JP2011163970A - Eccentricity measuring method and eccentricity measuring device of aspherical lens - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an eccentricity measuring method and eccentricity measuring device performing eccentricity measurement easily and inexpensively even for aspherical lens deviated largely from spherical shape. <P>SOLUTION: Based on a design formula of a measured lens, spherical surface approximation domain is computed (S1) which is approximated as a part of spherical surface from a vertex of the measured lens; an optical diaphragm for irradiating only spherical surface approximation domain is created (S2); an objective lens is selected (S3) corresponding to the spherical surface approximation domain, the measured lens L; the optical diaphragm and the objective lens are deployed (S4), respectively; measuring light is irradiated (S5) to the measured lens; by performing alignment of the objective lens and the measured lens, measuring light is forced to irradiate (S6) only the spherical surface approximation domain; the measured lens is rotated (S7) around an optical axis of measuring light as rotary shaft; and a value of eccentricity of optical axis of the measured lens to the rotary shaft is measured (S8) by detecting reflection light of measuring light reflected at the spherical surface approximation domain of the measured lens. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an aspherical lens eccentricity measuring method and an eccentricity measuring apparatus, and more particularly to a method and an apparatus for measuring the eccentricity of an aspherical lens using an autocollimation method.

A conventional method for measuring the eccentricity of an aspherical lens using a so-called autocollimation method is disclosed in Patent Document 1.
This autocollimation method is inherently known to be effective for measuring the eccentricity of a spherical shape, and is characterized in that the measurement takes a short time and the accuracy is high.

  However, when an aspherical lens is used as a target, measurement is possible with a lens with a small amount of deformation from the spherical shape, but with an aspherical lens greatly deviating from the spherical shape, the light irradiated to the lens to be measured is at a fixed position. The light is not condensed and the eccentricity measurement cannot be performed.

In recent years, in particular, there has been an increasing demand for an imaging lens used for a built-in camera of a mobile phone, a camera for medical equipment, an objective lens for an optical pickup used for a DVD drive, and the like. Such an imaging lens and an optical pickup objective lens are ultra-compact lenses, and high optical accuracy is required.
In addition, if aspherical lenses are used as these lenses, the number of lenses can be reduced compared to the case of spherical lenses, which is expected to help reduce the size, weight, and cost of equipment equipped with lenses. The

  Therefore, in order to maintain high optical accuracy for the ultra-small aspheric lens, it is significant to perform the eccentricity measurement in a short time and at a low cost.

Patent Documents 2 to 4 propose methods for enabling decentration measurement even for an aspherical lens greatly deviating from a spherical shape.
In the method disclosed in Patent Document 2, the eccentricity measurement is performed by directly measuring the shape of the surface to be measured by a shape measuring machine.
In the method described in Patent Document 3, a lens to be measured and a null optical element that matches the shape of the lens to be measured are arranged in a measurement light beam of an interferometer, and a reference surface and a surface to be measured of the lens to be measured Eccentricity measurement is performed by detecting the reference plane of the null optical element with the common reference plane of each interferometer.
Further, according to the method described in Patent Document 4, two light beams are irradiated on the surface to be measured that rotates around the rotation axis, and fluctuations in interference fringes formed by these light beams reflected by the surface to be measured are measured. Thus, eccentricity measurement is performed.

JP-A-5-340838 Japanese Patent Application Laid-Open No. 7-229811 JP 2007-3344 JP-A-11-173812

  However, the method of Patent Document 2 requires a lot of labor and time for the eccentricity measurement, and the methods of Patent Documents 3 and 4 have a problem that the equipment for the eccentricity measurement is complicated and the cost is high. It was.

  In order to solve the above-mentioned problems of the prior art, the present invention provides an aspherical lens decentration measuring method and a decentering method that can easily and inexpensively perform decentration measurement even for an aspherical lens greatly deviating from a spherical shape. An object is to provide a lead measuring device.

