty-seventh aspect, wherein a diffraction grating formed in the central region is a diffraction grating having a lower inclination degree than the first diffraction grating. and the second diffraction grating.

The twenty-ninth aspect of the present invention provides an optical information apparatus comprising:

the optical head device according to any of the first to sixteenth aspects:

an engine for rotating an optical disc; and an electrical circuit for receiving a signal obtained from the optical head device, and controlling and driving the motor, an optical lens, and a signal-based laser light source.

The thirty-first aspect of the present invention provides a twenty-ninth optical information device,

A push-pull signal, obtained by receiving the lightning bolt on the Iuz detector and calculation by photoelectric conversion, is amplified to a factor of amplification of the factor K1, and subtracted with the push-pull signal obtained by receiving the lightning bolt. in the light detector and which is processed by photoelectric conversion to be used as an alignment error signal; and

amplification factor K1 is fixed after being adjusted to a value at which the change in control of the alignment signal becomes smaller when the objective lens is moved in a direction perpendicular to an extension direction of a disc track groove. optical.

The thirty-first aspect of the present invention provides a twenty-ninth optical information apparatus, whereby a focus error signal, obtained by receiving the lightning beam at the light detector and calculating by photoelectric conversion, is amplified to an amplification factor 10 of factor K2, and added to the focus error signal, obtained by receiving the lightning bolt from the Iuz detector and which is processed by photoelectric conversion to be used as a focus error signal to focus control.

The thirty-second aspect of the invention provides a computer comprising:

the twenty-ninth aspect optical information apparatus; an input device or input terminal for entering information;

an arithmetic device for performing an arithmetic operation based on the input device input or reproduced information from the optical information device; and

an output device or output terminal for displaying or issuing input information by the input device or the information reproduced by the optical information device, or the result of an arithmetic [operation] performed by the arithmetic device.

The thirty-third aspect of the present invention provides an optical disc player comprising:

the twenty-ninth aspect optical information apparatus; and an image information decoder for converting an information signal obtained by the optical information device into an image.

The thirty-fourth aspect of the present invention provides a car navigation system comprising:

the twenty-ninth aspect optical information apparatus;

an image-information decoder for converting an information signal obtained by the optical information device into an image; and

a position sensor.

The thirty-fifth aspect of the present invention provides an optical disc recorder comprising:

the twenty-ninth aspect optical information apparatus; and an information-image encoder to convert information

information on information to be recorded by the optical information

The thirty-sixth aspect of the present invention provides a vehicle comprising: the twenty-ninth optical information device, a vehicle body mounted with the optical information device, and a power generating unit for generating energy for moving the vehicle. vehicle body.

The thirty-seventh aspect of the present invention provides an optical head device comprising a light source, a diffractive element for branching a light output of the light source into at least three light streams, including a main beam, which is transmitted without being diffracted and two sub-rays, which are diffracted, an objective lens to converge the three light streams on an optical disc recording surface, and a light detector to receive the converged light on the surface of an optical disc. recording of the optical disc through the objective lens and reflected by the optical disc and converting the light electrically into an electrical signal; being that

the diffractive element includes a first divided region, a second divided region, a third divided region, and a fourth divided region;

a first diffraction grating is formed in the first region

divided; a second diffraction grating with a phase differing substantially 180 degrees from a first diffraction grating is formed in the second divided region;

a third diffraction grating, with a phase that differs substantially by -90 degrees from the first diffraction grating, is formed in the third divided region; and

a fourth diffraction grating, with a phase that differs substantially +90 degrees from the first diffraction grating, is formed in the fourth divided region.

The thirty-eighth aspect of the present invention provides

A diffractive element, used in an optical head device, which includes a light source, a diffractive element for branching a light output of the light source into at least three light streams, including a main beam, which is transmitted without being diffracted. and two sub-rays, which are diffracted, an objective lens for converging the three light streams on an optical disc recording surface, and a light detector for receiving the converged light on the optical disc recording surface. by the objective lens and reflected by the optical disc and photoelectrically converting the light into an electrical signal; wherein the diffractive element includes a first divided region, one section

second divided region, a third divided region and a fourth divided region;

a first diffraction grating is formed in the first region

divided;

a second diffraction grating with a phase that differs

substantially 180 degrees of a first diffraction grating is formed in the second divided region;

a third diffraction grating, with a phase that differs substantially by -90 degrees from the first diffraction grating, is formed in the third divided region; and

a fourth diffraction grating, with a phase that differs substantially +90 degrees from the first diffraction grating, is formed in the fourth divided region.

Effect of the Invention

According to the embodiment of the present invention, an effect of obtaining the alignment error signal by the optimal DPP 5 method is obtained with respect to the optical disc with different degrees of track inclination using a single diffractive element such as suppress the reduced amount of alignment error signal amplitude, in a state in which the objective lens is moved by track accompaniment.

That is, the signal amplitude in a state in which the objective lens is not moved by track accompaniment is decreased in advance, and the reduction in the alignment error signal amplitude in a state in which the objective lens is moved, is relatively avoided by having split regions forming different diffraction grids than diffraction grids of the first diffraction grating region and the second diffraction grating region in a central region, nested between the first diffraction grating region and the second region. of diffraction grating. In addition, the phase is prevented from gradually shifting over the entire surface of the diffraction grating by dividing the central region nested between the first diffraction grating region and the second diffraction grating region into a plurality of divided regions. and having diffraction grids having different phases than each other, thereby obtaining that the respective sub-radius has a symmetrical light quantity distribution line in one direction (alignment direction) by moving the optical head relative to one line. symmetrical in a direction substantially parallel to the projection in the direction of extension on the optical disc track.

Brief Description of the Drawings

These and other aspects and features of the present invention are clear from the description below, taken in conjunction with preferred embodiments thereof, with reference to the accompanying drawings, in which:

Figure 1 is a view showing schematically a confi

configuration of an optical head device according to a first embodiment of the present invention; Figure 2 is a view showing a configuration of a diffractive element mounted on the optical head device of Figure 1;

Figure 2B is an explanatory view of a convergence point on an optical disk when the diffraction grating of Figure 2A is used;

Figure 3 is a view showing schematically the configuration

an optical head device according to a second embodiment of the present invention;

Figure 4A is a view showing a main beam and sub-ray transmitting region when the diffraction grating shown in Figure 2A is mounted on the optical head device of Figure 3;

Figure 4B is an explanatory view of a point of convergence on an optical disc when the diffraction grating of Figure 4A is used in the optical head device of Figure 3;

Figure 5A is a view showing a configuration of a diffractive element mounted on the optical head device of Figure 3;

Figure 5B is an explanatory view of a convergence point on an optical disk when the diffraction grating of Figure 5A is used;

Figure 6A is a view showing a configuration of a diffraction grating of a third embodiment of the present invention;

Figure 6B is an explanatory view of a convergence point.

above an optical disc when the diffraction grating of Figure 6A is used;

Figure 7A is a view showing a configuration of a diffraction grating of a fourth embodiment of the present invention;

Figure 7B is an explanatory view of a convergence point on an optical disk when the diffraction grating of Figure 7A is used;

Figure 8A is a view showing a configuration of a fifth embodiment diffraction grating of the present invention;

Figure 8B is an explanatory view of a convergence point on an optical disk when the diffraction grating of Figure 8A is used;

Figure 9A is a view showing a configuration of a

diffraction pattern of a sixth embodiment of the present invention;

Figure 9B is an explanatory view of a convergence point on an optical disk when the diffraction grating of Figure 9A is used;

Figure 10 is a schematic view showing an example of a light detector configuration used in combination with a sub-radius generating diffractive element in the optical head device of each embodiment of the present invention;

Figure 11 is a schematic view showing another example of a light detector configuration used in combination with a sub-radius generating diffractive element in the optical head device of each embodiment of the present invention;

Figure 12 is a view schematically showing a confi

configuration of an optical head device according to another embodiment of the present invention;

Figure 13 is a schematic view showing a configuration of a light detector mounted on the optical head device shown in Figure 12;

Figure 14 is a schematic view showing a configuration of an optical information apparatus mounted with the optical head device of Figure 12;

Figure 15 is a schematic perspective view showing a configuration of a computer mounted with the optical information apparatus of Figure 14;

