WO2010131461A1

WO2010131461A1 - Optical head apparatus, light receiving element, integrated circuit, photonic integrated element, optical disc apparatus, and signal detection method

Info

Publication number: WO2010131461A1
Application number: PCT/JP2010/003212
Authority: WO
Inventors: 山本博昭
Original assignee: パナソニック株式会社
Priority date: 2009-05-15
Filing date: 2010-05-12
Publication date: 2010-11-18
Also published as: JP2010267348A

Abstract

Disclosed is a low cost optical head apparatus capable of generating good reproduced signals. The optical head apparatus is provided with a semiconductor laser element (30), a light receiving element (40), and a hologram element (20). At a first diffraction region (261a) of the hologram element (20), a grating pattern is formed which converts light returning from an optical disc (10) to light spread over a second light reception dividing line (L72) at a first light receiving region group (451) and emitted to a first light-receiving region (451a) and second light receiving region (451b) with a coma aberration in the X-direction. At a third diffraction region (262a), a grating pattern is formed which converts light returning from the optical disc (10) to light spread over the second light reception dividing line (L72) at a second light receiving region group (452) and emitted to a third light receiving region (452a) and fourth light receiving region (452b) with a coma aberration opposite to the polarity of the first diffraction region (261a).

Description

Optical head device, light receiving element, integrated circuit, optical integrated element, optical disk device, and signal detection method

The present invention relates to an optical head device for recording / reproducing / erasing information on a recording medium by light, a light receiving element, an integrated circuit, an optical integrated element, an optical disc device, and a signal detection method.

In optical information recording including an optical disk, tracking control for controlling a light spot at a desired recording and reproducing position is an indispensable technique. There is a push-pull method as a method of detecting a tracking error signal used for this tracking control. The push-pull method can be realized by an optical system having a simple configuration, and is widely employed in an optical head device (hereinafter, also simply referred to as an “optical head”).

However, the push-pull method has a disadvantage that the tracking error signal is offset as the objective lens moves in the tracking direction. Patent Document 1 discloses a technique for compensating for this defect.

FIG. 14 is a block diagram of an optical head device in Patent Document 1, and FIG. 15 is a schematic top view of a composite diffraction element.

FIG. 14 shows an optical disc 10 as an information recording medium, an objective lens 12, a hologram element 20, a semiconductor laser element 30, and a light receiving element 40. Each arrow in the figure indicates the direction in which light travels. FIG. 15 is a top view of the hologram element 20 shown in FIG. In the figure, L8a to L8c indicate area dividing lines, 25a to 25f indicate divided areas, R0 indicates a light beam passing through the hologram element 20, R1 and R2 indicate light beams diffracted by the track of the optical disk 10 There is. FIG. 16 is a top view of the light receiving element 40. FIG. In the figure, 45a to 45d are light receiving areas, and 46 to 49 are light receiving area groups, each of which comprises light receiving areas 46a to 46c, light receiving areas 47a to 47c, light receiving areas 48a to 48c, and light receiving areas 49a to 49c. The figure written inside each light receiving element is a thing which shows typically the shape of the light ray which injects there. The signals detected by the respective light receiving areas generate a tracking error signal and a focus error signal in the arithmetic circuit of the circuit configuration shown in FIG. In the drawing, a circuit denoted by IV is a head amplifier (current-voltage conversion amplifier), a circuit denoted by K is an amplifier of gain K, and the other circuits are addition or subtraction circuits.

The operation of the optical head device of this configuration will be described below. The light emitted from the semiconductor laser element 30 passes through the hologram element 20 and is condensed on the information recording surface of the optical disc 10 by the objective lens 12. An information track is formed on the information recording surface of the optical disk 10, and the direction of the information track is assumed to be a direction perpendicular to the paper surface in FIG. After passing through the objective lens 12, the reflected light from the optical disk 10 again converges toward the vicinity of the semiconductor laser device 30 and advances while entering the hologram device 20. The luminous fluxes passing through the respective regions divided by the region dividing line L8c from the region dividing line L8a of the hologram element 20 are transmitted as + 1st order, 0th order and -1st order diffracted light. Among the transmitted light, + 1st order and -1st order diffracted lights are diffracted toward the corresponding light receiving areas.

Diffracted light in the

regions

25a and 25e of the hologram element 20, for example, in the light receiving region 45a and the light receiving region 45d, and diffracted light in the

regions

25b and 25f, for example, in the light receiving region 45b and the light receiving region 45c, diffracted light in the region 25c For example, diffracted light in the region 25d enters, for example, the light receiving region group 47 and the light receiving region group 49, for example. At this time, for example, a light flux entering the light receiving area group 47 and the light receiving area group 49 focuses on a place farther than the light receiving element, and a light flux entering the light receiving area group 46 and the light receiving area group 48 receives the light receiving element Focusing is closer to the hologram element 20. Furthermore, when the optical disk 10 is in focus of the objective lens 12, the light receiving area group 46, the light receiving area group 47, the light receiving area group 48 and the light receiving area group 49 in the direction orthogonal to the dividing line of the light receiving elements of the light beams. When the refractive power of the lens is given to the diffraction grating patterns of the

regions

25c and 25d of the hologram element 20 so that the lengths become substantially equal, the light flux on each light receiving element group according to the focal point shift of the objective lens 12 Because the size of each changes to a different size,
FE = 46a + 46c + 47b + 48a + 48c + 49b-(46b + 47a + 47c + 48b + 49a + 49c)
The focus error signal FE is obtained by the following calculation.

Here, the detection signal name is represented by the light receiving area name. Hereinafter, unless otherwise noted, the detection signal name is referred to as the light receiving area name in which the signal is detected.

The push-pull signal TE1 detects a light flux that has passed through the area between the area dividing line L8b of the hologram element 20 and the area dividing line L8c,
TE1 = (47a + 47b + 47c + 48a + 48b + 48c)-(46a + 46b + 46c + 49a + 49b + 49c)
It is obtained by

Further, a signal TE2 which is generated when the objective lens 12 moves in a direction orthogonal to the information track and which corrects the tracking offset is a light beam which has passed through the area outside the area dividing line L8b of the hologram element 20 and the area dividing line L8c. Detect
TE2 = 45a + 45d-(45b + 45c)
It is obtained by Therefore, the tracking error signal TE in which the offset generated with the movement of the objective lens has been corrected is TE = TE1-k * TE2 with the correction coefficient k.
Can be obtained by

These operations can be obtained by the operation circuit of FIG. Although not shown in FIG. 17, the signal (RF signal) for reading the recording information is detected by the sum of the signals from all the light receiving areas.

Japanese Patent Application Laid-Open No. 11-73658

However, in the conventional configuration, six head amplifiers are required to detect the FE signal and the tracking error signal. For this reason, there is also a problem that the circuit scale becomes large and the cost becomes high. Further, there is a problem that noise generated in the head amplifier also increases in proportion to the number of head amplifiers and the reproduction signal is deteriorated.

Furthermore, in systems such as DVD and BD, detection of a tracking error signal of a read-only disc (ROM disc) requires detection of a phase difference tracking error signal (DPD signal), but this configuration can not detect this signal. It is necessary to divide the light receiving area, and the number of head amplifiers is required to be 12 times as many, resulting in an increase in cost and a problem of noise increase, which is difficult to realize.

As described above, in the conventional optical head device, there is a problem of cost increase due to the increase of the head amplifier and deterioration of the reproduction signal.

