WO2017052244A1

WO2017052244A1 - Refractive index distribution measuring system and refractive index distribution measuring method using same

Info

Publication number: WO2017052244A1
Application number: PCT/KR2016/010607
Authority: WO
Inventors: 서광범
Original assignee: 주식회사 힉스컴퍼니
Priority date: 2015-09-25
Filing date: 2016-09-23
Publication date: 2017-03-30

Abstract

According to an embodiment of the present invention, there is provided a refractive index distribution measuring system comprising: a light source for emitting light; a support member arranged on a path of light emitted from the light source so as to support a measurement object such that the measurement object is arranged, about an optical axis, only on one side of the optical axis; an optical member arranged on a path of light, which has passed through the support member, such that the light is reflected at the front and rear surfaces thereof, the optical member having a predetermined thickness; a light-receiving unit for receiving two rays of light, which are reflected at the front and rear surfaces of the optical members, respectively, and parts of which then overlap and form an interference pattern; and a signal processing unit for deriving the refractive index distribution of the measurement object from the interference pattern acquired by the light-receiving unit.

Description

Refractive index distribution measuring system and refractive index distribution measuring method using the same

The present invention relates to a refractive index distribution measurement system and a refractive index distribution measurement method using the same, and more particularly, to a refractive index distribution measurement system which can precisely measure a refractive index distribution of a measurement object using a deformed shear interferometer. And a method of measuring a refractive index distribution.

As the demand for miniaturization and high integration of IT devices increases, the sizes of optical elements such as optical lenses included in IT devices also become smaller than microns. When an error occurs in the refractive index distribution of these optical elements, The performance of the product may be deteriorated. Accordingly, there is an increasing demand for a technique for precisely measuring the refractive index distribution error by comparing the refractive index distribution of the optical elements and the designed refractive index distribution.

On the other hand, digital holography microscopy is a technique for quantitatively measuring thickness information of a measurement object using hologram phase information formed by interference of highly coherent light sources.

Generally, a digital holography microscope forms a hologram pattern using an optical interferometer. Michelson interferometer and Mach-Zender interferometer, which are widely used in digital holography microscopes among optical interferometers. These interferometers convert light emitted from a light source into an object light source and a reference light source using a light separator. And the two light sources are overlapped to form an interference pattern. However, in the interference pattern obtained by these interferometers, DC bias and virtual image information are included in addition to real-world information to be measured, and there is a problem that the interferometer has a complicated structure and is vulnerable to vibration.

Therefore, it is possible to measure the refractive index distribution error of the optical element by using a lateral shearing interferometer, which has a simple configuration and two optical paths that cause interference, and which generates less errors due to vibration. However, in the case of the front end interferometer, since an interference pattern is obtained by using two object light sources passing through the object to be measured, there is a problem that the interference pattern includes information about the object in duplicate.

The present invention is a refractive index distribution measuring system capable of precisely measuring the refractive index distribution error by obtaining an interference pattern without duplicate images, comparing the refractive index distribution of the object to be measured with the designed refractive index distribution, and And a method of measuring a refractive index distribution.

According to an embodiment of the present invention, there is provided a light source device comprising: a light source that emits light; a support member that is disposed on a path of light emitted from the light source and supports the measurement target object such that the measurement target object is disposed on only one side of the optical axis, An optical member which is disposed on a path of light transmitted through the support member and reflects the light on the front surface and the rear surface respectively and has a predetermined thickness; And a signal processing unit for deriving a refractive index distribution of the measurement object from the interference pattern acquired by the light receiving unit.

According to another embodiment of the present invention, there is provided a light source device comprising a light source, a support member for supporting the measurement target object so that the measurement object is disposed only on one side of the optical axis, an optical member for reflecting light from the front and rear surfaces, A method of measuring a refractive index distribution using an interferometer including a light receiving unit for receiving light, comprising the steps of: obtaining a hologram image from an interference pattern acquired by the light receiving unit; removing noise from the hologram image; Extracting phase information of the measurement object, and measuring a refractive index distribution of the measurement object using the phase information.

According to an embodiment of the present invention, as described above, a refractive index distribution measuring system capable of obtaining an interference pattern without duplicate images and accurately measuring the refractive index distribution error of the object to be measured, and A refractive index distribution measuring method can be provided.

1 is a schematic view showing a refractive index distribution measuring system according to an embodiment of the present invention.

2 is a conceptual diagram showing a region B in Fig.

