JPH0258738A - Optical pickup head device and optical information device using the same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical pickup head device capable of recording, reproducing, or erasing optical information stored on a source medium or a magneto-optical medium such as an optical disk or an optical card; The present invention relates to an optical information device using a pickup head device.

Conventional Technology Optical memory technology that uses pit-like patterns as a high-density, large-capacity storage medium has been put into practical use with its applications expanding to include digital audio discs, video discs, document file discs, and even data files. There is. The mechanism by which information is recorded and recorded successfully with high reliability through a light beam focused on the micron order is entirely due to the optical system. The basic functions of the optical pickup head device (hereinafter referred to as GPU) are: (■) Light condensing ability to form a minute spot at the folding limit; (■) Focus control of the optical system and pit signal detection; and (I) tracking control. These are realized by combining various optical systems and photoelectric conversion detection methods depending on the purpose and use. FIG. 10 is a schematic diagram showing an example of a conventional OPU. Usually, TE91! The diverging wavefront (electric field: horizontally polarized wave) from the semiconductor laser light source 1 that oscillates in the mode is converted into a parallel beam by the collimating lens 2, and the polarizing beam splitter 107
Then, the light is selectively reflected onto a quarter-wave plate (1/4λ plate) 18 on the left. The circularly polarized wavefront that has passed through the 1/4 λ plate 18 is narrowed down to a spot of about 1 μm by the lens 3, reaches the medium surface 4'' of the optical storage 1, and irradiates the pit-like pattern 40. The light beam reflected and diffracted by the medium surface travels backward through the lens 3 again and passes through the 1/4λ plate 18, where it becomes a parallel beam of waves on the vertical side, passes through the polarizing beam splitter 107, and is split into two by the beam splitter 19. divided into directions. One reflected light passes through a condensing lens 201 and a cylindrical lens 21 that imparts astigmatism to a four-part photodetector 5.
59 and is converted into a focus error (hereinafter abbreviated as FE) signal. The other transmitted light enters a two-part photodetector 22 for detecting a tracking error (hereinafter abbreviated as TE) signal, with the far field pattern intact.

Here, the 1/4λ plate 18 is the polarizing beam splitter 10
By combining with 7, you can increase the efficiency of light usage and at the same time suppress the light returning to the semiconductor laser.
This is a device to prevent unnecessary noise from increasing in the signal light component. However, OPUs for read-only discs have some leeway in the light intensity design, and it is possible to omit the 1/4λ plate and polarizing beam splitter.In particular, in order to reduce the size and price, it is possible to omit parts and combine It is planned to become

Problems to be Solved by the Invention However, even in a raw-only OPU, it is necessary to construct a beam splitting means, a focal side control means using astigmatism or the Naifetsu method, and a tranokink control means independently or in combination. . For this purpose, the optical components conventionally used, such as beam splitters, lenses, and prisms, are not easy to manufacture, assemble, or adjust in large quantities. There was a problem.

The common reasons why these problems occur are that first, optical components that require highly accurate flat or aspherical surfaces require many processes to achieve the desired addition; Second, in order to combine a large number of parts to achieve a given overall performance, it takes a lot of time and complicated inspection and measurement equipment to adjust the assembly number; and third, the number of parts is difficult to assemble. Since there are limits to the miniaturization of the optical system, there were also major constraints on the miniaturization of the entire optical system.

” - As a solution to the problem described above, there is a technology in which predetermined wavefronts for focus and tracking control are recorded on a single hologram element, and each wavefront reproduced by the reading beam of an optical pickup head device is guided to a photodetector. recently disclosed. 1)～5)1) Tokikai Sho・62-3□36
No. 59, Okata" 2, water valve 2) Tokikai Akira, e2-t, 8
．． No. 8032, ``Okata'' 2, Mizuben 3) Tokikai Akira [12
-23 [i.1.45, Matsushita, Tatsumi 4) Y, K
imura et al, “old gh Perf, or,
mance 0ptical head using
Optimized Holographbic Opt
icalElement”, Prompting Off
Proc. of International Symposium on Optical Memory
national Sy, mposium on 0p
tical Memory), Tokyo, 5ept,
IG-18, 1987 (p, 131) 5) K, Tatsumi et al, “A Mul
ti-functional Reflection
Type Grating Lens for the
CD 0ptica1) lead”, Promoting International Symposium
On optical memory (Proc, of tbe
International Symposium
on 0ptical Memory), Tokyo,
5ept, IG-18, 1987 (p, 127) Of the above, is 4) an FE double signal double knife? −
1, this is a method of detection based on the intensity of diffracted light from a slit grating provided on the TE multiplied signal far field (hologram element surface), and in all other cases, the astigmatism wavefront 140, 141° 142 as shown in FIG. is calculated from the signal received by the four-part photodetector 555 to obtain the FE multiplied signal T.
This is to detect an E-fold signal. For example, the I''E signal is obtained by adding the outputs of each detector of a quadrant detector.
, 32, the differential circuit 33 takes the difference, and the signal processing circuit 34 performs signal processing.

