JPH06274926A - Optical member, polarization separating element, optical head and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a high-reliable optical head capable of simplifying its assembly process and eliminating its adjustment process, and small in a secular change or a temperature change, and to attain miniaturization by drastically combining functions. CONSTITUTION:An optical path length adjusting function which makes the optical path length of a going luminous flux 101f different from the optical path length of a returning luminous flux 101r, polarization separating function which detects an magneto-optical signal, or luminous flux reflecting function which guides one part of a luminous flux to a second light receiving element 170 for detecting an emitting power are set on an integrated optical member 120. The optical member is used as the cover of a package 80 of an optical head 1, and the light receiving element 170 or a light emitting element 10 are integrally housed. Thus, the initial offset of a focusing error signal can be removed, and the adjustment can be eliminated. Also, the detection of the magneto-optical signal or the emitting power can be attained by the integrated optical head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head used in an optical disk device or the like, and more particularly to an optical member or a polarization separation element which is a constituent member of the optical head.

[0002]

2. Description of the Related Art A conventional optical head of this type is disclosed in US Pat.
P-No. As disclosed in US Pat. No. 4,764,912, bulk (square) type optical parts made by shaving and polishing optical glass are often used, and in particular, an optical head of a type that also detects a magneto-optical signal does not require a polarizing prism or the like. there were.

[0003]

However, in the above-mentioned optical head, the bulk type optical component occupies a large volume,
Since the processing itself is expensive, and there are various positioning points during assembly, it has been difficult to reduce the size, cost, and weight of the device. Therefore, the performance in terms of access speed is sacrificed, which hinders its spread in the market. Also, the layout of the optical system is such that the light emitting element and the light receiving element are separated,
Dedicated optical parts are used for the forward optical system starting from the light emitting element and the returning optical system starting from the light receiving element, which is very wasteful in terms of the number of parts and space efficiency. Further, since the position accuracy is accumulated, it is difficult to ensure the position accuracy of the optical system, and a laborious adjustment work is required to remove the initial offset of the detection signal, especially the focus error signal.

The present invention is intended to solve such a problem, and its main purpose is to drastically reduce the number of optical components, reduce the size and weight, and simplify the adjustment process.

[0005]

An optical member and a method of manufacturing the same according to the present invention for solving the above-mentioned problems include (1) an integral member through which a divergent or convergent outward light flux and a backward light flux are transmitted. The optical path length of the light flux and the optical path length of the return light flux are different, (2) Regarding (1) above, the optical member is integrally molded and has a step on the surface, (3) Above (1) With regard to the above, the optical member is formed by bonding at least two separate components, and a step is formed on the surface in the state where the separate components are bonded together. (4) The optical member as the manufacturing method according to (1) above. Injection molding with transparent resin to form a step on the surface. (5) As a manufacturing method of the above (1), the optical member is integrally press-molded with glass to form a step on the surface. Characterize.

The structure of another optical member of the present invention is as follows.
(6) It is configured such that it has at least a binary refractive index locally, the forward light flux and the backward light flux pass through regions of different refractive indexes, and the forward light flux and the backward light flux have different optical path lengths. (7) The integrated member transmits the outward light flux and the backward light flux, and the refraction power of the area through which the outward light flux passes is different from the refractive power of the area through which the backward light flux passes. (8) The above (7) is characterized in that a convex or concave curved surface is locally formed on the surface.

Further, an optical head of the present invention comprises (9) the optical member described in (1), (6) or (7) above, and a light receiving element arranged behind the optical member so as to face the optical members. The optical flux is composed of a light emitting element which is arranged slightly higher or slightly lower than the light receiving surface of the light receiving element, and the forward light flux emitted from the light emitting element and the backward light flux reflected by the optical recording medium toward the light receiving element are both included in the optical member. (10) Regarding (9) above, it is configured to detect a change in the spot shape of the returning light flux on the light receiving element and generate at least a focus error signal. ) Regarding the above (9), the optical member is formed of a transparent resin and has a flange on the outer periphery, and a gate for injection molding is installed on the flange portion. (12) Regarding the above (9), the optical member is made of a transparent resin. Formed of optical components Forming or printing alignment marks for alignment on the surface or the back surface and the surface of the light receiving element, (13) Regarding the above (9), forming a diffraction grating or hologram on the surface or the back surface of the optical member, ( 14) Regarding (13) above, the hologram is
It is a blazed hologram which is blazed in a triangular tooth shape in units of diffraction groove pitch.

Another optical head according to the present invention comprises (15) the optical member described in (1), (6) or (7) above, and a light receiving element arranged behind the optical member so as to face the optical members. ,
A light emitting element arranged slightly higher or slightly lower than the light receiving surface of the light receiving element, and a package for holding the light receiving element and the light emitting element are provided, and by cooperation of the optical member and the package,
Sealing the light receiving element and the light emitting element, (16) above (1)
Regarding 5), the optical member and the package are fixed to each other via an adhesive, and the adhesive has a lower hardness after curing than the materials of the optical member and the package.

The polarization splitting element and the manufacturing method thereof according to the present invention have (17) a first optical member and a second optical member bonded to the first optical member. The optical member is formed with a recess including a slope, the slope is coated with a dielectric multi-layered thin film to provide a polarization separation function, the recess is filled with a transparent resin or liquid, and the first and second optical members are bonded together. (18) Regarding the above (17), the refractive index of each of the first optical member, the second optical member, and the transparent resin or liquid that fills the recess is approximately the same. Regarding the above item (17), the light beam incident on the slope is a convergent light beam or a divergent light beam having an NA (numerical aperture) equivalent to 0.15 or less in the medium, (20) The above (1)
Regarding 7), the slopes and the depressions are formed at a plurality of locations in the integrated optical member, and the plurality of slopes are coated with a common multi-layered thin film of a dielectric. (21) As the manufacturing method of (17) above, A dielectric multilayer function is provided on the slope to provide a polarization separation function, the recess is filled with a transparent resin, and the first and second optical members are bonded together, and then an annealing treatment is performed. (22) Optical member Formed by fixing or holding a polarizing plate or a polarizing film on the surface or inside thereof, (23) As the manufacturing method of (22) above,
An annealing treatment is performed after a polarizing plate or a polarizing film is fixed or held on the surface or inside of the optical member.

Another configuration of the optical head of the present invention is (2
(4) The polarization separating element according to (17) or (22) is used, and the return light flux transmitted through the polarization separating element is received by a light receiving element to detect a magneto-optical signal.
5) Using the polarization beam splitting element described in (17) above, the forward beam flux and the backward beam are transmitted to the first and second slopes having the polarization separating function, respectively, and the return beam is transmitted through the second slope of the polarization beam splitting element. (26) With respect to (25) above, the polarization plane of the outgoing light flux is made to coincide with the polarization transmission direction of the first inclined surface, and the return light flux is polarized. The polarization separation direction of the second inclined surface is set to be rotated by about 45 degrees with respect to the surface, and further, (27) an optical member separated into a mirror-finished area and an irregular reflection area having fine unevenness is provided. It is configured to transmit the outward light flux and the backward light flux to the mirror finish area, (2
8) Using an optical member separated into an area where the antireflection coating is deposited and an uncoated area where the antireflection coating is not deposited, the central portion of the divergent light flux emitted from the light emitting element is transmitted to the antireflection coating area, Having a second light receiving element for detecting the emission power, which reflects a part of the divergent light flux in the coating area and receives the reflected light,
(29) Regarding the above (28), the second for detecting the emission power
And a first light receiving element for receiving a return light flux that is reflected light of the optical recording medium, and the first and second light receiving elements are formed on an integrated substrate, (30) An optical member having a reflecting surface formed in a region where the outward light flux and the backward light flux are not transmitted is used, and a second light receiving element for detecting the emission power is provided, which reflects a part of the outward light flux by the reflecting surface and receives the reflected light. (31) Regarding the above (30), the reflecting surface is a slope or a curved surface, and the surface reflection light flux or the total reflection light flux of the slope or the curved surface is configured to be received by the second light receiving element. To do.

