JP3410902B2 - Lens surface eccentricity measuring method and lens surface eccentricity measuring device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lens surface decentering measuring method and a lens surface decentering measuring apparatus.

[0002]

2. Description of the Related Art Conventionally, measurement of decentering of each lens surface in a lens system composed of two or more lenses is
JP-A-2-99841 and JP-A-3-107739
The technique described in the publication is known. However, in the techniques described in these publications, the “lens surface to be inspected” that is the target of eccentricity measurement is a spherical surface, and the eccentricity is obtained from the center of curvature of the inspected lens surface.

When an aspherical surface is included in the lens system, if the lens surface to be inspected is aspherical, the decentering of the lens surface to be inspected cannot be completely specified only by the position of the paraxial curvature center, and the aspherical axis It is also necessary to know the inclination, and it has been difficult to measure the eccentricity of the aspherical surface with the technique described in the above publication.

[0004]

In view of the above-mentioned circumstances, the present invention measures a desired decentering amount and decentering direction of a lens surface to be tested in a lens system including two or more lenses and including an aspherical surface. The challenge is to realize a lens surface decentering measurement method.

Another object of the present invention is to realize a lens surface eccentricity measuring device for realizing the above method.

[0006]

The "lens surface eccentricity measuring method" of the present invention provides a desired eccentricity of a lens surface to be tested in a lens system to be tested having three or more lens surfaces including one or more aspherical surfaces. This is a method of obtaining the eccentric direction.

The "test lens system" in the present invention is composed of two or more lenses. Therefore, the minimum number of lens surfaces included in the lens system is three when two lenses are cemented. Then, at least one aspherical surface is included in the lens surface of the lens system to be tested.

The "lens system to be inspected" may be assembled to the lens barrel to form a lens unit (for example, a zoom lens or the like). For example, in order to configure the zoom lens, the lens barrel is used. It may be a “lens system that is a part of the zoom lens system” that is assembled halfway.

The invention according to claim 1 has the following features. A desired or inspected lens surface is irradiated with a converging or diverging irradiation light beam from the reference optical axis direction of the inspected lens system. The reflected light beam from the lens surface to be inspected is formed at a predetermined distance from the center of curvature of the lens surface to be inspected, or the paraxial center of curvature and the aspherical axis by an imaging optical system in which the optical axis is substantially aligned with the reference optical axis. The image is formed on the light receiving surface of the image pickup means as an image with the object points at the respective positions near the center of curvature of the aspherical portion at the position. A predetermined calculation is performed using the coordinates of the barycentric position of each image and the data of the lens system to be inspected to obtain a desired eccentricity amount and eccentric direction of the lens surface to be inspected.

The "lens surface to be inspected" is a lens surface which is an object of eccentricity measurement among the lens surfaces of the lens system to be inspected. Since the lens surface to be inspected is a desired lens surface, any lens surface in the lens system to be inspected can be the lens surface to be inspected. Of course, all the lens surfaces of the lens system to be inspected are to be inspected. Can be

When there are two or more lens surfaces to be inspected, the eccentricity amount and the eccentric direction of each lens surface to be inspected can be measured sequentially from the irradiation side of the irradiation light beam (claim 2).

The "reference optical axis" refers to the designed optical axis of the lens system to be inspected, but specifically it may be considered as the central axis of the lens barrel holding the lens system to be inspected.

As described above, the object of eccentricity measurement is the "eccentricity amount and eccentric direction" of the lens surface to be tested. Here, the amount of eccentricity and the eccentric direction will be described with reference to FIG. In FIG. 4, reference numerals S ₁ , S ₂ , S ₃ , and S ₄ denote lens surfaces in the lens system 1 to be tested. It is assumed that each of the lens surfaces S _{1 to} S ₄ is a “test lens surface”. Also, the lens surface S ₁ ,
S ₃ is an “aspherical surface”, and the lens surfaces S ₂ and S ₄ are “spherical surfaces”. The straight line 2 indicates the “reference optical axis”.

First, regarding the lens surfaces S ₂ and S ₄ which are spherical surfaces, reference numerals S ₂ ′ and S ₄ ′ in the figure indicate the “centers of curvature” of the lens surfaces S ₂ and S ₄ , respectively. Since the lens surfaces S ₂ and S ₄ are spherical surfaces, the eccentricity in this case is the center of curvature S ₂ '
It is uniquely determined by the “deviation amount” of S ₄ ′ from the reference optical axis 2, that is, the distances in the figure: σ ₂ , σ ₄ . That is, the lens surface S
₂ and S ₄ , σ ₂ and σ ₄ are “eccentricity amounts”.

