WO1993009535A1

WO1993009535A1 - Focus detecting mechanism and optical head and optical storage using the same

Info

Publication number: WO1993009535A1
Application number: PCT/JP1992/001441
Authority: WO
Inventors: Fumio Koyama; Masatoshi Yonekubo; Takashi Takeda; Toshio Arimura; Hidefumi Sakata; Osamu Yokoyama
Original assignee: Seiko Epson Corporation
Priority date: 1991-11-08
Filing date: 1992-11-06
Publication date: 1993-05-13
Also published as: KR100191884B1; KR930703669A; JP3132001B2

Abstract

A focus detecting mechanism wherein the light reflected on an object surface (25) is diffracted by a hologram element (23). The diffracted light includes two astigmatic convergent beams which form least circles of confusion on long photodetector means (29) and (30) in the same plane close to a focal plane (22f) of a lens (22), and a focus signal is obtained on the basis of a differential output from these photodetecting means. Since two diffracted beams having least circles of confusion on the same plane, the photodetecting means can be placed horizontally, and a focus detecting mechanism can be made easily with an improved dimensional accuracy. In spite of the use of a hologram element, the fluctuation of wavelength can be absorbed, and the reliability of the device is very high.

Description

Specification

Focus detection mechanism and optical head and optical storage device using the same

The present invention relates to a focus detection mechanism that detects the focus of a light beam on a target surface and is suitable for use in an optical storage device and the like, and an optical head and an optical storage device using the same. Background art

In optical storage devices that form / detect minute bits, it is essential to converge the luminous flux from the light-emitting source to an extremely small light spot on the target surface. To achieve this, focus detection using reflected light from the target surface is generally required.However, in order to reduce the size of the optical storage device, it can be efficiently mounted on an optical head and has high performance. There is a long-awaited need to achieve this, and various systems using hologram elements and the like have been proposed.

One of these, shown in Fig. 31, uses a linear diffraction grating 5 engraved at unequal intervals, enabling focus detection and the reproduction signal essential for optical storage devices. And various error signals can be obtained relatively easily, so it is regarded as an effective method.

In FIG. 31, the target surface reflected light that has been converted into a substantially parallel light beam by the objective lens 6 is split by the unequally spaced diffraction grating 5 into a first-order light and a first-order earth diffracted light. Here, the ruled line interval of the diffraction grating 5 is appropriately determined.-The primary light 7 is converged only in the grating arrangement direction (y), and the simultaneously generated + primary light 8 is diverged only in the y direction. ing. These luminous fluxes are converged by the collimating lens 9 arranged in this order. At this time, the diffracted lights 7 and 8 are located before the focal plane 9 f of the collimating lens 9 in the y direction. In the notch direction (X), which converges backward and is not affected by the diffraction grating 5, the light converges to the original focal point 9 f of the collimator lens 9, resulting in the focal point of the collimator lens 9. It becomes a non-point convergent light beam that forms a circle of least confusion before and behind the point plane 9f.

Before and after focusing, the target surface reflected light that has exited the objective lens 6 deviates from the parallel light beam at the time of focusing and converges or diverges, and the light beam focus position moves back and forth. As a result, the light is projected onto the two photoelectric conversion elements 10 and 11 that are placed in steps at the position of the circle of least confusion of ± 1st order light. The shape of the light spot changes complementarily from the vertical camellia circle to the horizontal camellia circle, and a focusing error signal is obtained as differential output by the elements 10 and 11 having a light-receiving surface with an intricate shape. ing.

In this way, the method of using the deformation of the astigmatism spot for focus detection has twice the sensitivity than the so-called spot size method that simply detects spot blur without using the astigmatism, and also uses a detector. It is superior to the so-called knife-edge method in that it must exactly match the conjugate position of the target surface during focusing, because manufacturing tolerances can be greatly reduced.Excellent focusing using astigmatic spots There is a need for a detection method.

However, in the above-mentioned unequally spaced linear diffraction grating 5, it is necessary to arrange the two detectors 10 and 11 in steps, and it is necessary to strictly control the step size. Mounting technology is required. In addition, when the wavelength of the light source fluctuates, the position of the circle of least confusion moves, which causes a problem in that the detection signal is disordered.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems, to enable a flat detector to be placed in the same plane, to enable good focus detection while being easy to manufacture, and to perform focus detection without any trouble even when the wavelength of a light source fluctuates. An object of the present invention is to provide a mechanism and an optical head and an optical storage device using the same. Disclosure of the invention

In order to achieve the above object, in a focus detection mechanism according to the present invention, a detection optical system that converges reflected light from a focus target surface;

A hologram element arranged in the detection optical system,

A pair of light detection means arranged on the same plane that is substantially conjugate with the target surface with respect to the detection optical system,

A longitudinal direction of the light detecting means is arranged substantially along a diffraction direction by the hologram element,

The hologram element has an in-phase and periodic light modulation rate pattern substantially along a hyperbolic group or a corrected hyperbolic group,

A pair of astigmatic II folded light beams whose HI-folded beam cross-sectional shape changes complementarily by the hologram element are detected by the pair of light detecting means,

—Focusing on the target surface is detected by calculating a difference between outputs of the pair of light detecting means. In another focus detection mechanism according to the present invention, a detection optical system that converges reflected light from a focus target surface;

A hologram element arranged in the detection optical system,

A pair of light detection means disposed on the same plane that is substantially conjugate with the target surface with respect to the detection optical system,

The hologram element is divided into two or more regions, and each of the divided regions has an in-phase and periodic light modulation rate pattern substantially along a hyperbolic group or a corrected hyperbolic group,

The astigmatic diffracted light beams diffracted by different regions of the hologram element are separated from each other,

A pair of astigmatic diffracted light beams, which are diffracted by different regions of the hologram element and whose beam cross-sectional shapes change complementarily, are detected by the pair of light detecting means;

—A focus on the target surface is detected by calculating a difference between outputs of the pair of light detection means.

Also, in the optical head according to the present invention, a detection optical system that converges the reflected light of the reproduction or recording light beam from the optical storage medium surface,

A hologram element arranged in the detection optical system,

A pair of light detection means groups arranged on the same plane that is substantially conjugate with the target surface with respect to the detection optical system,

Each of the pair of light detection means groups comprises two light detection means, and the longitudinal direction of the light detection means is arranged substantially along the direction of diffraction by the hologram element;

The hologram element is divided into two by a dividing line corresponding to the tangent and tangential directions of the surface of the optical recording medium, and the divided areas are substantially in-phase with each other in a hyperbolic group or a corrected hyperbolic group. And having a periodic light modulation rate pattern,

The beam cross-sectional shape changes with the same tendency, When a light beam group composed of the two astigmatism light beams is defined as an astigmatism light beam group, a pair of astigmatism light beams whose beam cross-sectional shape changes complementarily is detected by the pair of light detection means groups. And

Taking the output sum of the light detection means of each of the pair of light detection means groups, calculating the difference between the pair of output sums, and detecting the focus on the target surface;

The two astigmatic diffracted light beams diffracted from the same area of the hologram element are detected by the light detecting means to obtain a total output, and a difference between the two total outputs is calculated to detect a tracking error of the light beam. It is characterized by doing.

Further, in another optical head according to the present invention, a detection optical system for collecting reflected light of a reproduction or recording light beam from the optical storage medium surface, and

A hologram element arranged in the detection optical system,

The longitudinal direction of the light detection means is placed substantially along the direction of diffraction by the hologram element,

The hologram element is divided into two by a dividing line corresponding to the track tangential direction of the optical storage medium surface, and the in-phase and period are substantially along the hyperbolic group or the hyperbolic group captured in each of the divided areas. It has a typical light modulation rate pattern and is blazed ::

The astigmatic diffracted light beams folded by different regions of the hologram element are separated from each other,

A pair of the astigmatic diffracted light beams diffracted by different regions of the hologram element and having a beam cross-sectional shape that changes complementarily are detected by a pair of the light detection means, and the light detection means is a long light detection element. And another light detection element surrounding at least one of the light detection elements,

An output difference between the output of the long light detection element and the output of the another light detection element surrounding at least a part of the long light detection element is calculated, and a difference between the pair of the output differences is calculated. To detect the focus on the target surface,

A light head characterized in that a tracking error is detected by calculating a difference between outputs of the pair of long light detecting means. Further, in the optical storage device according to the present invention, the light for irradiating the reproduction or recording beam onto the optical storage medium is focused based on a source and a focus detection result of the light head. Focusing means for performing tracking adjustment, and tracking means for performing tracking adjustment based on the detection result of the tracking error of the optical head. BRIEF DESCRIPTION OF THE FIGURES

1 to 30 show an embodiment of a focus detection mechanism and an optical head and an optical storage device according to the present invention. FIG. 1 is a schematic diagram of a hologram pattern suitable for use in the present invention. FIG. 2 is an explanatory diagram showing a state of diffraction by a hologram, and FIG. 3 is another explanatory diagram showing details of diffraction by a hologram. FIG. 4 is a main cross-sectional view of the focus detection mechanism according to the first embodiment of the present invention. FIG. 5 is an explanatory diagram of a photoelectric conversion element in the focus detection mechanism of the first embodiment. FIG. 6 is an explanatory diagram of the operation of the focus detection mechanism of the first embodiment. FIG. 7 is a graph of a forcing single error signal by the focus detection mechanism of the first embodiment. FIG. 8 is a front view of a photoelectric conversion element having another configuration in the focus detection mechanism of the first embodiment. FIG. 9 is an explanatory diagram of a hologram element of an optical head according to a second embodiment of the present invention. FIG. 10 is a cross-sectional view of the optical head of the second embodiment. 1 is a front view of the photoelectric conversion element of the optical head of the second embodiment, FIG. 12 is a perspective view of a main part of the optical head of the second embodiment, and FIG. FIG. 14 is a perspective view of a main part showing another configuration example of the optical head of the second embodiment. FIG. 14 is a perspective view of a main part showing still another configuration example of the optical head of the second embodiment. is there. FIG. 15 is a front view of the photoelectric conversion element of the optical head according to the second embodiment of the present invention. FIG. 16 is an explanatory diagram of the hologram element of the optical head according to the fourth embodiment of the present invention. FIG. 17 is a front view of the photoelectric conversion element in the optical head of the fourth embodiment. It is a figure. FIG. 18 is a main cross-sectional view of a focus detection mechanism showing a fifth embodiment of the present invention. FIG. 19 is an essential sectional view of an optical head showing a sixth embodiment of the present invention. FIG. 20 is a schematic sectional view of a hologram element used for the optical head of the sixth embodiment. FIG. 21 is a front view of the photoelectric conversion element in the optical head of the sixth embodiment. FIG. 22 is a main cross-sectional view of a focus detection mechanism according to a seventh embodiment of the present invention. FIG. 23 is a cross-sectional view of a focus detection mechanism according to another configuration of the seventh embodiment. FIG. Figure 24 shows the book FIG. 25 is a main cross-sectional view of an optical head according to an eighth embodiment of the present invention. FIG. 25 is a front view of a photoelectric conversion element in the optical head according to the eighth embodiment, and FIG. It is a principal sectional view of the optical head which shows the other structure of an Example. FIG. 27 is a main cross-sectional view of the optical head according to the ninth embodiment of the present invention. FIG. 28 is a main cross-sectional view of a focus detection mechanism according to a tenth embodiment of the present invention, and FIG. 29 is a main cross-sectional view of a focus detection mechanism showing another configuration of the tenth embodiment. is there. FIG. 30 is a front view of an optical head photoelectric conversion element according to an i-th embodiment of the present invention.

