KR102397972B1 - Circular polarization device, notch filter and bandpass filter including the same - Google Patents

Abstract

A circular polarizer of the present invention includes: a pair of substrates extending in a horizontal direction; a liquid crystal alignment layer coated on one surface of each of the pair of substrates; a plurality of spacers disposed between the pair of substrates or the liquid crystal alignment layer; a cholesteric liquid crystal (CLC) layer positioned in the space secured by the spacer and including any one of a left-handed chiral material and a right-handed chiral material; a continuous pitch adjusting means for circularly polarizing light of a wavelength band that is continuously changed according to a region along the horizontal direction; may include

Description

CIRCULAR POLARIZATION DEVICE, NOTCH FILTER AND BANDPASS FILTER INCLUDING THE SAME

The present disclosure relates to a circular polarizing element, a notch filter and a band-pass filter including the same, and more particularly, to a circular polarizing element that does not require a phase retarder, and a notch filter and a band-pass filter using the circular polarizing element.

Light is an electromagnetic wave that travels with periodic changes in the strength of electric and magnetic fields. Natural light is an electromagnetic wave with a periodic change in the strength of an electric field in all directions of 360 degrees. Among the components of natural light, it has polarization characteristics by the direction of the electric field in an arbitrary plane perpendicular to the traveling direction.

The types of polarization include linear polarization, circular polarization, and elliptically polarized light. Circular polarization includes left-circular polarization in which the direction of the electric field of light rotates in a counterclockwise direction and right-circular polarization in which the direction of the electric field of light rotates in a clockwise direction. Linear polarization is the sum of right circularly polarized light and left circularly polarized light. The polarization characteristic of light is used in an optical element or a display element.

Meanwhile, in general, circularly polarized light may be obtained by passing the linearly polarized light passing through the linear polarization element through a phase retarder. However, the phase retarder is expensive, and in order to use the phase retarder, optical knowledge is required because the optical axis direction of the polarizer and the phase retarder must be aligned.

Accordingly, there is a need for a circularly polarized light element capable of obtaining circularly polarized light for several wavelengths with one element without using several phase retarders and a filter using the circularly polarized element.

SUMMARY OF THE INVENTION The present disclosure is to solve the above-described problem, and an object of the present disclosure is to provide a circular polarizing device capable of obtaining circularly polarized light for a plurality of wavelengths with one device without using a phase retarder.

Another object of the present disclosure is to provide a notch filter and a band pass filter using a circular polarizer.

In addition, an object of the present disclosure is to provide a notch filter and a band pass filter having excellent characteristics even when inputting a high energy laser light source.

A circular polarizer of the present invention includes: a pair of substrates extending in a horizontal direction; a liquid crystal alignment layer coated on one surface of each of the pair of substrates; a plurality of spacers disposed between the pair of substrates or the liquid crystal alignment layer; a cholesteric liquid crystal (CLC) layer positioned in the space secured by the spacer and including any one of a left-handed chiral material and a right-handed chiral material; a continuous pitch adjusting means for circularly polarizing light of a wavelength band that is continuously changed according to a region along the horizontal direction; may include

The continuous pitch adjusting means may include a power supply for supplying a voltage to at least one of the pair of substrates.

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As described above, according to various embodiments of the present disclosure, the circularly polarized light may obtain circularly polarized light without a phase retarder.

In addition, a user can use an inexpensive and simple circular polarizer.

In addition, according to various embodiments of the present disclosure, circularly polarized light may be obtained at all wavelengths within a predetermined wavelength region (photonic band gap, PBG) with one circular polarizing element.

And, according to various embodiments of the present disclosure, a notch filter and a band pass filter using a circular polarizer may be used.

Also, according to various embodiments of the present disclosure, a notch filter and a band pass filter using a circular polarizer may perform a function of a tunable filter for various wavelengths.

Meanwhile, according to various embodiments of the present disclosure, the band pass filter may be implemented without a beam splitter.

In addition, according to various embodiments of the present disclosure, a notch filter and a band pass filter using a circular polarizer may have excellent characteristics even when inputting a high energy laser light source.

1 is a view for explaining the structure of a circular polarizer according to an embodiment of the present disclosure.
2A and 2B are views for explaining right-circularly polarized light and left-circularly polarized light according to an embodiment of the present disclosure;
3 is a view for explaining a circular polarizer including spacers of different sizes according to an embodiment of the present disclosure.
4 is a view for explaining a circular polarizer using a concentration difference of a chiral material according to an embodiment of the present disclosure.
It is a figure explaining an azo dye.
6 is a view for explaining a circular polarizer using an azo dye according to an embodiment of the present disclosure.
7 is a view for explaining a circular polarizer using a concentration difference of an azo dye according to an embodiment of the present disclosure.
8 is a view for explaining a circular polarizer using an azo dye and an ND filter according to an embodiment of the present disclosure.
9 is a view for explaining a circular polarizer using heat according to an embodiment of the present disclosure.
10 is a view for explaining a circular polarizer using a temperature gradient according to an embodiment of the present disclosure.
11 is a view for explaining a circular polarizer using an electric field according to an embodiment of the present disclosure.
12 is a view for explaining a circular polarizer using a rotator according to an embodiment of the present disclosure.
13 to 19 are views for explaining a notch filter according to various embodiments of the present disclosure.
20 and 21 are diagrams for explaining a method of implementing a notch filter according to another embodiment of the present disclosure.
22 and 23 are diagrams for explaining a notch filter according to another embodiment of the present disclosure.
24 is a diagram illustrating an output waveform of a notch filter according to an embodiment of the present disclosure.
25 to 38 are diagrams for explaining a band pass filter according to various embodiments of the present disclosure.
39 is a diagram illustrating an output waveform of a band pass filter according to an embodiment of the present disclosure.
40 and 43 are views for explaining a method of implementing a filter including a plurality of cholesteric liquid crystals according to an embodiment of the present disclosure.
44 to 45 are views for explaining the structure of a filter including a plurality of cholesteric liquid crystal layers according to an embodiment of the present disclosure.
46 to 48 are views for explaining a notch filter including a plurality of cholesteric liquid crystal layers according to an embodiment of the present disclosure.
49 to 54 are views for explaining a band pass filter including a plurality of cholesteric liquid crystal layers according to an embodiment of the present disclosure.
55 is a view for explaining a composite filter including a band pass filter and a notch filter according to an embodiment of the present disclosure.
56 is a diagram illustrating an output waveform of a filter according to an embodiment of the present disclosure.

1 is a view for explaining the structure of a circular polarizer according to an embodiment of the present disclosure.

Referring to FIG. 1 , the circular polarizer 100 includes substrates 110a and 110b, polyimide layers (PI) 120a and 120b, spacers 130 and cholesteric liquid crystal (CLC). (140).

First, a pair of substrates 110a and 110b is prepared. For example, the substrates 110a and 110b may be made of Indium Tin Oxide (ITO), glass, or plastic, and if necessary, the substrate may be used with anti-reflective coating on one side or both sides of the incident light beam. Polyimide layers 120a and 120b are coated on one surface of each of the pair of substrates 110a and 110b. Polyimide has properties of high heat resistance, electrical insulation, flexibility and non-combustibility without changing its physical properties over a wide range of temperatures. For example, the polyimide may be a Kapton made by condensation of pyromellitic dianhydride and 4,4'-oxydianiline. In addition, polyimide may be classified into an aliphatic compound (Aliphatic), a semi-aromatic compound (Semi-aromatic), and an aromatic compound (Aromatic) according to the configuration of the linkage. The polyimide layers 120a and 120b may be subjected to a rubbing treatment as necessary.