  The method for measuring the eccentricity of an aspheric lens according to the present invention is a method for measuring the amount of eccentricity of a lens to be measured that has at least a part of an aspheric surface, and is based on a design equation for the lens to be measured. A spherical approximate area approximated as a part of a spherical surface is calculated from the apex of the lens, and the lens to be measured is rotated around a rotation axis set in the vicinity of the optical axis of the lens to be measured and approximately parallel to the optical axis. The amount of eccentricity of the optical axis of the lens to be measured with respect to the rotation axis is determined by irradiating the measuring light only to the spherical approximate region of the lens to be measured and detecting the reflected light of the measuring light reflected by the spherical approximate region of the lens to be measured. It is a method of measuring.

Note that the measurement light can be irradiated only to the spherical approximate region by using an optical aperture having an opening.
Moreover, it is preferable that the lens to be measured has an edge portion for positioning, and the rotation axis is set so as to pass through the center of the edge portion.

  An aspherical lens eccentricity measuring apparatus according to the present invention is an apparatus for measuring the amount of eccentricity of a measured lens having at least a part of an aspherical surface, and is measured based on a design equation of the measured lens. Calculation means for calculating a spherical approximate area approximated to a part of a spherical surface from the apex of the lens, and a rotation axis set around the optical axis of the lens to be measured and approximately parallel to the optical axis. Rotating means that rotates to the measuring axis, irradiating means for irradiating the measuring light only to the spherical approximate area of the lens to be measured, and the reflected light of the measuring light reflected by the spherical approximate area of the lens to be measured to detect the measured light with respect to the rotation axis Measuring means for measuring the amount of eccentricity of the optical axis of the lens.

The irradiating means is disposed between the objective lens and the lens to be measured and an aperture for irradiating the light to the lens to be measured at a predetermined irradiation angle with light emitted from the light source. And an optical diaphragm having a portion. In this case, the optical diaphragm preferably has an opening having a size corresponding to the spherical approximate area of the lens to be measured calculated by the calculating means. Further, as the optical diaphragm, a variable diaphragm that can adjust the size of the opening may be used.
Alternatively, the irradiation means includes a light source, an objective lens for irradiating light emitted from the light source toward the lens to be measured at a predetermined irradiation angle, and a light-shielding mask formed on the surface of the lens to be measured. It can also be configured as follows.
Moreover, it is preferable that the lens to be measured has an edge portion for positioning, and the rotation means sets the rotation axis so as to pass through the center of the edge portion.

  According to the present invention, it is possible to measure the eccentricity easily and inexpensively even for an aspherical lens greatly deviating from the spherical shape.

It is a figure which shows the structure of the eccentricity measuring apparatus which concerns on Embodiment 1 of this invention. 3 is a flowchart showing an eccentricity measuring method in the first embodiment. It is the schematic which shows the spherical approximate area in the vertex vicinity of a to-be-measured lens. FIG. 3 is a diagram illustrating a state in which measurement light is incident on a lens to be measured in the first embodiment. It is a figure which shows the eccentric amount of the center of the edge part of a to-be-measured lens, and the optical axis of to-be-measured lens. FIG. 10 is a plan view showing an optical aperture used in a modification of the first embodiment. It is a figure which shows the structure of the eccentricity measuring apparatus which concerns on Embodiment 2. FIG.

Embodiment 1
In FIG. 1, the structure of the eccentricity measuring apparatus 10 which concerns on Embodiment 1 of this invention is shown. The eccentricity measuring apparatus 10 performs eccentricity measurement using a so-called autocollimation method, and includes a light source 12 that emits measurement light M, and a collimator 16 that includes a half mirror 14 is connected to the light source 12. Yes. On the optical axis A of the measurement light M that is collimated by the collimator 16, an objective lens 18 and an optical aperture 20 having an opening 20 a formed at the center thereof are sequentially arranged in front of the collimator 16. A lens holder 22 for holding the lens L to be measured is disposed in front of the diaphragm 20. The lens L to be measured has an edge portion K formed on the periphery thereof for positioning when mounted on an optical device or the like, and the lens holder 22 holds the edge portion K in place. The lens L to be measured is held. The lens holder 22 is fixed on the rotary stage 24, and is configured to be rotated around the optical axis A of the measurement light M together with the lens L to be measured by the rotary stage 24.

