JPH04113526A - Optical pickup - Google Patents

Abstract

PURPOSE:To eliminate the need for respectively controlling respective optical elements again in changing into a different polarizing direction by providing a supporting member, which can freely attachably/detachably install a 1/2 wavelength plate on the optical path, so as to change the polarizing direction of light. CONSTITUTION:Between a rising mirror 5 and a beam splitter 4, a pair of grooves 12 and 12 opposed to each other in parallel are provided so as to nearly orthogonally cross the optical path in between and to install an almost cubic rectangular holding plate 11 equipped with a 1/2 wavelength plate 11a. Namely, by providing several rectangular holding plates 11 equipped with the 1/2 wavelength plates 11a changed at arbitrary various polarizing angles, the polarizing angle of light irradiating a recording medium 8 can be controlled only by inserting or not inserting the rectangular holding plate 11 between the grooves 12 and 12 or mounting the rectangular holding plate 11 equipped with the 1/2 wavelength plate 11a to the grooves 12 and 12 while turning the plate to right and left by 90 deg.. Thus, it is not necessary to control the optical elements on the optical path again for changing the polarizing direction of light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical pickup used in equipment that optically records and reproduces information by irradiating a light spot onto a recording medium such as an optical disk.

[Conventional technology]

Conventionally, for example, as shown in FIG. 6, an optical pickup 20 is equipped with a semiconductor laser 21 as a light source, and the light emitted from the semiconductor laser 21 passes through a collimating lens 22 and becomes parallel light. The beam is shaped by a shaping prism 23. This beam-shaped light passes through the beam splitter 24, changes its optical path with the raising mirror 25, is focused by the objective lens 26, and is directed to the recording medium 27.
The light is focused on a predetermined position on the recording surface.

The reflected light from the recording medium 27 follows the optical path system described above in the opposite direction, and its optical path is changed by the beam splitter 24. This light passes through a condensing lens 28 and is condensed, and this condensed light is sent to a photodetector. 29, and is a signal containing various information.

In other words, in the above configuration, the information recorded on the recording medium 27, for example, an audio signal, is read by the signal detected by the photodetector 29, and the light is focused on the recording medium 27 by the detected signal. I am getting a servo signal to control it.

Incidentally, this servo signal is detected based on the two-dimensional shape of the light spot focused on the photodetector 29 and its light intensity distribution. Therefore, the recording medium 2
The two-dimensional shape of the light spot and its light intensity distribution change depending on the birefringence of the material of the recording medium 27 or the shape of the recording groove.
is influenced by the optical properties of Furthermore, for the same reason as above, the servo signal is also affected by the polarization direction of the light focused on the recording medium 27.

For these reasons, in the above description, the polarization direction of the light focused on the recording medium 27 is adjusted in order to obtain the optimum servo signal output. The polarization direction is adjusted by rotating the mounting direction of the semiconductor laser 21 with respect to the optical axis and changing the direction of the shaping prism 23 accordingly.

Furthermore, according to the polarization direction, the beam splitter 2
4. The photodetector 29 is also adjusted.

[Problems to be Solved by the Invention] However, in the above configuration, in each optical element of the optical path system whose polarization directions are once set to match each other so as to obtain an optimal servo signal, polarization directions different from those described above are generated. When changing the direction, it is necessary to readjust each optical element, which creates a problem in that the adjustment takes time.

[Means to solve the problem]

In order to solve the above problem, the optical pink-up according to claim 1 of the present invention is capable of changing the polarization direction of the light in an optical pickup that records and reproduces information by irradiating light onto a recording medium. As such, it is characterized by having a support member on which the 1/2 wavelength plate can be removably installed on the optical path.

In order to solve the above problem, an optical pickup according to claim 2 of the present invention is an optical pickup provided with an opening through which light that is irradiated onto and reflected on a recording medium is emitted and input. It has a support member on which a 1/2 wavelength plate can be detachably installed on the optical path so that the polarization direction of the 1/2 wave plate can be changed, and when the 1/2 wavelength plate is installed on the support member, The supporting member is characterized in that the supporting member is provided so that the wavelength plate closes the opening.

