KR20130083117A - Refractive index measuring method for plastic lens with curvature - Google Patents

Refractive index measuring method for plastic lens with curvature Download PDF

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Publication number
KR20130083117A
KR20130083117A KR1020120003677A KR20120003677A KR20130083117A KR 20130083117 A KR20130083117 A KR 20130083117A KR 1020120003677 A KR1020120003677 A KR 1020120003677A KR 20120003677 A KR20120003677 A KR 20120003677A KR 20130083117 A KR20130083117 A KR 20130083117A
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South Korea
Prior art keywords
refractive index
plastic lens
phase contrast
contrast image
lens
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KR1020120003677A
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Korean (ko)
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엄효순
유영훈
황재학
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(주)미토스
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Priority to KR1020120003677A priority Critical patent/KR20130083117A/en
Publication of KR20130083117A publication Critical patent/KR20130083117A/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
    • G01B11/255—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures for measuring radius of curvature
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0228—Testing optical properties by measuring refractive power
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length

Abstract

In the present invention, the first step of measuring the refractive index of one location of the plastic lens, the refractive index measured in the first step is defined as the average refractive index of the plastic lens, the refractive index matching oil and the average refractive index matched with the average refractive index A second step of preparing relative refractive oils having different refractive indices, a third step of containing the refractive index matching oils and the relative refractive index oils in a container up and down based on a plastic lens, and a third wavelength A fourth step of obtaining a first phase contrast image from a transmission type digital holography microscope by irradiating light from the bottom to an upward direction; and a transmission type digital holography microscope by irradiating light of a second wavelength to the container of the third step from below To obtain the second phase contrast image from the third and third It is a method of irradiating the above direction to measure a third characteristic part by the shape and refractive index of the plastic lens of which comprises a sixth step for obtaining a phase contrast from a transmission digital holographic microscope below is provided.

Description

REFRACTIVE INDEX MEASURING METHOD FOR PLASTIC LENS WITH CURVATURE}

The present invention relates to a method for measuring the shape and refractive index of a plastic lens having a curvature shape, and more particularly, to a method for measuring the shape and refractive index of a plastic lens having a curvature shape such as a phone camera using a digital holography microscope. .

Plastic lenses such as contact lenses and camera lens for mobile phones are lenses that determine the focal length according to the shape. Therefore, when manufacturing a lens having such a curvature shape, it is desirable to keep the refractive indices of all parts the same. However, at the high temperature and high pressure, the molten plastic is pushed in to form a lens, and the pushing pressure must be kept constant during the process. However, when a slight pressure difference occurs during the process, the difference in refractive index occurs for each part of the lens due to the pressure difference. This difference in refractive index may cause a change in focal length.

The prior art for measuring optical parameters of plastic lenses is widely used and little is known about the method of measuring shape and optical parameters simultaneously. U.S. Patent 5,062,297 discloses a method for measuring the profile of an object, wherein an ultrasonic wave is irradiated by an ultrasonic transducer toward an object supported by a support member in water and reflected from the surface of the object. Is detected by the transducer. However, the method disclosed in this patent requires the transducer to move to several measuring points to obtain a number of profiles in order to generate average BC, FC and BC SAG, and thus is inefficient. This measurement technique is inefficient because it requires repeated parameter measurements, resulting in increased cost. The method also uses a diffused ultrasonic beam that is more susceptible to changes in lens curvature and thus is inadequate for use in a toric lens.

U.S. Patent 5,062,297

SUMMARY OF THE INVENTION The present invention aims to solve the above problems, and an object of the present invention is to easily measure the shape and refractive index of various parts of a plastic lens by using a transmission digital holographic microscope.

