JP2018072375A - Method of measuring eccentricity of optical component holding frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of measuring the eccentricity of optical component holding frames that is applied to a lens barrel having optical component holding frames capable of shifting along the optical axis with which a variation in the shift eccentricity resulting from a shift of the optical component holding frame can be measured easily for each optical component holding frame.SOLUTION: A method of measuring the eccentricity of an optical component holding frame includes securing a measurement surface 12a provided with an index 12b and an index member 12 composed of a condenser lens unit having a focal plane located on the measurement surface 12a on a second lens frame 2B provided in a lens barrel 1, measuring the amount of shift of the index 12b with respect to a direction perpendicular to a reference axis C of the lens barrel 1 by detecting light coming from the index 12b passing through the index member 12 by means of an optical measurement unit 13, and converting the amount of shift into a shift eccentricity of the second lens frame 2B.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for measuring the amount of eccentricity of an optical component holding frame.

In an optical apparatus, a lens is often used in a state where it is held in a lens frame and assembled in a lens barrel. The position and orientation of the optical axis of the lens held by the lens frame are affected by the manufacturing error of the lens frame or the movement error of the lens frame in the lens barrel. For example, a lens barrel such as a zoom lens is used in a state where a plurality of lenses are held in a plurality of lens frames and the plurality of lenses move relative to each other. For this reason, if a manufacturing error or a movement error exists in each lens frame, the eccentricity of the entire optical system changes according to the movement of the lens. Such a variation in the decentration of the lens may cause deterioration of the optical performance of the optical system, such as image blur.
Therefore, there has been proposed a lens frame eccentricity measuring method for measuring a manufacturing error and a movement error of a lens frame contributing to the eccentricity in the lens barrel.
For example, in the eccentricity acquisition method described in Patent Document 1, a flat plate member on which an index such as a reticle is formed is arranged on each lens frame, and each flat plate member is illuminated. Then, the shift eccentricity is calculated from the image of each index acquired by the tool microscope. When measuring the tilt eccentricity, the illumination light is parallel light, and the reflection angle of the parallel light by the flat plate member is converted into the tilt eccentricity.

International Publication No. 2015/108188

However, the conventional techniques as described above have the following problems.
According to the eccentricity acquisition method described in Patent Document 1, it is necessary to acquire an index image with a tool microscope in measuring the shift eccentricity. For this reason, it is necessary to perform a focusing operation for acquiring an index image for each flat plate member. In particular, when the position of the flat plate member moves in a complicated manner as in a zoom lens, there is a problem that it is difficult to follow and perform an accurate focusing operation.
For example, it may be possible to reduce the focusing operation by moving the measuring device in synchronization with the movement of the flat plate member after focusing on the flat plate member at a specific position. However, since the movement mechanism that realizes the movement of the flat plate member and the movement of the measuring instrument cannot be made common, different movement errors occur during each movement. For this reason, there exists a problem that it is difficult to match each moving amount | distance correctly. If each movement error has repetitive reproducibility, it is possible to correct the movement error, but it is not possible to correct even a movement error without repetitive reproducibility.
In this way, in a lens barrel having an optical component holding frame that can be moved in the direction along the optical axis for zooming, focusing, etc., it is easy to measure fluctuations in shift eccentricity caused by movement of the optical component holding frame There is a strong demand to do.

  The present invention has been made in view of the above problems, and in a lens barrel having an optical component holding frame provided so as to be movable in a direction along the optical axis, a shift accompanying the movement of the optical component holding frame. It is an object of the present invention to provide a method for measuring the amount of eccentricity of an optical component holding frame that can easily measure the variation in eccentricity for each optical component holding frame.

  In order to solve the above-described problem, the method for measuring the amount of eccentricity of the optical component holding frame according to the first aspect of the present invention includes a measurement surface on which an index is formed and a condensing lens in which a focal plane is aligned with the measurement surface An index member that includes a second optical axis disposed parallel to a reference axis of the lens barrel, An optical measurement unit comprising: an imaging optical system that forms an image of light; and an optical sensor having a sensor surface disposed at a position defocused from the image plane of the imaging optical system that is optically conjugate with the measurement surface And detecting the light from the index that has passed through the condenser lens unit, measuring the shift amount of the index in a direction orthogonal to the reference axis, and determining the shift amount as the optical component. Converting to a shift eccentric amount in the holding frame.

  In the method for measuring the amount of eccentricity of the optical component holding frame, the measurement surface of the index member may be formed on a part of the condenser lens portion.

  In the method for measuring the amount of eccentricity of the optical component holding frame, the indicator member is in a direction along the first optical axis of the plate-like member having the measurement surface, the condensing lens unit, and the condensing lens unit. You may provide the fixing member which fixes the relative position of the said plate-shaped member and the said condensing lens part.

  The method of measuring the amount of eccentricity of the optical component holding frame further includes measuring the amount of tilt eccentricity of the optical component holding frame in the lens barrel before converting the shift amount to the shift eccentricity amount, When converting the shift amount into the shift eccentric amount of the optical component holding frame, the shift component generated based on the tilt eccentric amount is removed from the shift amount, and then the shift amount is converted into the shift eccentric amount. You may convert.

  In the method of measuring the amount of eccentricity of the optical component holding frame, the optical component holding frame is provided so as to be movable in a direction along the reference axis, and when measuring the shift amount, The shift amount may be measured by changing the position on the reference axis.

  In the method for measuring the amount of eccentricity of the optical component holding frame, when the index member is held by the optical component holding frame, the mass held by the optical component holding frame holding the index member is determined when the lens barrel is used. The optical component holding frame that holds the index member may be matched to the mass that is held.

  In the method for measuring the amount of eccentricity of the optical component holding frame, when the lens barrel includes a plurality of the optical component holding frames, the mass that each of the optical component holding frames holds before measuring the shift amount. May be further matched with the mass held by each of the optical component holding frames when the lens barrel is used.

