KR101462890B1 - Method for measuring shape of lenticular lens in Fresnel lens type - Google Patents

Abstract

The present invention relates to a method for measuring a shape of a lenticular lens having a shape of a fresnel lens and provided with a central curved surface portion through which an optical axis and an aligned central axis pass, multiple curved surface portions that are arranged to be symmetrical with respect to the central axis on both sides of the central curved surface portion, and multiple inclined surface portions that connect end portions of the adjacent curved surface portions. The present invention includes a phase measurement step, a first graph calculation step, a second graph calculation step, a reference thickness calculation step, and a position determination step. In the phase measurement step, a phase of the central curved surface portion and a phase of the curved surface portion are measured. In the first graph calculation step, a phase graph of the central curved surface portion and a phase graph of the curved surface portion are arranged apart from each other in a left-right direction and a part between the phase graphs of the adjacent curved surface portions corresponding to the inclined surface portion is formed to have a connection portion by using interpolation so that a first graph in which the phase graph of the central curved surface portion, the phase graph of the curved surface portion, and the connection portion are comprehensively connected is calculated. In the second graph calculation step, a second graph is calculated by primary differentiation of the first graph. In the reference thickness calculation step, a reference thickness that is a thickness of the central curved surface portion is calculated from a distance between points of inflection arranged on both sides of a differentiation graph of the central curved surface portion in the second graph. In the position determination step, a position of the phase graph of the curved surface portion is determined by using the reference thickness while fixing the phase graph of the central curved surface portion and moving the position of the phase graph of the curved surface portion by 2 p.

Description

[0001] The present invention relates to a method of measuring a shape of a lenticular lens having a Fresnel lens shape,

The present invention relates to a method for measuring a shape of a lenticular lens having a Fresnel lens shape, and more particularly to a method for measuring a shape of a lenticular lens having a Fresnel lens shape without phase ambiguity using a transmission type interferometer.

An interferometer is a type of interferometer that irradiates light onto the surface and reference plane of an object to be inspected, forms interference fringes from two types of light reflected or transmitted, measures and analyzes the interference fringes, .

Since such an interferometer can easily obtain the shape of the object to be measured, it has been widely used in the industrial field. Particularly, rapid technological development in all the recent industrial fields requires fine processing in the fields of semiconductor, MEMS, flat panel display, , And currently, nano-unit ultra precise manufacturing technology is required. Also, the required machining shape is changed from a simple pattern to a complicated shape. Accordingly, the importance of a technique for measuring a fine shape is more emphasized.

Phase-shifting interferometry (PSI) is an interferometry technique that uses phase-shifting interferometry (PSI). The phase-shift interferometry (PSI) .

Generally, when the height difference between two neighboring points measured by the transmission type phase shift interference method exceeds one half of the wavelength of the light source, a problem of 2? Ambiguity occurs. This problem causes an error in the shape measurement . In other words, when measuring a point that is one-half or more of the wavelength of the light source due to the abrupt change in the level difference, there is no way to determine the period of the phase unwrapping. The existing measurement method of calculating the minimum periodic value based on the minimum period value results in a different result from the state of the measurement surface of the actual measurement object, and thus the accurate shape of the measurement object can not be measured. This is a problem inherent to the measurement method, which is a disadvantage in contrast to the advantage of accurate measurement resolution.

To solve this problem, it is possible to consider a method of increasing the equivalent wavelength of the interference fringe by using a plurality of light sources, but the method of increasing the equivalent wavelength causes a problem that the measurement resolution is degraded.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to solve such a problem of the prior art and to solve the problem of 2? Ambiguity by determining an area in which other curved portions can exist based on the shape of the central curved portion among the Fresnel lens shapes, The present invention also provides a method of measuring the shape of a lenticular lens having a Fresnel lens shape capable of accurately measuring the shape of the lenticular lens having the Fresnel lens.

According to another aspect of the present invention, there is provided a method of measuring a shape of a lenticular lens having a Fresnel lens shape, comprising: a central curved surface portion through which a central axis aligned with an optical axis passes; A method of measuring a shape of a lenticular lens having a Fresnel lens shape having a plurality of symmetrically arranged curved portions and a plurality of inclined surface portions connecting ends of neighboring curved portions, A phase measuring step of measuring a phase of the phase difference; And a phase graph of the central curved surface portion and a phase graph of the curved surface portion are spaced apart from each other in the left and right direction and a portion corresponding to the inclined surface portion between the phase graphs of the adjacent curved surface portions is formed by using interpolation, A phase graph, a phase graph of the curved surface portion, and a first graph obtained by connecting the connecting portions as a whole; A second graph computing step of computing a second graph obtained by first differentiating the first graph; A reference thickness calculating step of calculating a reference thickness which is a thickness of the central curved surface portion from a distance between inflection points arranged on both sides of the differential graph of the central curved surface portion in the second graph; And a position determining step of fixing the phase graph of the central curved surface portion and determining the position of the phase graph of the curved surface portion by using the reference thickness while locating the phase graph of the curved surface portion at intervals of 2 pi.

In the method of measuring the shape of a lenticular lens having a Fresnel lens shape according to the present invention, more specifically, the phase measuring step may include measuring a phase of the central curved portion using a transmission type interferometer including a light source that generates light of a single wavelength, And the phase of the curved portion is measured.

In the method of measuring a shape of a lenticular lens having a Fresnel lens shape according to the present invention, the first graph calculation step may be performed before the end portions of the phase graph of the neighboring curved surface portions are connected to each other by the connecting portion, The phase graph of the central curved surface portion and the phase graph of the curved surface portion are arranged so as to be spaced apart in the vertical direction so that the end portions of the phase graph of the adjacent curved surface portions have a phase difference of?

In the method of measuring the shape of a lenticular lens having a Fresnel lens shape according to the present invention, more specifically, the reference thickness calculating step may include a step of calculating a reference thickness, Is defined as the reference thickness and the reference thickness is calculated using the width of the central curved portion obtained from the radius of curvature of the central curved portion and the distance between the inflection points.

In the method of measuring the shape of a lenticular lens having a Fresnel lens shape according to the present invention, more specifically, the position determining step may include determining a position where at least half of the phase graph of the curved surface portion is within the reference thickness, Confirm with the position of the graph.

According to the method for measuring the shape of the lenticular lens having the Fresnel lens shape of the present invention, the surface shape of the lenticular lens, which is essential for quality control of the lens, can be accurately measured without any uncertainty while minimizing the dead zone.

Further, according to the method for measuring the shape of the lenticular lens having the Fresnel lens shape of the present invention, the width of the central curved portion can be easily calculated in real time and applied to the actual measurement, so that the measurement accuracy of the transmission interferometer Can be applied.

1 is a flowchart of a method of measuring a shape of a lenticular lens having a Fresnel lens shape according to an embodiment of the present invention,
2 is a cross-sectional view of a lenticular lens having a Fresnel lens shape measured by a method for measuring a shape of a lenticular lens having a Fresnel lens shape shown in Fig. 1,
3 is a view schematically showing an example of a transmission type interferometer used in a method of measuring the shape of a lenticular lens having a Fresnel lens shape of Fig. 1,
FIG. 4 is a view for explaining a first graph calculating step of the shape measuring method of the lenticular lens having the Fresnel lens shape of FIG. 1,
5 is a view showing a first graph of a shape measuring method of a lenticular lens having a Fresnel lens shape of Fig. 1,
Fig. 6 is a diagram showing a second graph of the shape measuring method of the lenticular lens having the Fresnel lens shape of Fig. 1,
7 is a view for explaining the reference thickness calculating step of the shape measuring method of the lenticular lens having the Fresnel lens shape of Fig. 1,
FIG. 8 is a view for explaining the position determining step of the shape measuring method of the lenticular lens having the Fresnel lens shape of FIG. 1; FIG.

Hereinafter, embodiments of a method for measuring a shape of a lenticular lens having a Fresnel lens shape according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a cross-sectional view of a lenticular lens having a Fresnel lens shape, and FIG. 3 is a cross-sectional view showing an example of a transmission type interferometer according to an embodiment of the present invention. FIG. 5 is a diagram showing a first graph, FIG. 6 is a diagram showing a second graph, and FIG. 7 is a diagram showing a graph FIG. 8 is a view for explaining the step of calculating the thickness. FIG.

Referring to FIGS. 1 to 8, the shape measuring method of a lenticular lens having a Fresnel lens shape according to this embodiment measures the shape of a lenticular lens having a Fresnel lens shape without phase ambiguity using a transmission type interferometer, A first graph calculating step S120, a second graph calculating step S130, a reference thickness calculating step S140, and a position determining step S150.

2, the measurement object measured by the present invention is a lenticular lens 10, and the cross section of the lenticular lens 10 has a Fresnel lens shape. The lenticular lens 10 of the present invention is formed so that the cross section shown in Fig. 2 extends along the direction coming out from the ground or along the direction going into the ground.

The lenticular lens 10 to be measured includes a central curved surface portion 11, a plurality of curved surface portions 12, and a plurality of inclined surface portions 13. The central curved surface portion 11 passes through the center axis c of the lenticular lens 10 aligned with the optical axis and is arranged at the center of the lenticular lens 10. [ The plurality of curved surface portions 12 are disposed on both sides of the central curved surface portion 11 and arranged symmetrically with respect to the center axis c. A plurality of slanted surface portions 13 are formed to connect the end portions of the adjacent curved surface portions 12, respectively.

In FIG. 2, the central curved surface portion 11 and the curved surface portion 12 are shown as being concave. However, the lenticular lens having the central curved surface portion and the curved surface portion formed convexly may also be an object to be measured.

3, a transmission type interferometer 20 used in a method for measuring the shape of a lenticular lens 10 having a Fresnel lens shape as a measurement object includes a light source unit 21, a light splitter 22, a reflection mirror 25 A phase shift mirror 23, and a photodetector 26. The phase shift mirror 23 and the photodetector 26 constitute a phase shift mirror.

The light source unit 21 generates light L of a single wavelength, and a diode laser or the like can be used. A laser beam having a wavelength of about 555.5 nm can be generated from the light source unit 21. [

The light splitter 22 divides the light L generated from the light source unit 21 into two. A part of the divided light is reflected by the optical splitter 22 and transmitted to the reflecting mirror 25 side and the remaining part of the divided light is transmitted to the phase shift mirror 23 through the optical splitter 22.

A part of the light split by the light splitter 22 is incident on the reflection mirror 25, and the incident light is transmitted through the lenticular lens 10 and transmitted to the light detecting unit 26 side. The phase shift mirror 23 receives the remaining part of the light split by the light splitter 22 and transmits the incident light to the light detection unit 26 side without passing through the lenticular lens 10. [ Light passing through the reflection mirror 25 and light passing through the phase shift mirror 23 are respectively incident on the light detection unit 26 via the objective lens 27. [

The phase shifting mirror 23 is provided with a driving means 24 such as a piezoelectric element, and the phase shifting mirror 23 is linearly reciprocable. The phase of the light transmitted by the phase shift mirror 23 can be shifted at an appropriate interval while linearly reciprocating the phase shift mirror 23.

The light transmitted by the reflection mirror 25 and the light transmitted by the phase shift mirror 23 generate an interference fringe and can detect the interference fringe by using the light detection unit 26. [ Generally, as the photodetector 26, a CCD camera having a number of pixels suitable for an area to be measured is used.

The phase measurement step S110 measures the phase of the central curved surface portion 11 of the lenticular lens 10 and the phase of the curved surface portion 12. In the phase measurement step S110, the phase of the central curved surface portion 11 and the phase of the curved surface portion 12 are measured using the transmission type interferometer 20 including the light source for generating the light L of single wavelength shown in FIG. .

The first graph calculation step S120 calculates a first graph 110 in which a phase graph 111 of a central curved surface portion and a plurality of curved surface phase graphs 112 are connected as a whole.

When the shape of the lenticular lens 10 is measured using the transmission type interferometer 20, the phase graph 111 of the central curved portion and the phase graph 112 of each curved portion can be obtained. However, since light can not pass through the inclined surface portion 13, a phase graph of the inclined surface portion 13 can not be obtained.

4 and 5, a phase graph 111 of the obtained central curved surface portion and a plurality of curved surface phase graphs 112 are arranged in the lateral direction along the pixels of the camera, (13) is left in an empty space. That is, the phase graph 111 of the center curved surface portion and the phase graphs 112 of the plurality of curved surface portions are arranged in the left-right direction while being spaced apart from each other by a portion corresponding to the sloped surface portion 13.

As shown in Fig. 4, the phase graphs 111 and 112 of the neighboring curved surface portions are arranged in the above-described manner in the left-right direction, and the phase graphs 111 and 112 of the neighboring curved- The phase graphs 111 and 112 of the curved surface are spaced apart from each other.

That is, the range of the phase graph 112 of the curved surface portion is shifted in the vertical direction by 2π intervals after setting the range of + π upward and -π downward with respect to the other end 111b of the phase curve of the central curved portion. When the phase difference between the other end portion 111b of the phase graph of the center curved portion and the one end portion 112a of the phase graph of the curved surface portion falls within a range of? . The same principle is applied to the phase graph 112 of another neighboring curved surface part to arrange the phase graph 112 of the curved surface neighboring to the up and down direction.

After the position of the phase graph 111 of the center curved surface portion and the position of the phase graphs 112 of the plurality of curved surface portions are fixed as described above, the portion corresponding to the sloped surface portion 13 between the phase graphs 111 and 112 of the adjacent curved surface portions is interpolated The connection portion 113 is formed. The ends of the phase graphs 111 and 112 of neighboring curved surfaces are connected to each other by the connecting portion 113. Various interpolation methods known in the art such as polynomial interpolation and spline interpolation can be used as the interpolation method for forming the connection part 113, so that detailed description will be omitted.

5, a phase graph 111 of a central curved surface portion and a plurality of curved surface phase graphs 112 are disposed, and by connecting the phase graphs 111 and 112 of neighboring curved surfaces through the connecting portion 113, It is possible to calculate the first graph 110 in which the phase graph 111 of the curved portion, the phase graph 112 of the curved portion, and the connecting portion 113 are connected as a whole.

The second graph calculating step S130 calculates a second graph 120 that is a first derivative of the first graph 110. [ The connecting portion 113 of the first graph includes an inflection point. In the second graph 120, the differential graph 121 of the central curved portion and the differential graph 122 of the curved portion or the differential graph 122 of the curved portion, The inflection point 123 can be confirmed by the shape of the vertex positioned between the differential graphs 122.

The reference thickness calculating step S140 calculates a reference thickness t, which is the thickness of the central curved surface portion 11. The reference thickness t which is the thickness of the central curved portion is defined as the distance between the point 11c where the central axis c and the central curved portion 11 intersect and the end portions 11a and 11b of the central curved portion.

7, the distance d1 between the inflection points 123 arranged on both sides of the differential graph 121 of the central curved surface portion in the second graph 120 is calculated as the width w of the central curved surface portion. The width w of the central curved portion is defined as a linear distance between one end 11a and the other end 11b of the central curved portion.

Since the width w of the central curved portion calculated from the distance d1 between the curvature radius r of the central curved portion and the inflection point 123 is known, the value of x can be obtained. If the value of x is subtracted from the curvature radius r of the central curved portion, the reference thickness t to be obtained can be calculated.

The position determination step S150 determines the position of the curved surface phase graph 112 using the reference thickness t.

The phase graph 111 of the center curved portion obtained in the phase measurement step S110 and the phase graph 112 of the curved portion still have 2? Ambiguity. Therefore, it is impossible to determine the relative positions of the phase graph 111 of the central curved surface portion and the phase graph 112 of the curved surface portion without any clear reference. If the reference thickness t calculated in the reference thickness calculating step S140 is 2π ambiguity It is a standard that can be solved.

8, a phase graph 112 of a curved surface portion disposed on both sides of the central curved surface portion 11 is moved in the vertical direction at intervals of 2 pi while the phase graph 111 of the central curved surface portion is fixed. If more than half of the curved surface phase graph 112 is included within the reference thickness t while locating the phase graph 112 of the curved portion at a distance of 2 pi, the position is determined to be the position of the curved surface phase graph 112 .

In the case of the lenticular lens 10 having the Fresnel lens shape, since the plurality of curved portions 12 have a shape that is mostly disposed in the thickness of the central curved portion 11, Determining to the position of the phase graph 112 may be an accurate reference for resolving the 2? Ambiguity.

The edges of the neighboring curved surface phase graphs 111 and 112 can be connected to the slant line 116 by linear interpolation to secure the measured shape of the lenticular lens 10 as a whole.

The method of measuring the shape of the lenticular lens having the Fresnel lens shape according to the present embodiment configured as described above determines an area where other curved surfaces can exist based on the shape of the central curved surface portion of the Fresnel lens shape to solve the 2π ambiguity problem Thus, the surface shape of the lenticular lens, which is essential for quality control of the lens, can be accurately measured without any uncertainty in a state in which the dead zone is minimized.

In the method of measuring the shape of the lenticular lens having the Fresnel lens shape according to the present embodiment configured as described above, the width of the central curved portion is calculated on the basis of the inflection point protruding from the differentiated graph, Can be easily calculated in real time and applied to the actual measurement, and it is possible to apply the high measurement accuracy of the transmission type interferometer without fear of occurrence of measurement ambiguity.

The scope of the present invention is not limited to the above-described embodiments and modifications, but can be implemented in various forms of embodiments within the scope of the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

10: Lenticular lens having a Fresnel lens shape
11: central curved portion
12:
13:
110: first graph
111: Phase graph of center curved surface
112: Phase graph of curved surface
120: second graph
121: Differential graph of center curved surface
123: inflection point

Claims (5)

A central curved surface portion through which a central axis aligned with the optical axis passes, a plurality of curved surface portions symmetrically arranged with respect to the center axis on both sides of the central curved surface portion, and a plurality of inclined surface portions connecting end portions of neighboring curved surface portions, A method of measuring a shape of a lenticular lens having a lens shape,
Measuring a phase of the central curved portion and a phase of the curved portion;
And a phase graph of the central curved surface portion and a phase graph of the curved surface portion are spaced apart from each other in the left and right direction and a portion corresponding to the inclined surface portion between the phase graphs of the adjacent curved surface portions is formed by using interpolation, A phase graph, a phase graph of the curved surface portion, and a first graph obtained by connecting the connecting portions as a whole;
A second graph computing step of computing a second graph obtained by first differentiating the first graph;
A reference thickness calculating step of calculating a reference thickness which is a thickness of the central curved surface portion from a distance between inflection points arranged on both sides of the differential graph of the central curved surface portion in the second graph; And
And a position determining step of determining a position of the phase graph of the curved surface portion by using the reference thickness while fixing the phase graph of the central curved surface portion and moving the phase graph of the curved surface portion at an interval of 2 pi, A method for measuring a shape of a lenticular lens having a lens shape. The method according to claim 1,
Wherein the phase measuring step comprises:
Wherein a phase of the central curved portion and a phase of the curved portion are measured using a transmission type interferometer including a light source that generates light of a single wavelength. The method according to claim 1,
The first graph computing step may include:
The phase graph of the central curved surface portion and the phase graph of the curved surface portion are vertically shifted so that the ends of the phase graph of the neighboring curved surface portion have a phase difference of less than or equal to? Before the ends of the phase graph of the neighboring curved surface portions are connected to each other by the connecting portion, Of the lenticular lens having the Fresnel lens shape. The method according to claim 1,
Wherein the reference thickness calculating step includes:
A distance between a point where the center axis intersects the center curved surface portion and an end portion of the central curved surface portion is defined as the reference thickness,
Wherein the reference thickness is calculated by using a width of a central curved portion obtained from a radius of curvature of the central curved portion and a distance between the inflection points. The method according to claim 1,
The positioning step includes:
Wherein a position of at least half of the phase graph of the curved portion within the reference thickness is determined as the position of the phase graph of the curved portion.

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