FIG. 3 is a graph showing the distance of light reflected from the front and back surfaces of the optical member according to the incident angle of light incident on the optical member included in FIG. 1;

4 is a block diagram showing the detailed configuration of the signal processing unit of FIG.

5 is a graph showing the refractive index distribution error according to the width of the measurement object.

An objective lens disposed between the support member and the optical member for magnifying light transmitted through the measurement object, and an adjustment lens for converting the light expanded by the objective lens into parallel light.

A first polarizer disposed between the light source and the support member, and a second polarizer disposed between the optical member and the light receiving unit, wherein a polarization axis direction of the first polarizer and a polarization axis direction of the second polarizer are mutually identical can do.

The predetermined thickness of the optical member may be 5 mm to 15 mm.

Wherein the light reflected by the front surface of the optical member includes a first object region transmitted through the measurement object and a first reference region that is a region other than the first object region, And a second reference area that is a region other than the second object area, the interference pattern being formed by overlapping the first object area and the second reference area, 1 reference area and the second object area, and the first object area and the second object area may not overlap with each other.

And a refractive index matching oil disposed on the support member, wherein the measurement object can be disposed in the refractive index matching oil.

Wherein the signal processing unit includes: a hologram image acquiring unit that acquires an object hologram image from the interference pattern acquired by the light receiving unit in a state where the measurement object is disposed on the support member; a noise removing unit that removes noise from the object hologram image; A phase information extracting unit for extracting phase information of the measurement object, and a refractive index distribution measuring unit for calculating a refractive index distribution of the measurement object using the phase information.

And a refractive index error measuring unit for calculating a refractive index distribution error by comparing the refractive index distribution of the measurement object with the designed refractive index distribution of the measurement object.

Wherein the hologram image obtaining unit obtains a reference hologram image from the interference pattern acquired by the light receiving unit in a state in which the measurement object is not disposed on the object hologram image and the support member, Wherein the phase information extracting unit extracts a phase of the reference hologram image from the reference hologram image based on the difference between the object phase information obtained from the object hologram image from which the noise is removed and the reference phase information obtained from the noise- The phase information can be extracted.

The method may further include the step of calculating a refractive index distribution error by comparing the refractive index profile of the measured object with the refractive index profile of the measured object after the measurement of the refractive index profile.

The obtaining of the hologram image may include acquiring an object hologram image in a state where the measurement object is disposed on the support member, and acquiring a reference hologram image in a state where the measurement object is not disposed on the support member Wherein the removing the noise includes removing noise from the object hologram image and the reference hologram image, and the step of extracting the phase information of the measurement object includes the step of extracting the object hologram image And extracting the phase information of the measurement object from the difference between the object phase information obtained from the reference hologram image and the reference phase information obtained from the reference hologram image from which noise has been removed.

The thickness of the optical member may be 5 mm to 15 mm.

Wherein the light reflected by the front surface of the optical member includes a first object region transmitted through the measurement object and a first reference region that is a region other than the first object region, And a second reference area that is an area other than the second object area, wherein before the step of acquiring the hologram image, a part of the light reflected from the front surface and the back surface of the optical member, respectively, And aligning the light source and / or the optical member so that the first object zone and the second object zone do not overlap with each other in the overlapping zone.

The step of aligning the light source and / or the optical member may include aligning the light source and / or the optical member such that light is incident on the optical member at 10 to 80 degrees.

Other aspects, features, and advantages other than those described above will be apparent from the following detailed description, claims, and drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following drawings, like reference numerals refer to like elements, and the size of each element in the drawings may be exaggerated for clarity and convenience of explanation.

FIG. 1 is a schematic view showing a refractive index distribution measuring system according to an embodiment of the present invention. FIG. 2 is a conceptual view showing a region B in FIG. 1, FIG. 5 is a graph illustrating a distance between light reflected by the front surface and the rear surface of the optical member according to the incident angle of light.

