JP2002182092A - Lens adjusting device and lens adjusting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lens adjusting device and a lens adjusting method utilizing a diffraction interference method. SOLUTION: This adjusting device 100 is provided with a diffraction grating 22 obtaining an interference image by diffracting light transmitted through a lens 10 and making it interfere, electromagnetic moving means (46 and 48) moving the lens in an orthogonal direction to the grating of the diffraction grating, and an aberration detecting device 30 obtaining the aberration of the lens from the change of light intensity at plural points on the interference image when the lens is moved. The adjusting device is provided with a controller 32 for allowing the lens to move by a moving means and obtaining a position where the light intensity becomes maximum or minimum from the change of the light intensity at the several points on the interference image obtained when the lens is moved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information storage medium of an optical disk system, for example, a DVD (Digita 1 Versatile
k), an optical lens adjusting device and an adjusting method for forming a light spot by combining light in an optical lens for reading and writing information, or a laser beam machine, a laser microscope or the like.

[0002]

BACKGROUND OF THE INVENTION In order to read information from an optical disk type high-density information storage medium and to store information on the high-density information storage medium, light emitted from a light source can be accurately irradiated to a target place. Optical system is required. for that reason,
In particular, the objective lens of the optical system not only requires strict optical characteristics per se, but also must be accurately fixed to a target place.

As a method of inspecting or adjusting an objective lens, as shown in FIG. 1, light (eg, laser light) 2 emitted through an objective lens 1 is used as a reference 3 for lens inspection (eg, an optical disk). ), The reflected light from the reference reference 3 is detected, the reproduction signal 4 obtained from this detection is compared with the reference signal 5, and the phase difference 6 between the reproduction signal 4 and the reference signal 5 is minimized. It is conceivable to adjust the inclination or the like of the objective lens 1 so that the phase difference falls within a predetermined allowable value (jitter method).

However, the characteristics of the objective lens 1 generally differ from each other, and there is no fixed relationship between the amount of tilt of the objective lens 1 and the like and the phase difference 6, and as shown in FIG. The other objective lens 1B may exhibit significantly different characteristics (lens tilt angle-phase characteristics). Also,
The tilt adjustment of the objective lens and the comparison of the signals must be repeatedly performed, and it is difficult to objectively determine at which stage the adjustment is completed. Further, the inclination of the objective lens 1 and the like cannot be sufficiently grasped from the reproduction signal 4. Therefore, the present invention
It is an object of the present invention to provide a new lens adjustment device that replaces the above-described jitter method.

[0005]

SUMMARY OF THE INVENTION A lens adjusting device according to the present invention includes a diffraction grating for diffracting and transmitting light transmitted through a lens to obtain an interference image;
Electromagnetic moving means for moving the lens in a direction orthogonal to the grating of the diffraction grating, and aberration detecting means for obtaining aberration of the lens from changes in light intensity at a plurality of points in the interference image when the lens moves. The adjusting device also has control means for moving the lens by the moving means and obtaining a position where the light intensity becomes maximum or minimum from a change in light intensity at a plurality of points in the interference image obtained when the lens is moved.

In another mode of the adjusting device, the control means includes a lens moving means for moving the lens from a first position where the light intensity is maximum or minimum to a second position where the light intensity is maximum or minimum. To move.

[0007] In another embodiment of the adjusting device,
The aberration detecting means obtains aberration by detecting light intensity at a plurality of positions obtained by dividing the first position and the second position.

Further, another embodiment of the above-mentioned adjusting device includes adjusting means for adjusting the inclination of the lens based on the aberration obtained by the aberration detecting means.

Still further, in another form of the adjusting device, the moving means includes a support for movably supporting the lens, first magnetic field forming means held by the support, and first magnetic field forming means. And a second magnetic field forming means for moving the lens.

A lens adjusting apparatus using a diffraction interference method according to the present invention prepares a diffraction grating for diffracting light transmitted through a lens and causing interference, thereby obtaining an interference image, and using an electric magnetic field forming means to connect the lens to the diffraction grating. It moves in the direction perpendicular to the grating, measures the light intensity at a plurality of points of the interference image formed when the lens moves, a first position where the light intensity is maximum or minimum, and then the light intensity is maximum. Alternatively, a minimum second position is obtained, and the lens is moved between the first position and the second position to obtain the lens aberration.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of embodiments of the present invention will be described below with reference to the accompanying drawings. First, FIG. 3 shows an optical storage medium such as a DVD (Digita1 Versa).
A lens adjustment system or an optical system (adjustment) using a diffraction interference method for an optical lens that reads and writes information on a tile disk, or an optical lens that forms a light spot by combining light in a laser processing machine, a laser microscope, or the like. Apparatus) 100
The whole is shown.

