JPH02185750A - Optical pickup - Google Patents

Abstract

PURPOSE:To decrease the number of parts, to facilitate assembly, to reduce the size and weight, and to shorten head access time by providing a prism with a beam shaping function, beam splitter function, and polarized beam splitter. CONSTITUTION:The laser light emitted from a laser diode 22 is provided with 180 deg. phase difference by a means 24 for providing 180 deg. phase difference and is made incident on the prism 26. The laser light is shaped by the 1st face 26a of the prism 26 and is emitted from the 2nd face 26b. The emitted laser light converges onto a magneto-optical recording medium 21 via an objective lens 25. The reflected laser light is made incident on the 2nd face 26b and is then reflected by the 1st face 26a. Of this laser light, the 1st polarization component is transmitted from the 3rd face 26c and is detected in the 1st detecting part 29. The 2nd polarization component reflected by the 3rd face 26c is transmitted from the 4th face 26d and is detected in the 2nd detecting part 30. The number of parts is decreased in this way and the assembly is facilitated. The reduction of the size and weight is possible and the head access time is shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical pickup for writing or reading information into or from a magneto-optical recording medium.

(Background of the Invention) Next, a conventional example will be explained using the drawings. FIG. 12 is a configuration diagram showing an example of the conventional method, FIG. 13 is a diagram explaining the anisotropy of the laser beam emitted from the laser diode in FIG. 12, and FIG. 14 is a diagram showing the first method of shaping the laser beam. Figure 15 is a cross-sectional view taken along line A-A in Figure 14.
FIG. 16 is a sectional view taken along line B-B in FIG. 14, FIG. 17 is a diagram explaining the second method of shaping the laser beam, and FIG. FIG. 19 is a sectional view taken along line DD in FIG. 17.

First, in FIG. 12, 1 is a magneto-optical disk, 2 is a laser diode that emits a laser beam with an elliptical light intensity distribution, and is arranged so that the long direction of the ellipse coincides with the direction perpendicular to the plane of the drawing. 3 is a collimator lens that converts the light beam from the laser diode 2 into a parallel light beam; 4 is a shaping prism that shapes the laser beam with an elliptical cross section emitted from the laser diode 2 into a laser beam with a substantially circular cross section; and 5 is an incident light beam. A beam splitter 6 that divides the light beam into two is an objective lens that is driven in the direction of the magneto-optical disk 1 by a lens actuator and forms an image of the light beam from the beam splitter 5 on the magneto-optical disk 1 . 8 is a half-wave plate that provides a phase difference of 180' to the laser beam separated by the beam splitter 5; 9 is a condenser lens that condenses the laser beam emitted from the half-wave plate 8; and 10 is a condenser lens 9 that condenses the laser beam. A polarizing beam splitter that splits the emitted laser beam into two polarized components, 11 a two-split photodetector on which the laser beam of one of the split polarized components is focused, and 12 a laser that is the other split polarized component. The cylindrical lens 13 acts as a lens for light in only one direction, and is a four-divided photodetector on which the laser light emitted from the cylindrical lens 12 is focused.

Next, the operation of the above configuration will be explained. laser diode 2
The laser beam emitted from the collimator lens 3 converts the laser beam into a parallel beam of light and enters the beam splitter 5. Then, an image is formed on the magneto-optical disk 1 via the objective lens 6. The reflected light from the magneto-optical disk 1 is separated by a beam splitter 5 and enters a half-wave plate 8. Here, the polarization direction is adjusted, and then the light is condensed by the condenser lens 9. The laser beam focused by the condensing lens 9 is split into two polarized components by the polarizing beam splitter 10. The laser light of one of the divided polarized components is focused on the two-divided photodetector 11 . Further, the laser light of the other divided polarized component passes through the cylindrical lens 12 and is focused on the four-divided photodetector 13 .

The tracking error signal (TE) is generated using the push-pull method using the output signal of the 2-split photodetector 11, and the focus error signal (FE) is generated using the output signal of the 4-split photodetector 13 using the astigmatism method. In the aberration method, the information reproduction signal (RF) is obtained by the difference between the output signals of the two photodetectors 11 and 13, respectively.