[0011]

According to the above configuration of the present invention, (A) the optical components relating to the forward optical system and the backward optical system can be made common, and the light emitting element and the light receiving element can be stored in a common package.

(B) The optical path length of the forward path and the optical path length of the return path can be set to different values, a spot can be accurately irradiated on the light receiving element, and it is particularly effective for removing the initial offset of the focus error signal.

(C) The adjustment concerning the removal of the initial offset of the focus error signal can be simplified.

(D) It becomes easy to position the optical component and the light receiving element.

(E) A polarization separation element for detecting a magneto-optical signal can be combined and integrated with other optical components.

(F) The emission power of the light emitting element can be monitored without adding any special component.

A number of actions are produced mainly by the above. As a whole, by adopting integrally molded optical members and polarizing elements,
A large number of functions can be combined, the size can be reduced, and the adjustment process can be simplified.

[0018]

【Example】

(Embodiment 1) FIG. 1 is a side sectional view showing an optical head in Embodiment 1 of the present invention, and FIG. 2 is a side sectional view of an optical pickup using the present optical head. In FIG. 1, 10 is a light emitting element composed of a semiconductor laser, 120 is an optical member called a cover plate, 130 is a hologram which is a curved diffraction groove for separating light beams, 170 is a light receiving element which is a multi-divided photodiode, A package 80 holds and stores the light emitting element 10 and the light receiving element 170. The package 80 is a frame body having an opening on only one side, and the opening surface is covered with the optical member 120 to be adhered and sealed. The optical head 1 of this embodiment is formed by combining these elements. The optical head 1 has a light source and a detection optical system integrated with each other, and has a composite function as will be described later, and has a small cubic external shape of about 5 mm square as a whole.

In FIG. 2, reference numeral 2 denotes an optical pickup case in which the above-mentioned optical head 1 is housed. Further, the mirror 40 and the objective lens 50 are also housed, and they are integrally driven (focusing servo, tracking servo) as a whole. The objective lens 50 is the only lens and constitutes a finite compact optical system. Specifically, the distance between object points and image points (total track) of the objective lens 50 is as short as about 15 mm, so that the case 2 is small and lightweight, and the entire optical pickup in this embodiment is about 2 g.
It will be as light as r. Reference numeral 60 is an optical recording medium, that is, an optical disc, in which track grooves (not shown) with a minute pitch are formed on the recording surface.

In FIG. 1, a step L is formed on the surface of the optical member 120 called a cover plate, which is close to the light emitting element 10, and is divided into a plane portion 121 and a step portion 122. The optical member 120 is made of PMMA (polymethylmethacrylate), PC (polycarbonate), or A.
Injection molding of an optical resin such as PO (amorphous polyolefin) can be performed by a simple method, and low-melting glass can be molded by hot pressing.

Here, it is practically impossible to mount the light emitting element 10 on the light receiving surface of the light receiving element 170, that is, on the same plane as the surface. This is because the light receiving element 170 is manufactured by a semiconductor manufacturing process, and a semiconductor wafer is diced into small pieces to form an outer shape, so that a through hole cannot be formed in the central portion. Although it is possible to mount the light emitting element 10 on the light receiving element 170, since the emission surface 11 (see FIG. 4) of the light emitting element 10 and the opposite surface 12 are interfaces for internal reflection of the laser chip, The light receiving element 170 and the like must not be in contact with the light receiving element 170, and must be fixed using the bottom surface 14 as shown in FIG. In this embodiment, in order to minimize the number of parts, as shown in FIG. 3 and FIG. 4, a recess 171 and a slope 172 are formed in a substantially central portion of the light receiving element 170, and a recess 172 is formed.
The light emitting element 10 is fixed horizontally, and the light flux 100 emitted from the emission surface 11 is reflected by the inclined surface 172 and emitted as a divergent light flux 101a in a direction perpendicular to the plane of the light receiving element 170. The slope 172 is inclined at about 45 °, and the depression 171
At the same time, it can be relatively easily formed on the light receiving element 170 made of a silicon substrate by anisotropic etching. By depositing a gold thin film on the slope 172, a reflection surface having excellent reflection efficiency can be obtained.

A point to be noted here is that when the light emitting element 10, that is, the laser chip is mounted as described above,
As shown in FIG. 4, a virtual light emitting point 1 obtained by mirror-moving the light emitting point 14 of the light emitting element 10 with the slope 172 of the light receiving element 170 as a boundary.
5 is inevitably downward from the light receiving surface of the light receiving element 170 (see FIG.
To the left). At the present time when surface emitting semiconductor lasers have not been established in technology, it is not possible to integrally manufacture a light receiving element and a light emitting element in a complete monolithic type in a continuous process, and a separate laser chip, that is, a light emitting element 10 is manufactured by such a method. Mounted on the light receiving element 170, and the slope 17
The best method is to use 2 to emit the light flux 101f in the vertical direction. Therefore, the virtual light emitting point 15 is located at a position lower than the light receiving element 170, and specifically, is lowered by about 0.08 mm in this embodiment.

If we are prepared to increase the number of parts,
For example, a stem (rectangular metal block, not shown) is fixed to the surface of the light receiving element 170, and the light emitting element 10 is attached to the side surface thereof.
It is also conceivable that the components are mounted in parallel (that is, perpendicular to the light receiving element 170). In this case, the light emitting point of the light receiving element 10 is shifted upward from the light receiving element (not shown). In any case, there is no choice but to mount the light-emitting point on the light-receiving surface of the light-receiving element 170 slightly downward or upward.

Next, returning to FIGS. 1 and 2, the optical behavior of the optical head of this embodiment will be described. The outward light flux 101f, which is a divergent light flux emitted from the light emitting element 10, is the optical member 1
The hologram 13 formed on the surface of the optical member 120 after being incident on and transmitted through the substantially central portion, that is, the flat surface portion 121 of 20.
0 is emitted, and the 0th-order light 102f (light flux not diffracted by the hologram 130) enters the mirror 40 and the objective lens 50. Light flux 10 condensed by the objective lens 50
3f images the spot 104 on the recording surface of the optical recording medium 60. The light flux 103r reflected by the optical recording medium 60 follows the opposite optical path to become the light flux 102r, and the hologram 130.
Return light flux 10 which is +/- 1 order light which is incident on and diffracted
1r is transmitted through the inside of the optical member 120, is emitted from the step portion 122, and is incident on the light receiving surface of the light receiving element 170, that is, the surface.