The lens to be adjusted by the adjustment system 100 (hereinafter referred to as “objective lens”) 10 is
It is arranged in the optical pickup 12. Objective lens 1
Numeral 0 is supported by a tilt adjusting device (tilt adjusting means) 14 so that the tilt of the objective lens 10 can be adjusted. The objective lens 10 is also supported by an electromagnetic moving device (moving means) 16. By operating the moving device 16, the objective lens 10 can be moved in a direction orthogonal to the optical axis. Before adjusting the objective lens 10, the objective lens 10 and the optical pickup 12 are in a state where the optical axis of the objective lens 10 is substantially aligned with an optical axis 20 of an evaluation device 18 described later (it is not necessary to completely match the optical axis). No.).

The evaluation device 18 for evaluating the inclination of the objective lens 10 with respect to the optical axis 20 has a diffraction grating 22. The diffraction grating 22 is made of a plate made of a transparent material such as an acrylic resin, a polycarbonate resin, or glass. For example, a plurality of light transmission slits (gratings) are formed on one surface in parallel at a predetermined pitch. . For example, when the optical lens to be adjusted is an objective lens for reading and writing information on an optical disk, the pitch of the slits is preferably equal to the distance between tracks on the optical disk. Also,
In the present embodiment, the diffraction grating 22 is arranged perpendicular to the optical axis 20 with the grating directed in the left-right direction in the drawing.

On the opposite side of the objective lens 10 with the diffraction grating 22 therebetween, a collimator lens 24 for demodulating the light transmitted through the objective lens 10 and the diffraction grating 22 into parallel light, and a parallel light transmitted through the collimator lens 24. An imaging lens 26 that forms an image again, and an imaging device (for example, a charge-coupled device) 28 that receives light transmitted through the imaging lens 26 are arranged.

The image pickup device 28 is electrically connected to an aberration measuring device (detection means) 30. Aberration measurement device 30
A display device for displaying an image received by the image sensor 28;
An aberration calculator (both not shown) for measuring aberration of the objective lens 10 based on an image displayed on the display device is provided. The aberration measuring device 30 is electrically connected to a control device (control means) 32 for controlling the driving of the tilt adjusting device 14 and the moving device 16 described above.

The adjustment of the objective lens 10 by the adjustment system 100 having the above configuration will be briefly described. At the time of adjustment, as shown in FIG. 3, the objective lens 10 is fixed with its optical axis substantially aligned with the optical axis 20. Next, a light source (not shown) arranged on the opposite side of the diffraction grating 22 with the objective lens 10 therebetween is turned on, and parallel light (for example, laser light) is incident on the objective lens 10. The light transmitted through the objective lens 10 is focused by a diffraction grating 22 (particularly, a diffraction slit or the like formed on the diffraction grating 22). Diffraction grating 2
Light transmitted through 2 is a 0th-order diffracted light, ± 1st-order diffracted light, ...
The light is split into ± n-order diffracted lights, and is projected on an image pickup device 28 via a collimator lens 24 and an imaging lens 26. here,
The diffraction grating 22 is designed so that the 0th-order diffracted light and the + 1st-order diffracted light partially interfere with each other on the projection plane of the image sensor 28, and the 0th-order diffracted light and the -1st-order diffracted light interfere with each other. Therefore, as shown in FIGS. 4A and 4B, the display device for reproducing the image projected on the image sensor 28 has the 0th-order diffracted light and +
An interference image (interference fringe) of the first-order diffracted light and an interference image (interference fringe) of the zero-order diffracted light and the -1st-order diffracted light are displayed.

The shape of the interference fringes differs depending on the inclination of the objective lens 10. Now, when the objective lens 10 is inclined in a direction orthogonal to the slit of the diffraction grating 22, an interference fringe shown in FIG. When the objective lens 10 is inclined in the longitudinal direction of the slit of the diffraction grating 22, FIG.
The interference fringes shown in FIG.