Here, beam shaping will be explained using FIGS. 13 to 19.

In FIG. 13, 2a is a laser chip of the laser diode 2. In FIG. The laser beam emitted from this laser chip 2a has anisotropy, and generally has an elliptical light intensity distribution in a plane (xy plane) perpendicular to the direction of travel of the laser beam (two-axis direction). There is.

If this laser beam is focused directly onto the magneto-optical disk 1 through the objective lens 6, the focused spot will also be elliptical, and the laser beam may hit an adjacent track that should not be illuminated, or a spot may appear in the longitudinal direction of the bit. As a result, the C/N ratio of the reproduced signal deteriorates. This also applies during recording.

Therefore, beam shaping is generally performed to make the light intensity distribution of the laser beam closer to a circular shape. The first part of this beam shaping
As a method, there is a method shown in FIG. 14.15
is a cylindrical lens that acts as a lens in only one direction. With this configuration, the cross-sectional shape on the incident side is elliptical (see FIG. 15), but the cross-sectional shape on the exit side is circular (see FIG. 16). However, it is difficult to polish a cylindrical lens with a good surface area, and it is also difficult to measure the surface area, so a second method using a shaping prism 4 shown in FIG. 17 is often used.

With such a configuration, the cross-sectional shape on the incident side is elliptical (see FIG. 18), but the cross-sectional shape on the exit side is circular (see FIG. 19).

(Problem to be Solved by the Invention) In the conventional example of the above configuration, in addition to the shaping prism 4,
A beam splitter 5 and a polarizing beam splitter 10 are required, and there are the following problems.

■The size of the optical pickup increases.

■There are many parts, and the optical axis and angle adjustment of each part is complicated.

■The mass of the optical pickup becomes heavy, making it difficult to shorten access time.

The present invention has been made in view of the above problems, and its purpose is to provide an optical head that has a small number of parts, is easy to assemble, is small and lightweight, and can shorten head access time. It's about doing.

(Means for Solving the Problems) The invention of claim 1 which solves the above problems includes: a laser diode that emits a laser beam; a means for providing a phase difference of 180° to the laser beam emitted from the laser diode; an objective lens that focuses a laser beam on a magnetic recording medium; a first surface that shapes the laser beam; the laser beam is emitted to the magneto-optical recording medium through the objective lens, and is reflected from the magneto-optical recording medium; a second surface on which light enters through the objective lens; after entering the second surface, the first polarized component of the laser beam reflected by the first surface is transmitted; A prism having a third surface 9 that reflects a polarized light component and a fourth surface that transmits a second polarized light component reflected by the third surface, and detects the laser beam that has passed through the third surface of the prism. and a second detection section that detects the laser beam transmitted through the fourth surface of the prism.

According to a second aspect of the invention, in the first aspect of the invention, the third surface and the second surface of the prism are the same surface.

According to a third aspect of the present invention, in the first aspect of the present invention, the fourth surface and the second surface of the prism are the same surface.

The invention of claim 4 is defined as claim 1. In the invention according to claim 2 or 3, the first and second detecting sections have a six-divided configuration in which the magneto-optical disk is divided into two in the radial direction and three in the track direction.

In a fifth aspect of the invention, in the fourth aspect of the invention, the emission angles of the respective laser beams transmitted from the third surface and the fourth surface of the prism are equal to each other.

The invention according to claim 6 includes a laser diode that emits a laser beam, and a laser beam emitted from the laser diode that
means for providing a phase difference of °; an objective lens for focusing the laser beam on the magneto-optical recording medium; a first surface for shaping the laser beam; the laser beam is emitted to the magneto-optical recording medium through the objective lens; and a second surface on which the reflected light from the magneto-optical recording medium enters through the objective lens, and a predetermined polarized light of the laser light reflected from the first surface after being incident on the second surface. The prism includes a prism having a third surface through which only the component passes through, and a detection section that detects the laser beam transmitted through the third surface.