The direction in which the plane including the reference optical axis 2 and the center of curvature S ₂ 'is oriented in the plane orthogonal to the reference optical axis 2 gives the "eccentric direction" of the lens surface S ₂ , and the center of curvature S ₄ 'whether a plane including the reference optical axis 2 is oriented in any direction in a plane orthogonal to the reference optical axis 2 of the lens surface S ₄ "eccentric direction"
give.

Next, the case of the aspherical lens surfaces S ₁ and S ₃ will be described. As is well known, an aspherical surface generally has the Y-axis aligned with the aspherical surface axis and the h-axis orthogonal to the Y-axis: Y = f (h) = (h ² / R) / [1 + √ {1- (K + 1) (h ²
/ R ² )} + Ah ² + Bh ⁴ + Ch ⁶ +. ． ． It is a curved surface obtained by rotating the curve represented by the formula (1) around the Y-axis, and R, K, A, B, C, D ,. ． Specified by. The aspherical axis is therefore the axis of rotational symmetry in the aspherical surface. The “R” is a radius of curvature in the vicinity of the aspherical surface axis of the aspherical surface, that is, a “paraxial radius of curvature”. An aspherical surface portion having this paraxial radius of curvature is a “paraxial spherical surface portion”, and its center of curvature is a “paraxial surface radius”. The center of curvature ". The relationship between the aspherical shape and the Y and h coordinate axes is shown in FIG. 5 as an explanatory diagram. In FIG. 5, reference numeral S'denotes the paraxial curvature center.

Returning to FIG. 4, reference numerals S ₁ 'and S in the figure.
₃ 'each represents a paraxial curvature center of the lens surface S _1, S _3, the straight line S _1' ', the straight line S _3' 'respectively, the lens surfaces S _1,
The aspherical axis of S ₃ is shown.

The decentering amount of the lens surface S ₁ which is an aspherical surface is the deviation amount σ ₁ between the paraxial curvature center S ₁ 'and the reference optical axis 2, the aspherical surface axis S ₁ ″ and the reference optical axis 2. The angle formed by: is determined by ε ₁ . Similarly, the eccentricity of the lens surface S ₃ is the distance in the figure: σ ₃ ,
Angle: Determined by ε ₃ . The above σ ₁ and σ ₃ are called “shift eccentricity”, and ε ₁ and ε ₃ are called “tilt eccentricity”.

The above description is easily generalized when the number of lens surfaces to be inspected is other than four. Therefore, when the lens surface to be inspected is spherical, the eccentricity amount is "the amount of deviation between the center of curvature and the reference optical axis", and when the lens surface to be inspected is aspherical surface, the "shift eccentricity amount and tilt eccentricity amount" are The amount of eccentricity is determined by the two amounts.

The eccentric direction is determined by the direction in which the plane including the paraxial curvature center and the reference optical path faces in the plane orthogonal to the reference optical axis even when the lens surface to be inspected is aspherical. The lens surface eccentricity measuring apparatus of the present invention is an apparatus for carrying out the method according to claim 1, that is, "one or more desired lens systems in three or more lens surfaces including one or more aspherical surfaces". An apparatus for obtaining the amount of eccentricity and the direction of eccentricity of the lens surface to be inspected ", which has a holding means, an illumination light source, an irradiation optical system, an imaging optical system, a barycentric position detecting means, and a computing means. .

The "holding means" is a means for holding the lens system under test by making the reference optical axis of the lens system under test substantially coincide with the central axis. The “light source for illumination” is a light source that emits light for illumination, and LDs, LEDs, and various laser light sources such as gas lasers and solid-state lasers can be preferably used.

The "irradiation optical system" is an optical system in which the optical axis is aligned with the central axis of the holding means, and the light beam from the illumination light source is applied to the lens system to be inspected as a converging or diverging irradiation light beam. is there. Therefore, the irradiation light flux is emitted from the “reference optical axis direction of the lens system to be inspected”. "Imaging optical system"
Has an optical axis substantially aligned with the central axis of the holding means,
It is an optical system for forming an image of a reflected light beam from a desired lens surface to be inspected. The imaging optical system can share a part of the optical system with the irradiation optical system.