FIG. 31 is a main cross-sectional view of a conventional focus detection mechanism using a diffraction grating, and FIG. 32 is a perspective view of a main part of a conventional optical head using a diffraction grating. BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in detail based on the embodiment shown in FIGS. The same reference numerals denote the same functional members.

(Example 1)

FIGS. 1 to 8 show a first embodiment according to the present invention. FIG. 1 is an explanatory view of a hologram 15 suitable for use in the focus detection mechanism of the present invention. The pattern 15 p formed on the glass substrate 15 b is represented by an equation expressed by rectangular coordinates (X, y) on the substrate plane, where c is a constant.

X ² — y = earth c ²

Are formed so as to have the same amplitude and phase light modulation rate, that is, the same transmittance and thickness or refractive index, along a group of hyperbolas represented by. Furthermore, these hyperbolic patterns 15 p are calculated using the constants f and L

c ² = (f + η · λ) ² -f ²

Has a periodic structure that repeats the same light modulation rate pattern every time the value of n represented by For example, hyperbolic

Sat (X ² — y ² ) = (f + λ) ² -f ²

And the part on the hologram surface according to the hyperbola

± Cx ² -y ² ) = (± + 2 λ) ² -f ²

Are portions having the same amplitude and phase light modulation rate, and have the same phase in the periodic structure. In order to form such a pattern 15P, for example, a general synthetic hologram is used in which a photosensitive agent applied on a glass substrate 15b is exposed through a mask having a desired pattern, and the glass substrate 15b is etched after development. Can be applied in the same way.

2 (a) and 2 (b) are explanatory views showing the state of diffraction by the hologram 15. FIG. As shown in FIG. 2 (a), when the parallel light 16 is vertically incident on the hologram 15 described above, the light beam incident on the point (x, y) becomes the pattern 15p of this part. It will be diffracted in the arrangement direction. In Fig. 2 (b), the slope of the tangent of the hyperbola at (X, y) is

dy / dx = x / y

And the arrangement direction of the pattern 15 p is perpendicular to this. Therefore, when the diffracted ray is projected on the X-y plane,

dy dx = -y x

A straight line L with a cover of As can be seen from Fig. 2 (b), the distance from the point (x, y) to both the x and y axes measured along this straight line L is equal to each other, and the distance r to the coordinate origin (0, 0) is also equal. Matches. On the other hand, when the interval D of one cycle of the pattern at (x, y) is calculated,

D = λ · (f + η · λ) / r

It is. Therefore, when the parallel light 16 of the same wavelength is irradiated, the diffraction angle ± 0 of the soil first-order light with respect to the light entering the point (x, y) is

sine = r / (f + nλ)

And f is sufficiently large compared to η · λ, so that on the surface that is separated from the hologram surface by the distance f in the ζ direction, the diffracted light 17, 18 will be (2, 0) on the axis and on the y axis (0, 2y). The above applies to all points (x, y) on the hologram surface, and the diffracted light generated here converges at the focus distance: e in the y direction and converges in the X direction, as shown in Fig. 2 (a). Is the primary light 17 diverging at f and the primary light 17 diverging at f, and converging at the focus distance f in the X direction, while diverging at the focal distance 1 f in the y direction + primary light 1 8 2 light fluxes. That is, on the focal plane 15 f of the distance: f, linear diffraction patterns 19, 20 overlapping both the X and y axes are obtained. It should be noted that such a hologram 15 has a wavelength variation of the light source. It has the characteristic that the focus distance ± f expands and contracts by the same amount before and after movement.

When the pattern 15 P completely complies with the hyperbolic equation, it is inevitable that aberrations due to deviation from paraxial appear. This aberration is not a problem for practical use, but in order to correct it, a correction term that is close to the equation may be added, the amplitude and phase modulation rate may be adjusted, or the substrate 15b may be curved. Also in this case, the necessary correction is slight, and the pattern for realizing the above does not substantially change from the hyperbola. By the way, if the parallel light 16 incident on the hologram surface has a finite diameter, the range of the emitted light can be limited. For example, as shown in Fig. 3), assuming that the incident light is a finite light beam 16 A having a diameter of 2 a and centered on the hyperbolic origin (0, 0), a diffraction pattern of ± 1 order light 19 A, 20 A Is as shown in Fig. 3): A crosshair consisting of two line segments, one 2a≤x2a on the? Axis and one 2a≤y≤2a on the y-axis. Further, as shown in FIG. 3 (c), in the light beam 16B having a diameter 2a incident on the center (0, b) off the central axis of the hyperbola, the ± 1st-order diffraction pattern 19B, As shown in Fig. 3 U), 2 0 B is two line segments of 2 a ≤ X ≤ 2 a on the X axis and 2 b-2 a ≤ y ≤ 2 b + 2 a on the y axis, | b |> If b is selected for a, the two are separated. Further, as shown in FIG. 3 (e), when a light beam 16 C centered on (b, b) is incident, as shown in FIG. 3 (f): the pattern 19 C on the κ axis is also 2 b Will only move. Therefore, the hologram element does not necessarily need to include the origin (0, 0) of the hyperbola within the substrate area, and uses only a part of the extraneous pattern corresponding to the incident range of the finite phantom beam to separate the beam. .

As is well known in ordinary synthetic holograms, the amplitude and the phase light modulation rate during one period are appropriately determined to increase or decrease the amount of diffracted light of a specific order, It is also possible to obtain an appropriate hologram element according to the application, for example, by changing the light distribution.

For example, as is well known, if a blazing method is used in which the light modulation rate of one cycle of the hologram element is made to have a sawtooth function, for example, only the light intensity of the primary light is increased. A hologram element with almost no light intensity can be obtained. If the blaze angle is selected, for example, the relative intensity of the + 1st-order light and the 0th-order light can be appropriately determined.

Furthermore, the slope of the asymptote common to the group of hyperbolas is dy / dx = ± 1

The absolute value of the focus distance that appears before and after in the x and y directions can also be changed. For example

d y / d x = ± 2

For a group of hyperbolas with an asymptote of a slope of, a luminous flux with a focus distance of + f ′ and 14 f ′ in the X and y directions and a luminous flux with a focus distance of 1 f ′ and + 4 f ′ Of, two things can happen.

In the following description, as described above, the diffracted light that converges in the main diffraction direction and diverges in a direction perpendicular to the main diffraction direction is referred to as primary first-order light, and conversely, diverges in the generated diffraction direction. Then, the diffracted light converging in the direction perpendicular to this is called + 1st-order light, and the two are distinguished.

FIG. 4 is a layout diagram showing a configuration example of a focus detection mechanism using a hologram element as described above. The divergent light from the semiconductor laser 21 is converted into a parallel light by the collimator lens 22 and reaches the hologram element 23 disposed immediately thereafter. Here, the hologram element 23 has a hyperbolic pattern having the asymptote of the above-mentioned inclination ± 1, and the position where the incident optical axis is displaced in the y direction from the origin of the group of hyperbolas as shown in FIG. Off-axis pattern that passes through. Therefore, both the first-order diffracted light and the first-order diffracted light are dispersed from the optical axis, and only the straight-order 0th-order light passes through the objective lens 24 arranged at an appropriate distance and passes through the recording Z reproduction beam converging on the optical recording medium surface 25. Has formed. The reflected light from the medium surface 25 of the incident beam is diverged, travels backward, is converted into a substantially parallel light beam by the objective lens 24, and is diffracted again to the hologram element 23. On the return path, the collimating lens 22 is disposed immediately after the hologram element 23, and in this case, the soil first-order diffracted lights 26 and 27 are also converged by the collimating lens 22. In order to receive these ± 1st-order diffracted lights 26 and 27, the long side extends along the radiation direction from the optical axis 28 as shown in Fig. 5 on the focal plane 22f of the collimator lens 22. Thus, rectangular photoelectric conversion elements 29 and 30 are provided.

Here, if the distance between the collimator lens 22 and the hologram element 23 is sufficiently small, the luminous flux of the focal length soil f incident on the collimator lens 22 will be the focal length of the collimator lens 22 Than F Therefore, the first-order diffracted light 26 incident on the collimate lens while diverging in the e direction and converging at + f in the y direction while diverging in the e direction is: A focal line is connected behind by α, and a focal line is connected just before or in the y direction. On the other hand, the + 1st-order diffracted light 27, on the other hand, forms a focal line slightly forward in the X direction and a focal line slightly backward in the y direction, and the diffracted lights 26, 27 Both are astigmatic convergence beams that connect the circle of least confusion on the same plane near the focal plane 22 f of the collimator lens 22. As described above, when the wavelength of the light source fluctuates, the focus distance before and after the diffracted light 26, 27 incident on the collimator lens 22 expands and contracts by the same amount, so that the position of the circle of least confusion hardly moves. . In addition, the diffraction angle of the ± first-order zero-fold light 26, 27 changes with the wavelength fluctuation, and the incident position on the photoelectric conversion elements 29, 30 moves in the radiation direction accordingly. Since the transducers 29 and 30 are long in the radial direction, this movement does not affect the output.