Therefore, the present invention solves such problems, and an optical head device, a light receiving element, an integrated circuit, an optical integrated device, an optical disk device, and a signal detecting method capable of generating a good reproduction signal at low cost. Intended to provide.

In order to achieve the above object, an optical disk apparatus according to an embodiment of the present invention comprises: a light source for emitting a light beam; and a focusing optical system for receiving the light beam and converging it to a minute spot on an information medium having a track. An optical head device comprising: a hologram element for diffracting the light beam reflected by the information medium; and a light receiving element for receiving light diffracted by the hologram element, the light receiving element comprising at least A first light receiving area, a second light receiving area, a third light receiving area, and a fourth light receiving area, and the first light receiving area and the second light receiving area The third light receiving area and the fourth light receiving area are disposed to face each other with the second light receiving division line interposed therebetween, and the hologram element is disposed to Diffraction region and second diffraction region And a second diffraction area group having a third diffraction area and a fourth diffraction area, and the first diffraction area group and the second diffraction area group have A first area division line passing through a center of an optical axis of the focusing optical system, the first diffraction area and the third diffraction area being reflected and diffracted by the track of the information medium And a second incident area on which the first order light is incident, wherein the second diffraction area and the third diffraction area are tracks of the information medium. The light incident on the first incident area is incident on the second light receiving area, and the second light receiving area includes the third incident area on which only undiffracted light is incident. A light having a first wavefront in which light incident on an incident area is incident on the first light receiving area A grating pattern for generating light is formed, and in the second diffraction area, diffracted light having a second wave front in which light incident on the third incident area is incident on the third light receiving area is generated In the third diffraction area, light incident on the first incident area is incident on the fourth light receiving area, and light incident on the second incident area is incident on the third diffraction area. A grating pattern for generating diffracted light having a third wavefront incident on the third light receiving area is formed, and the light incident on the third incident area is the second on the fourth diffraction area. A grating pattern is formed to generate diffracted light having a fourth wavefront incident on the light receiving region.

Thereby, the signal A from the first light receiving area 451a, the signal B from the second light receiving area 451b, the signal C from the third light receiving area 452a, and the signal D from the fourth light receiving area 452b When K is a constant, the tracking error signal TE can be easily detected by the following operation.

TE1 = (A + C)-(B + D)
TE2 = (A + B)-(C + D)
TE = TE1-K · TE2

Further, the focus error signal FE can be easily generated by the following operation using the signal A, the signal B, the signal C, and the signal D.

FE = (A + D)-(B + C)

Furthermore, using the signals A, B, C, and D, a phase difference tracking error signal can also be generated by the phase difference between the (A + D) and (B + C) signals.

Further, the signal recorded on the information medium may be detected by the sum of the signal A, the signal B, the signal C and the signal D.

The present invention is not only realized as the above optical head device, but is a light receiving element used for the above optical head device, and at least the first light receiving region, the second light receiving region, and the third light receiving region It has a fourth light receiving area, and the first light receiving area and the second light receiving area are disposed to face each other across the first light receiving division line, and the third light receiving area and the second light receiving area The fourth light receiving area is disposed to face the second light receiving division line, and the second light receiving area is the sum of the signal from the first light receiving area and the signal from the third light receiving area, and the second light receiving area. A circuit for generating a first signal obtained by the difference between the signal from the light receiving area and the sum of the signals from the fourth light receiving area; the signal from the first light receiving area and the second light receiving A sum of signals from the area, a signal from the third light receiving area, and the fourth light receiving area May also be implemented as a light-receiving element; and a circuit for generating a second signal obtained by the differential between the sum of al the signal.

Further, according to the present invention, there is provided an integrated circuit for processing a signal from the optical head device, wherein the signal A from the first light receiving area, the signal B from the second light receiving area, and the third one. Assuming that K is a constant, using the signal C from the light receiving area and the signal D from the fourth light receiving area,
TE1 = (A + C)-(B + D)
TE2 = (A + B)-(C + D)
TE = TE1-K · TE2
It can also be realized as an integrated circuit having a circuit that generates the tracking error signal TE obtained in

Further, according to the present invention, there are provided a light source for emitting a light beam, a focusing optical system for receiving the light beam and converging the light beam on an information medium having a track, and diffracting the light beam reflected by the information medium. An optical head device comprising a hologram element for causing light to be received and a light receiving element for receiving light diffracted by the hologram element, the light receiving element comprising at least a first light receiving area and a second light receiving area. A light receiving area, a third light receiving area, and a fourth light receiving area are provided, and the first light receiving area and the second light receiving area are disposed opposite to each other with the first light receiving division line interposed therebetween. The third light receiving area and the fourth light receiving area are disposed to face each other with the second light receiving division line interposed therebetween, and the hologram element has a first diffraction area and a second diffraction area. A first group of diffraction areas having an area; A second diffraction region group having a fourth diffraction region and the first diffraction region group, and the first diffraction region group and the second diffraction region group pass through the optical axis center of the condensing optical system; The first diffraction area and the third diffraction area are arranged on both sides of the area division line of 1, and the first incident light to which the −1st order light reflected and diffracted by the track of the information medium is incident An area and a second incident area on which +1 order light is incident, wherein the second diffraction area and the third diffraction area are the third incident area on which only light not diffracted by the track of the information medium is incident In the first diffraction area grating pattern, the light incident on the first incident area is incident on the second light receiving area, and the light incident on the second incident area is the first Generating diffracted light having a first wavefront incident on the light receiving area of The light incident on the third incident area generates diffracted light having a second wave front that is incident on the third light receiving area, and the grating pattern of the third diffraction area is generated. Then, the light incident on the first incident area is incident on the fourth light receiving area, and the third incident light on the second incident area is incident on the third light receiving area. To generate the diffracted light having the fourth wavefront in which the light incident on the third incident area is incident on the second light receiving area in the grating pattern of the fourth diffracted area It can also be realized as a signal detection method characterized by the above.

Further, according to the present invention, there is provided an optical integrated device including a light source for emitting a light beam, a hologram element for diffracting the light beam reflected by an information medium, and a light receiving element for receiving light diffracted by the hologram element. The light receiving element has at least a first light receiving area, a second light receiving area, a third light receiving area, and a fourth light receiving area, and the first light receiving area and the second light receiving The regions are disposed opposite to each other across the first light receiving division line, and the third light receiving region and the fourth light receiving region are disposed opposite to each other with the second light reception division line interposed therebetween. And the hologram element has a first diffraction area group having a first diffraction area and a second diffraction area, and a second diffraction area group having a third diffraction area and a fourth diffraction area. And the first diffraction area group and the second diffraction area group are The first area dividing line which passes through the center of the optical axis of the system is disposed, and the first diffraction area and the third diffraction area are -1st-order reflected and diffracted by the track of the information medium. A first incident area where light is incident and a second incident area where + first order light is incident, wherein the second diffraction area and the third diffraction area are only light that is not diffracted by the track of the information medium The light incident on the first incident area is incident on the second light receiving area and incident on the second incident area. The grating pattern is formed to generate diffracted light having a first wavefront in which the incident light enters the first light receiving area, and the light incident to the third incident area is formed in the second diffraction area. The diffracted light having the second wave front incident on the third light receiving area is A grating pattern to be produced is formed, and in the third diffraction region, the light incident on the first incident region is incident on the fourth light receiving region, and the light incident on the second incident region A grating pattern is formed to generate diffracted light having a third wave front that is incident on the third light receiving area, and the light incident on the third incident area is The present invention can also be realized as an optical integrated device characterized in that a grating pattern for generating diffracted light having a fourth wavefront incident on the second light receiving area is formed.