(Function) In the optical pickup according to the inventions of claims 1 to 5, the laser light emitted from the laser diode has an angle of 180@
A phase difference of 180° is provided by means for providing a phase difference of 1. incident on the prism.

The first surface of this prism shapes the laser beam, and the second surface
Emits from the surface. The emitted laser beam is focused on the magneto-optical recording medium via the objective lens, and the reflected laser beam is incident on the second surface. After being incident on the second surface, the first polarized component of the laser beam reflected on the first surface is transmitted through the third surface and detected by the first detection section. The second reflected from the third surface
The polarized light component is transmitted through the fourth surface and detected by the second detection section.

Further, in the optical pickup according to the sixth aspect of the invention, the laser light emitted from the laser diode is provided with a phase difference of 180' by means for providing a phase difference of 180°, and then enters the prism. The laser beam is shaped by the first surface of the prism and exits from the second surface. The emitted laser beam is focused on the magneto-optical recording medium via the objective lens,
The reflected laser light is incident on the second surface. After being incident on the second surface, only a predetermined polarized component of the laser beam reflected on the first surface is transmitted through the third surface and detected by the detection section.

(Example) Next, the present invention will be explained in detail using the drawings.

FIG. 1 is a configuration diagram illustrating an embodiment of the invention of claim 1;
Figure 2 is a configuration diagram showing an example of the beam spot on the first photodetector in Figure 1, Figure 3 is a configuration diagram showing an example of the beam spot on the second photodetector in Figure 1, and Figure 4. is a block diagram for generating various signals in FIG. 1, FIG. 5 is a block diagram for explaining one embodiment of the invention of claim 2, and FIG. 6 is a block diagram for explaining a first embodiment of the invention of claim 3. The configuration diagram, FIG. 7, is the second aspect of the invention of claim 3.
FIG. 8 is a configuration diagram explaining an embodiment of the invention of claim 4, and FIG. 9 is a configuration diagram showing an example of a beam spot on the first photodetector in FIG. 8. , FIG. 10 is a configuration diagram showing an example of a beam spot on the second photodetector in FIG. 8, and FIG. 11 is a configuration diagram illustrating an embodiment of the invention according to claim 5.

First, an embodiment of the invention according to claim 1 will be described using FIGS. 1 to 4. FIG. In these figures, 21 is a magneto-optical disk, 22 is a laser diode that emits a laser beam with an elliptical light intensity distribution, and is arranged so that the major axis of the ellipse coincides with the direction perpendicular to the plane of the drawing, and 23 2 is a collimator lens that converts the light beam from the laser diode 22 into a parallel light beam; 24 is a half-wave plate that provides a phase difference of 180'' to the laser beam so that the polarization direction is 45'' with respect to the plane of the paper;
Reference numeral 5 denotes an objective lens that focuses the laser beam on the magneto-optical disk 21.

26 is a prismatic prism. This prism 26 has a shaping function of making the intensity distribution of the incident laser light closer to a circular shape, and includes a first prism 26a provided with a half mirror surface;
A second surface 26b, onto which the laser beam transmitted through the first surface 26a is emitted to the magneto-optical disk 21 via the objective lens 25, and onto which reflected light from the magneto-optical disk 21 is incident via the objective lens 25; Polarized light transmittance (T(p)) is approximately 100%, and S polarized light reflectance (R(s)) is approximately 100%.
The third surface 26c is a polarizing beam splitter surface coated with a dielectric multilayer film of 30%, and the third surface 26c is where the laser beam reflected from the first surface 26a is guided, and the S-polarized light transmittance (T (s)
) is approximately 100% polarization beam splitter surface, and the third
It has a fourth surface 26d into which the S-polarized light component of the lens laser beam reflected by the surface 26c is incident.

27 is a condenser lens that condenses the P-polarized light component that has passed through the third element 26c of the prism 26, and 28 is a cylindrical lens that acts as a lens in only one direction, and these two form an astigmatic optical system. There is.

29 is a first photodetector on which the P-polarized light component emitted from the cylindrical lens 28 is collected. As shown in FIG. 2, this first photodetector 29 has a four-part structure. 30 is a second photodetector where the S-polarized light component transmitted through the fourth surface 26d of the prism 26 is collected.