A plurality of spacers 130 are disposed to secure a space between the polyimide layers 120a and 120b. That is, after the polyimide layers 120a and 120b are coated on one surface of each of the pair of substrates 110a and 110b, the respective polyimide layers 120a and 120b are disposed to face each other. In addition, a spacer 130 for securing a space is disposed between the polyimide layers 120a and 120b facing each other.

The cholesteric liquid crystal 140 is disposed between the spacers 130 . The cholesteric liquid crystal 140 includes a bar-shaped nematic liquid crystal and a chiral material having a preset concentration. The chiral material includes a left-handed chiral material that reflects left-circularly polarized light and a right-handed chiral material that reflects right-circularly polarized light. That is, when a left-handed chiral material is added to the cholesteric liquid crystal 140 , the nematic liquid crystal is arranged in a counterclockwise spiral. And, when a preferential chiral material is added to the cholesteric liquid crystal 140 , the nematic liquid crystal is arranged in a clockwise spiral. Right-circular polarization characteristics and left-circular polarization characteristics of the circular polarization element will be described later.

The circular polarizer 100 may be manufactured by filling a wedge or an equally spaced cell with a cholesteric liquid crystal 140 including a chiral material having one characteristic. That is, the cholesteric liquid crystal 140 is a mixture of a nematic liquid crystal and a chiral material and has a spontaneously assembled spiral structure. Selective reflection occurs in a specific wavelength region with respect to circularly polarized light such as the rotational spiral direction of the cholesteric liquid crystal 140 . This reflection is called the Bragg reflection, and the central wavelength is λB = n × p, and the bandwidth is given by Δλ = p × Δn, where p is the pitch (pitch: the helical structure of cholesteric liquid crystals is 360 degrees) The distance traveled during rotation), n is the average refractive index, Δn = ne - no is the birefringence characteristic of the nematic liquid crystal, which is the difference between the long-axis refractive index (ne) and the short-axis refractive index (no) of the molecule. Accordingly, the cholesteric liquid crystal 140 operates as a circular polarizer in a wavelength region (PBG: Photonic Band Gap) where Bragg reflection occurs. In addition, the wavelength band reflected by the circular polarizer 100 may be adjusted according to the concentration of the chiral material. In addition, the circular polarization range PBG of the circular polarization element 100 may be adjusted by changing the difference (Δn = ne - no) between the major axis refractive index ne and the minor axis refractive index no of the nematic liquid crystal molecules. The circular polarizer 100 according to the present disclosure may be used in an ultraviolet (UltraViolet: UV), visible light (VIS), or infrared (InfraRed: IR) band depending on the concentration of the chiral material. In some cases, the circular polarizer 100 may use not only a nematic liquid crystal, but also a smectic liquid crystal and an inorganic material having a spiral structure.

Meanwhile, the cholesteric liquid crystal 140 may include both general liquid crystals and liquid crystals that can be polymerized by ultraviolet rays or heat. Cholesteric liquid crystals that can be polymerized by Ultra Violet (UV) or heat can also be manufactured through a spin coating process.

2A and 2B are diagrams for explaining right-circularly polarized light and left-circularly polarized light according to an embodiment of the present disclosure;

Referring to FIG. 2A , a right-circular polarization device 100a is disclosed. The cholesteric liquid crystal of the right-circular polarizer 100a includes a left-handed chiral material. Due to the levorotatory chiral material, the cholesteric liquid crystal molecules are arranged in a counterclockwise spiral. And, the cholesteric liquid crystal including the left-handed chiral material reflects left-circularly polarized light. When the circularly polarized light element includes a cholesteric liquid crystal containing a left-handed chiral material, it may operate as the right-circularly polarized light 100a that reflects the left-circularly polarized light. For example, the levorotatory chiral material may be an S-811 chiral dopant mixture.

That is, when unpolarized light or linearly polarized light is incident on the right circularly polarized light 100a, the right circularly polarized light 100a reflects the left circularly polarized light within a predetermined wavelength range and transmits the right circularly polarized light. In various embodiments of the circular polarizer to be described below, the cholesteric liquid crystal may include a left-handed chiral material. In addition, the circular polarizing element including the left-handed chiral material may operate as the right circularly polarizing element 100a.

Referring to FIG. 2B , a left circular polarization device 100b is disclosed. The cholesteric liquid crystal of the left circular polarizer 100b includes a preferential chiral material. Due to the preferential chiral material, the cholesteric liquid crystal molecules are arranged in a clockwise spiral. And, the cholesteric liquid crystal including the preferential chiral material reflects right-circularly polarized light. When the circularly polarized light element includes a cholesteric liquid crystal including a preferential chiral material, it may operate as a left circularly polarized light element 100b that reflects right-circularly polarized light. For example, the preferential chiral material may be an R-811 chiral dopant mixture.

That is, when unpolarized light or linearly polarized light is incident on the left circularly polarized light 100b, the left circularly polarized light 100b reflects the right circularly polarized light within a predetermined wavelength range and transmits the left circularly polarized light. In various embodiments of the circular polarizer to be described below, the cholesteric liquid crystal may include a preferential chiral material. In addition, the circular polarization element including the preferential chiral material may operate as the left circular polarization element 100b.

The chiral material arranges the nematic liquid crystal included in the cholesteric liquid crystal in a counterclockwise or clockwise spiral. The travel distance until the nematic liquid crystal rotates 360 degrees is 1 pitch (P), and the distance until the nematic liquid crystal rotates 180 degrees is 1/2P. Due to the boundary condition between the nematic liquid crystal and both substrates 110a and 110b, the nematic liquid crystal is arranged only in a direction parallel to the rubbing direction (eg, 180 degrees or 360 degrees) at a position in contact with the polyimide. Accordingly, the nematic liquid crystals arranged between both substrates 110a and 110b are always integer multiples of 1/2P. And, when the distance of one pitch is shortened, the circularly polarized PBG moves to a high frequency band, and when the distance of one pitch becomes longer, the circularly polarized PBG moves to a low frequency band. The circularly polarized light may mean that the left circularly polarized light is reflected and the right circularly polarized light passes through in the PBG. Alternatively, the circularly polarized element may mean that the right-circularly polarized light is reflected and the left-circularly-polarized light passes through in the PBG.

Since frequency and wavelength are in inverse proportion to each other, when the pitch distance is shortened, the circularly polarized PBG moves to a short wavelength band, and when the pitch distance is increased, it moves to a long wavelength band. That is, when the distance of the pitch of the nematic liquid crystal included in the cholesteric liquid crystal is changed, the circularly polarized PBG may be moved.

When the length of the pitch of the nematic liquid crystal continuously changes according to the position of one circular polarizing element 100, one circular polarizing element 100 continuously transmits light of various frequency bands in a circular shape according to the area where the light is incident. can be polarized.

Hereinafter, various embodiments of the circular polarizer will be described.