On the other hand, on the optical axis A of the measurement light M, a light receiving unit 26 including a CCD image sensor 26a for capturing the reflected light of the measurement light M from the optical surface of the lens L to be measured is disposed behind the collimator 16. The light receiving unit 26 is connected to an arithmetic unit 28 made up of a computer.
The light source 12, the collimator 16, the objective lens 18, and the optical diaphragm 20 constitute irradiation means for irradiating the measurement light M only to the spherical approximate region of the lens L to be measured. The lens holder 22 and the rotating stage 24 constitute a rotating means for rotating the lens L to be measured, and the measuring means for measuring the eccentricity of the optical axis of the lens L to be measured by the light receiving unit 26 and the arithmetic unit 28. Are each configured. The computing device 28 also constitutes a calculation means for calculating a spherical approximate area based on the design formula of the lens L to be measured.

Next, the eccentricity measuring method in the first embodiment will be described with reference to the flowchart of FIG.
First, in step S1, a design formula of the lens L to be measured is input to the arithmetic unit 28, and a spherical approximate area that can be approximated to a part of the spherical surface from the apex of the lens L to be measured is calculated based on this design formula. For example, as shown in FIG. 3, an approximate spherical surface C corresponding to the curvature of the vertex portion is assumed for a lens L to be measured having a shape at least near the vertex away from the spherical shape, and a part of the spherical surface from the vertex is assumed. A spherical approximation region R that can be approximated as follows.

Next, in step S2, an optical aperture 20 for irradiating only the spherical approximate region R calculated by the arithmetic unit 28 in step S1 is created.
When the measurement light M is irradiated to a portion other than the spherical approximate region R, the reflected light from the lens L to be measured does not converge at a certain position, and the eccentricity measurement becomes difficult. For this reason, the optical diaphragm 20 having the opening 20a having such a size that the measurement light M is irradiated only on the spherical approximate region R is created.

  In step S3, the objective lens 18 corresponding to the spherical approximate region R of the lens L to be measured is selected. As shown in FIG. 4, when the objective lens 18 in which the measurement light M is perpendicularly incident on the spherical approximate region R of the lens L to be measured, that is, the lens L to be measured is held by the lens holder 22. The objective lens 18 having a focal length such that the measurement light M is collected at the apparent center of curvature P of the spherical approximate region R is selected. Instead of selection, such an objective lens 18 may be created.

Next, at step S4, the lens holder 22 holds the lens L to be measured, and the optical aperture 20 created at step S2 and the objective lens 18 selected at step S3 are respectively measured light M in front of the collimator 16. On the optical axis A.
At this time, the lens holder 22 holds the lens L to be measured by pressing the edge K of the lens L to be measured, but the object to be measured is such that the center of the edge K coincides with the optical axis A of the measurement light M. The lens L is held.

  Thereafter, in step S5, the measurement light M is irradiated to the lens L to be measured. The measurement light M emitted from the light source 12 is reflected by the half mirror 14, converted into parallel light by the collimator 16, condensed by the objective lens 18, and passed through the opening 20 a of the optical aperture 20. In this state, the lens L to be measured is irradiated.

Next, in step S6, the focus of the measurement light M by the objective lens 18 and the lens L to be measured are aligned. Specifically, as shown in FIG. 4, the measurement light M is perpendicularly incident on the spherical approximate region R of the lens L to be measured, that is, the measurement light M is in the apparent center of curvature P of the spherical approximate region R. Is adjusted so that the relative distance between the objective lens 18 and the lens L to be measured is adjusted.
At this time, the objective lens 18 may be moved along the optical axis A of the measurement light M, or the lens L to be measured may be moved. Further, the relative distance may be adjusted while moving both the objective lens 18 and the lens L to be measured. However, when the objective lens 18 is moved, the relative positional relationship between the objective lens 18 and the optical diaphragm 20 is changed in order to realize the irradiation of the measuring light M only to the spherical approximate region R of the lens L to be measured. The optical diaphragm 20 also needs to move with the objective lens 18 while maintaining.

