JP7404005B2 - Eccentricity measuring device and eccentricity measuring method - Google Patents

Description

The present invention relates to an eccentricity measuring device and an eccentricity measuring method.

Conventionally, an autocollimation method has been used to measure eccentricity of a lens system such as an assembled lens including a plurality of lenses. In an eccentricity measuring device that uses the autocollimation method, the movable part including the light source is illuminated in order to irradiate the measurement light emitted from the light source onto the apparent spherical center position of each surface to be measured of the lens system, which is the object to be measured. It is necessary to drive along the axial direction. If there is wobbling in the stage that drives the movable part, the relative positions of the movable part and the object will shift, making it impossible to measure each test surface under the same conditions.

Patent Document 1 discloses a technique for reducing the influence of stage wobbling by rotating a subject. According to this technique, each test surface can be evaluated using the same standard by correcting the measurement results based on the center position of the rotation locus drawn by the measurement light when the test object is rotated.

Japanese Patent Application Publication No. 5-312670

However, with the technique of Patent Document 1, measurement was not efficient because it was necessary to rotate the object on each test surface.

The present invention has been made in view of the above, and an object of the present invention is to provide an eccentricity measuring device and an eccentricity measuring method that are efficient in measurement.

In order to solve the above-mentioned problems and achieve the objects, an eccentricity measuring device according to one aspect of the present invention includes a focusing optical system that focuses light emitted from a light source onto an optical axis, and a focusing optical system that focuses light emitted from a light source onto an optical axis. a pinhole plate in which a pinhole is formed that selectively transmits the light focused by the focusing optical system, and the light transmitted through the pinhole is split into a reference light and a measurement light. a first optical system that retroactively reflects the reference light; a second optical system that irradiates the measurement light onto the object and collects the return light from the object; an imaging unit that images the reference light guided to the first optical system and the measurement light guided to the second optical system, the pinhole plate, the beam splitter, the first optical system, and A stage that moves the imaging unit along the optical axis.

Furthermore, the eccentricity measuring device according to one aspect of the present invention includes a shutter that can be inserted and removed on the optical path of the reference light.

Further, in the eccentricity measuring device according to one aspect of the present invention, the diameter of the pinhole is larger than the Airy disk diameter determined by the wavelength of the light emitted from the light source and the optical characteristics of the condensing optical system.

Further, the eccentricity measuring device according to one aspect of the present invention includes a drive unit that drives the pinhole plate in a direction perpendicular to the optical axis, and the pinhole is configured to match the wavelength of light emitted from a light source and the concentration of light. The first pinhole has a diameter larger than the Airy disk diameter determined by the optical characteristics of the optical system, and the second pinhole has a diameter smaller than or equal to the Airy disk diameter.

Further, in the eccentricity measuring method according to one aspect of the present invention, light emitted from a light source is focused on an optical axis by a focusing optical system, and a pinhole plate in which a pinhole is formed is aligned on the optical axis. The focusing optical system selectively transmits the focused light, the light transmitted through the pinhole is split into reference light and measurement light by a beam splitter, and the reference light is transmitted to the first optical system. The measurement light is retroreflected by a second optical system, and the return light from the test object is collected by irradiating the measurement light onto the test object, and the reference light is guided to the first optical system, and the reference light is guided to the first optical system. The measurement light guided to the second optical system is imaged by an imaging section, and the pinhole plate, the beam splitter, the first optical system, and the imaging section are moved along the optical axis by a stage. , calculating the eccentricity of the subject based on a plurality of imaging results of the subject imaged while moving the stage;

Further, in the eccentricity measuring method according to one aspect of the present invention, the pinhole is a first pin having a diameter larger than an Airy disk diameter determined by the wavelength of the light emitted from the light source and the optical characteristics of the condensing optical system. a second pinhole having a diameter equal to or less than the Airy disk diameter, and the reference light transmitted through the first pinhole and split by the beam splitter is formed on the imaging unit. A first spot center position is recorded, and a second spot center position formed on the imaging unit by the reference light transmitted through the second pinhole and split by the beam splitter is recorded as the first spot center position. Match the center position.

According to the present invention, it is possible to provide an eccentricity measuring device and an eccentricity measuring method that are efficient in measurement.