3 shows a CLC structure in which a pitch is continuously increased as the position of the cholesteric liquid crystal, which is the circular polarizer 100, is moved in the wedge direction (X-axis direction in FIG. 3) according to an embodiment of the present disclosure. . Such a structure may be implemented in the following embodiments. Depending on the position of the wedge cell, there are i) a method using a continuous change in concentration of a chiral molecule, ii) a method using photoisomerization of an azo dye molecule, and iii) a method using a temperature gradient.

Meanwhile, as shown in FIG. 3 , a CLC structure in which the pitch is continuously increased by including spacers 130a and 130b of different sizes in the circular polarizer 100 may be implemented. However, spacers 130a and 130b of different sizes may be used together with the above-described three embodiments for a more effective CLC structure of continuously increasing pitch.

Referring to FIG. 3 , a continuously tunable circular polarizer 100 is illustrated. As described above, the circular polarizer 100 includes a pair of substrates 110a and 110b, polyimide layers 120a and 120b coated on one surface of each of the pair of substrates, and spacers 130a and 130b. . Also, although the circular polarization device 100 including spacers of the same size has been described in FIG. 1 , the circular polarization device 100 may include spacers 130a and 130b of different sizes. As described above, a cholesteric liquid crystal in which a nematic liquid crystal and a chiral material are mixed may be included between the plurality of spacers 130a and 130b. The pitch 141 of the nematic liquid crystals around the first spacer 130a is shorter than the pitch 142 of the nematic liquid crystals around the second spacer 140b. Accordingly, when the position at which light passes through the circular polarization element 100 moves along the +X axis direction, the circularly polarized frequency band moves to the low frequency band, and the circularly polarized wavelength band moves to the long wavelength band.

4 is a view for explaining a continuously variable wavelength circular polarizer using a concentration difference of a chiral material according to an embodiment of the present disclosure. A first method for obtaining the continuously changing pitch structure of FIG. It is an explanatory drawing.

Referring to FIG. 4( a ), a diagram in which cholesteric liquid crystals having different chiral concentrations are filled is shown. The cholesteric liquid crystals 11 and 12 having different chiral concentrations may be half filled in the empty space of the spacer by the capillary principle. For example, the first cholesteric liquid crystal 11 having a relatively high chiral concentration is filled on the thin wedge empty cell side, and the second cholesteric liquid crystal 11 having a relatively low chiral concentration is filled on the thick wedge empty cell side. The steric liquid crystal 12 is filled. The chiral concentration of the discontinuous cholesteric liquid crystals 11 and 12 may form a continuous pitch change as shown in FIG. 3 after a certain time has elapsed due to the diffusion principle.

Referring to FIG. 4( b ), the cholesteric liquid crystal 13 in which the chiral concentration is continuously changed by diffusion is shown. As described above, after a certain period of time, the chiral concentration is continuously decreased from the left to the right of FIG. 4(b) . As described above, as the chiral concentration decreases, the length of one pitch increases, the circularly polarized frequency band moves to a low frequency band, and the circularly polarized wavelength moves to a long wavelength band. That is, when the circular polarizing device 100 includes the cholesteric liquid crystal 13 including a chiral material having a concentration gradient continuously changing in a predetermined direction, one circular polarizing device 100 is incident light. Circular polarization can be performed for various frequency bands of

Also, as described above, the circular polarizer 100 may include the cholesteric liquid crystal 13 including a chiral material having a concentration gradient continuously changing in a preset direction and spacers having different sizes. The circularly polarized frequency band of the circularly polarized element 100 may be continuously changed by chiral materials having different concentration gradients and spacers having different sizes. In addition, the cholesteric liquid crystal 130 including a chiral material of a continuously changing concentration gradient can be made by polymerizing it by applying UV (ultraviolet rays) or heat. The liquid crystal that can be polymerized by ultraviolet light may include RMS08-062, RMS08-061, RMS11-066 or RMS11-068. When the cholesteric liquid crystal is polymerized by ultraviolet rays or heat, the cholesteric liquid crystal having a continuously changing concentration gradient formed as shown in FIG. 3 can be maintained for a long time (several years or more).

It is a figure explaining an azo dye.

Referring to FIG. 5 , an azo dye that is changed to a trans-type or a cis-type according to light is shown. For example, the azo dye may be azobenzene. In general, the azo dye may exist in the trans form (1). And, when the azo dye is exposed to ultraviolet light, the trans-type azo dye may be transformed into the cis-type (2) in proportion to the intensity and exposure time of the ultraviolet light by photoisomerization. And, when the azo dye of the cis-type (2) is exposed to heat or visible light, the azo dye of the cis-type (2) may be transformed into the trans-type (1) by photoisomerization. The cholesteric liquid crystal may contain a certain amount of an azo dye. The azo dye may be trans-type (1). In addition, the circularly polarized frequency band of the circularly polarized element may be shifted by the azo dye transformed into the cis-type (2).

On the other hand, the cholesteric liquid crystal may include a molecule containing a stilbene group instead of an azo dye.

6 is a view for explaining a circular polarizer using an azo dye according to an embodiment of the present disclosure.

Referring to FIG. 6 , a circular polarizing element 100 including an azo dye is illustrated. The circular polarizer 100 may include a cholesteric liquid crystal to which an azo dye is added in a certain ratio. As described above, when the priority chiral material is included in the cholesteric liquid crystal, the circular polarizer 100 may be a left circular polarizer. Also, when the cholesteric liquid crystal contains a left-handed chiral material, the circularly polarized element 100 may be a right-handedly circularly polarized element.

And, when the cholesteric liquid crystal containing the azo dye is exposed to ultraviolet light, the azo dye included in the cholesteric liquid crystal may be transformed from a trans-type to a cis-type. And, the cholesteric liquid crystal may include a liquid crystal that can be polymerized by ultraviolet rays. In addition, the cholesteric liquid crystal may include a liquid crystal that can be polymerized by heat. For example, the liquid crystal that can be polymerized by ultraviolet light may include RMS08-062, RMS08-061, RMS11-066 or RMS11-068. When the cholesteric liquid crystal is polymerized by ultraviolet rays or heat, the circular polarization device 100 may be maintained in a cholesteric liquid crystal state including the azo dye modified in a cis form if it is not exposed to visible light or heat.

On the other hand, the liquid crystal that is not polymerized by ultraviolet rays or heat may be a general liquid crystal. When the cholesteric liquid crystal is a general liquid crystal, the circular polarizer 100 including the azo dye transformed into a cis-type by ultraviolet rays may further include a blocking layer for blocking ultraviolet rays or visible rays. Alternatively, when the cholesteric liquid crystal is a general liquid crystal, the circular polarizer 100 including the azo dye transformed into a cis-type by ultraviolet light may return to its original state by visible light. Accordingly, the wavelength region PBG that is circularly polarized using ultraviolet light and visible light may be actively used.