As shown in FIG. 3, this second photodetector 30 has a two-part structure.

Next, the operation of the above configuration will be explained. laser diode 2
The laser beam emitted from the laser beam 2 is made into a parallel beam by the collimator lens 23 and enters the half-wave plate 24 . Here, the laser beam is provided with a phase difference of 180'', and the polarization direction is 45 degrees with respect to the plane of the paper.Then, the laser beam is incident on the first surface 26a of the prism 26, where the beam is shaped, and The emitted laser beam is emitted from the objective lens 26b.
5 onto the magneto-optical disk 21.

Here, the laser beam is subjected to the Kerr effect, and the polarization direction undergoes Kerr rotation, resulting in an angle of 45°±θk (θ,−Kerr rotation angle) with respect to the plane of the paper.

The reflected laser beam passes through the objective lens 25. The light is guided to the first surface 26a through the second surface 26b of the prism 26, reflected there, and guided to the third surface 26c.

Substantially only the P-polarized component of the laser beam is transmitted through the third surface 26c, and the S-polarized component is reflected. The P-polarized component of the transmitted laser light is collected by a condenser lens 279, which is an astigmatism optical system.
An image is formed on a first photodetector 29 via a cylindrical lens 28.

On the other hand, the S-polarized light component reflected by the third surface 26c is guided to the fourth surface 26d, transmits therethrough, and forms an image on the second photodetector 30.

The first photodetector 29 at this time. The beam spot shape on the second photodetector 30 is shown in FIGS. 2 and 3. In addition, in Fig. 2, ■ indicates the objective lens 25.
indicates a case where the lens is too close to the magneto-optical disk 21, a symbol (■) indicates a case where the lens is at the in-focus position, and a symbol (■) indicates a case where the lens is too far away. Then, signals a to d are output from each of the two divided surfaces of the first photodetector 30, and signals p and q are output from each divided surface of the second photodetector 30. Further, in FIG. 1, the shaded area indicates the vicinity of the center of the first-order diffracted light distribution area by the group of magneto-optical disks.

Next, processing of signals from these photodetectors 29 and 30 will be explained using FIG. 4. In this figure, 3
1 is a first stage amplifier, 32 is an addition amplifier, and 33 is a differential amplifier. Using such a circuit, the following calculations are performed to generate a focus error signal (FE), a rack error signal (TE), and an information reproduction signal (RF).

FE-(a+c)-(b+d) TE-p-q RF-(a+b+c+d)-(p+q) Note that 34 is a variable resistor that generates a predetermined voltage from the power supply voltage Vcc,
Calibration is performed so that FE-0 is obtained during focusing.

According to the above configuration, the prism 26 has a beam shaping function, a beam splitter function, and a polarizing beam splitter function. Therefore, the following effects can be obtained.

■The size of the optical pickup becomes smaller.

■The number of parts is reduced, making optical axis and angle adjustment easier.

■The mass of the optical pickup is lighter, reducing access time.

Note that the present invention is not limited to the above embodiments.

In the above embodiment, the third surface 26c of the prism 26
is a polarizing beam splitter surface coated with a dielectric multilayer film, but the incident angle of the laser beam on the third surface 26c is determined by the Brewster angle θa (-ta Milo-(1/n)
, n ; optical refractive index of the prism 26), the laser beam guided to the first photodetector 29 has a P-polarized component as a main component, and
Since the laser beam guided to zero has an S polarization component, a similar effect can be obtained.

Next, an embodiment of the invention according to claim 2 will be described using FIG. Incidentally, the same parts as those in the invention of claim 1 are given the same reference numerals, and their explanation will be omitted.

In the figure, 36 is a prismatic prism.

