JPS63119024A - Optical head device - Google Patents

Abstract

PURPOSE:To obtain the titled device small, light, less in the number of parts and low-cost by constituting an optical splitter of a parallel flat plate optical member provided with a reflecting surface having an optical demultiplexing characteristic on a first surface or a second surface, and providing the pupil surface dividing means of a reflecting light flux on the second surface. CONSTITUTION:On the first surface of an optical member 11, a half mirror 12 formed by evaporation is provided, two prisms 13 and 14 are provided on the second surface and a reflecting mirror 15 is provided on the joining surface of the prisms 13 and 14. The light flux discharged from a laser light source 10 is made incident on a half mirror 12. When information is detected, the light of non-modulation is irradiated to an information recording surface 6, the reflecting light to receive the modulation in accordance with the information recorded there is photodetected by photodetecting surfaces 16a, 16b and 17a of light detecting devices 16 and 17, and detected by obtaining the sum of outputs Ia and Ib from the light detecting device 16 and an output Ic of the light detecting device 17. Thus, autofocusing and autotracking can be executed by a small number of parts.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical head device that records or detects information by irradiating the information recording surface of an information carrier with light, and particularly relates to an optical head device that is small, lightweight, and inexpensive to manufacture. The present invention relates to an optical head device.

(Prior Art) Conventionally, an optical head device has been configured as shown in FIG. 14, for example. FIG. 14 is a schematic configuration diagram thereof. As shown in the figure, a diverging light beam emitted from a semiconductor laser light source 1 is divided by a diffraction grating 2 into a main beam for signal readout and two sub beams for tracking error signal detection. This divided light flux passes through the beam splitter 3 and is focused by the objective lens 4 to form a spot with a diameter of about 14 m on the information recording surface 6 provided on the optically transparent substrate 5. The light beam reflected by the recording surface 6 passes through the objective lens 4, is condensed, is reflected by the beam splitter 3, passes through the sensor lens 7, the cylindrical lens 8, and reaches the photodetector 9.

When recording information using the optical head device configured in this way, the laser light source l is driven in accordance with the information signal to modulate the light incident on the information recording surface 6, and the information is also detected. In this case, unmodulated light is irradiated onto the information recording surface 6 on which information is recorded by uneven pits or changes in reflectance, and the reflected light modulated by the recorded information is detected by a photodetector 9. Play information.

At this time, on the information recording surface 6, a track consisting of a recording signal train or a guide track provided in advance on the substrate 5, etc.
In FIG. 14, they are densely formed and extend in a direction perpendicular to the plane of the paper. In order to record or detect information correctly, it is necessary to perform auto-tracking in which the spot always correctly traces the track. In addition to the above-mentioned auto-tracking, in optical head devices, in order to record information at high density on the information recording surface and to detect high-density recording, light from a light source is constantly directed onto the information recording surface. It is necessary to perform autofocusing to focus.

In the optical head shown in FIG. 14 described above.

Auto-tracking is performed using a well-known 3-beam system, and auto-focusing is performed using a well-known astigmatism method.

However, in order to perform auto-tracking using the 3-beam system, out of a total of three beams divided into a main beam and two sub-beams by the above-mentioned diffraction grating 2, each of the two sub-beams must be placed on the information recording surface. The light is irradiated slightly shifted from the center of the track, and the reflected light is received by a photodetector 9 divided into three parts. At this time, if tracking is done correctly, 2
The amounts of returned light from the two sub-beams are equal and in equilibrium, but if they shift to one side, a difference occurs in the amounts of returned light. The difference in the amount of returned light is detected by the photodetector 9 as a tracking error signal. The optical head is controlled to be driven horizontally with respect to the information recording surface 6 so as to eliminate the error signal thus obtained.

