JPH1091994A - Optical system for adjusting the tilt of the objective lens - Google Patents

Abstract

(57) [Problem] To adjust the tilt of an objective lens without impairing the detection accuracy of the tilt angle of the objective lens even when a laser irradiation system that generates a laser beam for interference fringe measurement is turned on and is not dimmed. And an optical system for adjusting the inclination of the objective lens, which can quickly perform the adjustment. An optical system for adjusting the tilt of an objective lens according to the present invention includes an objective lens having an annular flat portion provided so as to surround an outer periphery of a lens portion, and detection light for detecting the tilt of the objective lens. From the one side of the objective lens 1 toward the annular flat portion 3, and a detection light receiving system 1 for receiving the detection light reflected by the annular flat portion 3
1 and a laser irradiation system 28 for irradiating the objective lens 1 with a laser beam for writing and reading information as a laser beam P2 for measuring interference fringes from the other side of the objective lens 1, and detecting the reflected laser beam from the annular flat portion 3. By detecting the light detection position, the inclination of the objective lens 1 with respect to the reference plane is detected. The detection light receiving system 11 blocks transmission of the interference fringe measurement laser light P2 and transmits the detection light. A polarizing plate 18 was provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system for adjusting the tilt of an objective lens used for adjusting the tilt of the objective lens with respect to a reference plane.

[0002]

2. Description of the Related Art Conventionally, in an information writing / reading apparatus using an optical disk, an information recording surface of the optical disk is
If the objective lens of the optical pickup is tilted, so-called coma aberration occurs, which makes it impossible to write information on the optical disk at a high density, and also causes noise when reading information. Adjustments have been made so that the inclination of the objective lens with respect to the information recording surface of the optical disk falls within a predetermined standard.

The objective lens 1 is molded by a molding method. The objective lens 1 has an annular flat surface surrounding the outer periphery of a lens portion 2 in order to detect its inclination as shown in FIG. A unit 3 is provided, and the inclination of the objective lens 1 is adjusted according to the procedure described below.

First, as shown in FIG. 1B, a detection beam emitted from a helium-neon laser 4 as a detection light irradiation system is a laser beam P having a diameter of 1 mm to 2 mm as detection light.
Is irradiated on an information recording surface 6 as a reference surface of an optical disk 5 arranged at a position about 1 m away from the helium-neon laser 4, and the laser beam P ′ reflected by the information recording surface 6 is received as a detection light. The position is detected by the screen 7 as a system, and the position Q of the laser beam P ′ on the screen 7 (see FIG. In FIG. 1B, reference numeral O1 denotes a rotation center of the optical disk 6.

Next, as shown in FIG. 1C, the objective lens 1 is disposed at substantially the same position as the position where the optical disk 5 is disposed.
As shown in an enlarged manner in FIG. 1D, a laser beam P is irradiated on a part of the annular flat portion 3 from one surface side of the objective lens 1,
The laser beam P 'reflected by the annular plane portion 3
Is detected by the screen 7, and the position Q ′ of the laser beam P ′ on the screen 7 is obtained. Screen 7
1 is provided with a scale 8 as shown in FIG.
The difference between the position Q and the position Q 'of the laser beam P' reflected by the annular plane portion 3 is obtained by the scale 8, and the difference on the scale is converted into an angle, as shown in FIG. In addition, the inclination angle θ of the optical axis O of the objective lens 1 with respect to the normal line N of the information recording surface 6 is detected.

[0006]

By the way, the objective lens 1 whose inclination has been adjusted within the standard with respect to the information recording surface in this way is then set in the interferometer, and finally the information recording surface 6 By observing the shape of the interference fringes with respect to, it is determined whether or not the inclination angle conforms to the standard. For this purpose, a laser irradiation system that generates laser light for writing and reading information is used as a light source that generates laser light for measuring interference fringes, and the objective lens is used to write information as laser light for measuring interference fringes from the other side.・ Reading laser light is applied.

When the interference fringes do not conform to the standard, the tilt of the objective lens 1 is readjusted by using a tilt adjusting optical system of the objective lens, but the tilt of the objective lens 1 is readjusted. In this case, the laser irradiation system is turned off and the detection light P is irradiated on the objective lens 1, or the light amount of the information writing / reading laser light is reduced while the laser irradiation system is on, and the objective lens 1 The position of the reflected detection light on the screen 7 is detected.