  According to the method for measuring the amount of eccentricity of the optical component holding frame of the present invention, in the lens barrel having the optical component holding frame that is movably provided in the direction along the optical axis, the shift eccentricity associated with the movement of the optical component holding frame is detected. There is an effect that the fluctuation can be easily measured for each optical component holding frame.

It is a typical system block diagram which shows an example of the eccentric amount measuring system used for the eccentric amount measuring method of the optical component holding frame of embodiment of this invention. It is a schematic diagram which shows the example of the image of the parameter | index acquired with the eccentricity measuring method of the optical component holding frame of embodiment of this invention. It is a schematic diagram explaining the principle of the eccentricity measuring method of the optical component holding frame of the embodiment of the present invention. It is a schematic diagram explaining the effect | action of the eccentricity measuring method of the optical component holding frame of embodiment of this invention. It is typical sectional drawing explaining the eccentricity measuring method of the optical component holding frame of the 1st modification of embodiment of this invention. It is typical sectional drawing explaining the example of the parameter | index member used for the eccentricity measuring method of the optical component holding frame of the 2nd modification of embodiment of this invention. It is typical sectional drawing explaining the example of the parameter | index member used for the eccentricity measuring method of the optical component holding frame of the 3rd modification of embodiment of this invention.

Hereinafter, a method for measuring the amount of eccentricity of the optical component holding frame according to the embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic system configuration diagram showing an example of an eccentricity measurement system used in an optical component holding frame eccentricity measurement method according to an embodiment of the present invention.
Note that FIG. 1 is a schematic diagram, and dimensions and shapes are exaggerated or simplified (the same applies to the following drawings).

FIG. 1 shows a configuration example of an eccentricity measuring system 100 that can be used in the eccentricity measuring method of the optical component holding frame of the present embodiment. The eccentricity measuring system 100 is used to measure the shift eccentricity of the optical component holding frame of the lens barrel 1.
The lens barrel 1 is a cylindrical member that houses an optical component including a lens. However, FIG. 1 shows a state in which the optical component housed in the lens barrel 1 is removed in order to perform the eccentricity measurement. The lens barrel 1 on which the optical component is mounted can be used for an appropriate optical device, for example, a camera, a microscope, an endoscope, or the like.
The optical component housed in the lens barrel 1 may be a lens alone, or may be a lens and an optical component other than the lens. Examples of optical components other than lenses include mirrors, prisms, filters, diaphragms, image sensors, light emitting elements, light receiving elements, and the like. Further examples of other optical components include parallel plate-shaped optical components such as a cover glass and a filter.

The optical components housed in the lens barrel 1 are arranged along the reference axis C inside the outer cylinder 1 a that is an exterior member of the lens barrel 1. For example, the reference axis C may be an axis that is coaxial or parallel to the central axis of the outer cylinder 1a. The outer cylinder 1a may be a cylindrical member having a constant length along the reference axis C. Alternatively, the outer cylinder 1a may be configured by a combination of a plurality of cylindrical members that can move relative to each other in the direction along the reference axis C or around the reference axis C. In this case, the outer cylinder 1a may be expandable / contractable in the direction along the reference axis C as a whole.
An outer peripheral portion or an end portion of the outer cylinder 1a may be provided with a mounting portion for an optical device such as an appropriate mount.

There may be one or a plurality of optical components housed in the lens barrel 1. The optical component is held by an optical component holding frame arranged inside the outer cylinder 1a. The optical component holding frame may be fixed at a position along the reference axis C, or may be provided so as to be movable along the reference axis C.
Hereinafter, as an example, an example in which an optical component is held by the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C, which are optical component holding frames, will be described.
The first lens frame 2A includes a holding portion 2a that holds a lens 3A (see a two-dot chain line in the drawing) that is an optical component in a direction along the lens optical axis. Similarly, the second lens frame 2B and the third lens frame 2C also include holding portions 2b and 2c that hold a lens (not shown) in a direction along each lens optical axis.
The shape of the holding portions 2a, 2b, and 2c is not particularly limited as long as the lens can be held. In the present embodiment, as an example, a case where the holding portions 2a, 2b, and 2c include a plane orthogonal to the reference axis C will be described. The holding portions 2a, 2b, and 2c may be configured so that the lenses that are held by the holding portions 2a, 2b, and 2c can be positioned in a direction perpendicular to the reference axis C.

The first lens frame 2 </ b> A, the second lens frame 2 </ b> B, and the third lens frame 2 </ b> C are arranged in a separated state in this order in the direction along the reference axis C.
At least the second lens frame 2B is provided so as to be movable in a direction along the reference axis C by a moving mechanism (not shown).
The design holding centers of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C are arranged in a predetermined positional relationship with respect to the reference axis C. For example, when the optical system of the lens barrel 1 is a coaxial optical system, each design holding center is disposed on the same axis parallel to at least the reference axis C.

In the following, the amount of displacement from the design position in the direction orthogonal to the reference axis C of each holding center of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C is expressed as the first lens frame 2A. , Defined as the amount of shift eccentricity of the second lens frame 2B and the third lens frame 2C.
Similarly, the error from the design value of the holding posture of the lens with respect to the reference axis C in the holding portions 2a, 2b, and 2c is expressed as the tilt eccentricity amount of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C. Define. For example, when the holding portions 2a, 2b, and 2c include a plane portion that is orthogonal to the reference axis C in order to hold the lens, the inclination angle of each plane portion of the holding portions 2a, 2b, and 2c with respect to the plane orthogonal to the reference axis C Represents the amount of tilt eccentricity of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C.

In the present embodiment, as an example, a description will be given of an example in which each design holding center is arranged coaxially with the reference axis C. Furthermore, for simplicity, the holding units 2a, 2b, and 2c will be described by using an example in which the centers of the lens outer shapes to be held are held so as to coincide with the reference axis C by design.
In this case, the shift decentering amount of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C is the shift decentering amount of the outer center of each lens held by the holding portions 2a, 2b, and 2c. . The shift decentering amount of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C is the shift decentering amount added to the shift decentering amount of each lens itself in the optical system in the lens barrel 1. .
The tilt decentering amount of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C is the tilt decentering amount added to the tilt decentering amount of each lens itself in the optical system in the lens barrel 1. .

