JP2001141608A - Equipment and method for measuring chromatic aberration of radial grin lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an equipment and a method for measuring the Abbe number, i.e., the chromatic aberration or chromatic aberration parameter, of a medium of a radial GRIN lens easily and accurately. SOLUTION: The equipment for measuring the chromatic aberration of a sample lens, i.e., a radial GRIN lens 1, comprises a light source 3 emitting a plurality of wavelengths, a test target 2, and an imaging position detecting mechanism 8 and measures the chromatic aberration by detecting the difference of imaging position of the test target 2 due to difference of wavelengths emitted from the light source 3 wherein the radial GRIN lens 1 has planar surfaces on the opposite sides.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a radial GRI.
The present invention relates to a measuring device and a measuring method for measuring chromatic aberration of an N lens.

[0002]

2. Description of the Related Art In an imaging lens system used for imaging of a camera or the like, a radial GRIN lens element having a distribution of refractive index inside a lens is expected as an effective means for reducing the number of lenses and improving optical performance. Have been. In the radial type GRIN lens, the medium has a refractive index distribution in a direction perpendicular to the optical axis, and the refractive index distribution n
(R) is represented by the following equation (2). n (r) = N ₀ + N ₁ r ² + N ₂ r ⁴ + N ₃ R ⁶ + (2) where N ₀ is the refractive index on the optical axis at the reference wavelength, N
_.. (i = 1, 2, 3,...) are coefficients representing the refractive index distribution, and r is the distance from the optical axis in the vertical direction.

The Abbe number of this radial GRIN lens when the d-line is used as a reference wavelength is given by the following equations (3) and (4). V ₀ = (N _0d −1) / (N _0F −N _0C ) (i = 0) (3) V _i = N _id / (N _iF −N _iC ) (i = 1, 2, 3 _,. .....) (4) where, d, C, F is the symbol representing the Fraunhofer lines, for example, N _id coefficients of N _i to the d-line (i = 0,
1, 2, 3,...).

At this time, the axial chromatic aberration PAC generated by the radial GRIN lens is approximately given by the following equation (5). PAC = K [(φ _S / V ₀ ) + (φ _m / V ₁ )] (5) where φ _S is the power of the surface of the radial GRIN lens,
φ _m is the power of the medium of the radial type GRIN lens, and K is a constant depending on the axial ray height and the exit angle from the final surface of the lens.

[0005] Radial type G having both surfaces formed in a plane shape
In the RIN lens, since the power φ _S = 0 of the surface of the radial GRIN lens, the generated axial chromatic aberration PAC is approximately expressed by the following equation (6). PAC = Kφ _m / V ₁ (6)

Further, it is known that in order to maximize the effect of the radial type GRIN lens from the viewpoint of optical design, a material having a low dispersion such that the absolute value of the Abbe number V ₁ of the medium becomes large is required. ing. The Abbe number V ₁ was, the formula (5) is a parameter which greatly influences the occurrence of chromatic aberration in the radial GRIN lens medium as can be seen from (6), the Abbe number V ₁ in the actual material Accurate measurement of the value is a very important issue in developing a radial GRIN lens.

As a method for measuring the value of the Abbe number V ₁ , there are a plurality of different methods using a refractive index profile measuring device for detecting a critical angle, as described in Japanese Patent Application Laid-Open No. Hei 4-13948. performs detection of critical angle with a wavelength, there is a method of determining the value of the Abbe number V ₁ from the difference between the profile at different wavelengths.

[0008]

[SUMMARY OF THE INVENTION However, the method described in JP-A-4-13948, although it is possible to determine the value of the Abbe number V _1, there is a problem that the measurement accuracy is poor. The present invention aims to provide a measuring instrument and a measuring method capable of easily measuring the value of the Abbe number V ₁ is a chromatic or chromatic parameters of the medium of accurately radial type GRIN lens.