  In this way, by aligning the objective lens 18 and the lens L to be measured, the measurement light M is incident on only the spherical approximate region R while being incident perpendicularly to the spherical approximate region R of the lens L to be measured. Will be. For this reason, the measurement light M is reflected by the spherical approximate region R of the lens L to be measured, and follows the same path as that at the time of incidence, and sequentially passes through the opening 20a of the optical diaphragm 20, the objective lens 18 and the collimator 16, and further. The light passes through the half mirror 14 and is condensed on the CCD image sensor 26 a of the light receiving unit 26.

Further, in step S 7, the lens L 22 and the lens L to be measured are rotated around the optical axis A of the measurement light M by the rotation stage 24. As described above, since the lens holder 22 holds the lens L to be measured so that the center of the edge portion K coincides with the optical axis A of the measurement light M, the lens L to be measured is supported by the rotary stage 24. It rotates around a rotation axis passing through the center of the part K.
At this time, as shown in FIG. 5, the optical axis G1 of the lens L to be measured passing through the center of the optical surface of the lens L to be measured and the center G2 of the edge portion K of the lens L to be measured do not match. If there is a decentering amount ΔW, the lens L to be measured rotates around a rotation axis that is set in the vicinity of the optical axis G1 of the lens L to be measured and substantially parallel to the optical axis G1. As the lens L to be measured rotates, the optical axis G1 of the lens L to be measured rotates around the rotation axis passing through the center G2 of the edge portion K. Along with this, the reflected light of the measurement light M collected on the CCD image sensor 26 a of the light receiving unit 26 also rotates around the optical axis A of the measurement light M.

  In subsequent step S8, the arithmetic unit 28 decenters the optical axis G1 of the lens L to be measured with respect to the center G2 of the edge portion K of the lens L to be measured as the rotation axis based on the signal obtained by the light receiving unit 26. The quantity ΔW is measured. If the amount of eccentricity ΔW is 0, the condensing point on the CCD image sensor 26a of the light receiving unit 26 by the reflected light of the measuring light M moves even if the lens L to be measured is rotated around the rotation axis. As the eccentricity ΔW increases, the condensing point observed on the CCD image sensor 26a of the light receiving unit 26 when the lens L to be measured is rotated moves along a circumference having a large radius. Therefore, the amount of eccentricity ΔW of the lens L to be measured can be obtained by capturing the change in the position of the condensing point detected by the CCD image sensor 26a.

  In this way, by rotating the lens L to be measured around the rotation axis passing through the center G2 of the edge K while irradiating only the spherical approximate region R of the lens L to be measured, the spherical shape is greatly increased. Eccentricity measurement can be easily performed even with respect to a separated aspherical lens.

  If a variable diaphragm capable of adjusting the size of the opening 20a as shown in FIG. 6 is used as the optical diaphragm 20, it is not necessary to create an optical diaphragm corresponding to each lens L to be measured for each measurement. Thus, it is possible to easily measure various lenses L to be measured.

  In the first embodiment, the arithmetic unit 28 connected to the light receiving unit 26 not only constitutes a measuring unit that measures the eccentricity, but also approximates the spherical approximation area based on the design equation of the lens L to be measured. However, the spherical approximation area may be calculated by another computer or the like independent of the arithmetic unit 28, separately from the measurement means.

Embodiment 2
FIG. 7 shows the configuration of the eccentricity measuring apparatus 30 according to the second embodiment. This eccentricity measuring device 30 is the same as the eccentricity measuring device 10 according to the first embodiment shown in FIG. 1, but instead of the optical diaphragm 20 arranged on the optical axis A of the measuring light M, the optical of the lens L to be measured. A mask 32 is formed on the surface, and other members are the same as those in the first embodiment.
The mask 32 is made of a light-shielding material, and is formed such that only the spherical approximate region R is exposed by masking portions other than the spherical approximate region R on the optical surface of the lens L to be measured. The mask 32 is formed by sticking a sheet-like member made of a light-shielding material on the optical surface of the lens L to be measured, or by laminating a thin film made of a light-shielding material on the optical surface of the lens L to be measured. can do.
Even with such a configuration, it is possible to irradiate the measurement light M only to the spherical approximate region R of the lens L to be measured, and the same effects as those of the first embodiment can be obtained.