The "center-of-gravity position detecting means" is means for detecting the center-of-gravity position of the image of the reflected light from the desired lens surface to be inspected, based on the image formation state of the image forming optical system. "Calculator"
Is a means for calculating the eccentricity amount and the eccentric direction of each lens surface to be measured by a predetermined calculation based on the detection result of the center-of-gravity position detecting means and the data of the lens to be measured, and specifically, a personal computer Or a microcomputer,
Alternatively, a dedicated CPU can be used.

The "centroid position detecting means" is composed of a single image pickup means, a single image processing device for detecting the center of gravity of an image formed on the light receiving surface of the image pickup means, and a focusing optical system. And a converging point position adjusting means for displacing and adjusting the converging point position of the irradiating light flux in the reference optical axis direction (claim 4).

The "centroid position detecting means" is provided at a predetermined position, one on each of the divided optical paths and an optical path dividing means for dividing the image side optical path of the imaging optical system into a plurality of parts. The image pickup means and the image processing means for detecting the center of gravity of the image formed on the light receiving surface of each of the image pickup means may be included (claim 5).

As described above, the reference optical axis of the lens system to be inspected may be considered as "the central axis of the lens barrel holding the lens system to be inspected", and the holding means substantially has the central axis as the reference optical axis. The eccentricity measured in the invention according to claims 3 to 5 is actually the eccentricity with respect to the central axis of the holding means. If the "reference optical axis as the optical axis of" does not coincide with the central axis of the holding means, the measured eccentricity amount includes an error.

In such a case, the calculating means "calculates the least square of the amount of eccentricity of each test lens surface obtained by a predetermined calculation based on the detection result of the barycentric position detecting means and the data of the test lens. The optimum reference optical axis is obtained by averaging, and based on this optimum reference optical axis, it has a calculation function to obtain the amount of eccentricity. " A more accurate amount of eccentricity can be measured based on "(Claim 6).

As described above, the data of the lens system to be tested (radius of curvature of each lens surface, aspherical surface shape, surface spacing, refractive index of lens material, etc.) is used for the calculation in the calculating means. It is premised that various data (designed values) are known, and the amount of eccentricity is minute.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the invention described in claims 3 and 4. The test lens system 1 has a plurality of lenses. The lens system to be inspected may be a lens system in the process of being assembled (a lens system in the process of being assembled) in which some of the lenses (a plurality of lenses) have been assembled in the process of being configured as a lens system. A lens system (complete lens system) already assembled may be used.

When the lens surface eccentricity is measured by using the "lens system being assembled" as the lens system to be inspected, the assembly of each lens can be adjusted based on the measurement result. If the "finished lens system" is used as the lens system to be tested and the eccentricity of all lens surfaces is measured, it can be known whether or not the finished lens system actually conforms to the standard as a product.

The lens system 1 to be tested is a holding portion 3 of "holding means".
Held at A. The holding means is a holding portion 3A and an adjusting mechanism 3B.
Composed of and. The adjusting mechanism 3B is configured by combining a stage that is movable in two directions orthogonal to each other in a plane orthogonal to the drawing and a tilting mechanism that adjusts the direction of the central axis of the holding portion 3A (central axis of the holding means). ing.

The holder 3A holds the reference optical axis of the lens system 1 to be inspected (here, it is assumed to be the central axis of the lens barrel) so as to match the central axis.

The irradiation light flux emitted from the laser light source 4 which is the "illumination light source" becomes a divergent light flux after being narrowed down by the lens 5 which operates similarly to the objective lens of the microscope, and becomes 1/1 with the polarization beam splitter 6. The light passes through the four-wave plate 7, is returned to a parallel light flux by the lens 8, is folded back by the mirrors 9 and 10, and is converged by the lens 11 to illuminate the lens system 1 to be tested. Therefore, the lens 5, the polarization beam splitter 6, the quarter-wave plate 7, the lens 8, the mirror 9,
The lens 10 and the lens 11 form an "illumination optical system".
Of course, the lenses 5, 8 and 11 are "optical axis aligned".

By the adjusting mechanism 3B of the holding means, the holding portion 3A
The central axis of the holding unit is made to match the optical axis of the lens 11 by adjusting the posture of the lens. If the above irradiation is performed in this state, the irradiation light beam is emitted from the reference optical axis direction of the lens system 1 to be inspected.

The lens 11 is mounted on a stage 12 which is moved by a stepping motor 14 and is movable in the optical axis direction. The reference position of the stage 12 is detected by the origin sensor 13. Therefore, the position of the lens 11 is determined by the “origin position” set by the origin sensor 13 and the “polarity and pulse number” of the pulse applied to the stepping motor.

