JPH11283268A - Method and device to adjust optical head system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy in adjustment, and to facilitate adjustment without experiencing an out-of visual field by generating interference fringes to optical beams by means of a diffraction grating piece, which is arranged at the light converging position of the beams from an optical head, projecting the fringes to an imaging device by means of an observation optical system, adjusting the optical system of the head based on the projected picture and detecting the phase information of the wave front of the fringes. SOLUTION: A beam spot converged by the objective lens 7 of an optical head 1 is reflection-diffracted by a grooved disk piece 8, and interference fringes are generated by superimposing 0-order diffracted light and ±1 st-order diffracted light in a transversely shifted manner. The fringes are projected onto the light receiving surface of a camera 15 by an observation optical system 70 made of lenses 12 and 13 and image formed. The projected image is then aberration-analyzed by a picture processing device 16 and the head 1 is adjusted so that aberration is minimized. Thus, accuracy in the adjustment of the head 1 is improved and no out-of visual field is experienced even though the adjustment, in which the angle of the lens 7 is slightly varied, is conducted because the visual field is wide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for adjusting an optical system of an optical head used in an optical recording / reproducing apparatus.

[0002]

2. Description of the Related Art An example of this type of conventional optical head optical system adjusting apparatus will be described with reference to FIG.

In FIG. 7, reference numeral 1 denotes an optical head which is an object to be adjusted, 2 denotes a semiconductor laser which is a light source of the optical head 1, and 3 denotes divergent light emitted from the semiconductor laser 2. 4 is a collimator lens for converting the divergent light 3 into parallel light, 5 is a parallel light, 6 is a mirror for reflecting the parallel light 5 and changing its direction, and 7 is a parallel light 5 reflected by the mirror 6. Is an objective lens for converging light to a predetermined minute spot.

[0004] 108 is a cover glass having the same thickness as the optical disk substrate, 109 is a minute spot converged on the upper surface of the cover glass 108 by the objective lens 7, 110 is a microscope optical system for enlarging and observing the minute spot 109, Reference numeral 111 denotes convergent light transmitted through the microscope optical system 110, 1
Reference numeral 12 denotes a beam splitter for separating the focus detection light from the convergent light 111, and reference numeral 113 denotes a filter for limiting the amount of the convergent light 111. Reference numeral 114 denotes an image of the minute spot 109; 115, a camera for observing the image 114; and 116, an image processing device for processing an image obtained by the camera 115.

In the conventional optical head adjusting apparatus having the above-described configuration, the optical head 1 having the semiconductor laser 2 as a light source is provided.
The microspot 109 condensed on the upper surface of the cover glass 108 through the collimator lens 4, the mirror 6, and the objective lens 7 is enlarged by the microscope optical system 110, and is then transmitted through the beam splitter 112 and the filter 113 to the camera 1.
An image 114 is formed on the 15 light receiving surfaces.

The camera 115 observes a beam spot profile 117 as shown in FIG. This beam spot profile 117 is stored in the image processing apparatus 1.
By 16, the profile of the central light (zero-order light) is removed, and the profile 118 of the primary ring as shown in FIG. 8B is displayed. By judging the profile 118, the optical head 1 is controlled so that the optical aberration of the optical head is minimized.
Make adjustments. The optical head 1 is adjusted by, for example, minutely changing the angle of the objective lens 7 (coma aberration adjustment) or minutely changing the position of the collimator lens 4 in the optical axis direction (adjusting astigmatism). Cover glass 108
Is performed so that the minute spot 109 condensed on the upper surface of the substrate has a predetermined shape.

[0007]

However, in the above-described conventional optical head adjustment system, the optical aberration information is viewed only by the light amount distribution of the beam spot profile 117, and there is no wavefront phase information. In addition, since a large portion of the beam spot light amount is discarded and the minute energy of the profile 118 of the primary ring is analyzed,
There is a problem that the accuracy of analyzing the optical aberration, that is, the adjustment accuracy of the optical head 1 is poor.