Further, in order to perform autofocusing using the astigmatism method, the cylindrical lens 8 is provided in the reflected light beam as described above. The light beam passing through the cylindrical lens 8, especially the diffraction grating 2,
The main beam of the divided beams is received by the photodetector 9 as a perfect circle when it is focused, and as an elliptical spot when it is out of focus. The photodetector 9 is divided into three parts as described above, and among them, the central sensor is divided into four parts symmetrically in the horizontal and vertical directions. Therefore, a focusing error signal is detected by detecting a change in the spot shape due to the vertical movement of the information recording surface 6 as a change in light amount using the four-part sensor. The optical head is controlled to be driven vertically with respect to the information recording surface so as to eliminate the error signal thus obtained.

[Problems to be Solved by the Invention] Incidentally, it is desirable that the optical head device be small, lightweight, and inexpensive.However, as mentioned above, for example, it is possible to perform auto-tracking using a 3-beam system, or use an astigmatism method. To perform autofocusing, a diffraction grating,
Alternatively, a cylindrical lens shell is required, which poses an obstacle to reducing the size, weight, and cost of the optical head device. or,
When performing auto-tracking using a 3-beam system using a diffraction grating, a high-output laser light source is required, and i
A adjustment is also troublesome.

The present invention has been made to solve these problems, and an object of the present invention is to provide an optical head device that is small and lightweight, has a small number of parts, and can realize cost reduction.

[Means for Solving the Problems] The problem with the prior art is that the information recording surface is irradiated with light emitted from a light source, and a light splitter disposed in the optical path from the light source to the information recording surface is used to In an optical head device that detects or records information by guiding a reflected light beam from an information recording surface to a light receiving surface of a photodetector, the light splitter has light splitting characteristics on the first or second surface of the splitting base. This problem can be solved by comprising a parallel plate optical member having a reflective surface, and providing a pupil plane dividing means for the reflected light beam on the second surface of the optical member.

[Function] In the optical head device configured as described above, the light beam emitted from the light source is incident on the parallel plate optical member. Since this optical member has a reflective surface with light splitting characteristics, a part of the light beam incident on the optical member is reflected, and while being focused, the light beam enters the recording surface of the information recording carrier, and is then reflected by the recording surface. The light beam enters the optical member again, passes through the optical member, and is further divided into two light beams by a pupil plane dividing means provided on the second surface of the optical member. These light beams are then received by a photodetector, and predetermined recording information, focusing error detection, and tracking error detection are performed.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic block diagram of an optical head device based on the present invention. In FIG. Two prisms 13.1 are provided on the first surface.
4 is provided, and a reflecting mirror 15 is provided on the joint surface of the prisms 13 and 14. The light beam emitted from the laser light source 10 enters the half mirror 12. Part of this incident light is reflected, and part of it is transmitted as is.

The reflected light beam is focused by the objective lens 4 and forms a spot with a diameter of about IJLm on the information recording surface 6 via the substrate 5. The light beam reflected by the information recording surface 6 passes through the objective lens 4 again and enters the half mirror 12. Of this incident light, the semicircular bundle 19 that has passed through the prism 14 is
The light enters the light receiving surface 17a of the detector 17. On the other hand, the semicircular bundle 18 that has passed through the prism 13 is reflected by the reflecting mirror 15,
The light enters the light receiving surfaces 16a and 16b of the photodetector 16, which is divided into two.

When recording information, the laser light source IO is driven according to the information signal to modulate the light incident on the information recording surface 6, and when detecting information, unmodulated light is used. The reflected light that is irradiated onto the information recording surface 6 and modulated according to the information recorded thereon is sent to the photodetector 16.
．． The light is received by the light-receiving surfaces 16a, 16b, and 17a of the photodetector 17, and is detected by adding the outputs Ia and lb from the photodetector 16 and the output Ic from the photodetector 17.

Next, the principle of autofocusing in the optical head device configured as described above will be explained.

