JP2007033098A - Lens measuring method and lens measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lens measuring method and a lens measuring instrument using a detection means of a simple structure. <P>SOLUTION: This lens measuring instrument comprises: a diffraction means for turning a beam output from a lens into diffracted beams of a different order to cause them to interfere with each other; a correction means having the same optical path length as that of the diffraction means as to a beam diffracted by the diffraction means; an aberration measuring means for finding the aberration of the lens based on the diffracted beams; and an inclination adjusting means for adjusting the inclination of the lens based on the aberration found by the measuring means. This measuring instrument is characterized in that the lens and a detection means have the same optical path length as to the optical axis of the beam output from the lens, with the detection means used for detecting the diffracted beams caused to interfere with each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a lens measurement method used for an optical pickup for reading and writing information on an optical disk type high-density information recording medium, for example, BD and HD-DVD using a blue laser light source, DVD and CD using a red laser light source, and the like. And a lens measuring device.

  An optical pickup is an optical component that focuses light from a laser light source with a lens and strikes it on the surface of an optical disk type high-density information recording medium and guides the reflected light to a light receiving element.

  In recent years, the use of a blue laser or the like as a light source of an optical pickup has increased the recording density of a high-density information recording medium in the form of an optical disk with a short wavelength of light from the laser light source. Under such circumstances, there is a demand for a more accurate optical pickup for accurately and precisely irradiating light to a target location.

  However, due to variations in the characteristics of parts constituting the optical system and the assembly accuracy, the characteristics differ greatly for each manufactured optical pickup, and the characteristics of the optical pickup may exceed the allowable range. Therefore, in the optical pickup manufacturing process, it is important to individually adjust the position of the optical system.

  Currently, as a specific method for solving this problem, a diffraction interference method (patents) is used to detect the aberration of the objective lens of the optical pickup by interference measurement and adjust the position of the optical system on the light source side based on the detection result. Reference 1).

  FIG. 4 is a view showing a conventional optical pickup adjusting device. Hereinafter, a diffraction interference type optical pickup adjusting device described in Patent Document 1 will be described with reference to FIG.

  This optical pickup adjusting device includes an optical pickup 1 that emits light, a diffraction grating 3 that diffracts light, an assembled lens 4 that is a detection unit, an imaging lens 5 that collects light, and an imaging for photographing an image. The element 6 includes a characteristic detector 7 that detects a characteristic from the obtained data. Next, a method for adjusting the optical pickup will be described using a specific example.

  In FIG. 4, the light emitted from the optical pickup 1 is collected by the objective lens 2, enters the diffraction grating 3, and is diffracted by the diffraction grating 3 to generate diffracted light of zero order light and ± first order light. In the group lens 4, the generated 0th-order light and + 1st-order light, and 0th-order light and −1st-order light overlap to form an interference fringe pattern, which passes through the imaging lens 5 and is coupled onto the image sensor 6. Image.

  By analyzing the interference fringe pattern obtained by the image sensor 6 by the characteristic detector 7, the aberration of the objective lens 2 is detected.

The group lens 4 is required to reduce the influence of aberration in order to perform an accurate measurement. However, in consideration of its function and availability, the group lens 4 of the microscope as shown is used. . The microscope combination lens 4 has a structure in which a plurality of lenses such as a convex lens and a concave lens are combined.
JP 2001-108575 A

  However, since the detection means constituted by the combination lens in the conventional configuration has a plurality of lenses, the detection means has a complicated structure, and the lens measuring device also has a problem.

  In addition, when the lens is measured without using the group lens, the error corrected by using the group lens in the conventional configuration is not corrected, and there is a problem that the lens measurement cannot be performed.

  The present invention is intended to solve the above-described conventional problems, and an object thereof is to provide a lens measurement method and a lens measurement device having the same performance as the case of using a combined lens without using a combined lens. .

  In order to achieve the above object, the lens measurement method of the present invention diffracts light emitted from a lens into different orders by a diffraction grating, and a correction in which a specific order of diffracted light has the same optical path length as the diffraction grating. The diffracted light is transmitted through a plate, the transmitted light is detected by detection means, and the characteristics of the lens are measured from the detection result.

