JP2013148436A - Wavefront aberration measuring apparatus and method for manufacturing lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavefront aberration measuring apparatus capable of performing accurate wavefront aberration measurement.SOLUTION: A wavefront aberration measuring apparatus 1 includes: a relay optical system 31 for receiving light passed through a test lens 10 and converting the received light into parallel light; a wavefront sensor 41 for dividing and detecting the parallel light from the relay optical system 31; an analyzer 52 for finding out a wavefront aberration of the test lens 10 on the basis of a detection signal of the light divided and detected by the wavefront sensor 41; and a driving device 46 for moving the wavefront sensor 41 along an optical axis so that a microlens array 42 of the wavefront sensor 41 is located on a position conjugate with an exit pupil 11 of the test lens 10.

Description

The present invention relates to a wavefront aberration measuring apparatus used for measuring the wavefront aberration of a lens to be inspected. The present invention also relates to a lens manufacturing method using the wavefront aberration measuring apparatus.

A Shack-Hartmann sensor is known as a wavefront measurement method. For example, “4th Pencil of Light” written by Tatsuo Tsuruta (New Technology Communications, 1997, p. 212) has a description as a typical example of a wavefront measuring sensor.

In such a wavefront aberration measuring apparatus, the light beams divided by the openings of the plurality of microlenses are respectively condensed on the image pickup device and become spot light. This spot light is detected by the image sensor, and the analyzer determines the spot light detection position to measure the inclination of the wavefront. It is desirable that the plurality of microlenses (microlens array) coincide with the exit pupil of the test lens. However, in the case of a photographic lens, the position of the exit pupil differs depending on the lens configuration and the position of the stop.

JP 2003-121300 A

If the microlens array is not arranged at a position conjugate with the exit pupil of the test lens, the exit pupil image will be blurred, so that the light that should be incident on each microlens is mixed and incident on the adjacent microlens. . Therefore, the measurement accuracy of wavefront aberration with respect to the lens to be measured is lowered. In particular, in measurement of the wavefront aberration of the lens to be examined due to off-axis oblique incidence, the measurement accuracy is significantly reduced.

The present invention has been made in view of such problems, and an object of the present invention is to provide a wavefront aberration measuring apparatus capable of performing accurate wavefront aberration measurement and a method of manufacturing a lens using the same.

In order to achieve such an object, according to an embodiment illustrating the present invention, a relay optical system that receives light that has passed through the lens to be measured and converts it into parallel light, and a parallel light from the relay optical system is divided. A wavefront sensor to detect, a calculation unit for obtaining a wavefront aberration of the lens to be detected based on a detection signal of light divided and detected by the wavefront sensor, and a position conjugate with an exit pupil of the lens to be tested. There is provided a wavefront aberration measuring apparatus including a drive unit that moves the wavefront sensor along an optical axis so that the wavefront sensor is located.

According to another aspect of the present invention, the wavefront aberration of the test lens is measured using the wavefront aberration measuring apparatus described above, and the test lens is inspected based on the measurement result of the wavefront aberration. A method for manufacturing the lens is provided.

  According to the present invention, accurate wavefront aberration measurement can be performed.

It is a schematic block diagram of a wavefront aberration measuring device. It is an enlarged view of a wavefront aberration measuring apparatus. It is an enlarged view of the wavefront aberration measuring apparatus when a test lens is a single lens. (A) is a front view of the microlens array in a 1st modification, (b) is a side view of a microlens array, (c) is explanatory drawing which shows the position of spot light. (A) is a front view of the microlens array in a 2nd modification, (b) is a side view of a microlens array, (c) is explanatory drawing which shows the position of spotlight. It is a flowchart which shows the manufacturing method of a lens.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a wavefront aberration measuring apparatus 1 according to this embodiment. In the present embodiment, a description will be given assuming that the direction perpendicular to the paper surface of FIG. 1 is the x direction, the vertical direction of FIG. 1 is the y direction, and the horizontal direction of FIG. The wavefront aberration measuring apparatus 1 of this embodiment is an apparatus for measuring the wavefront aberration of the lens 10 to be examined, and includes an illumination unit 20, a detection unit 30, a data storage device 51, and an analysis device 52. Composed.
The illumination unit 20 includes a fiber 21 and a collimator lens 23 and illuminates the lens 10 to be examined. The fiber 21 guides light emitted from a light source (not shown) to the collimator lens 23. A stop 22 having a predetermined diameter is provided at the exit end of the fiber 21. The collimator lens 23 converts the light emitted from the fiber 21 into parallel light and guides it to the test lens 10.