Further, according to the present invention, there is provided an optical disk apparatus having the optical head device, wherein the signal A from the first light receiving area, the signal B from the second light receiving area, and the signal from the third light receiving area. Assuming that K is a constant, using the signal C and the signal D from the fourth light receiving area,
TE1 = (A + C)-(B + D)
TE2 = (A + B)-(C + D)
TE = TE1-K · TE2
The present invention can also be realized as an optical disk apparatus characterized by having a circuit that generates the tracking error signal TE obtained in the above.

According to the present invention, an optical head device, a light receiving element, an integrated circuit, an optical integrated element, an optical disc capable of detecting a push-pull signal with little influence of lens movement, obtaining a good reproduction signal at low cost and detecting DPD signal An apparatus and signal detection method are implemented.

FIG. 1 is a diagram showing the configuration of an optical head device according to Embodiment 1 of the present invention. FIG. 2 is a view showing a diffraction area of the hologram element in the first embodiment of the present invention. FIG. 3 is a diagram showing a light receiving area of the light receiving element in the first embodiment of the present invention. FIG. 4 is a diagram showing an arithmetic circuit according to the first embodiment of the present invention. 5 (a) to 5 (e) are spot diagrams on the light receiving element in the first embodiment of the present invention. FIG. 6 is a diagram showing a focus error signal in the first embodiment of the present invention. FIGS. 7A and 7B are diagrams showing the correspondence between the position of the hologram element and the spot position in the first embodiment of the present invention. FIG. 8 is a diagram showing a spot on the light receiving element 40 in the second embodiment of the present invention. FIG. 9 is a diagram showing the relationship between light receiving elements and spots in the third embodiment of the present invention. FIGS. 10 (a) to 10 (e) are diagrams showing spots on the light receiving element in the third embodiment of the present invention. FIG. 11 is a diagram showing a focus error signal in the third embodiment of the present invention. FIGS. 12 (a) and 12 (b) are diagrams showing the correspondence between the position of the hologram element and the spot position in the third embodiment of the present invention. FIG. 13 is a diagram showing the configuration of the optical disc device in the fourth embodiment of the present invention. FIG. 14 is a block diagram of a conventional optical head device. FIG. 15 is a schematic top view of a complex diffraction element of a conventional optical head device. FIG. 16 is a top view of the light receiving element 40 of the conventional optical head device. FIG. 17 is a diagram showing an arithmetic circuit of a conventional optical head device.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

Embodiment 1
FIG. 1 is a view schematically showing a configuration of an optical head device according to Embodiment 1 of the present invention.

The optical head device includes a semiconductor laser element 30 which is a light source for emitting a light beam toward an information medium (optical disc 10), a hologram element 20 which diffracts the light beam reflected by the information medium, and And a light receiving element 40 for receiving the reflected light. The semiconductor laser element 30 and the light receiving element 40 are closely fixed to the holder 741. The holding portion 741 is fixed in a desired positional relationship with the hologram element 20 via another holding portion (not shown). The other holding unit may be an optical bench of the optical head device, but a unit in which the hologram element 20, the semiconductor laser element 30, and the light receiving element 40 are integrated using a holding member different from the optical bench ) May be configured. The configuration of such a unit can stably configure the optical system.

The optical head device further has a collimator lens 11 and an objective lens 12. The collimator lens 11 and the objective lens 12 constitute a focusing optical system for focusing the laser light on the optical disk 10 which is an information medium. The optical head device further includes a lens drive mechanism (not shown) for driving and displacing the objective lens 12 in the optical axis direction (z direction) of the objective lens 12 and the radial direction (x direction) of the optical disc 10.

Hereinafter, unless otherwise noted, as shown in the figure, the direction of the optical axis of the condensing optical system is the Z-axis direction, the radial direction of the optical disc 10 is the X direction, and the track direction of the optical disc 10 The (tangential direction) is referred to as the Y direction. In the optical system of the optical head, even when the optical axis is bent by a mirror, a prism, or the like, the direction is defined based on the optical axis and the mapping of the optical disc 10.

First, the light beam emitted from the semiconductor laser element 30 of the optical head device of Embodiment 1 will be described. The light beam R0 emitted from the semiconductor laser element 30 is transmitted through the hologram element 20 and condensed on the information recording surface of the optical disc 10 by the collimator lens 11 and the objective lens 12. Reflected light from the optical disk 10 is converted by the objective lens 12 and the collimator lens 11 into light which converges to the light emitting point of the semiconductor laser device 30. This light is incident on the hologram element 20 and diffracted. The diffracted light is incident on the light receiving element 40, and the light receiving element 40 detects a signal.

Next, the diffraction area formed in the hologram element 20 and the light receiving area formed in the light receiving element 40 will be described in detail.

FIG. 2 is a view showing a diffraction area of the hologram element 20 in the present embodiment.

The grating pattern of the hologram element 20 is divided into a first diffraction area group 261 and a second diffraction area group 262 by a first area division line L11 which passes through substantially the center of the light beam and is parallel to the X-axis. The first diffraction area group 261 includes a second diffraction area 261b divided by a second area division line L12 substantially passing the center of the light beam and a third area division line L13 parallel to the X-axis and the other. It consists of a first diffraction area 261a. The second diffraction region group 262 is divided into a fourth diffraction region 262b divided by a second region division line L12 and a fourth region division line L14 parallel to X and a third diffraction region 262a other than that. It is divided. Note that R0 in the figure is the reflected light from the optical disc 10 incident on the hologram element 20. R1 and R2 are light diffracted by the optical disk 10, and generate light and dark according to the tracking position in the area interfering with R0, that is, the overlapping area. The third area dividing line L13 and the fourth area dividing line L14 are set outside this interference area.

FIG. 3 is a view showing a light receiving area of the light receiving element 40 in the present embodiment. The light receiving element 40 has a first light receiving area group 451 and a second light receiving area group 452. The first light receiving area group 451 is composed of a first light receiving area 451a and a second light receiving area 451b which are disposed opposite to each other with the first light receiving parting line L71 substantially parallel to the X-axis interposed therebetween. The second light receiving area group 452 includes a third light receiving area 452a and a fourth light receiving area 452b which are disposed to face each other with the second light receiving parting line L72 substantially parallel to the X-axis interposed therebetween.

In the first diffraction area 261a, the return light from the optical disc 10 is straddled across the second light reception division line L72 of the first light reception area group 451 into the first light reception area 451a and the second light reception area 451b in the X direction. A grating pattern is formed which is converted into incident light having coma.

In the third diffraction area 262a, the return light from the optical disc 10 is straddled across the second light reception division line L72 of the second light reception area group 452 into the third light reception area 452a and the fourth light reception area 452b. A grating pattern is formed to convert into incident light having a coma aberration opposite to that of the first diffraction area 261a. By providing the aberration of the opposite polarity, the sign of the operation for the focus error signal described later of the first light receiving area 451 a and the third light receiving area 452 a and the second light receiving area 451 b and the fourth light receiving area 452 b is reversed. It is possible to correct the displacement of the light receiving element in the y direction.

The second diffraction area 261b has a third diffraction area 262a and the fourth diffraction area 262b has a grating pattern having the same function as the first diffraction area 261a. The first spot 601a in FIG. 3 is the diffracted light from the first diffraction area 261a, the second spot 601b is the diffracted light from the second diffraction area 261b, and the third spot 602a is the third diffraction area 262a. The fourth spot 602b is the diffracted light from the fourth diffraction region 262b.