As described above, by displacing the lens 11 in the optical axis direction thereof, it is possible to displace the condensing point position of the converging irradiation light beam in the reference optical axis direction.

The light beam reflected by the lens surface of the lens system 1 to be tested is an objective lens 11, mirrors 10 and 9, lenses 8 and 1,
The light travels in the opposite direction to the / 4 wavelength plate 7, is reflected by the polarization beam splitter 6, is further reflected by the mirror 15, and then reaches the CCD camera 19 via the reticle 16, the microscope objective lens 17, and the field lens 18.

The reticle 16 is at a position substantially conjugate with the position of the focal point of the light beam irradiated by the lens 11 (focal position of the lens 8).
Have been deployed to. The lens 11, the mirrors 10 and 9,
Lens 8, quarter wave plate 7, polarization beam splitter 6,
The mirror 15 and the reticle 16 form an “imaging optical system”.

The reticle 16 is arranged so as to be substantially orthogonal to the optical axis of the image forming optical system, and the image forming state on the reticle 16 is enlarged by the microscope objective lens 17 and the field lens 18 to be taken by the CCD camera 19. An image is formed on the light receiving surface. The reticle 16, the microscope objective lens 17, the field lens 18, and the CCD camera 19 constitute a single "imaging means" in the invention of claim 4. The light receiving surface of the CCD camera 19 is the “light receiving surface of the image pickup means”.

The output of the CCD camera 19 is the image processing device 2.
0, the image processing apparatus 20 detects the center of gravity of the image formation on the light receiving surface of the CCD camera 19. The state of input to the image processing device 20 is observed by the monitor 21.

A computer denoted by reference numeral 22 in FIG. 1 is "calculation means" and receives "input from the image processing apparatus 20" to perform "calculation of eccentricity amount and eccentric direction". The computer 22 also controls the origin sensor 13 and the stepping motor 14.

Therefore, the stage 12, the origin sensor 13, the stepping motor 14 and the computer 22 described above are used.
Constitutes the "focus point position adjusting means" in the invention according to claim 4, and the focus point position adjusting means, the "imaging means", the image processing device 20 (and the monitor 2 if desired).
1) constitutes the "centroid position detecting means" in the invention of claim 4.

Hereinafter, for the sake of concreteness of description, the lens system to be inspected 1 includes the lens surfaces S ₁ , S ₂ , S ₃ and S ₄ shown in FIG. 4 as "desired lens surfaces to be inspected". A case will be described in which the eccentric amount and the eccentric direction of these lens surfaces to be measured are measured in the above order (claim 2). Also, the lens surface S to be inspected
_In the following description, ₁ is the "first surface of the lens system to be tested".

As described above, first, the lens surface S ₁ to be inspected
The eccentricity amount and the eccentricity direction of are measured.

The measurement is performed according to the following procedure. As shown in FIG. 1, the lens system 1 to be tested is attached to a holding portion 3A of "holding means".
Then, the holding mechanism of the lens system to be inspected 1 is adjusted by the adjusting mechanism 3B, and the reference optical axis (for the time being, the central axis of the lens barrel of the lens system to be inspected) is aligned with the optical axis of the irradiation optical system. Let Thereby the reference optical axis also coincides with the optical axis of the imaging optics. The lens 11 is at the origin position.

Data relating to the lens system 1 to be tested is input to the computer 22 in advance or at the time of measurement. The computer 22 also stores a program that defines procedures and calculations required for measurement.

When the lens system 1 to be tested is properly held by the holding means and the preparation for measurement is completed, the laser light source 4 is caused to emit light.
The emitted light beam is converted into a convergent irradiation light beam by the irradiation optical system and is applied to the lens system 1 to be inspected. Computer 2
Reference numeral 2 controls the stepping motor 14 to displace the lens 11 in the optical axis direction so that the focal point position of the irradiation light beam is the designed paraxial curvature center of the lens surface S _{1 to} be measured (point S ₁ 'in FIG. 1).
However, since it is a designed position, the position of the lens 11 is determined so as to match the assumed position on the reference optical axis 2. For this position setting, the computer 22 calculates the displacement amount of the lens 11 based on the data of the lens system to be inspected.

The irradiation light beam reflected by the lens surface S ₁ to be inspected forms an image on the reticle 16 by the action of the image forming optical system, and the image formation state is enlarged and formed on the light receiving surface of the CCD camera 19. To be done. The image formation state on the light receiving surface of the CCD camera 19 has a "spot-shaped portion in the center". This spot-shaped portion has an object point that is the “origin of divergence” of the light beam reflected by the lens surface S _{1 to} be inspected (imaging optical system and microscope objective lens 17).
And the field lens 18).