In FIG. 1, the reflected light beam reflected by the information recording surface 6 enters a half mirror 12. A part of this incident light flux passes through the prism 13 via the optical member 11, and passes through the reflecting mirror 15.
It is reflected by the photodetector 16 and enters the light receiving surface 16a.
, 16b are formed with semicircular spots. Now, when the information recording surface 6 is at the in-focus position, the light receiving surfaces 16a and 1
The photodetector 16 is provided at a position such that the amount of light received by the photodetector 6b is uniform, as shown in FIG. 2(B). In addition, in FIG. 2, the semicircular shaded area indicates the shape of the spot formed on the light receiving surfaces 16a, 16b as described above. Thus, when the information recording surface 6 is located at a relatively far position with respect to the objective lens 4, the semicircular bundle 18 moves upward in FIG. That is, the spot of the semicircular bundle 18 is formed in a state biased toward the light receiving surface 16b, as shown in FIG. 2(a). Therefore, the amount of light detected by the photodetector 16 is greater on the light receiving surface 16b than on the light receiving surface lea. On the other hand, when the information recording surface 6 is located relatively close to the objective lens 4, the semicircular bundle 18 moves downward in FIG. That is, as shown in FIG. 2(c), the spot of the single beam 18 is formed in a state biased toward the light receiving surface 16a. Therefore, the amount of light detected by the photodetector 16 is greater on the light receiving surface 16a than on the light receiving surface 16b.

Now, assuming that the output 1a from the light-receiving surface 18a and the output Ib from the light-receiving surface 16b are used, in an electrical system as shown in FIG. , a focus error signal as shown in FIG. 3(B) is obtained at the output terminal 21. In FIG. 3(B), the horizontal axis shows the distance (focus error) between the objective lens 4 and the information recording armor part 6 when the in-focus position is zero, and the vertical axis shows the signal output. According to the focus error signal,
By moving the objective lens 4 or the entire optical head relative to the disk along the optical axis of the incident light via an actuator (not shown), automatic 7-occursing becomes possible.

Next, the principle of auto-tracking in the optical head device of the first embodiment will be explained.

The tracking error signal is detected by photodetectors 16 and 17 using the single beam 1B and the single beam 19. Figure 4 (A),
As shown in (B) and (C), there are grooves 6 in 5 of the substrate of the information recording R carrier.
If a groove 6a is formed, the incident light beam is focused by the objective lens 4 in the vicinity of this groove 6a. Here, (B) shows a state where a spot is generated on the target groove 6a, (^
), , (C) show a state in which the spot is shifted to the right or left with respect to the groove, respectively.The light beam reflected by the recording surface 6 on this substrate 5 contains tracking information due to diffraction or scattering at the groove 6a. include.

The light receiving surface lea, 1 of the photodetector 16.17 shown in FIG.
When the reflected light is received by 6b and 17a, the aforesaid light will be reflected in the 5th [(A), (B), and It changes as shown in (C). Therefore, in an electrical system as shown in Figure 6 (^),
By performing the calculation Ia+Ib)-Ic in the differential amplifier 23, a tracking error signal as shown in FIG. 6(B) is obtained at the output terminal 24. In addition, Fig. 6 (B
), the horizontal axis shows the tracking error and the vertical axis shows the signal output. According to the obtained tracking error signal, a tracking actuator (not shown) is driven to move the objective lens 4 perpendicular to the optical axis. auto-tracking is possible.

In the optical head device of the first embodiment described above, the photodetector 317 is provided near the condensing position of the single beam 19, but if the area of the light receiving surface 17a of the photodetector 17 is increased, the photodetector 317 can be The container 17 can be provided near the prism 14. By doing so, the optical head device in this embodiment can be further miniaturized. Moreover, parallel plate optical member 1
When the half mirror 12 is deposited on the first surface of the optical member 11 and the prisms 13 and 14 are bonded to the second surface using a suitable adhesive, high surface precision is required for the half mirror 12 on the first surface of the optical member 11. If the adhesive used has the same refractive index as the optical member 11 and the prism 13, 14, the second surface of the optical member 11 or the prism 1
The accuracy of bonding 3 and 14 does not need to be very high. Note that the parallel plate optical member 11 can be easily processed into a large area with high precision, and can be produced in large quantities by cutting it into small pieces, so that it can be produced at a lower cost than a prism.

