JPS6182344A - Optical pickup - 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 the Invention The present invention relates to an optical pickup having various optical components for optically recording and reproducing data on and from a recording medium.

BACKGROUND OF THE INVENTION FIG. 8 shows a conventional example of the above-mentioned optical pickup. In this optical pickup 1, a beam 3 emitted from a light source 2 such as a laser diode is transmitted through a beam block 4, and after being made into a parallel beam by a collimator lens 5, the beam 3 is sent to a recording medium 71 such as an optical disk by an optical lens 6. − converges to −.

The heels 1 and 3 reflected by the recording medium 7 are made into parallel beams by the condenser lens 6, converged by the collimator lens 5, and reflected by the beam splinter 4, and then used for the detection of the nail error by the astigmatism method. The light enters a photodetector 9 such as a photodiode through a semicircular cylinder 8 .

Problems to be Solved by the Invention However, the optical pickup 1 as described above is expensive due to the large number of optical components. An aspherical lens or bologram element with different focal lengths on the object space side and image space side,
Although the collimator lens 5 and the condensing lens 6 can be replaced, the number of parts will only decrease by one in that case.

In addition, the optical pickup 1 as a whole is heavy due to the large number of optical parts, and the drive section of the optical pickup 1 has a double 9fC, which also increases the cost.

Means for Solving Problems The optical pink amplifier according to the present invention includes a light beam tA2, a hologram element 11, and a photodetector 9, respectively, and the beam 3 from the light source 2 is directed to a predetermined position by the hologram element 11. At the same time, the beam 3 from this predetermined position is converged onto the photodetector 9 by the hologram element 11.

Operation In the optical pickup according to the present invention, a single hologram element 11 has the function of converging the beam 3 from the light source 2 on a predetermined position and the function of converging the beam 3 from the predetermined position on the photodetector 9. are doing.

EXAMPLES Hereinafter, examples and specific examples of the present invention will be described with reference to FIGS. 1 to 7.

FIG. 1 shows one embodiment of the present invention, and first the principle of this embodiment will be explained with reference to FIGS. 2 and 3.

As shown in Figure 2, recording light is applied to the dry plate 11 from the 0 and a directions.
Then, as shown in FIG. 2B, the recording light is made incident on the dry plate 11 again from the 0 and b directions to record another phase volume hologram l. When recording, that is, double exposing the dry plate 11, two diffraction gratings are formed on the dry plate 11.

Then, as shown in Figure 2C, the reproduction light is applied to the dry plate 1 from the 0 direction.
1, diffraction occurs in both directions a and b.

In addition, as shown in the second diagram, the reproduction light is applied to the dry plate 11 from the direction a.
If it is made incident on , this reproduced light will be diffracted in the O direction, but
This diffracted light is further passed through another diffraction grating.
It is also diffracted in this direction. In this case, the diffraction intensity in the a, b and 0 directions can be arbitrarily changed by changing the phase modulation degree of the two diffraction gratings, and the diffraction intensity in the b direction can be changed arbitrarily by changing the degree of phase modulation of the two diffraction gratings.
' OO% diffraction can also be performed.

Therefore, as shown in FIG. 3, a hologram is recorded by interfering with the first recording light 12 that diverges toward the dry plate 11 and the second recording light 13 that converges toward the dry plate 11.
Immediately after that, the third recording light 1 diverges toward the dry plate 11.
4 and the second recording light 13 mentioned above to record another hologram, as shown in FIG. The beam 3 from the recording medium 7 can be focused on the recording medium 7 and the beam 3 reflected by this recording medium 7 can be focused on the photodetector 9.

Note that when detecting focus errors using the astigmatism method, the beam 3 converging on the photodetector 9 can be
can include astigmatism.

In addition, in the double recording of the hologram described above, the recording light 13
are used in common, but recording light beams 12 and 14 may also be used in common. Furthermore, in the double recording of the hologram described above, one of the recording beams 12 to 14 is used in common and the hologram and ram are recorded using any two recording beams, but three recording beams 12 to 14 are simultaneously used to mutually Let me interfere, Hologram J.
may be recorded at one time.

In such a light pickup 15, 50% of the beam 3 emitted from the light source 2 and incident on the dry plate 11 is diffracted so as to converge on the recording medium 7, is reflected on the recording medium 7, and is incident on the dry plate 11. 50% of the beam 3 is diffracted so as to converge on the photodetector 9, and the utilization efficiency of the beam 3 is 25%.
%, this utilization efficiency is theoretically highest.

However, within the range that can be detected by the photodetector 9,
The utilization efficiency of beam 3 may be lower than 25%. In the case of double exposure, the utilization efficiency of the beam 3 is the same regardless of which of the three recording beams 12 to 14 is used in common.

When the dry plate 11 is simultaneously exposed to the three recording beams 12 to 14, the diffraction index of each of the above becomes 479, and the utilization efficiency of the beam 3 is 16/8119. ．． This utilization efficiency is theoretically highest when it is 8%.

As described above, in the optical pickup 15 of this embodiment, the dry plate 1, which is a borodulum element on which bolograms are recorded double,
1, the number of optical parts is very small, but if the light source 2 and photodetector 9 are integrally formed on a single wafer, the number of parts can be further reduced. can.