The image processing apparatus 20 obtains the center coordinates of the spot-shaped portion as the "center of gravity of image formation". Figure 2
(A) shows this state. In FIG. 2A, the point P ₁
Is the center position of the spot-like portion, and the coordinates: r ₁ , φ ₁ of the center position P ₁ are obtained. Figure 2 (a)
The origin O of the coordinate system is determined in advance by measurement at the position of the optical axis of the imaging optical system on the light receiving surface of the CCD camera 19.

If the paraxial curvature center S ₁ 'of the lens surface S _{1 to} be inspected is located on the reference optical axis, the coordinate: r ₁ = 0, and φ ₁ is naturally zero. If the coordinate: r ₁ is finite, φ ₁ is also finite, and φ _{1 at} this time determines the “eccentric direction”.

When the coordinate r ₁ is not 0, the paraxial curvature center S ₁ 'is not on the reference optical axis 2. At this time, the object point of the spot-like portion is the origin of the divergence of the reflected light flux due to the lens surface S ₁ to be inspected, and is changed from the designed paraxial curvature center position to “the actual paraxial curvature center position and the reference optical axis 2”. Deviation amount from: 2 of σ ₁
It is away from the reference optical axis 2 by "double".

Therefore, the imaging optical system and the microscope objective lens 1
If the imaging magnification of the composite system of 7 and the field lens 18 is m (determined as a constant in the measuring device), r
₁ = m · 2σ ₁ . Computer 22 calculates: r ₁ /
2 m is performed to calculate the shift eccentricity: σ ₁ .

The computer 22 subsequently controls the stepping motor 14 to displace the lens 11 and displace the focal point position of the irradiation light beam by ΔR _{1 in the} reference optical axis direction. If the lens surface S ₁ to be inspected has no eccentricity, then the center of gravity of the image formation on the light receiving surface of the CCD camera 19 coincides with the optical axis position of the image forming optical system (origin O in FIG. 2A). At this time, the object point of the image-forming light flux is the aspherical shape of the lens surface S _{1 to} be tested: f ₁
In (h), the relational expression: ΔR ₁ = {h ₁ / f ₁ '(h ₁ )}
A distance satisfying + f ₁ (h ₁ ) −R ₁ : h ₁ is the center of curvature of the aspherical surface portion distant from the aspherical surface axis S ₁ ″. “R ₁ ” is the lens surface S _{1 to} be inspected
The paraxial radius of curvature of, f ₁ '(h ₁ ) is the derivative of the aspherical expression: f ₁ (h). The displacement amount: ΔR ₁ is calculated by the computer 22 based on the data of the lens system to be inspected.

When this center of curvature is deviated from the reference optical axis, the position of the center of gravity of the image formation on the light receiving surface of the CCD camera 19 becomes something like P ₁ 'in FIG. 2B, and the coordinates: r ₁ , Δ.
The coordinate: r ₁ 'is determined by r ₁ ' and φ ₁ '. At this time,
The amount of deviation of the center of curvature of the aspherical portion from the reference optical axis 2 is r ₁ ′ / 2m.

Then, the computer 22 executes the calculation: U ₁ = (r ₁ / 2m)-(r ₁ '/ 2m), ε ₁ = sin ~ ¹ (U ₁ / ΔR ₁ ). The shift eccentricity amount: σ ₁ , tilt tilt eccentricity amount: ε ₁ , and eccentric direction: φ ₁ with respect to the surface S ₁ are determined.

Subsequently, the eccentricity of the lens surface S _{2 to} be tested is measured. Since the lens surface S _{2 to} be tested is a “spherical surface”, it is only necessary to obtain the eccentricity amount σ ₂ and the eccentric direction: φ ₂ of the center of curvature S ₂ ′. In order to measure the eccentricity of the lens surface S _{2 to} be inspected, the computer 22 controls the stepping motor 14 to displace the lens 11, and the focus point position of the irradiation light beam is changed to the designed position (reference value) of the center of curvature S ₂ ′. (Position on the optical axis 2).

For this purpose, the position of the lens 11 when the irradiation light beam is focused on the designed position of the center of curvature S ₂ 'is calculated by the computer 22 by ray tracing using the data of the lens system 1 to be tested, The computer 22 controls the stepping motor 14 so as to realize the calculated position of the lens 11.