Furthermore, in the optical head device of this embodiment, since the photodetectors 16 and 17 are provided at completely different positions, each detector can be adjusted to the optimum position independently, and autofocusing and Auto tracking accuracy is improved.

Next, a second embodiment of the present invention will be described.

FIG. 7(a) is a schematic configuration diagram of an optical head device according to a second embodiment of the present invention.

The optical head device of the second embodiment shown in the figure is constructed by attaching only the prism 13 to the second surface of the parallel plate optical member 11 in the optical head device of the first embodiment, and one reflection is $115. It is stuck to the prism 13 as it is.

Furthermore, a photodetector 28 is provided directly below the prism 13. Note that the photodetector 2B may be provided so as to be in contact with the prism 13 as shown in FIG. 7(A).The other configurations are the same as in the optical head device of the first embodiment.

In the optical head device of this embodiment configured as described above, autofocusing can be performed using the same principle as that in the first embodiment. Further, auto-tracking is performed by detecting a tracking error signal with a photodetector 28 using a single beam 19. Tatashi,
The light receiving surface of the photodetector 28 is divided into two parts 28a and 28b, as shown in FIG. 7(B), and the direction of this division coincides with the track direction of the information recording surface 6. As shown in FIGS. 4A, 4B, and 4C, when the relative positional relationship between the spot and the track groove 6a changes on the information recording surface 6, the light on the photodetector 28 changes accordingly. The light intensity distribution changes as shown in FIG. In FIG. 8, the vertical axis indicates the amount of light of the single beam 19 received by the light receiving surfaces 28a and 28b of the photodetector 28, and the left side of the vertical axis represents the amount of light received at the light receiving surface 28a, and the right side represents the amount of light received by the light receiving surface 28a. Based on these light intensity changes, FIG. 7(C) shows the amount of light received at the surface 28b.
In an electrical system as shown in FIG. 6, by performing the calculation l5-Id in the differential amplifier 31, a tracking error signal as shown in FIG. 6CB) is obtained at the output terminal 32.

Auto-tracking is possible by driving an actuator (not shown) in accordance with this tracking signal and moving the objective lens 4 perpendicularly to the optical axis.

Furthermore, a third embodiment of the present invention will be described. !
@9 Figure is a schematic configuration diagram of an optical head device in a second embodiment of the present invention.

In the figure, 33 is a prism attached to the second surface of the parallel plate optical member 11. This prism 33 is arranged such that the optical axis of the reflected light beam from an information recording carrier (not shown) is located at the prism 33.
The other configuration of this embodiment is the same as that of the optical head device of the first embodiment.

In the optical head device of this embodiment configured as described above, the light beam reflected by the information recording surface (not shown) passes through the parallel plate optical member 11 and the prism 33, and then is divided into two single light beams 36 and 37. The light is split and focused onto a photodetector 35. Here, the photodetector 35 includes 35a, 35b, 35c, 3
5d, and the single beam 36 is sent to the photodetector 35.
c and 35d, and the single beam 37 is transmitted to the photodetector 3.
5a and 35d. However, the signal recorded on the information recording carrier is detected by light! 35
Outputs If, Ig, rh of a, 35b, 35c, 35d,
It is obtained by the sum of Ii.

Next, the autofocusing and autotracking methods used in the optical head device of this embodiment will be explained.

In FIG. 9, the light intensity distribution on the photodetector 35 changes as shown in FIGS. do. Here, (A) shows the spot situation due to the reflected light beam when the incident light beam is in focus on the information recording surface, and (B) and (C) show the spot situation when it is out of focus. In each figure, the shaded area indicates the position where the spot was formed. Therefore, the outputs If, Ig, Ih, and Ii from the photodetector 35 can be used in an electrical system as shown in FIG. 9(B). By performing the calculation (If-Ig)+(Ih-Ii) using the differential amplifiers 38, 39 and the adder 40, a focus error signal as shown in FIG. 3(B) is obtained at the output terminal 41. Autofocusing is performed by driving an actuator (not shown) according to the focus error signal thus obtained. Regarding auto-tracking, a tracking error signal is obtained at the output terminal 45 by performing the same calculation as described above using the differential amplifiers 42, 43 and the adder 44 in an electrical system as shown in FIG. 9(C). Auto-tracking is performed using the tracking error signal thus obtained.