However, a serious problem with each method is that when the wavelength of the light source deviates by δλ from the design standard wavelength λ, each beam of
401, etc.), and as a result, the component of the FE multiplied signal tracking signal is mixed.

It becomes difficult to perform accurate focus control due to occurrence of FE multiplied signal offset.

For normal semiconductor lasers, the usage environment is 6 degrees, for example.
When the driving current changes by 0'C, the laser oscillation wavelength changes by about 12 nm, and when the drive current changes by 40 mA, the wavelength changes by about 8 nm. There remains the problem of stable error signal detection that can cope with changes in the diffraction angle from the hologram element that occur due to such wavelength fluctuations.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention divides the hologram surface of a hologram element into at least two parts spatially f, and each hologram surface has one diverging or converging surface. A hologram element that records a wavefront, and a fum, l-detector that receives at least the 1st diffracted light other than the 0th order diffracted light from the hologram element are formed into a band shape, and furthermore, the region dividing line of the photodetector is formed to correspond to the 0th order diffracted light from the hologram element. A focus error (F'E) signal is detected using a photodetector that extends approximately parallel to the radial direction with the convergence point as the center, and a different diffraction grating or diffraction A tracking error (TE) signal is detected by a hologram element in which a grating and a non-bologram region are formed.

In the present invention, even if the diffraction angle of the diffracted light from the hologram element changes due to wavelength fluctuations in the light source, a constant amount of diffracted light is always incident on each photodetector, and extremely stable It becomes possible to detect the FE multiplied signal and the TE multiplied signal.

Further, by forming at least two types of regions independently in the hologram element, diffracted light due to beats of the hologram pattern is not generated and is not influenced by them, so that the FE multiplied signal can be stably detected.

Furthermore, an optical information device configured using this optical pickup head device is highly reliable because it is capable of stable focus servo and tracking servo, and can be easily used on the side of the optical pickup. Since the optical information device is simplified, it becomes an inexpensive and compact optical information device.

Embodiment FIG. 1(a) shows the outline, grooves, and structure of an OPU device according to an embodiment of the present invention. In the figure, 1 is a semiconductor laser that emits a coherent beam (for example, a wavelength of λ2800).
TE9i in nm! The beam emitted from the light source 1 is A collimating lens 2 converts the beam into a parallel beam, and a lens 3 focuses the beam onto a disk 4. Reference numeral 6 denotes a hologram element capable of reproducing a wavefront having two pairs of conjugate focal points, which is obtained by recording two 1 or convergent wavefronts on the hologram element. The hologram element 6 is interposed between the lenses 2 and 3, and its O
Next time, the tip of the tongue will be focused on the disk 4. In the disk 4, 42 is a substrate, and 41 is a protective film. The beam reflected by the disk 4-1- returns to the O lens 3.
The diffracted beams 71, 73 and 0 have two pairs of conjugate focal points off-axis to obtain an FE multiplied signal, in addition to the 0th-order tongue tip.・72
and 74 are generated. These diffracted lights 71 to 74 are converged via the collimating lens 2. When the diffracted lights 71 to 74 are properly focused on the disk 4'-, they are perpendicular to the optical axis of the lens 2, including the convergence point (light emitting point 10 of light #, 1) at the end of the O-th fourth fold. The focal plane 111 is focused in a direction orthogonal to two planes at front and back positions, and the distance between each focal plane and the plane 111 is designed to be δ, = δ2:δ.