1, a refractive index distribution measuring system according to an embodiment of the present invention includes a light source 100 for emitting light, a light source 100 disposed on a path of light emitted from the light source 100 and having an optical axis OA about an optical axis OA, A support member 200 for supporting the measurement object 210 so that the measurement object 210 is disposed only on one side of the support member 200 and a support member 200 for supporting the measurement object 210 on the front surface 300a and the rear surface 300b, An optical member 300 which reflects light and has a predetermined thickness t, two light beams which are reflected from the front face 300a and the rear face 300b of the optical member 300 and partially overlap each other to form an interference pattern B1 and B2 and a signal processing unit 510 for deriving a refractive index distribution of the measurement object 210 from the interference pattern acquired by the light receiving unit 400. [

The light source 100 may be a laser light source and may be, for example, a continuous He-Ne laser having a wavelength of about 632.8 nm. The light emitted from the light source 100 may be reflected by the reflective member 810 and then incident on the support member 200 supporting the measurement object 210. A collimator 820 composed of a lens or the like for converting the light emitted from the light source 100 into parallel light may be further disposed between the light source 100 and the reflective member 810. The light source 100, (820) may be formed integrally.

A first polarizer 830 may be further disposed between the collimator 820 and the reflective member 810. The first polarizer 830 may transmit only the polarized light in a predetermined direction, 400 can be minimized by interfering with the second polarizer 860 disposed in front of the light receiving unit 400. [ The direction of the polarization axis of the first polarizer 830 and the direction of the polarization axis of the second polarizer 860 may be identical to each other and the optical element 830 disposed between the first polarizer 830 and the second polarizer 860 It is possible to remove unintended light components such as scattered light that may be generated by the light sources. When the scattering occurs, the polarization direction may be changed, so that at least a part of the scattered light or the like can not pass through the second polarizer 860. That is, at least a part of the scattered light or the like, which may cause noise, can not be incident on the light receiving unit 400.

1, a collimator 820, a first polarizer 830, and a reflection member 810 are disposed between the light source 100 and the support member 200. However, the present invention is not limited thereto, May be omitted as needed.

The support member 200 is arranged on the path of the light reflected by the reflection member 810 and the support member 200 is measured so that the measurement object 210 is disposed on only one side of the optical axis OA with respect to the optical axis OA The object 210 can be supported. A reference numeral A in FIG. 1 shows the measurement object 210 disposed on the support member 200 in a direction in which the light travels. The beam spot includes a center line CL passing the optical axis OA The measurement object 210 is disposed within the beam spot BSP and the measurement target object 210 can be disposed on the support member 200 so as to be located at only one side with respect to the center line CL of the beam spot BSP.

According to one embodiment, the measurement object 210 may be disposed within an index matching oil 220. The refractive index of the refractive index matching oil 220 is the same as or similar to the refractive index of the measuring object 210 and is arranged such that the measuring object 210 is completely immersed in the refractive index matching oil 220, It is possible to prevent scattering or refraction at the interface between the measurement object 210 and the air. One side of the refractive index matching oil 220 can be in contact with the objective lens 840 and the numerical aperture NA of the objective lens 840 can be increased through this configuration.

An objective lens 840 and an objective lens 840 having a predetermined magnification are disposed between the support member 200 and the optical member 300. The objective lens 840 and the objective lens 840 are disposed between the support member 200 and the optical member 300, An adjustment lens 850 for converting the light expanded by the light source 810 into parallel light can be disposed. The light incident on the optical member 300 becomes the light transmitted through the support member 200 and the refractive index matching oil 220 when the measurement object 210 is not disposed on the support member 200, The measurement object 210 and the refractive index matching oil 200 when the measurement object 210 is disposed on the support member 200,

The size of the two light beams B1 and B2 incident on the light receiving unit 400 forming an interference pattern may be determined by the objective lens 840. For example, The radius may be about 5 mm. The size of the light B1 and B2 may be determined in consideration of the contrast of the interference pattern obtained by the light receiving unit 400 and the size of the light B1 and B2 may be determined based on the intensity of the light, Can be defined on the basis of a point at which 1 / e decreases.

The optical member 300 may be an optical glass having a predetermined thickness t and a refractive index n ₂ and the light incident on the optical member 300 may be incident on the front surface 300a and the rear surface And 300b, respectively. The first beam B1 reflected from the front surface 300a of the optical member 300 and the second beam B2 reflected from the rear surface 300b are spaced apart from each other by a predetermined distance d, . The distance d means the distance between the center of the first beam B1 and the center of the second beam B2, i.e., the distance between the two optical axes divided by the optical member 300. [

2 shows the first beam B1 and the second beam B2 reflected from the front surface 300a and the rear surface 300b of the optical member 300 in a direction in which light travels, reference to Figure 2 when, the first beam (B1) is a measurement target object 210, the first object region (O ₁₎ and the first object region (O _1), the area other than the first reference area (R ₁₎ transmitted through the included and the second beam (B2) may include a light transmitted through the measurement target object 210, the second object region (O ₂₎ and the second object region (O ₂₎ regions of the second reference region other than the (R ₂₎ have.