FIG. 4 shows a first specific example of the present invention.

In this first specific example, a package 17 having terminals 16
A light source 2 and a photodetector 9 are attached to the P1 to the sink 18 within. The package 17 is attached to one end of the lens barrel 21, and the dry plate 11 is installed at the other end of the lens barrel 21.

The lens barrel 21 is placed inside an outer frame 26 via a leaf spring 24 and a membrane damper 25, with a focusing coil 22 and a tracking coil 23 wound around it. An annular focusing magnet 27 is provided on the inner surface of the outer frame 26.
, focusing yokes 28, 29, and trunking magnets 31 are attached.

If the focus error signal is detected by a change in the spot size of the beam 3 on the photodetector 9, the fifth
As shown in the figure, the photodetector 9 is connected to six photodetectors Δ1 to B1.
It can be configured by

According to the photodetector 9 in FIG. 5, the focus error Shingetsuba (
A++13+ →-A3→-133)-(Δ282)
It can be found from In this case, the trunking error signal is calculated using the push-pull method (△1 +Δ2+Δ]
)−(n+1−B2+83).

When detecting the focus error signal by the astigmatism method, the photodetector 9 is connected to four photodetectors A as shown in FIG.
-D allows for good configuration deviation.

The lens barrel 21 is moved up and down in the direction of arrow F based on the claw error signal, and the leaf spring 2 is moved up and down based on the tracking error signal.
4 as a fulcrum and is swung in the direction of arrow T.

As described above, according to the present invention, the number of optical parts is extremely small, so that the lens barrel 2 can be shifted to be extremely lightweight, less than 1g R1i. Therefore, since it is possible to easily design a drive unit that moves the entire lens barrel 21, a drive unit that moves the lens barrel 21 in parallel in both the focusing direction and the I-racking direction may be used.

In this first specific example, the recording beams 12 and 1 in FIG.
Both numerical apertures of 4 and 4 are set to 0.1. For this reason, since the light source 2 and the photodetector 9 can be placed close to each other, they can be housed in a common package 17 as described above, reducing the cost of the package. The aberration of the incident beam 3 can also be reduced. Note that the numerical aperture of the recording light 13 is 0.47.

FIG. 7 shows a second specific example of the present invention.

In this second specific example, focus adjustment is performed by sliding the block 32 to which the lens barrel 21 is attached in the direction of the rotation axis 33.
Tracking adjustment is performed by rotating it around 3.

In this second specific example, the numerical aperture of the recording light 12 in FIG. 2 is 0.07, and the numerical aperture of the recording light 14 is 0.15. For this reason, the light source 2 and the photodetector 9 cannot be housed in a common package 17 as in the first specific example.

However, from the light lylλ2 to the dry plate 11)1--m(
Since the numerical aperture of the beam 3 is large and the proportion of the beam 3 that does not enter the dry plate 11 is small, the effectiveness of the beam 3 is high. Also, Hino heading from the recording medium 7 to the dry plate 11,
Compared to the numerical aperture of 3, the aperture of the beam 3 from the dry plate 11 to the photodetector 9! 1° (because it is very small, it goes to the photodetector 9), the imaging degree of 3 changes greatly even with a slight focus error, and the detection sensitivity of focus error is high.Moreover, the light 1'!, output The position of the container 9 is also easier to adjust compared to the first specific example.

In addition, in any of the above embodiments and specific examples, Bologura 1
A dry plate 11 is used as a recording medium for , and the dry plate 11 is heavily exposed to recording light beams 12 to 14. By developing 41 pieces, a Borodaram element is created. However, a bologram element may be created by joining a plurality of dry plates 11 on which vologram J, t7) of fit- is recorded. Alternatively, a borodulum element may be created by directly recording vologram l on the recording medium using a recording medium other than the dry plate 11 and a recording light such as an electron beam, without performing development.

Effects of the Invention As described above, in the optical pickup according to the present invention, the functions of converging the beam from the light source to a predetermined position and the function of converging the beam from the predetermined position to the photodetector are performed by a single Polodaram element. Therefore, the number of optical components can be reduced, and costs can be reduced.

Furthermore, since the number of optical parts is small, the entire optical pickup is light, and the drive unit for the optical pickup can be simple, which also reduces the cost of the optical pickup.

[Brief explanation of the drawing]

FIG. 1 is a side view showing one embodiment of the present invention, FIGS. 2 and 3 are side views for explaining the principle of one embodiment, and FIG. 4 is a side view showing a first specific example of the present invention. 5 is a plan view showing the photodetector used in the first specific example, and FIG. 6 is a side sectional view showing the photodetector used in the first specific example.
FIG. 7 is a plan view showing another photodetector used in the specific example, and a side sectional view not showing the second specific example of the present invention. FIG. 8 is a side view showing a conventional example of the present invention. In addition, in the symbols used in the drawings, 2---------- One light source 3---------- Beam 7-- Recording medium 9 --------
---------Photodetector] 1-----------Inui Jutan 15 =-----Optical pickup.

Claims (1)

[Claims] A light source, a hologram element, and a photodetector are respectively provided, and the beam from the light source is converged to a predetermined position by the hologram element, and the beam from the predetermined position is converged by the hologram element to the photodetector. Optical pickup.