The diffracted lights 71 to 74 are received by the photodetector unit 5. FIG. 1(b) shows the state of the first diffracted lights 71 and 72 on the surface of the photodetector unit disposed at the photodetector unit 111. FIG. The photodetector unit 5 is horizontally composed of photodetectors 51 and 52, and the photodetector 51 is further composed of photodetectors 511, 512 and 5.
13. The photodetector 52 is a photodetector 52
1,522 and 523. This figure shows a reproduced image corresponding to a state in which the focus is correctly set on the disk. FE double signal TE double signal RF
Details of the double signal detection method and the hologram element 6 will be described later.

FIG. 2 is a conceptual diagram showing another embodiment of the present invention. 1st
In the embodiment, a transmission type hologram element is used, whereas in this embodiment, a reflection type hologram element 660 is used to bend the optical axis at α 90°. Furthermore, the imaging optical system is configured with 30 objective lens systems without using a collimating lens, thereby achieving miniaturization and reducing the number of parts.

FIG. 3 illustrates yet another embodiment of the invention. Figure (a) shows a schematic diagram of the OPU device. The beam emitted from the light source 1 is made into a parallel beam by the collimating lens 2, reflected by the polarizing beam splitter 106, becomes circularly polarized by the wave plate 9, bends the optical path by the mirror 8, and then is sent to the disk by the lens 3. The light is focused on 4. The beam reflected by the disk 4'2 passes through the lens 3 again on its return trip to become substantially parallel light, and then passes through the wave plate 9 to become vertically polarized light and passes through the polarizing beam splitter 10B. The transmitted light from the polarizing beam splitter 106 enters the hologram 666, and in addition to the 0th-order tongue tip, there are diffracted light wavefronts 71 to 71 off-axis.
74, this diffracted light is collected by the lens 20, and received by the first detector unit 55. Same, figure (b)
2 shows the photodetector unit 55 and the state of diffracted light on the surface of this photodetector unit.

The difference between this photodetector unit 55 and the photodetector unit 1-5 in the previous two examples is that the forward path from the light source and the return path to the photodetector unit are separated, so that it cannot receive light from the 0th order tongue tip 70. It is possible, and the fumetodetetafuta 50 is formed for that purpose. By detecting the zero-order light, an RF multiplied signal can be easily and efficiently detected. Also, here:
The wavelength plate 9 has a λ15100 design in order to easily balance the performance with the polarizing beam splitter 106, and optimizes the amount of returned light to maximize the S/N ratio of signal detection.

Now, the signal detection method in the second embodiment will be explained in detail. FIG. 4 shows, for example, a photodetector area 511 of the photodetector unit 5 shown in FIG. 1(1)).
~513, Diffracted light 7L72 detected at 521~523
The relationship between the light emitting point 10 and the light emitting point 10 is schematically and generally expressed. FIG. 4(b) shows a case where a focused spot is formed on the disk, and FIGS. 4(a) and (C) each show a defocused state with opposite phases. The FE multiplied signal can be obtained, for example, by taking the differential outputs of photodetectors 512 and 522. The FE multiplied signal detection method using this calculation is called the spot size detection method, and is a well-known technique. Further, the differential output is increased by adding, for example, the outputs of 521 and 523 to the output of the two-fourth detector 512, and the output of 51L513 to the output of 522, respectively. Furthermore, when the wavelength λ2 of the light source changes by δλ to the longer wavelength side, the diffracted lights 71 and 72 of the photodetector 5'' move to 710 and 720, respectively, as shown in FIG. At this time, if each of the photodetectors 511 to 513 and 521 to 523 is formed radially around the convergence point of the 0th order tongue tip (light emitting point 10 of light tv, 1), the tip of the tongue can be moved by the wavelength fluctuation of the light source. Even when the photodetector is moved, a constant amount of diffracted light is always incident on each photodetector, so extremely stable FE signal detection is possible.

Furthermore, if the light source and photodetector unit are misaligned during the assembly process, the FE multiplied signal can be stably detected by simply rotating the hologram element slightly, making adjustment accuracy much higher than before. Improved.

Further, the RF multiplied signal, for example, the photodetectors 511 to 51
It is obtained by summing the outputs of 3,521 to 523.