The test lens 10 collects the parallel light emitted from the illumination unit 20 and forms an image of the diaphragm 22 (hereinafter, appropriately referred to as diaphragm images Ia and Ib). The diverging light from the aperture image Ia formed through the lens 10 is detected by the detection unit 30. 1 and 2 includes a lens barrel and a plurality of lens components accommodated in the lens barrel.

The detection unit 30 includes a relay optical system 31 and a wavefront sensor 41. As shown in FIG. 2, the relay optical system 31 includes an objective lens 32, a first relay lens 34, and a second relay lens 35, and makes divergent light from the aperture image Ia parallel light. Wavefront sensor 4
Lead to one. The objective lens 32 receives the divergent light from the aperture image Ia and guides the divergent light to the first relay lens 34 and the second relay lens 35 as parallel light. The first relay lens 34 and the second relay lens 35 relay the parallel light from the objective lens 32 and guide it to the wavefront sensor 41. At this time, the first relay lens 34 condenses the parallel light from the objective lens 32 to form the aperture image Ib, and the second relay lens 35 converts the divergent light from the aperture image Ib into the microlens array 42 and the like. The parallel light expanded according to the size of the light is guided to the wavefront sensor 41. Note that the detection unit 30 uses a focus detection device (not shown) so that the focal point of the lens 10 to be examined and the focus of the objective lens 32 coincide with each other (that is, the in-focus state with respect to the aperture image Ia). To be)
It is assumed that the position has been adjusted.

As shown in FIG. 2, the wavefront sensor 41 includes a microlens array 42 and a first image sensor 4.
3, a mirror 44, and a second image sensor 45. Microlens array 4
2 is composed of a plurality of microlenses arranged two-dimensionally in a plane perpendicular to the optical axis (in the xy plane), and is arranged at a position conjugate with the exit pupil 11 of the lens 10 to be examined. The microlens array 42 divides and collects the parallel light from the relay optical system 31 by a plurality of microlenses, and places a plurality of spot lights (aperture images) (according to the number of microlenses) on the first image sensor 43. Form. The first image sensor 43 photoelectrically converts the spot light formed on the imaging surface and outputs a detection signal to the data storage device 51. The microlens array 42 and the first image sensor 4
3 is integrally configured, and a plurality of light receiving elements (pixels) are arranged for each region corresponding to one microlens on the first imaging element 43. Further, the first image sensor 43 and the second image sensor 45 include a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS).
emiconductor) is used.

The mirror 44 is provided so that it can be inserted into and removed from the optical path between the relay optical system 31 and the microlens array 42. In a state where the mirror 44 is removed from the optical path, the parallel light from the relay optical system 31 is guided to the microlens array 42, and as shown in FIG. 2, the relay optical system is inserted in the state where the mirror 44 is inserted on the optical path. The parallel light from 31 is guided to the second image sensor 45. The second imaging element 45 is arranged at a position conjugate with the exit pupil 11 of the lens 10 to be tested, and reflects the light (exit pupil relay image Rb) reflected from the relay optical system 31 by the mirror 44 and reaching the imaging surface. Photoelectric conversion is performed, and a detection signal is output to the data storage device 51. That is, with the mirror 44 inserted in the optical path, the exit pupil 11 of the test lens 10, the exit pupil 33 of the objective lens 32, and the second imaging element 4
The exit pupil relay image Rb at 5 is conjugate. On the other hand, in a state where the mirror 44 is removed from the optical path, the exit pupil 11 of the test lens 10, the exit pupil 33 of the objective lens 32, and the relay image Ra of the exit pupil of the microlens array 42 are conjugate.