  The eccentricity measurement system 100 includes a lens barrel holding unit 10, an illumination light source 11, an index member 12, an optical measurement unit 13, and an arithmetic processing unit 16.

The lens barrel holding unit 10 holds the lens barrel 1. The lens barrel holding unit 10 may hold any part of the lens barrel 1 as long as the position of the lens barrel 1 can be stably held.
The lens barrel holding unit 10 holds the lens barrel 1 so that an optical axis O ₁₄ of an optical measurement unit 13 (to be described later) and a reference axis C of the lens barrel 1 are coaxial.

The illumination light source 11 irradiates the inside of the lens barrel 1 with illumination light L. The illumination light L is used to illuminate an index member 12 described later. In this embodiment, the illumination light source 11 irradiates the illumination light L in a direction along the reference axis C from one end side (left side in the drawing) of the lens barrel 1.
However, when the indicator 12b of the indicator member 12 to be described later can be observed only by the external light incident on the lens barrel 1, the illumination light L from the illumination light source 11 does not have to be irradiated.

The index member 12 is disposed and used in the holding portions 2a, 2b, and 2c, respectively, in order to obtain the shift eccentricity of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C. When the shapes of the holding portions 2a, 2b, and 2c are different, a plurality of index members 12 whose outer shapes are changed according to the shapes may be used.
Below, the example in the case of the parameter | index member 12 arrange | positioned at the 2nd lens frame 2B is demonstrated as an example.
The index member 12 in the present embodiment is configured by a lens having a measurement surface 12a on which an index 12b is formed and a lens surface 12c facing the measurement surface 12a. Hereinafter, the optical axis (first optical axis) of the index member ₁₂ is expressed as O12.
A cylindrical side surface 12d having an outer diameter that can be inserted into the second lens frame 2B is formed on the outer peripheral portion between the measurement surface 12a and the lens surface 12c. In this embodiment, the central axis of the side surface 12d is an optical axis O ₁₂ coaxially.

Measurement surface 12a is composed of a plane extending in a direction orthogonal to the optical axis _{O 12.} The measurement surface 12a is formed so as to be positioned on the same plane as the holding plane of the holding portion 2b when the index member 12 is held by the holding portion 2b of the second lens frame 2B.

The index 12b is composed of an appropriate mark that can detect a positional shift by an image. Examples of the indicator 12b include marks formed in a dot shape, a circular shape, a polygonal shape, a cross shape, and a lattice shape. Other examples of the indicator 12b include a mask-like mark that transmits light to a dot-like, circular, polygonal, cross-shaped, or lattice-shaped region.
Indicator 12b, the position of which point P ₁ the intersection of the image and the measurement surface 12a and the optical axis O ₁₂ as can be estimated, is formed at a position that is related to the point P _1.
For example, if the indicator 12b is composed of point-like marks, indicators 12b may be formed on the point P _1. For example, if the indicator 12b is composed of point-like marks, indicators 12b may be formed at three or more places on a circle centered on the point P _1. For example, if the indicator 12b is composed of point-like marks, indicators 12b may be formed into two intersections of the straight line passing through the center and circumference of a circle centered on point P _1.
For example, when the indicator 12b is formed of a mark such as a circle or a polygon, the center of these marks may be formed at the same position as the above-described dot-like mark.
For example, in the case where the index 12b is formed of a cross-shaped or lattice-shaped mark, the intersection of straight lines in these marks may be formed at the same position as the above-described point-shaped mark.
Similarly, when the index 12b is a mask-shaped mark having various shapes, the center of the light transmission region shape, the centroid, or the like may be formed at the same position as the dot-shaped mark described above. .

In the following, as an example, indicator 12b is a thin cross mark line width, described in example in which the intersection of the cross coincides with the point P _1.

Lens surface 12c is the front focal length f ₁₂ of the lens of the index member 12 is formed of a lens surface is equal to the distance between the front main surface and the measuring surface 12a. For example, the lens surface 12c may be a convex spherical surface or an aspherical surface. For example, the lens surface 12c may be a Fresnel lens surface.
For this reason, the light that diverges from the measurement surface 12a becomes a parallel light flux when transmitted through the lens surface 12c. In particular, the light L ₁ that diverges from the point P ₁ becomes a parallel light beam L ₂ that travels along the optical axis O ₁₂ .
As described above, the index member 12 constitutes a condensing lens unit in which the focal plane is matched with the measurement surface 12a. The index member 12 is an example of an index member in which a measurement surface 12a is formed on a part of the condenser lens portion.

Such an indicator member 12 may be formed of a light-transmissive glass material or a light-transmissive plastic material. As a method for forming the indicator member 12, for example, polishing processing or molding processing may be used.
The method for forming the indicator 12b in the indicator member 12 is not particularly limited as long as the above pattern can be formed. For example, examples of the method for forming the index 12b include groove processing, etching, engraving, printing, painting, vapor deposition, and the like on the measurement surface 12a.

The light measurement unit 13 detects the light from the measurement surface 12a that has passed through the index member 12 that is a condenser lens unit, and measures the shift amount of the index 12b from the image of the index 12b. In the present embodiment, since the reference axis C and the optical axis O ₁₄ are coaxial, the shift amount of indicator 12b is the amount of movement of the indicator 12b from the reference axis C in a plane perpendicular to the reference axis C.
The optical measurement unit 13 is disposed at a position facing the lens barrel 1 held by the lens barrel holding unit 10. In the present embodiment, the lens barrel 1 is opposed to the lens barrel 1 on the side opposite to the illumination light source 11 (right side in the drawing).
The optical measurement unit 13 includes an imaging lens 14 (imaging optical system) and an image sensor 15 (optical sensor).
The imaging lens 14 constitutes an imaging optical system that forms an image of light from the measurement surface 12 a that has passed through the index member 12. FIG. 1 schematically illustrates the imaging lens 14 as a single lens for the sake of schematic diagram. However, the imaging lens 14 may be configured by combining a plurality of lenses.
The optical axis O ₁₄ (second optical axis) of the imaging lens 14 is arranged so as to be coaxial with the reference axis C of the lens barrel 1 held by the lens barrel holder 10.