FIG. 5 is a conceptual diagram showing yet another embodiment of the present invention. FIG. 5A shows functional area divisions of the porogram element 6, and hologram areas 671 and 672 are areas in which a wavefront having a pair of conjugate focal points can be reproduced. A plurality of hologram regions 671 and 672 are formed alternately. FIG. 1(b) shows an OPU photodetector 5 using the hologram element 6 as shown in FIG. 1(a), for example.
The first diffracted light 71 is obtained from the functional region 671 of the hologram element 6, and the diffracted light 73 is obtained from the functional region 672 of the hologram element 6. With this hologram element, no matter what position this hologram element is inserted in with respect to the reflected beam from the disk, the TE signal component will not be mixed into the FE multiplied signal, and the hologram area can be spaced out. Since the two types of holograms are formed independently, diffracted light is generated due to interference between the two types of holograms, and as a result, stable FE multiplied signal detection is possible.

FIG. 6 is a conceptual diagram showing yet another embodiment of the present invention. FIG. 6A shows functional area divisions of the hologram element 61, and hologram areas 673 and 674 are areas in which a wavefront having a pair of conjugate focal points can be reproduced. Figure 1(1)) shows, for example, the OP as shown in Figure 1(a).
Hologram element 6 in fumeto detector Uniso 1-5''2 obtained when hologram element 61 is used in U
1, the diffracted light 711 is transmitted from the functional area 673 of the hologram element 61 to the diffracted light 721.
are each simplified from the functional area 674 of the hologram element 61. The FE multiplied signal detection method is the same as in the fourth embodiment, and is obtained by, for example, the differential output of photodetectors 512 and 522. Furthermore, by adding the outputs of 521 and 523 to the output of photodetector 512 and the outputs of 511 and 513 to the output of 522, the FE multiplied signal output strength is increased. In any case, in the FE multiplied signal detection method shown in this embodiment, there is no problem in omitting the photodetectors 513 and 523 or further 511 and 521, and the obtained FE multiplied signal strength of 1 degree is sufficient. In such cases, the horizontal and configuration can be simplified by omitting the photodetector. On the other hand, if the obtained FE multiplied signal strength is 1 degree or not enough, the first-order diffracted light beams 71 and 73
Sensitivity can be increased by also detecting conjugate lights 72 and 74.

FIG. 7 is a conceptual diagram showing yet another embodiment of the present invention. FIG. 6(a) shows functional area divisions of the hologram element 60, including an area 675 and 676 that can reproduce a wavefront having a conjugate focus of 2 intersections for FE signal detection, and a simple grating pattern for TE signal detection. It consists of an area 68L682 and a non-hologram area 691, each of which is recorded in a direction different from the others. This is, for example, a part of the hologram element of the fifth embodiment in which a diffraction grating for TE detection and a non-hologram region are formed. By making the far field patterns 401 and 402 related to the tracks of the disk included in the beam reflected by the disk incident on the hologram element 60 as shown in FIG.
A good TE multiplied signal can be detected. FIG. 1(b) shows, for example, a hologram element 6 in an OPU as shown in FIG. 1(a).
o and fu,! It shows the wavefront reproduced from the hologram element 60 on the photodetector Unisoto 500 obtained when using the photodetector Unisoto 500,
The diffracted light 712 comes from the functional area 675 of the hologram element 6o, the diffracted light 722 +j comes from the functional area 676 of the hologram element 60, the diffracted light 752 comes from the functional area 675 of the hologram element 60,
The diffracted light 762 is obtained from the functional area 681 and the functional area 682 of the hologram element, respectively. The photodetector unit 500 includes a plurality of photodetectors 51. ．．
52. The photodetector 51 is made up of 511, 512, and 513, and the photodetector 52 is made up of 521, 522, and 523, respectively. In this case, the FE multiplied signal is detected in exactly the same manner as in the fourth embodiment. On the other hand, the TE multiplied signal is obtained by the differential outputs of fumeto detectors 53 and 54. At this time, even if the aperture is restricted due to displacement of the condensing lens, the T2O E signal can be stably detected. In addition, TE4! There are no particular restrictions on the shape and size of the diffraction grating and non-hologram region for ii. Moreover, this diffraction grating for TE detection can be implemented in other embodiments as well. Further, the hologram elements of the present invention shown in the fifth to seventh embodiments can be easily produced by general methods such as three-beam interferometry and pattern generation using a computer.