Summarizing the above, the optical disk apparatus according to the present embodiment has the following features. That is, the light receiving element 40 has at least a first light receiving area 451a, a second light receiving area 451b, a third light receiving area 452a, and a fourth light receiving area 452b. The first light receiving area 451a and the second light receiving area 451b are disposed to face each other with the first light receiving division line L71 interposed therebetween. The third light receiving area 452a and the fourth light receiving area 452b are disposed to face each other with the second light receiving division line L72 interposed therebetween. The hologram element 20 has a first diffraction area group 261 having a first diffraction area 261a and a second diffraction area 261b, and a second diffraction having a third diffraction area 262a and a fourth diffraction area 262b. And a region group 262. The first diffraction area group 261 and the second diffraction area group 262 are disposed to sandwich a first area division line L11 passing through the center of the optical axis of the focusing optical system. The first diffraction area 261a and the third diffraction area 262a include a first incident area on which the −1st order light reflected and diffracted by the tracks of the information medium is incident and a second incident area on which the + 1st order light is incident. . The second diffraction area 261 b and the third diffraction area 262 a include a third incidence area on which only light not diffracted in the tracks of the information medium is incident. In the first diffraction area 261a, the light incident on the first incident area is incident on the second light receiving area 451b, and the light incident on the second incident area is incident on the first light receiving area 451a A grating pattern for generating diffracted light having a first wavefront is formed. In the second diffraction area 261b, a grating pattern is formed which generates diffracted light having a second wavefront in which light incident on the third incident area is incident on the third light receiving area 452a. In the third diffraction area 262a, light incident on the first incident area is incident on the fourth light receiving area 452b, and light incident on the second incident area is incident on the third light receiving area 452a A grating pattern for generating diffracted light having a third wavefront is formed. The fourth diffraction area 262b is formed with a grating pattern for generating diffracted light having a fourth wavefront in which light incident on the third incident area is incident on the second light receiving area 451b.

Signals from the respective

light receiving areas

451a and 451b are detected as a focus error signal (FE signal) and a tracking error signal (TE signal) by the arithmetic circuit shown in FIG.

First, a focus error signal detection method in the optical head device of the present embodiment will be described.

5 (a) to 5 (e) are spot diagrams on the light receiving element 40, and FIG. 6 is a diagram showing the obtained focus error signal (FE signal).

5 (a) to 5 (e) are spot diagrams for the position of the optical disc 10, which correspond to the positions of FIGS. 6 (a) to 6 (e), respectively. In FIG. 6, the disk position in the in-focus state (FIGS. 5C and 6C) in which the minimum spot is formed on the information recording surface of the optical disk 10 is taken as the origin.

The FE signal is detected by the circuit shown in FIG. 4 as described above. The operation by this circuit is expressed by Equation 1. The target of the calculation in the equation is the level (intensity) of the signal (the same applies to the following equation).

FE = (451a + 452b)-(451b + 452a) (Equation 1)

First, in the in-focus state (FIGS. 5C and 6C), the signal 451b (the signal from the second light receiving area 451b), the signal 451a (the signal from the first light receiving area 451a), the signal 452a (The signal from the third light receiving area 452a) and the signal 452b (the signal from the fourth light receiving area 452b) are balanced, and the focus error signal FE represented by the equation 1 becomes zero.

When the optical disc 10 is closer to the objective lens 12 than in the in-focus state (FIGS. 5B and 6B), the first light receiving area 451a to the second light receiving area 451b is the first spot 601a. Move according to the distance. Similarly, the third spot 602a moves from the fourth light receiving area 452b to the third light receiving area 452a. As a result, the focus error signal FE represented by Equation 1 has a negative value.

Further, when the optical disk 10 and the objective lens 12 approach each other, all the first spots 601a move to the second light receiving area 451b as shown in FIG. 5C and FIG. All of the spots 602a of the light source region 545 have moved to the third light receiving region 452a. In this state, the focus error signal FE has a minimum value.

Conversely, in the case where the optical disc 10 is farther from the objective lens 12 than in the in-focus state (FIGS. 5D and 6D), the second light receiving area 451 b to the first light receiving area 451 a The spot 601a moves in accordance with the distance. Similarly, the third spot 602a moves from the third light receiving area 452a to the fourth light receiving area 452b. As a result, the focus error signal FE represented by Equation 1 has a positive value. When the optical disc 10 and the objective lens 12 further move away, all the first spots 601a move to the first light receiving area 451a as shown in the states (FIG. 5 (e) and FIG. 6 (e)). All of the spots 602a are moved to the fourth light receiving area 452b. In this state, the focus error signal FE has a maximum value.

As described above, it is possible to obtain the focus error signal FE which changes in accordance with the position of the optical disc 10. The distance between the position where the focus error signal FE takes the maximum value and the position where the focus error signal takes the minimum value, that is, the detection range of the focus error signal can be designed as desired depending on the amount of coma of the hologram element 20.

Next, a tracking error signal (TE signal) detection method in the optical head device of the present embodiment will be described. The tracking error signal generates a tracking signal TE _DPD by the DPD method and a tracking error signal TE _PP by the push-pull method by the following equation.

TE _PP = TE1-k · TE2 (Equation 2)
TE _DPD = Phase (451a + 452b, 451b + 452a) (Equation 3)

Here, Phase is a function that performs phase comparison of two signals.

Further, TE1 is a push-pull signal, TE2 is a signal for correcting a tracking offset that occurs when the objective lens 12 moves in a direction orthogonal to the information track, and is given by the following equation.

TE1 = (451a + 452a)-(451b + 452b) (equation 4)
TE2 = (451a + 451b)-(452a + 452b) (Equation 5)

Also, k is a constant and is optimized so as to minimize the variation of TE _PP due to the shift of the objective lens 12.

The detection principle of the tracking signal will be described with reference to FIGS. 7 (a) and 7 (b).

FIG. 7A is a diagram showing the hologram element 20, and for the sake of explanation, the first area division line L11, the second area division line L12, the third area division line L13, and the fourth area division line L14. Regions which can be divided by are defined as regions A1 to D2. Further, R 0 is a reflected light from the optical disc 10 incident on the hologram element 20. R1 and R2 are light diffracted by the optical disc 10, and interference with R0 generates light and dark according to the tracking position.

Three figures I, II, and III in FIG. 7A show the case where the objective lens 12 moves in the radial direction, where II is the case where the objective lens 12 is at the center of the optical axis.

FIG. 7B is a view showing spots on the light receiving element 40, and the light diffracted in each area of FIG. 7A is identified and displayed. The notation of each spot is the same as the notation of each area in FIG. 7 (a).

When the signal component detected by each spot is represented by the notation symbol,
451a = B1 + B2 (Equation 6)
451b = A1 + C2 (Equation 7)
452a = C1 + A2 (Equation 8)
452b = D1 + D2 (equation 9)
Substituting equations 6 to 9 into equations 4 and 5,
TE1 = (B1 + B2 + C1 + A2)-(A1 + C2 + D1 + D2) (Equation 10)
TE2 = (B1 + B2 + A1 + C2)-(C1 + A2 + D1 + D2) (Equation 11)

Here, since A2 and D2 and B2 and C2 are always equal even when the objective lens 12 is shifted, Equation 4 is
TE1 = (B1 + C1)-(A1 + D1) (Equation 12)
Thus, it can be confirmed that the push-pull signal is detected by the correspondence with the area of FIG.