The above object of the present invention is a method for measuring the shape and refractive index of each part of a plastic lens including a phone lens or a contact lens used in a mobile phone, the first step of measuring the refractive index of one point of the plastic lens, and the first step Defining the refractive index measured by the average refractive index of the plastic lens, the second step of preparing a refractive index matching oil matching the average refractive index and a relative refractive index oil having a different refractive index than the average refractive index, and up and down based on the plastic lens The first phase contrast image is obtained from a transmission type digital holography microscope by irradiating light of the first wavelength to the container of the third step and the third step of containing the refractive index matching oil and the relative refractive index oil in the upward direction, respectively. The light of the second wavelength in the container of the fourth step and the third step The fifth phase of obtaining the second phase contrast image from the transmission type digital holography microscope; A seventh phase obtained by subtracting the first phase contrast image, the second phase contrast image, and the third phase contrast image acquired in the sixth and fourth to sixth steps It can be achieved by a method for measuring the shape and refractive index of each part of the plastic lens characterized in that it comprises a step.

The shape and refractive index of the plastic lens having the curvature shape of the present invention can be used to measure the shape and refractive index of various parts relatively easily using a digital holography microscope.

1 is a flow chart illustrating a shape and a refractive index measuring method of a plastic lens having a shape as an embodiment according to the present invention.
2 is a block diagram of a digital holographic microscope for obtaining a phase contrast image in the present invention.
3 is a view showing an example of a container containing the average refractive index oil as an embodiment according to the present invention.
4 is a photograph showing a hologram of a plastic lens measured with a digital hologram microscope and a phase contrast image obtained therefrom.

Best Mode for Carrying Out the Invention Hereinafter, a preferred embodiment of a glass surface foreign matter inspection apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart illustrating a method of measuring a shape and a refractive index of a plastic lens having a shape according to an embodiment of the present invention. First, the average refractive index of the plastic lens is measured by using an ellipsometer (ST 100). Ellipsometer is a device for measuring the refractive index by analyzing the change in the polarization state of the elliptically polarized light that is reflected and output after the light having a specific polarization state to the plastic lens. An index of refraction is measured by using an ellipsometer on a part of the plastic lens to be measured, and the average refractive index is determined. In order to measure the refractive index of various parts of the plastic lens with the ellipsometer, it is very difficult to measure the refractive index of all parts of the plastic lens by measuring the refractive index of the contact surface after contacting the measuring part to be measured close to the prism side. .

Refractive Index Matching Oil having a measured average refractive index and a relative refractive oil having a refractive index slightly different from the average refractive flow are prepared and placed in a container having a predetermined shape (ST 200). Here, the refractive index of the relative refractive index oil slightly different from the average refractive index means a value determined according to the size of the lens or a difference between the average refractive index and the range of 0.001 to 1 for the phone lens. If the difference is less than 0.001, the phase contrast image is almost the same as the case of using the refractive index matching oil, and thus there is no effect. If the difference is larger than 1, the result is too inaccurate.

In order to measure the upper shape and the refractive index of the plastic lens, the refractive index matching oil is contained in the lower part of the container with the plastic lens therebetween, and the relative refractive index oil is contained in the upper part of the container (ST 300).

A phase contrast image is photographed using a transmission digital holography microscope to transmit the first laser light (for example, red laser light) from the bottom to the top in the container prepared in step ST 300 (ST 400).

In the same manner, a phase contrast image is photographed using a transmission-type digital holography microscope to transmit a second laser light (for example, Green laser light) from the bottom to the top of the container prepared in step ST 300 (ST 500).

Also, in the same manner, a phase contrast image is photographed using a transmission-type digital holography microscope to transmit a third laser light (for example, blue laser light) from the bottom to the top in the container prepared in step ST 300 (ST 600).

Three phase contrast images obtained in steps ST 400 to ST 600 are subtracted from each other to obtain three phase contrast images represented by Equation 3 to be described later (ST 700). From the three subtraction phase contrast images obtained in step ST 700, the shape and refractive index of each portion of the plastic lens may be calculated by using the calculation process shown in Equations 1 to 6 below.