Further, when the moving device 16 is driven based on a signal from the control device 32 to move the diffraction grating 22 in the left-right direction (transverse direction of the slit) in FIG. A shift occurs between the change in the phase of the folded light and the change in the phase of the -1st-order diffracted light, and the light intensity at each point of the interference fringes changes. Accordingly, as shown in FIG. 4A, a line passing through the center of the interference image between the 0th-order diffracted light and the ± 1st-order diffracted light (shown as “lens moving direction” in the drawing) is orthogonal to this line. The light intensity change at the intersection Pa with the line X passing through the center of the interference image of the 0th-order diffracted light and the + 1st-order diffracted light draws a waveform (sine wave) Ia shown in FIG. Another point P on the line X
The light intensity change b shows a waveform (sine wave) Ib shown in FIG. 5, and a phase difference φ is observed between the waveforms Ia and Ib. Therefore, for example, with reference to the phase of the point Pa,
When the difference between the phase of a and the phases of a plurality of other points on the line X in FIG. 4A is plotted on a graph, a quadratic curve shown in FIG. 6 is obtained, and the quadratic coefficient of this quadratic curve is obtained. Is obtained as the amount of inclination of the objective lens 10 with respect to the slit transverse direction.

As shown in FIG. 4B, the phase differences of a plurality of points on a line Y or Y 'passing through the point Pa and forming a predetermined angle (for example, ± 45 °) with the line X are plotted on a graph. Then, a quadratic curve similar to the quadratic curve shown in FIG. 5 is obtained, and the quadratic coefficient of this quadratic curve is obtained as the amount of inclination of the objective lens 10 in the longitudinal direction of the slit.

The calculation for obtaining the inclination of the objective lens 10 as described above can be automatically performed by the aberration measuring device 30.

The tilt amount of the objective lens 10 calculated by the aberration measuring device 30 is output to the control device 32. The control device 32 controls the objective lens 10 obtained from the aberration measurement device 30.
The inclination adjusting device 14 is driven on the basis of the inclination amount to correct the inclination of the objective lens 10 respectively.

Next, the moving device 16 will be described in detail with reference to FIG. As shown in FIG.
Has a lens holding unit 40 that holds the objective lens 10. In the present embodiment, the lens holding unit (supporting unit) 40
Is disposed on the side of the objective lens 10 and is supported by a base 44 fixed to the optical pickup 12 via a thin elastic wire (supporting portion) 42 extending in the horizontal direction. The lens holding unit 40 also has a coil (first magnetic field forming means) wound around an axis extending in a direction orthogonal to the optical axis.
The coil 46 is electrically connected to the control device 32. Further, a permanent magnet (second magnetic field forming means) 48 fixed to the base 44 is disposed on the opposite side of the objective lens 10 with the lens holding section 40 interposed therebetween. In the permanent magnet 48, different magnetic poles are magnetized at both ends in the horizontal direction (in the illustrated embodiment, N is applied to the left end portion).
The pole and the south pole are magnetized at the right end. ).

In the mobile device 16 configured as described above,
When a current is applied to the coil 46 from the control device 32, a magnetic field is formed near the coil 46. This magnetic field attracts or repels the magnetic field formed by the permanent magnet 48, and causes the lens holding portion 66 holding the coil 46 and the objective lens 10 held by the lens holding portion 66 to be orthogonal to the optical axis direction. In the horizontal direction (the direction indicated by the arrow 50).

It should be noted here that the value of the current applied to the coil 46 and the current
The amount of movement of the objective lens 10 that is moved by applying a voltage to the optical system differs depending on the optical system including the objective lens 10 due to variations in the characteristics of the coil 46 and assembly errors.

Then, the control device 32 changes the current applied to the coil 46, and for example, for a point Pa shown in FIG. 5, a point (position) Pa _max1 where the light intensity becomes maximum, and then the light intensity becomes maximum again. _Are obtained (points) Pa _max2 and current values (I ₁ , I ₂ ) corresponding thereto. Next, the control device 32 determines the two points Pa _max1 , P max at which the light intensity is maximum.
The current difference [ΔI = (I ₁ −I ₂ ) / N] between a _max2 is divided into a plurality of parts and the sample period [ΔI = (I ₁ −I ₂ ) / N: N
Is a positive integer]. Then, the control device 32 determines that I ₁
By changing the current value for each sample period until I ₂ detects the light intensity of the interference fringes from the objective lens as described above 10
Find the slope of Also, in order to correct the calculated inclination,
The control device 32 drives the tilt adjusting device 14 to adjust the tilt of the objective lens 10.