FIG. 1 is a schematic diagram showing the configuration of an eccentricity measuring device according to the first embodiment. FIG. 2 is a diagram for explaining the relationship between the position of the pinhole and the lens to be tested. FIG. 3 is a flowchart showing a process executed by the eccentricity measuring device shown in FIG. FIG. 4 is a diagram illustrating an example of an image captured by the imaging unit. FIG. 5 is a schematic diagram showing the configuration of an eccentricity measuring device according to the second embodiment. FIG. 6 is an enlarged view of the pinhole plate shown in FIG. 5 viewed from the point light source side. FIG. 7 is a flowchart showing a process executed by the eccentricity measuring device shown in FIG. FIG. 8 is a diagram showing how the first pinhole transmits light. FIG. 9 is a diagram showing a spot formed on the imaging unit by the reference light transmitted through the first pinhole and split by the beam splitter. FIG. 10 is a diagram showing how the second pinhole is arranged on the optical axis. FIG. 11 is a diagram showing a spot formed on the imaging unit by the reference light transmitted through the second pinhole and split by the beam splitter. FIG. 12 is a diagram showing how the second pinhole transmits light.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an eccentricity measuring device and an eccentricity measuring method according to the present invention will be described below with reference to the drawings. Note that the present invention is not limited to these embodiments. The present invention can be applied to eccentricity measuring devices and eccentricity measuring methods in general.

Furthermore, in the description of the drawings, the same or corresponding elements are given the same reference numerals as appropriate. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, etc. may differ from reality. Drawings may also include portions that differ in dimensional relationships and ratios.

(Embodiment 1)
[Configuration of eccentricity measuring device]
FIG. 1 is a schematic diagram showing the configuration of an eccentricity measuring device according to the first embodiment. As shown in FIG. 1, the eccentricity measuring device 1 according to the first embodiment includes a point light source 2 as a light source, a collimator lens 3, an axicon lens 4 as a condensing optical system, and a pinhole plate 5. , a beam splitter 6, a collimator lens 7 and a corner cube 8 as a first optical system, a shutter 9, a motor 10, an objective lens 11 as a second optical system, a relay lens 12, and an imaging section 13. and an automatic stage 14 as a stage. The eccentricity measuring device 1 is used to measure the eccentricity of a lens 20 to be examined as a subject.

The point light source 2 emits light of a predetermined wavelength. The point light source 2 may be, for example, a laser diode, but is not particularly limited.

The collimator lens 3 converts the light from the point light source 2 into substantially parallel light.

The axicon lens 4 focuses the light emitted from the point light source 2 and made into parallel light by the collimator lens 3 onto the optical axis O. The axicon lens 4 has a flat surface on the point light source 2 side, and a conical surface on the opposite side to the flat surface. Since the light transmitted through the axicon lens 4 is refracted at the same angle regardless of the distance from the central axis of the conical surface, it is focused in a line from the apex of the conical surface to a predetermined range on the optical axis O. be illuminated.

The pinhole plate 5 is arranged on the optical axis O. A pinhole 5a is formed in the pinhole plate 5, and selectively transmits the light condensed by the axicon lens 4. In other words, the pinhole plate 5 selectively transmits only the light focused at a predetermined position on the optical axis O out of the light focused in a line on the optical axis O by the axicon lens 4. . The diameter of the pinhole 5a is preferably larger than the Airy disk diameter determined by the wavelength of the light emitted from the point light source 2 and the optical characteristics of the axicon lens 4, and is, for example, twice the Airy disk diameter. Note that the optical characteristics of the axicon lens 4 refer to the refractive index of the axicon lens 4, the inclination angle of the conical surface of the axicon lens 4 with respect to the optical axis, and the like.

Furthermore, as the diameter of the pinhole 5a becomes larger, the depth of field becomes larger, making it impossible to separately measure test surfaces whose apparent spherical center positions are close to each other. Therefore, it is preferable that the diameter of the pinhole 5a is, for example, twice or less the diameter of the Airy disk.

The beam splitter 6 splits the light transmitted through the pinhole 5a into reference light and measurement light.

The collimator lens 7 converts the light from the beam splitter 6 into substantially parallel light.