2 is a block diagram of a digital holographic microscope for obtaining a phase contrast image in the present invention. Referring to FIG. 2, the digital holographic microscope measuring the average refractive index oil or the plastic lens in three dimensions includes a light source unit 100, a reference light generator 300 for generating reference light, an object light generator 200 for creating object light, And a CCD 400 that combines the reference light and the object light to record the hologram, and an operation unit 500 that subtracts the first phase contrast image, the second phase contrast image, and the third contrast image. Since the calculation unit 500 may obtain three phase contrast images that are subtracted from each other by subtracting three phase contrast images recorded on the CCD 400, the plastic lens may be processed through the calculation process shown in Equations 1 to 6 below. The shape and the refractive index difference can be confirmed for each site.

The light source unit 100 according to the present invention emits laser light. When the light source unit 100 is a laser beam, speckle noise is generated due to the high coherence of the laser beam. Therefore, preferably, the light source unit 100 of the digital holographic microscope for measuring defects of the display substrate according to the present invention in three dimensions further includes a rotation diffusion plate (not shown) for rotating and diffusing the laser light. It can be configured to diffuse through the rotary diffusion plate.

When the light source unit 100 is constituted by the laser beam passing through the rotary diffuser plate, the laser beam passes through the diffuser plate and the traveling angle is diffused irregularly. Since the diffusion plate rotates and the laser beam is transmitted and diffused at an irregular level, the phase of the laser beam changes irregularly, thereby eliminating interference, which is inherent to the laser beam. The coherence of the laser light causes speckle, which is a sparkling grainy noise on the screen, to deteriorate the picture quality. The speckle is removed.

The light source used in the experiment was a 10mW He-Ne laser, and a microscope objective lens (210: Mitutoyo M PLAN APO 50X, NA = 0.55) was used to enlarge the image transmitted through the sample. Filters 110 and 220 were used to obtain holograms with maximum contrast of interference patterns. The lenses 310 and 330 and the pinhole 320 were used to obtain reference light in the TEM00 mode, and the CCD 400 (KODAK Megaplus II) was used to store the hologram, and the pixel size of the CCD 400 was 7.4 μm × It is 7.4 mu m and the number of pixels is 2048 x 2048. In the off-axis experiment, the angle between the object light and the reference light was 1 °, and in the in-line experiment, the angle between the object light and the reference light was 0 °. Reference numerals 120 and 420 denote light splitters, and reference numeral 600 denotes an object to be measured (plastic lens).

The basic configuration of the digital holographic microscope according to the present invention is the same as the Mahzander interferometer, it is possible to grasp the shape and refractive index of the plastic lens itself from the three holograms recorded on the CCD 400 by the operation unit 500.

The principle of recognizing the refractive index from the phase contrast obtained from the transmission digital holography microscope will be briefly described. In the transmissive mode, the phase contrast phase is an optical path difference (OPL difference, optical length difference), which is a distance difference of light, is generated by a difference in refractive index of a medium where the light meets.

According to the Cauchy model of Equation 1, the refractive index is given as a function of wavelength.

Figure pat00001

Here, A and B are unknown constants, λ i represents the wavelength of the i-th light, and n (λ i) represents the refractive index at that wavelength.

Three phase contrast images obtained from the experiment (

Figure pat00002
) Is a function of the wavelength as shown in equation (2).

Figure pat00003

In Equation 2, λ denotes a wavelength of light, Nm denotes an average refractive index of the lens, and h denotes a height of a corresponding point of the plastic lens through which the laser light passes.

The phase contrast image for the three wavelengths is experimentally obtained as in Equation 2 with the flow shown in Fig. 1 using the apparatus of Fig. 2, and then Equations 3 and 4 are obtained.

Figure pat00004

Figure pat00005

Equation 5 is derived from equations (3) and (4).

Figure pat00006

here,

Figure pat00007
ego,
Figure pat00008
Therefore, A and B can be obtained as shown in Equation 6.

Figure pat00009

By substituting the obtained A and B values into Equation 1, the refractive index at the corresponding wavelength can be calculated, and the substituted refractive index in Equation 2 is used to know the height (shape) of the lens at the point where the corresponding wavelength is transmitted. It becomes possible.