FIG. 8 shows an embodiment of an optical information device constructed using the optical pickup head device described below. The optical storage q medium (optical disk 4) is rotated by a pulsation quadrature 81. The optical pickup head device 80 also sends a signal corresponding to the positional relationship with the optical disk 4 to the electric circuit 8.
Send to 3. The electric circuit 83 increases, intensifies, or calculates this signal and outputs a signal for finely moving the optical pickup head device 80 or the objective lens within the optical pickup head device. 82 is a drive device for the optical pickup head device, and 85 is a drive device for an objective lens in the optical pickup head device. Based on the signals and the drive device 82 or 85, the optical disc 4 is subjected to text, focus servo, and track/queue servo, and information is read, written, or erased from the optical disc 4. Reference numeral 84 denotes a power supply or a connection part with an external power supply, from which electricity is supplied to the electric circuit 83, the drive device 82 of the optical pink-up head device, the drive mechanism 81 of the optical disk, and the objective lens drive device 85. Also, are the power supply or external power supply connection terminals for each drive circuit? There is no problem even if each road has one.

Effects of the Invention In the present invention, the hologram element has a hologram element whose pologram surface is spatially divided into at least two parts, each of which records one diverging or converging wavefront, and at least one wavefront from the hologram element. O next time,
A photodetector that receives light from the tip of the tongue at times other than the tip of the tongue has a band-like shape, and is arranged in a shape that extends approximately in parallel along a radial direction centering on one area dividing line of the photodetector or a convergence point of the 0th order tip of the tongue from the hologram element. A focus error (FE) signal is detected using a photodetector, and a tracking error (TE) signal is detected using a hologram element in which a portion of the hologram element has different diffraction patterns, gratings or diffraction patterns, a fold grating, and a non-hologram area. The detection has the following effects.

(I) Even if the diffraction angle from the hologram element changes due to wavelength fluctuations in the light source, a constant amount of diffracted light always enters each photodetector, so the focus error (F'E) signal and tracking error (TE) ) signal and high frequency information (RIi”) signal are detected extremely stably.
I can put it out.

(n) The alignment of the photodetector can be simplified to the extent that almost no adjustment is required or the hologram element is rotated only once.

(I) Since the 1 degree positional accuracy of the photodetector is relaxed, it is possible to stably detect the FE multiplied signal and the TE multiplied signal.

(IV) Since the FE multiplied signal, TE multiplied signal, or even RF multiplied signal can be detected with a photodetector formed on one substrate, the configuration of the optical system becomes easy, and the number of parts can be reduced, the price can be lowered, and miniaturization can be achieved. Become.

(V) By expanding the tolerance range for the wavelength fluctuation of the light source and the position adjustment of the photodetector, the optical pickup head device of the present invention is stable and reliable even in environments with extremely rapid temperature changes, even though it uses a semiconductor laser as the light source. Sexual movements become possible.

(VI) In this hologram element, since the FE multiplied signal and the TE multiplied signal are detected independently, a stable signal can be obtained.

(■) In this hologram element, by forming two types of regions independently, diffracted light due to beats of the hologram pattern is not generated, and stable FE multiplied signal detection is possible.

(■) When detecting a TE multiplied signal using this hologram element, there are restrictions on the aperture 1 of the condensing lens.
A stable signal can be detected even with slight defocus.

(IX) An optical information device configured using the optical pickup head device of the present invention can stably detect an FE multiplied signal and a TE multiplied signal, and thus becomes a highly reliable optical information device.

(X) Since the present optical pickup head device has a small number of parts and is inexpensive, an optical information device constructed using the present optical pickup head device is an inexpensive and small-sized optical information device.