As shown in FIGS. 5 and 6, the hologram 1
Reference numeral 30 is divided into two corresponding to the radial direction of the optical recording medium 60, that is, the direction orthogonal to the track groove, or in other words, the push-pull modulation direction. Two kinds of hologram patterns 1
The patterns 30a and 130b are designed so as to diffract and separate into two light fluxes of +/- 1 order and a total of four return light fluxes 101r, and at the same time generate remarkable astigmatism. As shown in FIG. 7, in the light receiving element 170, a strip-shaped light receiving pattern 173, which is divided into four parts independently, is formed by a semiconductor process.
The light flux 101r is condensed on each of the three light receiving spots 10
5 is formed. The shape of the light receiving spot 105 changes according to the focus error due to the astigmatism described above, and the light receiving pattern 1
The amount of light taken into 73 changes. In the present embodiment, this change in the light quantity is photoelectrically converted as a focus error signal (so-called astigmatism method), and the light quantity difference between the light fluxes transmitted through the two-division patterns 130a and 130b of the hologram 130 is photoelectrically converted as a track error signal (so-called so-called astigmatism method). Push-pull method).

Here, in FIG. 6, in the reference state where the amount of focus error is zero, the backward light flux 101r irradiated on the light receiving element 170 is at the center of the astigmatic difference (focal line interval) D, that is, the circle of least confusion 103. Must be set to position. As a result, astigmatism D is evenly distributed before and after the position of the circle of least confusion 103 as shown in FIG. 6, so that when the focus error is in the reference state, as shown in FIG. 7 or FIG. The light receiving spot 105 having the shape of the circle of least confusion is formed, and the amount of light taken into each of the channels 173a to 173d of the light receiving pattern 173 becomes uniform. Here, in each channel, the focus error signal 106 generated by the addition / subtraction operation of (173a-173c) + (173d-173b) = (173a + 173d)-(173b + 173c) becomes zero. Next, when the distance between the optical recording medium 60 and the objective lens 50 changes and the amount of focus error increases, the degree of convergence of the backward light flux 101r changes according to the principle of geometrical optics, and the focal line 1
The position 04 is shifted in the optical axis direction. Then, FIG. 8 (a)
Alternatively, as shown in FIG. 8C, the shape of the light receiving spot 105 changes to an ellipse, the amount of light taken into each channel of the light receiving pattern 173 changes, and the level of the focus error signal 106 changes. The astigmatic difference is set to D, and the objective lens 50
Let R be the magnification (horizontal magnification: image side / object point side), and let d be the value indicating the focus error in the area where the focus error signal changes monotonically, d = D * (R * R ) / 2, and the focus error signal 106 changes with a curve as shown in FIG. In the case of the present embodiment, the magnification of the objective lens 50 is about 1 / (1) in consideration of the processing difficulty and the distance between object points and image points.
Since it is set to 4 times, the relationship is actually d = D / 32.

The above-mentioned focus error signal 106 and the above-mentioned track error signal are used as error signals for focusing servo and tracking servo, respectively, and are controlled so that the spot 104 is accurately imaged on the optical recording medium 60. In the present invention, the details of the servo system are not important because they are not important. However, in order to accurately control the focusing servo, the focus error signal 106 in the reference state is zero, that is, there is no initial offset. It is essential to set to.

As described above, in this embodiment, a finite optical system is formed, and as shown in FIG. 1 and FIG.
And the focus of the objective lens 50 (the position of the spot 104) are in an optically conjugate relationship. Further, the focal point of the backward light flux 101r, in this case the circle of least confusion 103, and the focal point of the objective lens 50 are also in a conjugate relationship. Therefore, an optical conjugate relationship is established between the virtual light emitting point 15 and the circle of least confusion 103. Here, if the virtual light emitting point 15 and the circle of least confusion 103 are placed on the same plane in the optical axis direction, the light receiving spot shape on the light receiving element 170 becomes the circle of least confusion 103 in the reference state, and the focus error signal 106 shows No offset occurs.

However, as described above with reference to FIG. 4, the virtual light emitting point 15 is about 0.08 m from the light receiving surface of the light receiving element 170.
m behind. Also shown in FIG. 10, the hologram 130
The image plane 107 (which may be considered as a plane including the circle of least confusion 103) of the +/− 1st order light formed by
Because of the geometrical optical aberration caused by 0 or the hologram 130, it is curved to the front side (close to the optical member 120), and it is possible to automatically correct the deviation of the virtual light emitting point 15 to some extent. However, it is difficult to design the amount of curvature of field (indicated by W in FIG. 10) and the amount of deviation of the virtual light emitting point 15 to coincide with each other under various actual constraint conditions. In case of
The amount of field curvature W is 0.13 with respect to mm, which is overcorrection. After all, a deviation of 0.05 mm remains, which is about 1.6 μ when converted into the focus error signal 106.
It becomes an offset of m.

Therefore, if this is left as it is, an initial offset occurs in the focus error signal 106. In order to remove this, in the present embodiment, a step is provided on the surface of the optical member 120 called the cover plate as described above. The optical path length is adjusted. This is a very simple method and is a characteristic item of the present invention. When the level difference between the surfaces 121 and 122 is L, the refractive index of the optical member 120 is n (= 1.
5), the optical path length to be corrected is Δs (= 0.13 mm-
0.08 mm = 0.05 mm), L = nΔs / (n-1) = 1.5 * 0.05 / (1.5-1). Therefore, when L = 0.15 mm is set, the positional difference between the virtual light emitting point 15 and the light receiving element 170 in the optical axis direction is corrected, and the initial offset of the focus error signal 106 is canceled.

As a feature of this embodiment, it is a great advantage that the step of adjusting the initial offset of the focus error signal can be omitted. Since the accuracy of the step L is directly transferred to the accuracy of the mold, the accuracy of the step L is sufficiently within the dimensional tolerance of +/− 10 μm. When this tolerance is replaced with the change in the image plane position of the backward-direction light flux 101r based on the virtual emission point 15, Δs = L * (n-1) / n = 10 μm * (1.5-1) /1.5 = 3.3 μm. Further, if this Δs is converted into the amount of focus error, that is, the initial offset, it is 3.3.
Since /32=0.1 μm, which is within a sufficient error with respect to a general offset allowable value (about 1 μm or less), no adjustment can be performed without any problem.

In this embodiment, the surface 122 is higher than the surface 121 by the step L, that is, the optical path length of the return path is extended with respect to the optical path length of the outward path. However, the return light flux 101
When the curvature of field of r is small (when the diffraction angle by the hologram is shallow, etc.), the optical path length may be adjusted in the direction in which the optical path length of the backward light beam 101r is shortened. In this case, the surface 122 is a surface. A step may be formed so as to be concave with respect to 121.

In addition, although the so-called astigmatism method is used as the method for detecting the focus error signal 106 in this embodiment, the present invention is not limited to this, and a focus error detection method such as a spot size method is also applicable. The same problem may occur, and it can be said that the problem is peculiar to an optical head in which the light emitting element 10 and the light receiving element 170 are housed in the same package 80. Therefore, the present invention and this embodiment can be widely applied to this type of optical head. Further, the optical member 120 may be formed by bonding separate optical components instead of integrally molding to form a step L on the surface, but the dimensional accuracy is slightly sacrificed.