This prism 36 has a shaping function that makes the intensity distribution of the incident laser light closer to a circular shape, and the first prism 36 is a half-mirror surface.
The laser light that has passed through the surface 36a and the tenth surface 36a is emitted to the magneto-optical disk 21 via the objective lens 25, and the reflected light from the magneto-optical disk 21 is reflected from the objective lens 25.
The second surface 36b enters through the P-polarized light transmittance (T
(p)) is approximately 100%, and the S-polarized light reflectance (R(s)
) is a polarizing beam splitter surface with approximately 100% dielectric multilayer coating, and the laser beam reflected by the first layer 36a is guided to the third surface formed on the same surface as the second layer 36b. 36c is a polarizing beam splitter surface with an S-polarized light transmittance (T(s)) of approximately 100%, and the fourth surface is where the S-polarized component of the laser beam reflected by 36c is incident.
It has a surface 36d.

According to such a configuration, in addition to the effect of the invention of claim 1,
Since the shape of the prism 36 is simpler than the shape of the prism 26 in the invention according to claim 1, the cost can be reduced.

Next, the invention of claim 3 will be explained in detail using FIGS. 6 and 7. Note that the same parts as those in the first invention are given the same reference numerals, and their explanation will be omitted.

First, in FIG. 6 showing the first embodiment, 46 is a prismatic prism. This prism 46 has a shaping function that makes the intensity distribution of the incident laser light approximate to a circular shape. A second surface 46b on which the light emitted to the magnetic disk 21 and reflected from the magneto-optical disk 21 enters through the objective lens 25.
, the P polarized light transmittance (T (p)) is approximately 100%, and S
The third surface 4 is a polarizing beam splitter surface formed by a dielectric multilayer coating with a polarization reflectance (R(8)) of approximately 100%, and to which the laser beam reflected by the first surface 46a is guided.
6c is a polarizing beam splitter surface with an S-polarized light transmittance (T(S)) of approximately 100%, on which the S-polarized component of the laser beam reflected by the third surface 46c is incident, and is the same as the second surface 46b. and a fourth surface 46d formed on the surface.

According to such a configuration, in addition to the effect of the invention of claim 1,
The shape of the prism 46 is simpler than the shape of the prism 26 in the invention according to claim 1, and the cost can be reduced.

Next, in FIG. 7 showing the second embodiment, 56 is a prismatic prism. This prism 56 has a shaping function that makes the intensity distribution of the incident laser light approximate to a circular shape. A second surface 56b on which the light emitted to the magnetic disk 21 and reflected from the magneto-optical disk 21 enters through the objective lens 25.
, the P polarized light transmittance (T (p)) is approximately 100%, and S
The third surface 56 is a polarizing beam splitter surface formed by a dielectric multilayer coating with a polarization reflectance (R(s)) of approximately 100%, and the laser beam reflected from the first surface 56a is guided.
6c is a polarizing beam splitter surface with an S-polarized light transmittance (T(S)) of approximately 100%, on which the S-polarized component of the laser beam reflected by the third surface 56c is incident, and is the same as the second surface 56b. It has a fourth member 56d formed on the surface. Here, the difference from the first embodiment is that the S-polarized component of the laser beam reflected by the third surface 56c intersects with the laser beam directed toward the objective lens 25, so that the fourth surface and the second surface are Face 5
The position of 6b is reversed.

With such a configuration, in addition to the effect of the invention of claim 1, the shape of the prism 56 is simpler than the shape of the prism 26 in the invention of claim 1, and the cost can be reduced.

Next, an embodiment of the invention according to claim 4 will be described using FIGS. 8 to 10. In these figures, the same parts as in FIG. 7 showing the second embodiment of claim 3 are designated by the same reference numerals, and their explanation will be omitted.

In the figure, 57 is a first photodetector having a six-segment configuration in which the magneto-optical disk 21 is divided into two in the radial direction and three in the track direction, as shown in FIG. 9, and 58 is a first photodetector.
As shown in FIG.
This is a second photodetector having a six-segment configuration in which the photodetector is divided into three in the track direction. Note that the shaded area indicates the vicinity of the center of the first-order diffracted light area by the group of magneto-optical disks 21. Furthermore, as shown in FIG. 7, the condenser lens 27 and cylindrical lens 28, which are astigmatic optical systems, are not used.