As described above, the measurement target object 210 is placed only on one side of the optical axis (OA), the first object region (O ₁₎ and a second object area (O ₂₎ are all only one side relative to the center line of the beam . Therefore, when the degree of overlapping of the first beam B1 and the second beam B2 is adjusted by adjusting the distance d between the first beam B1 and the second beam B2, O ₁ and the second reference region R ₂ may overlap with each other and the interference pattern formed by overlapping the first object region O ₁ and the second reference region R ₂ may be incident on the light receiving section 400 have.

The first object region (O ₁₎ and a second object area (O ₂₎ is a region respectively transmitted through the measurement target object 210, the first object region (O ₁₎ and a second object area (O ₂₎ are superposed When the interference pattern is formed, the interference pattern includes the phase information for the measurement object 210 in a double manner. When the interference pattern includes duplicate images, a large error may occur in the phase information of the measurement object 210 extracted through the interference pattern and the refractive index distribution derived therefrom.

However, according to an embodiment of the present invention, the first object zone O ₁ and the second object zone O ₂ do not overlap with each other, and the first object zone O ₁ corresponds to the second reference zone R ₂ , To form an interference pattern. However, the present invention is not limited to this, and the second object zone O ₂ may overlap the first reference zone R ₁ depending on the position of the measurement object 210 disposed on the support member 200 . In any case, the first object zone O ₁ and the second object zone O ₂ do not overlap each other, and thus the interference pattern obtained by the interferometer of FIG. 1 does not include a dual image. However, the first object region (O ₁₎ overall are to be included in the first beam (B1) and the the second beam (B2) are superposed overlapping area (OR). When a part of the first object zone O ₁ is not included in the overlap area OR, it is not possible to measure the refractive index distribution of the measurement target object 210 corresponding to the area not including the first object zone O ₁ .

The first object zone O ₁ and the second object zone O ₂ do not overlap with each other so that the entire first object zone O ₁ is included in the overlap area OR, The separation distance d between the first beam B1 and the second beam B2 should be determined and the separation distance d may be determined by the following equation 1:

[Equation 1]

Here, t denotes the thickness of the optical member 300, n ₂ denotes the refractive index of the optical member 300, n ₁ denotes the air refractive index, and θ _i denotes the incident angle of the light incident on the optical member 300.

3 is a graph showing the distance d of light reflected from the front face 300a and the rear face 300b of the optical member 300 according to the incident angle? _{I of} the light incident on the optical member 300, , And the separation distance d is represented by a variable including the thickness t of the optical member 300 and n ₁ / n ₂ is calculated to be about 0.658, which is the ratio of the optical glass to the refractive index of air.

The horizontal axis in FIG. 3 represents the incident angle (? _I ) in radian units, and the angle in degree units can be calculated by multiplying the radian by 180 / 3.14.

As shown in FIG. 3, when the incident angle is 49.29 degrees, the separation distance d has a maximum value, and the separation distance d from the angle may have a value of 0.75 x tm. According to this, when the thickness t of the optical member 300 is less than about 5 mm, the maximum value of the separation distance is less than 3.5 mm. However, in this case, since the area of the overlap region OR between the first beam B1 and the second beam B2 becomes excessively large, the center line can be located in the overlap region OR. Therefore, the first object zone O ₁ of the first beam B1 overlaps the second object zone O ₂ of the second beam B2, and the interference pattern may include a double image. If the thickness t of the optical member 300 exceeds about 15 mm, even if the incident angle? _I is adjusted, the spacing distance d becomes excessively large, and the area of the overlapping area OR is excessively small, At least a part of the first object zone O ₁ of the first beam B1 may be arranged outside the overlap area OR in the area OR. That is, in this case, it is not possible to measure the refractive index distribution for a partial region of the measurement target 210. Therefore, the thickness t of the optical member 300 may have a value of 5 mm to 15 mm.