As an embodiment, the cholesteric liquid crystal may include 50 wt% of a nematic liquid crystal, 30 wt% of a chiral material, and 20 wt% of an azo dye. That is, in the cholesteric liquid crystal, the ratio of the chiral material to the total material may be 30 wt%. The azo dye included in the cholesteric liquid crystal is of the trans type, and the trans-type azo dye participates in the cholesteric helix together with the nematic liquid crystal, so the azo dye may affect the ratio of chiral substances. Cholesteric liquid crystals containing azo dyes can be exposed to ultraviolet light. And, the azo dye may be transformed into a cis form. However, the azo dye changed to the cis form by UV does not participate in the cholesteric helix structure together with the nematic liquid crystal and comes out of the helix structure, and as a result, the chiral material compared to the total material that makes the cholesteric liquid crystal spiral structure ratio will increase. When the ratio of the chiral material in the cholesteric liquid crystal increases, the optical band gap (PBG) moves to a short wavelength, and when the ratio of the chiral material decreases, the PBG moves to a long wavelength.

Azo pigments changed to cis form do not affect the proportion of chiral substances. That is, when all 20 wt% of the azo dye is transformed into a cis form, the azo dye is released from the formed helical structure of the cholesteric liquid crystal. Accordingly, the cholesteric liquid crystal contains about 62.5 wt% of the nematic liquid crystal and about 37.5 wt% of the chiral material. Accordingly, when the trans-type azo dye is transformed into the cis-type, the ratio of the chiral material of the cholesteric liquid crystal is changed, and the circularly polarized frequency band (PBG) has an effect of shifting to a shorter wavelength. In addition, the cholesteric liquid crystal may include an azo dye at a constant concentration corresponding to a frequency band in which circularly polarized light is polarized.

7 is a view for explaining a circular polarizer using a concentration difference of an azo dye according to an embodiment of the present disclosure.

Referring to FIG. 7 , a circular polarizing element 100 including an azo dye having a concentration gradient continuously changing in a preset direction is illustrated. The circular polarizer 100 may include a cholesteric liquid crystal, and the cholesteric liquid crystal may include an azo dye that is photoisomerized by ultraviolet light.

Two types of cholesteric liquid crystals having different concentrations of azo dyes may be prepared. In addition, the two types of cholesteric liquid crystals having different concentrations of the azo dye may be half filled in the empty space of the spacer by the capillary principle. For example, the first cholesteric liquid crystal may be a liquid crystal having a relatively high concentration of an azo dye, and the second cholesteric liquid crystal may be a liquid crystal having a relatively low concentration of an azo dye. The concentration of the azo dye of the discontinuous cholesteric liquid crystal may be continuously changed after a certain period of time due to the diffusion principle. As an embodiment, after a certain period of time, the concentration of the azo dye is continuously increased from one side to the other as shown in FIG. 7 .

The circular polarizer 100 in which the concentration of the azo dye continuously changes may be irradiated with ultraviolet rays. The azo dye included in the circular polarizer 100 may be transformed from a trans-type to a cis-type by ultraviolet light. In addition, the chiral concentration included in the circular polarizer 100 may also be relatively changed according to the continuously changing concentration of the azo dye. That is, according to the continuously changing chiral concentration, the distance of one pitch of the nematic liquid crystal included in the circular polarizer 100 may also be continuously changed. Accordingly, one circularly polarized light element 100 may perform circularly polarized light for various frequency bands of incident light.

On the other hand, the cholesteric liquid crystal containing the azo dye may be polymerized by heat or ultraviolet rays. Alternatively, the circularly polarizing element 100 including the azo dye may further include a film that blocks ultraviolet or visible light after the azo dye is transformed into a cis form. Also, as described above, the circular polarizer 100 may include spacers having different sizes.

8 is a method of manufacturing a circular polarizer capable of obtaining the continuously changing pitch structure of FIG. 3 by using an ND filter 150 in which the intensity of transmitted light is continuously variable according to an embodiment of the present disclosure; It is a drawing explaining the second method.

Referring to FIG. 8 , a circular polarizing element 100 including an azo dye is illustrated. The circular polarizer 100 may include a cholesteric liquid crystal to which an azo dye is added in a certain ratio. When the cholesteric liquid crystal containing an azo dye is exposed to left ultraviolet rays, the azo dye included in the cholesteric liquid crystal may be transformed from a trans-type to a cis-type. Even if the concentration of the azo dye included in the cholesteric liquid crystal is the same, the ratio of the azo dye that is transformed into a cis-type may vary depending on the intensity of ultraviolet rays or exposure time to the cholesteric liquid crystal. When the ratio of the azo dye transformed into the cis-type is different, the frequency band in which the cholesteric liquid crystal is circularly polarized may be different.

As shown in FIG. 8 , the circular polarizer 100 may be exposed to ultraviolet light through a neutral density (ND) filter 150 . The concentration of the ND filter 150 may be continuously changed in a predetermined direction. That is, the amount of ultraviolet light passing through the ND filter 150 may vary in a certain direction. As an embodiment, as shown in FIG. 8 , the density of the ND filter 150 may gradually increase along the Y-axis direction. Accordingly, even when uniform ultraviolet rays are irradiated to the circular polarizer 100 , the amount of ultraviolet rays passing through the ND filter 150 may gradually decrease along the Y-axis direction. In addition, the amount of the azo dye that is transformed into a cis-type may gradually decrease. Accordingly, in the circular polarization device 100 illustrated in FIG. 8 , a pitch gradient (or tilt, gradient) may be formed in the Y-axis direction. That is, in the circular polarizer 100, the ratio of chiral materials is continuously decreased along the +Y axis direction, the pitch distance is increased, the frequency band to be circularly polarized is moved to the low frequency band, and the wavelength band is moved to the long wavelength band. can That is, one circular polarizer 100 may circularly polarize light of various frequency bands according to an incident region of the light.

When the cholesteric liquid crystal is polymerized by ultraviolet rays or heat, the circular polarizer 100 may be maintained in a cholesteric liquid crystal state including a cis-formed azo dye. Alternatively, the circular polarizer 100 may further include a blocking layer that blocks ultraviolet or visible light.

Alternatively, the cholesteric liquid crystal including the azo dye of a preset concentration may be exposed so that the intensity of ultraviolet rays in a preset direction continuously changes according to the position of the device. Accordingly, the ratio of the photoisomerized azo dye included in the circular polarizing device 100 may be continuously changed in a predetermined direction of the device, and the pitch of the cholesteric liquid crystal may be continuously changed. In order to continuously change the intensity of ultraviolet rays in a preset direction according to the position of the device, an ND filter that continuously changes between UV of a certain intensity and the device may be used.

9 is a view for explaining a circular polarizer using heat according to an embodiment of the present disclosure.

Referring to FIG. 9 , a circular polarizing element 100 including a heater 160 and heater rings 161a and 161b on both substrates, respectively, is illustrated. The reflected frequency (or wavelength) band of the cholesteric liquid crystal may be changed according to a change in temperature. The pitch of the nematic liquid crystal included in the cholesteric liquid crystal may be changed in response to the supplied heat. That is, the circular polarization frequency of the cholesteric liquid crystal may be changed according to a change in temperature. The heater 160 may adjust the temperature of the heater ring (161a, 161b). And, the temperature of the heater ring (161a, 161b) can be changed by the heater (160). Heat supplied by the heater 160 may be transferred to the cholesteric liquid crystal through the heater rings 161a and 161b. And, as the temperature of the cholesteric liquid crystal changes, the reflected frequency band may be shifted. That is, one circularly polarized light element 100 can perform circularly polarized light for various frequency bands of incident light by controlling the temperature transmitted to the cholesteric liquid crystal using the heater 160 .