Further, since A1 and D1 and B1 and C1 are always equal even when the objective lens 12 is shifted, Equation 5 gives
TE2 = (B2 + C2)-(A2 + D2)
Thus, it can be confirmed that the change signal can be detected by the shift of the objective lens 12 in the radial direction by the correspondence with the area of FIG. 7A.

Therefore, the _TEPP signal expressed by Equation 2 becomes a push-pull signal whose operating point does not change even if the objective lens 12 is shifted in the radial direction by appropriately selecting the value of K.

Next, detection of the DPD signal will be described. Substituting Equation 6 to Equation 9 into Equation 3,
TE _DPD = Phase (B1 + B2 + D1 + D2, A1 + A2 + C2 + C1)
Thus, conventional DPD signal detection is possible.

As described above, according to the embodiment of the present invention, it is possible to detect a push-pull signal, a phase difference signal, and a focus error signal which are not affected by the radial shift of the objective lens. The number of head amplifiers required for this detection is four as shown in FIG.

Since the signal (RF signal) recorded on the optical disk 10 is detected by the sum of the obtained signals, it is affected by the noise generated by the head amplifier. The optical head apparatus according to the present invention can perform good signal detection because the number of head amplifiers is smaller than that of the conventional head amplifiers.

Further, in the optical head device, it is general to integrate a head amplifier and further an RF signal generation circuit in the light receiving element in order to prevent extraneous noise, but according to the present embodiment, the number of head amplifiers is conventional. Since the number is smaller than the number of head amplifiers, a low cost light receiving element can be realized.

The optical head device of the present invention requires the circuit as described above for generating tracking signals, but circuits other than the head amplifier can be calculated outside the optical head device, and analog integrated circuits in the optical disk device, It is also possible to perform digital operation after analog-to-digital conversion of the head amplifier signal, and cost is not a problem if an integrated circuit having an arithmetic function shown in FIG. 4 is used.

As described above, according to the first embodiment, an optical head device capable of detecting a push-pull signal with little influence of lens movement, obtaining a good reproduction signal at low cost, and detecting a DPD signal is realized. it can.

In the present embodiment, the third area dividing line L13 and the fourth area dividing line L14 are set outside the interference area of the light ray R0, the light ray R1, and the light ray R2. It is not limited to that, and it is only necessary that the tracking error signal component of TE2 is disposed at 1 / K or less of the tracking error signal of TE1 which is disposed at a symmetrical position sandwiching the first area dividing line L11, and is realized in a system with a large interference area. It is possible.

Second Embodiment
The optical head device of the second embodiment will be described below. The configuration of the optical head device of the present embodiment is substantially the same as the configuration of the optical head device of the first embodiment, and the detailed description is omitted, and only the differences from the first embodiment will be described.

The difference from the first embodiment of the optical head device of the second embodiment is that the grating patterns of the second diffraction region 261 b and the fourth diffraction region 262 b of the hologram element 20 are different. FIG. 8 is a diagram showing a spot on the light receiving element 40 in the optical head device of the present embodiment. As shown in FIG. 8, the grating pattern of the second diffraction area 261b is formed to condense light on the third light receiving area 452a. The grating pattern of the fourth diffraction area 262b is formed to condense on the second light receiving area 451b. Since the light amounts of the second spot 601b and the fourth spot 602b are smaller than those of the first spot 601a and the fourth spot 602b, the effect on the FE signal is small, and a good FE signal can be detected.

As for the TE signal, the signal detected in each light receiving area is equivalent to the signal of the first embodiment, and thus can be similarly detected.

As described above, in the optical head device according to the present invention, the light incident on the second diffraction area 261b at the focus position of the optical disc 10 is incident on the third light receiving area 452a and the light incident on the fourth diffraction area 262b is incident on the second The light receiving area 451 b of the light receiving area 451 b of FIG.

Third Embodiment
The optical head device according to the third embodiment will be described below. The configuration of the optical head device of the present embodiment is substantially the same as the configuration of the optical head device of the first embodiment, and the detailed description is omitted, and only the differences from the first embodiment will be described.

The difference from the first embodiment of the optical head device according to the present embodiment is that the grating pattern formed in each area of the hologram element 20 is different.

The division of the area is the same as in the first embodiment and is shown in FIG. The light receiving element 40 also uses the same light receiving element as that of the first embodiment. FIG. 9 is a view showing a light receiving area of the light receiving element 40 and a spot of diffracted light in the present embodiment.

In the first diffraction area 261a, the return light from the optical disc 10 is straddled across the second light reception division line L72 of the first light reception area group 451 into the first light reception area 451a and the second light reception area 451b in the X direction and A grating pattern is formed to convert into incident light having astigmatism at an angle of 45 degrees.

In the third diffraction area 262a, the return light from the optical disc 10 is straddled across the second light reception division line L72 of the second light reception area group 452 into the third light reception area 452a and the fourth light reception area 452b. A grating pattern is formed to convert into incident light having astigmatism similar to the aberration of the first diffraction area 261a.

The second diffraction area 261b is formed with a third diffraction area 262a, and the fourth diffraction area 262b is formed with a grating pattern having the same function as the first diffraction area 261a. The first spot 601a in FIG. 9 is the diffracted light from the first diffraction area 261a, the second spot 601b is the diffracted light from the second diffraction area 261b, and the third spot 602a is from the third diffraction area 262a. The fourth spot 602b is the diffracted light from the fourth diffraction region 262b.

The signals from the

light receiving areas

451a and 451b are detected from the focus error signal (FE signal) and the tracking error signal (TE signal) by the arithmetic circuit shown in FIG.

10 (a) to 10 (e) are diagrams showing the spots on the light receiving element 40, and FIG. 11 is a diagram showing the obtained focus error signal.

10 (a) to 10 (e) are spot diagrams for the position of the optical disc 10, which correspond to the positions of FIGS. 11 (a) to 11 (e), respectively. In FIG. 11, the disc position in the in-focus state (FIGS. 10 (c) and 11 (c)) in which the minimum spot is formed on the information recording surface of the optical disc 10 is taken as the origin.

The FE signal is detected by the circuit shown in FIG. 4 as described above. The operation by this circuit is expressed by the following equation 13.

FE = (451a + 452b)-(451b + 452a) (equation 13)

First, in the in-focus state (FIGS. 10C and 11C), the signal 451b (the signal from the second light receiving area 451b), the signal 451a (the signal from the first light receiving area 451a), and the signal 452a (The signal from the third light receiving area 452a) and the signal 452b (the signal from the fourth light receiving area 452b) are well balanced, and the focus error signal FE represented by Expression 13 becomes zero.

In the case where the optical disc 10 is closer to the objective lens 12 than in the in-focus state (FIGS. 10B and 11B), the first light receiving area 451a to the second light receiving area 451b is the first spot 601a. Move according to the distance. Similarly, the third spot 602a moves from the fourth light receiving area 452b to the third light receiving area 452a. As a result, the focus error signal FE represented by Expression 13 has a negative value.

Further, when the optical disc 10 and the objective lens 12 approach each other, all of the first spots 601a move to the second light receiving area 451b as shown in FIG. 10C and FIG. All of the spots 602a of the light source region 545 have moved to the third light receiving region 452a. In this state, the focus error signal FE has a minimum value.

Conversely, in the case where the optical disc 10 is farther from the objective lens 12 than in the in-focus state (FIGS. 10 (d) and 11 (d)), the second light receiving area 451b to the first light receiving area 451a The spot 601a moves in accordance with the distance. Similarly, the third spot 602a moves from the third light receiving area 452a to the fourth light receiving area 452b. As a result, the focus error signal FE represented by Equation 13 has a positive value. When the optical disc 10 and the objective lens 12 move further away, all the first spots 601a move to the first light receiving area 451a as shown in FIG. 10 (e) and FIG. 11 (e), and the third spot All of the light source 602 a has moved to the fourth light receiving area 452 b. In this state, the focus error signal FE has a maximum value.