The separation distance (d) as well as thickness (t) of the optical member 300 may be varied according to the incident angle (θ _i) impinging on the optical element 300, the angle of incidence (θ _i) is 10 to 80 degrees It can have an angle. When the incident angle? _I is less than 10 degrees, the path of the light traveling between the front surface 300a and the rear surface 300b of the optical member 300 is excessively long, so that the optical member 300 having a relatively large size is required, The distance may be long so that the interference between the light reflected from the front surface 300a and the light reflected from the rear surface 300b may not occur well. When the incident angle? _I exceeds 80 degrees, the path of the light incident on the optical member 300 and the path of the light reflected from the optical member 300 may be too close to align the optical elements.

The refractive index distribution measuring system according to an embodiment of the present invention includes two beams B1 and B2 which are partially reflected on the front surface 300a and the rear surface 300b of the optical member 300 and form an interference pattern, A light receiving unit 400 for receiving light and a central processing unit 500. The central processing unit 500 includes a signal processing unit 510 for deriving a refractive index distribution of the measurement object 210 from the interference pattern acquired by the light receiving unit 400 and a signal processing unit And a control unit 520 for adjusting the position of the display unit 850. Although not shown, the control unit 520 may be connected to the light source 100 and the optical member 300 to sense the intensity of the light source 100. The light source 100 may be a two-dimensional solid image sensor such as a charge coupled device (CCD) And the angle of the optical member 300 may be adjusted.

4 is a block diagram showing the detailed configuration of the signal processing unit of FIG. Hereinafter, a detailed configuration of the signal processing unit 400 included in the refractive index distribution measuring system and a method of measuring a refractive index distribution therefrom will be sequentially described with reference to FIG.

4, the signal processing unit 510 includes a hologram image acquiring unit 500 for acquiring an object hologram image from the interference pattern acquired by the light receiving unit 400 while the measurement object 210 is disposed on the support member 200, A phase information extracting unit 513 for extracting phase information of the measurement object 210 and a phase information extracting unit 513 for extracting the refractive index of the measurement object 210 using the phase information, And a refractive index distribution measuring unit 514 for calculating a distribution.

The signal processing unit 510 measures the refractive index distribution of the measurement object 210 from the interference pattern acquired through the interferometer including the light source 100, the support member 200, the optical member 300 and the light receiving unit 400 The method of measuring a refractive index profile according to an embodiment of the present invention includes the steps of obtaining a hologram image from an interference pattern acquired by a light receiving unit 400, removing noise from the hologram image, measuring the hologram image from the hologram image Extracting phase information of the object 210, and calculating a refractive index distribution of the measurement object 210 using the phase information. The step of acquiring the hologram image may include a step of removing the noise in the hologram image acquiring unit 511, a step of extracting the phase information from the noise removing unit 512, and a step of extracting the phase information from the phase information extracting unit 513, The calculating step may be performed in the refractive index distribution measuring unit 514. [

According to an embodiment of the present invention, the refractive index distribution measuring method further includes a step of calculating a refractive index distribution error by comparing the refractive index profile of the measured object 210 with the refractive index profile of the measured object 210 after the step of calculating the refractive index profile And this can be performed in the refractive index distribution error measuring unit 515 of the signal processing unit 510. The refractive index distribution error of the measurement object 210 can be precisely measured. For example, the measurement object 210 may be a high-performance microlens. The microlens is manufactured by a method of mass-injection of a plastic lens in consideration of manufacturing cost, robustness against impact, etc. When a microlens is manufactured by an optical lens manufacturing method through a plastic lens injection process, The refraction index of the microlens manufactured by the difference of the cooling speed and the pressure can be changed according to the position. As a result, when a portable multimedia terminal or the like includes a microlens as described above, it may be difficult to obtain a high-resolution image. Therefore, there is an increasing demand for a technique for measuring the refractive index distribution error by comparing the refractive index distribution of the manufactured microlens with the designed refractive index distribution. INDUSTRIAL APPLICABILITY The present invention can provide a refractive index distribution measuring system and a refractive index distribution measuring method which can precisely measure the refractive index distribution and the refractive index distribution error.

The step of acquiring the hologram image may include acquiring an object hologram image in a state where the measurement object 210 is disposed on the support member 200 and acquiring the hologram image in a state where the measurement object 210 is not disposed on the support member 200 Wherein the step of removing noise includes a step of removing noise from an object hologram image and a reference hologram image, and the step of extracting the phase information of the measurement object 210 includes the steps of: And extracting the phase information of the measurement object from the difference between the object phase information obtained from the object hologram image from which the noise has been removed and the reference phase information obtained from the noise-removed reference hologram image.