However, when the frequency of observing interference fringes of the objective lens 1 and adjusting the tilt of the objective lens 1 is frequently repeated, the laser irradiation system is repeatedly turned on and off, or the amount of information writing / reading laser light is increased. If the dimming is repeated, the tilt adjustment of the objective lens 1 cannot be performed quickly. Conversely, the tilt adjustment of the objective lens 1 is performed without turning on the laser irradiation system to reduce the light amount. In this case, the information writing / reading laser light as the interference fringe measuring laser light is mixed into the detection light receiving system, which becomes noise when detecting the detection light, and the tilt angle of the objective lens 1 cannot be accurately detected. There is a problem.

The present invention has been made in view of the above circumstances, and an object thereof is to turn on a laser irradiation system for generating information writing / reading laser light as interference fringe measuring laser light. Even if it is not dimmed,
An object of the present invention is to provide an optical system for adjusting the tilt of an objective lens, which can quickly adjust the tilt of the objective lens without impairing the detection accuracy of the tilt angle of the objective lens.

[0010]

According to a first aspect of the present invention, there is provided an optical system for adjusting the tilt of an objective lens, the objective lens having an annular flat portion provided so as to surround an outer periphery of a lens portion, and detecting the tilt of the objective lens. A detection light irradiating system that irradiates detection light for use from one surface side of the objective lens toward the annular flat portion,
A detection light receiving system for receiving the detection light reflected by the annular flat portion, and laser irradiation for irradiating the objective lens with laser light for writing and reading information as laser light for interference fringe measurement from the other surface side of the objective lens A tilt adjusting optical system for the objective lens, which detects a tilt of the objective lens with respect to a reference plane by detecting a detection position of the detection light reflected from the annular plane portion, wherein the detection light The light receiving system is provided with a polarizing plate that blocks transmission of the interference fringe measurement laser beam and transmits the detection light.

According to a second aspect of the present invention, in the optical system for adjusting the inclination of the objective lens, the deflection direction of the interference fringe measuring laser beam and the deflection direction of the deflection plate are substantially orthogonal to each other. It is characterized by having. According to a third aspect of the present invention, in the optical system for adjusting the inclination of the objective lens according to the first or second aspect, the detection light is a laser beam.

[0012]

FIG. 2 shows an optical system 9 for adjusting the inclination of an objective lens. In FIG. 2, reference numeral 10 denotes a detection light irradiation system, 11 denotes a detection light reception system, and 12 denotes an optical pickup. The detection light irradiation system 10 includes a helium-neon laser 13.
, A neutral density filter 14, and a half mirror 15. The helium-neon laser 13 emits parallel laser light P1 having a diameter of 1 mm to 2 mm as detection light. Half mirror 15 is neutral density filter 1
The laser beam P1 whose light amount has been adjusted by the
Irradiate toward one side. A part of the annular flat portion 3 of the objective lens 1 is illuminated by the laser light P1.

The laser beam P1 is polarized, and its polarization direction is a direction perpendicular to the plane of the paper, as indicated by reference numeral X1 '. The detection light receiving system 11 includes an autocollimator, and includes a collimator lens 16 and an imaging camera (CCD camera) 17. A polarizing plate 18 is provided between the collimating lens 16 and the imaging camera 17. The role of the polarizing plate 18 will be described later.

