JP4127422B2 - Optical characteristic detection method and optical characteristic detection apparatus for optical system including lens and other optical elements - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical characteristic detection method and an optical characteristic detection apparatus for an optical system ( including a lens and the like ) of an optical head used in an optical recording / reproducing apparatus.
[0002]
[Prior art]
An example of a conventional adjusting device for this type of optical head optical system will be described with reference to FIG.
[0003]
In FIG. 7, 1 is an optical head that is an object to be adjusted, 2 is a semiconductor laser that is a light source of the optical head 1, and 3 is divergent light emitted from the semiconductor laser 2. Further, 4 is a collimator lens for making the divergent light 3 parallel light, 5 is parallel light, 6 is a mirror for reflecting and changing the direction of the parallel light 5, and 7 is parallel light 5 reflected by the mirror 6. Is an objective lens for condensing the light into a predetermined minute spot.
[0004]
108 is a cover glass having the same thickness as the optical disk substrate, 109 is a micro spot focused on the upper surface of the cover glass 108 by the objective lens 7, 110 is a microscope optical system for magnifying and observing the micro spot 109, and 111 is a microscope Convergent light transmitted through the optical system 110, 112 is a beam splitter for separating focus detection light from the convergent light 111, and 113 is a filter for limiting the amount of the convergent light 111. 114 is an image of the minute spot 109, 115 is a camera for observing the image 114, and 116 is an image processing device for processing an image obtained by the camera 115.
[0005]
In the conventional optical head optical system adjusting apparatus having the above-described configuration, a minute spot focused on the upper surface of the cover glass 108 from the optical head 1 having the semiconductor laser 2 as the light source, through the collimator lens 4, the mirror 6, and the objective lens 7. 109 is magnified by the microscope optical system 110, and an image 114 is formed on the light receiving surface of the camera 115 through the beam splitter 112 and the filter 113.
[0006]
A beam spot profile 117 as shown in FIG. The beam spot profile 117 is removed by the image processing device 116 from the central light (0th-order light) profile, and a primary ring profile 118 as shown in FIG. 8B is displayed. The profile 118 is determined, and the optical head 1 is adjusted so that the optical aberration of the optical head is minimized. The adjustment of the optical head 1 may be performed by, for example, changing the angle of the objective lens 7 minutely (coma aberration adjustment) or changing the position of the collimator lens 4 in the optical axis direction minutely (astigmatism adjustment). The fine spot 109 collected on the upper surface of the cover glass 108 is formed in a predetermined shape.
[0007]
[Problems to be solved by the invention]
However, in the conventional optical head optical system adjustment apparatus described above, the optical aberration information is only seen by the light amount distribution of the beam spot profile 117, so there is no wavefront phase information. In addition, since the minute energy of the primary ring profile 118 is analyzed by discarding a large portion of the beam spot light quantity, there is a problem that the accuracy of analyzing the optical aberration, that is, the adjustment accuracy of the optical head 1 is poor.
[0008]
Further, since the micro 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 adjustments such as changing the angle of the objective lens 7 minutely are made, there is a problem in that it is difficult to perform the adjustment because it is immediately out of the field of view.
[0009]
The present invention eliminates the above-mentioned conventional problems and can detect an optical characteristic of an optical head optical system ( including a lens and the like ) with high accuracy based on phase information of a wavefront of an interference fringe and an optical An object of the present invention is to provide a characteristic detection device.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an optical characteristic detection method for an optical system including a lens and other optical elements according to the present invention diffracts light from the lens with a diffraction grating to generate an interference fringe, and the diffraction A phase changing step of changing the phase of the interference fringes by a grating; and a characteristic detecting step of detecting an optical characteristic of an optical system including the lens and other optical elements based on the interference fringes before and after the phase change. And
[0011]
In order to achieve the above object, an optical characteristic detection apparatus for an optical system including a lens or other optical element according to the present invention is arranged near the condensing position of the light from the lens to diffract the light from the lens. A diffraction grating that generates interference fringes; phase changing means that changes the phase of the interference fringes by the diffraction grating; an imaging device that images the interference fringes; and the lens based on image information about the captured interference fringes. And an image processing apparatus for detecting optical characteristics of an optical system including other optical elements .