The data storage device 51 stores spot light detection data (detection signal) input from the first image sensor 43 and sends it to the analysis device 52. The data storage device 51 includes the second image sensor 4.
The detection data (detection signal) of the light (exit pupil relay image Rb) input from 5 is stored and sent to the analyzer 52. The analysis device 52 obtains the inclination of the wavefront of the parallel light from the relay optical system 31 based on the spot light detection data sent from the data storage device 51, and analyzes the wavefront aberration of the lens 10 to be examined. Further, the analyzing device 52 receives light (from the data storage device 51).
Based on the detection data of the relay image Rb) of the exit pupil, the shape of the exit pupil 11 of the test lens 10 is obtained, and the pupil shape is analyzed.

The wavefront sensor 41 is provided with a driving device 46 that moves the wavefront sensor 41 along the optical axis. The driving device 46 includes a support member (not shown) that supports the wavefront sensor 41 so as to be slidable, a motor (not shown) that drives the wavefront sensor 41 together with the support member, and the like. The wavefront sensor 41 is moved along the optical axis so that the microlens array 42 is positioned at a position conjugate with the exit pupil 11. The exit pupil 11 of the lens 10 to be examined
The position conjugate with the data is calculated in advance from the design data of the lens 10 to be examined, and the data storage device 51.
Is remembered.

In the wavefront aberration measuring apparatus 1 configured as described above, light emitted from a light source (not shown) is guided to the collimator lens 23 by the fiber 21 of the illumination unit 20 and becomes parallel light by the collimator lens 23. And reaches the lens 10 to be examined. The parallel light transmitted through the test lens 10 is condensed to form a diaphragm image Ia, and divergent light from the diaphragm image Ia reaches the detection unit 30. The divergent light from the aperture image Ia that has reached the detection unit 30 is guided to the wavefront sensor 41 as parallel light by the relay optical system 31.

In a state where the mirror 44 of the wavefront sensor 41 is removed from the optical path, the parallel light from the relay optical system 31 is guided to the microlens array 42 and is divided and condensed by the plurality of microlenses, and then on the first image sensor 43. A plurality of spot lights (aperture images) are formed (according to the number of microlenses). The first image sensor 43 photoelectrically converts the spot light formed on the imaging surface,
A detection signal is output to the data storage device 51. The data storage device 51 stores spot light detection data (detection signal) input from the first image sensor 43 and sends it to the analysis device 52. The analysis device 52 obtains the inclination of the wavefront of the parallel light from the relay optical system 31 based on the spot light detection data sent from the data storage device 51, and analyzes the wavefront aberration of the lens 10 to be examined. Note that the spot light formed by the microlens array 42 is shifted in a direction perpendicular to the optical axis (normal line of the incident wavefront) in accordance with wavefront aberration, so that the spot light detected by the first image sensor 43 is From the position (pixel position), the inclination of the wavefront of the parallel light divided by the plurality of microlenses can be obtained.

On the other hand, in a state where the mirror 44 is inserted on the optical path, the parallel light from the relay optical system 31 is reflected by the mirror 44 and reaches the second image sensor 45. The second image sensor 45 photoelectrically converts the light (exit pupil relay image Rb) that has reached the imaging surface, and outputs a detection signal to the data storage device 51.
The data storage device 51 stores detection data (detection signal) of the light (exit pupil relay image Rb) input from the second image sensor 45 and sends it to the analysis device 52. Based on the detection data of the light (exit pupil relay image Rb) sent from the data storage device 51, the analyzer 52 detects the lens 1 to be examined.
The shape of the zero exit pupil 11 is obtained, and the pupil shape is analyzed.

When the position of the exit pupil changes depending on the type of the test lens, the position of the exit pupil relay image is also in the optical axis direction (the exit pupil relay image Ra in the microlens array 42 is in the z direction, the exit from the second image sensor 45). The pupil relay image Rb changes in the y direction). In the present embodiment, since the wavefront sensor 41 can be moved along the optical axis by the driving device 46, the position is conjugated with the exit pupil of the test lens corresponding to the position change of the exit pupil of the test lens. The position of the wavefront sensor 41 can be adjusted.