10 is a view for explaining a third method of manufacturing a circular polarizer capable of obtaining the continuously changing pitch structure of FIG. 3 using a temperature gradient according to an embodiment of the present disclosure.

Referring to FIG. 10 , a circular polarization element 100 including a first heater 160a and a second heater 160b is illustrated. The first heater 160a and the second heater 160b may supply heat of different temperatures to the circular polarizer 100 . For example, the first heater 160a may supply heat of a first temperature, and the second heater 160b may supply heat of a second temperature lower than the first temperature. The first heater 160a may be connected to one end of the substrate, and the second heater 160b may be connected to the other end of the substrate. That is, a temperature gradient may be formed in the circular polarizer 100 in a direction from one end to the other by a temperature difference between the first and second heaters 160a and 160b. As described above, the pitch of the cholesteric liquid crystal may change according to the temperature. And, the frequency band to be circularly polarized may vary according to the pitch. Accordingly, the circularly polarized frequency band of the circularly polarized element 100 may vary from one end in which the temperature gradient is formed to the other end.

In addition, the first heater 160a and the second heater 160b may be set to various temperatures depending on the purpose. In some cases, the first heater 160a and the second heater 160b may be set to the same temperature.

The circular polarizer 100 may further include a moving stage 20 that moves in a direction parallel to the direction in which the temperature gradient is formed. The movable body 20, including the light source, may be moved to a position where the incident light strikes the circular polarizing element 100 according to the movement of the movable body 20 . Although the movable body 20 has been described with reference to FIG. 10 , the movable body 20 may be included in another embodiment in which the frequency band in which the circularly polarized light is polarized according to the location of the light of one circular polarizing element 100 is changed.

11 is a view for explaining a wavelength tunable circular polarizer using an electric field according to an embodiment of the present disclosure.

Referring to FIG. 11 , the circular polarizer 100 to which the power is connected is illustrated. For example, when the substrate is made of ITO, the substrate may include cells that can be supplied with electricity. And, when an electric field is applied, the cholesteric liquid crystal can pass only circularly polarized light with respect to a wavelength within the optical band gap (reflection wavelength band of the cholesteric liquid crystal). The pitch of the cholesteric liquid crystal may be changed according to the magnitude of the supplied voltage. In addition, the frequency band in which circularly polarized light is circularly polarized according to the change of the pitch may be changed.

As described above, when the cholesteric liquid crystal includes a left-handed chiral material, the circular polarizer 100 may operate as a right-circular polarizer. In addition, when the cholesteric liquid crystal includes a preferential chiral material, the circular polarizer 100 may operate as a left circular polarizer.

As described above, according to various embodiments of the circular polarizing device 100 , one circular polarizing device 100 having a pitch slope that continuously changes according to a position emits light of various frequency bands according to an incident position of the light. It can also be circularly polarized. Accordingly, it is necessary to move the light source or the circular polarizer 100 so that light can be incident on various regions of the circular polarizer 100 .

As an embodiment of moving the light source, the circular polarizer 100 may include a movable body. As described above, the movable body includes a light source and may move from one end of the circular polarizing element 100 to the other end. According to the movement of the movable body, the light source may illuminate various areas of the circular polarizer 100 .

12 is a view for explaining a wavelength tunable circular polarizer using a rotator according to an embodiment of the present disclosure.

Referring to FIG. 12 , the rotator 30 in which the circular polarization element 100 is positioned is shown. The rotator 30 may be used for the purpose of changing the incident angle of light incident on the device or may be used for the purpose of simultaneously changing the incident angle and the incident position of light with respect to the device. The rotator 30 may rotate based on a central point (or a rotation axis). In addition, the circular polarizer 100 may be located at a point separated by a predetermined distance d from the center point of the rotator 30 . That is, when the position of the circular polarization element 100 is changed so that light can be incident on various regions of the circular polarization element 100 , the rotator 30 may be used instead of the movable body. Since the circular polarizer 100 is disposed a certain distance d from the central point, an axis passing through the diameter of the rotator 30 according to the rotation of the rotator 30 may pass through various regions of the circular polarizer 100 . That is, when the light source is positioned on the same axis as the diameter of the rotator 30 , the light source may illuminate various regions of the circular polarizing element 100 according to the rotation of the rotator 30 . Accordingly, the rotator 30 may be applied to various embodiments of the single circular polarizer 100 in which the pitch gradient is formed.

Up to now, various embodiments of the circular polarizer 100 have been described. Hereinafter, various filters including the circular polarizer 100 will be described.

13 to 19 are views for explaining a notch filter according to various embodiments of the present disclosure.

Referring to FIG. 13 , the notch filter of the first embodiment including the circular polarizer 100 is illustrated.

The notch filter includes a right-circular polarization element 100a and a left-circular polarization element 100b. And, the output waveform of the notch filter may be detected using a spectrophotometer. That is, a notch filter that blocks light transmission in a preset frequency band PBG may be implemented by combining one right-circular polarizing element 100a and one left-circular polarizing element 100b of a preset concentration.

As described above, the right-circular polarization element 100a includes a left-handed chiral material in a cholesteric liquid crystal. Accordingly, the right circularly polarized light element 100a has a characteristic of reflecting left circularly polarized light of a certain wavelength (or frequency) band and transmitting right circularly polarized light. In addition, the left-circular polarization element 100b includes a preferential chiral material in the cholesteric liquid crystal. Accordingly, the left circularly polarized light element 100b has a characteristic of reflecting the right circularly polarized light of a certain frequency band and transmitting the left circularly polarized light.

Referring to FIG. 13 , light 51 is output from the light source 200 . The light 51 output from the light source 200 may be unpolarized light (unpolarized light) or linearly polarized light. Unpolarized light and linearly polarized light consist of 50% right-circularly polarized light and 50% left-circularly polarized light, respectively.

The right circularly polarized light element 100a reflects left circularly polarized light of a specific wavelength PBG and transmits right circularly polarized light. Accordingly, the light 52 passing through the right circularly polarized element 100a may have a waveform from which the left circularly polarized light component is removed from the PBG. Light passing through the right-circular polarization element 100a arrives at the left-circular polarization element 100b.

The left circularly polarized light element 100b reflects the right circularly polarized light of the PBG. Accordingly, the light 53 passing through the left circularly polarized element 100b may have a waveform from which the right circularly polarized light component at a specific wavelength is removed. As described above, since the left circularly polarized light component in the PBG is removed from the right circularly polarized light element 100a and the right circularly polarized light component is removed again from the left circularly polarized light element 100b, the light 53 passing through the two polarizing elements is It is possible to have a waveform in which all wavelengths in the PBG are removed. Accordingly, the notch filter may be implemented using the right-circular polarization element 100a and the left-circular polarization element 100b. In addition, the notch filter may be implemented by changing the arrangement positions of the right-circular polarizing element 100a and the left-circularly polarizing element 100b. That is, the left-circular polarization element 100b is disposed first, so that light output from the light source 200 may pass through the left-circular polarization element 100b and then pass through the right-circular polarization element 100a. Various embodiments of the arrangement order of the right-circular polarization element 100a and the left-circular polarization element 100b may also be applied to various notch filters described below.

The notch filter may be implemented using the right-circular polarization element 100a and the left-circular polarization element 100b of the various embodiments described above.

14 shows a notch filter according to the second embodiment.