As shown in FIGS. 3 and 4, the optical pickup 12 is movably supported by a guide rail 19 of the optical disk device 12A. In FIGS. 3 and 4, reference numerals 19 </ b> A and 19 </ b> A are support columns of the guide rail 19. The optical disk device 12A is provided with a spindle 20, and the optical disk 6 (FIG.
(See (b)), but here, a cover glass 21 is provided as a dummy disk for adjusting the tilt of the objective lens 1. The optical pickup 12 reciprocates along the guide rail 19 between the inner peripheral side and the outer peripheral side of the optical disk device 12A.
An optical system 9 for adjusting the inclination of the objective lens is provided on the outer peripheral side of the optical disk device 12A.
An interferometer 22 is provided on the inner peripheral side of the. The interferometer 22 includes a collimating lens 23 and a beam splitter 24
, Corner cubes 25 and 26, and imaging lens 27A
And an imaging camera 27. The output of the imaging camera 27 and the output of the imaging camera 17 are input to the image processing device 28A. The image processing device 28A includes a personal computer 28B and a keyboard 2 as an operation unit.
8C, a mouse 28D, a monitor M, and the like. The optical disk device 12A has a light source unit 2 as a laser irradiation system.
8 are provided. This light source unit 28 is provided with a laser
The laser beam P2 is normally used for writing and reading information. In order to check whether the tilt angle of the objective lens 1 is within the standard, the optical pickup 12 is set to the interferometer 22. In this case, it is used as a laser beam for measuring interference fringes. This laser light P2 is also polarized,
The polarization direction is parallel to the plane of the paper as indicated by reference sign X2 '. The optical pickup 12 generally includes a rising mirror 29 for deflecting the laser light P2 emitted from the light source unit 28 toward the other surface of the objective lens 1, and a lens holder 30 on which the objective lens 1 is mounted. . The laser beam P2 is converted into a parallel light beam by the lens unit 2 of the objective lens 1.
Is incident on.

The lens holder 30 is formed with a conical receiving surface 30a as shown in an enlarged view in FIG. The annular flat portion 3 of the objective lens 1 is in contact with the receiving surface 30a, and the objective lens 1 is supported by the lens holder 30. To adjust the tilt of the objective lens 1,
As shown in FIG. 3, the optical pickup 12 is moved directly below the tilt adjusting optical system 9, and the tilt of the objective lens 1 is adjusted using a tilt adjusting jig 31 and a tilt adjusting jig moving mechanism (not shown). . The tilt adjustment jig is shown in FIGS.
As shown in (b) in an enlarged manner, the claw 31a has a claw 31a, and the claw 31a is applied to the annular flat surface portion 3, and each direction of the tilt adjusting jig moving mechanism applied to the annular flat surface portion 3 via each claw 31a. The inclination of the objective lens 1 is adjusted by increasing or decreasing the pressing force from the lens. When the laser beam P1 is irradiated, the laser beam P1 is reflected by a part of the annular plane portion 3 to become a reflected laser beam P1 ', passes through the half mirror 15, is guided to the collimating lens 16, and is condensed by the collimating lens 16. Is done. Laser light P2 is the objective lens 1
After being converged once and then diverged, it is guided to the half mirror 16, and a part of the transmitted laser light P 2 ′ of the laser light P 2 is collected by the collimating lens 16.

The polarization direction of the polarizing plate 18 is set in the same direction as the polarization direction of the laser beam P1 or in such a direction that the component of the laser beam P1 transmitted by the polarizing plate 18 has a sufficient amount of light to be sufficiently received by the image sensor 17. Then, the reflected laser light P1 'is guided to the imaging surface 17a of the imaging device 17, and the transmitted laser light P2 is blocked by the polarizing plate 18. Therefore, even if the tilt of the objective lens 1 is adjusted while the light source unit 28 is turned on and the light is not dimmed, the detection accuracy of the tilt angle of the objective lens 1 is not impaired. Image sensor 1
7, a beam spot S3 is formed on the imaging surface 17a by the reflected laser beam P1 '.
Is displayed on the screen G of the monitor M.
The tilt adjustment of the objective lens 1 is performed while observing the beam spot S3 above.

After adjusting the tilt of the objective lens 1, the optical pickup 12 is moved to a position immediately below the interferometer 22, as shown in FIG. The laser light P2 is deflected by the rising mirror 29 toward the objective lens 1. The laser beam P2 is converged by the objective lens 1 and guided to the cover glass 21. The cover glass 21 plays a role of emulating the optical disc 6. The laser light P2 transmitted through the cover glass 21 is condensed by the collimating lens 23,
The light is guided to the beam splitter 24 through the optical path X. The laser beam P2 guided to the beam splitter 24 is split into a light beam to an optical path X1 toward the corner cube 25 and a light beam to an optical path X2 toward the corner cube 26. The luminous flux to the optical path X1 toward the corner cube 25 and the luminous flux to the optical path X2 toward the corner cube 26 are reflected by the respective corner cubes toward the beam splitter 24, and as a result are combined at the optical path X3 to form the imaging lens 2
7A, an image is formed on the imaging camera 27,
Is received by the The received light output of the imaging camera 27 is output to the image processing device 28A, and when the objective lens 1 is inclined with respect to the cover glass 21, interference fringes are generated.
As shown in FIG. 4, the interference fringes K are displayed on the screen G. The number of the interference fringes K depends on the tilt angle of the objective lens 1, and the shape of the interference fringes K depends on the direction of the tilt of the objective lens 1. When the interference fringe K obtained by this observation is not within the wavefront standard, the optical pickup 12 is moved again immediately below the tilt detection optical system 9 to adjust the tilt of the objective lens 1, and after adjusting the tilt, the interference The interference fringe K is observed again by moving the sample to just below the total 22. This adjustment and observation are repeated until the interference fringe falls within the wavefront standard. When it is determined that the interference fringe falls within the wavefront standard, the objective lens 1 is fixed to the lens holder 30 by bonding, and the tilt adjustment operation is performed. finish.