[0009]

In order to solve the above-mentioned problems, a chromatic aberration measuring device for a radial type GRIN lens according to the first aspect of the present invention comprises a light source emitting a plurality of wavelengths or a plurality of light sources emitting different wavelengths from each other. And a test target, and an imaging position detection mechanism, wherein the chromatic aberration measuring device measures the chromatic aberration of the sample lens by detecting a difference in the imaging position of the test target image due to the different wavelengths emitted from the light source. The sample lens is a radial GRIN lens having both surfaces formed in a planar shape.

The radial GR according to the second aspect of the present invention.
The chromatic aberration measuring device for the IN lens has a light source emitting a plurality of wavelengths or a plurality of light sources each emitting a different wavelength, and a deflection angle detection mechanism for a light beam from the light source, and a light beam having a different wavelength emitted from the light source. A chromatic aberration measuring device for measuring the chromatic aberration of a sample lens by detecting a difference in the angle of deviation of the sample lens, wherein the sample lens is a radial GRIN lens having both surfaces formed in a planar shape.

Further, the method for measuring chromatic aberration of a radial GRIN lens according to the present invention comprises measuring chromatic aberration generated in a radial GRIN lens having both surfaces formed in a planar shape.
The method is characterized in that the Abbe number of the medium is calculated from the amount of chromatic aberration using a successive approximation method by ray tracing.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a radial type G according to the present invention
The operation of the chromatic aberration measuring device for the RIN lens will be described.
In the measurement method using a critical angle described in JP-A-4-13948, which is shown as a conventional example, only the refractive index information of one section of a radial type GRIN lens medium as a sample is obtained, and the polished state of the surface is obtained. Etc.,
Further, since the in the process of converting the measured data of the value of the Abbe number V ₁ it is necessary to use the fitting method, there is a problem that errors occurring in the process is great.

In order to measure the value of the Abbe number V ₁ with high accuracy, it is necessary to use the light propagating through a medium having a certain thickness, and to directly convert the value to the Abbe number V ₁ as directly as possible. It is effective to detect. Therefore, in the present invention, the chromatic aberration is directly detected by the light propagating through the medium of the radial type GRIN lens.

FIG. 1 is a diagram showing the measurement principle of the chromatic aberration measuring apparatus according to the first invention. In this chromatic aberration measuring device, first, an object 2 such as a test target arranged on the optical axis of a radial GRIN lens sample 1 is illuminated with light of a certain wavelength using a light source (not shown), and the radial GR
An image formed by the IN lens sample 1 is formed, and then the object 2 is illuminated with a wavelength different from the above-mentioned wavelength using an illuminating means to form an image formed by the radial GRIN lens sample 1. . The deviation Δ of the imaging position when the object 2 is illuminated with these two wavelengths corresponds to the axial chromatic aberration due to the difference between the two wavelengths, and depends on the Abbe number V ₁ of the medium of the radial type GRIN lens. Things. Therefore, by detecting the deviation Δ of the imaging position at the time of illuminating the object 2 with these two different wavelengths can be obtained by converting the value of the Abbe number V _1.

At this time, it is preferable that both surfaces of the radial type GRIN lens sample 1 are formed in a planar shape. If both surfaces are not flat but have a curvature, as shown in the above equation (5), the generated chromatic aberration includes the power φ _S of the surface of the radial type GRIN lens and the value of the Abbe number V ₀ . It will be come strongly related, in that case, when the converted value of the Abbe number V ₁ from the measured chromatic aberration, the value of the power phi _S and Abbe number V ₀ which surface is required, error It will be large. In this respect, if the both surfaces of the radial type GRIN lens sample 1 as in the present invention is in a planar shape, the amount of chromatic aberration is given approximately by the equation (6), easily in terms of the Abbe number V ₁ It is convenient.