Figure 16 is a schematic perspective view showing a configuration of an optical disc player mounted with the optical information apparatus of Figure 14;

Figure 17 is a schematic perspective view showing

an arrangement of an optical disc recorder mounted with the optical information apparatus of FIG. 14;

Figure 18 is an explanatory view showing a configuration of a vehicle mounted with the optical information apparatus of Figure 14; Figure 19 is a view schematically showing a confi

configuration of a conventional optical head device;

Figure 20A is a front view showing a configuration of a diffractive element of the optical head device shown in Figure 19;

Figure 20B is a cross-sectional view showing a configuration of a diffractive element of the optical head device shown in Figure 19;

Figure 21 is an explanatory view of a convergence point.

over an optical disc in the conventional optical blind device;

Figure 22A is a front view showing a configuration of a diffractive element of the conventional optical head device;

Figure 22B is an explanatory view of a point of convergence over the optical disc when the diffraction grating shown in Figure 22A is used;

Figure 23A is a front view showing a diffractive element configuration of the conventional optical head device;

Figure 23B is an explanatory view of a point of convergence over the optical disk when using the diffraction grating shown in Figure 23A;

Fig. 24A is a view showing a state of change in the diffraction phase which becomes the main component of the diffractive element of the optical head device shown in Fig. 23A; and Figure 24B is an explanatory view of a convergence point.

over the optical disc when using the diffraction grating shown in the figure

24 A.

Best Mode for Performing the Invention

Before proceeding with the present disclosure, it should be noted that equal parts are designated by like reference numerals in all accompanying drawings. The first embodiment of the present invention is now described in detail with reference to the drawings.

(First Mode)

Figure 1 is a view schematically showing a configuration of an optical head device according to a first embodiment of the present invention.

A light beam 14 irradiated from a light source (e.g., red light source) 12 is transmitted through a diffractive element 31, which diffracts some light (partial diffraction) and then reflects it into a beam splitter 3000, and has alignment converted (e.g. to substantially parallel light) by the collimator lens 70, with the light beam 14 being converged on the recording surface of the optical disc 27 such as DVD-R and DVD-RAM etc. through a transparent base material about 0.6 mm through objective lens 25 to form a sub-point on optical disc 27. The light ray reflected by the recording surface of optical disc 27 passes the same path from Iuz towards o10, transmits through the radius divider 3000, and is then branched towards a different direction from the light source 12 and at the same time endowed with astigmatism. The light beam is photoelectrically converted by a Light 10 detector to obtain electrical signals for information signals, servo signals (focus error signal for focus control, and alignment error signal 15 for alignment control). If an amplifier circuit is incorporated into the light detector 10, a satisfactory information signal with a high signal to noise ratio (Y / N) is obtained, and the optical head device is miniaturized and is stability is obtained.

Although not shown, the optical head can be thinned by bending the optical axis in a direction perpendicular to the optical disc, such as DVD-R and DVD-RAM, providing a raised mirror between the collimator lens 70 and the objective lens 25.

Figure 2A is a view showing a configuration of a diffractive element 31 mounted on the optical head device of Figure 1. In Figure 2A, the dotted line is a boundary line showing virtually the boundary 3108 of the region. diffraction grating. The diffraction grating in each diffraction grating region has the centerline of the convex part shown with a full line. The degree of inclination of the diffraction grating is suitably designed by the arrangement of the diffractive element 31.

The direction T is the direction perpendicular to the optical axis of the radius lu

minute and substantially perpendicular to a projection extending towards the optical disc track groove (not shown), and Z-direction is a direction of the optical axis (direction perpendicular to the drawing plane) of the light ray. The T-axis is a direction of movement of the optical head device when recording or playing the inner and outer periphery of the optical disc, and is a direction in which the objective lens moves according to track accompaniment. The Y axis is a direction perpendicular to the Z axis and the T axis, and is a direction substantially parallel to the direction extending in the optical disc track groove. In the above description, the projection is performed including specular inversion etc. along the optical axis of the light ray.

The diffractive element 31 of this application is divided into re

gions by a dividing line (dotted line), parallel to the direction of the Y groove, as shown in figure 2A, thereby forming diffraction grids. Assuming that the network phase of the first diffraction grating region 3101 on the left side of the figure is the reference (the degree), the network phase of the second diffraction grating region 3102 on the right side of the figure is 180 degrees. The change in Y direction of the network phase is positive. The central region 3109, between the first 0 degree phase diffraction grating region 3101 and the 180 degree phase second diffraction grating region 3102, is divided into regions by a dividing line 3108 which extends 20 in the T direction, with a third diffraction grating region 3103 with a phase and 90 degrees and a fourth diffraction grating region 3104 with a phase of -90 degrees being arranged in the Y direction. in other words, region 3109 between the first diffraction grating region 3101 and the second diffraction grating region 3102 is further divided into a plurality, and the network phases of the divided regions 3103, 3104 assume opposite signal values. such as + 90 degrees and -90 degrees. The network phase is in the range of -180 degrees to +180 degrees in the present embodiment. Since the phase has a periodicity, in which a period is 360 degrees, the phase can be indicated in other scopes by adding or subtracting multiples of 30 360 degrees. For example, when the grid phase is indicated within the range 0 degrees to 360 degrees, 360 degrees added only when the phase is negative, and the grid region phase phase 3104 of the present embodiment becomes the same as if it were indicated as 270 degrees. The network phase is indicated within the range -180 degrees to +180 degrees in the present application, described below. The amplitude of the signal in a state in which the objective lens is not moved by track accompaniment is reduced in advance, and the reduction in the amplitude of the alignment error signal in a state in which the objective lens is moved is relatively avoided by having the regions 3103, 3104, which form diffraction grids different from the diffraction grids of the first diffraction grating region 3101 and the second diffraction grating region 3102 in the central region 3109, fitted between the first diffraction grating region 3101 and the second diffraction grating region 3102. The phase is prevented from gradually shifting over the entire surface of the diffractive element 31 and a light quantity distribution in which the sub-rays 33, 34 are symmetrically in line in the T direction. , with respect to the symmetrical line in the Y direction, is obtained by forming regions obtained by dividing the central region 15 3109, fitted between the first diffraction grating region 3101 and the second diffraction grating region 3102 in a plurality and having diffraction grids of different phases from one another. Specifically, as shown in simplified form in Figure 2B, each sub radius appears to be divided into two rays, as light quantity level lines are shown. That is, according to the embodiment of the present invention, an effect of satisfying both the obtaining of the alignment error signal by the optimal DPP method with respect to the optical disc 27 of varying degrees of track inclination is obtained by using the element diffractive signal 31, such as suppressing the reduction in the amount of signal alignment error 25 amplitude in a state, in which the objective lens is moved by track accompaniment.

The essential feature of the invention described in the present example is that it divides the network region into at least one first to fourth region, with at least the third region and fourth region 30 being disposed between the first region and the second region, with the +90 degree and -90 degree phase being given in each case to the third region and the fourth region, assuming that the first region network phase is the reference (0 degree) and the second region phase is 180 degrees. In other words, four phase peak networks, with phases that differ by 90 degrees, are formed in the first region to the fourth region. The effect described above is obtained by this feature.

5 The network pattern which is linear and of uniform period is illustrated.

and it's in the same direction. This means that the direction and size of the network vector are the same. But the present application is not limited to the example of a uniform network vector. The grid, which is the basis of the phase shift, may be curved, the grid period may be partially changed, or the grid direction may be partially changed to change the sub-radius wavefront to the radius front. desired. In this way, the effect of reducing off-axis aberrations of the objective lens is obtained. Off-axis aberration is the aberration that is generated when the beam enters the lens diagonally.

The T-direction width of central region 3109, fitted between the first diffraction grating region 3101 and the second diffraction grating region 3102, is suitably 10% to 40% of the projection diameter (hereinafter referred to as the effective diameter) in the plane of the diffraction grating 31 to the limited aperture main radius disposed close to the objective lens with respect to the red light. Unless otherwise indicated, this applies equally to the following embodiments. Signal variation at lens shift time can thus be suppressed while ensuring the signal strength obtained by the sub-radius by setting the width in the T direction.