In the above description, the point where the light intensity is maximum and the next maximum are determined. However, the minimum point and the next minimum point are determined, and the current values corresponding to them are calculated. The lens inclination measurement can be performed based on the measurement.

The tilt of the objective lens 10 can be eliminated by moving the diffraction grating and the members supporting and driving the diffraction grating. However, the optical members including these diffraction gratings and the like are provided with the objective lens 10 and its supporting member. In contrast to the above, there is a problem in that the adjustment of the objective lens is very heavy, which requires much time for adjustment, and that the rigidity of the adjustment device must be strengthened. There is an advantage that it can be performed with a simple configuration.

Further, the present invention is limited only by the configuration described in the claims, and other configurations can be freely modified, and all such modified examples are technical features of the present invention. It belongs to the range.

[0029]

As is apparent from the above description, in the present invention, the range from the point of maximum (or minimum) of the light intensity contained in the interference image to the point of the next maximum (or minimum) of light intensity is obtained. In order to move the objective lens, the optimal and shortest lens tilt adjustment can be performed according to each optical pickup.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of lens adjustment of a conventional jitter type optical pickup.

FIG. 2 is an explanatory diagram of a conventional lens adjustment method.

FIG. 3 is a schematic configuration diagram of a lens adjustment device according to the present invention.

FIGS. 4A and 4B are diagrams showing (a) a diffraction interference image showing the inclination of the lens in the direction transverse to the slit of the diffraction grating, and (b) a diffraction interference image showing the inclination of the lens in the longitudinal direction of the slit.

FIG. 5 is a diagram showing a change in light intensity due to movement of an objective lens.

FIG. 6 is a diagram showing a phase distribution of interference fringes.

FIG. 7 is a perspective view showing an objective lens and a configuration for supporting the objective lens.

[Explanation of symbols]

 100: Lens adjustment device 10: Objective lens 12: Optical pickup 14: Tilt adjustment device 16: Electromagnetic movement device 18: Evaluation device 22: Diffraction grating 30: Aberration measurement device 32: Control device 46: Coil (first magnetic field) Forming means) 48: permanent magnet (second magnetic field forming means) 66: lens holding portion

Continued on the front page F-term (reference) 2H043 AD04 AD12 AD23 2H044 AC01 5D118 AA06 CD04 CD06 5D119 AA38 BA01 JA43 JC07 PA05

Claims (6)

[Claims] 1. A lens adjustment device using a diffraction interference method, wherein the adjustment device diffracts light transmitted through the lens to cause interference and obtains an interference image. Electromagnetic adjustment means for moving the lens in a direction orthogonal to the grating; and aberration detecting means for obtaining the aberration of the lens from a change in the light intensity at a plurality of points in the interference image when the lens is moved; Comprises a control means for moving a lens by the moving means, and obtaining a position where the light intensity is maximum or minimum from a change in light intensity at a plurality of points in an interference image obtained when the lens is moved. Lens adjustment device. 2. The control means moves the lens by the moving means from a first position at which the light intensity becomes maximum or minimum to a second position at which the light intensity becomes maximum or minimum. The lens adjustment device according to claim 1, wherein: 3. The method according to claim 2, wherein the aberration detecting means detects aberration by detecting light intensity at a plurality of positions obtained by dividing the first position and the second position. Item 3. The lens adjustment device according to Item 2. 4. The lens adjusting device according to claim 1, further comprising an adjusting unit that adjusts a tilt of the lens based on the aberration obtained by the aberration detecting unit. 5. The moving means includes: a supporting portion that movably supports the lens; first magnetic field forming means held by the supporting portion; and the lens in cooperation with the first magnetic field forming means. 5. The lens adjusting device according to claim 1, further comprising: a second magnetic field forming unit that moves the lens. 6. A lens adjusting method using a diffraction interference method, comprising: preparing a diffraction grating for diffracting light transmitted through the lens to cause interference, thereby obtaining an interference image; Moving in a direction orthogonal to the grating of the above, measuring the light intensity at a plurality of points of the interference image formed when the lens moves, a first position where the light intensity is maximum or minimum, and then the light intensity A lens adjustment method comprising: obtaining a second position at which is maximum or minimum; and moving the lens between the first position and the second position to obtain lens aberration.