[For production]

According to the configuration according to the above claims 1 and 2,
By installing the 1/2 wavelength plate on the support member, the polarization direction of the light irradiated onto the recording medium can be changed. Therefore, it is possible to save the effort of readjusting the optical elements on the optical path in order to change the polarization direction of the light as in the conventional case.

[Embodiment 1] An embodiment of the optical pickup amplifier according to claim 1 of the invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 2, the optical pickup is equipped with a semiconductor laser l as a light source. Light emitted from this semiconductor laser 1 passes through a collimating lens 2 and becomes parallel light. This parallel light passes through a shaping prism 3 and a beam splitter 4 and enters a rising mirror 5. This incident light has an optical path changed by approximately 90 degrees by the reflecting surface of the rising mirror 5 and is emitted. This emitted light passes through the aperture 6 and enters the objective lens 7. This incident light is
The position of the objective lens 7 is controlled by an objective lens driving section (not shown), and the light is focused on a desired position on the recording medium 8.

The return light, which is the reflected light from the recording medium 8, follows the above-mentioned optical path in the reverse direction, is reflected by the beam splitter 4, and is sent to the photodetector 10 through the condenser lens 9, where it is detected.

This photodetector 10 detects a servo signal that controls the objective lens 7 in order to focus the light from the semiconductor laser 1 onto a desired position on the recording medium 8 via the objective lens 7, and detects the servo signal on the recording medium 8. Information contained in the returned light, such as audio and video signals, is detected.

As shown in FIG. 1, which is an enlarged view of section A in FIG.
In addition, a pair of parallel grooves (supporting members) 12 are provided, respectively, so that a substantially square rectangular holding plate provided with a 1/2 wavelength plate can be installed therein. Further, when this square holding plate is supported by the grooves 12, 12,
As shown in FIG. 3, a 1/2 wavelength plate 11a is provided at the center of the square holding plate 11, which corresponds to the optical path.

This half-wave plate 11a is made of a thin piece of uniaxial crystal, such as quartz, cut so as to include the optical axis, and consists of light that vibrates in a plane that includes the optical axis (ordinary ray), and a vibrating plane that is perpendicular to this. Since it has a different refractive index for light (extraordinary ray) with
By setting the thickness appropriately, a phase difference of 1/2 wavelength is obtained.

As a result, in the half-wave plate 11a, the incident light having a predetermined polarization angle can be changed to an arbitrary polarization angle by appropriately setting the vibration planes of the ordinary ray and the extraordinary ray. Can be emitted.

In this way, in the above configuration, if several square retaining plates 11 each having a half-wave plate 11a that can be changed to any different polarization angle are arranged, the square retaining plates 11 can be placed in the grooves 12 and 12. To insert or not to insert, and part 1
The degree of polarization of the light irradiated onto the recording medium 8 can be adjusted by simply rotating the square holding plate 11 provided with the /2 wavelength plate 11a by 90 degrees left and right and mounting it in the grooves 12.

By the way, in detecting the servo signal, a predetermined two-dimensional shape and its light intensity distribution are necessary for the light spot incident on the photodetector 10 in order to obtain the servo signal with good sensitivity. That is, in the focus direction servo signal, when the optical pickup is accurately tracing the recording medium 8, the optical bonnet is circular and the servo signal output from the photodetector 10 is approximately zero; When it deviates from this, it becomes an ellipse and its output becomes a positive or negative signal.

In addition, in the servo signal in the track direction, when the optical pink-up accurately traces the recording groove on the recording medium 8, the optical intensity distribution is symmetrical with respect to a certain reference plane, and the servo signal output from the photodetector 10 is is approximately zero, and on the other hand, if it deviates from the exact trace, it will no longer be symmetrical and its output will be a positive or negative signal.