The conversion into the Abbe number V ₁ is performed as follows. The values of the focal length f _d and the Abbe number V ₁ are approximately given by the following equations (7) and (8). _{f d ≒ -1 / 2N 1d t} m ...... (7) V 1 = N 1d / (N 1F -N 1C) ≒ f d / (f C -f F) ...... (8) where, N ₁ is a refractive Coefficients representing the rate distribution, d, C, and F are symbols representing the Franchoffer line. For example, N _1d indicates the N ₁ coefficient for the d line. Also, t _m is a radial type GRI.
This is the thickness of the N lens sample.

First, in order to use the above-described measurement principle, an axial chromatic aberration Δ is determined using a C-line and an F-line as two wavelengths by using a chromatic aberration measuring machine in which both surfaces of a radial type GRIN lens 1 are formed in a planar shape. measured, and the measured value and delta _M.
Further, the focal length f _d of the d-line is measured by another measuring device such as an optical bench, and the measured value is defined as f _dM . By approximating these values as Δ ≒ f _C −f _F and substituting them into the above equation (8), the approximate Abbe number V ₁ can be easily obtained.
Can be obtained.

Here, when the conversion to the Abbe number V ₁ is strictly performed, a method of successive approximation by ray tracing is effective. FIG. 2 shows a flowchart for obtaining a strict Abbe number V ₁ value by a successive approximation method by ray tracing.
First, the coefficient N _1d and the Abbe number V ₁ are converted to an appropriate initial value N _1d
(0) and the initial value V ₁ (0) (step S
1). As the initial value, it is effective to use the approximate value obtained by the above equations (7) and (8), but another value may be used. Then, by the technique of ray tracing, calculating the focal length f _dc and chromatic delta _C for those values (step S
2). At this time, values measured separately are used for the thickness t _m , the axial refractive index N _0, and the imaging magnification of the radial GRIN lens sample. The d-line and C shown in the following equation (9)
The fact that the partial dispersion ratio θ _1dC of the medium between the line and the line is usually about 0.3 is used. θ _1dC = (N _1d −N _1C ) / (N _1F −N _1C ) (9)

Next, regarding the focal length of the d-line and the longitudinal chromatic aberration due to the C-line and the F-line, the difference between the calculated value and the measured value is ε ₁ = f _dC −F _dM and ε ₂ = Δ _C −Δ _{M, respectively.} Is calculated (step S3), and it is determined whether both the values of ε ₁ and ε ₂ are 0 (step S4). In this case, even if the values of ε ₁ and ε ₂ are not strictly 0, it is sufficient if it can be determined to be almost 0 in consideration of the allowable error. For example,
If the absolute values of ε ₁ and ε ₂ are equal to or less than 10 ⁻² , it may be determined to be 0, for example, in consideration of an allowable error.

When it can be determined that the values of ε ₁ and ε ₂ are both 0, the values of N _1d and V ₁ at that time are the values obtained respectively (step S5). When at least one of the values of ε ₁ and ε ₂ cannot be determined to be 0, the values of N _1d and V ₁ at that time are given by the following equations (10),
As a value obtained by subtracting the correction amount as given in (11) (step S6), the process returns to the calculation process by ray tracing. _{N 1d = N 1d - (δN} 1d / δf dc) ε 1 ...... (10) V 1 = V 1 - (δV 1 / δΔ C) ε 2 ...... (11)

In the chromatic aberration measuring apparatus according to the first aspect of the present invention, in order to secure sufficient measurement accuracy, the radial type G
The thickness t _m of the medium of the RIN lens sample is given by the following conditional expression (1)
It is desirable to satisfy _{0.05 <t m /p<0.2 ...... (1} ) where, p is a pitch of the radial type GRIN material, the following formula
Given by (12). p = 2π (N ₀ / −2N ₁ ) ^1/2 (12) If the lower limit of conditional expression (1) is exceeded, the measurement accuracy is not sufficient. If the upper limit is exceeded, an image is formed in the sample. A case occurs, which is not preferable.