  As described above, according to the lens measurement device of the present invention, it is possible to perform lens measurement without using a combined lens having a complicated structure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a diagram showing a lens measuring device according to Embodiment 1 of the present invention. In FIG. 1, the same components as those in FIG.

  1, the lens measuring apparatus according to the first embodiment of the present invention includes an optical pickup 1 having a light source 1a, a beam splitter 1b, and a light receiving element 1c, and means for emitting light from the objective lens 2 and the light source from the objective lens 2. And an optical pickup 1 having means for guiding the light incident from the objective lens 2 to the light receiving element, and diffracts the light in order on the optical axis of the light emitted from the objective lens 2 when viewed from the objective lens 2. , A correction plate 8 made of a parallel plate, a detection lens 9 for detecting diffracted light, an imaging lens 5 for condensing the light, and an image sensor 6 for taking an image. The In addition, a characteristic detector 7 is provided which is connected to the image sensor 6 and measures the aberration of the objective lens 2 from the obtained sharing interference image.

  The operation of this lens measuring device will be described in order. Light emitted from the light source 1 a in the optical pickup 1 and incident on the objective lens 2 is emitted from the objective lens 2 and enters the diffraction grating 3. The light incident on the diffraction grating 3 is diffracted by the diffraction grating 3 to generate 0th order diffracted light and ± 1st order diffracted light, and this 0th order diffracted light and ± 1st order diffracted light are overlapped to generate a sharing interference image. The light diffracted by the diffraction grating 3 passes through the correction plate 8 having a specific optical path length of the diffracted light of a specific order (here, 0th order light) of the diffraction grating 3 and the diffracted light and the detection lens 9. The light is condensed by the imaging lens 5 and imaged by the image sensor 6 to generate interference fringes. Here, since each point in the interference fringe has a unique phase, the diffraction grating 3 is moved at a constant speed in a direction perpendicular to the optical axis, and the light intensity change at a certain point in the interference region of the diffracted light is different from that. The phase difference of the change of the light intensity at the point is obtained, the phase difference is analyzed by the characteristic detection unit 7, each aberration is evaluated, the quality of the objective lens 2 is inspected based on the aberration, and the adjustment is made according to the inspection result. Is possible. The aberration at this time usually does not exist alone, but appears in a form in which coma, spherical aberration, astigmatism, and the like are combined. A phase shift method is used for aberration extraction.

  Here, the principle of obtaining an interference image with the same accuracy as that of a conventional lens measuring device using a combined lens with a lens measuring device using a single lens of the present invention will be described. The objective lens in the optical pickup is designed by correcting the spherical aberration corresponding to the thickness of the optical disk in consideration of the actual use situation where the light emitted from the optical pickup is reflected by the optical disk and the reflected light is transmitted. . Therefore, in the diffraction interference method in which inspection is performed without using an optical disc, a structure for correcting spherical aberration corresponding to the thickness of the optical disc is required.

  In the first embodiment of the present invention, in order to correct the spherical aberration corresponding to the thickness of the optical disk, the correction plate 8 having the same material and the same thickness as the diffraction grating 3 is provided between the objective lens 2 and the detection lens 9. Install between. Here, as a material of the diffraction grating 3 and the correction plate 8, for example, quartz glass is used.

  Here, the reason that the thickness and the material of the correction plate 8 are the same as that of the diffraction grating is that the optical path length that is the same as the optical path length generated by the diffraction grating 3 in the diffraction interference method as in Embodiment 1 of the present invention, This is because it can be obtained by passing through the correction plate 8.

  In addition, the thicknesses of the objective lens 2 and the detection lens 9 are equal, and the optical path length of each lens with respect to the light emitted from the light source is equal.

  In addition, since the correction plate 8 in the first embodiment of the present invention is made of the same material and the same thickness as the diffraction grating 3, it is not necessary to make a new design and can be obtained more easily.