The corner cube 8 reflects the reference light so as to trace it in the opposite direction to the optical axis incident on the corner cube 8 (retroreflection). The corner cube 8 reflects the reference light with a reflectance of 90% or more, for example. The reference light reflected by the corner cube 8 is focused on a point P that is conjugate with the pinhole 5a. However, instead of the collimator lens 7 and the corner cube 8 as the configuration that reflects the reference light, a configuration that retroactively reflects the reference light may be arranged. Specifically, for example, a combination of a convex lens and a plane mirror may be arranged.

The shutter 9 can be inserted into and removed from the optical path of the reference light. However, the eccentricity measuring device 1 may not include a shutter. In that case, a light shielding member may be appropriately placed in the optical path of the reference light.

The motor 10 drives the shutter 9 and inserts and removes the shutter 9 onto and from the optical path of the reference light.

The objective lens 11 irradiates the test lens 20 with the measurement light that has passed through the pinhole 5a and the beam splitter 6, and collects the return light from the test lens 20.

The relay lens 12 collects the reference light reflected by the corner cube 8 and the measurement light reflected by the test lens 20. The reference light and measurement light focused on a point P conjugate with the pinhole plate 5 form a spot image on the imaging section 13 by the relay lens 12 . However, if the imaging unit 13 can be placed directly at a point P that is mutually beneficial to the pinhole plate 5, the relay lens 12 may be omitted.

The imaging unit 13 images the reference light guided to the corner cube 8 and the measurement light guided to the test lens 20. The imaging unit 13 is, for example, a CCD (Charge Coupled Device) camera.

The automatic stage 14 moves a movable part 15 including a pinhole plate 5, a beam splitter 6, a collimator lens 7, a corner cube 8, a shutter 9, a motor 10, a relay lens 12, and an imaging section 13 along the optical axis O. It's a stage.

The test lens 20 reflects a part of the irradiated measurement light. The lens 20 to be tested consists of a plurality of lenses, and the eccentricity is usually determined after measuring all surfaces. Here, for the sake of simplicity, the test surfaces 20a, 20b, and 20c will be explained as an example. The test surfaces 20a, 20b, and 20c reflect a portion of the measurement light when irradiated with it. The light reflected from the test surfaces 20a, 20b, and 20c follows approximately the same optical path as the incident light, but it travels on a slightly different optical path depending on the amount of eccentricity of the test surfaces 20a, 20b, and 20c, and passes through the pinhole 5a. The light is focused on a conjugate point P. The lens 20 to be tested is usually coated with an antireflection coating to reduce reflectance at wavelengths in the visible light range. Therefore, the light intensity of the light reflected on the test surfaces 20a, 20b, and 20c is small.

[Pinhole position]
Next, the position of the pinhole 5a will be explained. FIG. 2 is a diagram for explaining the relationship between the position of the pinhole and the lens to be tested. As shown in FIG. 2, Z is the position of the pinhole 5a in the direction along the optical axis O. Further, let A be the distance from the pinhole 5a to the principal point of the objective lens 11, and let B be the distance from the principal point of the objective lens 11 to the apparent spherical center position P of the surface to be measured.

In the case of position Z=Z1 shown in FIG. 2(a), among the light condensed in a line on the optical axis O by the axicon lens 4, only the measurement light for which 1/A1+1/B1=1/F holds. This measurement light is transmitted through the pinhole 5a and focused on the apparent spherical center position P1 of the surface to be measured 20a. In other words, when the pinhole plate 5 is adjusted so that the position Z=Z1, the measurement light is irradiated so as to be focused on the apparent spherical center position P1 of the test surface 20a. As a result, a part of the measurement light is reflected by the surface to be measured 20a and enters the imaging section 13.

Next, in the case of position Z = Z2 shown in FIG. Only the light is transmitted through the pinhole plate 5, and this measurement light is focused on the apparent spherical center position P2 of the surface to be measured 20b. In other words, when the pinhole plate 5 is adjusted so that the position Z=Z2, the measurement light is irradiated so as to be focused on the apparent spherical center position P2 of the test surface 20b. As a result, a part of the measurement light is reflected by the surface to be measured 20b and enters the imaging section 13.