FIG. 3 shows the measurement result of the chromatic aberration measuring apparatus of the second invention.
FIG. In this chromatic aberration measuring instrument,
Ray-shaped GRIN lens sample 1
A light beam of a certain wavelength is incident using a light source such as a laser.
The incident light flux is refracted inside the radial type GRIN lens 1.
It is bent by the rate gradient, and as a result, the emitted luminous flux enters
It is bent by a certain declination θ with respect to the shooting direction. Next
The incident position and direction of the luminous flux
Then, the luminous flux having different wavelengths is converted into a radial type GRIN lens.
Incident on the noise sample 1. The declination at this time is θ + Δθ
Thus, they differ by a small angle Δθ. This
Is equivalent to chromatic aberration due to two wavelengths
And the Abbe number V of the radial GRIN lens medium ₁Depend on
It exists. So at these two different wavelengths
The luminous flux enters the radial GRIN lens sample 1
By detecting the deviation Δθ of the declination when shooting,
Abbe number V₁The value of
You.

Also at this time, it is desirable that the radial type GRIN lens sample 1 has both surfaces formed in a planar shape. If both surfaces are not flat but have a curvature, as shown in the above equation (5), the generated chromatic aberration includes the power φ _S of the surface of the radial type GRIN lens and the value of the Abbe number V ₀ . It has a lot to do with it. In this case, when converting the value of the Abbe number V ₁ from the measured chromatic aberration, the value of the power phi _S and Abbe number V ₀ which surface is required, error occurs greatly. In this regard, when the planar shape of both sides of the radial type GRIN lens sample 1 as in the present invention is given by the occurrence of chromatic aberration is approximately the conditional expression (6), in terms of bookmarks in the Abbe number V ₁ It is easy and convenient.

The conversion into the Abbe number V ₁ can be performed by a method according to the procedure used in the chromatic aberration measuring apparatus of the first invention. Further, in the aberration measuring machine according to the second aspect of the invention, in order to ensure sufficient measurement accuracy, it is desirable that the thickness t _m of the medium of the radial type GRIN lens sample satisfies the following condition (1). 0.05 <When the lower limit of t _m /p<0.2 ...... (1) The condition (1), the measurement accuracy is not sufficient, and when it exceeds the upper limit, varying within the radial type GRIN sample A case where the beam undulates with a curved point occurs, which is not preferable.

Next, an embodiment of a chromatic aberration measuring device for a radial type GRIN lens according to the present invention will be described with reference to the drawings. Embodiment 1 FIG. 4 is a schematic configuration diagram showing a first embodiment of a chromatic aberration measuring apparatus according to the present invention. The chromatic aberration measuring apparatus according to the present embodiment is an embodiment of the first chromatic aberration measuring apparatus, and includes a mercury lamp 3 as a light source, a band-pass filter 4, a diffuser 5, a resolution chart 2 as a test target, and a radial GRIN. It comprises a lens sample 1, a ground glass 6, an eyepiece 7, and the like.

The band pass filter 4 is a mercury lamp 3
Is used to pass light of a desired wavelength only, and one that transmits the desired wavelength is prepared. At first, the one for the C line is set. Then, the light emitted from the mercury lamp 3 illuminates the resolution chart 2 via the band-pass filter 4 for C-line and the diffuser 5, and a radial type GRIN lens sample 1 having both surfaces polished into a planar shape.
To form an image of the chart. Then, the image forming position of the formed image is read by the eyepiece 7.

Next, the bandpass filter 4 is exchanged for the F-line, the wavelength of the illumination light emitted from the mercury lamp 3 is changed, an image is formed at the wavelength, and the image forming position is read by the eyepiece 7. . Deviation of the imaging position of the two images, which corresponds to the axial chromatic aberration of the C line and the F-line with two wavelengths, is dependent on the Abbe number V ₁ of the radial type GRIN lens medium. Therefore, to detect the shift of the imaging position, it is possible to determine the value of the Abbe number V ₁ by conversion.