The intensity of the object hologram image acquired by the hologram image acquisition unit 511 is expressed by Equation 2 below.

&Quot; (2) "

Here, O ₁ denotes an electric field of light corresponding to the first object zone O ₁ described in FIG. 2, R ₂ denotes an electric field of light corresponding to the second reference area R ₂ , and Equation 2 It can be confirmed that the intensity of the object hologram image does not include information on the light corresponding to the second object zone O ₂ , that is, a dual image.

The noise removing unit 512 may remove noise such as a DC bias and a virtual image from the hologram intensity of the object hologram image. Various methods for eliminating such noise have been proposed. Hereinafter, a noise control method using a low pass filtering (LPF) method and an angular spectrum (ASP) method will be described below.

In order to numerically recover the complex amplitude included in Equation ( ₂ ), light corresponding to the second reference region (R ₂ ) is further irradiated to the interference pattern, thereby obtaining a plurality of amplitudes as shown in Equation (3) have.

&Quot; (3) "

Low frequency pilling was performed to remove the DC bias and the virtual image from the obtained complex amplitude, and phase information for the measurement object 210 was extracted from the reconstruction plane using each spectral method. Equation (4) is a complex amplitude in which low frequency filtering and each spectral method are applied in the frequency domain after a fourier transform.

&Quot; (4) "

here,

Is a plurality of amplitudes from which the DC bias and the virtual image are removed by low frequency filtering, and the exponent part means the application of each spectral method. In addition, f _x and f _y are spatial frequencies in the x and y axis directions, and k, λ and d denote the wave number, wavelength, and restoration distance, respectively.

Finally, a complex amplitude for extracting the phase information for the measurement object 210 can be obtained as shown in Equation (5) by using an inverse fourier transform to convert the complex amplitude in the frequency domain into the spatial domain have.

&Quot; (5) "

Generally, the difference in light path is determined by the difference between the thickness of the measurement object 210 and the refractive index. In addition, the difference in the light path can be expressed by the wavelength of the light source and the phase information of the measurement object 210. According to one embodiment, the information on the refractive index of the measurement object 210 can be expressed by Equation (6).

&Quot; (6) "

Here,? X (x, y, d) and? L (x, y, d) mean the phase difference by the measurement target 210 and the thickness of the measurement target 210.

According to one embodiment, the measurement object 210 is disposed in the refractive index matching oil 220 having the same or similar refractive index as that of the measurement object 210, and the phase of the measurement object 210 when the measurement object 210 is disposed on the support member 200 Can be expressed by the following Equation (7), and the phase when the measurement object 210 is not disposed on the support member (200) can be expressed by the following Equation (8).

&Quot; (7) "

&Quot; (8) "

Where D is the distance along the direction in which the light of the refractive index matching oil 220 advances and? L is the distance along the direction in which the light of the measurement object 210 travels.

From Equation (7) and Equation (8), the phase information of the measurement object 210 can be extracted as shown in Equation (9).

&Quot; (9) "

Here, n _lens means a refractive index of the measurement object 210, and n _oil means a refractive index of the refractive index matching oil 220.

If the refractive index of the refractive index matching oil 220 is the same as the refractive index of the measurement object 210,? Is 0, and if the refractive index difference is constant, ?? has a constant value. That is, when the refractive index (n _lens ) of the measurement object 210 is constant according to the position, only a regular interference pattern in the form of a line is formed over the entire overlap region OR.

However, when an error occurs between the refractive index of the measurement target 210 and the refractive index of the actual measurement target 210 depending on the position of the measurement target 210, An irregularly shaped interference pattern can be formed. The refractive index of the measurement object 210 including the error can be expressed by the following equation (10).

&Quot; (10) "

Here, n is the refractive index _designed, σ _lens design of the measurement target object 210 means a refractive error.

From Equations (9) and (10), it is possible to derive an equation relating to the refractive index distribution error as shown in Equation (11).

&Quot; (11) "

In the above formula, n _designed, n _oil and? L is a known value,? Φ is the value obtained from the interference pattern, it is possible to derive the refractive index profile errors by the equation (11). Although the present invention has been described in the case where noise is reduced by minimizing refraction and scattering of light by arranging the measurement object 210 in the refractive index matching oil 220, the present invention is not limited to this, Without the refractive index matching oil 220 on the lens 200. In this case, n _oil can be replaced by the air refractive index value.

Referring to FIG. 5, it can be seen that the refractive index distribution error according to the width of the measurement object 210 is measured with an accuracy of nanometer or less.