The imaging element 15 photoelectrically converts light projected on the imaging surface 15a (sensor surface) according to the light intensity. For example, a CCD (charge coupled device), a CMOS image sensor, or the like may be used as the imaging element 15. The image sensor 15 sends out an image signal photoelectrically converted to an arithmetic processing unit electrically connected to an arithmetic processing unit 16 described later.
The imaging surface 15 a of the imaging element 15 is disposed at a position defocused from the image plane of the imaging lens 14 that is optically conjugate with the measurement surface 12 a of the index member 12.
For example, if the focal length of the imaging lens 14 and f _14, the defocus amount delta (However, delta ≠ 0) the imaging surface 15a as is the position of the rear principal plane distance f _{14 +} delta after the imaging lens 14 Be placed. FIG. 1 shows an example where Δ> 0 as an example.

The arithmetic processing unit 16 converts the image signal sent from the image sensor 15 into image data, and calculates the shift amount of the index 12b based on this image data. Further, the arithmetic processing unit 16 converts the shift amount of the index 12b into the shift eccentricity amount of the optical component holding frame on which the index member 12 is arranged.
Appropriate hardware is used for the apparatus configuration of the arithmetic processing unit 16. In the present embodiment, the arithmetic processing unit 16 includes a computer including a CPU, a memory, an input / output interface, an external storage device, and the like. When the computer executes an arithmetic processing program, arithmetic processing including image processing is performed. Is called.

A method for measuring the amount of eccentricity of the optical component holding frame of the present embodiment using the amount of eccentricity measurement system 100 will be described. In the following description, when the relative position along the optical axis O ₁₄ in the eccentricity measuring system 100 is expressed, the one closer to the image sensor 15 in the range from the illumination light source 11 to the image sensor 15 (shown in FIG. 1). The right side may be referred to as the rear position, and the farther from the image sensor 15 (the left side in the drawing in FIG. 1) may be referred to as the front position. For example, the illumination light source 11 is located in front of the lens barrel holding unit 10.
FIG. 2 is a schematic diagram illustrating an example of an index image acquired by the method for measuring the amount of eccentricity of the optical component holding frame according to the embodiment of the present invention. FIG. 3 is a schematic diagram illustrating the principle of the method for measuring the amount of eccentricity of the optical component holding frame according to the embodiment of the present invention. FIG. 4 is a schematic diagram for explaining the operation of the optical component holding frame eccentricity measuring method according to the embodiment of the present invention.

The arithmetic processing unit 16 of the eccentricity measuring system 100 stores the tilt eccentricity of each optical component holding frame of the lens barrel 1. As the tilt eccentricity of each optical component holding frame, a measurement value measured in advance by another measuring device may be used. When measuring the shift eccentricity in a state where the optical component holding frame is moved in the direction along the reference axis C, the tilt eccentricity is also stored for each similar movement position.
However, if it is known that the tilt eccentricity of each optical component holding frame of the lens barrel 1 is sufficiently smaller than the shift eccentricity, the arithmetic processing unit 16 replaces the tilt eccentricity with the measured value. 0 may be stored.

As a method of measuring the tilt eccentricity, for example, a tilt eccentric measuring jig made of, for example, a mirror or a parallel plate is arranged on the optical component holding frame instead of the optical component, and the measuring jig is tilted with respect to the reference axis C. A method of measuring the angle may be used.
For example, an autocollimator may be used as the angle measuring device. The autocollimator can perform continuous measurement without moving the autocollimator itself even if the measurement object moves along the measurement optical axis. According to such measurement, even if a plurality of optical component holding frames are arranged at different positions along the measurement optical axis or the position of the optical component holding frame along the measurement optical axis changes, the tilt eccentricity amount Is easily measured.
The tilt eccentricity measuring device may be built in the eccentricity measuring system 100 and used by switching to the optical measuring unit 13. Alternatively, the tilt eccentricity measuring device may be provided independently of the eccentricity measuring system 100.

In order to perform the eccentricity measurement using the eccentricity measurement system 100, the optical component having refractive power, at least the optical component holding frame (first optical component holding frame) to be measured and the optical measuring unit 13 is used. The optical component held by another optical component holding frame (second optical component holding frame) located between (image side) is removed before the start of measurement. In this state, the index member 12 is arranged on the optical component holding frame to be measured.
However, it is more preferable that an optical component that may interfere with illumination light irradiation be removed even when it is located on the front side (opposite to the image side) of the optical component holding frame to be measured. Examples of optical components that may interfere with illumination light irradiation include optical components having refractive power, optical components that greatly reduce the amount of illumination light, and the like.

Hereinafter, an example in which the optical component holding frame to be measured is the second lens frame 2B will be described. In the example shown in FIG. 1, all the lenses of the lens barrel 1 are removed.
The index member 12 is held by the second lens frame 2B so that the positional relationship with the second lens frame 2B is kept constant during measurement. For example, the index member 12 may be fixed to the second lens frame 2B using an adhesive or the like.
The lens barrel 1 holding the index member 12 is held by the lens barrel holding portion 10.
When the lens barrel 1 is held by a lens barrel holding portion 10, so that the reference axis C and the optical axis O ₁₄ is coaxially, optionally, the lens barrel holder 10 and the optical measuring unit 13 The relative position between them is adjusted.
Direction of the distance along the optical axis O ₁₄ between the lens barrel 1 and the optical measuring unit 13 is not particularly limited.