3 is a diagram showing an example in which a plastic lens is contained in a container to obtain a phase contrast image for the top shape and the refractive index of the plastic lens. It is understood that the light transmits upward from the lower part of FIG. 3, and in order to grasp the upper shape and the refractive index of the plastic lens, as shown in FIG. 3, the refractive index matching oil is located below the plastic lens 30 in the container. The upper part contains the relative refractive oil. When placed in the air without using the relative refractive index oil contained in the upper part, since there are quite a lot of ring patterns in the phase contrast of the experimental result, using moderately different refractive index oils (2 to 3 ring patterns) This is to allow phase contrast to appear within the range where aliasing does not appear at the expense of.

If the shape and refractive index of the lower portion of the plastic lens is to be measured, the lens may be rotated 180 degrees in FIG. 3 so that the upper portion is contained in the refractive index matching oil positioned below.

While the preferred embodiments of the present invention have been described and illustrated above using specific terms, such terms are used only for the purpose of clarifying the invention, and the embodiments of the present invention may be embodied in various forms without departing from the spirit or scope of the following claims It is evident that various changes and changes may be made.

10: refractive index matching oil 20: relative refractive index oil
30: plastic lens
100: light source unit 110, 220: filter
200: reference light generator 210: objective lens
120 and 420: light splitter 300: object light generator
310, 330: Lens 400: CCD
500: calculator 600: target object to be measured

Claims (3)

A method of measuring the shape and refractive index of each part of a plastic lens including a phone lens or a contact lens used in a mobile phone,
A first step of measuring a refractive index of one location of the plastic lens;
Defining a refractive index measured in the first step as an average refractive index of the plastic lens, and preparing a refractive index matching oil matching the average refractive index and a relative refractive oil having a refractive index different from the average refractive index;
A third step of placing the refractive index matching oil and the relative refractive oil in a container, respectively, on the basis of the plastic lens;
A fourth step of obtaining a first phase contrast image from a transmission type digital holography microscope by irradiating the container of the third step from the bottom to the top with light having a first wavelength;
A fifth step of obtaining a second phase contrast image from a transmission type digital holography microscope by irradiating the vessel of the third step with light of a second wavelength in a downward direction;
A sixth step of obtaining a third phase contrast image from the transmission type digital holography microscope by irradiating the container of the third step with light of a third wavelength from the top to the bottom; And
And a seventh step of obtaining the subtracted three phase contrast images by mutually subtracting the first phase contrast image, the second phase contrast image, and the third phase contrast image obtained in the fourth to sixth steps. Method for measuring the shape and refractive index of each part of the plastic lens characterized in that.
The method of claim 1,
The refractive index difference between the refractive index matching oil and the relative refractive oil is a value between 0.001 to 1, wherein the shape and refractive index of each part of the plastic lens.
3. The method according to claim 1 or 2,
And further comprising an eighth step of calculating a refractive index of the plastic lens by applying a Cosi model to the three phase contrasts obtained after the seventh step. .
KR1020120003677A 2012-01-12 2012-01-12 Refractive index measuring method for plastic lens with curvature KR20130083117A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101528132B1 (en) * 2014-11-13 2015-06-12 윤철주 The method for measuring the power of glass lens by personal mobile device
KR20160071298A (en) * 2014-12-11 2016-06-21 주식회사 케이피에스 Curvature of both sides surface and refractive index profile simultaneous measurement method of the lens

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101528132B1 (en) * 2014-11-13 2015-06-12 윤철주 The method for measuring the power of glass lens by personal mobile device
WO2016076530A1 (en) * 2014-11-13 2016-05-19 윤철주 System for measuring power of eyeglass lens using mobile device, method therefore, and program therefor
KR20160071298A (en) * 2014-12-11 2016-06-21 주식회사 케이피에스 Curvature of both sides surface and refractive index profile simultaneous measurement method of the lens

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