Before and after focusing, the reflected light passing through the objective lens 24 deviates from the parallel light beam at the time of focusing and converges or diverges. That is, when the medium surface 25 is closer to the focal point of the objective lens 24, the light beam diverges, and when it is farther away, the light beam converges conversely. Therefore, when the medium 25 is near, the light beam is collected rearward when the collimator lens 22 is in the image plane, and moves toward the near side when the medium 25 is far. As a result, as shown in FIG. 6, the shapes of the light spots 31 and 32 projected on the rectangular photoelectric conversion elements 29 and 30 are as shown in FIG. 6A when the medium 25 is close. The primary spot 31 is a vertical ellipse and the primary spot 32 is a horizontal ellipse. When focused, the circle of least confusion as shown in (b). When the medium 25 is far away, as in (C). — Primary boss 3 1 is a horizontally long ellipse and + primary boss 32 is a vertically long ellipse. The long-elliptical slot whose major axis coincides with the long side of the photoelectric conversion elements 29 and 30 has a larger photoelectric conversion output, so the photoelectric conversion element 29 on the-primary side and the photoelectric conversion of the + 1st order If the output of the element 30 is differentiated, a focusing error signal S as shown in FIG. 7 is obtained. By driving the actuator for adjusting the position of the objective lens 24 back and forth so that this signal has a constant value, the recording / reproducing beam can always be collected on the medium surface 25.

To achieve this, a difference signal between the obtained error signal and the control target value is obtained, and if necessary, an appropriate order of complementarity is added to the difference signal to obtain a drive signal for the actuator. Are known. As described above, according to the configuration of the present embodiment, the two photoelectric conversion elements 29 and 30 for obtaining the differential output can be placed in the same plane, and the step size is strictly controlled. There is no need for this, and the manufacture of devices is greatly facilitated, especially for composite devices incorporated in the same package as the semiconductor laser. In addition, the change in the diffraction angle is compensated for by the long photoelectric conversion elements 29 and 30 with respect to the wavelength fluctuation, and the focal line positions are moved back and forth by the same amount, so that the center of the differential is not shifted. Even when a light source such as a semiconductor laser whose emission wavelength is liable to change is used, the advantages of the hologram can be fully utilized.

In this embodiment, by changing the width of the short sides of the rectangular photoelectric conversion elements 29 and 30, the output difference between the case where the medium is near and the case where the medium is far can be increased and decreased, and the width of the short side is small. The output becomes smaller when the light spots 31 and 32 become horizontally elliptical. However, since the amount of received light during focusing also decreases at the same time, which causes problems such as weakness to noise, it is desirable to select an appropriate value according to the actual application. The shape of the photoelectric conversion elements 29 and 30 is not limited to a rectangle, but may be an ellipse as long as it is long. Further, the shape of the photoelectric conversion elements 29 and 30 may be rectangular or the like, or, for example, a mask may be provided on the front surface of the photoelectric conversion element to limit the light receiving region to an appropriate shape. Further, as shown in FIG. 8, a splitting element 33 having peripheral regions 33 s on both sides of a long central region 33 c along the diffraction direction is used, and the central region 33 c and the peripheral region 33 are used. The output difference from s may be used instead of one of the photoelectric conversion elements 29 and 30. In this way, even when the light spots 31 and 32 become horizontally elliptical, the surrounding light amount can be effectively used for detection, which is preferable. The peripheral region 33s may be provided separately on both sides of the central region 33c as shown in the figure to add the output, or may be provided so as to surround the central region 33c. .

In addition, the focus detection mechanism of the present invention is not only suitably applied to the optical storage device described above, but also an optical probe type shape measuring device or the like which requires a similar high-performance focusing sensor. It can also be applied to devices such as an atomic force microscope that optically captures the movement of the cantilever, and can provide compact and highly reliable focus detection.

(Example 2)

9 to 14 show a second embodiment of the present invention. The child 35 is composed of two symmetrical regions 35 A and 35 B corresponding to each other via a dividing line 35 p as shown in FIG. 9A. In these regions 35 A and 35 B, the above-described hyperbolic patterns, particularly off-axis patterns deviated in the y-direction from the hyperbolic origin as shown in FIG. 3 (c), are formed. In the half area 35A, the left half of the off-axis pattern rotated clockwise by 80 degrees is drawn, and in the right half area 35B, the same off-axis pattern is counter-inverted. The right half of a clockwise rotation of 80 degrees is shown. Therefore, when a parallel luminous flux straddling the left and right areas 35A and 35B is incident, a total of 4 points on a straight line inclined ± 80 degrees with respect to the dividing line 35p as shown in Fig. 9 (b). Light beams 36 A, 36 B, 37 A, and 37 B are generated.

FIG. 10 is an explanatory view of the optical head of the magneto-optical recording / reproducing apparatus configured using the above-mentioned hologram element 35. The divergent light from the semiconductor laser 38 is collimated by the collimator lens 39. The light is converted into parallel light, reaches the hologram element 35 disposed immediately thereafter, and travels straight. The 0th-order light passes through the objective lens 40 disposed at an appropriate distance and is collected on the recording medium surface 41. A recording Z reproduction beam is formed. The reflected light of the incident beam from the medium surface 41 becomes divergent light, travels backward, is converted into a substantially parallel light beam by the objective lens 40, and reaches the hologram element 35 again. The two areas 35 A of the hologram element 35 , 35B form first-order diffracted lights 36A and 36B and + first-order diffracted lights 37A and 37B, respectively. Here, the hologram element 35 is arranged such that the division line 35 p is parallel to the track groove direction of the optical storage medium 41. The diffracted lights 36 A, 36 B, 37 A, and 37 B are converged by the collimator lens 39, and as shown in FIG. 11, are shifted to the left and right along the dividing line 35 p of the hologram element 35. A non-point-collected luminous flux reaching a straight line inclined at 80 degrees. In order to detect the optical robots 42 A, 42 B, 43 A, 43 B connected by these light beams, a rectangular photoelectric conversion element 44 A, 44 B, which is long along the radiation direction. 45 A and 45 B are provided, all of which are placed on the same plane. In front of the left and right photoelectric conversion elements 44A and 45B and the right and left photoelectric conversion elements 44B and 45A, two polarizing plate analyzers 46 and 47 are provided, respectively. The transmission axes 46a and 47a are disposed so that they are turned to the right and left from the polarization axis of the semiconductor laser by an appropriate angle.

Here, the diffracted light incident on the photoelectric conversion elements 44 A, 44 B, 45 A, and 45 B is minimum on the focal plane 39 f of the collimating lens 39 as in the case described above. The circle of confusion It is a non-point convergent light flux. Before and after focusing, the primary spots 42A, 42B projected on the photoelectric conversion elements 44A, 44B, and +1 projected on the photoelectric conversion elements 45A, 45B At the next spots 43A and 43B, the shape changes complementarily between the vertical ellipse and the horizontal ellipse. Therefore, using the outputs VIA, V1B, V2A, and V.2B of the photoelectric conversion elements 44A, 44B, 45A, and 45B,

(V 1 A + V 1 B)-(V 2 A + V 2 B)

By controlling the focusing error of the objective lens 40 so that the error signal can be obtained as a constant value, the recording / reproducing beam is always output on the medium surface. Can converge.

For this purpose, as described above, a difference signal between the error signal and the control target value is obtained, and if necessary, an appropriate position complement 僙 is added thereto to obtain a drive signal for the actuator. Etc. are known.

Also, when the light beam formed on the recording medium 41 by the objective lens 40 deviates from the track groove of the recording medium 41, the left and right areas 35A of the dividing line 35p parallel to the track groove are formed. , 35 B, there is a difference in the amount of reflected light. As a result, the sum of the outputs of the photoelectric conversion elements 44 A and 45 A that receive the diffracted lights 36 A and 37 A in the left area 35 A and the diffracted light 36 B in the right area 35 B , 37 B, the sum of the outputs of the photoelectric conversion elements 44 B, 45 B is unbalanced. Therefore

(V 1 A + V 2 A)-(V 1 B + V 2 B)

By the calculation, a tracking error signal can be obtained. That is, if the value of the above equation is 0, the tracking is normal, and if the value is positive or negative, the tracking is off. Therefore, if tracking control of the objective lens is performed so that this signal has a constant value, the recording / reproducing beam can always be converged on the track.

For this purpose, a difference signal between the error signal and the control target value is obtained in the same manner as in the case of the focusing described above, and if necessary, an appropriate complementary value 僙 is added thereto. And the like are known.

The analyzers 46 and 47 are provided for detecting the magneto-optical signal. In other words, the medium reflected light of the reproduction beam incident on the semiconductor laser 38 with a unique polarization plane is transmitted between the eraser and the recording bit: the rotation directions of the polarization planes due to the force effect are mutually different. The opposite is true. Therefore, if, for example, one rotation occurs in the transmission direction 46a of the analyzer 46 arranged in the left photoelectric conversion elements 44A and 45B in the erasing section, the left photoelectric conversion element 44 The amount of light reaching A, 45B increases, and the amount of light from the right-handed photoelectric conversion elements 44B, 45A decreases. Conversely, in the recording bit portion, since the Kerr rotation occurs in the transmission direction 47a of the analyzer 47 arranged in the right photoelectric conversion elements 44B and 45A, the left photoelectric conversion elements 44A, The amount of light that reaches 45 B decreases, and the amount of light from the right photoelectric conversion elements 44 B and 45 A increases. Therefore,

(V 1 A + V 2 B) one (V 1 B + V 2 A)

By the calculation, the magneto-optical recording signal can be reproduced. In particular, if this calculation is followed, the differential output between the primary light and the primary light is obtained, so that the diffraction efficiency between the primary light and the primary light is higher. Even at different times or when defocusing occurs, it is possible to efficiently remove the in-phase light amount fluctuation noise and the like by taking advantage of the differential detection, and obtain a high-quality reproduced signal.