The mercury lamp 3 is a light source having a luminance spectrum such as C-line and F-line. The band-pass filter 4 is made of an interference film, and can selectively transmit light of one wavelength in the emission line spectrum of the mercury lamp 3. The bandpass filter 4 includes various types such as a d-line, a C-line, an F-line, and a g-line. In the present embodiment, two types of the band-pass filter 4 are used for the C-line and the F-line. The diffuser 5 is a diffusion plate for uniformly illuminating the resolution chart 2 serving as a test target uniformly, and can provide brighter illumination when used together with a condenser lens (not shown). The resolving power chart 2 is a test target to be imaged, and is used for facilitating detection of a light imaging position.

The eyepiece 7 is a specific example of the focus detecting mechanism 8 in the chromatic aberration measuring apparatus of the present invention, and can adjust the position along the optical axis. Explaining the position adjustment, first, in a state where the user looks through the eyes 9 using the band-pass filter 4 for C-line,
The position of the eyepiece 7 is adjusted to focus on the C-line image, and the position of the eyepiece 7 at that time is recorded. Next, the band is replaced with the bandpass filter 4 for the F-line, and the image position of the F-line is refocused. Eyepiece 7 at this time
And the difference between the position of the eyepiece 7 and the position of the eyepiece 7 correspond to the chromatic aberration of the C-line and the F-line. In this case, by disposing a screen such as frosted glass 6 at the focus position of the eyepiece lens 7 as a part of the focus detection mechanism 8, an error occurs in the image position detected by the function of adjusting the focus of the human pupil. This can be avoided.

The measured chromatic aberration is given by the above equation since both surfaces of the radial GRIN lens are polished into a planar shape.
As represented by (6), it is to directly dependent on the value of the Abbe number V _1. Therefore, from the measured chromatic aberration, a value of an Abbe number V ₁ using the method of successive approximation by the approximate expression (8) or ray tracing, as compared with the conventional aberration measuring instrument and measurement method may easily and accurately You can ask.

In the embodiment shown in FIG. 4, the focus detecting mechanism 8 is configured by using the eyepiece 7, but is not limited to the configuration shown in FIG. As shown in FIG.
A focus detection mechanism 8 ′ configured by combining the lens and the eyepiece 7 may be used. In that case, it is desirable to move the objective lens 10 and the eyepiece 7 integrally for focusing. For simple focusing, only the objective lens 10 may be moved. At this time,
Further, by disposing a screen such as frosted glass 6 at the focus position where the objective lens 10 and the eyepiece 7 are aligned, it is possible to prevent an error from occurring in the image position detected by the function of adjusting the focus of the human pupil. be able to.

Further, as another focus detecting mechanism, as shown in FIG. 6, an image pickup surface of an image pickup device 11 such as a CCD is directly arranged at an image forming position, and a CR is outputted via an electric processing circuit 12.
A focus detection mechanism 8 ″ configured to check the focus position based on the image displayed on the T monitor 13 may be applied. In this method, the degree of error caused by the focusing power of the human pupil is different from the method of focusing with eyes as in the case of using the focus detection mechanisms 8 and 8 'shown in FIGS. And the measurement accuracy can be further improved. Further, by automatically and electrically detecting the focus position, it is possible to suppress a variation in measured values by the operator.

Further, in this embodiment, if the g-line measurement is performed in addition to the C-line and F-line measurement, the anomalous dispersion of the medium of the radial type GRIN lens can be obtained. The parameter indicating the anomalous dispersion of the g-line is, for example, the partial dispersion ratio θ of the medium of the radial type GRIN lens.
_1gF , and the partial dispersion ratio θ _1gF is given by the following equation (13). θ _1gF = (N _1g −N _1F ) / (N _1F −N _1C ) (13) where N ₁ is a coefficient representing a refractive index distribution, and g, C, and F are symbols representing a Franchoffer line. For example, N _1g indicates the coefficient of N ₁ for the g line.