  In addition, the detection means composed of a combination lens used in a microscope or the like has a complicated structure and is difficult to reduce in size. However, if the single lens used in Embodiment 1 of the present invention is used, a single lens is used. Therefore, it is possible to easily reduce the size of the optical system.

  Further, when the diffraction grating 3 and the correction plate 8 are bonded together, the influence of the interface between the diffraction grating 3 and the correction plate 8 can be reduced, so that the spherical aberration can be corrected more accurately. Here, when the correction plate 8 is bonded to the surface on which the focal point of the diffraction grating 3 exists, that is, the surface having a groove (grating surface), the structure of the disk can be made closer. In addition, as a means for bonding the diffraction grating 3 and the correction plate 8, the structure is simple but the characteristics of the adhesive are important. The method of adhering with an adhesive that does not cause refraction, and the structure is complicated but mass production. However, it is easy to maintain a certain degree of accuracy, and a method of fitting by providing a convex portion or a concave portion on each of the diffraction grating 3 and the correction plate 8 can be considered.

(Embodiment 2)
FIG. 2 is a diagram showing a lens measuring device according to Embodiment 2 of the present invention. 2, the same components as those in FIGS. 1 and 4 are denoted by the same reference numerals, and description thereof is omitted.

  2, in addition to the components of the lens measurement device of FIG. 1, an attitude control mechanism 10 that controls the attitude of the objective lens 2 of the optical pickup 1 and a mechanism 11 that chucks the objective lens 2 are arranged.

  The light emitted from the objective lens 2 is diffracted by the diffraction grating 3 to form a sharing interference fringe on the image sensor 6, and the sharing interference fringe is imaged by the image sensor 6. The characteristic detector 7 measures the aberration. If an aberration indicating a deviation from the ideal imaging state in the optical system is generated, the optical pickup becomes a defective product, and it is necessary to correct this aberration. For this purpose, the attitude control mechanism 10 is moved from the aberration detected by the characteristic detection unit 7 to change the attitude of the objective lens 2 in a direction to cancel the aberration. By repeating this aberration measurement and changing the posture of the objective lens 2, the influence of the aberration measured from the light emitted from the objective lens 2 is reduced, and the optical pickup is adjusted.

  With this configuration, aberration measurement and tilt adjustment of the objective lens 2 can be performed in conjunction.

(Embodiment 3)
FIG. 3 is a diagram showing a lens measuring device according to Embodiment 3 of the present invention. In FIG. 3, the same constituent elements as those in FIGS.

  In FIG. 3, the lens measuring device according to the third embodiment of the present invention has two objective lenses 13 and 14. A diffraction grating 15, a correction plate 17, a detection lens 19 and an imaging lens 22 are provided on the optical axis of the objective lens 13, and a diffraction grating 16, a correction plate 18, a detection lens 20 and an imaging lens are provided on the optical axis of the objective lens 14. It has a lens 23. The positions of the diffraction gratings 15 and 16, the correction plates 17 and 18, the detection lenses 19 and 20, and the imaging lenses 22 and 23 are determined according to the distance and height between the centers of the designed objective lenses 13 and 14. Yes. The diffraction grating 16, the correction plate 18, and the detection lens 20 are integrally disposed on a stage 24 that moves in three directions of X, Y, and Z.

  Here, the diffraction grating 15 and the correction plate 17 and the diffraction grating 16 and the correction plate 18 are made of the same material and the same thickness. The objective lens 13 and the detection lens 19, the objective lens 14 and the detection lens 20 have the same thickness, and the optical path lengths for the light from the respective light sources are also the same.

  In FIG. 3, light emitted from the light source 12 a on the objective lens 13 side in the optical pickup 12 is transmitted through the collimator lens 12 c, reflected by the mirror 12 f, and emitted from the objective lens 13. Thereafter, the light is diffracted by the diffraction grating 15, passes through the correction plate 17, becomes parallel light by the detection lens 19, and forms an image by the imaging lens 22. The light emitted from the light source 12b on the objective lens 14 side passes through the collimator lens 12d and the beam expander 12e, is reflected by the mirror 12f, and is emitted from the objective lens 14. Thereafter, the light is diffracted by the diffraction grating 16, passes through the correction plate 18, becomes parallel light by the detection lens 20, the optical axis is bent by the half mirror 21, and an image is formed by the imaging lens 23. The objective lens 13 is chucked by the chuck mechanism 11, and the position and posture can be changed by the posture control mechanism 10. Similarly, the position and orientation of the objective lens 14 can be changed.