When this state is realized, a distance r ₂ from the optical axis of the image forming optical system to the center of gravity of the image formation on the light receiving surface of the CCD camera and an eccentric direction φ ₂ as its deviation angle are obtained.

Decentering amount of the lens surface S ₂ to be tested: σ ₂ is magnification:
using the m ₂ given by the "r ₂ / m _2". The magnification m ₂ is a magnification according to the “composite system of lenses located between the lens surface S ₂ to be inspected and the light receiving surface of the CCD camera 19”, and the shift displacement amount of the lens surface S _{1 to} be inspected is _first obtained. Magnification: different from m.

[0060] That is, test lens surface S ₁ are the first plane as viewed from the incident side of the irradiation light beam, imaging of the reflected light beam by the sample lens surface S _1, the lens surface of the lens system Not affected by refraction. However, the reflected light beam by the sample lens surface S ₂ is refracted by the refractive surface S ₁ on the incident side of the sample lens surface S _2, since the exit from the test lens system 1, from the test lens surface S ₂ Also, the "lens system part to be inspected" on the incident side of the irradiation light flux affects the imaging magnification: m ₂ of the reflected light flux. The computer 22 also calculates the magnification: m ₂ based on the data of the lens system 1 to be tested.

Next, the eccentricity of the lens surface S ₃ to be tested is measured. Since the lens surface S _{3 to} be tested is an aspherical surface, the shift eccentricity amount, the tilt eccentricity amount, and the eccentricity direction are measured. The procedure of eccentricity measurement is the same as the procedure of eccentricity measurement of the lens surface S ₁ to be tested. That is, first, the position of the lens 11 is adjusted so that the irradiation light beam is condensed at the designed position of the paraxial curvature center S ₃ ′ (the displacement amount of the lens 11 is determined by the lens system 1 to be tested).
Calculated by the computer 22 based on the above data). The coordinates of the center of gravity of the image formed on the CCD camera 19 are: r ₃
And the deviation angle: φ ₃ are obtained by the image processing device 20.

Magnification: m ₃ (calculated by the computer 22 based on the imaging magnification of the composition system of the lens between the lens surface S ₃ to be tested and the light receiving surface of the CCD camera 19), shift eccentricity: σ ₃ = r ₃ / m ₃ is obtained, and from this, the shift eccentricity amount: σ ₃ and the eccentric direction: φ ₃ are known.

Next, the aspherical shape of the lens surface S _{3 to} be tested:
In f ₃ (h), the relational _{expression: ΔR 3 = {h 3 /} f 3 '(h 3)} + f 3 (h 3) the distance satisfies -R _3: h ₃ only, the aspherical axis S _3' ' The converging position of the irradiation light flux is displaced to (the designed position of) the curvature center of the aspherical surface portion away from. At this time, the amount of displacement of the focusing position is ΔR ₃ , and the amount of displacement of the lens 11 for realizing this displacement is calculated from the data of the lens system 1 to be measured by the computer 2
Calculated by 2.

When the barycentric position of the spot image on the light receiving surface of the CCD camera 19 at this time is r ₃ ′, the deviation amount of the center of curvature of the aspherical portion from the reference optical axis 2 is “r ₃ ′ / 2.
m ₃ ”.

The computer 22 performs the calculation: U ₃ = (r ₃ / 2m ₃ )-(r ₃ '/ 2m ₃ ), ε ₃ = sin ~ ¹ (U ₃ / ΔR ₃ ), and tilt eccentricity: ε ₃ To calculate.

Finally, the eccentricity of the lens surface S ₄ to be tested is measured. Since the lens surface S _{4 to} be tested is a spherical surface, the measurement procedure is the same as in the case of measuring the eccentricity of the lens surface S ₂ to be tested,
The center of gravity of the imaging on the light receiving surface of the CCD camera 19: the r ₄ eccentricity: magnification when determining the sigma _4: m _4, the lens located between the light receiving surface of the lens surface S ₄ and the CCD camera 19 Is an image forming magnification (needless to say to be calculated by the computer 22) of the composite system of, and the eccentricity amount: σ ₄ = r ₄ / m ₄
Therefore, the eccentric direction is determined by the declination of the center of gravity position: φ ₄ . In this way, the eccentricity measurement for the lens surfaces S _{1 to} S ₄ to be tested is completed. In the above description, the lens surface S ₁ to be inspected
For each of S ₄ , the image processing device performs r _i (i = 1 to
Calculation every time a 4) and the like are determined: was performed r _i / m _i, etc. After performing the measurement of r _i, such as required for the operation for all of the lens surfaces, operations on r _i like May be performed collectively.