[Brief explanation of the drawing]

FIG. 1(a) is a schematic configuration diagram of an optical pickup head device showing a sixth embodiment of the present invention, and FIG. 1(b) is the same as FIG. 1(a).
FIG. 2 is a diagram showing the relationship between the photodetector and the diffracted light in the optical pickup head device shown in FIG. 2, which is another embodiment 1 of the present invention.
A conceptual diagram of an optical pickup head device showing an example, Fig. 3 (
4A is a conceptual diagram of an optical pickup head device showing another embodiment of the present invention; FIG. 4B is a diagram of the relationship between the photodetector and diffracted light in the optical pickup head device shown in FIG. (a)+(b), (c) are general principle diagrams explaining the present invention, FIG. 5(a) is a configuration diagram of a hologram element explaining the present invention in detail, and FIG. FIG. 6(a) is a diagram showing the relationship between the diffracted light and the photodetector in the optical pickup head device using the hologram element shown in FIG. 6(a), and FIG. (b) is a relationship diagram between diffracted light and a photodetector in an optical pickup head device using a hologram element, which is not shown in FIGS. 7(a and 7).
1(a) and 1(b) are block diagrams of a hologram element explaining another embodiment of the present invention, and FIG. 1 and 8 are cross-sectional views (omitted) of the optical information device according to the embodiment of the present invention, and FIGS. 9(a) and 9(b).
L(c) is a conceptual diagram of a method for detecting a nail error signal in the optical system of a conventional optical pickup head device, and FIG. 10 shows an example of an astigmatism wavefront detection system in the optical system of a conventional optical pickup head device. FIG. 1.-Fist semiconductor laser or equivalent coherent light source, 2..Collimating lens, 3..φ lens, 4..
Optical storage, medium (optical disk), 5... Photodetector unit, 6... Porogram element, 10, Φ, light emitting point, 41, Φ, protective film, 42... Substrate, 50-54
・Φ・F, AI・Detector, 55...Photodetector unit 60...Hologram element, 61 life...Hologram element, 65...times, folded grating, 66.Fist Φ diffraction grating, 67...Fist Hologram area, 70...0th order tongue tip, 71-74, skewer, 1st order. tip of tongue, 40140
2...Far field pattern, 671-676.
...Hologram area, Agent's name: Patent attorney Shigetaka Awano, 1 person Uko ＼ Ward q） Sorry illusion

Claims (4)

[Claims] (1) A radiation light source, a condensing optical system that receives the beam from the light source and converges it onto a minute spot on the optical storage medium, a hologram element that receives the beam reflected by the optical storage medium and generates diffracted light, and a focus error. a photodetector that receives diffracted light from the hologram element for detecting a signal, a tracking error signal, or a high frequency information signal, and the hologram surface of the hologram element is spatially divided into at least two parts, One diverging or converging wavefront is recorded on each hologram surface of the hologram element, and a plurality of photodetectors each having a band-like shape receive diffracted light other than at least the 0th-order diffracted light from the hologram element. An optical pickup head device characterized in that the region dividing lines are arranged in a shape such that they extend approximately parallel to each other along a radial direction centered on a convergence point of zero-order diffracted light from a hologram element. (2) a radiation light source, a condensing optical system that receives the beam from the light source and converges it onto a minute spot on the optical storage medium, a hologram element that receives the beam reflected by the optical storage medium and generates diffracted light, and a focus error. a photodetector that receives diffracted light from the hologram element for detecting a signal, a tracking error signal, or a high-frequency information signal, and two diverging or converging wave fronts are recorded on the hologram surface of the hologram element, and the hologram The hologram surface of the element is spatially divided into a plurality of regions, and each divided region has one of the two diverging or converging wavefronts.
A plurality of photodetectors have a band-like shape, and each of the photodetectors receives diffracted light other than at least the 0th-order diffracted light from the hologram element, and a region dividing line of the photodetector is a convergence of the 0th-order diffracted light from the hologram element. An optical pickup head device characterized by having a shape extending approximately parallel to each other along a radial direction centered on a point. (3) In the optical pickup head device according to claim 1 or 2, a different diffraction grating or diffraction grating and a non-hologram area for detecting a tracking error signal or a high frequency information signal in a part of the hologram element. An optical pickup head device comprising: (4) A drive mechanism for an optical storage medium, an optical pickup head device according to any one of claims 1 to 3, and a focus error signal and a tracking error signal obtained from the optical pickup head device. An optical information device comprising at least a focus servo mechanism and a tracking servo mechanism, an electric circuit for realizing the servo mechanism, and a connection portion to a power source or an external power source.