Further, the main purpose of the optical member 120 in the present embodiment is that the optical path length of the forward light flux 101f and the optical path length of the backward light flux 101r can be set to different lengths, but conceptually, A member that allows a plurality of light beams to pass therethrough, and is for freely setting the optical path length of each member. Therefore, in addition to the optical head, it is a device that includes an optical system,
The application range of the present invention can be expanded even when there are a plurality of converging light fluxes or divergent light fluxes passing in close proximity.

(Second Embodiment) FIG. 11 is a side sectional view showing an optical head according to a second embodiment. In this embodiment, the basic specifications of the optical system are similar to those of the above-mentioned embodiment, but the hologram 230 formed on one surface of the optical member 220 has a small triangular groove having a sawtooth shape in the diffraction groove cross section direction. 2 is different from the optical member 220 in that a simple diffraction grating of linear grooves, that is, a grating 240 is formed on the other surface of the optical member 220.

Since the hologram 230 is blazed, it is well known that the backward light beam 201r, which is the diffracted first-order light, is known.
Is diffracted only on one side. Therefore, the focus error signal cannot be detected by the operation detection using the astigmatism as in the first embodiment, and instead, the focus error signal called the double knife edge method (or Foucault method) as known is used. Can be detected with (details omitted). Also, the track error signal is, as is also known, a signal obtained by using the +/− 1st order light 201b generated in the grating 240.
It can be detected by the beam method.

This embodiment uses the hologram 230 as described above.
The number of diffracted light fluxes generated in 1 is half that in the first embodiment, and therefore, the light receiving pattern on the light receiving element 270 (not shown)
Is brought to one side, the light receiving element 270 and the package 80 can be made smaller. Also, the grating 24
Since 0 can also be formed integrally with the optical member 220, the combination of functions is progressing. Therefore, as a functionally simple optical head that only reproduces a CD (compact disc), a very small optical head can be provided. Note that FIG.
The stepped portion 222 provided on the optical member 220 at 1 is provided to adjust the optical path length of the outgoing light flux (first-order diffracted light) 201r in the same manner as in Embodiment 1 and cancel the initial offset of the focus error signal. ing.

(Third Embodiment) In the first embodiment described above, the optical member 120 having the step L is used to correct the positional deviation in the optical axis direction between the minimum circle of confusion 103 of the returning light beam 101r and the virtual light emitting point 15. Was there. However, there are other means for correcting the optical path length.

The third embodiment shown in FIG. 12 is characterized in that the optical path length is changed by locally changing the refractive index. That is, the material B (3) having a different refractive index from the material A (321) around the optical member 320 is partially present.
22) is included. As a specific manufacturing method, a so-called two-color molding method using two-stage injection molding is used. For example, the material B (322) is injection-molded using a small mold, a part of the mold is replaced, and the periphery thereof is injection-molded with the material A (321). As specific materials, material A ... PMMA (refractive index of about 1.5) and material B ... PC (refractive index of about 1.6) are selected. In this case, unlike the first embodiment, the extreme difference in refractive index between resin and air is not used, and therefore it is necessary to maintain the difference in refractive index over a long distance in the optical axis direction. Assuming that the refractive index of the material A is nA, the refractive index of the material B is nB, the optical path length to be corrected is ΔS, and the distance at which the refractive index difference exists is L, then L = nB * Δs / (nB-nA) = 1.6 * 0.05 / (1.6-15) Therefore, it suffices to set L = 0.75 mm. Since the refractive index is a value specific to the material and can be managed very accurately, there is an effect that the optical path length can be adjusted more accurately than in the case of the first and second embodiments.

Instead of molding the material B (322) with the end faces on the same plane as shown in FIG. 12, the material B may be completely enclosed inside the material A. Further, instead of the two-color molding method as described above, a method of fitting separate parts having different refractive indexes may be used, but the dimensional accuracy is slightly disadvantageous. Furthermore,
If the material is not limited to resin, it is possible to locally change the refractive index by a method such as ion doping like a gradient index lens (so-called GRIN lens).

(Embodiment 4) As Embodiment 4, another method of correcting the optical path length will be described. In FIG. 13, a lens surface 422 is locally formed on the flat surface 421 of the optical member 420. In this case, instead of using the difference in refractive index as described above, refraction by the lens is positively used to shift the focal length, that is, the focal position. A concave lens surface may be formed for a light beam whose optical path length is desired to be extended, and a convex lens surface may be formed for a light beam whose optical path length is desired to be reduced. However, in order to apply it to the optical head as described in the first embodiment, it is necessary not to give unnecessary aberration to the light beam, and the lens surface 422 is preferably an aspherical shape.

(Embodiment 5) FIGS. 14 and 15 show another type of optical head constructed by using a cover plate or optical member 520 as Embodiment 5. In this embodiment, the principle of the optical system is the same as that of the first embodiment, except that the shape of the optical member 520 is different and the hologram element 530 is provided as a separate body.
0 back surface 521 and hologram element 530 front surface 531
A plurality of alignment marks 522, 532, 5 at the same plane direction position on the surface of the light receiving element 570.
72 is formed (FIG. 15). These alignment marks are for alignment during assembly, are cross-shaped lines with a line width of about 10 μm, and are formed by etching, die engraving, or the like. In this type of optical head, the positional accuracy of the light receiving spot 505 with respect to each channel of the light receiving pattern 573 of the light receiving element 570 is determined by the diameter of the light receiving spot 505 (in other words, the circle of least confusion) in order to ensure the quality of the detection signal. On the other hand, it should be about 10% or less. In this embodiment, the diameter of the light receiving spot 505 is about 15
0 μm, therefore the alignment accuracy is +/− 15 μm
Is required. However, the alignment mark (52
2,532,572) can be formed by etching with a photomask, so +/− 5 μm for each part
It is possible to mark with a certain positional tolerance. Therefore, if the alignment marks are aligned and positioned through the optical axis direction during assembly, the light receiving pattern 573 and the light receiving spot 505 can be aligned at a level of +/− 10 μm.

Next, a method of assembling the optical head of this embodiment will be described. In FIG. 14, a light receiving element 570 and a light emitting element 1 which is a laser chip mounted in a recess 571 on the light receiving element 570.
0 is fixed inside the frame of the package 80. This fixing method is usually a brazing method using silver paste. The planar outer shape of the package 80 is the optical member 520.
The outer surface has a flat shape, and the opening surface has good flatness. Next, a small amount of the adhesive material 85 is applied to the opening surface of this package, the optical member 520 is placed, and the alignment mark 522 is aligned with the alignment mark 572. The material 85 is cured.