In this embodiment, a mercury lamp is used as a light source. However, a laser light source as shown in a second embodiment to be described later or a tunable laser such as a dye laser may be used. When the _Abbe number V ₁ and θ _1gF are obtained using wavelengths other than the C-line, F-line and g-line, it is necessary to perform conversion using a Hertzberger relational expression or the like. Further, in the present embodiment, the resolving power chart is used as the test target, but a chart having another pattern, a slide film, a pinhole, or the like may be used as long as the imaging position can be easily detected.

Embodiment 2 FIG. 7 is a view showing the arrangement of essential parts of a second embodiment of the chromatic aberration measuring apparatus according to the present invention. The chromatic aberration measuring apparatus of the present embodiment
1 shows an embodiment of a chromatic aberration measuring instrument. As a light source,
A He-Ne laser 14 (λ = 633 nm) and an Ar laser 15 (λ = 488 nm) are used. In addition, a half mirror 16 and a reflection mirror 17 are arranged on the optical path of the laser light, and the laser light is adjusted so as to be completely coaxial. The laser beams of these two wavelengths are made incident simultaneously on the surface parallel to the optical axis 18 of the radial type GRIN lens sample 1 whose both surfaces are polished into a planar shape and at a certain height from the optical axis 18 of the lens sample. Inside the radial type GRIN lens sample 1, the laser beam is bent by the refractive index gradient, and the emitted light is bent at an angle with respect to the incident direction. The bending angles are the He-Ne laser beam and the Ar laser beam. Is slightly different, and a deviation Δy occurs at the laser spot position reaching the screen 19. This deviation Δy
Are equivalent to chromatic aberrations at λ = 633 nm and λ = 488 nm.

At this time, since the laser beam has a certain beam diameter, the laser beam after passing through the radial type GRIN lens 1 spreads, and the deviation Δ
There is a case where a problem occurs that y becomes difficult to detect. In such a case, APPLIED OPTICS Vol.22 N
o. 3 Using a mode matching method as shown in P396-399 (1983.2), for example, as shown in FIG.
By squeezing the laser beam through the lens 20 by a predetermined amount so as to be incident on the radial GRIN lens 1, it is possible to reduce the above-described problem that the deviation Δy is difficult to detect.

Further, the deviation Δy on the screen 19 in FIG. 7 is the radial type G at the laser beam incident position.
Although it differs depending on the distance of the RIN lens sample 1 from the optical axis 18, the ratio Δy / y with respect to the overall declination y hardly depends on the position of incidence on the radial GRIN lens sample 1 and corresponds to chromatic aberration. Value. Since the radial type GRIN lens 1 has both sides polished into a planar shape, the chromatic aberration can be obtained by successively approximating the value of the Abbe number V ₁ as represented by the above equation (6). it can. At this time, since the wavelength is not directly a C-line or an F-line, it is necessary to convert the wavelength using a Hertzberger relational expression or the like.

In this embodiment, the light source is He.
If a He—Cd laser (λ = 442 nm) is further added in addition to the −Ne laser 14 and the Ar laser 15, the partial dispersion ratio θ 1 _{gF and the} like can be obtained as in the first embodiment. At this time, it is needless to say that wavelength conversion using the Hertzberger relational expression or the like is necessary.

In this embodiment, the light source is He-N
Although two different wavelength lasers such as the e-laser 14 and the Ar laser 15 are used, a tunable laser such as a dye laser that can oscillate a plurality of wavelengths with one laser may be used. Further, in this embodiment, the laser light is incident on the radial GRIN lens sample 1 in a state where the laser light is parallel to the optical axis 18 of the radial GRIN lens sample 1. However, the laser light is inclined by a known predetermined angle. Radial GRIN lens sample 1
May be incident. However, when converting to the Abbe number V ₁ or the like, it is necessary to consider that it is inclined by a known predetermined angle.