Furthermore, since the minute spot 109 needs to be enlarged at a high magnification by the microscope optical system 110, the field of view is narrow. For this reason, when an adjustment such as minutely changing the angle of the objective lens 7 is performed, there is a problem in that the adjustment immediately falls out of the field of view and the adjustment is difficult.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, detects a phase information of a wavefront of an interference fringe, has good adjustment accuracy, and has a method of adjusting an optical head optical system which is easy to adjust without deviating from a visual field. It is intended to provide.

[0010]

According to the present invention, there is provided a method for adjusting an optical head optical system, comprising the steps of: providing a diffraction grating piece disposed at a condensing position of a light beam from an optical head; The method is characterized in that fringes are generated, the interference fringes are projected on an imaging device by an observation optical system, and the optical system of the optical head is adjusted based on the projected image.

Further, the adjusting device for the optical head optical system according to the present invention comprises:
In order to achieve the above object, a diffraction grating piece that is arranged at a focus position of a light beam from an optical head and generates an interference fringe in the light beam, and an interference fringe of the light beam generated by the diffraction grating piece is captured by an imaging unit. An observation optical system configured by a plurality of lenses for projection, and an imaging device for imaging interference fringes of the light beam,
An image processing apparatus that performs aberration analysis based on image information about interference fringes from the imaging apparatus, and an optical system adjustment unit that adjusts an optical system of the optical head based on information about aberration analysis from the image processing apparatus are provided. It is characterized by the following.

As the above-mentioned diffraction grating piece, it is preferable to use a grooved disk piece having a large number of grooves parallel to the upper surface of a transparent flat plate made of transparent glass or transparent resin. The provided one may be adopted.

Claims 2 to 5 and 8 to 10 describe the case where the diffraction grating piece is constituted by a grooved disk piece, but the contents are constituted by the diffraction grating piece provided with light and shade stripes. It can be applied if it is.

According to the adjusting method and the adjusting apparatus of the optical head optical system of the present invention, the reflected diffraction light from the diffraction grating piece such as the grooved disk piece interferes, the interference fringes are imaged, and the aberration analysis is performed. Since the phase information of the wavefront of the fringes can be detected, the aberration detection accuracy of the optical system of the optical head is high,
Good adjustment accuracy of optical head. Further, since the field of view can be widened, even if an adjustment such as minutely changing the angle of the objective lens of the optical head is performed, it is easy to adjust without deviating from the field of view.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of an adjusting method and an adjusting device for an optical head optical system according to the present invention.

FIG. 1 is a schematic view (including a front view and a plan view) of an optical system of an adjustment device for an optical head optical system according to a first embodiment.
FIG. 2 is an explanatory diagram of an interference fringe generation principle in the first embodiment,
FIG. 3 is an explanatory view showing the arrangement of the observation optical system in the first embodiment, FIG. 4 is a front view showing the appearance of the optical head optical system adjusting device of the first embodiment, and FIG. 5 is the optical head of the first embodiment. FIG. 2 is a schematic diagram (including a front view and a side view) illustrating a configuration of a driving unit of the optical system adjustment device.

The configuration of the optical system of the optical head optical system adjusting apparatus according to the first embodiment will be described with reference to FIG.

In FIG. 1, reference numeral 1 denotes an optical head of an object to be adjusted;
Reference numeral 2 denotes a semiconductor laser as a light source of the optical head 1, reference numeral 3 denotes divergent light emitted from the semiconductor laser 2, reference numeral 4 denotes a collimator lens for converting the divergent light 3 into parallel light, reference numeral 5 denotes parallel light, and reference numeral 6 denotes parallel light 5. A mirror 7 for reflecting and changing the direction is an objective lens for converging the parallel light 5 reflected by the mirror 6 to a predetermined minute spot.

Reference numeral 8 denotes a grooved disk piece which is formed to have the same thickness as the optical disk substrate and performs a reflection / diffraction action; 9 denotes an interference light reflected and diffracted by the grooved disk piece 8; 10 reflects the parallel light 5 on the emission side; This is a beam splitter for transmitting the interference light 9 on the opposite side.

Reference numeral 11 denotes a beam splitter for splitting the focus detection light from the interference light 9. Reference numerals 12 and 13 denote lenses, respectively, which constitute an observation optical system 70 as a set of two lenses. 14 is the interference light from the observation optical system 70, 15
Denotes a camera (imaging device) for imaging the interference light 14, 1
Reference numeral 6 denotes an image processing device for processing an image obtained by the camera 15.