In the above embodiment, the central region 3109, fitted between the first diffraction grating region 1 and the second diffraction grating region 2, is divided into a plurality to obtain two regions of the third diffraction grating region 3103 and the fourth diffraction grating region 3104, using the dividing line 3108, which extends in the T direction, but can be divided by dividing the line that extends in the Y direction, rather than the T direction, 30 to arrange the plurality of regions in the direction T. The region can be divided into an intermediate angle of the Y direction and the T direction. Also in this case, an effect can be obtained that the phase is relieved from shifting gradually over the entire surface of the diffraction grating 31, and sub-spokes 33, 34 approach a symmetrical light quantity distribution in line in the T direction with respect to the symmetrical line in the Y direction. This applies equally to the following embodiments.

5 (Second Modality)

Due to restrictions on the external shape of the optical head device, the sub-ray generating diffractive element used in place of the diffractive element 31 of FIG. 1 must be arranged near a light source 12 and spaced from the collimating lens 70. According to this arrangement, the required effective diameter of the diffractive element 3100 is reduced and the external shape is miniaturized, and thus the material cost of the diffractive element 3100 decreases.

In this case, however, the region from which the sub-radius is generated at diffractive element 3100 differs from the region from which the main radius is generated, and the generating region 402 from sub-radius 242 and the generating region 403 from sub-radius 243 they are changed in the Y direction with respect to the transmitting region 401 of the main radius 214 as shown in figure 4A. This is because the sub beam is a diffracted light, and the optical axis is inclined from the main radius, and the projection position on the limited aperture sub beam disposed near the objective lens is shifted from the projection position of the objective lens in the main radius. The generating regions are changed because the sub-radius, which is the diffracted light, bends toward a different direction from the main radius. Therefore, the amount of change of the generating region, defined by the product of the angle and distance, becomes greater the greater the distance to the limited aperture disposed near the objective lens of the diffractive element, that is, the closer the diffractive element is to the light source. Since the lightning radius diameter or limited aperture mapping is small the closer the diffractive element is to the light source, the ratio of the change to the radius diameter becomes larger. Focusing on generating region 403 of sub-radius 243, subtray 243 in the region between the first diffraction grating region 3101, with a 0 degree phase, and the second diffraction grating region 3102, with a 180 degree phase, it is mainly generated by the third diffraction grating region 3103, with a 90 degree phase. Thus, sub-radius 243 has the phase of the 0 degree diffraction grating, substantially 90 degrees, and 180 degrees from the left, and the phase changes gradually. Thus, a state occurs close to the prior art example shown in figures 23A, 23B.

Focusing on sub-radius 242 generating region 403, sub-radius 242 in a region between the first 0 degree phase diffraction grating region 3101 and the 10 phase second diffraction grating region 3102 180 degrees, is mainly generated by the fourth diffraction grating region 3104, with a phase of -90 degrees. In addition, the phase of securing the diffraction grating region 3102 is -180 degrees, given the 360 degree periodicity. Thus, sub-radius 242 has a phase of the diffractive element of 0 degrees, substantially - 90 degrees, and -180 degrees, from the left and 15 the phase changes gradually. Thus, a state occurs locally close to the prior art example shown in figures 23A, 23B.

Since the diffraction grating phases of the sub-ray generating regions are gradual in shape, the sub-rays are asymmetric as shown in Figure 4B, and displacement occurs in the push-pull alignment error signal on the radius. main and sub-radius, and the amount of displacement fluctuates, depending on the degree of track inclination of the optical disc and cannot be corrected with a constant correction value.

In order not to give rise to this case, the central region 3119, en25 enclosed between the first diffraction grating region 3111 and the second diffraction grating region 3112, is divided into a plurality of regions of three or more by one. or more virtual boundary lines 3118, to provide diffraction networks 3113, 3114, with a plurality of phase types in the present embodiment, as shown in figures 5A and 6A. In Figure 5A and 30 below, the line of the convex part of the diffraction grating is omitted for the sake of simplicity, for the grating in a direction equal to the degree of inclination. When only the diffraction grating phase is shown, the degree of inclination and grating direction in the same region are assumed to be constant.

The diffraction grating 3110 of FIG. 5A divides the central region 3119 between the first diffraction grating region 3111 with a 0 5 degree phase (reference) and the second diffraction grating region 3112 with a 180 degree phase. , in five regions across four dividing lines 3118, extending in the T direction, where the three regions are the third diffraction grating region 3113, with a 90 degree phase and the remaining two regions are the fourth diffraction grating region 3113B, with a phase of -90 degrees. 10 According to this configuration, the 4310 generator region of the

sub-radius 3410 and sub-radius 3310 generating region 4210 substantially contain the diffraction grating region 3A with a 90 degree phase and the diffraction grating region 3B with a -90 degree phase, and thus sub-radius 3310 and sub-radius 3410 are symmetrical as shown in Fig. 5B. Therefore, the effect of satisfying both the alignment error signal obtained by the optimal DPP method with respect to the optical disc with different degree of track inclination can be obtained by using a single diffractive element, as well as the suppression of the reduced amount in the amplitude of the alignment error signal, in a state, in which the objective lens 20 is moved by track accompaniment. The number of regions divided by the dividing line 3118, which extends in the T direction, is not limited to five and only needs to be three or more and thus may be greater than five.

(Third Mode)

The 3120 diffraction grating according to the third mode of

The present invention is used in place of the diffractive element 31 of Figure 1. As shown in Figure 6A, the diffractive element 3120 divides the central region 3129 between the first 0 degree phase diffraction grating region 3121 and the second one. diffraction grating region 3122 with a phase of 180 30 degrees in seven regions for six divider lines 3128 extending in the T direction to provide the third diffraction grating region 3123 with a phase of 60 degrees being whereas the fourth diffraction grating region 3124 has a 120 degree phase, a fifth diffraction grating region 3125 with a -120 degree phase, and a sixth diffraction grating region 3126 with a -60 degree phase . In accordance with the present embodiment, sub-radius 3420 generating region 4320 and sub-radius 3320 generating region 4220 include substantially equally diffraction grating regions whose phases are contradictory to one another and thereby , sub-radius 3320 and sub-radius 3420 are symmetrical as shown in figure 6B. Therefore, an effect can be obtained of satisfying both the alignment error signal obtained by the optimal DPP method with respect to the optical disc with varying degrees of track inclination using a single diffractive element, as well as the suppression of the reduced amount. in the amplitude of the alignment error signal, in a state in which the objective lens is moved by tracking the track. The number of regions to be divided by dividing line 3128, which extends in the T direction, is not limited to seven and may be larger. The diffraction grating phase formed in the central region 1329 between the diffraction grating region 1 and the diffraction grating region 2 forms a network with opposite signal phases, or the average of the diffraction grating phase formed in the central region 3129 it only needs to be substantially 0 degrees, and is not necessarily limited to ± 60 degrees, ± 90 degrees, ± 120 degrees, etc.

(Fourth Modality)

In another embodiment, an example of a diffractive element arranged with a region forming a diffraction grating with a different grating vector than the diffraction grating of the diffraction grating region 25 and the diffraction grating region 2 is disclosed. in the central part, fitted between the first diffraction grating region and the second diffraction grating region. An example of using the diffractive element in place of the diffractive element 31 of FIG. 1 is described using FIG. 7A. The diffractive element 3130 of FIG. 7A divides the central region 3139 between the first 0 degree phase diffraction grating region 31 3131 and the 180 degree second phase diffraction grating region 3132 into five regions. by four dividing lines 3138 extending in the T direction, three regions being the third diffraction grating region 3133, with a convex centerline diagonally to the bottom right in the figure, and the remaining two regions are the fourth diffraction grating region 3134, with a centerline of the convex portion, diagonally left below in the figure. That is, the network vector directions of the first diffraction grating region 3131, the second diffraction grating region 3132, and the central region 3139 are changed. In the present embodiment, the central region diffracted light 3139, fitted between the first diffraction grating region 3131 and the second diffraction grating region 3132, is irradiated at different positions of sub-rays 3330, 10 3430 than in the light. 3530 and diffracted light 3630 of FIG. 7B on the recording surface of the optical disc. Similarly, when reflected by the optical disc and irradiated in the light detector, the light is irradiated at different positions from sub-rays 3330, 3430. Thus, the beam transmitted through the central region 3139 does not contribute to the formation of the push signal15. pull and signal amplitude, in a state in which the lens slow is not moved by track accompaniment, is reduced in advance. Therefore, reduction in amplitude of the alignment error signal in a state in which the objective lens is moved is relatively avoided. Sub-radius 3330 and sub-radius 3430 are symmetrical as shown in Figure 7B, and thus an effect of satisfying both alignment error signaling by the optimal DPP method with respect to the ratio can be obtained. to the optical disc with varying degrees of track tilt, using a single diffractive element, such as suppressing the reduction in the amount of alignment error signal amplitude, in a state in which the objective lens is moved by track accompaniment. The number of regions to be divided by the dividing line, extending in the direction t, is not limited to five, and may be a larger number.