In this manner, the servo signal output is set to almost zero in a normal trace state, and when a deviation occurs, a positive or negative signal is output depending on the direction, thereby making it possible to control the optical pickup with high sensitivity.

However, the material of the recording medium 8, such as the birefringence of the transparent resin layer (polycarbonate, etc.) that covers and protects the recording surface, or the shape of the recording grooves may be affected by various factors (internal stress during molding, raw materials and manufacturing conditions). Photodetector 1 of the above light spot may change due to slight changes, etc.)
This may affect the two-dimensional shape on 0 and its light intensity distribution, and it may not be possible to obtain a servo signal with good sensitivity.

In such cases, the conventional method is to adjust the mounting condition of each optical element, for example, change the mounting direction of the semiconductor laser by rotating it with respect to the optical axis, and change the direction of the shaping prism accordingly to change the polarization angle. However, in the above configuration, the 1/2 wavelength plate 11a to be inserted is selected, and the square holder vi, 11 equipped with the 1/2 wavelength plate 11a is inserted, or 90 °By rotating and inserting,
The degree of polarization of the light irradiated onto the recording medium 8 can be adjusted.

As a result, the two-dimensional shape of the light spot and its light intensity distribution, which have been deformed due to the birefringence of the material of the recording medium 8 or the change in the shape of the recording groove, can be returned to their normal state.

Therefore, the photodetector 1 that detects the servo signal
0, the two-dimensional shape of the light spot and its light intensity distribution can be adjusted appropriately.

As a result, in the past, it was necessary to adjust optical elements, etc. in order to obtain servo signals with good sensitivity, but with the above,
A necessary servo signal can be obtained by simply inserting the square holding plate 11 provided with the 1/2 wavelength plate 11a.

[Embodiment 2] An embodiment of the optical pink amplifier according to claim 2 of the invention will be described below with reference to FIGS. 4 and 5. Note that the same reference numerals are used for each element having the same function as in Example 1, and a description thereof is omitted.

In the optical pickup, as shown in FIG. 5, the light from the semiconductor laser l passes through the aperture 6 through the optical elements 2, 3, 4, and 5, and passes through the objective lens 7, as in the first embodiment. The light is focused at a predetermined position on the recording medium 8. The return light, which is the reflected light from the recording medium 8 , follows the above-mentioned optical path in the reverse direction, is reflected by the beam splitter 4 , and is detected by the photodetector 10 via the condenser lens 9 .

As shown in FIG. 4, which is an enlarged portion of section B in FIG. 5, a round retaining plate 13 and a recess ( A support member) 14 is provided.

The recess 14 is formed in a substantially cylindrical shape coaxially on the objective lens 7 side of the peripheral edge of the approximately circular opening 6, and is removably fitted into the inner peripheral surface of the recess 14. A round retaining plate 13 having a substantially disc shape is provided to match the retaining plate 13 . Furthermore, when this round holding plate 13 is fitted into the recess 14, a 1/2 wavelength plate 13a similar to that in Embodiment 1 almost controls the optical path between the raising mirror 5 and the objective lens 7. It runs vertically across.

In this way, in the above configuration, any 1/2 wavelength plate 13a
is selected, and the round holding plate 13 equipped with the 1/2 wavelength plate 13a is fitted into the recess 14 or not, and the round holding plate 13 equipped with the 1/2 wavelength plate 13a is rotated left and right. The degree of polarization of the light irradiated onto the recording medium 8 can be adjusted simply by fitting and mounting the recording medium 8.

By the way, in the detection of the servo signal, the first embodiment
As described above, a certain two-dimensional shape of the light spot entering the photodetector 10 and its light intensity distribution are necessary in order to obtain a servo signal with high sensitivity.