That is, according to the refractive index distribution measuring system and the refractive index distribution measuring method according to an embodiment of the present invention, an interference pattern without duplicate images is obtained, and the refractive index distribution error of the measurement object 210 is precisely And a refractive index distribution error measuring method using the refractive index distribution error measuring system.

An apparatus according to the present invention may include a processor, a memory for storing and executing program data, a permanent storage such as a disk drive, a communication port for communicating with an external device, a user interface such as a touch panel, a key, Devices, and the like. Methods implemented with software modules or algorithms may be stored on a computer readable recording medium as computer readable codes or program instructions executable on the processor. Here, the computer-readable recording medium may be a magnetic storage medium such as a read only memory (ROM), a random access memory (RAM), a floppy disk, a hard disk and the like) and an optical reading medium (e.g., a CD ROM, (DVD: Digital Versatile Disc)). The computer-readable recording medium may be distributed over networked computer systems so that computer readable code in a distributed manner can be stored and executed. The medium is readable by a computer, stored in the memory, and executable on the processor.

All documents, including publications, patent applications, patents, etc., cited in the present invention may be incorporated into the present invention in the same manner as each cited document is shown individually and specifically in conjunction with one another, .

In order to facilitate understanding of the present invention, reference will be made to the preferred embodiments shown in the drawings, and specific terminology is used to describe the embodiments. However, the present invention is not limited to the specific terminology, Lt; / RTI > may include all elements commonly conceivable by those skilled in the art.

The present invention may be represented by functional block configurations and various processing steps. These functional blocks may be implemented in a wide variety of hardware and / or software configurations that perform particular functions. For example, the present invention employs integrated circuit configurations, such as memory, processing, logic, look-up tables, etc., that can perform various functions by control of one or more microprocessors or by other control devices can do. Similar to the components of the present invention may be implemented with software programming or software components, the present invention may be implemented in a variety of ways, including C, C ++, And can be implemented in a programming or scripting language such as Java, assembler, and the like. Functional aspects may be implemented with algorithms running on one or more processors. The present invention may also employ conventional techniques for electronic configuration, signal processing, and / or data processing. Terms such as "mechanism", "element", "means", "configuration" may be used broadly and are not limited to mechanical and physical configurations. The term may include the meaning of a series of routines of software in conjunction with a processor or the like.

The specific acts described in the present invention are, by way of example, not intended to limit the scope of the invention in any way. For brevity of description, descriptions of conventional electronic configurations, control systems, software, and other functional aspects of such systems may be omitted. Also, the connections or connecting members of the lines between the components shown in the figures are illustrative of functional connections and / or physical or circuit connections, which may be replaced or additionally provided by a variety of functional connections, physical Connection, or circuit connections. Also, unless explicitly mentioned, such as " essential ", " importantly ", etc., it may not be a necessary component for application of the present invention.

The use of the terms " above " and similar indication words in the specification of the present invention (particularly in the claims) may refer to both singular and plural. In addition, in the present invention, when a range is described, it includes the invention to which the individual values belonging to the above range are applied (unless there is contradiction thereto), and each individual value constituting the above range is described in the detailed description of the invention The same. Finally, the steps may be performed in any suitable order, unless explicitly stated or contrary to the description of the steps constituting the method according to the invention. The present invention is not necessarily limited to the description line of the above steps. The use of all examples or exemplary language (e.g., etc.) in this invention is for the purpose of describing the present invention only in detail and is not to be limited by the scope of the claims, It is not. It will also be appreciated by those skilled in the art that various modifications, combinations, and alterations may be made depending on design criteria and factors within the scope of the appended claims or equivalents thereof.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

At least one of the embodiments of the present invention can be used in a refractive index distribution error measuring system and a refractive index distribution error measuring method using the same.