(Fifth Modality)

A diffractive element 3140 of FIG. 8A, used in place of the diffractive element 31 of FIG. 1, forms a third diffraction grating region 3143, with a different degree of inclination from the first diffraction grating region 3141 and the second grating region. diffraction 3142, in a central region 3149 between the first diffraction grating region 3141, with a 0 degree phase, and the second diffraction grating region 3142, with a 180 degree phase. Even if the direction of the centerline of the convex part of the diffraction grating arranged in the third diffraction grating region 3143 is equal to that of the first diffraction grating region 3141 and the second diffraction grating region 3142, the size of the vector network differs as the degree of inclination is different. The axis direction of the convex part can be changed. In the present embodiment, the diffracted light transmitted through the central region 3149, fitted between the first diffraction grating region 31141 and the second diffraction grating region 3142, is irradiated to different positions of sub-rays 3340, 3440, as in the light. 3540 and the diffracted light 3640 of FIG. 8B on the recording surface of the optical disc. Similarly, when reflected by the optical disc and radiated over the light detector, the light is irradiated at different positions from sub-rays 3340, 3440. Thus, the beam transmitted through central region 3149 does not contribute to signal formation. push-pull, and signal amplitude, in a state in which the objective lens is not moved by track accompaniment, is reduced in advance. Therefore, the empliutde reduction of the alignment error signal in a state in which the objective lens is moved is reliably avoided. Sub-radius 3340 and sub-radius 3440 are symmetrical as shown in Fig. 8B, and thus an effect of satisfying both the alignment error signaling by the optimal DPP method is obtained with respect to to the optical disc with varying degrees of track tilt, using a single diffractive element, such as suppressing the reduction in alignment error signal amplitude, in a state in which the objective lens is moved by track accompaniment. In addition, the central region 3149, fitted between the first diffraction grating region 3141 and the second diffraction grating region 3142, can be divided into regions by a dividing line (not shown) extending in the T direction to form networks of varying degrees of inclination.

(Sixth Modality)

The alignment error signal detection method by the DPP1 method is sometimes used with the focus error signal detection method by the differential astigmatism method. Patent Document 5 (International Published Publication No. WO 2004/097815) describes the method of differential astigmatism and improvement in the focus error signal defocusing characteristic by the differential astigmatism method. The diffraction grating divides the diffraction grating to generate the sub radius into four regions, where the phase of the adjacent regions differs by 180 degrees and the opposite regions are adjusted with the same phase. In this diffraction grating, the sub radius is divided into four, and when the sub radius is arranged in the same groove as the main radius on the recording surface of the optical disc, the sub radius push-pull signal has an opposite polarity. to the main radius, thereby performing the DPP method. In addition, the cross-action of the push-pull signal component with the focus error signal is eliminated by detection and addition of the focus error signal by the astigmatism method of both the main radius and the sub radius.

In the sub-radius generating diffraction grating described in patent documents 3 and 4, only one area is provided for the grating part with a 0 degree phase and the grating part with a 180 degree phase.

As shown in Figure 9A, in the present embodiment, a left-hand diffraction region 3151 of the diffractive element 3150 used in place of the diffractive element 31 of Figure 1 is divided into regions by the limit 3158L extending in the T direction. , in a diffraction grating region A 3151A and a diffraction grating region B 3151B, where the diffraction grating phase of the diffraction grating region A is 0 degree and the phase of the diffraction grating region B is 180 degrees . In addition, the diffraction region 3152 on the right side of the diffraction grating 3150 is divided into regions by a limit 3158R extending in the T direction, a diffraction grating region A 3152A and a diffraction grating region B 3152B where the phase of the diffraction grating region A 3152A is 180 degrees and the phase of the B 3152B diffraction grating region is 0 degree. The 3151A diffraction grating region of the left-hand diffraction region 3151 and the 3152A diffraction grating region of the right-hand diffraction region 3152 have diffraction grating phases that differ by 180 degrees from each other, and the diffraction grating region B 3151B from the diffraction grating region 3151 on the left and diffraction grating region B 3152B from the diffraction grating region and 3152 on the right have diffraction grating phases that differ by 180 degrees from each other, and hence In this way, the polarity of the main and sub-radius push-pull signals is also opposite. Similarly to patent document 5, the focus error signal blurring feature by the differential astigmatism method is also improved, and the cross-action of the push-pull signal component with the focus error signal is suppressed. The aspect of the present example, that the central region 3159 is disposed between the left diffraction region 3151 and the right side diffraction region 3152, differs from the patent documents described above. An effect is obtained of suppressing the reduction in the amount of alignment error signal amplitude in a state in which the objective lens is moved by track accompaniment 15 by the arrangement of the central region 3159. The specific configuration of the central region 3159 can be any of the above modalities.

(Light detector)

The light detector, used in combination with the sub-radius generator diffractor according to the embodiment of the present invention, is now described.

Figure 10 shows an example of a configuration which splits the light detection regions of the light detector 10 suitable for detecting the focus error signal by the differential astigmatism method and detecting the alignment error signal by the DPP method. In Figure 10, the Y, 25 T, Z axes are common to those shown in Figure 1. A pattern of the Light 10 detector is shown when viewed across the opposite surface from which the beam of light enters. The receiving region of Light 20, to receive the main radius, is also divided into four and the focus error (FE) signal is detected using astigmatism, formed when transmitted through the 30-ray divider 3000. Expressing the name of each region divided as signal output intensity, the EF can be calculated by equation 1.

(Eq. 1) FE = (20A + 20C) - (20B + 20D) The alignment error signal by a so-called phase difference method or push-pull method can also be obtained. The alignment signal by phase difference method is obtained by comparing the phase of change in time signal intensity of 20A + 20C and 20B + 20D. Signal of alignment error by the main radius push-pull method (TEPP) is calculated by equation 2.

(Eq. 2) TEPP + (20A + 20B) - (20C + 20D)

The light receiving regions 21, 22 receive the sub-radius. The alignment error signal by the push-pull method can be detected by calculation with the push-pull signal of the Iuz 20 receiving region, the focus error signal can be detected by the astigmatism method of the Iuz 21 receiving regions 22 is calculated with the focus error signal obtained from the receiving region 20 of Iuz to remove cross-action with the alignment signal.

The TEDPP alignment error signal by the differential push-pull method is calculated by equation 3.

(Eq. 3) TEDPP = (20A + 20B) - (20C + 20d) -K1 [(21A + 21B) (21C + 21D)] - K1 (22A + 22B) - (22C + 22D)],

where K1 is a constant. By properly defining the constant K1, the push-pull alignment error signal is prevented from floating when the objective lens moves in the T-direction by track accompaniment. The cause of fluctuation in the misalignment signal when the objective lens moves in the T direction is the movement of the light beam on the light detector 10 when the remote field pattern moves. Since the main radius and subrays are also subject to the influence of remote field pattern movement, K1 is adjusted to cancel the ratio of the main beam Iuz amount and the sub beam Iuz amount. Specifically, the groove-free optical disc is prepared, focus control is performed, and the objective lens is forcibly moved in the T direction to set the value of K1 so that the change in TEDPP becomes sufficiently small. The value of K1 needs to be changed for each degree of track inclination of the optical disc in patent document 3, but preferably the value of K1 is preferably set according to the Iuz amount distribution of the optical pattern. remote field of the light ray and the diffraction efficiency of the diffractive element for sub-ray diffraction. Therefore, K1 is desirably a device-unique constant, such as mounting a semifixed resistor on the optical head device or circuit substrate of the optical information device, and dispatching after adjusting amplifier amplification.