  In the second embodiment, the lens L to be measured is irradiated with the measuring light M by the annular illumination method, and the eccentricity measurement is similarly performed in a plurality of regions of the lens L to be measured by masking. The inclination of the shaft can also be measured.

  In addition, instead of the optical aperture 20 in the first embodiment and the mask 32 in the second embodiment, the objective lens 18 having a transmission region in which the measurement light M is irradiated only to the spherical approximate region R of the lens L to be measured. Can also be created. Even if such an objective lens 18 is used, as in the first and second embodiments, it is possible to easily perform decentration measurement with respect to an aspheric lens greatly deviating from the spherical shape.

DESCRIPTION OF SYMBOLS 10, 30 Eccentricity measuring device 12 Light source 14 Half mirror 16 Collimator 18 Objective lens 20 Optical aperture 20a Opening part 22 Lens holder 24 Rotating stage 26 Light receiving part 26a CCD image sensor 28 Arithmetic unit 32 Mask

Claims (10)

A method for measuring the amount of eccentricity of a lens to be measured having at least a part of an aspheric surface,
Based on the design equation of the lens to be measured, calculate a spherical approximate area approximated to a part of the sphere from the apex of the lens to be measured,
Rotating the lens to be measured around a rotation axis set in the vicinity of the optical axis of the lens to be measured and substantially parallel to the optical axis;
Irradiate measurement light only to the spherical approximate region of the lens to be measured,
An aspherical lens comprising: an aspheric lens that measures an eccentric amount of the optical axis of the lens to be measured with respect to the rotation axis by detecting reflected light of the measurement light that is reflected from the spherical approximate region of the lens to be measured. Eccentricity measuring method.   The method for measuring the eccentricity of an aspherical lens according to claim 1, wherein the measurement light is irradiated only on the spherical approximate region by using an optical aperture having an opening.   The decentering measurement method for an aspherical lens according to claim 1, wherein the measurement light is irradiated only on the spherical approximate region by masking a surface of the lens to be measured. The lens to be measured has an edge portion for positioning,
The eccentricity measurement method of the aspherical lens according to any one of claims 1 to 3, wherein the rotation shaft is set so as to pass through a center of the edge portion. An apparatus for measuring the amount of eccentricity of a lens to be measured having at least a part of an aspheric surface,
Calculating means for calculating a spherical approximate area approximated to a part of a spherical surface from the apex of the measured lens based on a design formula of the measured lens;
Rotating means for rotating the lens to be measured around a rotation axis set in the vicinity of the optical axis of the lens to be measured and substantially parallel to the optical axis;
Irradiating means for irradiating measuring light only to the spherical approximate region of the lens to be measured;
Measuring means for measuring the amount of eccentricity of the optical axis of the lens to be measured with respect to the rotation axis by detecting the reflected light of the measuring light reflected by the spherical approximate region of the lens to be measured. An aspherical lens eccentricity measuring device. The irradiation means includes
A light source;
An objective lens for irradiating light emitted from the light source toward the lens to be measured at a predetermined irradiation angle;
The aspherical lens eccentricity measuring device according to claim 5, further comprising: an optical aperture disposed between the objective lens and the lens to be measured and having an opening.   The aspherical lens eccentricity measuring apparatus according to claim 6, wherein the optical aperture has an opening having a size corresponding to the spherical approximate region of the lens to be measured calculated by the calculating unit.   The aspherical lens eccentricity measuring apparatus according to claim 7, wherein the optical aperture is a variable aperture capable of adjusting an opening size. The irradiation means includes
A light source;
An objective lens for irradiating light emitted from the light source toward the lens to be measured at a predetermined irradiation angle;
The aspherical lens eccentricity measuring device according to claim 5, further comprising: a light shielding mask formed on a surface of the lens to be measured. The lens to be measured has an edge portion for positioning,
The aspherical lens eccentricity measuring apparatus according to any one of claims 5 to 9, wherein the rotating means sets the rotating shaft so as to pass through a center of the edge portion.

Images