Next, in the case of the position Z=Z3 shown in FIG. Only the light is transmitted through the pinhole plate 5, and this measurement light is focused on the apparent spherical center position P3 of the surface to be measured 20c. In other words, when the pinhole plate 5 is adjusted so that the position Z=Z3, the measurement light is irradiated so as to be focused on the apparent spherical center position P3 of the surface to be measured 20c. As a result, a part of the measurement light is reflected by the surface to be measured 20c and enters the imaging section 13.

As explained above, by changing the position Z of the pinhole plate 5 in the direction along the optical axis O, out of the light condensed in a line on the optical axis O by the axicon lens 4, the By selecting the measurement light to be focused on the apparent spherical center position P1 to P3 of any one of the test surfaces 20a, 20b, or 20c, the reflected light from any one of the test surfaces 20a, 20b, or 20c can be It becomes possible to select and capture an image using the imaging unit 13.

Note that the apparent spherical center position is a spherical center position that takes into account the refraction of light in a lens located in front of the target surface to be measured (on the light source side). In other words, if there is a lens in front of the target surface to be measured, by irradiating light that focuses on the apparent spherical center position of the target surface to be measured, the measurement light will be refracted by the lens in front of it. Light can be focused on the actual spherical center position of the target surface to be inspected. The apparent spherical center position can be calculated from the radius of curvature of the target surface to be measured, the radius of curvature of each surface of the lens in front of it, the refractive index of each lens, and the interval between each surface.

[Eccentricity measurement method]
Next, a method for measuring eccentricity using the eccentricity measuring device 1 will be explained. FIG. 3 is a flowchart showing a process executed by the eccentricity measuring device shown in FIG. As shown in FIG. 3, the apparent spherical center position of each test surface (test surfaces 20a, 20b, 20c) of the test lens 20 is calculated (step S1). As described above, the apparent spherical center position of each test surface can be calculated by ray tracing or the like based on the design data of the test lens 20.

Subsequently, the variable i is set to 1 as an initial setting (step S2).

Then, it is determined whether i>N (step S3). Note that N is the number of surfaces to be tested of the lens 20 to be tested. The number of surfaces to be inspected will be explained here as three, but is not particularly limited.

If i>N is not satisfied (step S3: No), the movable part 15 is moved so that the measurement light that has passed through the pinhole plate 5 is focused on the apparent spherical center position of the i-th test surface ( Step S4).

Subsequently, the motor 10 is driven to retract the shutter 9 from the optical path of the reference light (step S5). Further, the shutter speed and the like of the imaging section 13 are adjusted according to the light intensity of the reference light.

Then, the spot center position of the reference light is recorded by the imaging unit 13 (step S6). At this time, both the reference light and the measurement light enter the imaging unit 13, but as described above, the reflectance of the corner cube 8 is 90% or more, while the Since the reflected light from the surface is sufficiently weak, only the reference light can be selectively observed by adjusting the shutter speed of the imaging unit 13 according to the brightness of the reference light.

Subsequently, the motor 10 is driven to insert the shutter 9 onto the optical path of the reference light (step S7). Further, the shutter speed and the like of the imaging section 13 are adjusted according to the light intensity of the measurement light.

Then, the spot center position of the measurement light is recorded by the imaging unit 13 (step S8). At this time, since the reference light is blocked by the shutter 9, only the measurement light can be selectively observed.

Thereafter, the variable i is incremented (i=i+1) (step S9), and the process returns to step S3 to repeat the process.

In step S3, if i>N (step S3: Yes), the apparent eccentricity of each test surface of the test lens 20 is calculated (step S10).

The actual eccentricity of each test surface of the test lens 20 is calculated (step S11).

FIG. 4 is a diagram illustrating an example of an image captured by the imaging unit. FIG. 4 shows an image Imi in which the reference light and measurement light respectively captured for the i-th test surface are displayed in a superimposed manner. As shown in FIG. 4, the spot center position PRi (Rxi, Ryi) of the reference light imaged on the i-th test surface by the imaging unit 13, and the spot center position PRi (Rxi, Ryi) of the reference light imaged on the i-th test surface. The spot center position PMi (Mxi, Myi) of the measurement light is recorded. Note that the reference light spot center position PRi (Rxi, Ryi) and the measurement light spot center position PMi (Mxi, Myi) represent positions on the imaging unit 13 in pixels.