The EDF focus error signal by the differential astigmatism method is calculated by equation 4.

(Eq. 4) EDF = (20A + 20C) - (20B + 20D) -K2 [(21A + 21C) - (21B + 21D)] K2 [(22A + 22C) - (22B + 22D)],

where K2 is a constant. The cross action of the alignment signal with the focus error signal is removed by the appropriate definition of the constant K2. Particularly, as the push-pull signal of the DVD-RAM is large, K2 is desirably adjusted so that the alignment action of the alignment signal 15 with the focus error signal becomes minimal with respect to the DVDRAM disc. . Focus control is performed on the DVD-RAM disc, and the objective lens is forcibly moved in the T-direction to set the value of K2 so that the change in FED focus error signal becomes small enough. Similarly to K1, K2 is desirably a unique constant for the device, such as mounting a semifixed resistor on the optical head device or the circuit substrate of the optical information device, and dispatching after adjusting amplifier amplification. .

In DVD-R, DVD-RAM, DVD-ROM, as the push-pull signal is relatively small, a circuit for switching according to the type of optical disc is arranged in the optical information device, so that the signal of Focus error uses FE from equation 1, and uses EDF from equation 4 only so that the DVD-RAM plays the signals.

(Other examples of light detector configuration)

Now described is a light detector, used in combination with a sub-ray generating diffractive element according to the above embodiment of the present invention, capable of reproducing or recording not only the DVD but also the CD. Light source 12 in Figure 1 is presumed to be a two-wavelength light source to radiate not only red light but also infrared light. As described in patent document 6 (Japanese Published Patent Publication No. 7-98431), with the region divided into inner periphery and outer periphery, objective lens 5 converges to the light passing through both the inner periphery and the outer periphery. to the DVD and converges only the Iuz that passes through the inner periphery to the CD. Playback and recording of both CD and DVD are performed using the Iuz 1000 detector shown in figure 11. In figure 11, the Iuz detector regions 20, 21, 22 function in the same manner as the Iuz detector 10 shown in Figure 10. The Light detector 1000 is further arranged with the light detector regions 23, 24, 25 to receive the infrared light. The light detector region 23 is divided into four, and the light detector regions 24, 25 are divided into two. Similarly to when the Iuz 20 receiving region receives the red Iuz, the infrared 15 Iuz is received by the Iuz 23 detecting region, and the focus error signal is detected by the astigmatism method and the alignment error signal, by the push-pull method or the phase difference method. When writing to CD-R or CD-RW, the alignment error signal is detected by the DPP method using the output of the Iuz 24, 25 detector regions. The TEDPPCD alignment error signal by the DPP method is detected. by calculating with equation 5.

(Eq. 5) TEDPPCD = 923A + 23B) - (23C + 23D) -K3 (24A-24B) K3 (25A-22B),

where K3 is a constant. The alignment error signal by the push25 pull method is prevented from fluctuating when the objective lens moves in the T direction by track accompaniment by properly setting the constant K3. The cause of fluctuation in the misalignment signal when the objective lens moves in the T direction is the movement of the light beam on the 1000 light detector when the remote field pattern moves. Since the main radius and 30 subbeams are also subject to the influence of the movement of the remote field pattern, K3 is adjusted to cancel the ratio of the Iuz amount of the main radius and the Iuz amount of the subfield. Specifically, the groove-free optical disc is prepared, focus control is performed, and the objective lens is forcibly moved in the T direction to set the value of K3 so that the change in TEDPPCD becomes small enough. The value of K3 is preferably defined according to the light quantity distribution of the remote field pattern of the light ray and the diffraction efficiency of the diffractive element for sub-radius diffraction. Therefore, K3 is desirably a device-unique constant, such as mounting a semifixed resistor on the optical head device or circuit substrate of the optical information apparatus, and dispatching after adjusting the amplifier amplification.

As the diffractive element described in the previous embodiments is used as the sub-ray generating diffractive element in the present application, a satisfactory DPP signal can be obtained, even on CD, where the degree of track inclination differs extensively from the DVD. But since the effective diameter 15 of the infrared light is about 3/4 of the red light, the width of the region between the diffraction grating region 1 and the diffraction grating region 2 of the sub-ray generating diffractive element is, desirably less than or equal to 30% of the effective diameter (objective lens projection) of the red light. As previously described, that the width is desirably 10% to 20 40% in the optical head intended for DVD, the width of the region between the diffraction grating region 1 and the diffraction grating region 2 of the generating diffractive element The sub beam is desirably 10% to 30% of the effective diameter (objective lens projection) of the red light to satisfy both requirements when also playing the CD.

(Optical head device)

It is now described the optical head device capable of playing or recording not only DVD but also CD and BD. In Figure 12, the T direction is a direction perpendicular to the optical axis of the objective lens 9 and substantially perpendicular to the track groove extending towards the optical disc (not shown), and in the Z direction is a direction of the optical axis. objective lens 34, 41, i.e. focusing direction (direction perpendicular to the plane of the drawing). The T-axis is a direction of movement of the optical head device when recording and playing the inner periphery and the outer periphery of the optical disc. The Y axis is a direction perpendicular to the Z axis and the T axis and is a direction substantially parallel to the rail groove extending towards the optical disc at the objective lens position 5 9. The specular inversion configuration may be adopted, wherein the T axis and Y axis are reversed, or rotated 90 °, 180 °, 270 °.

The linear polarized light beam 2 radiated from a first short wavelength light source (eg blue light source) 1 is reflected by a polarization separation film on the surface of a parallel flat plate 3 and transmitted through of a hologram element 4. A reflected hologram (not shown) is formed in a region that does not obscure the light incident on the objective lens 9, away from the optical axis of the hologram element 4, and a monitor signal to stabilize it. The light intensity is obtained, without increasing the number of components, by receiving the diffracted light reflected in the light detector 10 and monitoring the light intensity of the light beam 2.

The light ray 1 transmitted through the hologram element

4 is converted to light flux, which is further diverged by a relay lens 5. Relay lens 5 has a concave lens effect, and converts the estimation angle of light source 1 from the aperture portion of objective lens 9, that is, the numerical aperture on the light source side (NA) is converted from small NA in the vicinity of the light source to large NA on the side of the collimating lens 7. The alignment of the light beam 2 is converted to near the alignment by the collimating lens 7 and the optical axis is curved in the direction of the Z axis perpendicular to the optical disc by the raised mirror 8. The objective lens 9 passes the light ray 2 through the transparent base material, about 0.1 mm plus 0.6 mm, and the light beam 2 converges on the recording surface of the high density optical disc such as BD. The collimator lens 7 corrects alignment, that is, corrects the degree of divergence, and can be configured by two combined lenses. By moving collimating lens 7 towards the optical axis to correct for a spherical aberration, if collimating lens 7 is configured by two lenses, only one of the two lenses needs to be moved. A quarter-wavelength 18 plate changes linear polarized light to circular polarized light. The light ray reflected on the recording surface of the optical disc follows the original light path in the opposite direction, and is made for the linear polarized light in the direction perpendicular to the direction exiting light source 1 by the quarter-length plate. wave 18, and transmitted through a branch member, such as a parallel flat plate 3, with the bias separation film formed on the surface, together with a portion of the light ray diffracted by the 10 hologram element 4, branched to a direction different from the light source 1, and photoelectrically converted by the Iuz 1010 detector, so that electrical signals are obtained, to obtain the information signal and servosignal (focus error signal for focus control, that is, focus servosignal and alignment signal for alignment control).