In such a configuration, the outputs of each divided plane of the first photodetector 57 are A-F, and the outputs of the second photodetector 58 are
When the output of each divided plane is P-U, the focus error signal (FE) is the first. Second photodetector 57.5
By changing the beam spot size on 8 depending on the focusing state, the tracking error signal (
The information reproduction signal (RF) is transmitted by the push-pull method, and the information reproduction signal (RF) is transmitted by the first TE). Second photodetector 57°58
can be obtained from the difference between the output signals as follows.

FE-((B+E)+ (Q1T)1 - ((A+C+D+F)+ (P+R+S+U))
TE import ((A+B+C)+ (P+Q+R))-f
(D+E+F)-1-(S+T+U))RF-(A+B
+C+D+E+F) -(P+Q+R+S+T+U) According to the above configuration, an optical element for detecting a focus error such as an astigmatism optical system is not required, so that the optical pickup is further improved than the inventions of claims 1 to 3. ■The number of parts is reduced, making it easier to adjust the optical axis and angle.■The mass of the optical pickup is lighter, reducing access time.

Note that the present invention is not limited to the above embodiments. Although the above embodiment was applied to the configuration shown in FIG. 7, it goes without saying that it can also be applied to the configurations shown in FIGS. 1 to 6.

Next, an embodiment of the invention according to claim 5 will be described using FIG. 11. In the figure, the same parts as in FIG. 8 showing the embodiment of claim 4 are given the same reference numerals, and their explanation will be omitted.

The difference from FIG. 8 is a prism 66.

This prism 66 has a shaping function of making the intensity distribution of the incident laser light closer to a circular shape, and has a first half-mirror surface.
The laser beam transmitted through the second surface 66a and the first surface 66a is emitted to the magneto-optical disk 21 via the objective lens 25, and the reflected light from the magneto-optical disk 21 is emitted from the objective lens 25.
The second surface 66b is incident through the P-polarized light transmittance (T
(p)) is approximately 100%, and the S-polarized light reflectance (R(s)
) is the polarizing beam splitter surface formed by approximately 100% dielectric multilayer coating, and the third surface 66c to which the laser beam reflected by the first surface 66a is guided, and the S-polarized light transmittance (T(s)) This is an approximately 1,00% polarization beam splitter surface, and the S-polarized component of the laser beam reflected from the third surface 66c enters the fourth surface 66d, which is formed on the same plane as the second surface 66b. have.

Further, in this embodiment, the emission angle θ from the prism 66 of the luminous flux toward the first photodetector 67.

The shape of the prism 66 is determined so that the output angle θ5 of the light flux from the prism 66 toward the second photodetector 68 is equal.

That is, in FIG. 11, when the laser beam that passes through the objective lens 25 and enters the second surface 66b is orthogonal to the second surface 66b, when the relationship of 4θ, +3θ2−360@ holds, both emission angles θ1 ．． θ2 becomes equal. The output angle at this time is θ, -05 -5in-'(nsin(2θ1+2θ2-1110'
)1n; given by the optical refractive index of the prism 66 with respect to air.

By adopting such a configuration, in addition to the invention of claim 4, the beam spot shapes on the first photodetector 67 and the second photodetector 68 are made equal; Any shape can be used. Therefore, it is not only easy to adjust the electric circuit, but also advantageous in terms of cost.

Note that the present invention is not limited to the above embodiments.

In the above embodiment, the collimator lens 23 was used to convert the laser beam emitted from the laser diode 22 into a parallel beam. A similar effect can be obtained by arranging each photodetector 6768 so that the optical path lengths of the photodetectors 6768 are equal.

In the embodiment described above, the first. The second photodetector was used to obtain a focus error signal, a tracking error signal, and an information reproduction signal. However, a focus error signal, a tracking error signal, and an information reproduction signal can be obtained with just one photodetector. Here, the invention of claim 6 will be explained.

In the embodiment of the present invention, for example, in FIG. 8, the second photodetector 58 is simply not provided, so the drawing is omitted. In this case, if the output of each divided plane of the first photodetector 57 is A-F, the focus error signal (FE)
, ) Rack error signal (TE) and information reproduction signal (RF) are obtained as follows.