However, the material of the recording medium 8, such as the birefringence of the transparent resin N (polycarbonate, etc.) that covers and protects the recording surface, or the shape of the recording grooves may be affected by various factors (internal stress during molding, raw materials, manufacturing conditions, etc.). Photodetector 1 of the above light spot may change due to slight changes, etc.)
This may affect the two-dimensional shape on 0 and its light intensity distribution, and it may not be possible to obtain a servo signal with good sensitivity.

In such cases, the conventional method is to adjust the mounting condition of each optical element, for example, change the mounting direction of the semiconductor laser by rotating it with respect to the optical axis, and change the direction of the shaping prism accordingly to change the polarization angle. However, in the above configuration, the degree of polarization of the light irradiated onto the recording medium 8 can be adjusted by adjusting the round holding plate 3 equipped with the 1/2 wavelength plate 13a to be fitted. I can do it.

As a result, the two-dimensional shape of the light spot and its light intensity distribution, which have been deformed due to the birefringence of the material of the recording medium 8 or the change in the shape of the recording groove, can be returned to their normal state.

Therefore, the photodetector 1 that detects the servo signal
0, the two-dimensional shape of the light spot and its light intensity distribution can be adjusted appropriately.

As a result, in the past, it was necessary to adjust optical elements, etc. in order to obtain servo signals with good sensitivity, but with the above,
A necessary servo signal can be obtained by simply inserting the round holding plate 13 provided with the 1/2 wavelength plate 13a.

Furthermore, the round holding plate 13 is attached to close the opening 6, thereby preventing dust and the like from entering the inside of the optical pickup. In addition, when there is no need to use the round holding plate 13, if the round holding plate 13 equipped with a parallel glass plate is fitted in the recess 14 instead of the 1/2 wavelength plate 13a, dust can be removed in the same way as above. etc. can be prevented from entering.

Therefore, by adjusting the degree of polarization of the light irradiated to the recording medium 8, the two-dimensional shape of the light spot and its light intensity distribution necessary for the servo signal in the photodetector 10 can be secured, while preventing dust from entering the inside of the optical pickup. can be prevented.

[Effects of the Invention] As described above, the optical pink amplifier according to claims 1 and 2 is an optical pickup that records and reproduces information by irradiating light onto a recording medium. This configuration includes a support member that allows a 1/2 wavelength plate to be removably installed on the optical path so that it can be changed.

As a result, by installing the above 1/2 wavelength plate,
The polarization direction of the light irradiated onto the recording medium can be changed. Therefore, it is possible to save the effort of readjusting the optical elements on the optical path in order to change the polarization direction of light as in the conventional case.

FIG. 2 is an explanatory diagram showing the configuration of an optical pick amplifier.

The third is a front view showing a square holding plate equipped with a 1/2 wavelength plate.

Figure 4 is an enlarged view of the main parts of the optical pink-up.

FIG. 5 is an explanatory diagram showing the configuration of the optical pick amplifier.

FIG. 6 shows a conventional example, and is a block diagram of an optical pink-up.

6 is an aperture, 8 is a recording medium, Ila is a 1/2 wavelength plate, 1
2 is a groove (the support member L13a is a 1/2 wavelength plate, and 14 is a recess (support member).

Patent applicant Sharp Corporation

[Brief explanation of drawings]

1 to 5 show one embodiment of the present invention. FIG. 1 is an enlarged view of the main parts of the optical pickup.

Claims (1)

[Claims] 1. In an optical pickup that records and reproduces information by irradiating light onto a recording medium, there is a light beam on the optical path so as to change the polarization direction of the light.
An optical pickup characterized by having a support member on which a /2 wavelength plate can be detachably installed. 2. In an optical pickup that is equipped with an aperture through which the light that is irradiated and reflected on the recording medium is emitted and entered, there is a
The support member has a support member on which the /2 wavelength plate can be installed in a detachable manner, and the support member is configured such that the 1/2 wavelength plate closes the opening when the 1/2 wavelength plate is installed on the support member. An optical pickup characterized by being provided with.