[0012]
As the diffraction grating, it is preferable to use a diffraction grating in which a large number of grating grooves parallel to the upper surface of a transparent flat plate made of transparent glass or transparent resin are provided, but a transparent flat plate provided with light and shade stripes is adopted. May be.
[0014]
According to the lens optical property detection method and optical property detection device of the present invention, the reflected diffracted light from a diffraction grating such as a grooved disk piece is caused to interfere, the interference fringe is imaged, and aberration analysis is performed. Therefore, the optical characteristics of the optical system ( including the lens and other optical systems ) of the optical head can be detected with high accuracy.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an adjustment method and an adjustment apparatus for an optical head optical system according to the present invention will be described below with reference to the drawings.
[0016]
FIG. 1 is a schematic diagram of an optical system (including a front view and a plan view) of an optical head optical system adjusting apparatus according to the first embodiment. FIG. 2 is an explanatory diagram of the principle of interference fringe generation according to the first embodiment. FIG. 4 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 optical system of the first embodiment. It is a schematic diagram (a front view and a side view are included) which shows the structure of the drive part of this adjustment apparatus.
[0017]
The configuration of the optical system of the adjusting device for the optical head optical system according to the first embodiment will be described with reference to FIG.
[0018]
In FIG. 1, 1 is an optical head of an object to be adjusted, 2 is a semiconductor laser which is a light source of the optical head 1, 3 is diverging light emitted from the semiconductor laser 2, and 4 is a collimator for making the diverging light 3 parallel light. A lens 5 is parallel light, 6 is a mirror for reflecting the parallel light 5 to change its direction, and 7 is an objective lens for condensing the parallel light 5 reflected by the mirror 6 into a predetermined minute spot.
[0019]
8 is a grooved disk piece that is formed to have the same thickness as the optical disk substrate and has a reflection diffraction action, 9 is interference light reflected and diffracted by the grooved disk piece 8, 10 reflects the parallel light 5 on the exit side, and This is a beam splitter for transmitting the interference light 9.
[0020]
Reference numeral 11 denotes a beam splitter for branching the focus detection light from the interference light 9. Reference numerals 12 and 13 each denote a lens, and the observation optical system 70 is constituted by a set of two lenses. Reference numeral 14 denotes interference light from the observation optical system 70, 15 is a camera (imaging device) for imaging the interference light 14, and 16 is an image processing device for processing an image obtained by the camera 15.
[0021]
The operation of the optical head optical system adjusting apparatus configured as described above will be described.
[0022]
The divergent light 3 emitted from the semiconductor laser 2 that is the light source of the optical head 1 is converted into parallel light 5 by the collimator lens 4, and the parallel light 5 is reflected by the mirror 6, and the upper surface of the grooved disk piece 8 by the objective lens 7. It is focused on. The 0th-order diffracted light 20 reflected by the grooved disk piece 8 and the ± 1st-order diffracted lights 21 and 22 (see FIG. 2) interfere with each other to generate interference fringes and become the interference light 9. Then, 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 subjected to aberration analysis by the image processing device 16, and the optical head 1 is adjusted so that the aberration is minimized. The adjustment of the optical head 1 means, for example, changing the angle of the objective lens 7 minutely (coma aberration adjustment) or changing the position of the collimator lens 4 in the optical axis direction minutely (astigmatism adjustment).
[0023]
Next, the principle of generating interference fringes will be described with reference to FIG.
[0024]
In FIG. 2, 7 is an objective lens, 8 is a grooved disk piece, and 18 is 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 20, 21, and 22 denote 0th-order diffracted light, 1st-order diffracted light, and −1st-order diffracted light obtained by diffracting the beam spot 19 by the groove 18.
[0025]
The pitch p of the grooves 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.
[0026]
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 superposed as lateral shifts of the optical wavefront, respectively, to generate interference fringes representing a differential wavefront. The interference fringes appear in the shaded area shown in FIG. 2, and the fringe pattern changes according to the aberration of the optical system of the optical head 1. This interference fringe information is detected and adjusted to minimize the aberration.
[0027]
Next, the optical arrangement of the observation optical system 70 including the two lenses 12 and 13 will be described with reference to FIG.
[0028]
The focal length of the lens 12 is f1, and the focal length of the lens 13 is f2. Reference numeral 7 denotes an objective lens, and 25 denotes a light receiving surface of the camera 15.
