JPH11296895A - Optical pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and small-sized optical pickup device with an excellent temp. characteristic, recording/reproducing information of optical recording media of plural standards. SOLUTION: The optical pickup device having plural light sources 1, 2 with plural different wavelengths is provided with an optical means 3 guiding beams of these plural light sources 1, 2 to the optical recording medeum surfaces 10, a hologram 4 refracting the beams of two or more different wavelengths among reflected beams from the optical recording medeum 10 and a photodetector 11 capable of light receiving refracted beams 12 of plural different wavelengths from the hologram 4 and arranged being separated from the light sources 1, 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical pickup provided with a plurality of light sources having different wavelengths for reproducing a plurality of types of optical storage media.

[0002]

2. Description of the Related Art Hitherto, an optical pickup provided with a light source for reproducing a CD has been used in a reproducing apparatus for a compact disk (hereinafter, referred to as a CD). Also, recently, for reasons such as cost reduction and improvement of production efficiency, a stable reproduction of a CD has been made possible by integrating a light source and a reading unit into a unit. on the other hand,
In recent years, the standards for digital video discs or digital versatile discs (hereinafter, referred to as DVDs) have been established, DVD recording / reproducing devices have been released, and DVD software sales have increased. It is getting.
By the way, the CD and the DVD have the same outer dimensions of the disk, but have different storage methods, so that the frequency and optical system of the light source used for reproduction are different. Therefore, basically, two types of playback devices are required to play a CD and a DVD. However, it is more convenient for the user to integrate the playback device into one device than to split the playback device into two. Several optical pickups capable of reproducing both CDs and DVDs have been proposed because they are easy to use. Hereinafter, an optical pickup capable of reproducing both a CD and a DVD as described above will be described with reference to the drawings. FIG.
FIG. 11 is a diagram showing a first conventional example of an optical pickup capable of reproducing both D and DVD. FIG. 13 is a collection of preprints of the 1997 Spring Society of Applied Physics (30p-NF-2) “LD
FIG. 2 is a side view schematically showing a structure shown in “2-wavelength optical head for DVD using PD unit”. The optical pickup shown in FIG.
A 0-nm laser (hereinafter, referred to as LD) light source 82 and an LD-CD unit 94 for CD in which a light receiving unit 92 is integrated, and 650 n for reproducing DVD media.
DV in which the LD light source 81 and the light receiving unit 91 are integrated
LD-CD unit 93 for D, wavelength filter 83,
It comprises a condenser lens 85, a rising mirror 86, a polarization hologram 87, an aperture filter and a wavelength plate 88, an objective lens 89, and an optical recording medium 90. In the above configuration, the aperture filter has a wavelength plate for the light from the LD light source 82 of 790 nm, and the DVD light source 81 of 650 nm.
The optical system of the CD is not affected by the polarization hologram 87 because it is designed to be a quarter-wave plate with respect to light from the optical disk. Therefore, the LD-CD unit for DVD can be adopted while the conventional LD-PD unit for CD is used, and it is possible to support various media of CD system and DVD system.

FIG. 14 is a diagram showing a second conventional example of an optical pickup capable of reproducing both a CD and a DVD. FIG. 14 is FIG. 1 of Japanese Patent Application Laid-Open No. Hei 9-138567, “Optical Pickup Device”. The optical pickup of FIG.
Laser light source 101 of first wavelength and its first photodetector 1
10, a first hologram laser unit 112 in which the first hologram element 103 is unitized, a laser light source 102 of a second wavelength, a second photodetector 111 thereof, and a second
Hologram laser unit 113 in which hologram element 104 is unitized, and laser light source 101
From the laser 105 and light 106 from the laser light source 102
Is composed of a polarization beam splitter 107, an objective lens 108, and an optical recording medium 109 on which the light beam enters. In the above configuration, by providing two hologram laser units 112 and 113 equipped with LD light sources having different wavelengths, the optical recording medium 109 having different substrate thickness can be reproduced. Further, the laser light sources 101 and 102 in the hologram laser units 112 and 113 and the light detector 11
The hologram elements 103 and 104 and the hologram elements 103 and 104 are designed corresponding to optical recording media (CD and DVD) having respective substrate thicknesses.