FIG. 3 shows the arrangement of the wavefront sensor 41 with respect to the lens 15 to be measured which is composed of a single lens. The position of the exit pupil 16 of the test lens 15 composed of a single lens is different from the position of the exit pupil 11 of the test lens 10 composed of a plurality of lenses. In such a case, the wavefront sensor 41 (test lens made up of a plurality of lenses) is placed by the drive device 46 so that the microlens array 42 is positioned at a position conjugate with the exit pupil 16 of the test lens 15 made up of a single lens. Move along the optical axis (in the plus z direction relative to 10). Thereby, the position of the relay image Ra of the exit pupil coincides with the position of the microlens array 42, and the relay image Ra of the exit pupil forms an image on the microlens array 42 without blurring. As a result, the wavefront aberration can be measured with high accuracy.

At this time, the second image sensor 45 is also positioned at a position conjugate with the exit pupil 16 of the lens 15 to be measured, which is a single lens. That is, in the state where the mirror 44 is inserted in the optical path, the test lens 1
5, the exit pupil 33 of the objective lens 32, and the relay image Rb of the exit pupil of the second image sensor 45 are conjugate. On the other hand, with the mirror 44 removed from the optical path, the test lens 1
5, the exit pupil 33 of the objective lens 32, and the relay image Ra of the exit pupil in the microlens array 42 are conjugate. Further, the conjugate positions of the test lenses 10 and 15 with the exit pupils 11 and 16 are stored in the data storage device 51, and each target (stored in the data storage device 51) is stored by a control device (not shown). The operation of the driving device 46 is controlled so that the microlens array 42 is positioned at a position conjugate with the exit pupils 11 and 16 of the test lenses 10 and 15.

Thus, according to the present embodiment, the drive device that moves the wavefront sensor 41 along the optical axis so that the wavefront sensor 41 is positioned at a position conjugate with the exit pupils 11 and 16 of the test lenses 10 and 15. Since 46 is provided, accurate wavefront aberration can be measured regardless of the position of the exit pupil of the lens to be examined. In the case of the test lens 15 made of a single lens, the exit pupil 16 is located on the lens surface, but the position of the exit pupil 16 varies greatly depending on the focal length of the test lens 15. Even in such a case, according to the present embodiment, the measurement position can be corrected with respect to the change of the exit pupil 16.

At this time, the driving device 46 moves the wavefront sensor 41 along the optical axis so that the microlens array 42 is positioned at a position conjugate with the exit pupils 11 and 16 of the test lenses 10 and 15. Accurate wavefront aberration can be measured.

In the above-described embodiment, the operation of the driving device 46 is controlled by a control device (not shown) so that the microlens array 42 is positioned at a position conjugate with the exit pupils 11 and 16 of the test lenses 10 and 15. However, it is not limited to this. For example, the drive device 4 is manually operated.
6 may be activated. Further, the position of the microlens array 42 where the spot light does not move on the first image sensor 43 even if the test lenses 10 and 15 are tilted with respect to the optical axis is determined as the test lens 1.
You may make it obtain | require as a conjugate position with the exit pupils 11 and 16 of 0,15.

In the above-described embodiment, in order to prevent the formation of spot light greatly deviated on the first image sensor 43, even if a limiting aperture is provided at the position where the aperture image Ib is formed in the relay optical system 31. Good.

In the above-described embodiment, at least one transmittance of the plurality of microlenses (microlens array 42) may be different from other transmittances. In the conventional Shack-Hartmann type sensor, the shape of the minute openings of the plurality of microlenses constituting the microlens array is generally circular or quadrangular. Further, the transmittance of the conventional microlens is constant, and each microlens is colorless and transparent except in the case of surface reflection.

A conventional microlens uses a convex lens having a focal length of 10 mm or less, and the microscopic apertures of each microlens are arranged in a plane perpendicular to the optical axis. The diameter of the microlens corresponding to the size of the minute aperture varies depending on the size to be divided, but is generally 1 mm or less.
Therefore, as a conventional manufacturing method, for example, as described in Japanese Patent No. 4296679, a method of manufacturing a microlens array using a photoresist as an etching mask is known.