The operation of the adjustment device for the optical head optical system configured as described above will be described.

The divergent light 3 emitted from the semiconductor laser 2 which is the light source of the optical head 1 becomes parallel light 5 by a collimator lens 4, and this parallel light 5 is reflected by a mirror 6.
The light is focused on the upper surface of the grooved disk piece 8 by the objective lens 7. 0 reflected and diffracted by the grooved disk piece 8
The first-order diffracted light 20 and the ± first-order diffracted lights 21 and 22 (see FIG. 2) interfere with each other to generate interference fringes, and become the interference light 9. And 2
The interference fringes are projected onto the light receiving surface of the camera 15 by the observation optical system 70 including the two lenses 12 and 13 and observed. The observed interference fringes are analyzed for aberrations by the image processing device 16,
The optical head 1 is adjusted so that aberration is minimized. The adjustment of the optical head 1 means, for example, minutely changing the angle of the objective lens 7 (coma aberration adjustment) or minutely changing the position of the collimator lens 4 in the optical axis direction (adjusting astigmatism).

Next, the principle of interference fringe generation will be described with reference to FIG.

In FIG. 2, reference numeral 7 denotes an objective lens, 8 denotes a grooved disk piece, and 18 denotes a plurality of grooves formed on the upper surface of the grooved disk piece 8. Reference numeral 19 denotes a beam spot condensed by the objective lens 7, and reference numerals 20, 21, and 22 denote 0-order diffracted light, 1st-order diffracted light, and −1st-order diffracted light obtained by diffracting the beam spot 19 by the groove 18.

The pitch p of the groove 18 satisfies p = λ / NA. Here, λ represents the wavelength of the laser beam (light beam), and NA represents the numerical aperture of the objective lens 7.

The beam spot 19 is diffracted by the groove 18, and the 0th-order diffracted light 20 and the ± 1st-order diffracted lights 21 and 22 are respectively superposed as lateral shifts of the optical wavefront to generate an interference fringe representing a differential wavefront. The interference fringes appear in the hatched portions shown in FIG. 2, and the pattern of the fringes changes according to the aberration of the optical system of the optical head 1. The information on the interference fringes is detected and adjusted so as to minimize the aberration.

Next, based on FIG.
The optical arrangement of the observation optical system 70 composed of 2 and 13 will be described.

The focal length of the lens 12 is f1, the lens 13
Is f2. Incidentally, 7 is an objective lens, and 25 is a light receiving surface of the camera 15.

As shown in FIG. 3, the distance from the objective lens 7 to the lens 12 is f1, the distance from the lens 12 to the lens 13 is f1 + f2, and the distance from the lens 13 to the light receiving surface 25 of the camera 15 is f2. With such an arrangement, the interference fringes generated at the position of the objective lens 7 can be accurately projected on the light receiving surface 25 of the camera 15.

Next, the configuration of the optical head optical system adjusting device of the first embodiment will be described with reference to FIG.

In FIG. 4, 1 is an optical head, 8 is a grooved disk piece, 40 is a disk piece holding means for holding the grooved disk piece 8, and 12 and 13 are two lenses, respectively.
The observation optical system 70 is configured as a set, and 15 is an observation camera. 30 is a focus detection optical system, 31 is the optical head 1
Is an optical system adjusting means for making an adjustment such as minutely changing the angle of the objective lens 7. Reference numerals 32 and 33 denote a slide stage and a switching lever for switching the grooved disk piece 8 to another grooved disk piece 8a having a different groove pitch (see FIG. 5).

Numeral 40 denotes a disk piece holding means, which is a grooved disk piece 8 such that the beam spot converged by the objective lens 7 of the optical head 1 crosses the groove 18 (see FIG. 2) of the grooved disk piece 8. Reciprocating in the horizontal direction, and moving the grooved disk piece 8 vertically so that the focused position of the beam spot focused by the objective lens 7 of the optical head 1 matches the upper surface of the grooved disk piece 8. Have the function of doing. This vertical movement is performed by feeding back the signal of the focus detection optical system 30.

The drive mechanism of the disk piece holding means 40 has a structure as shown in FIG.