As described above, it is possible to obtain the focus error signal FE which changes in accordance with the position of the optical disc 10. The distance between the position where the focus error signal FE takes the maximum value and the position where the focus error signal takes the minimum value, that is, the detection range of the focus error signal can be designed as desired by the amount of astigmatism of the hologram element 20.

TE _PP = TE1-k · TE2 (Equation 14)
TE _DPD = Phase (451b + 452a, 451a + 452b) (Equation 15)
Here, Phase is a function that performs phase comparison of two signals.

TE1 = (451b + 452b)-(451a + 452a) (Equation 16)
TE2 = (451b + 451a)-(452b + 452a) (Equation 17)

The detection principle of the tracking signal will be described using FIGS. 12 (a) and 12 (b).

FIG. 12A shows the hologram element 20. FIG. Here, for the sake of explanation, the areas divided by the first area dividing line L11, the second area dividing line L12, the third area dividing line L13, and the fourth area dividing line L14 are defined as the areas A1 to D2. ing. Further, R0 is a reflected light from the optical disc 10 incident on the hologram element 20. R1 and R2 are light diffracted by the optical disk 10, and interference with R0 generates light and dark according to the tracking position.

Three figures I, II, and III in FIG. 12A show the case where the objective lens 12 moves in the radial direction, where II is the case where the objective lens 12 is at the center of the optical axis.

FIG. 12B is a view showing spots on the light receiving element 40, and the light diffracted in each area of FIG. 12A is identified and displayed. The notation of each spot is the same as the notation of each area in FIG. 12 (a).

When the signal component detected by each spot is represented by the notation symbol,
451b = B1 + B2 (equation 18)
451a = A1 + C2 (equation 19)
452b = C1 + A2 (equation 20)
452a = D1 + D2 (equation 21)
Substituting equations 18 to 21 into equations 16 and 17,
TE1 = (B1 + B2 + C1 + A2)-(A1 + C2 + D1 + D2) (Equation 22)
TE2 = (B1 + B2 + A1 + C2)-(C1 + A2 + D1 + D2) (Equation 23)

Here, since A2 and D2 and B2 and C2 are always equal even when the objective lens 12 is shifted, Equation 16 is
TE1 = (B1 + C1)-(A1 + D1) (Equation 24)
It is possible to confirm that the push-pull signal is detected by the correspondence with the area of FIG.

Further, since A1 and D1, and B1 and C1 are always equal even when the objective lens 12 is shifted, Expression 17 gives
TE2 = (B2 + C2)-(A2 + D2) (equation 25)
Thus, it can be confirmed that the change signal can be detected by the shift of the objective lens 12 in the radial direction by the correspondence with the area of FIG. 12 (a).

Therefore, by selecting the value of K appropriately, the _TEPP signal represented by Expression 14 can obtain a push-pull signal in which the operating point does not change even if the objective lens 12 is shifted in the radial direction.

Next, detection of the DPD signal will be described. Substituting Equations 18 to 21 into Equation 15,
TE _DPD = Phase (B1 + B2 + D1 + D2, A1 + A2 + C2 + C1)
Thus, conventional DPD signal detection is possible.

Also, in the optical head device, it is common to use an optoelectronic integrated circuit (OEIC) that integrates a light receiving element and a head amplifier, and further RF signal generation, on the same substrate as a light receiving element to prevent external noise. According to the present embodiment, since the number of head amplifiers is smaller than the number of conventional head amplifiers, the light receiving element can be simplified and the cost merit is great.

The optical head device of the present invention requires the circuit as described above for generating tracking signals, but circuits other than the head amplifier can be calculated outside the optical head device, and analog integrated circuits in the optical disk device, It is also possible to perform digital operation after analog-digital conversion of the head amplifier signal, and the cost is not a problem.

As described above, according to the present embodiment, it is possible to realize an optical head device capable of detecting a push-pull signal having a small influence of lens movement, obtaining a good reproduction signal at low cost, and detecting a DPD signal.

Embodiment 4
FIG. 13 is a diagram showing the configuration of the optical disc apparatus (optical information processing apparatus) of the fourth embodiment. This optical disk apparatus comprises an optical disk 10, an electric circuit 59, an optical head device 76, a drive device 79 and a rotation mechanism 78.

The rotation mechanism 78 is a mechanism that holds and rotates the optical disc 10. The optical head device 76 is any one of the optical head devices described in the first embodiment, the second embodiment, and the third embodiment, and includes the fine movement means of the objective lens 12. The optical head unit 76 is coarsely moved by the drive unit 79 to the track where the desired information of the optical disc 10 is present. Then, the optical head device 76 sends a signal to the drive device 79. The electric circuit 59 has all or part of the arithmetic functions shown in FIG. 4 and generates TE signals and FE signals, based on which the optical head device 76 and the objective lens 12 are finely moved. It sends a signal and performs focus servo and tracking servo.

The reproduction signal is generated by the sum of the signals detected by the light receiving element 40 in the optical head device 76 or in the electric circuit 59, and is output as a data raw signal after signal processing such as an equalizer.

According to the optical disk apparatus of the present embodiment, a push-pull signal with little influence of lens movement can be detected, stability can be realized by tracking servo, and good recording and reproduction can be realized. In addition, the number of head-ups is small and a good signal can be obtained.

The optical head apparatus, the light receiving element, the integrated circuit, the optical integrated element, the optical disc apparatus, and the signal detection method according to the present invention have been described based on the first to fourth embodiments. It is not limited to The embodiments obtained by applying various modifications to the embodiments without departing from the spirit of the present invention, and embodiments realized by arbitrarily combining the components in the embodiments are also included in the present invention.

An optical head device, a light receiving element, an integrated circuit, an optical integrated element, an optical disc device, and a signal detection method according to the present invention have a function of recording and reproducing information on an information recording medium. Useful as. It can also be applied to storage of computer data and programs, storage of car navigation map data, and so on.

DESCRIPTION OF SYMBOLS 10 optical disk 11 collimate lens 12 objective lens 20 hologram element 30 semiconductor laser element 40 light receiving element 59 electric circuit 76 optical head apparatus 78 rotation mechanism 79 drive apparatus