[Spot light size]
Next, the size of the spot image on the imaging section 13 will be explained. Since the NA of the light transmitted through the axicon lens 4 is constant regardless of the position in the optical axis O direction, the size of the spot transmitted through the pinhole 5a (Airy disk diameter) is 1.22×λ/NA becomes. λ is the wavelength (nm) of the light emitted by the point light source 2, and the numerical aperture NA is NA=sin θ, where θ is the angle between the light refracted by the axicon lens 4 and the optical axis O. Since the size of the pinhole 5a is twice the diameter of the Airy disk, the entire light focused on the position where the pinhole 5a is arranged is transmitted through the pinhole 5a.

The light that has passed through the pinhole 5a is irradiated by the objective lens 11 so as to be focused on the apparent spherical center of the surface to be inspected, and a portion is reflected from the surface to be inspected. The light reflected on the test surface is focused near a point P that is conjugate with the pinhole 5a. At this time, the size of the spot formed by the objective lens 11 at the spherical center position of the surface to be measured is B/A times the Airy disk diameter. Then, the size of the spot that is reflected on the test surface and formed near the point P is further multiplied by A/B. Therefore, the measuring light is multiplied by 1 by reciprocating between it and the surface to be measured, and is focused to the same size as the Airy disk diameter. Further, the spot image on the imaging section 13 is further enlarged to an observation magnification determined by the focal length of the relay lens 12 and the position of the imaging section 13. As explained above, the size of the spot observed on the imaging unit 13 is the same regardless of the surface to be inspected.

Similarly, the spot size of the reference light is also doubled at point P by reciprocating.

[How to calculate eccentricity]
Next, a method of calculating the amount of eccentricity will be explained. Since the eccentricity is a lateral deviation of the spot of the measurement light caused by the lateral deviation of the surface to be measured, it is multiplied by A/B regardless of the incident conditions of the light incident on the surface to be measured. Further, the magnification on the imaging section 13 is further expanded to an observation magnification determined by the focal length of the relay lens 12 and the position of the imaging section 13, similarly to the spot image.

When the observation magnification is β, the apparent eccentricities Δxi and Δyi between the X-axis component and the Y-axis component on the i-th test surface can be expressed as follows.
Δxi=(Mxi-Rxi)×pixel size/(β×(A/B)×2)
Δyi=(Myi-Ryi)×pixel size/(β×(A/B)×2)
Note that in the case of reflection, the sensitivity is twice as high with respect to the inclination of the surface to be inspected, so it is necessary to divide by 2. Moreover, the pixel size represents the size of one pixel (pixel) of the imaging unit 13.

After calculating the apparent eccentricity of each test surface, the actual eccentricity of each test surface, the eccentricity of each lens, etc. can be calculated based on conventional eccentricity calculation algorithms, depending on the application. .

As explained above, according to the first embodiment, unlike the autocollimation method in which the light source is driven, the positional relationship between the point light source 2 and the test lens 20 does not change, so each test surface is inspected under the same conditions. can be evaluated. Therefore, since there is no need to rotate the lens 20 to be tested, the measurement becomes efficient. Furthermore, since there is no need for a configuration for rotationally driving the lens 20 to be tested, the apparatus can be simplified and the manufacturing cost of the apparatus can be suppressed.

(Embodiment 2)
FIG. 5 is a schematic diagram showing the configuration of an eccentricity measuring device according to the second embodiment. As shown in FIG. 5, the eccentricity measuring device 1A according to the second embodiment includes an XY stage 16A as a drive unit that drives the pinhole plate 5A in a direction orthogonal to the optical axis O. The configurations other than the pinhole plate 5A and the XY stage 16A are the same as in Embodiment 1, so the description will be omitted as appropriate.

FIG. 6 is an enlarged view of the pinhole plate shown in FIG. 5 viewed from the point light source side. As shown in FIG. 6, the pinhole plate 5A has a first pinhole 5Aa and a second pinhole 5Ab.

It is preferable that the first pinhole 5Aa has a diameter larger than the Airy disk diameter. When the diameter of the first pinhole 5Aa is larger than the Airy disk diameter, the entire light focused on the position where the pinhole plate 5A is arranged is transmitted through the first pinhole 5Aa. Furthermore, since the motorized stage 14 has running errors such as pitch, yaw, running parallelism, etc., even if a running error occurs, the entire light focused on the position where the pinhole plate 5A is placed is It is preferable that the light be transmitted through the first pinhole 5Aa. Specifically, the diameter of the first pinhole 5Aa is, for example, twice the diameter of the Airy disk.