[0004]

However, FIG.
In the case of using an element in which a laser light source and its light receiving unit (photodetector) are integrated (unitized or packaged) as in the optical pickup of FIG. 14, the temperature characteristics of the integrated element deteriorate. More specifically, a high-output LD is required to support a recordable optical medium, but a high current flows through the LD to increase the output, and the temperature of the entire package rises. This makes it difficult for the PDs in the same package to operate stably, making it impossible to obtain sufficient signal characteristics especially when operating at high speed. When two hologram laser units are used as shown in FIG. 14, for example, there are two hologram laser units having a 780 nm light source and two hologram laser units having a 650 nm light source. , And the cost is high and miniaturization is difficult. In particular, when an optical medium capable of recording at both wavelengths is to be used, it is desirable to use a polarizing hologram as a hologram. However, a polarizing hologram is expensive, and if two such holograms are provided, the cost of the entire pickup will be reduced. Will be up. SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an inexpensive, compact, and good temperature characteristic optical pickup device capable of recording and reproducing information on an optical recording medium of a plurality of standards. Aim.

[0005]

In order to achieve the above object, an optical pickup device according to the first aspect of the present invention comprises a plurality of light sources having different wavelengths. An optical means for guiding to a recording medium surface, and at least two of reflected light from the optical recording medium
A hologram that diffracts light of two or more different wavelengths, and a light receiving element that can receive diffracted light of a plurality of different wavelengths from the hologram and is arranged separately from the light source, By using a hologram and a light receiving element in common for light sources of a plurality of wavelengths, the number of components can be reduced and the size can be reduced, and the temperature characteristics can be improved by using a separate package for the LD and PD. In the optical pickup device according to the second aspect of the present invention,
In an optical pickup device having a plurality of light sources having different wavelengths, an optical unit for guiding light from the plurality of light sources to an optical recording medium surface, and light having at least two or more different wavelengths out of reflected light from the optical recording medium. A hologram to be diffracted, and a light receiving element that can receive diffracted light of a plurality of different wavelengths from the hologram and can also receive monitor light of the light source and that is arranged separately from the light source. The feature is that by making the light receiving element for signal detection and the light receiving element for monitoring the light source common to one,
Further, the number of parts can be reduced.

According to a third aspect of the present invention, in the optical pickup device of the first or second aspect, a reflecting surface means for reflecting the diffracted light from the hologram and making the light incident on the light receiving element is provided. It is characterized in that it is arranged in the optical path, and guides the diffracted light from the hologram to the light-receiving element using the reflection surface means, thereby facilitating the processing of the hologram and reducing the cost. Also, by preventing the monitor light from entering the signal detecting light receiving element from the optical recording medium, highly sensitive signal detection can be performed. According to a fourth aspect of the present invention, in the optical pickup device of the third aspect, the reflecting surface means is arranged so as to block a part of monitor light from the light source from entering the light receiving element, The reliability of the signal can be improved by blocking the monitor light with the reflection surface means so as not to enter the light receiving element for signal detection.

According to a fifth aspect of the present invention, in the optical pickup device according to any one of the second to fourth aspects, the plurality of light sources having different wavelengths receive light emitted from the light source onto an optical recording medium. Having at least one first light source for accommodating a first light source for receiving light from a second light source, the second light receiving element further comprising the first light source. Characterized in that it is arranged separately from the second light source so as to be able to receive only monitor light of light from the optical disc. The unit that integrates LD, PD, and hologram during mass production can be used, so that development costs and assembly adjustments can be avoided, thereby reducing costs and simplifying adjustments. . According to a sixth aspect of the present invention, in the optical pickup device according to any one of the first to fifth aspects, the light sources of the plurality of different wavelengths rotate a polarization direction of light emitted from the light source. Means for transmitting a hologram after the polarization directions of light from all light sources are substantially matched by the polarization direction rotating means. A plurality of light sources are used in order to correspond to a standard optical recording medium. By adjusting the polarization directions of these light sources so that the characteristics of the hologram are exhibited, light use efficiency is high and signal detection with high sensitivity can be performed.