Claims

A light source for emitting a light beam, a focusing optical system for receiving the light beam and causing the light beam to converge on a minute spot on an information medium having a track, a hologram element for diffracting the light beam reflected by the information medium, An optical head device comprising: a light receiving element for receiving light diffracted by a hologram element;
The light receiving element has at least a first light receiving area, a second light receiving area, a third light receiving area, and a fourth light receiving area.
The first light receiving area and the second light receiving area are disposed to face each other with the first light receiving division line interposed therebetween,
The third light receiving area and the fourth light receiving area are disposed to face each other with the second light receiving division line interposed therebetween,
The hologram element has a first diffraction area group having a first diffraction area and a second diffraction area, and a second diffraction area group having a third diffraction area and a fourth diffraction area.
The first diffraction area group and the second diffraction area group are disposed across a first area division line passing through the center of the optical axis of the condensing optical system,
The first diffraction area and the third diffraction area are a first incident area on which −1st order light reflected and diffracted by the track of the information medium is incident and a second incident area on which + 1st order light is incident Including
The second diffraction area and the third diffraction area include a third incidence area on which only light not diffracted in the tracks of the information medium is incident,
In the first diffraction area, light incident on the first incident area is incident on the second light receiving area, and light incident on the second incident area is on the first light receiving area. A grating pattern is formed which generates diffracted light having an incident first wavefront,
The second diffraction area is formed with a grating pattern for generating diffracted light having a second wave front in which light incident on the third incident area is incident on the third light receiving area,
In the third diffraction area, light incident on the first incident area is incident on the fourth light receiving area, and light incident on the second incident area is on the third light receiving area. A grating pattern is formed which generates diffracted light having a third incident wavefront,
A grating pattern is formed in the fourth diffraction area to generate diffracted light having a fourth wavefront in which light incident on the third incident area is incident on the second light receiving area. apparatus.
further,
Using the signal A from the first light receiving area, the signal B from the second light receiving area, the signal C from the third light receiving area, and the signal D from the fourth light receiving area, When K is a constant,
TE1 = (A + C)-(B + D)
TE2 = (A + B)-(C + D)
TE = TE1-K · TE2
The optical head device according to claim 1, further comprising a circuit for detecting a tracking error signal TE obtained by
further,
Using the signal A, the signal B, the signal C and the signal D,
FE = (A + D)-(B + C)
3. The optical head device according to claim 2, further comprising a circuit for generating a focus error signal FE obtained by
further,
Using the signal A, the signal B, the signal C and the signal D,
3. The optical head device according to claim 2, further comprising a circuit for generating a phase difference tracking error signal based on the phase difference between the signals (A + D) and (B + C).
further,
3. The optical head device according to claim 2, further comprising a circuit for detecting the signal recorded on the information medium by the sum of the signal A, the signal B, the signal C and the signal D.
The ratio occupied by the first incident region or the second incident region in the first diffraction region is the ratio occupied by the first incident region or the second incident region in the second diffraction region. Greater than
The ratio occupied by the first incident region or the second incident region in the third diffraction region is the ratio occupied by the first incident region or the second incident region in the fourth diffraction region. The optical head device according to claim 1, wherein the optical head device is larger.
The optical head device according to claim 1, wherein the second diffraction region and the fourth diffraction region are point symmetric with respect to the center of the optical axis.
The optical head device according to claim 1, wherein the second diffraction area and the fourth diffraction area do not include the first incident area.
The second area is an area divided by a second area dividing line perpendicular to the first area dividing line and a third dividing line parallel to the first area dividing line. Any area that does not include the area dividing line of
The optical head device according to claim 1, wherein the fourth area is point-symmetrical with respect to the second area and the center of the optical axis.
The optical head device according to claim 1, wherein the first wavefront and the third wavefront are wavefronts having coma aberration in the direction of the first region division line.
11. The optical head device according to claim 10, wherein the third wavefront is a wavefront having a coma aberration having a polarity opposite to that of the first wavefront.
11. The optical head device according to claim 10, wherein the second wavefront and the fourth wavefront are wavefronts collected on the surface of the light receiving element.
11. The optical head device according to claim 10, wherein the grating pattern of the first region and the fourth grating pattern are equal, and the grating pattern of the second region and the third grating pattern are equal.
The optical head device according to claim 1, wherein the first wavefront and the third wavefront are wavefronts having astigmatism in a direction different from the direction of the first area dividing line by 45 degrees.
The optical head device according to claim 14, wherein the second wavefront and the fourth wavefront are wavefronts collected on the surface of the light receiving element.
The second wavefront is a wavefront having astigmatism with the opposite polarity of the first aberration,
The optical head device according to claim 14, wherein the fourth wavefront is a wavefront having astigmatism with a polarity opposite to that of the third aberration.
A light receiving element for use in the optical head device according to claim 1, wherein
The light receiving element has at least a first light receiving area, a second light receiving area, a third light receiving area, and a fourth light receiving area.
The first light receiving area and the second light receiving area are disposed opposite to each other with the first light receiving division line interposed therebetween,
The third light receiving area and the fourth light receiving area are disposed opposite to each other with a second light receiving division line interposed therebetween,
Obtained by the difference between the sum of the signal from the first light receiving area and the signal from the third light receiving area, and the sum of the signal from the second light receiving area and the signal from the fourth light receiving area A circuit for generating a first signal to be
Obtained by the difference between the sum of the signal from the first light receiving area and the signal from the second light receiving area, and the sum of the signal from the third light receiving area and the signal from the fourth light receiving area And a circuit for generating a second signal.
further,
The light receiving element according to claim 17, further comprising a circuit for multiplying the second signal by a desired constant and subtracting the result from the first signal.
further,
The light receiving element according to claim 17, further comprising a circuit that generates a sum of the signal A, the signal B, the signal C, and the signal D.
An integrated circuit for processing a signal from the optical head device according to claim 1;
Using the signal A from the first light receiving area, the signal B from the second light receiving area, the signal C from the third light receiving area, and the signal D from the fourth light receiving area, When K is a constant,
TE1 = (A + C)-(B + D)
TE2 = (A + B)-(C + D)
TE = TE1-K · TE2
An integrated circuit having a circuit for generating a tracking error signal TE obtained by
further,
Using the signal A, the signal B, the signal C and the signal D,
FE = (A + D)-(B + C)
The integrated circuit according to claim 20, further comprising a circuit that generates a focus error signal FE obtained by
further,
Using the signal A, the signal B, the signal C and the signal D,
The integrated circuit according to claim 20, further comprising a circuit that generates a phase difference tracking error signal based on a phase difference between the (A + D) and (B + C) signals.
further,
The integrated circuit according to claim 20, further comprising a circuit that generates a sum of the signal A, the signal B, the signal C, and the signal D.
A light source for emitting a light beam, a focusing optical system for receiving the light beam and causing the light beam to converge on a minute spot on an information medium having a track, a hologram element for diffracting the light beam reflected by the information medium, A method of detecting a signal with an optical head device comprising: a light receiving element for receiving light diffracted by a hologram element;
The light receiving element is
At least a first light receiving area, a second light receiving area, a third light receiving area, and a fourth light receiving area;
The first light receiving area and the second light receiving area are disposed to face each other with the first light receiving division line interposed therebetween,
The third light receiving area and the fourth light receiving area are disposed to face each other with the second light receiving division line interposed therebetween,
The hologram element has a first diffraction area group having a first diffraction area and a second diffraction area, and a second diffraction area group having a third diffraction area and a fourth diffraction area.
The first diffraction area group and the second diffraction area group are disposed across a first area division line passing through the center of the optical axis of the condensing optical system,
The first diffraction area and the third diffraction area are a first incident area on which −1st order light reflected and diffracted by the track of the information medium is incident and a second incident area on which + 1st order light is incident Including
The second diffraction area and the third diffraction area include a third incidence area on which only light not diffracted in the tracks of the information medium is incident,