On the other hand, in the so-called pre-bit section, the light amount itself of the medium reflected light is modulated, so that the light amounts incident on the photoelectric conversion elements 44 A, 44 B, 45 A, 45 B all increase or decrease in the same manner. Therefore, in order to reproduce the pre-bit signal,

V 1 A + V 1 B + V 2 A + V 2 B

It is sufficient to perform the calculation of

As described above, the optical head according to the present embodiment has a configuration with an extremely small number of components, and can obtain all the signals necessary for the magneto-optical recording device while being small in size and low in cost. In addition, all the outputs of the four photoelectric conversion elements can be used for calculation of any signal, and can be generated by a calculation different from any of the signals, so that there is no waste of light quantity and crosstalk between signals. It is possible to obtain high quality magneto-optical signals, pre-pit signals and various error signals. Furthermore, since the photoelectric conversion element is long along the diffraction direction even with respect to the wavelength fluctuation of the light source, there is no effect due to the movement of the diffraction bot, and the astigmatic luminous flux of each astigmatic light flux is not affected. Since the two focal line positions move back and forth by approximately the same amount, the center of the differential does not shift, and even when a light source such as a semiconductor laser whose emission wavelength is liable to change is used, the hologram element can be used. The advantages can be fully utilized. Therefore, an optical storage device equipped with the optical head of the present embodiment and controlling the focusing and tracking as described above has a high quality. It is supported by output signals, has high reliability and high performance, and has a small head, which makes the entire device smaller.

Since the photoelectric conversion elements 44 A, 44 B, 45 A, and 45 B for obtaining the output can all be placed in the same plane as in the first embodiment, the step size is strict. There is no need to manage the device, and the manufacture of devices is greatly facilitated, especially for composite devices that incorporate a photoelectric conversion device in the same package as the semiconductor laser.

In other words, if a similar light head is to be constructed using a conventional linear grating hologram element, as shown in Fig. 32, four photoelectric conversion elements are replaced by at least two base substrates 48a, 4b. It was necessary to make two pieces each on 8b and arrange them separately on both sides of the semiconductor laser.

On the other hand, in this embodiment, as shown in FIG. 12, four photoelectric conversion elements 44 A, 44 B, 45 A, and 45 B are manufactured on one base substrate 49. And dimensional control during assembly is greatly simplified. The semiconductor laser 38 may be provided with a heat sink 50 provided on the base substrate 74 as shown in FIG. 12 or cut out at the center of the base substrate 51 as shown in FIG. The structure may be such that the portion 5 la is provided and the heat sink 52 is disposed at the center of the cutout portion 51 a. Further, as shown in FIG. 14, the heat sink 53 may be a cantilever structure, and the base substrate 49 may be inserted and arranged below the beam. In this way, since all the photoelectric conversion elements used for detection can be formed on the same base substrate, not only the dimensional control during assembly is easy, but also the head, pump, signal processing, and signal processing are performed on the same base substrate. It is easy to mount arithmetic circuits etc. in a monolithic manner, and it is also easy to achieve further downsizing and higher performance. In the above embodiment, the azimuth angles of the transmission axes 46 a and 47 a of the analyzers 46 and 47 were set to be appropriate. By changing this angle, the angle of the magneto-optical recording signal with respect to the amount of incident light was changed. The degree of modulation can be changed. Therefore, for example, it is desirable to adjust the angle so that the degree of modulation can be increased while suppressing noise proportional to the amount of incident light. Instead of using the polarizing plates as the analyzers 46 and 47, another element having an analyzing function, for example, a polarizing beam splitter using a multilayer film may be used.

The rotation angles of the hyperbolic pattern in the regions 35A and 35B of the hologram element, and the directions of generation of the primary light and the primary light of the regions 35A and 35B are as described above. There is no need to limit. Furthermore, the combinations for obtaining various signals Other than this, any signal can be used as long as a similar signal can be obtained.

In the above description, the description has been given along the magneto-optical recording device and the optical head for magneto-optical recording. However, the focus detection and tracking are performed in the same manner for other types of optical recording devices and optical heads. Detection and pre-bit detection are possible, and an optical storage device that performs focusing control, tracking control, and signal reproduction can be configured based on the detection and pre-bit detection. For example, the same applies to read-only optical disk devices such as so-called compact disks and video disks, write-once disk devices such as dye recording type and hole-burning type, and rewritable disk devices of phase change recording type. Can be used for These discs do not have magneto-optical bits, and the bits are all reflectance-modulated bits. Therefore, the analyzer having the above-described configuration is unnecessary. It is desirable to increase efficiency.

(Example 3)

FIG. 15 shows a third embodiment in which the second embodiment is modified, and the same reference numerals as those described above denote the same functional members. In Example 2, the four-valued photoelectric conversion elements are elongated along the direction of diffraction separation as shown in FIG. 11 and are arranged radially, whereas in this example, two photoelectric conversion elements are provided as shown in FIG. each of the photoelectric conversion element 4 4 a ', 4 4 B 5, 4 5 a', 4 5 B ' is a elongated in a direction parallel to each other. In the case of a radial arrangement, when the element arrangement center and the light source position deviate, the spot position deviation is not compensated for by the element shape. The placement error can be improved. As described above, if the diffracted lights 42A, 42B, 43A, and 43B are arranged at close angles such as ± 80 ° with respect to the dividing line, the photoelectric conversion element 44A ', Since the longitudinal directions of 44B ', 45A', and 45B are roughly along the diffraction direction, the effect of complementing the movement of the robot when the wavelength varies is not impaired on a practical level. This is effective because a manufacturing error in the scale direction can be compensated. Also, when the photoelectric conversion elements 44 A ′ and 45 B ′ arranged on the left side and the photoelectric conversion elements 44 B ′ and 45 Α ′ arranged on the right side are manufactured separately, In a parallel arrangement, mutual alignment is difficult, while in a parallel arrangement, mutual deviation can be compensated for by rotating the hologram 35 and moving the spots, and the manufacturing magazine can be widened.

(Example 4)

FIGS. 16 to 17 show a fourth embodiment in which the second embodiment described above is modified, The same reference numerals as those described above represent similar functional members. In the second embodiment, the hologram patterns in the left and right regions of the dividing line are the same off-axis pattern, and the spots can be separated by changing the pattern rotation angles in the left and right regions 35A and 35B. On the other hand, in the hologram element 55 of the present embodiment, the hologram pitches of the areas 55A and 55B are changed. In other words, the left and right patterns are basically different in the degree of off-axis from the origin of the force hyperbola generating the luminous flux with the same focus distance ± f, so that the diffraction separation angles are different. In this case, the diffracted light beams 56 A, 56 B, 57 A and 57 B by the respective regions 55 A and 55 B can be arranged on a straight line.

For example, in the area 55A, a pattern with a large pitch, that is, a pattern with a small degree of off-axis is drawn by rotating by 90 degrees, and in the area 55B, a part with a small pitch, that is, a degree of off-axis is large. If the pattern is drawn by rotating the pattern by −90 degrees, the ± 1st-order diffraction robots 58 B and 59 B in the area 55 B will be two spots 58 A and 59 A in the area 55 A Appears in a straight line outside of.

When the diffraction spots are arranged in this manner, the corresponding four photoelectric conversion elements 60 A, 60 B, 61 A, and 61 B are also arranged linearly, and the spot movement at the time of wavelength fluctuation is reduced. This is effective because it can completely compensate and, as in the previous embodiment, can reduce the manufacturing tolerance in the diffraction separation direction.

(Example 5)

FIG. 18 shows a fifth embodiment of the present invention, and the same reference numerals as those described above denote the same functional members. The divergent light from the semiconductor laser 21 is collimated by the collimating lens 22, then passes through the beam splitter 62, passes through the objective lens 24, and passes on the optical storage medium surface 25. To form a recording / reproducing beam that converges. The reflected light of the incident beam from the medium surface 25 becomes divergent light, travels backward, is converted into a substantially parallel light beam by the objective lens 24, and is transmitted to the hologram element 63 arranged on the optical path bent by the beam splitter 62. Reach. Here, the hologram element 63 has a hyperbolic pattern similar to that of the above-described first embodiment. As is well known in the case of ordinary synthetic holograms, It is desirable to reduce the intensity of the secondary transmitted light as much as possible and to increase the diffraction efficiency of the ± 1st order light. The ± 1st-order diffracted light emitted in this manner is refracted by the condenser lens 64 disposed immediately thereafter. On the focal plane 64 f of the focusing lens 64, two photoelectric conversion elements 29, 30 is provided.

With the above configuration, it is possible to perform focus detection in the same manner as in the above-described second embodiment. Further, the hologram element 63 can be of a split type as in the second embodiment, and four photoelectric conversion elements can be provided to form the same optical head and optical storage device. By splitting the optical path in this way, the efficiency of the zero-order light can be reduced as described above, and the efficiency of the ± first-order light can be increased instead. Thus, the amount of light reaching the photoelectric conversion elements 29, 30 can be reduced. Many are preferred.

Further, if the focal length of the condenser lens 64 is made longer than the focal length of the collimator lens 22, the longitudinal magnification of the optical system for detection with respect to the medium side can be independently adjusted to be higher. Therefore, it is possible to widen the astigmatic difference of the detection light beam while securing the light use efficiency of the semiconductor laser, and it is possible to increase the focus error detection sensitivity.

(Example 6)

FIGS. 19 to 21 show a sixth embodiment of the present invention, and the same reference numerals as those described above denote the same functional members. The hologram element 65 placed in the parallel optical path is a divided hologram element 65 having a pattern similar to that of the second embodiment described above, and the respective areas 65 A and 65 A are formed by the blazing method described above. One of the ± 1st-order lights of 5B, for example, is configured so that only the intensity of the light beam diffracted to the right of the dividing line 65P is increased. It is known that such blazing can be realized, for example, in a transmission type hologram element 65 by forming a sawtooth cross section 65c that rises to the left as shown in FIG. If the blazing angle is set appropriately, the light intensity can be reduced to almost zero for light diffracted to the left.

In this case, the diffracted light on the return path involved in detection is the primary light 66 B of the region 65 B diffracting rightward of the dividing line 65 p and the + primary light 67 of the region 65 A A only. As shown in FIG. 21, only the photoelectric conversion elements 68 B and 69 A corresponding to the two light beams 66 B and 67 A are provided on the detection surface in the same plane. As described above, the two photoelectric conversion elements 68 B and 69 A are provided with two peripheral areas 68 Bs and 69 As on both sides of the central area 68 Bc and 69 Ac, respectively. It is a dividing element, and the dividing lines are provided along the respective diffraction directions. Assuming that the photoelectric conversion output of each area 6 8 B c, 6 8 B s, 6 9 A c, 6 9 A s is V 1 c, V is, V 2 c, V 2 s, focusing • The error signal is

(Vic-Vis)-(V2c-V2s)

= (V 1 c + V 2 s)-(V 2 c + V 1 s)

Also, the tracking error signal

(V 1 c + V 1 s) one (V 2 c + V 2 s)

Or

V 1 c-V 2 c

Can be obtained at Further, if analyzers having different azimuths of transmission axes are provided on the front surfaces of the photoelectric conversion elements 68B and 69A, the magneto-optical reproduction signal can be obtained.