FE= (B+E)-(A0C+D+F)TE-(A0B+C)-(D+E+F)RF-(A+B+C+D10E
+F) According to the above configuration, an optical element for detecting a focus error such as an astigmatism optical system is not required, and furthermore, only one photodetector is required, so compared to the inventions of claims 1 to 5. (1) The size of the optical pickup is smaller, (2) the number of parts is reduced, making it easier to adjust the optical axis and angle, (2) the mass of the optical pickup is lighter, and access time can be shortened.

Furthermore, in the above embodiment, the Kerr effect can be most effectively suppressed by adjusting the rotation of the half-wave plate 24 as appropriate so that the polarization plane of the laser beam incident on the third surface 56c forms an angle of 45° with respect to the plane of the paper. can be detected.

(Effects of the Invention) As described above, according to the present invention, the following effects can be obtained.

According to the invention of claim 1, a laser diode that emits a laser beam, a means for providing a phase difference of 180' to the laser beam emitted from the laser diode, and an objective lens that focuses the laser beam on a magneto-optical recording medium. , a first surface for shaping the laser beam, a second surface on which the laser beam is emitted to the magneto-optical recording medium via the objective lens, and a reflected light from the magneto-optical recording medium is incident via the objective lens. side.

a third surface that transmits the first polarized component of the laser beam reflected by the first surface after being incident on the second surface and reflects the second polarized component; a prism having a fourth surface through which the second polarized light component reflected by the surface is transmitted; and a first surface that detects the laser beam transmitted through the third surface of the prism.
By including a detection section and a second detection section that detects the laser beam transmitted through the fourth surface of the prism, the number of parts is small, assembly is easy, and the device can be made smaller and lighter. , it is possible to realize an optical head that can shorten head access time.

According to the invention of claim 2, in addition to the effect of the invention of claim 1, by making the third surface and the second surface of the prism the same surface in the invention of claim 1, the shape of the prism can be changed. It can be done easily and costs can be reduced.

The invention according to claim 3 is the invention according to claim 1, by making the fourth surface and the second surface of the prism the same surface,
In addition to the effect of the invention of claim 1, the prism shape can be simplified and the cost can be reduced.

The invention of claim 4 is defined as claim 1. In the invention according to claim 2 or claim 3, the first and second detection sections have a six-divided configuration in which the magneto-optical disk is divided into two in the radial direction and three in the track direction. In addition to the effects of inventions 3 to 3, the size of the optical pickup is reduced, the number of parts is reduced, the optical axis and angle adjustment is simplified, the mass of the optical pickup is reduced, and access time can be shortened. .

In the invention of claim 5, in addition to the invention of claim 4, the emission angles of the respective laser beams transmitted from the third surface and the fourth surface of the prism are equal to each other. , the beam spot shapes on the first photodetector and the second photodetector are equal,
The first photodetector and the second photodetector can have the same shape. Therefore, it is not only easy to adjust the electric circuit, but also advantageous in terms of cost.