When the illumination light L is emitted from the illumination light source 11, the indicator 12b is illuminated from the front side.
Of the illumination light L, the light that passes through the contour of the index 12 b is collected by the index member 12. The index 12 b is located on the measurement surface 12 a that is the front focal plane of the index member 12. Therefore, the light passing through the outline of the reference member 12, the process proceeds to the rear side as a parallel light beam L _3.
For example, as shown in FIG. 1, when the shift amount of eccentricity of the second lens frame 2B is zero, the optical axis O ₁₂ is an optical axis O ₁₄ coaxially. The parallel light beam L ₂ that is the axial light beam of the optical axis O ₁₂ is imaged at the rear focal point Q of the imaging lens 14 by the imaging lens 14.
Parallel beam passing through the contour in the vicinity of the cross points of intersection in the indicator 12b L ₃ proceeds substantially the same optical path as the parallel light beam L _2. The parallel light beam L ₃ is imaged on the image plane of the imaging lens 14 by the imaging lens 14 and then diverges to the rear side.
Similarly, light passing through the other contour of the index 12b is emitted from the index member 12 as a parallel light beam, and after being imaged on the image plane of the imaging lens 14 by the imaging lens 14, it diverges to the rear side.
As a result, as shown in FIG. 2, on the imaging surface 15a, the image R ₁ is projected a defocused image of the indicator 12b. In the example of this embodiment, the image R ₁ is the line width than the index 12b is wider cross-shaped image.

In the optical measuring unit 13, the center _{O 15a} of the imaging surface 15a is to the reference axis C coaxial with the optical axis _{O 14} are aligned. Therefore, when the shift amount of eccentricity of 0 in the second lens frame 2B, the center _{O R1} image _{R 1} is coincident with the center _{O 15a.}
On the other hand, for example, as shown in FIG. 3, when the tilt decentering amount of the second lens frame 2B is 0 and the shift decentering amount is E ₂ larger than 0, the index member 12 passes through the contour of the index 12b. the light beam in a collimated is translated by a distance E ₂ eccentric direction. For example, the parallel light beam L ₃ passing through the outline of the vicinity of the cross intersection _'is in index 12b, when a parallel beam L ₃ in FIG. 1 by a distance E _2, it becomes the same light flux as that moves parallel to the eccentric direction.
As a result, as shown in FIG. 3, the imaging surface 15a, the image R ₂ index 12b which corresponds to the image R ₁ is translated by [delta] ₂ to the side opposite to the eccentric direction is projected. Thus, seeking a position on the imaging surface 15a of the center _{O R2} image _{R 2,} by determining the magnitude of the position vector of the center _{O R2} with respect to the center _{O 15a,} the shift amount of the image _{R 2} on the imaging plane 15a [delta] ₂ Is required. Position vector of the center _{O R2} is the xy coordinate system is a rectangular coordinate system on the imaging surface 15a, is obtained as (δ _x2, δ _y2).
The direction of shift eccentricity for calculating the eccentricity is opposite to the direction of the position vector of the center _OR2 .

The shift amount δ ₂ and the eccentric amount E ₂ on the imaging surface 15a are the focal length f ₁₄ of the imaging lens ₁₄ and the arrangement position of the imaging surface 15a when the second lens frame 2B has no tilt eccentricity. The relational expression (first relational expression) including the magnitude of Δ corresponds one-to-one.
As the magnitude of Δ, which is the defocus amount, is larger, the amount of movement of the image with respect to the shift eccentric amount becomes larger, so that the calculation accuracy of the shift eccentric amount can be improved. However, if Δ becomes too large, the image of the index 12b becomes blurred, and the accuracy of calculating the image center may be reduced. For this reason, the magnitude of Δ is set according to the shape of the indicator 12b and the like so as to ensure the measurement accuracy necessary for measuring the shift eccentricity.

When the second lens frame 2B has tilt decentering, the shift amount δ ₂ of the image R ₂ includes the shift amount δ _2T resulting from the true shift decentering amount and the apparent shift amount δ _2F (shifting due to tilt decentering). Component).
The tilt eccentricity and the apparent shift amount δ _2F are paired by a relational expression (second relational expression) that includes the focal length f14 of the imaging lens ₁₄ and the magnitude of Δ that is the arrangement position of the imaging surface 15a. Corresponding to one.
The arithmetic processing unit 16 in the present embodiment stores in advance a first relational expression for calculating the eccentricity amount from the true shift amount and a second relational expression for calculating the apparent shift amount from the tilt eccentricity amount. ing.

The processing of the arithmetic processing unit 16 executed based on the above measurement principle will be briefly described.
For example, when receiving an image signal corresponding to the image _{R <} b> 2 from the image sensor 15, the arithmetic processing unit 16 converts the image signal into two-dimensional image data.
Thereafter, the arithmetic processing unit 16 performs an appropriate image processing operation on the image data to obtain the position coordinates (δ _x2 , δ _y2 ) and the size δ ₂ of the center _{OR 2} of the image R ₂ .
The arithmetic processing unit 16 substitutes the tilt eccentricity at the measurement position of the second lens frame 2B stored in advance into the second relational expression to calculate the apparent shift amount δ _2F .
Arithmetic processing unit 16 subtracts the shift amount [delta] _2F apparent from the shift amount [delta] _2, and calculates a true shift amount [delta] _2T.
Thereafter, the arithmetic processing unit 16 substitutes the true shift amount δ _2T for the first relational expression and converts it into the true shift amount of the index 12b. True shift amount of indicator 12b is equal to the shift amount of eccentricity E ₂ of the second lens frame 2B of indicator member 12 is disposed. The arithmetic processing unit 16 may further calculate an eccentric direction, a coordinate decomposition value of the eccentric amount, and the like as necessary.
This completes the measurement of the shift eccentricity in the second lens frame 2B.

In the case of measuring the shift eccentricity at the other movement position in the second lens frame 2B, the second lens frame 2B is moved in the direction along the reference axis C using the movement mechanism in the lens barrel 1, and then the above-mentioned. In this way, the defocused image of the index 12b is acquired and the same measurement is repeated. In this case, the index member 12 may remain disposed on the second lens frame 2B. For this reason, it is possible to continuously measure the amount of eccentricity at a plurality of positions of the second lens frame 2B moved by the moving mechanism. As a result, the amount of eccentricity during the movement of the second lens frame 2B including the amount of eccentricity caused by the movement error of the moving mechanism of the lens barrel 1 is measured.
For example, when measuring the shift eccentricity of other optical component holding frames such as the first lens frame 2A and the third lens frame 2C, the index member 12 is disposed on the optical component holding frame to be measured, and Repeat the same measurement. In this case, when the index member 12 used in the second lens frame 2B cannot be arranged on the optical component holding frame to be measured, another index member 12 that can be arranged on the optical component holding frame to be measured is arranged.