In this embodiment, an acrylic UV (ultraviolet) curable resin having excellent workability is used as the adhesive 85, and the adhesive hardness after curing is relative to the hardness of the optical member 570 and the package 80. Very soft ones are selected. Since the package 80 requires molding of metal wiring, generally, a material such as epoxy resin or ceramics is used, while the optical member 520 uses optical resin such as PMMA as described in the first embodiment. The coefficient of thermal expansion between them differs by more than one digit. When these two materials are firmly bonded, stress is generated in the optical member 520 with respect to temperature change, and optical characteristics such as transmitted wavefront aberration and birefringence are deteriorated. Therefore, the adhesive material 85 that joins these members must be an extremely soft material that absorbs the difference in the coefficient of thermal expansion. Experimentally, it has been confirmed that if the Shore A scale hardness is about 60 after curing, optical distortion is hardly given to the optical member 520. This hardness is positioned to be relatively soft in the hardness after curing of a general adhesive, and the optical member 5
Compared with the hardness of 20 materials (PMMA and PC), the hardness is about one digit.

FIG. 16 shows the optical member 520 in a single shape. The optical member 520 has a planar shape of about 5 mm square, and a flange portion 524 is formed on the outer peripheral portion thereof. In this embodiment, the method of manufacturing the optical member 520 is premised on injection molding using a mold, and the gate 525 which is a resin flow port at the time of injection adopts a side gate method provided on the outer peripheral side surface of the flange 524. ing.

The effect of the flange portion 524 is to firstly improve the rigidity of the whole, and secondly to equalize the pressure of the resin flowing from the side gate type gate 525 during molding. In the optical head of this embodiment, the optical member 520
Among them, the effective region where the optical characteristics should be ensured is the region having a diameter of about 2 mm at the central portion. When optical distortion due to stress occurs in the central portion 526, optical characteristics such as transmitted wavefront aberration and birefringence are deteriorated, and reliability of information recording / reproducing of the optical head is significantly deteriorated. If the flange portion 524 is formed on the outer peripheral portion as in the present embodiment, the rigidity is significantly improved against external force and thermal deformation, and the stress generated in the central portion 526 is greatly relieved. Further, during injection molding, the flow pressure of the resin is uniformly relieved by the flange portion 524, and the residual stress after molding can be made almost zero in the central portion 526, which also contributes to the improvement of the optical characteristics. .

(Embodiment 6) Embodiment 6 is an embodiment relating to the polarization beam splitting element of this embodiment. The polarization separation element described here is an optical element for use in an optical head or the like of a magneto-optical disk device that requires reproduction of a magneto-optical signal (MO signal). The main purpose of this embodiment is to manufacture a polarization separation element for detecting a magneto-optical signal by a simple method, which is a great change from the conventional manufacturing method. Hereinafter, FIG. 17, FIG. 18, and FIG.
This embodiment will be described with reference to FIG.

In FIG. 17, the first optical member 620 has a recess 621 and a slope 622 of about 45 degrees formed in the center. The first optical member 620 is integrally injection-molded with an optical resin such as PMMA (polymethylmethacrylate), and can be manufactured in large quantity and at low cost. On the other hand, the second optical member 6
Reference numeral 30 denotes a plane parallel plate, which is manufactured by ordinary optical glass cutting because it does not include a curved surface or an inclined surface, and can also be supplied in large quantities at low cost.

FIG. 18 shows a state in which the first optical member 620 and the second optical member 630 are combined to form the polarization separation element 601. The recess 621 of the first optical member 620,
It is filled with resin 640 and covered with the second optical member 630.
The chemical composition of the resin 640 is adjusted so that the refractive index after curing is about 1.5, which is equivalent to that of the first and second optical members. The resin 640 filled in the recess 621 in the state where the first and second optical members are combined functions as a triangular prism. In this embodiment, the resin 640 is U
Although a V (ultraviolet) curing resin is used and UV irradiation is performed after the combination to cure the resin, a thermosetting resin or the like may be used.

A dielectric multi-layer thin film is coated (deposited) on the inclined surface 622 or the entire area of one surface of the first optical member 620 as shown in FIG. 19 to form a dielectric A (625) and a dielectric B (6).
26) are alternately laminated. This is a vapor deposition method usually called multi-coating, but in the present embodiment, it is taken into consideration that the first optical member 620 serving as a base material is resin. That is, since the heat resistant temperature (glass transition point; TG) of the resin (PMMA is assumed in this example) is about 80 ° C., which is extremely low compared to glass, the temperature is set to about 70 ° C. or less during vapor deposition. ing. Further, since the coefficient of thermal expansion of the resin is large, the vapor deposition material is selected in consideration of the occurrence of cracks due to stress strain with the vapor deposition material. Specifically, dielectric A ... MgF2 (magnesium fluoride), refractive index =
1.3 Dielectric B ... ZrO2 (zirconium oxide), refractive index =
2.2 are alternately laminated with a film thickness of 0.3 to 0.4 λ (where λ is a wavelength used; approximately 780 nm), and P polarized light or S at the interface between them is laminated.
By stacking the differences in the transmittance due to the polarized light, a desired polarized light transmission characteristic can be obtained.

Here, the portion filled with the resin 640 and the first optical member 620 of FIG. 18 are the above-mentioned multilayer thin film (625,
626) to function as a so-called polarization beam splitter. As a result of the experiment, the optimal number of layers of the vapor-deposited thin film was in the range of 10 to 20 for the dielectrics A and B, and the S-polarized light transmittance with respect to the P-polarized light transmittance (the transmittance of the P wave 651) was finally obtained. A polarized light transmission characteristic having a ratio of (transmittance of S wave 652), that is, an extinction ratio of about 100: 1 was obtained.

It can be said that the combination of the vapor deposition materials shown above is only one example, but no change in characteristics due to temperature change or the occurrence of cracks is observed, and a polarization separation element 601 that can be sufficiently used can be provided. However, in order to secure the extinction ratio,
It is premised that birefringence due to residual stress does not occur inside the resin 640 after assembly. Therefore, in this embodiment, an aryling treatment is performed at the end of the manufacturing process to remove the residual stress inside the resin 640. The annealing conditions include
It may be about 1 hour at 70 ° C.

By the way, the incident angle θ (center value 45) of the light beam incident on the polarization separation element 601 having the above-mentioned structure.
It should be noted that the above extinction ratio changes depending on the (degree). That is, when the incident angle θ changes, the effective film thickness of the dielectrics A and B changes, so that the reflection / transmission characteristics of light rays change. The incident angle θ at which the extinction ratio (about 50: 1 or more) necessary for detecting the magneto-optical signal can be secured even with the optimum film thickness control is about +/− 9 in terms of the incident angle inside the polarizing element 601. It has been confirmed as a result of optical simulation and experiment that the degree is limited. This corresponds to the convergence (or divergent light flux) of NA 0.15 in terms of NA (numerical aperture) in the medium.

In addition, in addition to the advantage that the polarization separation element 601 shown in this embodiment is easy to manufacture, the shape accuracy of the optical member 620, especially the surface accuracy of the slope 622, is the same as the conventional method for cutting glass. There is a remarkable advantage that it is significantly relaxed as compared with the case of the polarization beam splitter. The reason for this is that the resin 640 fills even if the surface accuracy of the slope 622 is poor.
The refractive index of 40 is 0.0 with respect to the refractive index of the optical member 620.
Even if they differ by about 3, the slopes 622 can be used without problems in terms of optical characteristics as long as the slope 622 has a surface accuracy (waviness) of about 20 μ or less. This is the required value of the slope accuracy of the triangular prism that constitutes the conventional type polarization beam splitter,
This means that it will be alleviated about 20 times. Moreover, since parts can be manufactured by injection molding, a very small outer shape can be manufactured, and when applied to an optical head for magneto-optical detection, a very small detection optical system can be realized.