Above, the 3″X embodiment according to the present invention has been explained.
Since each surface of the prism 33 used in this embodiment acts as a transmitting surface, even members with relatively low surface precision can be used. Further, even if the vertex 34 of the prism 33 has an extremely small angle, for example, less than 1°, it is applicable to this embodiment. Therefore, the prism 33 may be made of a transparent plastic molded member, or an ultraviolet curable resin may be poured onto the mold, and the ultraviolet rays may be irradiated by pressing the prism 33 against the parallel plate optical member 11 made of a glass plate. Tokoro gff
It may also be created using the ZP method.

Furthermore, the photodetector 35 of the photodetector 35 in this embodiment
Since elements a, 35b, 35c, and 35d can be formed on the same element, this is useful for reducing the cost of the optical head device.

Note that in the optical head device of this embodiment, the prism 33
Since it is necessary to take a relatively long optical path length from the photodetector 35 to the photodetector 35, the optical head device becomes somewhat larger, but this can be solved by arranging a bending mirror (not shown) in the optical path.

Furthermore, a fourth embodiment of the present invention will be described.

FIG. 11(A) shows an optical head according to a fourth embodiment of the present invention. This is a schematic configuration diagram of the tl, and FIG. 11(B) is the 11th
FIG. 2 is a schematic view of the optical head device from the prism side shown in FIG.

In these figures, 46.47 is either one vertex angle or 9
It is a triangular prism formed with an angle of 0'', and the apex angle of 90'' is disposed on the far side with respect to the optical member 11 in the prism 46 and in contact with the optical member 11 in the prism 47. There is. The prisms 46 and 47 are arranged so that the optical axis of the reflected light beam from an information recording carrier (not shown) passes through the apex 48. Follow me,
The reflected light beam from the information recording carrier is divided into semicircular beams 52 and 51 that pass through prism 46 and prism 47, and enter photodetectors 49 and 50. The photodetectors 49 and 50 are each divided into two parts 49a and 49b, and 50a and sob. In an optical head device having such a configuration,
Focusing error detection is performed by photodetectors 50a and 50b using a semi-circular bundle 52.The detection principle is approximately the same as that in the first embodiment, and the detection of focusing errors is performed by photodetectors 50a and 50b according to the amount of focusing deviation. The light intensity distribution above is shown in Figure 2 (A).
, CB) and (C). Based on these changes in light intensity, the differential amplifier 53 calculates the difference between the output current 1j of 50a and the output current fk of 50b, as shown in FIG. 11(C). By taking the signal, a cross-cutting error signal is obtained at the output terminal 54. Further, in the error optical head gtR, tracking error detection is performed by the photodetectors 49a and 49b using the semicircular bundle 51.Since the edge of the prism 46 is oriented in the same direction as the track direction of the information recording carrier, As the spot moves on the information recording carrier as shown in Figures (A), CB), ((:), the light intensity distribution on the photodetector 49 changes accordingly as shown in Figure 8(A),
It changes as shown in (B) and (C). Therefore, based on these changes in the amount of light, in the electrical system shown in FIG. 11(D), the differential amplifier 55 performs the calculation ``I-Im'', and the output terminal 56 performs tracking as shown in FIG. 6(B). An error signal is obtained.

Furthermore, a fifth embodiment of the present invention will be described. FIGS. 12(^) and (8) are schematic configuration diagrams of an optical head device according to a fifth embodiment of the present invention.

In the figure, the second surface of the parallel plate optical member 11 includes a prism 57a with a reflecting mirror formed on one surface.

57b is provided. This prism 57a.