Referring to FIG. 14 , a notch filter implemented as a right-circular polarizing element 100a including a first rotator 30a and a left-circular polarizing element 100b including a second rotator 30b is illustrated. As the first rotator 30a and the second rotator 30b rotate, respectively, the PBG positions of the right and left circular polarization elements 100a and 100b can move to a shorter wavelength, respectively, and the changed rotation angle of the two circularly polarized elements is changed by changing the rotation angle. By adjusting the PBG positions to match, a tunable notch filter can be implemented. In this case, the right-circle and left-circular polarizers 100a and 100b each have a constant concentration of chiral molecules, and the rotational movement of the PBG can be clockwise or counterclockwise regardless of the rotational direction.

Also, in FIG. 14 , the right-circular polarizing element 100a and the left-circular polarizing element 100b may be circular polarizing elements each having a pitch gradient according to various methods. For example, the right-circular polarization element 100a and the left-circular polarization element 100b may include different spacers, and may be elements in which a gradient of a chiral material concentration is formed, and a gradient using photoisomerization of an azo dye. It may be an element in which is formed, or a pitch gradient using a temperature gradient may be formed. The right-circular polarization element 100a and the left-circular polarization element 100b may be elements in which only the properties of a chiral material are different and the gradients of the same and similar concentrations are formed.

The right-circular polarization element 100a and the left-circular polarization element 100b may be disposed in regions separated by a predetermined distance from the rotation axes of the first and second rotators 30a and 30b, respectively. In addition, the first and second rotators 30a and 30b may rotate at the same angle. In some cases, the first rotator 30a and the second rotator 30b may rotate at different angles. As an embodiment, the first and second rotators 30a and 30b may rotate from 0 degrees to close to 90 degrees. The light source 200 may be disposed on the same axis as the diameters of the first and second rotators 30a and 30b. Accordingly, the light output from the light source 200 may be irradiated to corresponding regions of the right-circular polarization element 100a and the left-circular polarization element 100b. Light passing through the left-circular polarization element 100a and the right-circular polarization element 100b may be detected through the spectrometer 300 .

Light output from the light source 200 may be irradiated to various regions of the right-circular polarization element 100a and the left-circular polarization element 100b according to the rotation of the first and second rotators 30a and 30b. The right-circular polarization element 100a and the left-circular polarization element 100b may reflect light of different wavelength (or frequency) bands according to a region to which light is irradiated by the pitch gradient. Accordingly, the notch filter shown in FIG. 14 may remove light of various wavelength bands according to rotation of the first and second rotators 30a and 30b.

The embodiment of the rotator may be applied to various notch filters.

15 shows a notch filter according to the third embodiment.

Referring to FIG. 15 , the notch filter may include a right-circular polarization element 100a and a left-circular polarization element 100b in which a gradient of a chiral concentration is formed. Also, the right-circular polarization element 100a and the left-circular polarization element 100b may include a first movable body 20a and a second movable body 20b, respectively. The first and second movable bodies 20a and 20b may respectively move the right-circular polarizing element 100a and the left-circular polarizing element 100b on which the gradient is formed. The first and second movable bodies 20a and 20b may move the same distance. In some cases, the first and second movable bodies 20a and 20b may move different distances from each other.

As the first and second movable bodies 20a and 20b move, the light output from the light source 200 may be irradiated onto various regions of the right-circular polarization element 100a and the left-circular polarization element 100b. Since the light output from the light source 200 is irradiated to various regions of the right-circular polarizing element 100a and the left-circular polarizing element on which the gradient is formed, the notch filter may remove light of various wavelength bands. Embodiments of the movable body may be applied to various notch filters.

16 shows a notch filter according to the fourth embodiment.

Referring to FIG. 16 , the notch filter may include a first heater 160a and a second heater 160b in a right-circular polarization element 100a and a left-circular polarization element 100b of a predetermined concentration. Alternatively, the notch filter may include the first movable body 20a and the second movable body 20b in the right-circular polarization element 100a and the left-circular polarization element 100b at a predetermined concentration.

The light source 200 outputs light. The first heater 160a may supply heat at a first temperature to one end of the right-circular polarization element 100a and the left-circular polarization element 100b. The second heater 160b may supply heat of a second temperature different from the first temperature to the other ends of the right-circular polarization element 100a and the left-circular polarization element 100b. As described above, the right-circular polarization element 100a and the left-circular polarization element 100b may have temperature gradients formed by heat of different temperatures supplied from the first heater 160a and the second heater 160b, respectively. In addition, the right-circular polarization element 100a and the left-circular polarization element 100b may reflect light components of various wavelengths according to an area to which light is irradiated.

The notch filter shown in FIG. 16 may adjust the wavelength band of the reflected light by adjusting the temperature of the heat supplied from the first heater 160a and the second heater 160b. Alternatively, the notch filter shown in FIG. 16 may include a first movable body 20a and a second movable body 20b. The first movable body 20a and the second movable body 20b may adjust the wavelength band of the reflected light by moving the right circularly polarizing element 100a and the left circularly polarizing element 100b by the same distance, respectively. Alternatively, the first movable body 20a and the second movable body 20b may individually control the right-circular polarization element 100a and the left-circular polarization element 100b, respectively, to adjust the wavelength band of the reflected light.

17 shows a notch filter according to the fifth embodiment.

Referring to FIG. 17 , the notch filter may include a right circularly polarizing element 100a and a left circularly polarizing element 100b including a certain azo dye. As described above, when UV light is irradiated to the right circularly polarized element 100a and the left circularly polarized element 100b including the azo dye, the PBG of each circularly polarized element can be moved toward a shorter wavelength, and the moved PBG position is the visible light (VIS). It can move back to the long wavelength when it is pinched. The concentration of the azo dye included in the right-circular polarizing element 100a and the left-circularly polarizing element 100b may be variously set according to the purpose of the notch filter.

Since the characteristics of the linear polarizer including the azo dye and the characteristics of the notch filter including the right-circular polarizing element 100a and the left-circular polarizing element 100b are the same as in the above-described example, a detailed description thereof will be omitted.

The cholesteric liquid crystals of the right-circular polarizing element 100a and the left-circularly polarizing element 100b may be polymerized by heat or ultraviolet rays. Alternatively, the right-circular polarization element 100a and the left-circular polarization element 100b may further include a blocking layer capable of blocking ultraviolet or visible light.

18 shows a notch filter according to the sixth embodiment.

Referring to FIG. 18 , a notch filter including a right-circular polarizing element 100a and a left-circular polarizing element 100b having a gradient formed according to the concentration of the azo dye converted into a cis-type is illustrated.

As an embodiment, each of the right-circular polarization element 100a and the left-circular polarization element 100b may include an azo dye having a uniform concentration and an ND filter having a constant concentration. The amount or intensity of ultraviolet rays projected to each region of the right-circular polarization element 100a and the left-circular polarization element 100b may vary by the ND filter. The ratio of the azo dye converted to the cis-type in each region may vary depending on the amount or intensity of ultraviolet rays. In addition, the wavelength of light reflected from each region of the right-circular polarizing element 100a and the left-circular polarizing element 100b may vary according to the ratio of the azo dye.

Since the characteristics of the linear polarizer including the azo dye and the characteristics of the notch filter including the right-circular polarizing element 100a and the left-circular polarizing element 100b are the same as those of the above-described example, a detailed description thereof will be omitted.