In this embodiment, the recessed slope 622 is molded with the resin 640. However, if the peripheral sealing property is good, the same function can be exhibited even if a liquid such as silicon oil is filled. In this case, there is an advantage that it is easy to avoid the problem of birefringence that the resin 640 had to pay attention to.

(Seventh Embodiment) FIG. 20 shows a seventh embodiment.
7 shows another type of polarization splitting element. In this embodiment, the function of the polarization beam splitter described in Embodiment 6 is replaced with a polarizing film or a polarizing plate.

In FIG. 20, the optical member 720 is formed of an optical resin, and the polarizing plate 740 is fitted and fixed in the depressed portion. The polarizing plate is a glass plate in which fine silver particles are mixed and heated and stretched to have a polarizing function, which has excellent performance, that is, an extinction ratio, but is not limited to this, and a film containing iodine is stretched. A polarizing film made by the above method may be used.
However, such a polarizing film generally has poor heat resistance,
The film, which had been stretched in a high temperature environment, had a drawback that its polarization characteristics were deteriorated due to shrinkage due to residual stress.

The advantage of this embodiment is that the polarizing plate or the polarizing film is lined with a much stronger optical member 720 than those, so that even a polarizing film having poor heat resistance shrinks in a high temperature environment. It will be difficult. Therefore, it is possible to obtain the polarization separation element 701 having excellent environment resistance characteristics.
However, if there is a slight shear shift in the adhesive layer that fixes the optical member 720 and the polarizing plate or the polarizing film 740, the polarizing plate or the polarizing film 740 may be slightly shrunk, and a long-term aging may occur. As a preventive measure, in this embodiment, an aryling process is performed after the assembly process to relieve the residual stress in advance and prevent the change over time. The annealing conditions may be 70 ° C. for about 1 hour.

(Embodiment 8) Embodiment 8 is an application of the polarization separation element shown in the above-mentioned Embodiment 6 to an optical head for detecting a magneto-optical signal, and will be described below with reference to FIGS. 21, 22 and 23. explain.

In FIG. 21, the optical member 820 is similar to the optical member 620 shown in the sixth embodiment, and the concave slopes are three types of slopes 828a, 828b, 828 having different slope directions.
made of c.

Further, in this embodiment, a hologram element 830 is used instead of the second optical member 630 of the sixth embodiment, and the polarization separation element 801 is constituted by these, and the functions are compounded. The optical member 820 is formed on the recessed slopes 828a to 828c.
A resin having a refractive index of about 1.5, which is equivalent to the refractive index of, is filled in three places. FIG. 22 shows the optical head in the assembled state. The optical member 820 has the polarization separation function described in the sixth embodiment, and also has the optical path length adjusting function for the return light flux described in the first embodiment. Is characteristic.

FIG. 23 is a plan view of the optical head as seen from the direction of the optical axis, showing each of the parts shown in FIG. 22 as seen through. In the figure, arrows 829 indicate the directions of the three inclined surfaces formed on the optical member 820, that is, the polarization transmission direction, and the central inclined surface 828c is along the junction surface of the light emitting element 10, that is, the polarization plane. On the other hand, slopes 828a, 828b on both sides
Is inclined by about 45 degrees with respect to the direction of the slope 828c.

In the present embodiment, a magneto-optical disk is assumed as the optical recording medium (not shown), and the specifications of the optical head are the return light flux 801 generated when reflected by the optical recording medium.
The Kerr rotation angle in r is detected as a modulation component. The light beam incident on the optical recording medium is linearly polarized light,
In this embodiment, P-polarized light is formed on the slope 828c. Therefore, the outward light flux (801f in FIG. 22) passes through the slope 828c with almost no loss. In addition, the return light beam 801r
(A total of four luminous fluxes) Two luminous fluxes form a pair and the slope 828
a and 828b, the slopes 828a and 828b are about 45 degrees in different directions as described above.
Since it is rotated by a degree, the Kerr rotation angle, which is the magneto-optical signal modulation component included in the backward light flux 801r, can be detected by differentially detecting it after polarization transmission in the direction of 45 degrees orthogonal to each other.

By the way, 3 formed on the optical member 820
There is no functional problem even if the central slope 828c is omitted among the recessed slopes. However, in this embodiment, the slope is intentionally formed from the viewpoint of the method of manufacturing the component, and the multilayer thin film of the dielectric as described in Embodiment 6 is coated thereon. The reason is that if there is no slope 828c and the surface is flat, then when the dielectric thin film is vapor-deposited, the outgoing light flux 801 is generated.
When the incident angle of f becomes 0 degree, a large amount of light is reflected without transmitting the outward light flux 801f. On the contrary, in order not to coat this minute portion, a delicate and precise masking process is required. Because it will be necessary. That is, it can be said that the slope 828c exists as a dummy. However, there is also a secondary effect that the extinction ratio of the laser beam emitted from the issuing element 10 is improved and the quality of the magneto-optical signal is slightly improved by utilizing the polarization separation function, that is, the filter effect by the sloped surface 828c. .

(Embodiment 9) Embodiment 9 is an application of the polarization separating element shown in the above-mentioned Embodiment 7 to an optical head for detecting a magneto-optical signal, and is shown in FIGS. 24 and 25.

In this embodiment, the polarization separating function by the recessed slopes 828a and 828b as described in the above-mentioned Embodiment 8 is replaced with the polarizing plates 940a and 940b. Therefore, the polarization transmission directions of the polarizing plates 940a and 940b shown in FIG. 25 are the slopes 828a and 82 of Example 8, respectively.
It corresponds to the direction of 8b.

In this embodiment, as shown in FIG. 24, the polarizing plates 940a. In the state where the optical member 920 is fitted and fixed to the optical member 920, the polarizing plate projects by a step L from the plane of the optical member 920. This has the same meaning as the step L described in the first embodiment, and is provided in order to cancel the initial offset of the focus error signal by adjusting the optical path length of the returning light flux.

(Embodiment 10) Embodiment 10 is one in which functions other than those described above are added to the optical member 1020, and is shown in FIG.

On the surface of the optical member 1020 on the light emitting element 10 side, a mirror-finished flat surface portion 1021 and stepped portion 1022 are formed.
In addition to the above, the irregular reflection surface 1023 formed of minute irregularities is integrally formed. The minute unevenness present on the irregular reflection surface 1023 is a roughened surface having unevenness height and pitch of several λ to several tens of λ (where λ is a wavelength used), and is partially embossed or sandblasted (sand) in the injection molding die. It is formed by subjecting the roughened mold surface to transfer during molding.
On the other hand, the plane portion 1021 and the step portion 1022 are required to efficiently transmit the outward light fluxes 1001f and 1001r of the optical system. It is possible to do

In this type of optical head, since the light emitting element 10 and the light receiving element 1070 are close to each other, the divergent light flux emitted from the light emitting element 10 is incident on the entrance pupil of the objective lens (not shown) for use. Except for the central light flux, there is a possibility that it will be reflected inside the optical head and return to the light receiving element 1070. This is called stray light, which is added to the detection signal as DC noise and deteriorates the signal quality. Therefore, it is desirable to eliminate it as much as possible. From this point of view, in the present embodiment, the irregular reflection surface 1023 is provided as a measure for absorbing unnecessary stray light generated in the optical head. The irregular reflection surface 1023 absorbs stray light, and at the same time, diffuses stray light that has not been completely absorbed and diffuses the stray light in all directions, and makes it uniformly incident on each light receiving pattern on the light receiving element 1070 (similar to 173 of the first embodiment). As a result, there is an effect that noise is not added to various detection signals that are differentially detected.