57b, as shown in FIG. 12(B), is provided so that its reflecting surface is inclined in opposite directions to the second surface of the optical member 11, and the reflecting light beam from the information recording carrier is The optical axis of the prism 60 is arranged so as to pass through the boundary surface between the prisms 57a and 57b after entering the optical member 11. Therefore, the reflected light beam 59 is reflected by the prisms 57a and 57b.
The semi-round bundles 60a and 60b are divided into half-round bundles 60a and 60b, and reflected by the reflecting mirrors of the prisms 57a and 57b, respectively.Then, each half-round bundle 60a and 60b is totally reflected by the first surface of the optical member 11, and Photodetector 5 provided on the end face
Entered at 8.59. The photodetectors 58 and 59 are each 5
The photodetector 58.5'l is divided into two parts, 8a and 58b, and 59a and 59b, and the detection of the information recorded on the information recording carrier, the focusing error detection, and the tracking error detection are carried out in the fourth embodiment. It is carried out in the same direction as.

In this embodiment, the photodetectors 58 and 59 are the optical members 1
The prism 57a is provided on the end face of the prism 57a.

Since the light beam incident on 57b has an optical path within the optical member 11, the optical head device can be significantly downsized. Moreover, a holding mechanism for the photodetectors 58 and 59 is unnecessary.

Furthermore, a sixth embodiment according to the present invention will be described. FIG. 13 is a schematic diagram of an optical head device according to a sixth embodiment of the present invention.

In the same figure, the diverging light emitted from the laser light source 10 is made into a parallel beam by the collimator lens 61, and the crystal plate 6
2. This crystal plate 62 is provided in a diagonal direction with respect to the optical axis of the above-mentioned traveling light beam, and its first surface is coated with an antireflection coating, and its second surface is provided with a reflective layer 1j163 having polarization characteristics. . Therefore, when S-polarized light whose vibration direction is perpendicular to the plane of the drawing is incident on the crystal plate 62, the incident light flux will not change its polarization state,
The light enters the reflective film 63 and is almost completely reflected.

The reflected light beam passes through the crystal plate 62 again and passes through the objective lens 4.
incident on . At this time, since the traveling direction of the light beam and the optical axis of the crystal plate 62 form an appropriate angle, the crystal plate 62
can be set to a thickness such that it acts as a quarter-wave plate.Next, the light beam reflected by the recording surface 6 of the information recording carrier becomes circularly polarized light in the opposite direction to that at the time of incidence.
The light is incident on the crystal plate 62. The crystal plate 6
2 again acts as a quarter-wave plate, so now P
After being polarized and incident on the reflective film 63 having polarization characteristics, the light is transmitted as is. This transmitted light flux is condensed by aspheric lenses 64 and 65 formed on the father-reflective film 63 and enters the photodetector 35. Then, recording information detection, focusing error detection, and tracking error detection are performed in the same manner as described above.

In this embodiment, when the aspherical lenses 64 and 65 are made of ultraviolet curing resin, it is easy to form a resin layer 66 around the reflection l1163. Functions as a protective layer.

In this embodiment, as is clear from the above description, it is possible to make the crystal plate 62 function as a quarter-wave plate and to construct an optical head device with good light utilization efficiency with a very small number of parts. can.

Further, since the aspherical lenses 64 and 65 can be manufactured using a relief copying method, after forming a plurality of lenses on a parallel plate to be used as the optical member 62,
A highly mass-producible manufacturing method in which the material is cut into predetermined dimensions becomes possible.

In this embodiment, the combination of the crystal plate 62 and the reflective film 63 can be replaced by a combination of a glass plate and a half mirror.

(Effect of the invention) As explained above, according to the uninvented optical head device,
Auto-flashing and auto-tracking can be performed with a smaller number of parts than in the past, making it possible to obtain a smaller and lighter optical head device at a lower cost.

In addition, in order to split the reflected light beam from the conventional information recording carrier,
Previously, this was done using a boundary line provided in the photodetector, but since the optical head device of the present invention can do it with a small number of optical elements, it is possible to achieve high-precision pupil division without having to set the optical elements so precisely. becomes possible.