According to a seventh aspect of the present invention, in the optical pickup device according to any one of the first to sixth aspects, the hologram is guided to the light receiving element rather than the amount of diffracted light not guided to the light receiving element. It is characterized by having a structure in which the amount of diffracted light becomes large, and by producing a hologram that does not generate unnecessary diffracted light unrelated to signal detection, highly sensitive signal characteristics can be obtained. The present invention of claim 8 is the first invention.
8. The optical pickup device according to any one of items 1 to 7, wherein the light receiving element is arranged such that a light receiving surface is fitted on a focal point of each of diffracted lights having different wavelengths. The reliability can be enhanced by accurately aligning a plurality of spots with the same light receiving element.

According to a ninth aspect of the present invention, in the optical pickup device according to any one of the first to seventh aspects, the collimating lens and the hologram provided in the optical pickup have chromatic aberrations which are different from each other. The configuration is such that the chromatic aberration is canceled by the lens and the hologram, whereby the stability can be improved.
According to a tenth aspect of the present invention, in the optical pickup device according to any one of the first to eighth aspects, the light source, the hologram, the light receiving element, and the wavelength filter, or the light source, the hologram, the light receiving element, The wavelength filter and the reflection surface means are fixed to respective positions and housed in one housing, and the light source, the hologram, the light receiving element, and the wavelength filter, or the light source, the hologram, the light receiving element, By housing the wavelength filter and the reflection surface in one housing and fixing them at appropriate positions, miniaturization and improvement in stability can be achieved.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram of an embodiment of the optical pickup device of the present invention. The optical pickup device shown in FIG. 1 includes a light source 1 and a light source 2 that output two different wavelengths of light, a wavelength filter 3 that makes the emission directions of both lights the same, and a polarization hologram that transmits and diffracts light according to the polarization direction of the light. 4. a collimating lens 5 that converts the diffused light into parallel light or converts the parallel light into convergent light; a mirror 6 that changes the traveling direction of the light;
A quarter-wave plate 7 for changing the polarization direction, a filter 8 for adjusting the numerical aperture, an objective lens 9 for condensing light on an optical recording medium,
The light receiving element 11 receives the light diffracted by the polarization hologram 4. In FIG. 1, 650n
m emitted from the light source 1 pass through the wavelength filter 3 and also pass through the polarization hologram 4 and the collimating lens 5
Is turned into parallel light. The light source 1 has a wavelength of 650 nm.
Instead, it may be 635 nm. The luminous flux that has become parallel light is
After being reflected by the mirror 6, it becomes circularly polarized light by the 波長 wavelength plate 7, passes through a filter 8 for adjusting the numerical aperture, and is condensed on an optical recording medium 10 by an objective lens 9. The reflected light after reading the information on the optical recording medium 10 passes through the objective lens 9, the filter 8 for adjusting the numerical aperture again, and the quarter-wave plate 7, and the polarization direction when emitted is 90 degrees. The light becomes the linearly polarized light whose direction has been changed, is reflected by the mirror 6, and returns to the collimator lens 5. The light converged by the collimating lens 5 is diffracted by the polarization hologram 4 to become a diffracted light 12 and is guided to the light receiving element 11.

In the same manner as described above, light emitted from the light source 2 of 780 nm is reflected by the wavelength filter 3, passes through the polarizing hologram 4, and becomes parallel light by the collimating lens 5. In addition, regarding the description of the parallel light, it is conceivable that both wavelengths do not always become parallel light in order to correct the difference in the substrate thickness of the disk, but one becomes non-parallel light. However, whether or not the light is a parallel light is not related to the essence of the present invention. The collimated light beam is reflected by the mirror 6, passes through a filter 8 for adjusting the numerical aperture, and is condensed on an optical recording medium 10 by an objective lens 9. And
The reflected light from the light source 2 also reads the information on the optical recording medium 10 and returns to the collimating lens 5 again along the same path as the reflected light from the light source 1 of 650 nm. The light converged by the collimator lens 5 is diffracted by the polarization hologram 4 to become a diffracted light 12 and is guided to the light receiving element 11 in the same manner as the light flux of the light source 1. With the configuration as shown in FIG. 1, an optical pickup device can be configured with one polarizing hologram and one light receiving element even if there are two light sources. Although the spot positions on the light receiving element 11 are slightly different due to the different wavelengths of the light source 1 and the light source 2, the light receiving area of the light receiving element 11 can be increased accordingly, or the light receiving surface can be divided into spots. It is possible to cope by matching.