According to the method for measuring the amount of eccentricity of the optical component holding frame of this embodiment, the light from the index 12b is converted into a parallel light beam by the condenser lens portion of the index member 12, and the image of the index 12b is acquired by the light measurement unit 13.
For example, as shown in FIG. 4, when the second lens frame 2B moves to the front side, the distance between the second lens frame 2B and the imaging lens 14 of the optical measurement unit 13 changes. Further, the shift amount of eccentricity of the size of the second lens frame 2B is changed to E _3, even the direction of the shift eccentric is likely to change.
However, since the light incident on the imaging lens 14 in order to acquire the image of the index 12b is a parallel light beam, the light measuring unit 13 is focused on the moving measurement surface 12a or moved in accordance with the movement of the measurement surface 12a. The amount of eccentricity can be measured by the optical measuring unit 13 without moving.
In particular, when the lens barrel 1 is a zoom lens, the second lens frame 2B needs to move along the reference axis C while rotating around the reference axis C in the lens barrel 1 depending on the zoom position. There is a case. At that time, the shift eccentricity and the shift direction at each movement position may change in a complicated manner due to the movement error of the zooming movement mechanism.
In such a case, in order to analyze the manufacturing error of the lens barrel 1 that affects the optical performance, it is necessary to finely measure the shift eccentricity of the second lens frame 2B at a number of movement positions along the reference axis C.
In the present embodiment, when the second lens frame 2B is moved in the direction along the reference axis C, the defocused image of the index 12b can be obtained sequentially and continuously, and measurement at each moving position is extremely easy and quick. Can be done.

  Similarly, when an optical component holding frame other than the second lens frame 2B is set as the measurement target in the lens barrel 1, the distance between the imaging lens 14 and the measurement target changes. Also in this case, as described above, the eccentricity can be measured without performing focusing or moving the optical measuring unit 13. Therefore, the eccentricity can be measured immediately after the indicator member 12 is rearranged.

As described above, according to the method for measuring the amount of eccentricity of the optical component holding frame of the present embodiment, in the lens barrel having the optical component holding frame that is movably provided in the direction along the optical axis, The fluctuation of the shift eccentricity accompanying the movement of the optical component can be easily measured for each optical component holding frame.
According to the method of measuring the amount of eccentricity of the optical component holding frame of the present embodiment, even when the lens barrel moves simultaneously in the direction along the optical axis in order to perform, for example, zooming, focusing, etc. The amount of eccentricity during movement can be easily measured for each optical component holding frame.
For this reason, the optical component holding frame having a large amount of eccentricity that contributes to image blur or the like is easily specified from the measurement result. Based on this identification result, by correcting the error of the optical component holding frame that greatly contributes to image blur, it is possible to improve the optical characteristics of the lens barrel 1 during zooming and focusing.

[First Modification]
A method for measuring the amount of eccentricity of the optical component holding frame of the first modification of the present embodiment will be described.
FIG. 5 is a schematic cross-sectional view illustrating a method for measuring the amount of eccentricity of the optical component holding frame according to the first modification of the embodiment of the present invention.

In the method for measuring the amount of eccentricity of the optical component holding frame of the present modification, the mass held by each of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C before the shift amount of the index 12b is measured. It further includes matching with the mass held by each of the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C when the lens barrel 1 is used.
Hereinafter, a description will be given focusing on differences from the above embodiment.

As shown in FIG. 5, in this modification, the lenses mounted on the first lens frame 2A and the third lens frame 2C when the lens barrel 1 is used are respectively mounted on the first lens frame 2A and the third lens frame 2C. Weights 20A and 20C having a mass matched to the mass are arranged.
The mass of the weight 20A (20C) is designed based on the mass of the lens mounted when the lens barrel 1 is used.
The user of this technology may appropriately determine the tolerance between the mass of the weight 20A (20C) and the mass of the lens mounted when the lens barrel 1 is used. For example, when a deviation of ± 5% with respect to the mass of the lens mounted when using the lens barrel 1 is allowed, if the mass of the lens is 100 g, the mass of the weight 20A (20C) is in the range of 95 g to 105 g. It only has to be designed to be.

Furthermore, in this modification, it replaces with the index member 12 of the said embodiment, and the index member 12B is used.
The index member 12B is configured in the same manner as the index member 12 except that the mass is matched with the mass of the lens mounted on the second lens frame 2B when the lens barrel 1 is used.
A user of this technology may appropriately determine a tolerance between the mass of the index member 12B and the mass of the lens mounted when the lens barrel 1 is used. For example, when a deviation of ± 5% with respect to the mass of the lens mounted when using the lens barrel 1 is allowed, if the mass of the lens is 100 g, the mass of the index member 12B is in the range of 95 g to 105 g. If it is designed to.

According to this modification, the weight 20A, the index member 12B, and the weight 20C are provided on the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C. As a result, the masses held by the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C at the time of measuring the amount of eccentricity are the same as the first lens frame 2A and the second lens frame when the lens barrel 1 is used. 2B and the third lens frame 2C are matched with the mass held by each.
As a result, a static load acting on the lens barrel 1 via the first lens frame 2A, the second lens frame 2B, and the third lens frame 2C, or a dynamic load generated during the movement is applied to the lens mirror. It becomes substantially equal to the static and dynamic loads when the cylinder 1 is used (including the case where they are equal). As a result, since the measurement including the influence of the load acting when the lens barrel 1 is used can be performed, the measurement accuracy of the shift eccentricity is improved.

[Second Modification]
A method for measuring the amount of eccentricity of the optical component holding frame of the second modification of the present embodiment will be described.
FIG. 6 is a schematic cross-sectional view illustrating an example of an index member used in the method for measuring the amount of eccentricity of the optical component holding frame according to the second modification of the embodiment of the present invention.