It is assumed that the Airy disk diameter of the light transmitted through the axicon lens 4 is 50 μm, and that the diameter of the first pinhole 5Aa is 100 μm, which is twice the Airy disk diameter. At this time, assuming that the running error of the motorized stage 14 in the direction perpendicular to the optical axis is ±10 μm, (100 μm diameter of first pinhole 5Aa − 50 μm Airy disk diameter − running error 20 μm)/2 = 15 μm. Since there is a margin, even if the automatic stage 14 is moved, the entire light focused by the axicon lens 4 is transmitted through the first pinhole 5Aa. Therefore, it is possible to prevent the spot image from being missing.

The diameter of the second pinhole 5Ab is preferably equal to or smaller than the Airy disk diameter. The diameter of the second pinhole 5Ab is, for example, half the diameter of the Airy disk. The smaller the diameter of the second pinhole 5Ab, the smaller the depth of field, and the better the resolution of the surface to be inspected in the direction along the optical axis O. Furthermore, when the second pinhole 5Ab is smaller than the Airy disk diameter, light passes through the entire area of the second pinhole 5Ab, and the center of the spot image can be regarded as the center of the second pinhole 5Ab.

The XY stage 16A drives the pinhole plate 5A in a direction perpendicular to the optical axis O, and adjusts the positions of the optical axis O and the first pinhole and the second pinhole.

[Eccentricity measurement method]
Next, a method for measuring eccentricity using an eccentricity measuring device will be explained. FIG. 7 is a flowchart showing a process executed by the eccentricity measuring device shown in FIG. As shown in FIG. 7, after performing steps S1 to S5 in the same manner as in the first embodiment, the XY stage 16A is operated to place the first pinhole 5Aa on the optical axis O (step S21).

FIG. 8 is a diagram showing how the first pinhole transmits light. As shown in FIG. 8, when the first pinhole 5Aa is placed on the optical axis O, since the first pinhole 5Aa is sufficiently larger than the Airy disk diameter, the first pinhole 5Aa is located at the position where the first pinhole 5Aa is placed. The entire spot SP of the focused light is transmitted through the first pinhole 5Aa.

Then, using the imaging unit 13, the center position of the first spot formed on the imaging unit 13 by the reference light transmitted through the first pinhole 5Aa and split by the beam splitter 6 is recorded (step S22).

FIG. 9 is a diagram showing a spot formed on the imaging unit by the reference light transmitted through the first pinhole and split by the beam splitter. Since the entire spot SP in FIG. 8 is transmitted through the first pinhole 5Aa, as shown in FIG. 9, the spot SP1 formed on the imaging section 13 has a circular shape with no chipped outer periphery. Therefore, the first spot center position C1, which is the center of the spot SP1, coincides with the optical axis O of the reference light.

Next, the XY stage 16A is operated to place the second pinhole 5Ab on the optical axis O (step S23). FIG. 10 is a diagram showing how the second pinhole is arranged on the optical axis. As shown in FIG. 10, when the second pinhole 5Ab is placed on the optical axis O, the Airy disk diameter is larger than the second pinhole 5Ab, and the center of the second pinhole 5Ab and the optical axis O ( (center of spot SP) do not match.

FIG. 11 is a diagram showing a spot formed on the imaging unit by the reference light transmitted through the second pinhole and split by the beam splitter. The second spot center position, which is the center of a spot SP2 formed on the imaging unit 13 by the reference light transmitted through the second pinhole 5Ab and split by the beam splitter 6, is C2.

Thereafter, using the imaging unit 13, the second spot center position C2 formed on the imaging unit 13 by the reference light transmitted through the second pinhole 5Ab and split by the beam splitter 6 was recorded in step S22. It is made to coincide with the first spot center position C1 (step S24). Specifically, the amount of deviation of the second spot center position C2 from the first spot center position C1 is measured, and the XY stage 16A is moved to compensate for this amount of deviation. Then, since the first spot center position C1 and the optical axis O of the reference light match, the second spot center position C2 and the optical axis O of the reference light match.