Next, FIG. 2 shows a configuration of an optical pickup device in which a signal detection light receiving element 10 has a light source 1 and a light source 2 monitoring function. In FIG. 2, the light emitted from the light source 1 should ideally transmit 100% through the wavelength filter 3, but actually does not necessarily transmit 100%, and a few% are reflected by the film inside the wavelength filter 3. Then, the light proceeds as leakage light (monitor light) 24 toward the light receiving element 21. When the light source 1 is a light source having a particularly large emission angle, the amount of light reflected from the characteristics of the film of the wavelength filter 3 increases.
Similarly, the light emitted from the light source 2 should originally be reflected 100% by the film inside the wavelength filter 3, but in reality, it is not necessarily reflected 100%, but several percent is transmitted, and the transmitted light is leaked. The light (monitor light) 24 travels toward the light receiving element 21. Wavelength filter 3 as described above
By receiving the light leaking from the light receiving element 21, the power fluctuation of the light source 1 and the light source 2 can be monitored. In addition, as shown in FIG. 3, if the above-described leaked light is received by the light receiving surface 22 different from the light receiving surface 23 that receives the reflected light from the optical recording medium 10 among the same light receiving elements 21, one With the light receiving element, the light receiving element for signal detection and the light receiving element for monitoring the front of the light source can be shared. In that case, the amount of light leaking can be changed by changing the characteristics of the film of the wavelength filter 3, so that a desired monitor light amount can be obtained. Therefore, the stability of the light source can be optimized because the light source can be reliably monitored.

Next, as shown in FIG. 4, a configuration will be described in which a reflection surface 32 is provided in the optical path until the diffracted light 12 from the polarizing hologram 4 is guided to the light receiving element 10. As shown in FIG. 4, the light receiving element 31 reflects the diffracted light 12 from the polarizing hologram 4 on the reflecting surface 32.
To the diffraction light 1 even if the separation angle 33 is small.
2 can be detected by the light receiving element 31. Without this reflection surface 32, the diffracted light 12 hits the wavelength filter 3 and is not guided to the light receiving element 31, so that signal detection becomes impossible. If the separation angle 33 of the polarizing hologram 4 is increased, the diffracted light 12 can be directly incident on the light receiving element 31 without the reflection surface 32. The pitch must be reduced. If the pitch of the polarizing hologram 4 is reduced, the following problem occurs. 1. Decreasing diffraction efficiency When the pitch of the polarizing hologram 4 is reduced, the grating shape cannot be formed as an ideal shape from the viewpoint of the accuracy of the processing process, so that the diffraction efficiency decreases. 2. Increase in wavelength fluctuation When the pitch of the polarizing hologram 4 is small, the diffraction angle fluctuation with respect to the wavelength fluctuation becomes large, so that the spot position fluctuation of the signal light on the light receiving element 31 becomes large and the signal is likely to be offset. . By providing the reflecting surface 32, the pitch of the polarizing hologram 4 does not need to be reduced, and the cause of the above-mentioned problem can be eliminated, so that highly efficient and stable signal detection can be performed.

Further, as shown in FIG. 5, if the reflection surface 44 is arranged so as to block a part of the monitor light from the wavelength filter 3, the diffracted light 12 as the signal light and the monitor light can be completely separated. And more accurate signal detection becomes possible. In addition, as shown in FIG. 6, when the reflection surface of the diffracted light 12 is integrated with a part of the wavelength filter 54, the assembly process of the optical pickup can be simplified. By the way, in the various embodiments described above, the signal detection of all the light sources having different wavelengths is performed by the light receiving element 11, 21, or 31, but for example, 780 nm of 780 nm for reproducing an optical disk of CD is used. Since the light source is a well-established technology, the pickup is often also unitized, and the light source and the light receiving element are integrated or integrated including the hologram in addition to the above configuration. It is often mass-produced. In such a case, higher stability can be obtained at lower cost by using a unitized unit than by using an optical pickup in which a light source and a light receiving element are separated from each other. Therefore, in such a case, the light receiving elements 11 and 21 described above are used.
Or 31 is used only for detecting the front monitor light from the unit in which the light source and the light receiving element are integrated, and simplifies the adjustment by using the integrated unit for detecting the signal of the optical recording medium 10. can do.