As shown in FIG. 6, in the method for measuring the amount of eccentricity of the optical component holding frame according to this modification, an index member assembly 22 is used instead of the index member 12. FIG. 6 illustrates an example in which the index member assembly 22 is held by the second lens frame 2B as an example. The indicator member assembly 22 may be configured to be held by the first lens frame 2A and the third lens frame 2C.
Hereinafter, a description will be given focusing on differences from the above embodiment.

The index member assembly 22 includes an index member 21 having an outer diameter smaller than that of the index member 12 held by the second lens frame 2B in the above embodiment, and a frame member 20B that is externally fitted to the side surface 21d of the index member 21. .
Like the index member 12, the index member 21 is a condensing lens unit including a measurement surface 12a, an index 12b, and a lens surface 12c. The outer diameter of the index member 21 is not particularly limited as long as the numerical aperture that can project the image of the index 12b with the brightness that can be captured is secured.
The frame member 20B has an outer shape that can be held by the holding portion 2b of the second lens frame 2B. When the frame member 20B is held by the holding portion 2b of the second lens frame 2B, the frame member 20B holds the index member 21 so that the measurement surface 12a of the index member 21 is positioned in the same plane as the holding plane of the holding portion 2b.
Since the shape of the frame member 20B does not match, the frame member 20B functions as an adapter when the index member 21 alone cannot be held by the holding portion 2b of the second lens frame 2B.
Further, the frame member 20B may have a function of a weight that matches the mass of the index member assembly 22 with the mass held by the second lens frame 2B when the lens barrel 1 is used. A preferable range for adjusting the mass is the same as the mass of the indicator member 12B in the first modified example.

In this modification, the index member 21 is held by the holding portion 2b of the second lens frame 2B via the frame member 20B having the function of an adapter. For example, the outer diameter of the index member 21 is made smaller than each optical component holding frame, and the index member 21 is moved to each optical component via a frame member 20B whose outer diameter is matched with the shape of each optical component holding frame as necessary. It can hold | maintain at each holding | maintenance part of a component holding frame. For this reason, even if the shape of each optical component holding frame is different, the single-shaped index member 21 can be used in common.
The indicator member 21 is configured in the same manner as the indicator member 12 except that the outer peripheral portion is held by the frame member 20B. For this reason, by using the index member 21 instead of the index member 12, even in the case of the optical part holding frame of the lens barrel whose arrangement position in the direction along the optical axis is different or changes, as in the above embodiment, The amount of eccentricity can be easily measured.

  Further, when the mass of the index member assembly 22 is matched with the mass held by the second lens frame 2B when the lens barrel 1 is used, for example, the index barrel assembly 22 is attached to the lens barrel 1 via the second lens frame 2B. The acting static load or the dynamic load generated at the time of movement is substantially equal to the static and dynamic load when the lens barrel 1 is used (including the case where they are equal). As a result, since the measurement including the influence of the load acting when the lens barrel 1 is used can be performed, the measurement accuracy of the shift eccentricity is improved.

[Third Modification]
A method for measuring the amount of eccentricity of the optical component holding frame of the third modification of the present embodiment will be described.
FIG. 7 is a schematic cross-sectional view illustrating an example of an index member used in the method for measuring the amount of eccentricity of the optical component holding frame according to the third modification of the embodiment of the present invention.

As shown in FIG. 7, in the method for measuring the amount of eccentricity of the optical component holding frame according to this modification, an index member 33 is used instead of the index member 12. FIG. 7 shows an example in which the index member 33 is held by the second lens frame 2B as an example. The index member 33 may be configured to be held by the first lens frame 2A and the third lens frame 2C.
Hereinafter, a description will be given focusing on differences from the above embodiment.

The index member 33 includes an index plate 30 (plate member), a condensing lens 31 (condensing lens portion), and a frame member 32 (fixing member).
The indicator plate 30 is a plate-like member that includes a flat plate portion having optical transparency. On the flat plate portion of the indicator plate 30, an indicator 12b similar to that in the above embodiment is formed. The indicator 12b may be formed on the surface of the indicator plate 30 or may be formed inside. FIG. 7 shows an example in which the index 12b is formed on the measurement surface 30a which is the rear surface of the index plate 30 as an example. For example, the indicator 12b may be formed on the front surface of the indicator plate 30 (surface 30b in FIG. 7).
The indicator plate 30 is formed of a glass material or a plastic material. In the example shown in FIG. 7, the indicator plate 30 is composed of a flat plate. However, the indicator plate 30 may be formed with a curved portion or an uneven portion on the outer peripheral side as long as the portion where the indicator 12b is formed is a flat portion and is plate-like as a whole.

Condenser lens 31, the front focal distance of the positive lens of _{f 31.} The condensing lens 31 may be a single lens or a bonded lens. The lens type of the condenser lens 31 is not particularly limited. For example, the condensing lens 31 may be a spherical lens, an aspherical lens, or a Fresnel lens.

The frame member 32 is a cylindrical member that holds the relative position between the indicator plate 30 and the condenser lens 31. The frame member 32 has an outer shape that can be held by the holding portion 2b of the second lens frame 2B. In the example shown in FIG. 7, when the frame member 32 is held by the holding portion 2b of the second lens frame 2B, the measurement surface 30a of the index plate 30 is positioned in the same plane as the holding plane of the holding portion 2b. The indicator plate 30 is held.
The frame member 32 holds the condenser lens 31 on the rear side of the indicator plate 30. The frame member 32 holds the condenser lens 31 so that the front focal plane thereof coincides with the measurement surface 30 a of the indicator plate 30.
Intersection P ₂ of the optical axis O ₃₃ and the measurement surface 30a of the condenser lens 31 held by the frame member 32 is disposed at a position that is related to the index 12b as in the above embodiment.
A method for fixing the frame member 32 to the indicator plate 30 and the condenser lens 31 is not particularly limited. For example, the frame member 32, the indicator plate 30, and the condenser lens 31 may be fixed by adhesion.
Furthermore, the frame member 32 may have a function of a weight that matches the mass of the index member 33 with the mass held by the second lens frame 2B when the lens barrel 1 is used. A preferable range for adjusting the mass is the same as the mass of the indicator member 12B in the first modified example.