[0029]
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. By arranging in this way, the interference fringes generated at the position of the objective lens 7 can be accurately projected onto the light receiving surface 25 of the camera 15.
[0030]
Next, the configuration of the optical head optical system adjusting apparatus according to the first embodiment will be described with reference to FIG.
[0031]
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 each a lens and constitute a pair of observation optical system 70. , 15 are observation cameras. Reference numeral 30 denotes a focus detection optical system, and reference numeral 31 denotes an optical system adjustment unit that performs adjustments such as minutely changing the angle of the objective lens 7 of the optical head 1. 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 (see FIG. 5) having a different groove pitch.
[0032]
Reference numeral 40 denotes a disk piece holding means which horizontally moves the grooved disk piece 8 so that the beam spot collected by the objective lens 7 of the optical head 1 crosses the groove 18 (see FIG. 2) of the grooved disk piece 8. And a function of moving the grooved disk piece 8 in the vertical direction so that the condensing position of the beam spot collected by the objective lens 7 of the optical head 1 is aligned with the upper surface of the grooved disk piece 8. Have. This vertical movement is performed by feeding back the signal of the focus detection optical system 30.
[0033]
Further, the drive mechanism of the disk piece holding means 40 is configured as shown in FIG.
[0034]
In FIG. 5, 8 is a first grooved disk piece, and 8 a is a second grooved disk piece having a groove pitch different from that of the first grooved disk piece 8. 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, two grooved disk pieces 8 and 8a having different groove pitches are required corresponding to the two objective lenses 7 having different NAs.
[0035]
However, when the objective lens 7 adjusts one optical head 1, the second grooved disk piece 8a is not necessary.
[0036]
Reference numeral 41 denotes a drive element, and 42 denotes a parallel leaf spring, which functions to reciprocate the grooved disk piece 8 or 8a in the horizontal direction at a very small distance (for example, 10 pitches of the groove) and at a very low speed (for example, 1 μm / sec). Have. For this reason, a signal having a constant period is input to the drive element 41.
[0037]
Reference numeral 43 denotes another drive element, and 44 denotes a flat plate spring. A feedback signal from the focus detection optical system is input to the drive element 43. As the drive elements 41 and 43, for example, piezoelectric elements are used. Alternatively, a giant magnetostrictive element or the like can also be used.
[0038]
As described above, according to the optical head optical system adjusting apparatus of the first embodiment, the beam spot condensed by the objective lens 7 of the optical head 1 is reflected and diffracted by the grooved disk pieces 8 and 8a, and the next time. The folded light 20 and the ± first-order diffracted lights 21 and 22 are superposed side by side to generate interference fringes. 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. 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 interference fringes are imaged and aberration analysis is performed. Compared with the case where the attached disk pieces 8 and 8a are stopped, aberration analysis with higher accuracy can be performed.
[0039]
As described above, according to the adjustment apparatus for the optical head optical system of the first embodiment, the reflected diffracted light by the grooved disk pieces 8 and 8a is caused to interfere, and the interference fringes are imaged and analyzed for aberration, thereby causing interference. Since the phase information of the fringe wavefront can be detected, the aberration detection accuracy of the optical system is high, and the adjustment accuracy of the optical head 1 is good. In addition, since the field of view is wide, even if 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.
[0040]
FIG. 6 is a schematic view of a grooved disk piece according to the second embodiment of the present invention.
[0041]
The optical head optical system adjusting apparatus according to the second embodiment has the same basic configuration as that of the first embodiment, except that a pair of grooved disk pieces 8 and 8a are not used. The grooved disk piece 45 corresponding to the type of NA is used.
[0042]
In FIG. 6, 45 is a grooved disk piece, 46 is a region having grooves with a pitch corresponding to the NA of the first objective lens, and 47 is a region having grooves having a pitch corresponding to the NA of the second objective lens. . The optical head 1 having two objective lenses having different NAs is adjusted using only one grooved disk piece 45 having these two types of groove pitches.
[0043]
That is, when the first objective lens is set on the optical axis by controlling the input signal to the driving element that reciprocates the grooved disk piece 45 in the horizontal direction, the beam spot crosses the groove in the region 46; When the second objective lens is set on the optical axis, the beam spot crosses the groove in the region 47. Alternatively, when either objective lens is set on the optical axis, the input signal to the drive element is controlled so that the beam spot crosses the grooves in both the region 46 and the region 47 and image processing is necessary. Aberration analysis is performed by ignoring the information on the other side.