The radiated light beam 15 from the second source of Iuz (for example

infrared light source) 12 is transmitted through the diffractive element (13) (partial diffraction) to diffract some light to form a sub-point on the optical disc transmitted through a wedge 6 with a cross-sectional shape. wedge, and has the alignment converted by the slow collimator (e.g., substantially parallel light) and the optical axis curved by the raised mirror 9 in a direction perpendicular to the optical disc, such as compact disc (CD), with higher recording density. lower than BD. The objective lens 9 passes the light ray 14 through the transparent base material, about 1.2 mm, and converges the light ray 25 over the recording surface of the optical disc. The light ray reflected by the recording surface of the optical disc follows the original light path in the opposite direction, branched to a different direction from the light source 12 by a branch member, such as a polarization separation film disposed on the surface on the side. of the collimating lens 7 of the 30 wedge 6, and photoelectrically converted by the Iuz 1010 detector, similar to the light beam 1, so that electrical signals are obtained to obtain the information signal and servosignal (focus error signal for focus control, that is, focus signal and alignment signal for alignment control). If an amplifier circuit is incorporated in the light detector 10, satisfactory information signals are obtained with a high signal to noise ratio (Y / N), and miniaturization and thinning of the optical head device and stability are obtained.

In addition, in order to reproduce or record a third optical disc (e.g. DVD) with an intermediate recording density of the two types of optical discs, the third red light source is arranged in the vicinity of the light source 12, and a ray divider arranged in the vicinity of the light source 12 may be arranged to combine the light paths with the infrared light source, but if the light source 12 is a two wavelength light source to emit the beam. With two wavelengths, red light and infrared light, the beam splitter is unnecessary and the number of components is reduced. The irradiated red light beam 15 of the light source 12 reaches the objective lens 9, similar to the red light, and passes through the transparent base material, about 0.6 mm, and converges on the recording surface of the light. optical disc, such as DVD, by objective lens 9. Similarly to the red light, the light ray 20 reflected by the recording surface of the optical disc follows the original light path in the opposite direction and the light 10 detector produces electrical signals. , for the information signal and servosignal (focus error signal for focus control, and alignment signal for alignment control).

In general, in order to branch the light path, a cube-type splitter may be used, in which two transparent, triangular members are connected, but the number of components may be reduced if a parallel flat plate is used or wedge, as in the present application, and the material cost is reduced. If the single limb beam splitter is arranged in a non-parallel light path from the light source to the objective light-transmitting lens, the wedge 6, as shown in Figure 12, is used to prevent astigmatism production, and the angle of incidence of the optical axis is desirably less than 45 degrees. An aberration may still occur due to manufacturing errors even if the above is taken into account. Thus, in the example shown in Figure 1 of the present application, the light ray 2 to be converged on the highest density optical disc is reflected without transmission through any of the ray splitters in the non-parallel light path of the light source

1 for the collimator lens 7. Thus, satisfactory signal reproduction and signal recording can be performed on the highest density optical disc, such as BD.

Objective lens 9 is fixed at a predetermined position of the activator (not shown) to microscopically move the objective lens. An objective lens drive device (objective lens activator) is capable of microscopically moving objective lens 9 in both the Z-focus direction, orthogonal to the recording surface of the optical disc, and the Y-alignment direction of the optical disc. When using objective lens 9 with 0.85 NA or larger numerical aperture for BD playback or recording and the like, a spherical aberration is significantly produced with respect to the thickness of the transparent base material filled with the surface, whereby the Iuz enters the optical disc up to the information recording surface when recording or playing back the optical disc as the numerical aperture is large. In the present example, the degree of scattering convergence of the light from the collimating lens 7 to the objective lens 9 is modified by moving the collimating lens 7 towards the optical axis of the collimating lens 7. When the degree of scattering convergence of the light entering the objective lens changes, the spherical aberration changes, and thus the spherical aberration, which originates from the thickness difference of the base material, is corrected using the same. The optical head device shown in Figure 12 is arranged with a drive device 11 to move the collimator lens 7 towards the optical axis of the collimator lens 7. Specifically, a stepped motor, a brushless motor or the like is used as drive device 11. A holder 17 for supporting the collimating lens 7, a guide shaft for guiding movement of the holder 17, and a gear (not shown) for transmitting the drive force of the drive motor 11 to the holder 17 are arranged in the optical head device. The holder 17 for holding the collimating lens 7 may be molded in one piece with the collimating lens 7, the number of components of the optical head device being reduced if molded in one piece.

The collimating lens 7 is prevented from unintentional movement with respect to the inertial force by acceleration and deceleration speed when the entire optical head device is moved in the inner and outer peripheral direction of the optical disc while maintaining the optical axis of the optic disc. collimating lens 7 not parallel to the Y axis as in the present application.

Objective lens 25 converges infrared light 15 at the innermost peripheral part, near the optical axis, through the 1.2 mm transparent base material of the low density optical disc 28, such as a CD. The objective lens 25 also converges the red light 14 to 15 to the central peripheral portion of a wider scope than the innermost peripheral portion through the about 0.6 mm transparent base material of the optical disc 27. , such as a DVD. Objective lens 25 converges the blue Light 2 within the effective diameter through about 0.1 mm or thin transparent base material from the high density optical disc 26, such as a BD.

Therefore, in order to converge the respective light passed through the transparent base material of different thicknesses, the diffractive element is effectively used as described in patent document 6 (Japanese Publication No. 7-98431). The diffractive element has the configuration of the innermost peripheral portion, with the central peripheral portion and the outermost peripheral portion being discontinuous, so that the innermost peripheral portion converges through the base material of any thickness, and the outermost peripheral portion converges only when transmitted through 0.1 mm or thinner base material. As an example, configuration is facilitated using the light source of different wavelengths as described above. The CD uses infrared light, DVD uses red light, and BD uses blue light, and spherical aberration correction due to the thickness of the base material and limited aperture change of disc type are obtained using the fact that The diffraction angle of a diffracted primary diffracted element differs depending on wavelength.

5 Figure 13 shows an example of a division of a region.

Iuz detector 1010 detector suitable for detecting the focus error signal by the astigmatism method. Figure 13 shows a pattern seen across the surface from which the light ray of the Iuz 1010 detector enters. The Iuz receptor regions 20, 21, 22, 23, 24, 2510 are indicated with the same. reference numbers for parts that function in the same way as the light detector 1000 of figure 11 with respect to the red light and infrared light. The light receiving region 20 is divided into four, and detects the focus error signal using astigmatism formed by the parallel flat plate 3. The alignment signal by the so-called phase difference method and push-pull method can also be obtained. The receiving regions of Iuz 21, 22 receive the diffracted sub-radius when the red Iuz passes through the diffractive element 13. Differential push-pull alignment error signal is detected by calculation with the push-pull region signal receiver 20. The focus error signal from the

The astigmatism method is detected by the Iuz receptor regions 21, 22 and calculated with the focus error signal obtained from the Iuz 20 receptor region to perform the differential astigmatism method of removing the cross action by the alignment signal. By arranging the diffractive element between the light source 1 and the parallel flat plate 3, the sub beam signal can be detected by the light receiving regions 21, 22 in the blue light, similar to the red light.

The light receiving regions 23, 24, 25 receive infrared light. The center-to-center distance of the receiving regions of Iuz 20 and 23 is adjusted to the distance obtained by multiplying a magnification ratio performed by the relay lens 5 to the distance from the red-to-infrared I-light-emitting point in the light. light source 12. Assuming that the center-to-center distance of the Iuz 20 and 21 receptor regions is L1, and the center-to-center distance of the Iuz 23, 24 receptor regions is L2, the ratio of L1 to L2 is adjusted to be equal. to the wavelength ratio of red light: infrared light wavelength. The light receiving region 23 is divided into four, and the 5 focus error signal is detected using astigmatism formed by the parallel flat plate 3. The alignment signal by the so-called phase difference method and push-pull method can also be obtained. . The light receiving regions 24, 25 receive the refracted sub-radius when the infrared light passes through the diffractive element 13. The alignment signal by the differential push-pull method 10 is detected by calculation with the push-pull signal of the receiving region. 23. In the present application, the diffractive element described in the previous embodiments, such as diffractive element 31, 3100, is used as diffractive element 13. Thus, an effect of satisfying both the obtaining of the alignment error signal by the DPP method, suitable for optical disc 15 with varying track inclination degrees, using a single diffractive element, and suppressing the reducing amount in the alignment error signal amplitude, in a state in which the objective lens is moved by Track tracking.