In the above embodiment, the index member 12 itself constitutes the condenser lens portion, whereas the index member 33 in the present modification is provided on the index plate 30 provided with the index 12b and the condenser lens 31. It is an example that is configured separately.
The index member 33 of this modification changes the light that diverges rearward from the measurement surface 30a into a parallel light flux. For this reason, even if the index member 33 is used instead of the index member 12, even if it is an optical component holding frame of a lens barrel whose arrangement position in the direction along the optical axis is different or changes, as in the above embodiment. The amount of eccentricity can be measured.

  In the description of the embodiment and the second modified example, the example in which the index members 12 and 21 are single lenses has been described. However, the index members 12 and 21 are not limited to single lenses. For example, the index members 12 and 21 may be bonded lenses. For example, the index members 12 and 21 may have a configuration in which one or more lenses and the index plate 30 in the third modified example are bonded together.

  In the description of the embodiment and each modification, the example in which the optical axis of the index member is coaxial with the reference axis C has been described. However, the deviation amount between the optical axis of the index member and the reference axis C at a specific position is known. If the optical axis of the indicator member is parallel to the reference axis C, the optical axis of the index member may be parallel.

  In the description of the embodiment and each modification, the example in which the optical sensor of the optical measurement unit 13 is the image sensor 15 has been described. However, appropriate light that can detect the positional deviation of the index according to the intensity of light from the index. Sensor can be used. For example, a position sensitive detector (PSD) using a photodiode may be used.

  In the description of the second modified example, the frame member 20B has been described as an example in which the holding function and the weight function of the index member 21 are provided. However, the frame member 20B may not have a weight function.

  In the description of the above embodiment and each modification, the illumination light source 11 illuminates the illumination light from the front side to the rear side. For this reason, the measurement surface of the indicator member is light transmissive. However, the illumination light may be irradiated from the rear side. In this case, the measurement surface of the indicator member may be configured by a reflection surface.

  In the description of the above-described embodiment and each modification, an example in which the measurement surface of the index member is located on the same plane as the holding plane of the holding unit in the optical component holding frame has been described. However, if it is better to measure the shift eccentricity and tilt eccentricity at a position deviated from the holding plane, for example, when the lens thickness is thick, the measurement surface is shifted from the holding plane in the direction along the optical axis. May be.

As mentioned above, although preferable embodiment and each modification of this invention were described, this invention is not limited to this embodiment and each modification. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit of the present invention.
Further, the present invention is not limited by the above description, and is limited only by the appended claims.

1 Lens barrel 2A First lens frame (optical component holding frame)
2B Second lens frame (optical component holding frame)
2C Third lens frame (optical component holding frame)
2a, 2b, 2c Holding part 3A Lens (optical component)
DESCRIPTION OF SYMBOLS 10 Lens barrel holding part 11 Illumination light source 12, 12B, 21 Index member (condensing lens part)
12a, 30a Measurement surface 12b Index 12c Lens surface 13 Optical measurement unit 14 Imaging lens (imaging optical system)
15 Image sensor (optical sensor)
15a Imaging surface 16 Arithmetic processing unit 20A, 20C Weight 20B, 32 Frame member 22 Index member assembly 30 Index plate (flat plate member)
30a Measuring surface 31 Condensing lens (condensing lens part)
32 Frame member (fixing member)
33 Index member 100 Eccentricity measuring system C Reference axis O ₁₂ , O ₃₃ optical axis (first optical axis)
O ₁₄ optical axis (second optical axis)

Claims (7)

Holding an index member including a measurement surface on which an index is formed and a condensing lens unit whose focal plane is aligned with the measurement surface in an optical component holding frame provided in the lens barrel;
An imaging optical system having a second optical axis arranged in parallel with a reference axis of the lens barrel and imaging light from the index, and the imaging optics optically conjugate with the measurement surface An optical sensor having a sensor surface disposed at a position defocused from the image plane of the system, and detecting light from the index that has passed through the condenser lens unit, and the reference axis Measuring the shift amount of the indicator in a direction orthogonal to
Converting the shift amount into a shift eccentric amount in the optical component holding frame;
A method for measuring the amount of eccentricity of the optical component holding frame. The measurement surface of the indicator member is formed on a part of the condenser lens portion.
The method for measuring the amount of eccentricity of the optical component holding frame according to claim 1. The indicator member is a plate-like member having the measurement surface, the condenser lens portion, and the relative relationship between the plate-like member and the condenser lens portion in a direction along the first optical axis of the condenser lens portion. A fixing member for fixing the position,
The method for measuring the amount of eccentricity of the optical component holding frame according to claim 1. Measuring the tilt eccentric amount of the optical component holding frame in the lens barrel before converting the shift amount into the shift eccentric amount;
When converting the shift amount into the shift eccentric amount of the optical component holding frame, a shift component generated based on the tilt eccentric amount is removed from the shift amount, and then the shift amount is converted into the shift eccentric amount. Convert to
The method of measuring the amount of eccentricity of the optical component holding frame according to any one of claims 1 to 3. The optical component holding frame is provided to be movable in a direction along the reference axis,
When measuring the shift amount, the shift amount is measured by changing the position of the optical component holding frame on the reference axis.
The method for measuring the amount of eccentricity of the optical component holding frame according to any one of claims 1 to 4. When holding the index member on the optical component holding frame, the optical component holding frame that holds the index member when the lens barrel is used has a mass held by the optical component holding frame that holds the index member. Match the mass to hold,
The method of measuring the amount of eccentricity of the optical component holding frame according to claim 5. When the lens barrel includes a plurality of the optical component holding frames,
Further including adjusting the mass held by each of the optical component holding frames to the mass held by each of the optical component holding frames when the lens barrel is used before measuring the shift amount,
The method for measuring the amount of eccentricity of the optical component holding frame according to any one of claims 1 to 6.

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