FIG. 12 is a diagram showing how the second pinhole transmits light. When the second spot center position C2 and the optical axis O of the reference light coincide, the spot SP of the light focused on the center of the second pinhole 5Ab and the position where the second pinhole 5Ab is arranged. The center matches. As a result, when arranging the second pinhole 5Ab with a diameter smaller than the Airy disk diameter on the optical axis O, the center of the optical axis O and the center of the second pinhole 5Ab are misaligned, reducing measurement accuracy. This can be prevented.

Thereafter, steps S7 to S11 are performed in the same manner as in the first embodiment.

As explained above, according to the second embodiment, by performing measurement using light transmitted through the second pinhole 5Ab having a diameter equal to or smaller than the Airy disk diameter, the depth of field can be reduced, and the target object can be Only the test surface can be measured.

In addition, in the above-mentioned Embodiment 2, an example was described in which two pinholes (first pinhole 5Aa, second pinhole 5Ab) of different sizes are formed in the pinhole plate 5A. Not limited to. Instead of the pinhole plate 5A, a configuration capable of changing the diameter of the pinhole, such as an iris diaphragm or an electronically controlled diaphragm such as a liquid crystal diaphragm, may be arranged.

Further advantages and modifications can be easily deduced by those skilled in the art. Therefore, the broader aspects of the invention are not limited to the specific details and representative embodiments shown and described above. Accordingly, various changes may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

1, 1A Eccentricity measuring device 2 Point light source 3, 7 Collimator lens 4 Axicon lens 5, 5A Pinhole plate 5a Pinhole 5Aa First pinhole
5Ab second pinhole
6 Beam splitter 8 Corner cube 9 Shutter 10 Motor 11 Objective lens 12 Relay lens 13 Imaging section 14 Automatic stage 15 Movable section 16A XY stage 20 Test lens 20a, 20b, 20c Test surface

Claims (3)

a condensing optical system that condenses the light emitted from the light source onto the optical axis;
a pinhole plate arranged on the optical axis and having a pinhole formed therein that transmits the light collected by the focusing optical system;
a beam splitter that splits the light transmitted through the pinhole into a reference light and a measurement light;
a first optical system that retroactively reflects the reference light;
a second optical system that irradiates the measurement light onto the object and collects the return light from the object;
an imaging unit that images the reference light guided to the first optical system and the measurement light guided to the second optical system;
a stage for moving the pinhole plate, the beam splitter, the first optical system, and the imaging unit along the optical axis;
a drive unit that drives the pinhole plate in a direction perpendicular to the optical axis;
Equipped with
The pinhole is
a first pinhole having a diameter larger than an Airy disk diameter determined by the wavelength of the light emitted from the light source and the optical characteristics of the condensing optical system;
a second pinhole whose diameter is equal to or less than the Airy disk diameter;
including;
The drive unit is an eccentricity measuring device that adjusts the positions of the optical axis, the first pinhole, and the second pinhole . The eccentricity measuring device according to claim 1, further comprising a removable shutter on the optical path of the reference light. The light emitted from the light source is focused on the optical axis by a focusing optical system,
a first pinhole having a diameter larger than the Airy disk diameter determined by the wavelength of the light emitted from the light source and the optical characteristics of the condensing optical system; and a second pinhole having a diameter less than or equal to the Airy disk diameter; A pinhole plate in which a pinhole including a pinhole is formed is arranged on the optical axis, and the light condensed by the condensing optical system is transmitted,
The light transmitted through the pinhole is split into reference light and measurement light by a beam splitter,
retroreflecting the reference light by a first optical system;
irradiating the measurement light onto the object using a second optical system and collecting the return light from the object;
recording a first spot center position formed on an imaging unit by the reference light transmitted through the first pinhole and split by the beam splitter;
aligning a second spot center position formed by the reference light transmitted through the second pinhole and split by the beam splitter on the imaging unit with the first spot center position;
imaging the measurement light transmitted through the second pinhole and guided to the second optical system by the imaging unit;
moving the pinhole plate, the beam splitter, the first optical system, and the imaging unit along the optical axis by a stage;
An eccentricity measurement method that calculates eccentricity of the subject based on an eccentricity amount of the measurement light imaged by moving the stage with respect to the reference light.

Images