In the conventional microlens array, wavefront sensor, and wavefront aberration measuring apparatus, the light beams divided by the openings of the plurality of microlenses are respectively condensed on the image pickup device to become spot light. When the position of the spot light is detected by the imaging device, but the spot light position shift (position shift in the direction perpendicular to the optical axis) exceeds half of the interval between the adjacent micro lenses, the spot light of the micro lens is detected. This makes it impossible to determine whether the light is spot light of an adjacent microlens, which causes erroneous measurement. For example, if the distance between the microlenses is 0.2 mm, the discriminable amount of spot light displacement is 0.1 mm. Thus, the detection range of the wavefront inclination is limited by the discriminable positional deviation amount.

Therefore, a modified example of the microlens array will be described. As shown in FIG. 4A, the microlens array 62 according to the first modification includes a plurality of microlenses L11 to L99 having positive refractive power. Here, the micro lens in the i-th row (i is a natural number) from the top and j-th column (j is a natural number) from the left in FIG. That is, the first
The microlens array 62 according to the modified example is composed of microlenses L11 to L99 having 9 rows and 9 columns arranged two-dimensionally in a plane perpendicular to the optical axis. Note that the number of microlenses is not limited to this example, and it is desirable that the number of microlenses is made up of a larger number of microlenses. For example, as 100 rows and 100 columns, the light flux is condensed in a narrower range. To be configured.

Each of the microlenses L11 to L99 has, for example, a focal length of 10 mm and an opening of 0.2 mm ×
A 0.2 mm one is used. The micro lens L55 in the fifth row from the top and the fifth column from the left is
Located in the center of the microlens array 62, the transmittance is lower than other microlenses. The micro lens L55 is provided with a neutral density filter, for example, having a transmittance of 50.
% Is set.

In the microlens array 62 configured as described above, as shown in FIG. 4B, the parallel light from the relay optical system 31 is guided to the microlens array 62 and divided and collected by the plurality of microlenses L11 to L99. A plurality of spot lights are formed on the first image sensor 43 by being irradiated. The first image sensor 43 photoelectrically converts the spot light formed on the imaging surface and outputs a detection signal to the data storage device 51. The data storage device 51 stores spot light detection data (detection signal) input from the first image sensor 43 and sends it to the analysis device 52. The analysis device 52 obtains the inclination of the wavefront of the parallel light from the relay optical system 31 based on the spot light detection data sent from the data storage device 51, and analyzes the wavefront aberration of the lens 10 to be examined.

At this time, since the microlens L55 in the fifth row from the top and the fifth column from the left has lower transmittance than the other microlenses, the spot light S5 collected by the microlens L55.
5 (see FIG. 4B and FIG. 4C) is a microlens L45, L adjacent to this.
It becomes darker than the spot lights S45 and S65 collected by 65. Therefore, the analyzer 5
2 or the like, among the plurality of microlenses L11 to L99, the central microlens L
The spot light S55 collected by 55 can be identified.

Thereby, even when a plurality of spot lights are detected in an area corresponding to one micro lens in the first image sensor 43, the spot light S55 collected by the central micro lens L55 is used as a reference. It becomes possible to identify which of the plurality of microlenses L11 to L99 is the spot light collected by each microlens. For example, the spot light S65 collected by the micro lens L65 in the sixth row from the top and the fifth column from the left, and the spot light S75 collected by the micro lens L75 in the seventh row from the top and the fifth column from the left. (Refer to FIG. 4B and FIG. 4C).

As described above, according to the first modification, the detection range of the spot light and the detection range of the inclination of the wavefront can be expanded, so that more accurate wavefront aberration can be measured.

Next, a second modification of the microlens array will be described. As shown in FIG. 5A, the microlens array 72 according to the second modification includes a plurality of microlenses L11 to L99 similar to those in the first modification. As in the case of the first modification,
In FIG. 5A, the micro lens in the i-th row (i is a natural number) from the top and the j-th column (j is a natural number) from the left is Lij.

In the second modified example, the microlens L35 in the third row from the top and the fifth column from the left, and 7 from the top
The microlens L75 in the fifth row from the left has a lower transmittance than the other microlenses. The two microlenses L35 and L75 are provided with a neutral density filter, and the transmittance is set to 50%, for example.

In the microlens array 72 configured as described above, as shown in FIG. 5B, the parallel light from the relay optical system 31 is guided to the microlens array 72 and divided and collected by the plurality of microlenses L11 to L99. A plurality of spot lights are formed on the first image sensor 43 by being irradiated. The first image sensor 43 photoelectrically converts the spot light formed on the imaging surface and outputs a detection signal to the data storage device 51. Then, the same processing as in the case of the first modification is performed.