In FIG. 5, reference numeral 8 denotes a first grooved disk piece, and 8a denotes a second grooved disk piece having a groove pitch different from that of the first grooved disk piece 8. Note that the optical head optical system adjusting apparatus of this embodiment adjusts the optical head 1 having two objective lenses 7 having different NAs for recording and reproducing two different types of optical disks, for example, CD and DVD. Is considered. In this case, 2 of different NA
2 having different groove pitches corresponding to the objective lenses 7
Two grooved disk pieces 8, 8a are required.

However, when the objective lens 7 adjusts one optical head 1, the second grooved disk piece 8a is unnecessary.

Reference numeral 41 denotes a drive element, and reference numeral 42 denotes a parallel leaf spring. These reciprocate the grooved disk piece 8 or 8a in a horizontal direction at a very small distance (for example, 10 pitches of grooves) and at an extremely low speed (for example, 1 μm / sec). Has the function of causing. Therefore, a signal having a constant cycle is input to the driving element 41.

Reference numeral 43 denotes another drive element, and reference numeral 44 denotes a flat plate spring. A feedback signal from the focus detection optical system is input to the drive element 43. The driving elements 41 and 43 use, for example, piezoelectric elements. Alternatively, a giant magnetostrictive element or the like can be used.

As described above, according to the adjustment device for the optical head optical system of the first embodiment, the objective lens 7 of the optical head 1
The beam spot condensed by the light is reflected and diffracted by the grooved disk pieces 8 and 8a, and the zero-order diffracted light 20 and ± 1
Interference fringes are generated by superimposing the next-order diffracted lights 21 and 22 laterally. The interference fringes are projected and imaged on the light receiving surface 25 of the camera 15 by the observation optical system 70 including the two lenses 12 and 13, and the projection image is subjected to aberration analysis by the image processing device 16 so that the aberration is minimized. The optical head 1 is adjusted as follows. In the present embodiment, the grooved disk pieces 8 and 8a are reciprocated in the horizontal direction so that the beam spot crosses the groove 18, and the interference fringes are imaged and aberration analysis is performed.
In this way, more accurate aberration analysis can be performed as compared to the case where the grooved disk pieces 8 and 8a are stopped.

As described above, according to the adjusting device for the optical head optical system of the first embodiment, the diffracted light reflected by the grooved disk pieces 8, 8a interferes, and the interference fringes are imaged to analyze the aberration. As a result, the phase information of the wavefront of the interference fringes can be detected, so that the aberration detection accuracy of the optical system is high, and
Adjustment accuracy is good. Further, since the field of view is wide, even if an adjustment such as minutely changing the angle of the objective lens 7 is performed, the adjustment does not deviate from the field of view and the adjustment is easy.

FIG. 6 is a schematic view of a grooved disk piece according to a second embodiment of the present invention.

The adjustment device for the optical head optical system of the second embodiment has the same basic configuration as that of the first embodiment.
A different point is that a grooved disk piece 45 corresponding to two types of NAs is used without using a pair of grooved disk pieces 8 and 8a.

In FIG. 6, reference numeral 45 denotes a grooved disk piece;
Reference numeral 46 denotes a region having a groove having a pitch corresponding to the NA of the first objective lens, and reference numeral 47 denotes a region having a groove having a pitch corresponding to the NA of the second objective lens. Using only one grooved disk piece 45 having these two types of groove pitches,
The optical head 1 having two objective lenses A is adjusted.

That is, by controlling the input signal to the drive element for reciprocating the grooved disk piece 45 in the horizontal direction, the first
When the objective lens is set on the optical axis, the beam spot crosses the groove in the area 46, and when the second objective lens is set on the optical axis, the beam spot crosses the groove in the area 47. Alternatively, regardless of which objective lens is set on the optical axis, an input signal to the drive element is controlled so that the beam spot crosses both grooves of the region 46 and the region 47, and necessary image processing is performed. The aberration analysis is performed ignoring the information on the non-existing side.

As described above, in the optical head optical system adjusting device of the second embodiment, the control is performed so that only one of the two regions 46 and 47 having two different groove pitches of the grooved disk piece 45 crosses. Alternatively, only the necessary image information is subjected to aberration analysis.