[0018]

Since the optical system for adjusting the inclination of the objective lens according to the present invention is constructed as described above, the laser irradiation system for generating the interference fringe measuring laser light is turned on and the light is not dimmed. However, there is an effect that the tilt of the objective lens can be quickly adjusted without impairing the detection accuracy of the tilt angle of the objective lens.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining detection of an inclination angle of an objective lens using a conventional objective lens inclination adjusting optical system, wherein (a) is a plan view of an objective lens whose inclination is adjusted; (B) is an explanatory diagram showing a state in which the information recording surface of the optical disc is irradiated with the detection light, (c) is an explanatory diagram showing a state in which the annular flat portion of the objective lens is irradiated with the detection light, and (d) is an annular diagram of the objective lens. FIG. 5E is an explanatory diagram showing a state in which the detection light reflected by the flat surface portion is received on the screen, FIG. 7E is an explanatory diagram of a spot formed on the screen based on the detection light reflected by the annular flat portion, and FIG. FIG. 3 is an explanatory diagram of an inclination angle of an objective lens with respect to an information recording surface.

FIG. 2 is an enlarged view showing an optical system for adjusting the tilt of an objective lens according to the present invention.

FIG. 3 is an explanatory diagram for explaining tilt adjustment using the tilt adjustment optical system according to the present invention, and shows a state in which an objective lens is located immediately below the tilt adjustment optical system.

FIG. 4 is an explanatory diagram for explaining tilt adjustment using the tilt adjustment optical system according to the present invention, and shows a state in which an objective lens is positioned immediately below an interferometer.

FIG. 5 is an explanatory view of the tilt adjustment of the objective lens according to the present invention, wherein (a) is an enlarged side view showing a state in which a nail of a tilt adjustment jig is applied to the objective lens held by the lens holder; (B) is a plan view showing a state in which the annular adjustment jig and the objective lens shown in (a) are viewed from above, and (c) is a beam spot formed on the imaging surface based on detection light reflected by the objective lens. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Objective lens 2 ... Lens part 3 ... Annular flat part 6 ... Information recording surface (reference surface) 10 ... Detection light irradiation system 11 ... Detection light reception system 18 ... Polarizing plate 28 ... Light source part (laser irradiation system) P1 ... Laser Light (detection light) P2: Laser light for interference fringe measurement (laser light for information writing / reading)

Claims (3)

[Claims] An objective lens having an annular flat portion provided so as to surround an outer periphery of a lens portion, and detection light for detecting the inclination of the objective lens is irradiated from one surface side of the objective lens toward the annular flat portion. A detection light irradiation system, and a detection light reception system that receives the detection light reflected by the annular flat portion,
A laser irradiation system for irradiating the objective lens with information writing / reading laser light as interference fringe measurement laser light from the other surface side of the objective lens, and detecting a detection position of the detection light reflected from the annular plane portion. By detecting
An optical system for adjusting the inclination of an objective lens for detecting an inclination of the objective lens with respect to a reference plane, wherein the detection light receiving system is configured to block transmission of the interference fringe measurement laser light and transmit the detection light. An optical system for adjusting the tilt of an objective lens, comprising a plate. 2. The optical system for adjusting the tilt of an objective lens according to claim 1, wherein the direction of deflection of the laser beam for measuring interference fringes is substantially orthogonal to the direction of deflection of the deflection plate. 3. The detection light according to claim 1, wherein the detection light is a laser light.
Or the optical system for adjusting the inclination of the objective lens according to 2.