In the above description of the present invention, the d-line,
Although the case where each of the C line, the F line, and the g line is targeted has been described, the basic concept of the present invention can be applied even if the wavelength is changed, such as using the e line as a reference wavelength. Absent. For example, in the case of the e-line reference, the coefficient of the e-line may be used instead of the coefficient of the d-line in each equation to be used.

As described above, the chromatic aberration measuring device and chromatic aberration measuring method for a radial GRIN lens according to the present invention have the following features in addition to the features described in the claims.

(1) The chromatic aberration measuring apparatus for a radial type GRIN lens according to claim 1, wherein the following conditional expression (1) is satisfied. _{0.05 <t m /p<0.2 ...... (1} ) where, p is the pitch of the radial type GRIN material, the t _m is the thickness of the medium of the radial type GRIN lens.

(2) The apparatus for measuring chromatic aberration of a radial type GRIN lens according to claim 2, wherein the following conditional expression (1) is satisfied. _{0.05 <t m /p<0.2 ...... (1} ) where, p is the pitch of the radial type GRIN material, the t _m is the thickness of the medium of the radial type GRIN lens.

[0044]

As evident from the foregoing description, according to the present invention, it is possible to easily measure the value of the Abbe number V ₁ which is chromatic parameters of a medium accurately radial type GRIN lens.

[Brief description of the drawings]

FIG. 1 is a diagram showing a measurement principle of a chromatic aberration measuring device according to the first invention.

FIG. 2 is a flowchart for obtaining a strict Abbe number value by a successive approximation method by ray tracing in the present invention.

FIG. 3 is a diagram showing a measurement principle of the chromatic aberration measuring apparatus according to the second invention.

FIG. 4 is a schematic configuration diagram showing a first embodiment of a chromatic aberration measuring apparatus according to the present invention.

FIG. 5 is a schematic configuration diagram illustrating another example of the focus detection mechanism in the present embodiment.

FIG. 6 is a schematic configuration diagram showing still another example of the focus detection mechanism in the present embodiment.

FIG. 7 is an arrangement diagram of main parts showing a second embodiment of the chromatic aberration measuring apparatus according to the present invention.

FIG. 8 is an arrangement diagram when a mode matching method is used in the present embodiment.

[Brief description of reference numerals]

 DESCRIPTION OF SYMBOLS 1 Radial type GRIN lens sample 2 Test target 3 Mercury lamp 4 Band pass filter 5 Diffuser 6 Ground glass 7 Eyepiece 8, 8 ', 8 "Focus detection mechanism 9 Eye 10 Objective lens 11 CCD 12 Electric processing circuit 13 Monitor 14 He-Ne Laser 15 Ar laser 16 Half mirror 17 Reflecting mirror 18 Optical axis of radial type GRIN lens 19 Screen 20 Lens

Claims (3)

[Claims] A light source emitting a plurality of wavelengths or a plurality of light sources each emitting a different wavelength, a test target, and an imaging position detecting mechanism, wherein a test target image is formed by the different wavelengths emitted from the light source. A chromatic aberration measuring device for measuring chromatic aberration of a sample lens by detecting a difference in image position, wherein the sample lens is a radial GRIN lens having both surfaces formed in a planar shape. Lens chromatic aberration measuring machine. 2. A light source that emits a plurality of wavelengths or a plurality of light sources each emitting a different wavelength, and a deflection angle detection mechanism for the light beam from the light source, wherein the deflection angle of the light beam by the different wavelength emitted from the light source is provided. A chromatic aberration measuring device for measuring a chromatic aberration of a sample lens by detecting a difference between the two types, wherein the sample lens is a radial GRIN lens having both surfaces formed in a planar shape. Chromatic aberration measuring machine. 3. A radial type G having both surfaces formed in a planar shape.
A method for measuring chromatic aberration of a radial GRIN lens, comprising: measuring chromatic aberration generated in an RIN lens, and calculating the Abbe number of a medium from the amount of chromatic aberration by using a successive approximation method by ray tracing.