(V 1 c + V 1 s)-(V 2 c + V 2 s)

Is obtained. This calculation is the same as the above-mentioned tracking error signal, but since the band of the magneto-optical signal is high, if the band of the signal is electrically separated, both can be obtained independently.

As described above, the optical head according to the present embodiment also has a configuration with an extremely small number of components and requires only one side of the light source to be provided with the light detecting means. All the signals required for a magneto-optical recording device can be obtained at low cost. In addition, since all the outputs of the photoelectric conversion means can be used for calculating any of the signals, it is possible to obtain high-quality magneto-optical signals, pre-bit signals, and various error signals without wasting light. is there. Furthermore, since the photoelectric conversion element is long along the diffraction direction even with respect to the wavelength variation of the light source, there is no effect due to the movement of the diffraction spot, and the two non-point convergent light beams Since the focal line position moves back and forth by approximately the same amount, the center of the differential does not deviate, and even when using a light source such as a semiconductor laser whose emission wavelength is liable to fluctuate, the advantages of the hologram element can be fully utilized. We can make use of it. Therefore, the optical storage device equipped with the optical head of the present embodiment and controlling the focusing and tracking as described above can provide a high-quality output signal, high reliability, high performance, and a small size. As a result, the entire device can be downsized.

Note that, even when the blazed hologram element 65 is used as in this embodiment, the long directions of the photoelectric conversion elements 68 B and 69 A can be made parallel based on the above-described modification. Alternatively, the diffraction spots can be separated by changing the pattern pitch. Wear. Furthermore, the present invention can be similarly applied to the case where the light beam is separated on the return path as in the fifth embodiment.

(Example 7)

FIGS. 22 to 23 show a seventh embodiment of the present invention. In FIG. 22, the divergent light from the semiconductor laser 21 passes through the hologram element 75 and passes through the condenser lens 76. The beam is converged and forms a recording Z reproduction beam to be received on the recording medium 25. The reflected light travels backward in the optical path and is refracted by the condenser lens 76, and reaches the hologram element 75 again to generate ± first-order diffracted lights 78 and 79. The diffracted lights 78 and 79 form a two-point astigmatic light flux in a manner similar to the above-mentioned case that passes through the lens after diffraction, and when both light fluxes are focused, the emission end of the semiconductor laser 21 is focused. Connect the circle of least confusion on f.

Before and after focusing, the convergence position of the light beam moves rearward when the medium 25 is close, and moves forward when the medium 25 is far. Therefore, the same two photoelectric conversion elements 29 and 30 as in the first embodiment are provided in the plane of the emission end of the semiconductor laser 21 to perform focus detection. At this time, only the focusing lens 76 or the entire finite system 80 from the focusing lens 76 to the photoelectric conversion elements 29 and 30 is moved back and forth by an actuator (not shown) so that the focusing 'error signal obtained at this time becomes a constant value. By driving, the recording / reproducing beam can be always converged on the medium surface.

In this embodiment, unlike some of the above cases, the hologram element 75 is arranged in the convergent light path. When the hologram separates the convergent light beam, if the ± 1st-order diffracted light 78 and 79 are used together, a slight curve correction is required for the pattern. Even if the correction is performed, the astigmatism common to the two light beams is generated. As a result, the astigmatism of the primary light beam 78 is large, and the astigmatic difference of the + first light beam 79 is small. I cannot escape from the phenomenon. However, for example, when the diffraction angle of the light beam is smaller than about 15 ^{β and} the numerical aperture on the detection side is smaller than about 0.2, the necessary correction amount is small and the pattern shape is not much different from the hyperbola. In such a case, astigmatism generated at the time of separation is also small, and if a force that hardly causes a problem for detection is needed, the photoelectric conversion elements 29, 30 are required according to the diameter of the circle of least confusion. The detection sensitivity may be made uniform by changing the width of the detection.

In the collimating system, the diffracted light on the outward path by the hologram element is transmitted to the objective lens. It was easy to disperse the light outside the optical path as unnecessary light by adjusting the distance in the optical path. In a finite system, the distance to the condenser lens 76 is limited, so it is not so easy to take a sufficient distance, but if this distance is not enough, for example, 0 in the return path of the outgoing + 1st order light Since the next light overlaps with the minus first light of the return light of the 0th light on the outward path and interferes with the focus detection, the position of the hologram element 75 should be determined in consideration of this point. In addition, if the hologram element 75 is provided with an aperture stop by using unnecessary return light passing through an optical path distant from the optical axis as compared with the desired diffracted lights 78 and 79 on the return path, the above-described restriction is imposed. Can be reduced.

As shown in FIG. 23, a beam splitter 81 may be provided in the convergent light path, the light path may be divided into the forward path and the return path, and a finite system may be configured such that only the return path passes through the hologram element 75. In this case, unnecessary diffracted light on the outward path is not generated, so that the hologram element sets the diffraction efficiency of the 0th-order light to almost zero and increases the efficiency of the ± 1st-order light as in the previous embodiment. It is desirable. It is also preferable to improve the detection sensitivity by inserting a negative lens on the detection side as necessary and increasing only the vertical magnification on the detection side. Furthermore, if the detection lens is intentionally given an appropriate astigmatism, the above-mentioned unnecessary astigmatism generated in the hologram of the convergent light path can be canceled out, which is extremely effective.

Further, as a modification of the present embodiment, the hologram element 75 is of a split type similar to that of the second embodiment, and four photoelectric conversion elements are provided. In this case, tracking is also performed by driving the entire finite system from the condenser lens 76 to the photoelectric conversion element.

As described above, a finite optical head can be configured extremely simply by the present invention. Finite-type heads have few adjustment items during manufacturing, can be made even smaller, and have high reliability after manufacturing. Therefore, they are preferable for miniaturizing optical storage devices and ensuring reliability.

(Example 8)

FIGS. 24 to 26 show an eighth embodiment of the present invention, which shows another embodiment in which a finite system head is constructed, and which is used to eliminate the above-mentioned influence of unnecessary astigmatism. This is another configuration example. In FIGS. 24 and 25, the hologram element 85 is divided into two left and right regions 85A and 85B by a dividing line 85p as in the second embodiment. In each region, the diffraction direction is, for example, 80 in the clockwise and counterclockwise directions. Separated by rotation. Each of the regions 85A and 85B has a corrected hyperbolic pattern. As described above, the astigmatic difference of the diffracted light beam is large in the -first light beams 86A and 86B, and the + first light beam 87 and In the hologram element & 5 of the present embodiment, the astigmatism of the primary light flux 86B of one area 85B and the astigmatic difference of the + primary light flux 87A of the other area 85A are reduced in the hologram element & 5 of this embodiment. The focus distance f unique to each of the patterns of the areas 85A and 85B is changed so as to be equal.回折 The diffracted light beams 86 B and 87 A given equal astigmatic difference form the smallest circle of confusion with the same diameter on the same plane 76 f, and the convergence position of the light beam moves before and after focusing. I do. Since each light beam has the opposite astigmatic difference, at the minimum confusion circle position at the time of focusing, astigmatism spots and zots that change vertically to horizontally long ellipse are obtained.

Therefore, if the deformation of these two astigmatic spots 86B and 87A is detected and the differential is taken, a focusing error signal that crosses zero at the time of focusing can be obtained. In this embodiment, the photoelectric conversion elements 88B and 89A are divided elements having the peripheral areas 88Bs and 89As on the rain side of the central areas 88Bc and 89Ac as described above. The output difference between the central area and the peripheral area is used. On the other hand, the other diffracted light fluxes S 7 B and 86 A in each area will have astigmatic differences that differ greatly in magnitude. In this embodiment, the total light amount is not used for calculating the forcing-error signal. Is incident on the photoelectric conversion elements 89B and 88A, which are large enough to receive light. The operation of various signals is performed by the outputs VIA, V1Bc, VIBs, V2Ac, V2As, of the photoelectric conversion elements 88A, 88Bc, 88Bs, 89Ac, 89As, 89B. Using V2B, we can write First, the focusing error signal

(Vl B c -V l B s)-(V2 Ac -V2As)

= (VlBc + V2As)-(V2Ac + VlBs)

However, if there is a leakage of the tracking error signal as it is, to avoid this,

(V 1 B C -V 1 B S -V 2 B) One (V2Ac-V2As -V lA)

= (VlBc + V2As + VlA) One (V2Ac + VlBs + V2B)

It is preferred that Tracking error signal V 1 A-V 2 B

Or

V I A-(V l B c + V l B s)

(V2 Ac + V 2 As)-V 2 B

Moreover

(V2 Ac + V 2 As) one (V1Bc + V1Bs)

Any of (V2Ac + V2As + VIA)-(VIBc + VIBs + V2B) can be obtained. Furthermore, if the analyzer 47 extending over the splitting element and the analyzer 46 extending over the other two photoelectric conversion elements are provided at an inclined angle of mutual analysis similarly to the second embodiment, the magneto-optical signal is

(V1Bc + V1Bs + V2Ac + V2As) It can be obtained in one (V1A + V2B). In the above calculation of the tracking error signal, V 1 A-V 2 B

By selecting, (V1Bc + V2As) and (V2Ac + V1Bs) can be handled collectively, which is convenient because a connection can be made on the photoelectric conversion element. Furthermore, if the addition capacity of the photoelectric conversion element relating to the calculation of the magneto-optical signal (V1Bc + V2As + V2Ac + V1Bs) is made equal to the addition capacity relating to (V1A + V2B) It is preferable because common mode noise can be efficiently removed by differential detection.

As described above, according to the configuration of the present embodiment, the influence of unnecessary astigmatism when the astigmatism generating hologram is placed in the convergent light path can be eliminated in the detection stage. In addition, since both the ± 1st-order diffracted lights that change complementarily to each other are used, good focus detection is possible, and changes in the diffraction angle are long even with wavelength fluctuations. Thus, the advantage of the hologram can be fully utilized even when using a light source such as a semiconductor laser in which the emission wavelength is easily changed without the center of the differential being shifted.