In the grating pattern of the first diffraction area, light incident on the first incident area is incident on the second light receiving area, and light incident on the second incident area is the first light receiving Generating diffracted light having a first wavefront incident on the region,
The grating pattern of the second diffraction region generates diffracted light having a second wavefront in which light incident on the third incident region is incident on the third light receiving region,
In the grating pattern of the third diffraction area, light incident on the first incident area is incident on the fourth light receiving area, and light incident on the second incident area is the third light receiving Generating diffracted light having a third wavefront incident on the region,
A signal detection method for generating diffracted light having a fourth wavefront in which light incident on the third incident area is incident on the second light receiving area in a grating pattern of the fourth diffractive area.
further,
Using the signal A from the first light receiving area, the signal B from the second light receiving area, the signal C from the third light receiving area, and the signal D from the fourth light receiving area, When K is a constant,
TE1 = (A + C)-(B + D)
TE2 = (A + B)-(C + D)
TE = TE1-K · TE2
The signal detection method according to claim 24, wherein the tracking error signal TE obtained in
further,
Using the signal A, the signal B, the signal C and the signal D,
FE = (A + D)-(B + C)
The signal detection method according to claim 25, wherein the focus error signal FE obtained by
further,
Using the signal A, the signal B, the signal C and the signal D,
26. The signal detection method according to claim 25, wherein a phase difference tracking error signal is generated by the phase difference between the (A + D) and (B + C) signals.
further,
26. The signal detection method according to claim 25, wherein the signal recorded on the information medium is detected by the sum of the signal A, the signal B, the signal C, and the signal D.
The ratio occupied by the first incident region or the second incident region in the first diffraction region is the ratio occupied by the first incident region or the second incident region in the second diffraction region. Greater than
The ratio occupied by the first incident region or the second incident region in the third diffraction region is the ratio occupied by the first incident region or the second incident region in the fourth diffraction region. 25. The signal detection method according to claim 24, which is larger than the above.
25. The signal detection method according to claim 24, wherein the second diffraction area and the fourth diffraction area are point symmetric with respect to the optical axis center.
The signal detection method according to claim 24, wherein the second diffraction area and the fourth diffraction area do not include the first incident area.
The second area is an area divided by a second area dividing line perpendicular to the first area dividing line and a third dividing line parallel to the first area dividing line. Any area that does not include the area dividing line of
The signal detection method according to claim 24, wherein the fourth area is point-symmetrical with respect to the second area and the center of the optical axis.
The signal detection method according to claim 24, wherein the first wave front and the third wave front have a coma aberration in the direction of the first area division line.
The signal detection method according to claim 33, wherein the third wavefront is a wavefront having a coma aberration having an opposite polarity to the first wavefront.
The signal detection method according to claim 33, wherein the second wavefront and the fourth wavefront are wavefronts collected on the surface of the light receiving element.
The signal detection method according to claim 33, wherein the grating pattern of the first region and the fourth grating pattern are equal, and the grating pattern of the second region and the third grating pattern are equal.
The signal detection method according to claim 24, wherein the first wavefront and the third wavefront are astigmatism having a direction different from that of the direction of the first area dividing line by 45 degrees.
The signal detection method according to claim 37, wherein the second wavefront and the fourth wavefront are wavefronts collected on the surface of the light receiving element.
The second wavefront is a wavefront having astigmatism with the opposite polarity of the first aberration,
The signal detection method according to claim 37, wherein the fourth wavefront is a wavefront having astigmatism with a polarity opposite to that of the third aberration.
An optical integrated device comprising: a light source for emitting a light beam; a hologram element for diffracting the light beam reflected by the information medium; and a light receiving element for receiving the light diffracted by the hologram element,
The light receiving element has at least a first light receiving area, a second light receiving area, a third light receiving area, and a fourth light receiving area.
The first light receiving area and the second light receiving area are disposed opposite to each other with the first light receiving division line interposed therebetween,
The third light receiving area and the fourth light receiving area are disposed opposite to each other with a second light receiving division line interposed therebetween,
The hologram element has a first diffraction area group having a first diffraction area and a second diffraction area, and a second diffraction area group having a third diffraction area and a fourth diffraction area.
The first diffraction area group and the second diffraction area group are disposed across a first area division line passing through the center of the optical axis of the condensing optical system,
The first diffraction area and the third diffraction area are a first incident area on which −1st order light reflected and diffracted by the track of the information medium is incident and a second incident area on which + 1st order light is incident Including
The second diffraction area and the third diffraction area include a third incidence area on which only light not diffracted in the tracks of the information medium is incident,
In the first diffraction area, light incident on the first incident area is incident on the second light receiving area, and light incident on the second incident area is on the first light receiving area. A grating pattern is formed which generates diffracted light having an incident first wavefront,
The second diffraction area is formed with a grating pattern for generating diffracted light having a second wave front in which light incident on the third incident area is incident on the third light receiving area,
In the third diffraction area, light incident on the first incident area is incident on the fourth light receiving area, and light incident on the second incident area is on the third light receiving area. A grating pattern is formed which generates diffracted light having a third incident wavefront,
The fourth diffraction area is formed with a grating pattern for generating diffracted light having a fourth wavefront in which light incident on the third incident area is incident on the second light receiving area. element.
The ratio occupied by the first incident region or the second incident region in the first diffraction region is the ratio occupied by the first incident region or the second incident region in the second diffraction region. Greater than
The ratio occupied by the first incident region or the second incident region in the third diffraction region is the ratio occupied by the first incident region or the second incident region in the fourth diffraction region. 41. An integrated optical device according to claim 40, wherein the integrated device is larger than.
41. The optical integrated device according to claim 40, wherein the second diffraction area and the fourth diffraction area are point symmetric with respect to the optical axis center.
41. The optical integrated device according to claim 40, wherein the second diffraction region and the fourth diffraction region do not include the first incident region.
The second area is an area divided by a second area dividing line perpendicular to the first area dividing line and a third dividing line parallel to the first area dividing line. Any area that does not include the area dividing line of
41. The optical integrated device according to claim 40, wherein the fourth region is point-symmetrical with respect to the second region and the center of the optical axis.
41. The optical integrated element according to claim 40, wherein the first wavefront and the third wavefront are wavefronts having coma in the first region division line direction.
The light integrating element according to claim 45, wherein the third wavefront is a wavefront having a coma aberration having a polarity opposite to that of the first wavefront.
The light integrating element according to claim 45, wherein the second wavefront and the fourth wavefront are wavefronts collected on the surface of the light receiving element.
46. The optical integrated device according to claim 45, wherein the grating pattern of the first area and the fourth grating pattern are equal, and the grating pattern of the second area and the third grating pattern are equal.
41. The optical integrated element according to claim 40, wherein the first wavefront and the third wavefront are wavefronts having astigmatism in a direction different from the direction of the first area dividing line by 45 degrees.
50. The optical integrated element according to claim 49, wherein the second wavefront and the fourth wavefront are wavefronts collected on the surface of the light receiving element.
The second wavefront is a wavefront having astigmatism with the opposite polarity of the first aberration,
50. The optical integrated device according to claim 49, wherein the fourth wavefront is a wavefront having astigmatism with the opposite polarity of the third aberration.
An optical disk apparatus comprising the optical head apparatus according to claim 1, wherein
Using the signal A from the first light receiving area, the signal B from the second light receiving area, the signal C from the third light receiving area, and the signal D from the fourth light receiving area, When K is a constant,
TE1 = (A + C)-(B + D)
TE2 = (A + B)-(C + D)
TE = TE1-K · TE2
An optical disk apparatus having a circuit for generating a tracking error signal TE obtained in
further,
Using the signal A, the signal B, the signal C and the signal D,
FE = (A + D)-(B + C)
53. The optical disc apparatus according to claim 52, further comprising a circuit that generates a focus error signal FE obtained by
further,
Using the signal A, the signal B, the signal C and the signal D,
The optical disk apparatus according to claim 52, further comprising a circuit that generates a phase difference tracking error signal based on a phase difference between the (A + D) and (B + C) signals.
further,
The optical disc apparatus according to claim 52, further comprising a circuit that generates a sum of the signal A, the signal B, the signal C, and the signal D.