In order to enhance the effect of absorbing stray light by the irregular reflection surface 1023, it is more effective to apply a black paint or the like to this surface (so-called black-painting), which is in accordance with the purpose of this embodiment. .

(Embodiment 11) In Embodiment 10, the stray light is removed, but among the light flux emitted from the light emitting element, unnecessary peripheral light flux is positively utilized.
This is the present embodiment.

In FIG. 27, the divergent light flux emitted from the light emitting element 10 is reflected by the 45-degree inclined surface 1172 formed on the light receiving element 1170 by etching. Of this light flux, the light flux in the central portion is incident on the optical member 1120 as a forward light flux 1101f. In the present embodiment, this forward light flux 11
A non-reflective coating is vapor-deposited only on the area 1121 where 01f is transmitted. If this antireflection coating is subjected to multilayer vapor deposition (multicoating), a surface having an extremely low reflectance of 0.5% or less can be obtained. On the other hand, the non-coated area surface 1122 on which the antireflection coating is not applied
Has a reflectance of about 5% based on the Fresnel equation.

On the upper surface of the light receiving element 1170, the light emitting element 1
The second light receiving element 1 having a relatively large area separated from 0
175 is integrally formed. As shown in FIG. 27, the peripheral light flux 1101b reflected by the non-coating area 1122 is received by the second light receiving element 1175. The peripheral light flux 1101b is proportional to the light amount of the outward light flux 1101f, which is the light flux in the central portion, and is also proportional to the light emission power of the light emitting element 10. Therefore, the signal received by the second light receiving element 1175 and photoelectrically converted (power monitor signal 1176)
By checking, it is possible to monitor the light emission power, that is, the objective lens output power. Also, this power monitor signal 117
If 6 is fed back to the drive current control circuit (not shown) of the light emitting element 10, an APC (auto power control) control system can be configured, and the light emitting power of the light emitting element 10 can be accurately controlled to ensure stable operation. Information recording / reproduction becomes possible.

(Embodiment 12) Embodiment 12 corresponds to Embodiment 11
This is an embodiment for more positively taking in the unnecessary peripheral light flux described in 1) into the second light receiving element.

In FIG. 28, the outgoing light flux 1201f is incident on the antireflection coating region 1221 of the optical member 1220. On the other hand, the light flux 1201b in the peripheral portion is the optical member 1
It is reflected / focused by the curved surface 1223 formed integrally with 220, and can be efficiently incident on the second light receiving element 1275. Therefore, the signal level of the power monitor signal 1276 is improved, and more accurate APC control becomes possible.

Note that although 1223 is formed as a curved surface in FIG. 28, the effect can be expected even if it is an inclined surface. Also, curved surface 1
Instead of using the surface reflection of 223, it is also possible to use another shape to perform total reflection. Further, even if the curved surface and the inclined surface are formed by separate members and are combined with the optical member 1220, the functions are the same, and they belong to the gist of the present invention.

Finally, each of the above-described embodiments can be applied not only individually, but also by combining the contents of the invention of each embodiment as appropriate to further enhance the functional combination.

[0079]

As described above, according to the present invention, the optical components related to the forward optical system and the backward optical system can be made common, and the light emitting element and the light receiving element can be housed in a common package. Then, the optical path length of the forward path and the optical path length of the return path can be set to different values to accurately irradiate the spot on the light receiving element, which is very effective especially for removing the offset of the focus error signal. In addition, the adjustment process related to the removal of the offset can be eliminated, and the positioning of the optical component and the light receiving element is easy, so that the assembling process can be simplified and at the same time, there is little change over time or change in temperature, which is highly reliable. An optical head can be provided.

Further, the polarization separation element for detecting the magneto-optical signal can be combined and integrated with other optical parts, and stable signal detection with little change over time can be performed.

Further, the emission power of the light emitting element can be monitored without adding any special component.

Various effects such as the above can be obtained.

In addition, since an integrally formed optical member and a polarization separation element are adopted and a hologram element is integrated, a large number of functions can be combined, the size can be reduced, and the adjustment process can be simplified. The impact on the equipment market is large.

[Brief description of drawings]

FIG. 1 is a side sectional view of an optical head including an optical member according to a first embodiment.

FIG. 2 is a side sectional view of an optical pickup including the optical head of the first embodiment.

FIG. 3 is a perspective view showing a light emitting element and a light receiving element of the optical head of the first embodiment.

FIG. 4 is a front sectional view showing a light emitting element and a light receiving element of the optical head of the first embodiment.

FIG. 5 is a plan view showing a hologram of the optical head of the first embodiment.

FIG. 6 is a perspective view showing a hologram function of the optical head according to the first embodiment.

FIG. 7 is a plan view showing a light emitting element and a light receiving element of the optical head of the first embodiment.

8A, 8B, and 8C are explanatory views showing changes in a light receiving spot of the optical head according to the first embodiment.

FIG. 9 is a graph showing a focus error signal of the optical head of the first embodiment.

FIG. 10 is an explanatory diagram showing field curvature of the optical head according to the first embodiment.

FIG. 11 is a side sectional view showing an optical head according to a second embodiment.

FIG. 12 is a side sectional view showing an optical member of Example 3.

FIG. 13 is a side sectional view showing an optical member of Example 4.

FIG. 14 is a side sectional view showing an optical head of Example 5.

FIG. 15 is a plan view showing an optical head of Example 5;

FIG. 16 is a perspective view showing an optical member in the optical head of Example 5.

FIG. 17 is a perspective view showing a polarization beam splitting element of Example 6.

FIG. 18 is a sectional view showing a polarization beam splitting element of Example 6;

FIG. 19 is a sectional view showing a multilayer thin film of the polarization beam splitting element of Example 6;

FIG. 20 is a perspective view showing a polarization beam splitting element of Example 7.

FIG. 21 is a perspective view showing a polarization beam splitting element of the optical head of Example 8.

22 is a side sectional view showing an optical head of Example 8. FIG.

FIG. 23 is a plan view showing an optical head of Example 8.

FIG. 24 is a side sectional view showing an optical head of Example 9.

FIG. 25 is a plan view showing an optical head of Example 9;

FIG. 26 is a side sectional view showing an optical head of Example 10.

FIG. 27 is a side sectional view showing an optical head of Example 10.

28 is a side sectional view showing the optical head of Example 10. FIG.