At this time, the micro lens L35 in the third row from the top and the fifth column from the left has lower transmittance than the other micro lenses, and therefore the spot light S3 collected by the micro lens L35.
5 (see FIGS. 5B and 5C) is darker than the spot light S45 collected by the microlens L45 adjacent thereto. Similarly, since the microlens L75 in the seventh row from the top and the fifth column from the left has lower transmittance than the other microlenses, the spot light S75 collected by the microlens L75 (FIG. 5B). And (refer FIG.5 (c)) becomes darker than the spot light S65 condensed by the micro lens L65 adjacent to this. Therefore, in the analyzer 52 and the like, the spot lights S35 and S7 collected by the microlenses L35 and L75 having a low transmittance among the plurality of microlenses L11 to L99.
5 can be identified.

Thereby, even when a plurality of spot lights are detected in a region corresponding to one microlens in the first image sensor 43, the microlenses L35 and L75 having low transmittance are provided.
A plurality of microlenses L11 with reference to the spot lights S35 and S75 collected by
It becomes possible to identify each of the microlenses L99 to L99 to collect the spot light. For example, the micro lens L6 in the sixth row from the top and the fifth column from the left
5 and the spot light S75 condensed by the micro lens L75 in the seventh row from the top and the fifth column from the left (FIG. 5B and FIG. 5).
see c)).

Thus, according to the second modification, the detection range of the spot light and the detection range of the inclination of the wavefront can be expanded, so that more accurate wavefront aberration can be measured. Note that the number of microlenses having low transmittance is not limited to two, and may be larger. In this case, it is preferable to arrange the microlenses having low transmittance so as not to be adjacent to each other.

Next, an outline of a method for manufacturing a lens (lens system) having a plurality of lens components will be described with reference to the flowchart shown in FIG. First, a plurality of lens parts are arranged in a lens barrel, and a lens system is assembled (step ST101). Next, the wavefront aberration of the assembled lens system (that is, the wavefront aberration of the test lens) is measured using the wavefront aberration measuring apparatus 1 shown in FIG. 1 described above (step ST102). Then, the lens system is inspected by determining the quality of the assembled lens system based on the measurement result of the wavefront aberration (step ST1).
03).

According to such a manufacturing method, since the wavefront aberration can be accurately measured using the wavefront aberration measuring apparatus 1 described above, the manufacturing quality of the lens (lens system) can be improved. In the case of a single lens, the same manufacturing can be performed. That is, the lens may be a lens system composed of a plurality of lens parts or a single lens.

DESCRIPTION OF SYMBOLS 1 Wavefront aberration measuring apparatus 10 Test lens 11 Exit pupil 15 Test lens 16 Exit pupil 30 Detection part 31 Relay optical system 41 Wavefront sensor 42 Micro lens array 43 1st image pick-up element 44 Mirror 45 2nd image pick-up element 46 Drive device 51 Data Storage device 52 Analysis device (calculation unit)
Ia, Ib Aperture image Ra, Rb Relay image

Claims (3)

A relay optical system that receives light that has passed through the test lens and converts it into parallel light; and
A wavefront sensor for dividing and detecting parallel light from the relay optical system;
Based on the detection signal of the light detected by being divided by the wavefront sensor, a calculation unit for obtaining the wavefront aberration of the lens to be measured;
A wavefront aberration measuring apparatus comprising: a drive unit that moves the wavefront sensor along an optical axis so that the wavefront sensor is positioned at a position conjugate with an exit pupil of the lens to be examined. . The wavefront sensor includes a microlens array that divides and collects parallel light from the relay optical system, and an image sensor that detects light collected by the microlens array,
2. The wavefront according to claim 1, wherein the driving unit moves the wavefront sensor along an optical axis so that the microlens array is positioned at a position conjugate with an exit pupil of the lens to be examined. Aberration measuring device. The wavefront aberration of the lens to be measured is measured using the wavefront aberration measuring device according to claim 1 or 2,
A method for manufacturing a lens, comprising: inspecting the test lens based on a measurement result of the wavefront aberration.

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