19 shows a notch filter according to the seventh embodiment.

Referring to FIG. 19 , the notch filter may include a heater 160 . The heater 160 may supply heat to each surface of the right-circular polarization element 100a and the left-circular polarization element 100b. As the temperature of the heater 160 is controlled, wavelengths of light reflected from the right-circular polarization element 100a and the left-circular polarization element 100b may vary.

Meanwhile, the notch filter may be implemented as one element.

20 and 21 are diagrams for explaining a method of implementing a notch filter according to another embodiment of the present disclosure.

Referring to FIG. 20( a ), the above-described circular polarizing element is illustrated. That is, the polyimide layers 120a and 120b are coated on one surface of each of the pair of substrates 110a and 110b. In addition, the polyimide layers 120a and 120b may be subjected to a rubbing treatment in some cases. Next, a cell is manufactured using the spacer 130 between the polyimide layers 120a and 120b, and a mixture of nematic liquid crystal and a chiral material (dopant) is injected. In an embodiment, the chiral material may be a levorotatory chiral material. When a levorotatory chiral material is injected into the cell, the nematic liquid crystal is arranged in a counterclockwise spiral. After the injection of the chiral material, when ultraviolet rays are irradiated, the cholesteric liquid crystal layer 140 is polymerized. One substrate 110b coated with the polyimide layer 120b of the polymerized circular polarizer is removed. Referring to FIG. 20(b) , a diagram in which one substrate 110b coated with the polyimide layer 120b of the circular polarizer is removed is shown. After one substrate 110b of the circular polarizer is removed, a cell is manufactured using the spacer 130a.

20( c ) shows a device including a new cell. A cell is manufactured using the substrate 110c coated with the polyimide layer 120c and a new spacer 130a. Then, a nematic liquid crystal and a chiral material are injected into the fabricated cell.

20( d ) shows a device having a two-layer structure having left-circle and right-circular polarization characteristics, each including a new cholesteric liquid crystal layer 140a by injecting a nematic liquid crystal and a chiral material into the manufactured cell. . As described above, when the left-handed chiral material is included in the cholesteric liquid crystal layer 140 of FIG. 20A , the new cholesteric liquid crystal layer 140a includes the right-handed chiral material. On the other hand, when the cholesteric liquid crystal layer 140 of FIG. 20(a) contains a right-handed chiral material, the new cholesteric liquid crystal layer 140a includes a left-handed chiral material. When a left-handed chiral material is included, light passing through the cholesteric liquid crystal layer has a right-circular polarization characteristic, and when a right-handed chiral material is included, the light passing through the cholesteric liquid crystal layer has left-circular polarization properties have That is, the manufacturing order of the cholesteric liquid crystal layer having the left circular polarization characteristic and the cholesteric liquid crystal layer having the right circular polarization characteristic may be changed. In addition, the concentration of injected chiral molecules may be adjusted to match the positions of the PBG in the existing cholesteric liquid crystal layer 140 and the new cholesteric liquid crystal layer 140a.

In some cases, the surface of the pair of substrates 110a and 110c on which the polyimide is not coated with respect to the incident light may be used as an anti-reflection coating. In addition, the cholesteric liquid crystal layers 140 and 140a used for manufacturing the notch filter may be a material that can be polymerized by ultraviolet rays or heat.

Also, the notch filter may be manufactured in other ways.

Referring to FIG. 21A , after the polyimide layer 120a is coated, the cholesteric liquid crystal layer 140b is spin-coated on the rubbing-treated substrate 110a. For example, the cholesteric liquid crystal layer 140b may include a preferential chiral material, and the cholesteric liquid crystal layer 140b has left-circular polarization characteristics. Since the cholesteric liquid crystal layer 140b is manufactured through the spin coating process, only one substrate 110a is used. Next, a heat treatment process is performed at about 100 degrees for about 1 minute, and after cooling at room temperature slowly to facilitate the formation of a cholesteric spiral structure, when UV rays are irradiated, the cholesteric liquid crystal layer 140b is polymerized. A new cholesteric liquid crystal layer 140c is spin-coated on the spin-coated cholesteric liquid crystal layer 140b, and is formed in the same manner as the existing cholesteric liquid crystal layer 140b.

21(b) shows a device in which a new cholesteric liquid crystal layer 140c is formed. When the previous cholesteric liquid crystal layer 140b includes a left-handed chiral material, the new cholesteric liquid crystal layer 140c includes a left-handed chiral material. The spin coating process is performed to form two cholesteric liquid crystal layers 140b and 140c on the device. A heat treatment process is performed at about 100 degrees for about 1 minute so that the new cholesteric liquid crystal layer 140c is well formed, and when the left ultraviolet ray is irradiated, the new cholesteric liquid crystal layer 140c is polymerized. In addition, the concentration of injected chiral molecules may be adjusted so that the positions of the PBGs match the existing cholesteric liquid crystal layer 140b and the new cholesteric liquid crystal layer 140c. In addition, the cholesteric liquid crystal layers 140b and 140c used for manufacturing the notch filter may be a material that can be polymerized by ultraviolet rays or heat.

22 shows a notch filter according to an eighth embodiment.

Referring to FIG. 22 , a notch filter 400 formed of one element is illustrated. As described above, the notch filter 400 includes a double layer of a right circularly polarized cholesteric liquid crystal and a left circularly polarized cholesteric liquid crystal. Light 56 is output from the light source 200 . The light 56 output from the light source 200 may be unpolarized light (unpolarized light) or linearly polarized light. The unpolarized light and the linearly polarized light consist of 50% right-circularly polarized light and 50% left-circularly polarized light, respectively. pass through the screen The right-circularly polarized cholesteric liquid crystal of the notch filter 400 reflects the left-circularly polarized light component in the PBG. In addition, the left circularly polarized cholesteric liquid crystal of the notch filter 400 reflects the right circularly polarized light component in the PBG. The PBG of the right circularly polarized cholesteric liquid crystal and the left circularly polarized cholesteric liquid crystal of the notch filter 400 are the same. Accordingly, the light 57 passing through the notch filter 400 may have a waveform in which all components of the PBG region are removed.

The waveform of the light 57 passing through the notch filter 400 may be detected using a spectrophotometer.

23 shows a notch filter according to the ninth embodiment.

Referring to FIG. 23 , the notch filter 400 disposed on the rotator 30a is shown. The notch filter 400 includes a right circularly polarized cholesteric liquid crystal and a left circularly polarized cholesteric liquid crystal. Light 56 is output from the light source 200 . As the rotator 30a rotates, the PBG position of the notch filter 400 may move to a shorter wavelength.

At this time, the right-circularly polarized cholesteric liquid crystal and the left-circularly polarized cholesteric liquid crystal in the notch filter 400 each have a constant concentration of chiral molecules, and the position movement of the PBG by rotation is clockwise or counterclockwise regardless of the rotation direction. It can be turned clockwise.