Claims

A light source for emitting light;

A support member disposed on a path of light emitted from the light source and supporting the measurement object so that the measurement object is disposed only on one side of the optical axis with respect to the optical axis;

An optical member disposed on a path of light transmitted through the support member and reflecting the light on the front surface and the rear surface, respectively, the optical member having a predetermined thickness;

A light receiving unit for receiving two lights, which are partially overlapped after being reflected from the front surface and the rear surface of the optical member to form an interference pattern; And

And a signal processing unit for deriving a refractive index distribution of the measurement object from the interference pattern acquired by the light receiving unit.
The method according to claim 1,

Further comprising an objective lens disposed between the support member and the optical member for magnifying light transmitted through the measurement object and an adjustment lens for converting the light expanded by the objective lens into parallel light, .
The method according to claim 1,

A first polarizer disposed between the light source and the supporting member, and a second polarizer disposed between the optical member and the light receiving unit,

Wherein the polarization axis direction of the first polarizer is the same as the polarization axis direction of the second polarizer.
The method according to claim 1,

Wherein the predetermined thickness of the optical member is 5 mm to 15 mm.
The method according to claim 1,

Wherein the light reflected from the front surface of the optical member includes a first object zone which has passed through the measurement object and a first reference zone which is an area other than the first object zone,

The light reflected from the back surface of the optical member includes a second object region that has passed through the measurement object and a second reference region that is a region other than the second object region,

Wherein the interference pattern is formed by overlapping the first object region and the second reference region or by overlapping the first reference region and the second object region, and the interference pattern is formed by overlapping the first object region and the second reference region, Wherein the regions do not overlap with each other.
The method according to claim 1,

Further comprising a refractive index matching oil disposed on the support member, wherein the measurement object is disposed within the refractive index matching oil.
The method according to claim 1,

The signal processing unit,

A hologram image acquiring unit for acquiring an object hologram image from the interference pattern acquired by the light receiving unit in a state where the measurement object is disposed on the support member;

A noise removing unit for removing noise from the object hologram image;

A phase information extracting unit for extracting phase information of the measurement object; And

And a refractive index distribution measuring unit for calculating a refractive index distribution of the measurement target using the phase information.
8. The method of claim 7,

Further comprising a refractive index error measuring unit for calculating a refractive index distribution error by comparing the refractive index profile of the measurement subject with the designed refractive index profile of the measurement subject.
8. The method of claim 7,

Wherein the hologram image obtaining unit obtains the reference hologram image from the interference pattern acquired by the light receiving unit in a state in which the measurement object is not disposed on the object hologram image and the support member,

Wherein the noise removing unit removes noise from the object hologram image and the reference hologram image,

Wherein the phase information extraction unit extracts phase information of the measurement object from a difference between object phase information obtained from the object hologram image from which the noise has been removed and reference phase information obtained from the reference hologram image from which noises have been removed, .
An interferometer including a light source, a support member for supporting the measurement object so that the measurement object is disposed only on one side of the optical axis, an optical member for reflecting light from the front and back surfaces, and a light receiving section for receiving the light reflected by the optical member In the refractive index distribution measuring method,

Acquiring a hologram image from the interference pattern acquired by the light receiving unit;

Removing noise from the hologram image;

Extracting phase information of the measurement object from the noise-removed hologram image; And

And measuring a refractive index distribution of the measurement object using the phase information.
11. The method of claim 10,

After measuring the refractive index distribution,

Further comprising the step of calculating a refractive index distribution error by comparing the refractive index profile of the measurement subject with the designed refractive index profile of the measurement subject.
11. The method of claim 10,

The obtaining of the hologram image may include obtaining an object hologram image in a state where the measurement object is disposed on the support member, and acquiring a reference hologram image in a state where the measurement object is not disposed on the support member Including,

Wherein the removing the noise includes removing noise from the object hologram image and the reference hologram image,

The step of extracting the phase information of the measurement object extracts the phase information of the measurement object from the difference between the object phase information obtained from the object hologram image from which the noise has been removed and the reference phase information obtained from the reference hologram image from which noise has been removed Wherein the refractive index distribution measurement method comprises the steps of:
11. The method of claim 10,

Wherein the thickness of the optical member is 5 mm to 15 mm.
11. The method of claim 10,

Wherein the light reflected from the front surface of the optical member includes a first object zone which has passed through the measurement object and a first reference zone which is an area other than the first object zone,

The light reflected from the back surface of the optical member includes a second object region that has passed through the measurement object and a second reference region that is a region other than the second object region,

Before the step of acquiring the hologram image,

Wherein the light reflected from the front surface and the rear surface of the optical member are at least partially overlapped with each other, and the light source and / or the optical member are aligned so that the first object area and the second object area do not overlap each other in the overlap area &Lt; / RTI > further comprising the steps of:
15. The method of claim 14,

Wherein aligning the light source and / or the optical member comprises aligning the light source and / or the optical member such that light is incident on the optical member at 10 to 80 degrees.