Next, the case where the transmission modes of the light from the respective light sources are different will be described with reference to FIG. Light source 1 or 2
Is almost linearly polarized light, but its transmission mode is a TE mode or a TM mode. Therefore, not all light sources have the same polarization direction,
Between light sources having different wavelengths (for example, a light source of 780 nm and a light source of 635 nm)
(nm light source), the polarization directions may differ by 90 degrees. However, since the polarization direction of the polarization hologram 4 having a high diffraction efficiency is determined in advance, the polarization hologram 4 cannot have its original performance unless polarized light is incident on the polarization hologram 4. Therefore, in order to match the performance of the polarizing hologram 4, the polarization directions of the plurality of light sources must all be the same. Therefore, as shown in FIG. 7, an element 55 that functions as a half-wave plate only for light of a specific wavelength is arranged between the wavelength filter 3 and the polarizing hologram 4, and for example, the light source 1 When the light source 2 is in the TE mode in the TM mode, the polarization direction of the light of either wavelength is turned 90 degrees by the element 55 of the half-wave plate so as to match the polarization direction of the other light source. Accordingly, high light use efficiency can be realized for light of all wavelengths.

Next, optimization of the structure of the polarization hologram 61 will be described with reference to FIG. Polarizing hologram 6
1 generates 0th order light, ± 1st order light, ± 2nd order light, as shown in FIG. 8, but here, it is assumed that only the + 1st order light is received by the light receiving element 11. In order to improve the signal characteristics in the case of the configuration shown in FIG. 8, it is desirable that the + 1st-order light has as much light quantity as possible, that is, that the diffraction efficiency of the + 1st-order light is high. For this purpose, as shown in FIGS. 9A to 9C showing variations of the polarizing hologram, FIG.
Blazing the cross-sectional structure of the polarizing hologram 62,
(B) The cross-sectional structure of the polarizing hologram 63 is stepped, or conventionally proposed by the present inventor (c).
The diffraction efficiency of the + 1st order light of the polarizing hologram is increased by using a dual grating or the like.

Next, an embodiment in which the arrangement of the light receiving elements is optimized will be described with reference to FIG. As shown in FIG. 10, when light of different wavelengths enters the hologram 4, they are diffracted at different angles, and condensed at different positions. In such a case, for example, if the knife edge method is used as the focus detection method, it is necessary to adjust the light receiving surface of the light receiving element 71 so that the light receiving surface of the light receiving element 71 coincides with the spot position which is the focal point of the light of any wavelength. . Therefore, by arranging the light receiving surface of the light receiving element 71 at an angle so that the light receiving surface of the light receiving element 71 coincides with the spot position of each wavelength condensed at a different position, the light receiving surface can be adjusted to both spot positions. This makes it possible to perform focus detection for both spot positions by the knife edge method. Here, the knife edge method has been described as an example, but the astigmatism method and the beam size method can be similarly applied. Next, a method of using the chromatic aberration of the hologram 4 and the collimating lens 5 as shown in FIG. 11 to optimize the spot position on the light receiving element will be described. Generally, since the polarization hologram 4 has very good wavelength selectivity, it is considered that the polarization hologram 4 is equivalent to having a large chromatic aberration. When the polarizing hologram 4 has a lens function, the relationship between the focal length f of the lens and the wavelength λ has an inversely proportional relationship such that fλ = constant. On the other hand, the chromatic aberration of the glass material of the collimating lens 5 generally has a proportional relationship between the focal length f of the lens and the wavelength λ. Therefore,
As shown in FIG. 11, by combining the polarizing hologram 4 in which the relationship between the focal length f and the wavelength λ is inversely proportional, and the collimating lens 5 in which the relationship is proportional, the light receiving element 7 is formed.
The influence of spot chromatic aberration on two surfaces can be reduced. With this configuration, the inclination of the light receiving element 72 can be reduced, and the mounting tolerance can be increased.

FIG. 12 shows an embodiment in which each optical element having the above-described configuration is housed in one housing to form a cell structure. Light sources 1 and 2, polarizing hologram 4, light receiving element 51 and wavelength filter 54, or light sources 1 and 2 and hologram 4
The light receiving element 51, the wavelength filter 54, and the reflection surface provided on a part of the wavelength filter 54 are accommodated in a housing 73 and fixed at predetermined positions. Such a cell structure has the following advantages. 1. The size can be reduced. 2. The integrated structure eliminates displacement of each component. 3. Since it is possible to individually assemble only the cell portion, it is easy to assemble the optical pickup. By using the cell structure as shown in FIG. 12, the same stability as that of the conventional hologram laser unit can be obtained, so that both low cost and high reliability can be achieved.