[0044]
As described above, in the optical head optical system adjusting apparatus according to the second embodiment, control is performed so as to cross only one of the two different groove pitch regions 46 and 47 of the grooved disk piece 45. Alternatively, only the image information on the necessary side is subjected to aberration analysis.
[0045]
According to the optical head optical system adjusting apparatus of the second embodiment, by using the grooved disk piece 45 having the regions 46 and 47 having two different groove pitches, the grooved disk piece is not switched. An optical head 1 having two objective lenses with different NAs can be adjusted. This eliminates the need for a switching mechanism, simplifies the adjustment device, and eliminates the need for switching work, thereby reducing the adjustment time.
[0046]
【The invention's effect】
According to the present invention, since the phase information of the wavefront of the interference fringes can be detected, the optical characteristics of the optical system of the optical head ( including lenses and other optical systems ) can be detected with high accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of an optical system of an optical head optical system adjusting apparatus 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 showing an arrangement of observation optical systems in the first embodiment.
FIG. 4 is a front view showing an appearance of the optical head optical system adjusting apparatus according to the first embodiment.
FIG. 5 is a schematic diagram illustrating a configuration of a driving unit of the optical head optical system adjusting device 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 a schematic diagram of an optical system of a conventional optical head optical system adjustment apparatus.
FIGS. 8A and 8B are schematic diagrams of a beam spot profile in a conventional optical head optical system adjustment device, where FIG. 8A shows a beam spot profile observed by a camera, and FIG. 8B is a display 1 displayed by an image processing apparatus; The beam spot profile of the next ring is shown.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 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 Disc piece holding means 41, 43 Drive element

Claims (10)

An interference fringe generating step of diffracting light from the lens with a diffraction grating to generate an interference fringe;
A phase changing step of changing the phase of the interference fringes by the diffraction grating ;
A characteristic detecting step of detecting optical characteristics of the optical system including the lens and other optical elements based on interference fringes before and after the phase change, and detecting optical characteristics of the optical system including the lens and other optical elements Method. 2. The lens or other optical element according to claim 1, wherein the interference fringe generation step is a step of generating the interference fringes by causing interference of diffracted light beams of different orders diffracted by the diffraction grating. A method for detecting optical characteristics of an optical system . The phase changing step is a step of changing the phase of the interference fringes by moving the diffraction grating relative to the lens so that light from the lens crosses a grating groove formed in the diffraction grating. An optical characteristic detection method for an optical system including the lens or other optical element according to claim 1. The optical characteristic detection method for an optical system including a lens and other optical elements according to claim 1, wherein a plurality of diffraction gratings having different groove pitches are switched and used as the diffraction grating. 5. The optical characteristic detection method for an optical system including a lens and other optical elements according to claim 1, wherein the diffraction grating has a plurality of regions having different groove pitches. A diffraction grating that is arranged in the vicinity of a light collection position of light from the lens and diffracts light from the lens to generate interference fringes;
Phase changing means for changing the phase of the interference fringes by the diffraction grating ;
An imaging device for imaging the interference fringes;
An image processing apparatus for detecting optical characteristics of an optical system including the lens and other optical elements based on image information regarding the captured interference fringes, and an optical system including the lens and other optical elements. Optical property detection device. 7. The optical characteristic detection apparatus for an optical system including a lens and other optical elements according to claim 6, wherein the diffraction grating generates interference fringes in which diffracted light beams having different orders interfere. 8. The optical characteristic detection apparatus for an optical system including a lens and other optical elements according to claim 6, wherein the diffraction grating has a plurality of regions having different groove pitches. The phase changing means is constituted by relative moving means for moving the lens relative to the diffraction grating so that light from the lens crosses a grating groove formed in the diffraction grating. Item 9. An optical characteristic detection device for an optical system including the lens or other optical element according to any one of Items 6 to 8. The phase changing means includes a first drive element that moves the diffraction grating relative to the lens so that light from the lens crosses a grating groove formed in the diffraction grating;
A lens or other optical element according to claim 6, comprising: a second driving element that moves the diffraction grating in an optical axis direction of light from the lens. Optical characteristic detection device for optical system.

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