  With this configuration, it is possible to simultaneously capture the light emitted from the two laser light sources, measure the aberration, and adjust the position and orientation of the lens so as to correct the aberration. If the distance between the centers of the two objective lenses and the height thereof vary due to errors during assembly of the optical pickup, the objective lens 13 side is made to coincide with the optical axis of the detection lens 19 and then the objective lens. The optical axis on the 13th side is measured, and the adjustment stage 24 is moved from the measurement result so that the optical axis on the objective lens 14 side coincides with the optical axis of the detection lens 23. Thereby, the aberration measurement of the two objective lenses can be performed simultaneously regardless of the assembly error of the optical pickup 12.

  Further, considering the case where the blue laser light source is used on the objective lens 14 side and the red laser light source is used on the objective lens 13 side, the objective lens 13 side using the red laser light source that does not require higher accuracy than the blue laser light source is adjusted. Thereafter, the objective lens 14 side is precisely adjusted. Therefore, when the objective lens 14 side requires a longer adjustment time than the objective lens 13 side, the stage is moved in a state where the objective lens 14 side is adjusted to some extent in advance, and the adjustment time can be shortened. .

  The lens measurement method and the lens measurement apparatus of the present invention can reduce the influence of the aberration of the diffraction grating without using complicated detection means such as a combined lens. Therefore, it can be applied to an apparatus for measuring a lens using a diffraction interference method.

The figure which shows the lens measuring device in Embodiment 1 of this invention. The figure which shows the lens measuring device in Embodiment 2 of this invention. The figure which shows the lens measuring device in Embodiment 3 of this invention. The figure which shows the conventional optical pick-up adjustment apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,12 Optical pick-up 1a Light source 1b Beam splitter 1c Light receiving element 2, 13, 14 Objective lens 3, 15, 16 Diffraction grating 4 Pair lens 5, 22, 23 Imaging lens 6 Imaging element 7 Characteristic detector 8, 17, 18 Correction plate 9, 19, 20 Detection lens 10 Attitude control mechanism 11 Chuck mechanism 12a, 12b Light source 12c, 12d Collimator lens 12e Beam expander 12f Mirror 21 Half mirror 24 Adjustment stage

Claims (10)

The light emitted from the lens is diffracted into light of different orders by a diffraction grating, and the diffracted light of a specific order transmits the diffracted light to a correction plate having the same optical path length as the diffraction grating, and the transmitted light And a lens measurement method, wherein the characteristic of the lens is measured from the detection result. 2. The lens measuring method according to claim 1, wherein the light detected by the detecting means is sharing interference light formed by interference of the diffracted light. The lens measuring method according to claim 1, wherein the specific order diffracted light is zero-order diffracted light. The lens measurement method according to claim 1, wherein the detected result is an aberration of the lens. A diffraction grating that forms diffracted light of a different order from the light emitted from the lens, a detection means that detects the diffracted light, and a correction plate having the same optical path length as the diffraction grating with respect to the optical axis of the lens; With
A lens measuring device, wherein the correction plate is arranged between the diffraction grating and the detecting means. The lens measuring device according to claim 5, wherein a grating surface of the diffraction grating and the correction plate face each other. The lens measuring device according to claim 5 or 6, wherein the diffraction grating and the correction plate are joined. The lens measurement device according to claim 7, wherein the diffraction grating and the correction plate are bonded with a translucent adhesive. The lens measurement device according to claim 7, wherein the diffraction grating and the correction plate are joined by fitting. A lens measurement device further comprising a lens measurement mechanism similar to the lens measurement mechanism according to claim 5.

Images