[Explanation of symbols]

1 Optical Head 2 Case 10 Light Emitting Element 15 Virtual Light Emitting Point 40 Mirror 50 Objective Lens 60 Optical Recording Medium 80 Package 120, 220, 320, 420, 520, 620, 7
20,820,920,1020,1120,1220
Optical member 130,230,1030 Hologram 530,830,930 Hologram element 622,822a, 822b, 822c Slope 740,940a, 940b Polarizing plate 170,270,570,870,970,1070,
1170, 1270 light receiving element 1175, 1275 second light receiving element 101f, 201f, 302f, 401f, 501f,
801f, 901f, 1001f, 1101f, 120
1f Forward light flux 101r, 201r, 302r, 401r, 501r,
801r, 901r, 1001r Return light flux

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI technical display location G11B 11/10 Z 9075-5D (72) Inventor Toshio Arimura 3-3 Yamato, Suwa City, Nagano Prefecture No. 5 within Seiko Epson Corporation

Claims (31)

[Claims] 1. An integral member for transmitting a divergent or convergent outward light flux and a backward light flux, wherein the optical path length of the outward light flux and the optical path length of the backward light flux are different from each other. And optical members. 2. The optical member according to claim 1, wherein the optical member is integrally molded and has a step on the surface. 3. The optical element according to claim 1, wherein the optical member is formed by laminating at least two separate components, and a step is formed on the surface in the state where the separate components are laminated. Element. 4. A method of manufacturing an optical member, characterized in that the optical member according to claim 1 is integrally injection-molded with a transparent resin to form a step on the surface. 5. A method of manufacturing an optical member, comprising press-molding the optical member according to claim 1 integrally with glass to form a step on the surface. 6. An optical path length of at least a binary refractive index is locally provided, and a forward light flux and a backward light flux pass through regions having different refractive indexes, and an optical path length of the forward light flux and an optical path length of the backward light flux are An optical member characterized by being configured differently. 7. The refracting power of a region through which the forward light flux and the backward light flux are transmitted through the integrated member, and the area where the forward light flux is transmitted,
An optical member characterized in that the refracting power of a region through which the backward light flux passes is different. 8. The optical member according to claim 7, wherein a locally convex or concave curved surface is formed on the surface. 9. The optical member according to claim 1, claim 6 or claim 7, a light receiving element disposed behind and substantially facing the optical member, and slightly higher or slightly higher than a light receiving surface of the light receiving element. A light emitting element which is arranged low, and a forward light flux which is emitted from the light emitting element and a backward light flux which is reflected by an optical recording medium and is directed to the light receiving element are configured to pass through the optical member. An optical head characterized by. 10. The optical head according to claim 9, wherein the optical head is configured to detect at least a focus error signal by detecting a change in the spot shape of the returning light flux on the light receiving element. 11. The optical head according to claim 9, wherein the optical member is made of a transparent resin and has a flange on its outer periphery, and a gate for injection molding is installed on the flange portion. 12. The optical member is formed of transparent resin,
The optical head according to claim 9, wherein alignment marks for alignment are formed or printed on the front surface or the back surface of the optical member and the front surface of the light receiving element. 13. The optical head according to claim 9, wherein a diffraction grating or a hologram is formed on the front surface or the back surface of the optical member. 14. The optical head according to claim 13, wherein the hologram is a blazed hologram that is blazed in a triangular tooth shape in units of pitches of diffraction grooves. 15. The optical member according to claim 1, claim 6 or claim 7, a light receiving element disposed behind and substantially facing the optical member, and slightly higher or slightly higher than a light receiving surface of the light receiving element. A light emitting element arranged low, and a package for holding the light receiving element and the light emitting element, wherein the light receiving element and the light emitting element are sealed by cooperation of the optical member and the package. Optical head. 16. The optical member and the package are
16. The optical head according to claim 15, wherein the optical members are fixed to each other via an adhesive material, and the adhesive material has a lower hardness after curing than the materials of the optical member and the package. 17. A first optical member and a second optical member bonded to the first optical member, wherein the first or second optical member is formed with a depression including an inclined surface, and Polarization formed by coating a multilayered thin film of a dielectric on a slope to provide a polarization separation function, filling the recess with a transparent resin or liquid, and bonding the first and second optical members together Separation element. 18. The refractive index of each of the first optical member, the second optical member, and the transparent resin or liquid filling the recess is substantially the same.
The polarized light separating element described. 19. The polarization beam splitting element according to claim 17, wherein the light flux incident on the slope is a convergent light flux or a divergent light flux having an NA (numerical aperture) equivalent to 0.15 or less in the medium. 20. The polarization splitting device according to claim 17, wherein the sloped surface and the recess are formed at a plurality of positions in an integrated optical member, and the plurality of sloped surfaces are coated with a common dielectric multilayer thin film. element. 21. The inclined surface according to claim 17, which is coated with a multilayered thin film of a dielectric material so as to have a polarization separation function, the recess is filled with a transparent resin, and the first and second optical members are bonded together. A method for manufacturing a polarization beam splitting element, characterized by performing an annealing treatment later. 22. A polarization separation element formed by fixing or holding a polarizing plate or a polarizing film on the surface or inside of an optical member. 23. A method of manufacturing a polarization beam splitting element, which comprises performing an annealing treatment after fixing or holding the polarizing plate or the polarizing film on the surface or inside of the optical member according to claim 22. 24. The polarization separating element according to claim 17 or 22, wherein the returning light flux transmitted through the polarization separating element is received by a light receiving element to detect a magneto-optical signal. Optical head to do. 25. The polarization beam splitting element according to claim 17, wherein the forward beam and the backward beam are transmitted to the first and second slopes having a polarization separating function, respectively, and are transmitted through the second slope of the polarization beam splitter. The received light flux is received by the light receiving element,
An optical head characterized by being configured to detect a magneto-optical signal. 26. The polarization plane of the outgoing light flux is set to coincide with the polarization transmission direction of the first inclined surface, and the polarization separation direction of the second oblique surface is rotated by about 45 degrees with respect to the polarization plane of the return optical flux. 26. The optical head according to claim 25, wherein: 27. An optical member, which is divided into a mirror-finished region and a diffused reflection region having fine irregularities, is used, and the outward light flux and the backward light flux are transmitted to the mirror-finished region. Optical head. 28. An optical member, which is divided into a region having an antireflection coating deposited thereon and a non-coating region having no antireflection coating deposited thereon, is provided with a central portion of a divergent light beam emitted from a light emitting device in the antireflection coating region. An optical head comprising: a second light receiving element for light emission power detection which transmits the light, reflects a part of the divergent light flux in the non-coating area, and receives the reflected light. 29. A second light-receiving element for detecting the emission power, and a first light-receiving element for receiving a return light beam which is a reflected light of an optical recording medium, and the first and second light-receiving elements. 29. The optical head according to claim 28, wherein the optical head is formed on an integrated substrate. 30. A light-emission power detecting device, comprising: an optical member having a reflecting surface formed in a region where a forward light flux and a backward light flux are not transmitted, wherein the reflecting surface reflects a part of the forward light flux and receives the reflected light. An optical head comprising a second light receiving element. 31. The reflection surface is an inclined surface or a curved surface,
31. The optical head according to claim 30, wherein the surface reflection light flux or the total reflection light flux of the inclined surface or the curved surface is received by the second light receiving element.