The number of semiconductor component components is reduced by arranging a plurality of Iuz receptor regions on a single Iuz detector or a single semiconductor chip and photoelectrically converting the different wavelengths.

(Optical Information Device)

In addition, an exemplary configuration of the optical information apparatus using the optical head device of the present invention is shown in Figure 14. In Figure 14, the optical discs 26, 27, 28 are arranged on a turntable 182. and driven by a motor 164. The optical head device shown in Figure 12 is used for the optical head device 155. The optical head device 155 is moved by the optical head device driver 151 to a track where The desired information is present on the optical disc.

Optical head device 155 provides the focus error (focus error) or alignment error signal to an electrical circuit 153 in correspondence with the positional relationship with the optical disc 26. The electrical circuit 153 provides a signal to microscopically moving the objective lens to the optical head device 155 in response to the 5 focus error signal or alignment error signal. In response to the signal, the optical head device 155 performs focus control and alignment control on the optical disc, and also reads, writes (writes), or removes information with respect to the optical head device 155.

The optical information apparatus 157 of the present embodiment is mounted with the optical head device shown in Figure 12 and thus has the advantage of stably recording or reproducing on a plurality of optical discs of different recording density with a Single head optical device.

(Computer)

The computer mounted with the optical information device

167, shown in figure 14, is now described. The computer, optical disc player, or optical disc recorder, mounted with the optical information apparatus of Figure 14, or by adopting the record and playback method described above, records or stably reproduces optical discs of different types 20 and It can therefore be used for a wide range of applications.

In Figure 15, a computer 300, including optical information device 167, shown in Figure 14, an input device 365, such as a keyboard, mouse, and touch panel for entering information, 25 an arithmetic device 364, such as a central processing unit (CPU) for performing input-based information input calculations and read information from the optical information device 167, and an output device 361 such as a Braun tube, input device liquid crystal display, and printer for displaying information, 30 as the result of calculations by the arithmetic device.

(Optical disc player)

The frame format configuration of the optical disc player mounted with the optical information device shown in Figure 14 is shown in Figure 16. In Figure 16 the optical disc player 321 which includes the optical information device 167 14 is shown, and an information-image conversion device (e.g., decoder 366) for converting information signals obtained from the optical information apparatus into images is configured. This setting is also used as a car navigation system by adding a position sensor such as a GPS and a central processing device (CPU). A mode added to display device 320, such as a liquid crystal monitor, is also possible.

(Optical Disc Recorder)

The frame format configuration of the optical disc recorder mounted with the optical information device shown in figure 14 is shown in figure 17. The optical disc recorder shown in figure 17 includes an optical information device 167 shown in FIG. 14 is an information-image conversion device (e.g., decoder 366) for converting information signals obtained from the optical information apparatus into images. Output device 361, such as a Braun tube, liquid crystal display device, printer and the like 20 for displaying information, may also be arranged.

(Vehicle)

The vehicle mounted with the optical information device 167 shown in Figure 14 is now described. The frame-shaped configuration of the vehicle mounted with the optical information device shown in Figure 14 is shown in Figure 18. Figure 18 , optical information device 167 is optical information device 167 of FIG. 14. Vehicle body 131 is mounted with optical information device 167. An energy generating unit 134 and a fuel storage unit 135 for storing The fuel to be supplied to the power generating unit 134 and / or a power supply 136 is also disposed on the vehicle body 131. Therefore, information can be stably obtained from various types of optical discs while in the moving body by mounting Optical Information Device 167 of this application on the vehicle body. Alternatively, the information can be recorded. The vehicle body 131 further includes wheels 133 for displacement in the case of a train or car. In the case of a car,

5 a lever 130 is provided for changing directions.

In addition, a large number of optical discs can easily be used by mounting an exchange device 138 or an optical disc housing unit 139 on the vehicle body 131. An arithmetic device 164, for processing the information obtained from the optical disc, to obtain an image, a semiconductor memory 137 for temporarily storing the information, and a display device 142 may be provided to enable reproduction of optical disc image information. Audio and music can be reproduced from the optical disc with an amplifier 140 and a speaker 141. With a positional sensor, such as a GPS 132, along with the reproduced map information of the optical disc, the current position and the direction of advance. can be recognized as an image displayed on the display device 142 or audio output from the speaker 141. In addition, information can be received from outside and used in addition to optical disc information by having a wireless communication unit 143.

Output device 361 and liquid crystal display monitor 320 are shown in Figures 15, 16 and 17, but output terminals may be provided, where output device 361 and liquid crystal monitor 320 may obviously be in modes. of product sold separates

without being disposed within. The input device is not shown in figures 16 and 17, but a product mode equipped with the input device such as keyboard, touch panel, mouse, remote control device and the like is also possible. may be sold separately, and may be in a mode that includes only the 30 input terminals.

Industrial Applicability

The optical head device according to the present invention can record and play back on a plurality of optical disc types, with different base material thickness, response wavelength, recording density, and the like, and an information apparatus. Compatible optical media, which uses the optical head device, can handle optical discs of various types, such as CD, DVD, and BD. Therefore, the application can be expanded to various systems for storing information such as computer, optical disc player, optical disc recorder, car navigation system, editing system, data server, AV component, vehicle and the like.

The respective advantages are obtained by combining, appropriate

arbitrary modalities of the various modalities described above.

While the present invention has been fully described in connection with preferred embodiments thereof, with reference to the accompanying drawings, it should be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be construed as falling within the scope of the present invention as defined by the appended claims, unless they differ from them.

Claims (36)