In this embodiment, the force described for the type that separates the spot by changing the diffraction direction on the left and right of the dividing line 85p is also used for the type that separates the spot by changing the diffraction separation angle on the left and right as described above. Of course, it is of course possible to suitably configure.

As in the case of the seventh embodiment, it is effective to provide an open d stop in the hologram element 85 in order to ease the restriction on the arrangement position of the hologram element 85. In addition, the hologram element 85 of the present embodiment can be blazed in the same manner as in the sixth embodiment. That is, in FIG. 26, when the hologram element 85, is blazed so as to increase the light intensity of the light fluxes 86B, 87A having the same astigmatic difference, the light intensity of the other two face-folded lights (not shown) is obtained. Can be made almost zero, and only the two sets of photoelectric conversion elements 88 B and 89 A which are divided elements need to be provided. Assuming that the outputs of the photoelectric conversion elements 88 Bc, & 8 Bs, 88 Ac, and 88 As are Vic, Vis, V2 c, and V2 s, respectively, the focusing error signal is

(V1c + V2s) One (V2c + V1s)

Also, the tracking error signal is

(V 1 c + V 1 s)-(V2 c + V2 s)

Can be obtained at Further, if the analyzers 70 and 71 having different detection angles are provided in front of the respective photoelectric conversion elements 88 B and 89 A, the magneto-optical reproduction signal can be obtained.

C V 1 c + V 1 s) C V2 c + V2 s)

Is obtained. This is because the band of the magneto-optical signal, which is the same operation as the above tracking error signal, is high. Therefore, if the signal band is electrically separated, both can be obtained independently.

The optical head configured as described above has a small number of adjustment items at the time of manufacture because it is a finite system. — It can be made much smaller, and has high reliability after manufacturing. It is only necessary to dispose the photoelectric conversion elements 88B and 89A only on the side, which is preferable because the manufacture is easier.

In addition, in the case of such a blaze, there is almost no unnecessary diffracted light on the outward path overlapping with the diffracted light on the return path, so that there is no restriction on the arrangement position of the hologram element 85 ′, and the hologram element 85 ′ can be sufficiently moved from the light source. It can be placed at a remote location. In this case, the distance between the light source and the photoelectric conversion element can be increased while the diffraction angle of the hologram is kept small, so that the manufacturing is further facilitated and preferable.

In this case as well, since both the ± 1st-order diffracted lights that change complementarily to each other are used, good focus detection is possible, and the change in the diffraction angle with respect to wavelength fluctuation is a long light. The advantage of the hologram is achieved even when a light source such as a semiconductor laser is used, in which the center of the differential is not displaced and the emission wavelength is liable to fluctuate due to the detection means. Can be used for minutes.

(Example 9)

FIG. 27 shows a ninth embodiment of the present invention, and the same reference numerals as those described above denote the same functional members. The divergent light from the semiconductor laser 38 is bent at the beam splitter 91 and is made parallel by the collimator lens 39. An objective lens 40 is arranged in the parallel light beam, and the light passing therethrough forms a recording Z reproduction beam that converges on the storage medium surface 41. The objective lens 40 is movable in a direction perpendicular to the track groove of the storage medium 41, and the beam can be moved to a desired track by moving the objective lens 40. In addition, a lens shift sensor 92 for providing the amount of movement of the objective lens 40 at this time is provided. The light reflected by the medium surface is converted into a substantially parallel light beam again by the objective lens 40, travels backward in the optical path, is converged by the collimating lens 39, and is incident on the beam splitter 91. The light beam that travels straight here then enters the hologram element 95 through the negative detection lens 93 arranged. Here, the hologram element 95 is divided into two left and right regions 95A and 95B by a dividing line 95p as in the fourth embodiment, and the spots of each region are divided into the left and right regions. Is changed by changing the diffraction separation angle at. Each region has a corrected hyperbolic pattern, and generates four astigmatic light beams 96 A, 96 B, 97 A, and 97 B.

In order to receive these light beams, four pairs of photoelectric conversion elements 98 A, 98 Β, 99 A, and 99 B, which are arranged in a straight line and are long in the diffraction direction, similarly to the fourth embodiment. It is provided as a divisional element provided with a peripheral area in order to effectively use the light amount as necessary. Assuming that each photoelectric conversion output is V 1 A, V 1 B, V 2 A, V 2 B, the focusing error signal is

(V 1 A + V 1 B) one (V 2 A + V 2 B)

The objective lens 40 is driven in the focus direction so that the value becomes a constant value, and the recording Z reproduction beam can always be converged on the medium surface 41. Also, the tracking error signal is

(V 1 A + V 2 A) one (V 1 B + V 2 B)

Can be obtained. It is sufficient to move the objective lens 4 ° in the cross-track direction so that this takes a constant value, but in this configuration, it depends on the position of the objective lens 40. The error signal generates an offset. The lens shift sensor 92 is provided to correct the offset, and the offset can be removed by multiplying the output of the lens shift sensor by an appropriate coefficient and adding it to the tracking error signal. Therefore, if the tracking servo control of the objective lens 40 is performed so that the corrected tracking error signal has a constant value, the recording / reproducing beam can always be converged on the track.

According to the configuration of the present embodiment, since only the lightweight objective lens 40 can perform the tracking operation, it is suitable for use where high-speed tracking is required.

It is needless to say that a magneto-optical signal can be detected by providing an analyzer in the same manner as described above. In addition, the negative detection lens 93 provided for detection has a high vertical magnification to improve the focus detection sensitivity. Further, as described above, it is effective to intentionally impart astigmatism to the detection lens 93 to cancel unnecessary astigmatism generated in the hologram element 95 in the converging light path.

In this case, as in the case described above, all necessary signals can be obtained while being small in size and low in cost. In addition, all the outputs of the four photoelectric conversion elements can be used for the operation of any signal, and can be generated by an operation different from any of the signals, so that there is no waste of light amount and there is no crosstalk between signals. It is possible to obtain few and high quality signals. Furthermore, even when the wavelength of the light source fluctuates, there is no influence due to the movement of the diffraction lens, and the light source such as a semiconductor laser whose emission wavelength is liable to fluctuate without a shift of the differential center of focus detection. Even when used, the advantages of the hologram element can be fully utilized. Therefore, the optical storage device equipped with the optical head according to the present embodiment is supported by high-quality output signals, has high reliability and high performance, and can be downsized by the small head.

(Example 10)

FIGS. 28 to 29 show a tenth embodiment of the present invention. In FIG. 28, the divergent light from the semiconductor laser 21 is collimated by the collimating lens 22 and is oblique. To the reflection-type hologram element 100 which is arranged in the hologram. On the outward path, only the specularly reflected zero-order light passes through the objective lens 24 disposed at an appropriate distance to form a recording Z reproduction beam converging on the optical storage medium 25. Depends on the medium plane of the incident beam The reflected light becomes divergent light, travels backward, is converted into a substantially parallel light beam by the objective lens 24, and reaches the hologram element 100 again to be diffracted. The diffracted light is refracted by the collimating lens 22 and received by the photoelectric conversion elements 101 and 102 arranged in the same plane near the focal plane 22 f of the collimator lens 22. .

Here, the hologram element 100 is a pattern that generates a non-point-collected luminous flux similar to some of the preceding hologram elements by applying one-dimensional correction to the above-described hyperbolic pattern with respect to the inclination direction of the reflection surface. With the above configuration, it is possible to perform focus detection in the same manner as in the above-described embodiment. Further, it is a matter of course that the hologram element 100 is of a split type as in the second embodiment, and four photoelectric conversion elements are provided to form the same optical head and optical storage device as in the embodiment.

When the hologram element 100 is arranged obliquely as described above and the diffraction direction in which the light beam is generated is set to the inclined direction, one of the diffracted light beams becomes the same as when the hologram element is arranged in the convergent light path. The astigmatism of the other beam becomes smaller and the astigmatism of the other beam becomes smaller, or the angle of the diffracted light from the specularly reflected light differs for ± 1st order light, and the distance of the robot from the center is two Changes such as differences appear. For this reason, it is more preferable that the direction of diffraction of the light beam by the reflection hologram element 100 be in a direction perpendicular to the tilt direction than in the case shown in the figure.

In the case where the reflection hologram element 100 is constituted by the segmented hologram element 100, as described above, if the reflection hologram element 100 is blazed to use one light flux in each area, the above-described astigmatism is obtained. The problem of the difference in the distance can be avoided, and good focus detection is possible even when the diffraction direction is made coincident with the tilt direction, which is preferable.

Further, even if the hologram element 105 is a reflection type in a finite optical system as shown in FIG. 29, a similar detection system can be configured by performing one-dimensional correction as in this embodiment. In this case as well, it is more preferable that the diffraction direction in which the luminous flux is generated is orthogonal to the inclination direction. They can also be placed. The effect obtained by brazing is the same as described above.

(Example 11)

FIG. 30 shows an eleventh embodiment of the present invention, in which the photoelectric conversion element 29 or the photoelectric conversion element 30 has the same configuration as that of the first embodiment, as shown in FIG. 4 strips The light receiving areas 110a, 110b, 110c, 110d are arranged in parallel to form a quadrant element 110.

In this configuration, when the medium goes out of the focus position, the shape of the projected light spot 31 changes from a vertical ellipse to a horizontal ellipse as shown in FIG. Assuming that the output of the receiving area is V1, V2, V3, V4 from the left, respectively

(V2 + V3) one (V I + V4)

Thereby, a focusing error can be detected.

On the other hand, if the track direction of the medium is parallel to the dividing direction of the quadrant 110, and if the light beam deviates from the track, the projected light spot 31 will be as shown in FIG. Because the position of can swing from side to side

(V 1 + V 2) one (V3 + V)

Thus, a track error can be detected.

It should be noted that the quadrant 110 may be replaced with either one of the photoelectric conversion elements 29 and 30, or one of them may be used.

In the first to eleventh embodiments, the calculation for obtaining various signals may be performed in a manner that the addition and the subtraction are reversed depending on the modification of the equation, but this is a change within the scope of the present invention.