As shown in FIG. 4, the lens surface S _{3 to} be inspected is a concave surface toward the side where the irradiation light beam is irradiated, and the paraxial curvature center S ₃ ′ is the lens surface S _{3 to} be inspected. It is on the incident side of the irradiation light flux to ₃ . Therefore, in this case, the irradiation light beam to the lens surface S ₃ to be inspected is a divergent light beam. From this fact, when all the lens surfaces to be measured for eccentricity measurement have concave surfaces facing the incident side of the irradiation light flux, the irradiation optical system can focus the light on the focusing property as described above. It will be easily understood that it is also possible to irradiate the divergent irradiation light flux instead of the above irradiation light flux.

FIG. 3 is a diagram for explaining one embodiment of the invention described in claim 5. In FIG. In order to avoid complication, the parts which are not likely to be confused are given the same reference numerals as in FIG.

In this embodiment, the "centroid position detecting means" is a semi-transparent mirror 15 ', 15A, 15B, 15 as an optical path dividing means for dividing the image side optical path of the imaging optical system into a plurality of parts.
C ,. ． And the image pickup means 16A, 16B, 16 provided at predetermined positions, one on each of the divided optical paths.
C ,. ． And image processing means 20 and 21 for detecting the center of gravity of the image formed on the light receiving surface of each image pickup means.

The reticle 16, the microscope objective lens 17, the field lens 18, and the CCD camera 19 are the image pickup means 16A, 16B ,. ． Together with this, it constitutes one imaging means. The individual image pickup means 16A, 16B ,. ． Each is a reticle, microscope objective lens, field lens, CC
An output of the CCD camera of each image pickup means can be input to the image processing apparatus 20 via an “input switching means” (not shown). In addition to this case, an image processing device is individually provided to each image pickup unit, and the output of each image processing device is output to the computer 22.
May be input to.

Each image pickup means forms a spot-like image in the reflected light beam from the lens system to be inspected whose object point is the center of curvature, the center of paraxial curvature, and a position ΔR _i away from the center of paraxial curvature. Has a light receiving surface at a position where is obtained (preliminarily calculated and determined based on the data of the lens system 1 to be tested). That is, one image pickup unit is required when the lens surface to be inspected is a spherical surface, and two image pickup units are required when the lens surface to be inspected is an aspherical surface. In the case shown in FIG. You will need it. In this case, it is not necessary to move the lens 11 in the optical axis direction.

In this embodiment, the r _i and r _i 'φ _i are determined by the output of each image pickup means, and the above-mentioned calculation is performed based on them to perform the eccentricity measurement for all the lens surfaces to be inspected. You can Unlike the above-mentioned embodiment,
Since it is not necessary to displace the lens 11 with respect to the lens surface to be inspected to sequentially obtain the eccentricity data, the eccentricity measurement can be efficiently performed.

In each of the embodiments described above, the reference optical axis of the lens system to be tested is considered to be the central axis of the lens barrel of the lens system to be tested 1, and this is matched with the central axis of the holding means for measurement. However, the reference optical axis of the lens system to be inspected is originally the designed optical axis, and does not always match the central axis of the lens barrel.

In such a case, an error occurs in the measured eccentricity amount depending on the deviation between the original reference optical axis and the center axis of the lens barrel (center axis of the holding means). In order to effectively reduce this error, as in the invention according to claim 6, "calculation means"
Is the "optimum" based on the least square mean of the eccentricity amount of each lens surface to be inspected, which is obtained by the predetermined calculation based on the detection result of the barycentric position detecting means and the data of the lens to be inspected. A reference optical axis "may be obtained, and based on the optimum reference optical axis, a calculation function for obtaining the eccentricity amount may be provided.

[0075] That is, for example, the aforementioned eccentricity: Based on the sigma ₁ to _{σ 4, Σ (σ i -δ} ) 2 obtains the [delta] ₀ that minimizes the, instead of such σ _i (σi-δ ₀ ) Is used to repeat the operation. In this way, the eccentricity can be accurately measured.

Further, the holding means is provided with a rotation mechanism, and the held lens system to be tested is rotated about the central axis of the holding means. At this time, the radius of gyration of the center of the spot-shaped image on the light receiving surface of the image pickup means is determined. The r _{i and the} like may be obtained.

[0077]

As described above, according to the present invention, a novel lens surface decentering measuring method and apparatus can be realized. According to the present invention, it is possible to easily and accurately measure decentering of a desired lens surface to be tested in a lens system having three or more lens surfaces and including an aspherical surface.