[0019]

As described above, according to the first aspect of the present invention,
Since light sources of a plurality of wavelengths are used, recording and reproduction of optical discs of various standards can be performed, and the number of components can be reduced and the size can be reduced by using a common polarizing hologram and light receiving element. In addition, by using a separate package for the light source and the light receiving element, the temperature characteristics are improved, and even when a higher-speed signal characteristic is required for the optical pickup, the speed can be increased simply by replacing the light receiving element. It becomes possible. According to the present invention of claim 2, claim 1
In addition to the same effects as described above, the number of components can be further reduced and the cost can be reduced by using a single light receiving element for signal detection and a single light receiving element for monitoring the light source. According to the third aspect of the present invention, by guiding the diffracted light from the polarizing hologram to the light receiving element using the reflecting surface, the pitch of the polarizing hologram may be large, so that the processing is easy and high accuracy can be achieved. Therefore, cost reduction and high efficiency can be achieved. Further, since the light receiving element can be arranged so that the monitor light does not enter the signal detecting light receiving element from the optical recording medium, signal detection with high sensitivity is possible. According to the fourth aspect of the present invention, the monitor light is blocked by the reflection surface, so that the monitor light does not enter the signal detection light receiving element, and high-sensitivity signal detection becomes possible. Further, the integration of the optical pickup can be facilitated by integrating the reflection surface and the wavelength filter. According to the fifth aspect of the present invention, in order to record and reproduce an optical recording medium of an established standard, a unit in which a mass-produced light source and a light receiving element or a light source, a light receiving element and a hologram are integrated is used. By doing
The development cost for the combination of a new light source and a light receiving element and the cost for the adjustment of the optical pickup can be reduced, thereby reducing the cost and simplifying the adjustment by using the unit. According to the sixth aspect of the present invention, the direction of polarization of light from a plurality of light sources used to support an optical recording medium of a plurality of standards is exhibited by the characteristics of a polarizing hologram used in the optical pickup device. By providing a means for matching, the light use efficiency is increased,
Highly sensitive signal detection becomes possible. According to the seventh aspect of the present invention, a highly sensitive signal characteristic can be obtained by using a polarizing hologram that does not generate unnecessary diffracted light unrelated to signal detection, and the C / N is reduced by flare light. And speeding up the signal can be realized. According to the eighth aspect of the present invention, the reliability can be improved by allowing a plurality of focal spots to be accurately positioned by the same light receiving element. In the ninth aspect of the present invention, the chromatic aberration is canceled by the characteristics of the lens and the characteristics of the hologram, so that a positional shift due to a fluctuation in the wavelength of the light source or a fluctuation in the light source itself can be reduced, and the stability of signal detection can be improved. According to the tenth aspect of the present invention, since the components of the light source, the wavelength filter, the light receiving element, and the polarization hologram have a cell structure, it is possible to achieve both low cost and high reliability. In addition, since the cell can be assembled as a single unit, the entire optical pickup can be easily assembled.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an embodiment of an optical pickup device of the present invention.

FIG. 2 is a diagram illustrating a configuration of an optical pickup device in which a signal detection light receiving element has a light source monitoring function.

FIG. 3 is a diagram illustrating a configuration of a light receiving element configured to receive light leaked from a light receiving surface different from a light receiving surface that receives reflected light from an optical recording medium.

FIG. 4 is a diagram showing a configuration in which a reflection surface is provided in an optical path until diffracted light from a polarizing hologram is guided to a light receiving element.

FIG. 5 is a diagram showing a configuration in which a reflection surface is arranged so as to block a part of monitor light from a wavelength filter.

FIG. 6 is a diagram illustrating a configuration in which a reflection surface of diffracted light is integrated with a part of a wavelength filter.

FIG. 7 is a diagram showing a configuration in which an element that functions as a half-wave plate only for light of a specific wavelength is arranged between a wavelength filter and a polarizing hologram.

FIG. 8 shows that the polarization hologram has 0 order light, ± 1 order light, ± 2 order.
FIG. 5 is a diagram illustrating a state where a next light or the like is generated.

FIGS. 9A to 9C are diagrams showing variations of a polarizing hologram.