1. Optical head device, comprising: a light source; a diffractive element for branching a light output from the light source into at least three light streams, including a main beam, which is transmitted without being diffracted, and two sub-rays, which are diffracted; an objective lens for converging the three Iuz streams onto a recording surface of an optical disc; and a light detector for receiving the light converged on the recording surface of the optical disc by the objective lens and reflected by the optical disc and photoelectrically converting the light into an electrical signal, the diffractive element being divided into a first network region. diffraction, a second diffraction grating region, formed with a second diffraction grating, with a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first diffraction grating region, and a central region, nested between the first diffraction grating region and the second diffraction grating region; the central region is further divided into a plurality of regions divided by a virtual dividing line; and the central region has different grid phases or vectors than the first diffraction grating region and the second diffraction grating region, and the divided regions divided by the dividing line are formed by diffraction grating, phase grating and grid vector. different from each other. Optical head device according to claim 1, wherein the dividing line for dividing the central region extending in an orthogonal direction to an extension direction of an optical disc track groove. Optical head device according to claim 1, wherein the central region is divided into three or more divided regions. Optical head device according to claim 3, wherein the diffraction grids have different phases from each other are formed in two divided regions of the three or more divided regions of the central region; and a diffraction grating with the same grating vector and the same phase as the diffraction grating formed in one of the two divided regions is formed in at least one divided region of a remaining divided region. Optical head device according to claim 1, wherein when the phase of the first diffraction grating formed in the first region of the diffraction grating is 0 degree as a reference, the phase of a third diffraction grating formed in the region Divided, obtained by dividing the central region and the phase of a fourth diffraction grating, formed in another divided region, have opposite polarities, but the same absolute value. Optical head device according to claim 5, wherein when the phase of the first diffraction grating formed in the first divided region is 0 degree as a reference, the phase of the third diffraction grating is 90 degrees, and the phase of the fourth diffraction grating is -90 degrees. Optical head device according to claim 1, wherein the phase of the first diffraction grating formed in the first diffraction grating region is 0 degree by reference, the phase of each diffraction grating formed in each divided region from the central region is, on average, substantially 0 degree. Optical head device according to claim 3, wherein when the phase of the first diffraction grating formed in the first divided region is 0 degree by reference, the central region is divided into four or more divided regions, and includes a -120 degree diffraction grating, a -60 degree diffraction grating, a +60 degree diffraction grating and a diffraction grating +120 degrees. 9. Optical head device, comprising: a light source; a diffractive element for branching a light output from the light source into at least three light streams; an objective lens for converging the three light streams onto a recording surface of an optical disc; and a light detector for receiving the light converged on the recording surface of the optical disc by the objective lens and reflected by the optical disc and photoelectrically converting the light into an electrical signal, the diffractive element being divided into a first network region. diffraction, a second diffraction grating region, formed with a second diffraction grating with a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first diffraction grating region, and a central region embedded in it. between the first diffraction grating region and the second diffraction grating region; and a diffraction grating with a different direction from the first diffraction grating and the second diffraction grating is formed in the central region. Optical head device according to claim 8, wherein a third diffraction grating formed in the split region obtained by dividing the central region and a fourth diffraction grating formed in another divided region are diffraction grids having a direction differing from the first diffraction grating and the second diffraction grating and have an angle formed with an extension direction of an optical disc track groove of opposite signals relative to one another. An optical head device comprising: a light source; a diffractive element for branching a light output from the light source into at least three light streams; an objective lens for converging the three light streams onto a recording surface of an optical disc; and a light detector for receiving the light converged on the recording surface of the optical disc by the objective lens and reflected by the optical disc and photoelectrically converting the light into an electrical signal, the diffractive element being divided into a first network region. diffraction, a second diffraction grating region formed with a second diffraction grating with a phase differing substantially 180 degrees from a first diffraction grating arranged in the first diffraction grating region, and a central region nested between the first diffraction grating region and the second diffraction grating region; and a diffraction grating having a degree of inclination of grating different from the first diffraction grating and the second diffraction grating is formed in the central region. Optical head device according to claim 10, wherein a diffraction grating formed in the central region is a diffraction grating having a lower degree of inclination than the first diffraction grating and the second diffraction grating. Optical head device according to one of claims 1, 9 and 11, wherein the width of the central region is 1% to 40% of a projection diameter over the diffractive element of an effective diameter of an objective lens. Optical head device according to one of claims 1, 9 and 11, wherein the light source is a light source with two wavelengths for emitting a red light and an infrared light. Optical head device according to claim 14, wherein the width of the central region is less than or equal to 30% of a projection diameter over the diffractive element of an effective aperture diameter of the objective lens. Optical head device according to one of claims 1, 9 and 11, further comprising a blue light source. 17. A diffractive element mounted on an optical head device including a light source, an objective lens for converging a light output from the light source onto an optical disc recording surface, and a light detector for receiving the converged light on the recording surface of the optical disc by the objective lens and reflected by the optical disc and convert the light to an electrical signal, the diffractive element branches the light output of the light source into at least three light streams, including a beam which is transmitted without being diffracted, and two sub-rays which are diffracted, wherein the diffractive element is divided into a first diffraction grating region, a second diffraction grating region formed with a second diffraction grating. with a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first diffraction grating region and a central region nested between the first diffraction grating region and the second diffraction grating region; and the central region has different grid phases or vectors than the first diffraction grating region and the second diffraction grating region, and the divided regions divided by the dividing line are formed by diffraction grating, phase grating and grid vector. different from each other. The diffractive element of claim 17, wherein the dividing line for dividing the central region extends in an orthogonal direction to an extension direction of a track groove of the optical disc. The diffractive element of claim 17, wherein the central region is divided into three or more divided regions. A diffractive element according to claim 19, wherein diffraction networks with different phases from one another are formed in two divided regions of the three or more divided regions of the central region; and a diffraction grating of the same grating vector and the same phase as the diffraction grating formed in one of the two divided regions is formed in at least one divided region of a remaining divided region. The diffractive element of claim 17, wherein the phase of the first diffraction grating formed in the first region of the diffraction grating is 0 degree as a reference, the phase of a third diffraction grating formed in the region divided, obtained by dividing the central region, and the phase of a fourth diffraction grating, formed in another divided region, have opposite polarities, but the same absolute value. The diffractive element of claim 21, wherein the phase of the first diffraction grating formed in the first divided region is 0 degree as a reference, the phase of the third diffraction grating is 90 degrees, and the phase of the fourth diffraction grating is -90 degrees. The diffractive element of claim 17, wherein when the phase of the first diffraction grating formed in the first region of the diffraction grating is 0 degree as a reference, the phase of each diffraction grating formed in each divided region of the central region is substantially 0 degree on average. The diffractive element of claim 20, wherein when the phase of the first diffraction grating formed in the first divided region is 0 degree as a reference, the central region is divided into three or more divided regions to form a -120 degree phase diffraction grating, -60 degree phase diffraction grating, +60 degree phase diffraction grating, and +120 degree phase diffraction grating. 25. Diffractive element mounted on an optical head device including a light source, an objective lens for converging a light output from the light source onto an optical disc recording surface, and a light detector for receiving the converged light on the recording surface of the optical disc by the objective lens and reflected by the optical disc and convert the light to an electrical signal, the diffractive element branches the light output of the light source into at least three light streams, including a beam which is transmitted without being diffracted, and two sub-rays which are diffracted, wherein the diffractive element is divided into a first diffraction grating region, a second diffraction grating region formed with a second diffraction grating. with a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first diffraction grating region and a central region nested between the first diffraction grating region and the second diffraction grating region; and a diffraction grating, with a different direction from the first diffraction grating and the second diffraction grating, is formed in the central region. A diffractive element according to claim 17, wherein a third diffraction grating formed in the split region obtained by dividing the central region and a fourth diffraction grating formed in another divided region are one-direction diffraction grating. different from the first diffraction grating and the second diffraction grating and have an angle formed with an extension direction of an optical disc track groove of opposite signals relative to one another. 27. A diffractive element mounted on an optical head device comprising a light source, an objective lens for converging the three light streams onto a recording surface of an optical disc, and a light detector for receiving the converged light on the recording surface of the optical disc by the objective lens and reflected by the optical disc and photoelectrically convert the light to an electrical signal, the diffractive element branches the light output of the light source into at least three light streams, including a main beam , which is transmitted without being diffracted, and two sub-rays, which are diffracted; wherein the diffractive element is divided into a first diffraction grating region, a second diffraction grating region formed with a second diffraction grating having a phase that differs substantially 180 degrees from a first diffraction grating arranged in the first diffraction grating region, and a central region nested between the first diffraction grating region and the second diffraction grating region; and a diffraction grating having a different degree of inclination from the first diffraction grating and the second diffraction grating is formed in the central region. A diffractive element according to claim 17, wherein a diffraction grating formed in the central region is a diffraction grating having a lesser degree of inclination than the first diffraction grating and the second diffraction grating. Optical information apparatus, comprising: the optical head device as defined in one of claims 1 to 16; an engine for rotating an optical disc; and an electrical circuit for receiving a signal obtained from the optical head device, and controlling and driving the motor, an optical lens, and a signal-based laser light source. Optical information apparatus according to claim 29, wherein a push-pull signal obtained by receiving the lightning-beam sub-ray and calculating it by photoelectric conversion is amplified to an amplification factor of factor K1, and subtracted with a push-pull signal obtained by receiving the lightning beam from the light detector and which is processed by photoelectric conversion for use as an alignment error signal; and the amplification factor K1 being fixed after being adjusted to a value at which the change in control of the alignment signal becomes smaller when the objective lens is moved in a direction perpendicular to a groove extension direction. of optical disc track. Optical information apparatus according to claim 29, wherein a focus error signal, obtained by receiving the subgrade at the Iuz detector and calculating by photoelectric conversion, is amplified to an amplification factor of factor K2, and added to the focus error signal, obtained by receiving the lightning bolt from the light detector and which is processed by photoelectric conversion, to be used as a focus error signal for focus control. A computer, comprising: the optical information apparatus as defined in claim 29; an input device or input terminal for entering information; an arithmetic device for performing an arithmetic operation based on the input device input or reproduced information from the optical information device; and an output device or output terminal for displaying or issuing input information by the input device or information reproduced by the optical information device, or the result of an arithmetic operation performed by the arithmetic device. Optical disc player comprising: the optical information apparatus of claim 29; and an image information decoder for converting an information signal obtained from the optical information device into an image. A car navigation system comprising: the optical information apparatus as defined in claim 29; an information-decoder for converting an information signal obtained from the optical information device into an image; and a position sensor. Optical disc recorder, comprising: the optical information apparatus as defined in claim 29; and an image information encoder for converting image information into information to be recorded by the optical information device. Vehicle comprising the optical information apparatus as defined in claim 29, a vehicle body mounted with the optical information apparatus, and a power generating unit for generating energy for moving the vehicle body.