[Brief description of drawings]

FIG. 1 is a diagram for explaining one embodiment of a lens surface eccentricity measuring device of the present invention.

FIG. 2 is a diagram for explaining eccentricity measurement in the above embodiment.

FIG. 3 is a diagram for explaining another embodiment of the lens surface eccentricity measuring device of the present invention.

FIG. 4 is a diagram for explaining decentering of a lens surface to be inspected in a lens system to be inspected.

FIG. 5 is a diagram for explaining an aspherical shape.

[Explanation of symbols]

1 Test lens system 3A, 3B holding means 4 Lighting light source 5,6,7,8,9,10,11 Irradiation optical system 6,7,8,9,10,15 Imaging optical system 16, 17, 18, 19 Imaging means 19 Image processing device 22 Computing means

Continuation of front page (56) Reference JP-A-2-99841 (JP, A) JP-A-3-107739 (JP, A) JP-A-5-312670 (JP, A) JP-A-9-145537 (JP , A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01M 11/00-11/08

Claims (6)

(57) [Claims] 1. A method for obtaining a desired decentering amount and decentering direction of a lens surface to be inspected in a lens system to be inspected having three or more lens surfaces including one or more aspherical surfaces, which is a reference of the lens system to be inspected. From the optical axis direction, a desired test lens surface is irradiated with a converging or diverging irradiation light beam, and the reflected light beam from the test lens surface is substantially aligned with the reference optical axis. By the image optical system, an image pickup means is provided as an image with the curvature center of the lens surface to be inspected, or each of the paraxial curvature center and the curvature center of the aspherical portion at a predetermined distance from the aspherical surface as object points. An image is formed on the light-receiving surface of, and a predetermined calculation is performed using the barycentric position coordinates of each image and the data of the lens system under test to obtain the eccentric amount and the eccentric direction of the desired lens surface under test. Characteristic lens surface eccentricity measurement method. 2. The lens surface eccentricity measuring method according to claim 1, wherein when there are two or more lens surfaces to be inspected, the eccentricity amount and the eccentric direction of each lens surface to be inspected are sequentially measured from the irradiation side of the irradiation light beam. A lens surface eccentricity measuring method characterized by the above. 3. An apparatus for determining an eccentricity amount and an eccentric direction of one or more desired lens surfaces to be tested in a lens system to be tested having three or more lens surfaces including one or more aspheric surfaces. The reference optical axis of is substantially aligned with the central axis of the holding means for holding the lens system to be tested, the illumination light source, and the central axis of the holding means is aligned with the optical axis, Has an optical axis for irradiation that irradiates the lens system under test as a convergent or divergent beam of light, and an optical axis that substantially matches the above-mentioned central axis, and reflects the light beam reflected from the desired lens surface under test. An image forming optical system for forming an image, a barycentric position detecting means for detecting a barycentric position of an image of reflected light from a desired lens surface to be inspected on the basis of an image forming state by the image forming optical system, and this barycentric position detection. Based on the detection result by the means and the data of the lens under test Lens surface eccentricity measuring apparatus characterized by having a calculating means for calculating an eccentric direction and the eccentric amount of each test lens surface by a predetermined calculation. 4. The lens surface eccentricity measuring device according to claim 3, wherein the center-of-gravity position detecting means includes a single image-capturing means and a single center-of-gravity for detecting the center of gravity of the image formed on the light-receiving surface of the image-capturing means. An image processing device, and a condensing point position adjusting means for displacing / adjusting the condensing point position of the converging or diverging irradiation light beam by the irradiation optical system in the reference optical axis direction. Lens surface eccentricity measuring device. 5. The lens surface eccentricity measuring device according to claim 3, wherein the center-of-gravity position detecting means divides the image-side optical path of the imaging optical system into a plurality of optical path dividing means, and one on each of the divided optical paths. A lens surface eccentricity measuring device characterized by comprising image pickup means provided at predetermined positions and image processing means for detecting the center of gravity of the image formed on the light receiving surface of each image pickup means. . 6. The lens surface eccentricity measuring device according to claim 3, 4 or 5, wherein the calculating means obtains each by a predetermined calculation based on the detection result by the barycentric position detecting means and the data of the lens to be inspected. A lens surface eccentricity measuring device having a calculation function for obtaining an optimum reference optical axis by a least square mean of the eccentricity amount of a lens surface to be inspected and for obtaining the eccentricity amount based on the optimum reference optical axis.