In the invention of claim 6, there is provided a laser diode that emits a laser beam, a means for providing a phase difference of 180'' to the laser beam emitted from the laser diode, an objective lens that focuses the laser beam on a magneto-optical recording medium, and a laser diode that emits a laser beam. a first surface that shapes light; a second surface on which the laser beam is emitted to the magneto-optical recording medium via the objective lens, and on which reflected light from the magneto-optical recording medium is incident; the second surface; a prism having a third surface through which only a predetermined polarized component of the laser beam reflected by the first surface after being incident on the prism is transmitted; and a detection unit that detects the laser beam transmitted through the third surface. In addition to the effects of the inventions of claims 1 to 4,
Furthermore, the size of the optical pickup is reduced, the number of parts is reduced, the optical axis and angle can be easily adjusted, the mass of the optical pickup is reduced, and access time can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram illustrating an embodiment of the invention of claim 1;
FIG. 2 is a configuration diagram showing an example of the beam spot on the first photodetector in FIG. 1, FIG. 3 is a configuration diagram showing an example of the beam spot on the second photodetector in FIG. 1, and FIG. FIG. 1 is a block diagram for generating various signals, FIG. 5 is a configuration diagram explaining an embodiment of the invention of claim 2, and FIG. 6 is a configuration diagram explaining a first embodiment of the invention of claim 3. 7 is a block diagram explaining a second embodiment of the invention of claim 3, FIG. 8 is a block diagram explaining one embodiment of the invention of claim 4, and FIG. 9 is a block diagram explaining a second embodiment of the invention of claim 4. FIG. 10 is a configuration diagram showing an example of the beam spot on the first photodetector in FIG. 8, FIG. 11 is a configuration diagram showing an example of the beam spot on the second photodetector in FIG. Configuration diagram explaining one embodiment, No. 12
The figure is a block diagram showing an example of the conventional method, FIG. 13 is a diagram explaining the anisotropy of the laser beam emitted from the laser diode in FIG. 12, and FIG. 14 is a diagram showing the first method of shaping the laser beam.
Figure 15 is a diagram explaining the method of A- in Figure 14.
A sectional view, FIG. 16 is a BB sectional view in FIG. 14,
Fig. 17 is a diagram explaining the second method of shaping the laser beam, Fig. 18 is a cross-sectional view taken along the line C-C in Fig. 17, and Fig. 19 is a cross-sectional view taken along the line D-D in Fig. 17. . In these figures, 1.21... magneto-optical disk 2.22... laser diode 3.23... collimator lens 4... shaping prism 5... beam splitter 6.25... objective lens 7... Lens actuator 8.24... Half-wave plate 9.27... Condensing lens 10... Polarizing beam splitter 11.13... Photodetector 12.28... Cylindrical lens 26. 36, 46, 56.66...prism 26a
, 36a, 46a, 56a, 66a...first surface 26b, 36b, 46b, 56b, 66b...second surface 26c, 36c, 46c, 56c, 66c
...Third surface 26d, 36d, 46d, 56d, 66d...Fourth surface 29.57...First photodetector 30.58.
...Second photodetector 31...First stage amplifier
32...Additional amplifier 33...Differential amplifier

Claims (6)

[Claims] (1) A laser diode that emits a laser beam, a means for creating a 180° phase difference in the laser beam emitted from the laser diode, an objective lens that focuses the laser beam on a magneto-optical recording medium, and a shaper that shapes the laser beam. a first surface, a second surface on which the laser beam is emitted to the magneto-optical recording medium via the objective lens, and a second surface on which reflected light from the magneto-optical recording medium is incident via the objective lens; After being incident on the surface of the laser beam, the first polarized component of the laser beam reflected by the first surface is transmitted, and the second polarized component is reflected by the third surface, and reflected by the third surface. a prism having a fourth surface through which the second polarized light component passes through; a first detection unit that detects the laser light that has passed through the third surface of the prism; An optical pickup comprising: a second detection section that detects laser light. (2) The optical pickup according to claim 1, wherein the third surface and the second surface of the prism are the same surface. (3) The optical pickup according to claim 1, wherein the fourth surface and the second surface of the prism are the same surface. (4) The first and second detecting sections have a six-divided configuration in which the magneto-optical disk is divided into two in the radial direction and three in the track direction. optical pickup. (5) The optical pickup according to claim 4, wherein the emission angles of the respective laser beams transmitted from the third surface and the fourth surface of the prism are equal to each other. (6) A laser diode that emits a laser beam, a means for providing a 180° phase difference to the laser beam emitted from the laser diode, an objective lens that focuses the laser beam on a magneto-optical recording medium, and a shaper that shapes the laser beam. a first surface, a second surface through which the laser beam is emitted to the magneto-optical recording medium via the objective lens, and a reflected light from the recording medium is incident through the objective lens; a prism having a third surface through which only a predetermined polarized component of the laser beam reflected by the first surface after being incident on the prism is transmitted; and a detection unit that detects the laser beam transmitted through the third surface. An optical pickup characterized by comprising: