KR101587641B1 - Filtering device for improving color saturation and color gamut - Google Patents

Abstract

According to an aspect of the present invention, a filtering device with an increased color reproduction rate and an extended color reproduction range is provided. According to an embodiment of the present invention, the filtering device includes: a wave guide which guides light in a guide mode predetermined with respect to incident light; and a grid which is patterned in a two-dimensional, asymmetric, and rectangular model and has the distance of pitch x and y in an x direction and a y direction, which is determined according to a penetrating color. According to the present invention, the color reproduction rate is increased and the color reproduction range is extended by the filtering device having an extended spectrum bandwidth with respect to a given sideband.

Description

TECHNICAL FIELD [0001] The present invention relates to a filtering device having improved color reproduction rate and color reproduction range,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a filtering apparatus with improved color saturation and color gamut, and more particularly, to a filtering apparatus having an extended spectral bandwidth that extends color gamut and color reproduction range.

Color filters are an important element used in displays, imaging devices, biosensors, solar cells, active color pixels, polarization detectors, and security tags. Color filters have also been developed to improve performance in terms of high transmittance, narrow bandwidth, polarization independence, high angle tolerance and wide spectrum tuning range. Here, the variable conversion characteristic can be dynamically adjusted by the incident angle, the micro-engineering drive and the electric optical effect. Efficient spectral tuning for a square grating structure is made possible with the aid of an incident light polarizer. Recently, central wavelength and transmissivity are mainly considered as advantages of color filters. However, in order to optimize the color response of the filter, the characteristics of the spectral response such as spectral wavelength and sideband levels must be carefully considered. In view of the practical application of the display and image areas, the color gamut and the color gamut must be evaluated as the main parameters of the color filter. Color saturation is known to contribute to visual perception and is indicative of the degree of color sensibility distinct from achromatic sensation, regardless of perceived brightness. The color gamut is quantitatively measured in terms of excitation purity of a colorimetric analysis, and a color gamut is a range of colors that can be reproduced in a device or system. The color reproduction rate and color reproduction range are preferably extended, which enables the imitation of the natural color of the object. However, until recently, no attempt has been made to improve the color reproduction rate or the color reproduction range through the visible filter based on the resonance lattice.

The background art of the present invention is disclosed in Korean Registered Patent No. 10-0552279 (registered on Mar. 02, 2008, Color Filter Substrate).

The present invention provides a filtering device with improved color reproduction rate and color reproduction range.

The present invention provides a filtering device with an extended spectrum bandwidth that improves the color gamut and increases the color gamut for a given sideband.

Other objects of the present invention will become readily apparent from the following description.

According to an aspect of the present invention, there is provided a filtering apparatus with improved color reproduction rate and color reproduction range.

The filtering apparatus according to an embodiment of the present invention is patterned into a waveguide and a two-dimensional asymmetric rectangular pattern guiding light in a guide mode set in advance with respect to incident light, and the distance between the pitches x and y in the x- and y- , And the distances of the pitches x and y include a grating determined according to the transmitted color.

According to the present invention, for a given sideband, a color reproduction rate can be improved and a color reproduction range can be increased through a filtering device having an extended spectrum bandwidth.

1 is a schematic structural view of a filtering apparatus according to a preferred embodiment of the present invention;
2 is a view for explaining transmission characteristics of a filtering device according to an embodiment of the present invention;
3 is a view for explaining a result of chromaticity coordinates in a chromaticity diagram of a filtering apparatus according to an embodiment of the present invention.
FIGS. 4 and 5 are diagrams for explaining a change in chromaticity coordinates according to various center wavelengths with respect to a given sideband in a filtering apparatus according to an embodiment of the present invention. FIG.
FIGS. 6 and 7 are diagrams for explaining the effect of a change in the excitation purity of colors and the 3 dB bandwidth at the dominant wavelength, according to an embodiment of the present invention. FIG.
FIGS. 8 and 9 are views for explaining a 3 dB bandwidth and a center wavelength shift depending on a thickness of a coating layer according to an embodiment of the present invention. FIG.
10 to 12 are views for explaining switching characteristics of different filtering apparatuses according to an embodiment of the present invention.
13 shows chromaticity coordinates of filters BG-1, BR-1 and GR-1 and BG-2, BR-2 and GR-2 of different polarizations connected by broken lines and solid lines respectively according to an embodiment of the present invention FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Also, when a part is referred to as "including " an element, it is to be understood that it may include other elements as well, without departing from the other elements unless specifically stated otherwise.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

1 is a schematic structural view of a filtering apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a filtering apparatus 100 according to an embodiment of the present invention includes a grating 110 and a waveguide 120.

The grating 110 is patterned into a two-dimensional asymmetric rectangular pattern and has distances of pitches x and y according to the x direction and the y direction, and the distances of the pitches x and y are determined according to the transmitted color. . The grating 110 may be made of a metal, for example, an aluminum (Al) film. The grating 110 may be coupled to the waveguide 120.

The waveguide 120 guides the light to the guide mode in a predetermined guide mode. The waveguide 120 may include a SiO ₂ coating layer (n = 1.457) 122, a Si ₃ N ₄ core (n = 2.023) 124 and a quartz substrate 126.

The filtering apparatus 100 is operated based on guided-mode resonance (GMR) between the guiding mode of the waveguide 120 and the diffracted light generated by the grating. Filtering device 100 may each have transmission peaks corresponding to green and red depending on two optical polarization Lx and Ly with a 3 dB bandwidth ([Delta] [omega]). The chromaticity coordinates in the CIE 1931 chromaticity diagram for the transmitted color output are determined by the polarization angle corresponding to the alignment of the electric field in the x-axis direction.

The color recall ratio is quantitatively measured in terms of excitation purity depending on the distance between the outer boundary of the chromaticity diagram and the white point, and depends on the resonance peak Δω.

The color reproduction range can be defined as the range of colors available from the device, in view of the fact that the change in optical polarization changes the color output of the proposed dual band filter. And this depends on the separated coordinates on the chromaticity diagram corresponding to the points for the &thetas; = 0 and 90 DEG polarization angles. If the chromaticity coordinates are largely separated, the color reproduction range becomes larger, and vice versa.

The filtering device 100 may be a single band or a dual band color filter.

The filtering device 100 may include, for example, a metal lattice 110 having a pitch x = 355 nm and a y = 395 nm, a 100 nm thick core 124 in Si ₃ N ₄ , and a 100 nm thick SiO ₂ And may include a planar waveguide 120 having a covering layer 122.

2 is a view for explaining transmission characteristics of a filtering device according to an embodiment of the present invention.

2, transmission characteristics for different incident polarization angles Θ = 0 °, 45 °, and 90 ° are examined through a finite difference time domain (FDTD) method for the filtering apparatus 100 .

The grating 110 has a grating filling ratio defined as a ratio of the width of the metal pattern to the grating pitch of 0.7 in terms of transmittance in the visible spectrum region. 2, the first order resonance peaks for Lx (? = 0 °) and Ly (? = 90 °) polarization at? = 558 and 612 nm are observed with a transmission of almost 85% = 45 [deg.], The permeability is firstly about two average values. The reason may be as follows. When light is incident on the x-axis with an electric field E aligned at an angle Θ, the output power is proportional to TΘ (λ) E ² . Here, T? (?) Is the transmittance for the polarization angle? Of the incident light. The electric field E of the incident light is represented by E cos? And E sin? Along the two elements, the x axis and the y axis. The transmittances T _x (λ) and T _y (λ) for light polarized along the x and y axes are such that the transmitted power due to the first or second element is T _x (λ) E ² cos ² and T _y ([lambda]) E ² sin ² . Therefore, the overall output depends on E ² [T _x (λ) cos ² + T _y (λ) sin ² ]. As a result, the transmittance of the polarization angle in the angle _{T (λ) = T x (} λ) cos 2 + T y (λ) is given by sin ^2, the output polarization state of the light and is not related.

As shown in Figure 2, the major peak bands for the spectral bands of green and red are ~ 13 and 15 nm. Using the transmittance of the color filter, the colors to be represented can be calculated using standard equations. To calculate the chromaticity coordinates in the CIE 1931 chromaticity diagram, the values of the XYZ tristimulus for color with the spectral transmittance T (λ) are calculated using the following formula:

이고,

은 CIE 1931 표준 색도 관찰자 컬러 매칭 함수들이고,

는 CIE 정규화된 광원 E, 표준 광원의 상대적인 스펙트럼 출력 분포이고, 합산(summation)은 파장 간격

이 1 ㎚ 와 같은 상태에서 360부터 830 ㎚의 가시스펙트럼 대역의 범위를 넘어서 수행되고, 상수 k는 모든 파장을 위해

인 물체를 위하여 Y가 100과 같다고 한 것과 같은 방법으로 선택된다. here,

ego,

Are CIE 1931 standard chromaticity observer color matching functions,

Is the relative spectral power distribution of the CIE normalized light source E, the standard light source, and the summation is the wavelength spacing

Is performed beyond the visible spectral band from 360 to 830 nm in the same state as 1 nm, and the constant k is for all wavelengths

Is selected in the same way as Y is equal to 100 for an object.

  Finally, the chromaticity coordinates (x, y) are given by

3 is a view for explaining the result of chromaticity coordinates in a chromaticity diagram of a filtering apparatus according to an embodiment of the present invention.

Referring to FIG. 3, chromaticity coordinates result in a CIE 1931 chromaticity diagram corresponding to the spectral response when changing from 45 ° to 45 ° from 0 = 0 ° to 90 °. In this case, the output color changes from green to red, which means that the output color is efficiently controlled by the polarization. Although the proposed filter device shows that the resonant wavelengths include green and red, the chromaticity coordinates of the output colors indicate a poor color reproduction rate. It can be seen from the chromaticity diagram that the two polarizations for Θ = 0 ° and 90 ° and the corresponding chromaticity coordinates are closely distributed to one another and exhibit a narrow reproducibility range. It is assumed that the poor color reproduction rate arises from notable transmittance in the non-resonant sideband. In order to reproduce the natural color of the object more satisfactorily, the color recall ratio and the color reproduction range need to be preferably extended. The sideband transmission can be efficiently reduced according to the arrangement in combination with the Bragg reflection plane of the multi-layer structure. However, this approach is only valid for a limited spectrum and angular range, and there is a limitation that each thickness must be precisely controlled due to the multilayer structure. On the other hand, the device consists of a single dielectric waveguide with metal gratings, and is characterized by the transmission peak of the waveguide mode resonance structure through excellent reflection characteristics over a wide spectrum and angular range. In addition, we have developed a method to improve the color reproduction rate or increase the color reproduction range by checking the spectral response related to the chromaticity coordinates in the proposed apparatus. The resonance spectra of the filter utilizing the guided-mode resonance (GMR) effect are expressed by a Lorentzian function defined by the following equation (3).

Where T _o is the sideband transmittance, T ₁ is the peak transmittance of the resonant peak, Δω is the 3-dB bandwidth of the resonant peak, and λ _o is the center wavelength of the resonant peak.

To investigate the λ _o, the effect of the transmission characteristic including a △ ω and T _o of the output color in detail, and track the chromaticity coordinates with respect to the parameters mentioned above optionally in the fixed transmission rate of 90%. Two different considerations were considered, with and without sideband levels, for example, T _o = 0 and T _o ≠ 0. First, the level of the sideband negligible if the (T _o = 0) has a 5 ㎚ interval in the range of the chromaticity coordinates △ ω is 5 to 30 ㎚, λ _o is identified 10㎚ interval from 450 to 650㎚ .

4 and 5 are views for explaining a change in chromaticity coordinates according to various central wavelengths with respect to a given sideband in a filtering apparatus according to an embodiment of the present invention.

Referring to FIG. 4, the change in output color from blue to green to finally red shifts clockwise along the direction indicated by the black arrow by adjusting the central wavelength? _O determined by the lattice pitch. This is like following the direction of the horseshoe outline of the hue diagram. As Δω increases, the chromaticity coordinates corresponding to a given λ _o and filter transparency move toward the white point E of the diagram, as indicated by the blue arrow. In such a case, the color purity / color gamut decreases.

Referring to FIG. 5, for a constant sideband level (T _o = 0.05), the chromaticity coordinates shift from blue to green through red with λ _o for a given Δω, similar to the previous case. However, unlike the preceding situation of the sideband level of zero, the chromaticity coordinates corresponding to the increased [Delta] [omega] and the given [lambda] _o and filter transmittance gradually diverge from the white point E toward the spectral curve of the diagram. This shows that the color reproduction rate improves as? W increases. In addition, for any other nonzero sideband transmission, the movement of chromaticity coordinates moving from the white point toward the spectral curve of the chromaticity diagram is similarly observed. As a result, with respect to a given transmission and sideband level filtering apparatus, the color gamut can be improved by enlarging the bandwidth DELTA omega.

Then, in order to examine the quantitative aspect of the color recall ratio, the excitation purity of the color with respect to the filter transmittance was investigated. In the chromaticity diagram, the dominant wavelength (λ _D ) for the given chromaticity coordinates is first determined, and a straight line connecting the length of the straight line connecting the chromaticity coordinates of the reference white point E with the point of interest and the reference white point to the dominant wavelength The excitation purity is calculated at a ratio of length.

Figs. 6 and 7 are diagrams for explaining the excitation purity of colors and the influence of the change of the 3 dB bandwidth (DELTA omega) at the dominant wavelength according to an embodiment of the present invention.

If 6, blue, green, for a λ _o = 450, 550 and 650 respectively corresponding to the red region, is not present and ((T _o = 0) When particularly the sideband level present (T _o = 0.05), the influence of the change of DELTA omega in the excitation purity of the colors for Lorentz filter response given by the above-mentioned equation (3) is shown.

Referring to Figure 7, the dominant wavelength of the Lorentzian response of a given < RTI ID = 0.0 > _o < / RTI > for zero and non-zero sideband levels indicates that a small change is seen, The excitation purity reaches its maximum value when it increases from λ _o = 450 and 550 nm to λ _o = 650 nm. Thus, it can be seen that as the number of filters increases, the excitation purity of the available green and red color outputs from the filter is improved.

Further, the spectral bandwidth of the pass band can be increased as the thickness of the coating layer decreases. In order to investigate the bandwidth tunability of the apparatus of the present invention, the spectral response was investigated by changing the thickness of the coating layer from 30 to 210 at 30 intervals.

FIGS. 8 and 9 are views for explaining the 3 dB bandwidth and the center wavelength shift depending on the thickness of the coating layer according to an embodiment of the present invention.

Referring to FIG. 8, when the thickness of the coating layer was reduced from 210 to 30 nm, the bandwidth increased from about 3 to 29 nm for the green spectral band of Lx polarized light. On the other hand, for the red spectral band of Ly polarized light, the bandwidth increased from about 8 to 32 nm.

Referring to Fig. 9, the bandwidth can be adjusted while slightly shifting the resonance frequency according to the variation of the coating layer thickness. The resonance bandwidth Δλ _o when the thickness of the coating layer was 210 nm was examined for the change of the coating layer thickness from 30 to 210 nm. The relative bandwidth shift in Fig. 9 is defined as [Delta] [lambda] _o / [lambda] _o and is shown to be even smaller.

FIGS. 10 to 12 are views for explaining switching characteristics of different filtering apparatuses according to an embodiment of the present invention.

Referring to Figures 10-12, for a coplanar waveguide of 100-thickness Si ₃ N ₄ core and 100-nm SiO ₂ coating, the lattice period is 462 for blue, green and red in the x- and y- 558 and 612 nm and a transmittance of more than 85%. Further, when a bandwidth of ~ 15 nm was set for the other band, and xx / yy = 285/355 ㎚, xx / yy = 285/395 ㎚ and xx / yy = 355/395 ㎚ Blue (BG), blue-red (BR), and green-red (GR) filters by adjusting the grating period.

Further, as shown by the solid line in Figs. 10 to 12, when the thickness of the coating layer is reduced to 30 nm, the spectral bandwidth DELTA omega causes a small shift at &thetas; _o and widens to 32 nm . 2, BR-2 and GR-2, which have a wide bandwidth when t = 30 and have a coating thickness t = 100 and have a narrow bandwidth, are designed as BG-1, BR-1 and GR- Can be designed.

13 shows chromaticity coordinates of filters BG-1, BR-1 and GR-1, BG-2, BR-2 and GR-2 of different polarizations connected by broken lines and solid lines respectively according to an embodiment of the present invention Fig.

Referring to FIG. 13, the direction of the arrow indicates a change in chromaticity coordinates when? Changes from 0 degrees to 90 degrees. In addition, for each filter, the dots in the chromaticity coordinates represent the chromaticity coordinates at Θ = 0, 45, and 90 °. It is clear from Figs. 10 to 12 that regions such as triangles are surrounded by three cases of BG, BR and GR. This represents the area of colors that can be reproduced due to the use of filters. The chromaticity coordinates in the devices of BG-1, BR-1 and GR-1 are very close to the white point E. This shows poor color reproduction and low excitation purity. Conversely, in the case of BG-2, BR-2 and GR-2 filters, the chromaticity coordinates are distributed farther from the white point E, leading to high excitation purity or color gamut. Moreover, the separation of the chromaticity coordinates of the filters for the other polarizations is larger for the BG-2, BR-2 and GR-2 filters and provides a larger color reproduction range. Thus, the color reproduction rate as well as the color reproduction range was found to be better for a broader spectrum corresponding to a 30 nm thick coating than for a 100 nm thick coating. The calculated chromaticity coordinates, dominant wavelength and excitation purity for each point in the chromaticity diagram for the calculated spectral response of the six different filters are summarized for different incident polarization angles to Table 1, Table 2 and Table 3 to be shown below. If the dominant wavelength is not well defined, the auxiliary wavelength is indicated in the tables as '(c)'. The wavelength associated with the point in the horseshoe curve is defined as the auxiliary wavelength at the intersection of the extrapolated straight line in the other direction (from the point of interest to the reference white point). It can be seen from FIG. 13 and Table 1, Table 2 and Table 3 that the excitation purity and color reproduction range increase with a wider bandwidth.

Theoretical colorimetric parameters of blue-green filters for different coating thicknesses
BG-1 BG-2 Chromaticity coordinates
(x, y) _{? D} (nm) Purity here Chromaticity coordinates
(x, y) _{? D} (nm) Purity here 0 (0.29, 0.18) 565 (c) 0.36 (0.24, 0.13) 569 (c) 0.48 45 (0.28, 0.31) 486 0.18 (0.26, 0.32) 490 0.24 90 (0.28, 0.40) 510 0.17 (0.29, 0.53) 541 0.47

Theoretical colorimetric parameters of blue-red filters for different coating thicknesses
BR-1 BR-2 Chromaticity coordinates
(x, y) _{? D} (nm) Purity here Chromaticity coordinates
(x, y) _{? D} (nm) Purity here 0 (0.28, 0.16) 565 (c) 0.42 (0.27, 0.12) 564 (c) 0.53 45 (0.38, 0.26) 510 (c) 0.34 (0.40, 0.24) 511 (c) 0.43 90 (0.47, 0.38) 607 0.42 (0.53, 0.36) 600 0.65

Theoretical colorimetric parameters of Green-Red filters for different coating thicknesses
GR-1 GR-2 Chromaticity coordinates
(x, y) _{? D} (nm) Purity here Chromaticity coordinates
(x, y) _{? D} (nm) Purity here 0 (0.27, 0.37) 501 0.18 (0.31, 0.52) 548 0.51 45 (0.36, 0.35) 583 0.15 (0.42, 0.44) 575 0.61 90 (0.46, 0.33) 611 0.39 (0.53, 0.37) 596 0.71

GMR filter devices having a certain sideband level can not only not only expand the excitation purity, which is a measure of the color reproduction rate, but also the color reproduction range, by increasing the bandwidth of the pass band. In order to optimize the color reproducible properties of the filter, the resonant wavelength and maximum transmittance as well as the spectral bandwidth and the sideband level of the spectral response must be considered. In addition, the display system can be implemented in various ways such as by extending the triangular color reproduction range. Thus, the filtering device shows an adjustable spectral response exhibiting polarization selective characteristics, the center wavelength is determined by the lattice period, and the bandwidth can be controlled by the coating layer thickness. It can also be very useful when designing color filters that extend color gamut and color reproduction range. In addition, the invention can be equally effective in other cases, such as surface plasmon resonance based on thin films or filters.

The invention has been demonstrated using a filtering device combined with a two-dimensional asymmetric resonant lattice structure showing a spectral response that can be adjusted by polarization with a method of extending color gamut and color reproduction range. In particular, the effects of spectral bandwidth, the color recall ratio and the color reproduction range according to the resonance bandwidth and the sideband transmission were theoretically investigated through the spectral response of the chromaticity coordinates of the CIE 1931 chromaticity diagram. Between two filtering devices having a bandwidth of about ~ 15 and 32 nm, it can be seen that devices with wider bandwidth have higher excitation purity, better color gamut and better color reproduction range. The present invention can be sufficiently applied to improve the performance of various kinds of display applications.

The embodiments of the present invention have been described above. 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 invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

100: Filtering device 110: Grid
120: waveguide 122: coating layer
124: core 126: substrate

Claims (8)

A filtering device comprising:
The filtering device includes:
A waveguide for guiding light in a guide mode set in advance with respect to incident light; And
Dimensional asymmetric rectangular model and has a distance of pitches x and y according to the x direction and the y direction, and the distances of the pitches [theta] x and [gamma] y include gratings determined according to the transmitted color: In addition,
The waveguide
A dielectric core deposited on the quartz substrate, and a coating layer,
The filtering device controls the 3 dB bandwidth (?) Of the resonance peak of the filtering device by adjusting the thickness of the coating layer,
The thickness of the coating layer is determined so as to increase the color reproduction ratio of the filtering device by increasing the 3 dB bandwidth (??) Of the resonance peak when a constant sideband level exists.
Wherein the thickness of the coating layer is determined so as to improve the color reproduction rate of the filtering device by reducing the 3 dB bandwidth (?) Of the resonance peak when the sideband level does not exist.
delete delete delete delete delete The method according to claim 1,
Wherein the grating has a lattice fill ratio of 0.7, wherein the lattice fill ratio is defined as a ratio of the width of the lattice pattern to the lattice pitch. The method according to claim 1,
Wherein the filtering device is a single band color filter or a dual band color filter.

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