Industrial applicability

As described above, in the focus detection mechanism according to the present invention, two photoelectric conversion elements for obtaining a differential output can be arranged in the same plane, so that manufacturing with improved dimensional accuracy is easy. Furthermore, the advantage of the hologram element can be fully utilized even when a light source such as a semiconductor laser whose emission wavelength is liable to be changed without the center of the differential being shifted with respect to the wavelength change. Further, the optical head of the present invention has a configuration with an extremely small number of parts, is small in size and low in cost, and can efficiently obtain a signal required for the optical storage device. Signal and various error signals. Further, the optical storage device of the present invention equipped with the above-mentioned optical head can be realized at a low cost with a simple configuration and high performance. As described above, the present invention has a great effect in this field, and the possibility of using the present invention is extremely high.

Claims

The scope of the claims

1. A detection optical system that converges the reflected light from the focusing target surface,

A hologram element arranged in the detection optical system,

A pair of astigmatic diffracted light beams whose beam cross-sectional shapes diffracted by the hologram element change complementarily are detected by the pair of light detection means;

A focus detection mechanism for detecting the focus on the target surface by calculating the difference between the outputs of the pair of light detection means;

2. A detection optical system that converges the reflected light from the focusing target surface,

A hologram element arranged in the detection optical system,

3. The hologram element is a blazed hologram element. 3. The focus detection mechanism according to claim 2, wherein:

4. The focus detection mechanism according to claim 1, wherein the detection optical system is common to a projection optical system that causes a light beam to enter the target surface.

5. The detection optical system is at least partially independent of the projection optical system, and a magnification of the detection optical system is different from a magnification of the projection optical system. 4. The focus detection mechanism according to claim 1 or claim 3.

6. The detection optical system is at least partially independent of the projection optical system, and the detection optical system excluding the hologram has an astigmatic difference in the diffraction direction of the hologram element. 4. The focus detection mechanism according to claim 1, wherein:

7. The light detecting means includes a long light detecting element and another light detecting element surrounding at least a part of the light detecting element, and an output of a difference between the two is used as an output of the light detecting means. 7. The focus detection mechanism according to claim 1, wherein the focus detection mechanism comprises:

8. A light source comprising the focus detection mechanism according to claims 1 to 7, which is used for detecting the focus of a reproduction or recording light beam on the surface of an optical recording medium. Ko

9. The optical head according to claim 8, wherein a recording bit of said optical storage medium is reproduced using an output of said optical detection means.

10. The optical head according to claim 8, further comprising an analyzer in front of said light detecting means, for reproducing a recording bit by magneto-optical recording of said optical recording medium. De.

11. The light detecting means is divided into two by a splitter corresponding to a track tangential direction of the optical recording medium surface, and a tracking error of the light beam is detected based on a difference between outputs of the divided light detecting means. The optical head according to claim 8, wherein the optical head is characterized in that:

1 2. A detection optics system that collects the reflected light of the reproducing or recording light beam from the optical recording medium surface,

A hologram element arranged in the detection optical system,

A pair of light detection means groups disposed on the same plane that is substantially conjugate to the target surface in lieu of the detection optical system; Each of the pair of light detection means groups comprises two light detection means, and the longitudinal direction of the light detection means is arranged substantially along the direction of diffraction by the hologram element;

The hologram element is divided into two by a dividing line corresponding to a track tangent direction of the optical recording medium surface, and each of the divided areas is substantially in-phase with a hyperbolic group or a corrected hyperbolic group substantially in line. Having a periodic light modulation rate pattern,

When the beam cross-sectional shape changes with the same tendency, and the light beam group including the two astigmatic diffraction light beams from different regions of the hologram element is defined as the astigmatic diffraction light beam group, the beam cross-sectional shape changes complementarily. A pair of astigmatic diffracted light beams are detected by a pair of the light detection means groups,

-Taking the output sum of the light detection means of each of the pair of light detection means groups, calculating the difference between the pair of output sums, and detecting the focus on the target surface;

The two astigmatic diffracted light beams diffracted from the same area of the hologram element are detected by the light detecting means to obtain a total output, and a difference between the two total outputs is calculated to calculate a tracking error of the light beam. Light head characterized by detection.

13. The optical head according to claim 12, wherein the detected bit of the optical storage medium is reproduced by using a detection output of the optical detection means.

14. The optical head according to claim 12, wherein an analyzer is provided on a front surface of the light detecting means, and the recording bit is reproduced by magneto-optical recording on the optical storage medium.

15. The light modulation rate pattern is arranged so that complementary astigmatic diffracted light beams from different regions of the hologram element come close to each other, and two sets of the diffracted light beams that are close to each other are received. 15. The light head according to claim 14, further comprising an analyzer having a different azimuth of a transmission axis with respect to each pair on a front surface of the light detecting means.

16. The light detecting means comprises a long light detecting element and another light detecting element surrounding at least a part of the light detecting element, and outputs the difference between the two to the output of the light detecting means. 16. The optical head according to claim 12, wherein the optical head is used as a force.

1 7. Detection light that converges the light reflected from the optical storage medium of the reproduction or recording light beam Academic and

A hologram element arranged in the detection optical system,

A longitudinal direction of the light detecting means is arranged substantially along a diffraction direction by the chopper element,

The hologram element is divided into two by a dividing line corresponding to the tangent and tangential directions of the surface of the optical recording medium, and the divided areas are substantially in-phase with each other in a hyperbolic group or a corrected hyperbolic group. And has a periodic light modulation rate pattern and is blazed,

The astigmatic diffracted light beams diffracted by different regions of the hologram element are mutually difficult,

A pair of the astigmatic diffracted light beams, which are diffracted by different regions of the hologram element and whose beam cross-sectional shapes change additively, are detected by a pair of the light detection means. An element and another light detection element surrounding at least a part of the light detection element,

—A light head characterized in that a tracking error is detected by calculating a difference between outputs of the pair of long light detecting means.

18. The light head according to claim 17, wherein the output sum of the long light detection element and the another light detection element surrounding at least a part of the light detection element is calculated. A light head characterized in that a tracking error is detected by calculating a difference between a pair of the output sums.

19. The recording bit of the optical storage medium is reproduced by using a detection output of the photodetecting means, wherein the recording bit is reproduced. Light head.

20. The apparatus according to claim 17, wherein an analyzer is provided in front of said light detecting means, and reproduction of recording pits by magneto-optical recording of said optical recording medium is performed. Item 18 to the light described in box 18.

21. The astigmatism diffracted light beam is separated by rotating the light modulation rate patterns by different angles, respectively. 21. The claim 12 through claim 20. Light head.

22. The astigmatism diffraction light beam is separated by setting the light modulation rate patterns to have different periods, respectively. Light head.

23. The light head according to claim 12, wherein said detection optical system is common to said light beam projection optical system.

2 4. The detection optical system is at least partially independent of the light beam projection optical system, and the magnification of the detection optical system is different from the magnification of the projection optical system. The optical head according to claim 12 or claim 22.

25. The detection optical system is at least partially independent of the projection optical system of the light flux, and the detection optical system excluding the hologram has astigmatism in the diffraction direction of the hologram element. Features Claims 1 to 2 or Claims 2

Optical head according to item 2.

26. The optical head according to claim 8 or claim 10 for irradiating a reproduction or recording light beam onto the optical recording medium, and a focus detection result of the optical head according to claim 8 or 10. An optical storage device, comprising: focusing means for performing focusing based on the following. 27. The optical head according to claim 11 or claim 25, wherein the optical storage medium is irradiated with a reproduction or recording light beam, and a focus detection result of the optical head. An optical storage device comprising: focusing means for performing focusing on the basis of: and tracking means for performing focusing based on the detection result of the tracking error of the optical head. Claims captured

[Accepted by the International Bureau on April 9, 1993 (09.04.93); Claims 1-27 as originally filed were captured

Range was replaced with 1-35. (Page 6) I

A hologram element arranged in the detection optical system,

A pair of light detection means arranged on the same detection plane that is substantially conjugate with the target surface with respect to the detection optical system,

The hologram element generates a pair of astigmatic light beams that form a minimum circle of confusion on the detection plane and whose astigmatic directions are orthogonal to each other,

-Detecting the pair of astigmatic light beams by the pair of light detection means;

A focus detection mechanism for detecting focus on the target surface by comparing outputs of a pair of the light detection means.

2. The focus detection mechanism according to claim 1, wherein the hologram element has a light modulation rate pattern substantially along a hyperbolic group or a corrected hyperbolic group.

3. A detection optical system that converges the reflected light from the focusing target surface,

A hologram element arranged in the detection optical system,

The hologram element is divided into two or more regions, and forms a pair of astigmatic convergent light beams that form a minimum circle of confusion on the detection plane and whose astigmatism directions are orthogonal to each other, from two different regions. Occurs

Detecting the pair of astigmatic convergent light beams by the pair of light detection means,

A focus detection mechanism for detecting focus on the centroid by comparing outputs of the pair of light detection means;

4. The focus detection mechanism according to claim 3, wherein each region of the hologram element has a light modulation rate pattern substantially along a hyperbolic group or a captured hyperbolic group.

5. The focus detection mechanism according to claim 3, wherein the hologram element is blazed.

6. The focus detection mechanism according to claim 1, wherein the detection optical system is common to a projection optical system that causes a light beam to enter the target surface.

7. The detection optical system is at least partially independent of the projection optical system, and the magnification of the detection optical system is different from the magnification of the projection optical system. 6. The focus detection mechanism according to claim 1 or claim 6.

8. The detection optical system is at least partially independent of the projection optical system, and the detection optical system excluding the hologram element has an orientation parallel or perpendicular to a main diffraction surface of the hologram element. 6. The focus detection mechanism according to claim 1, wherein the astigmatism is given.

9. The light detecting means is composed of a long light detecting element and another light detecting element surrounding at least a part of the light detecting element, and a difference between outputs of both the light detecting element and an output of the light detecting means. 9. The focus detection mechanism according to claim 1, wherein the focus detection mechanism is used.

10. A focus detection mechanism according to claim 1 to claim 9, wherein the focus detection mechanism is used for playback or focus detection of a recording light beam on an optical recording medium surface. Light head.

11. The optical head according to claim 10, wherein a recording pit of said optical storage medium is reproduced using an output of said optical detection means.

12. The apparatus according to claim 10, wherein an analyzer is provided on a front surface of the light detecting means, and reproduction of recording bits by magneto-optical recording of the optical recording medium is performed. An optical head according to item 11.