According to the optical head optical system adjusting apparatus of the second embodiment, the switching of the grooved disk piece is performed by using the grooved disk piece 45 having the two different types of groove pitch areas 46 and 47. It is possible to adjust the optical head 1 having two objective lenses having different NAs without performing. This eliminates the need for a switching mechanism, simplifies the adjustment device, and eliminates the need for a switching operation, thereby reducing the adjustment time.

[0046]

According to the present invention, the aberration detection accuracy of the optical system of the optical head can be increased and the detection field can be widened. As a result, the optical head optical system can be adjusted with high accuracy and efficiency. It is possible to provide an adjustment method and an adjustment device for an optical head optical system that can perform the adjustment.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an optical system of an adjustment device of an optical head optical system according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of an interference fringe generation principle in the first embodiment.

FIG. 3 is an explanatory diagram illustrating an arrangement of an observation optical system according to the first embodiment.

FIG. 4 is a front view illustrating an appearance of an adjustment device of the optical head optical system according to the first embodiment.

FIG. 5 is a schematic diagram illustrating a configuration of a driving unit of the adjustment device for the optical head optical system according to the first embodiment.

FIG. 6 is a schematic view of a grooved disk piece according to a second embodiment of the present invention.

FIG. 7 is an optical system schematic diagram of a conventional optical head optical system adjustment device.

FIG. 8 is a schematic diagram of a beam spot profile in a conventional optical head optical system adjusting device, where (a) shows a beam spot profile observed by a camera;
(B) shows a beam spot profile of the primary ring displayed by the image processing apparatus.

[Explanation of symbols]

 Reference Signs List 1 optical head 2 semiconductor laser 7 objective lens 8, 8a, 45 grooved disk piece (diffraction grating piece) 70 observation optical system 15 camera (imaging device) 16 image processing device 18 groove 31 optical system adjusting means 40 disk piece holding means 41 , 43 drive element

Claims (10)

[Claims] An interference fringe is generated in a light beam by a diffraction grating piece arranged at a condensing position of a light beam from an optical head, and the interference fringe is projected on an imaging device by an observation optical system, and the projection image is formed on the projection image. A method for adjusting an optical head optical system, comprising adjusting an optical system of the optical head based on the information. 2. The method for adjusting an optical head optical system according to claim 1, wherein the diffraction grating piece is a grooved disk piece. 3. A projection image obtained by an image pickup device is processed by driving the grooved disk piece so that a condensed beam from an optical head crosses the groove of the grooved disk piece. 3. The method for adjusting an optical head optical system according to item 2. 4. The grooved disk piece is constituted by two pieces having different groove pitches from each other, and said two pieces are formed by a switching mechanism.
4. The method for adjusting an optical head optical system according to claim 2, wherein one of the grooved disk pieces is switched and used. 5. The grooved disk piece has two regions having different groove pitches from each other.
3. The method for adjusting an optical head optical system according to item 1. 6. The method according to claim 1, wherein the light beam is a laser beam.
6. The method for adjusting an optical head optical system according to any one of items 5 to 5. 7. A diffraction grating piece which is arranged at a focus position of a light beam from an optical head and generates interference fringes in the light beam, and projects an interference fringe of the light beam generated by the diffraction grating piece onto an imaging unit. An observation optical system composed of a plurality of lenses, an imaging device that captures interference fringes of the light beam, an image processing device that performs aberration analysis based on image information on interference fringes from the imaging device, and an image processing device. An optical system adjusting means for adjusting the optical system of the optical head based on the information on the aberration analysis of the optical head. 8. The adjustment device for an optical head optical system according to claim 7, wherein the diffraction grating piece is a grooved disk piece. 9. The adjusting device for an optical head optical system according to claim 8, further comprising a disk piece holding means for reciprocating the grooved disk piece so that a converged beam from the optical head crosses the grooved disk piece. 10. A drive element for driving a disc piece holding means for reciprocating a grooved disc piece so that a light beam from an optical head crosses the optical disc, and an optical axis of a light beam from the optical head for driving the grooved disc piece. The optical head optical system adjusting device according to claim 9, further comprising a driving element for driving the disk piece holding means to move the disk piece holding means in the direction.