FIG. 10 is a diagram showing an embodiment in which the arrangement of light receiving elements is optimized.

FIG. 11 is a diagram showing an embodiment in which a spot position on a light receiving element is optimized.

FIG. 12 is a diagram showing an embodiment in which each optical element has a cell structure accommodated in one housing.

FIG. 13 is a diagram showing a first conventional example of an optical pickup capable of reproducing both a CD and a DVD.

FIG. 14 is a diagram showing a second conventional example of an optical pickup capable of reproducing both a CD and a DVD.

[Explanation of symbols]

1, 2, 81, 82, 101, 102 ... light source 3,
54, 83 ... wavelength filters, 4, 61, 62, 6
3, 64, 87: polarizing hologram, 5: collimating lens, 6: mirror, 7: 1/4 wavelength plate, 8: filter, 9, 89, 108: objective Lens, 10, 90109, optical recording medium, 11, 2
1, 31, 51, 71, 72... Light receiving element, 12,.
Diffracted light, 22, 23: light receiving surface, 24: leaked light (monitor light), 32, 44: reflective surface, 33: separation angle, 55: element (1/2 wavelength) Plate), 73 ... housing, 85 ... condenser lens, 86 ... rising mirror, 88 ... aperture filter and wavelength plate, 91, 92
..Light receiving section, 93 ... LD-CD unit for DVD,
94 ··· LD-CD unit for CD, 103, 104
... hologram, 105, 106 ... light, 107-
..Polarizing beam splitters, 110, 111... Photodetectors, 112, 113.

Claims (10)

[Claims] 1. An optical pickup device having a plurality of light sources having different wavelengths, an optical unit for guiding light from the plurality of light sources to an optical recording medium surface, and at least two or more of light reflected from the optical recording medium. An optical pickup device comprising: a hologram for diffracting light of different wavelengths; and a light receiving element capable of receiving a plurality of diffracted lights of different wavelengths from the hologram and arranged separately from the light source. . 2. An optical pickup device having a plurality of light sources having different wavelengths, an optical unit for guiding light from the plurality of light sources to an optical recording medium surface, and at least two or more of reflected light from the optical recording medium. A hologram for diffracting light of different wavelengths, and a light receiving element capable of receiving diffracted light of a plurality of different wavelengths from the hologram and capable of receiving monitor light of the light source and arranged separately from the light source An optical pickup device comprising: 3. The hologram and a light receiving element according to claim 1, wherein a reflection surface means for reflecting the diffracted light from the hologram and entering the light receiving element is arranged in an optical path between the hologram and the light receiving element. Optical pickup device. 4. The optical pickup device according to claim 3, wherein said reflection surface means is arranged so as to block a part of monitor light from said light source from entering said light receiving element. 5. The light source having a plurality of different wavelengths includes at least one first light source that accommodates a first light receiving element for receiving light emitted from the light source onto an optical recording medium in a same package. A second light receiving element for receiving light from the second light source, further comprising the second light source and the second light source so as to be able to receive only monitor light of the light from the first light source. 5. The device according to claim 2, wherein the components are arranged separately.
The optical pickup device according to claim 1. 6. The light source of a plurality of different wavelengths has at least one first light source provided with a polarization direction rotating means for rotating a polarization direction of light emitted from the light source, and the polarization direction rotating means The optical pickup device according to any one of claims 1 to 5, wherein the hologram is transmitted after the polarization directions of light from all light sources are substantially matched. 7. The hologram according to claim 1, wherein the hologram has a structure in which the amount of diffracted light guided to the light receiving element is larger than the amount of diffracted light not guided to the light receiving element. 2. The optical pickup device according to claim 1. 8. The light-receiving element according to claim 1, wherein the light-receiving element is arranged so that a light-receiving surface is located on a converging point of each of a plurality of diffracted lights having different wavelengths. An optical pickup device according to item 1. 9. The collimating lens and the hologram provided in the optical pickup, wherein chromatic aberrations of the collimating lens and the hologram cancel each other out. An optical pickup device according to item 1. 10. A case in which the light source, the hologram, the light receiving element, and the wavelength filter, or the light source, the hologram, the light receiving element, the wavelength filter, and the reflection surface are fixed at respective positions. The optical pickup device according to claim 1, wherein the optical pickup device is housed in a body.