13. The light beam is divided into two parts by a dividing line corresponding to a track tangent direction of the optical recording medium surface, and the output of the divided light detecting means is compared with the light beam. The optical head according to claim 10, wherein the tracking error is detected.

1 4. A detection optical system for converging the reflected light of the reproducing or recording light beam from the optical storage medium surface,

A hologram element arranged in the detection optical system,

And two pairs of light detection means disposed on the same detection plane that is substantially conjugate with the optical storage medium surface with respect to the detection optical system,

The hologram element is divided into at least two regions by a dividing line corresponding to a track tangential direction of the optical recording medium surface, From the two regions of the hologram element, a pair of astigmatic convergence light beams that form a circle of least confusion on the detection plane and whose astigmatism directions are orthogonal to each other are generated by being separated from each other,

Two pairs of the astigmatic light beams are detected by two pairs of the light detection means,

By comparing the outputs of the light detecting means belonging to the same pair, the focusing on the optical storage medium surface is detected,

An optical head characterized in that a tracking error of the light beam is detected by comparing outputs of the light detecting means belonging to different pairs. -

15. The light head according to claim 14, wherein each region of said hologram element has a light modulation rate pattern substantially along a hyperbolic group or a captured hyperbolic group.

16. The tracking error of the light beam is calculated by substantially obtaining the difference between the output sum of the light detection means belonging to the same pair and the output sum of the light detection means belonging to the other same pair. The optical head according to claim 14 or claim 15, characterized in that the optical head is detected.

1 -7. The optical storage medium is calculated by substantially obtaining a difference between the output sum of one set of the light detection means belonging to a different pair and the output sum of another set of the light detection means. 17. The optical head according to claim 14, wherein focus on a surface is detected.

18. The optical head according to claim 14, wherein a recording pit of the optical recording medium is reproduced by using a detection output of the photodetecting means.

19. The photodetector according to claim 14, further comprising an analyzer in front of said light detecting means, for reproducing recorded bits by magneto-optical recording of said optical recording medium. Light head as described in section.

20.In front of the two groups of light detection means, two groups are provided with analyzers having different transmission axis azimuth angles, and the outputs of the light detection means belonging to different groups are compared. 20. The optical head according to claim 19, wherein recording bits are reproduced by magneto-optical recording on said optical storage medium.

21. The light detecting means comprises a long light detecting element, and another light detecting element surrounding at least a part of the light detecting element, and outputs an output of a rain difference to the light detecting means. Out The optical head according to claim 14, wherein the optical head is used as a force.

2 2. A detection optical system that converges the reflected light of the reproducing or recording light beam from the optical recording medium surface,

A hologram element arranged in the detection optical system,

A pair of light detection means disposed on the same detection plane that is substantially conjugate to the optical storage medium surface with respect to the detection optical system;

The light detection means includes a long light detection element and another light detection element surrounding at least a part of the light detection element,

The hologram element is divided into at least two parts by a dividing line corresponding to a track tangent direction of the optical storage medium surface, and forms a minimum circle of confusion on the detection plane, and the directions of astigmatism are orthogonal to each other. Generated as a pair of astigmatic convergent light beams separated from each other from the two different regions,

By comparing the output difference between the output of the long light detecting element and the output of the another light detecting element surrounding the long light detecting element with respect to the pair of the light detecting means, focusing on the optical recording medium surface is performed. To detect

—A light head characterized by detecting a tracking error of the light beam by comparing outputs of only the pair of long light detecting elements.

23. The light source according to claim 22, wherein each region of the hologram element has a light modulation rate pattern substantially along a hyperbolic group or a corrected hyperbolic group.

24. The optical head according to claim 22, wherein said hologram element is blazed.

25. The optical head according to claim 22 or claim 24, wherein the output sum of the long photodetector and the another photodetector surrounding the long photodetector is calculated. A light head characterized by detecting a tracking error of the light beam by comparing a pair of the light detection means.

26. The light according to claim 22 or 25, wherein the recording pit of said optical storage medium is reproduced by using a detection output of said light detecting means. 33 He o

27. The method according to claim 22, wherein an analyzer is provided in front of said light detecting means, and reproduction of recording bits by magneto-optical recording of said optical recording medium is performed. 26. A light head according to item 26.

28. In the two divided areas of the hologram element, the astigmatic light beams are separated from each other by arranging the diffractive surfaces of the respective areas at an angle to each other. 27. The light according to claim 27 or claim 27.

29. In the two divided areas of the hologram element, the non-point convergent light beams are separated from each other by selecting diffraction angles of the respective areas different from each other. The optical head according to claim 4 to claim 27.

30. The optical head according to claims 14 to 29, wherein said detection optical system is common to said light beam projection optical system.

'31. The detection optical system is at least partially independent of the light beam projection optical system, and the magnification of the detection optical system is different from the magnification of the projection optical system. The optical head according to claim 14 to claim 29.

32. The detection optical system is at least partially independent of the light beam projection optical system, and the detection optical system excluding the hologram has an astigmatism in a direction parallel or perpendicular to a main diffraction surface of the hologram element. The optical head according to claim 12, wherein the optical head has an aberration.

33. The optical head according to claim 10 or claim 12 for irradiating a reproduction or recording light beam onto the optical recording medium, and focusing on the optical head 'and the optical head according to claim 10. An optical storage device comprising: focusing means for performing focusing based on a detection result.

34. The optical head according to claim 13 or claim 32, wherein the reproducing or recording light beam is irradiated onto the optical recording medium, and the focus detection of the optical head. An optical storage device comprising: focusing means for performing focusing based on a result; and tracking means for performing tracking based on a detection result of the tracking error of the optical head.

35. An optical head for irradiating a reproduction or recording light beam onto the optical recording medium and outputting four types of photoelectric conversion outputs distinguished by a first output to a fourth output,

Effectively, [1st output + 2nd output)-[3rd output + 4th output] 3s

Detecting the focus of the light beam on the optical storage medium surface;

Substantially calculating (first output + third output) one (second output + fourth output) to detect a tracking error of the light beam on the optical recording medium surface;

An optical recording method comprising: performing substantially (first output + fourth output) 1 [second output + third output] to reproduce a magneto-optical recording bit on the optical storage medium surface; Billion devices,

Statements under Article 19 of the Convention Claims shall be collected in order to further clarify the features of the present invention by making the wording of claims and the composition of the claims appropriate based on the embodiments. The details are as follows. Claim 1 extracts the basic structure from claim 1 at the time of filing, and uses appropriate expressions to further clarify the features of the focus detection mechanism of the present invention. It is. Claim 2 is an appropriate representation of the features of the hologram element described in claim 1 at the time of filing, and further clarification of the features. Claim 3 extracts the basic structure from claim 2 at the time of filing, and uses appropriate expressions to further clarify the features of the focus detection mechanism of the present invention. It is. The fourth range of the feedback appropriately expresses the characteristics of the hologram element described in the second claim at the time of filing, and further clarifies the characteristics. You. Claim 5 is the same as Claim 3 at the time of filing, with the text being arranged in a timely manner and the number of the cited claim being changed. Claim 6 is the same as claim 4 at the time of filing, except that the number of the cited claim is changed. Claim 7 is the same as claim 5 at the time of filing, except that only the number of the cited claim is changed. Claim 8 is the same as claim 6 at the time of filing. Clarified features by using appropriate expressions, and changed the number of the cited claim. It is. Claim 9 is the same as claim 7 at the time of filing. The text has been rearranged using appropriate expressions, and the number of the cited claim has been changed. is there. Claim 10 is the same as claim 8 at the time of filing, except that only the number of the cited claim is changed. Claim 11 is the same as claim 9 at the time of filing, except that the number of the cited claim is changed. Claim 12 is the same as claim 10 at the time of filing, except that the number of the cited claim is changed. Claim 13 is a claim that clarifies the features by using appropriate expressions in claim 11 at the time of filing and cites the claim. The number has been changed. Claim 14 extracts the basic structure from claim 12 at the time of filing, and uses appropriate expressions to make the characteristics of the optical head of the present invention more clear. It has become Claim 15 properly expressed the features of the hologram element described in claim 12 at the time of filing and clarified the features. It is a thing. Claim 16 provides an appropriate representation of the tracking error detection features described in claim 12 at the time of filing, and describes the features in more detail. It is clarified. Claim 17 is an appropriate representation of the features of focus detection described in claim 12 at the time of filing, and clarifies the features. is there. Claim 18 is the same as claim 13 at the time of filing, except that the number of the cited claim is changed. Claim 19 is the same as claim 14 at the time of filing, except that the number of the cited claim is changed. Claim 20 describes appropriately the characteristics of reproducing the recording bit of magneto-optical recording described in claim 15 at the time of filing, and makes the characteristics clearer. It has become Claim 21 is the same as claim 16 at the time of condyle, except that the number of the cited claim is changed. Extract the basic feature from claim 17 at the time of filing, and clarify the characteristics of the optical head of the present invention using appropriate expressions. It is. Claim 23 is a statement that appropriately expresses the features of the holographic element described in claim 17 at the time of filing and clarifies the features. You. Claim 24 is an 'appropriate representation of the features of the holographic element described in claim 17 at the time of filing, and further clarification of the features. You. Claim No. 25 of the claim shall contain the number of the claim that clarifies the features by using appropriate expressions in the claim 18 at the time of filing and cites the claim. Has been changed. Claim 26 is the same as claim 19 at the time of filing, except that only the number of the cited claim is changed. Claim 27 is the same as claim 20 at the time of filing, except that the number of the cited claim is changed. Claim 28 states that the features of claim 21 at the time of filing were clarified by using appropriate expressions, and the number of the cited claim was changed. It has been changed. Claim 29 states the features of the claim 22 at the time of filing by clarifying the features by using appropriate expressions. The claim number has been changed. Claim 30 is the same as claim 23 at the time of filing, except that the number of the quoted claim is changed. Claim 31 is the same as claim 24 at the time of filing, except that only the number of the cited claim is changed. Claim 32 is a clarification and use of features by using appropriate language in claim 25 at the time of filing. The claim number has been changed. Claims. Paragraph 33 is a variation of Claim 26 at the time of filing, with the only change being the number of the cited claim. Claim 34 is the same as claim 27 at the time of filing, except that the number of the cited claim is changed. Claim 35 is newly created within the range disclosed in the specification at the time of filing, and is characterized by a signal operation applied to the optical storage device of the present invention. Is clarified.