[Brief Description of the Drawings] Section 1 is a schematic configuration diagram of an optical head device according to a first embodiment of the present invention, and FIGS. 2 and 3 are for explaining detection of a focusing error signal in the first embodiment. This is a diagram of
Figures 2 (A), (B), and (C) are diagrams showing the situation of the spout of the light beam irradiated onto the light detection base, and Figure 3 (A).
) is a diagram showing an electrical system, FIG. 3(B) is a diagram showing a focusing error signal, FIGS. 4 to 6 are diagrams for explaining detection of a tracking error signal in the first embodiment, and FIG. Figures 4 (A), (B), and (C) are diagrams showing the on-track status of the light beam irradiated from the objective lens onto the information recording carrier, and Figures 5 (A), (B), and ((:
) is a light intensity distribution diagram, Figure 6 (A) is a diagram showing the electrical system, Figure 6
FIG. 7(B) is a diagram showing a tracking error signal, FIGS. 7 and 8 are diagrams for explaining a second embodiment of the present invention, and FIG. 7(A) is a diagram showing a tracking error signal. A schematic configuration diagram of the head device, FIG. 7 (CB) is a perspective view of the prism used in the second embodiment, FIG. 7 (C) is a diagram showing the electrical system, FIG. 8 is a light intensity distribution diagram, and FIG. FIG. 10 is a diagram showing a third embodiment of the present invention, and FIG. 9(A) is a schematic diagram of the optical head device of the third embodiment, FIG. 9(B), (C
) is a diagram showing the electrical system, FIG. 10 is a diagram showing the state of the spot of the light beam irradiated on the photodetector, and FIG. 11 is a diagram for explaining the fourth embodiment of the present invention. Diagram (A
) is a schematic configuration diagram of the optical head device of the fourth embodiment;
Figure (B) is an explanatory diagram of the prism used in the optical head device,
11(C) and (D) are diagrams showing the electrical system, FIG. 12(^) is a schematic configuration diagram of the optical head ml of the fifth embodiment according to the present invention, and FIG. 12(B) is a diagram showing the optical A perspective view of a combination of a parallel Y-plate optical member and a prism used in a head device, FIG. 13 is an am configuration diagram of an optical head device according to a sixth embodiment of the present invention, and FIG. 14 is a schematic configuration of a conventional optical head device. It is a diagram. 4...Objective lens, IO...Laser light source, 11...
・Parallel plate optical member, 13, 14, 33.4B. 47, 57 a, 57 b --- prism, 6i
--Collimator lens, 62--Crystal plate, 63--
・Reflective film, 64.65-... Aspherical lens agent Patent attorney Minoru Yamashita Child figure 1 (A) (8) (
C) Figure 3 (A) Figure 4 (A) (8) (C)
Fig. 5 (A) (B) (C) Fig. 6 Fig. 7 +j (C) Fig. 8 Fig. Ω (A) (B) (
C) 0 days
- Law - Figure 11 (C-n

Claims (6)

[Claims] (1) Light emitted from a light source is irradiated onto the information recording surface, and a beam splitter disposed in the optical path from the light source to the information recording surface directs the reflected light beam from the information recording surface to the light receiving surface of the photodetector. In an optical head device that detects or records information guided by light, the light splitter is constituted by a parallel plate optical member having a reflective surface having light splitting characteristics on a first surface or a second surface of the splitter, An optical head device characterized in that a second surface of the member is provided with pupil plane dividing means for the reflected light beam. (2) The optical head device according to claim 1, wherein the light splitting means is constituted by two or more reflecting surfaces or transmitting surfaces having mutually different inclination angles. (3) The optical head device according to claim 2, wherein the light splitting means is constructed by bonding one or more prisms to the second surface of the parallel plate optical member. (4) The optical head device according to claim 3, wherein the pupil plane dividing means of the prism is provided to divide the reflected light beam from the information recording surface into two equal parts. (5) The optical head device according to claim 1, wherein the first surface of the parallel plate optical member has a half mirror or a polarizing beam splitter characteristic. (6) In the case where the light splitting means is constructed by bonding one or more prisms, the bonding surface has a reflecting mirror or a means having polarizing beam splitter characteristics. The optical head device described in Section 1.