In addition, in FIG. 23 , the right-circularly polarized cholesteric liquid crystal and the left-circularly polarized cholesteric liquid crystal in the notch filter 400 may each have a pitch gradient according to various methods. For example, the right circularly polarized cholesteric liquid crystal and the left circularly polarized cholesteric liquid crystal may be devices in which a gradient of chiral material concentration is formed, may be devices in which a gradient using photoisomerization of an azo dye is formed, and a temperature gradient It is also possible to form a pitch gradient using The right-circularly polarized cholesteric liquid crystal and the left-circularly polarized cholesteric liquid crystal differ only in the properties of the chiral material, and gradients with the same concentration and similar concentration can be formed.

The notch filter 400 may be disposed in an area separated from the rotation axis of the rotator 30a by a predetermined distance. As an embodiment, the rotator 30a may rotate from -90 degrees to close to 90 degrees. The light source 200 may be disposed on the same axis as the diameter of the rotator 30a. Light passing through the notch filter 400 may be detected through the spectrometer 300 .

The light output from the light source 200 may be irradiated to various regions of the notch filter 400 according to the rotation of the rotator 30a. The notch filter 400 may reflect light of different wavelength (or frequency) bands according to an area to which light is irradiated by the gradient of the pitch. Accordingly, the notch filter 400 illustrated in FIG. 23 may remove light of various wavelength bands according to rotation of the rotator 30a.

24 is a diagram illustrating an output waveform of a notch filter according to an embodiment of the present disclosure.

24 , a waveform of a notch filter according to various embodiments is illustrated. 24 , one notch filter may remove various wavelengths of light according to various gradients formed in the right-circular polarizing element and the left-circularly polarizing element. For example, the waveform of the notch filter shown in FIG. 24 shows that light of continuous and various wavelengths from a wavelength of about 500 nm to a wavelength of about 730 nm can be removed.

So far, various embodiments of a notch filter using a linear polarizer have been described. As described above, the embodiment of the notch filter is not limited to the embodiment shown in the drawings. If a specific wavelength (or frequency) band can be removed using the various linear polarizers described above, a notch filter may be implemented by combining various linear polarizers.

Hereinafter, various embodiments of a band pass filter using a linear polarizer will be described.

25 to 38 are diagrams for explaining a band pass filter according to various embodiments of the present disclosure.

25 shows a band pass filter according to the first embodiment.

Referring to FIG. 25 , the band pass filter may include a beam splitter 180 and a left circular polarizer 100b. The light source 200 outputs light. The output light may be unpolarized light or linearly polarized light. Light output from the light source 200 may pass through the beam splitter 180 . The light passing through the beam splitter 180 reaches the left circular polarization element 100b. The left circularly polarized element 100b may reflect the right circularly polarized light of a specific wavelength band among the transmitted light. For example, the specific wavelength band may be between 490 nm and 510 nm. The right circularly polarized light reflected from the left circularly polarized element 100b may be reflected from the beam splitter 180 . Right circularly polarized light reflected from the beam splitter 180 is converted into left circularly polarized light. That is, the spectrometer 300 may detect only left-circularly polarized light having a wavelength band between 490 nm and 510 nm by the beam splitter 180 and the left-circular polarizer 100b among the light output from the light source 200 . That is, the filter shown in FIG. 25 is a band-pass filter that passes only light having a wavelength band between 490 nm and 510 nm.

Although the left circular polarization element 100b is used in FIG. 25 , a band pass filter may be implemented using the right circular polarization element 100a. When the band pass filter includes the right-circular polarization element 100a, the light output from the light source 200 passes through the beam splitter 180 to reach the right-circular polarization element 100a. The right-circular polarization element 100a may reflect left-circularly polarized light of a specific wavelength band. For example, the specific wavelength band may be between 490 nm and 510 nm. Left circularly polarized light reflected from the right circularly polarized light element 100a may be reflected from the beam splitter 180 . Left circularly polarized light reflected from the beam splitter 180 is converted into right circularly polarized light. That is, the spectrometer 300 may detect only right-circularly polarized light having a wavelength band between 490 nm and 510 nm by the beam splitter 180 and the right-circular polarization element 100a among the light output from the light source 200 . That is, the filter is a band-pass filter that passes only light having a wavelength band between 490 nm and 510 nm.

Meanwhile, an optical waveguide may be disposed instead of the beam splitter. That is, by reflecting or separating the light reflected from the right-circle (or left-circle) polarizer 100a by a beam splitter or an optical waveguide, a band pass filter that passes light of a specific wavelength band may be implemented.

26 shows a band pass filter according to the second embodiment.

Referring to FIG. 26 , the band pass filter may include an optical waveguide 190 . The light output from the light source 200 may pass through the optical waveguide 190 to reach the left circular polarization element 100b. The left-circularly polarized element 100b may reflect the right-circularly polarized light among the incident light. The reflected right-circularly polarized light may be totally reflected in the waveguide a countless number of times through a branch of the optical waveguide 190 and then output in an unpolarized state. A spectrometer may be located at the end of the branch. The spectrometer may detect light of a specific wavelength band output from the optical waveguide.

27 shows a band pass filter according to the third embodiment.

Referring to FIG. 27 , the band pass filter may include a left circularly polarizing element 100b and a right circularly polarizing element 100a. The light output from the light source 200 passes through the beam splitter 180 and arrives at the left circular polarizer 100b. Among the light reaching the left circularly polarizing element 100b, right circularly polarized light of a specific wavelength is reflected by the left circularly polarizing element 100b. For example, the specific wavelength may be between 483 nm and 516 nm. The reflected right circularly polarized light is reflected by the beam splitter 180 and is converted into left circularly polarized light. The light changed to the left circularly polarized light reaches the right circularly polarized element 100a.

Meanwhile, the polarized wavelength band of the left circularly polarizing element 100b may be different from the polarized wavelength band of the right circularly polarizing element 100a. For example, the polarization wavelength of the left-circular polarizing element 100b may be between 483 nm and 516 nm, and the polarization wavelength of the right-circular polarizing element 100a may be between 500 nm and 534 nm.

That is, the wavelength band of light reaching the right-circularly polarized element 100a is left-circularly polarized light between 483 nm and 516 nm. In addition, the right circularly polarized light element 100a reflects left circularly polarized light between 500 nm and 534 nm. Accordingly, the light passing through the right-circularly polarized light element 100a is left-circularly polarized light between 483 nm and 500 nm. Light passing through the right-circular polarization element 100a may be detected through the spectrometer 300 .

As described above, the position of the left circularly polarizing element 100b and the position of the right circularly polarizing element 100a may be changed. A band-pass filter capable of adjusting a band gap passing through the left-circular polarizing element 100b and the right-circular polarizing element 100a having different reflected wavelength bands may be implemented.

28 shows a band pass filter according to the fourth embodiment.

Referring to FIG. 28 , the band-pass filter may include a beam splitter 180 , a left-circular polarization element 100b , and a right-circular polarization element 100a. In FIG. 28 , the wavelength band reflected by the left-circular polarization element 100b and the right-circular polarization element 100a may be the same. For example, as shown in FIG. 28 , it is assumed that the reflected wavelength band is between 490 nm and 510 nm.

Light output from the light source 200 and passing through the beam splitter 180 arrives at the left circular polarizer 100b. Right-circularly polarized light between 490 nm and 510 nm is reflected, and the remaining light, including left-circularly polarized light between 490 nm and 510 nm, passes. And, left circularly polarized light between 490 nm and 510 nm is reflected by the right circularly polarized light element 100a. Then, the reflected left circularly polarized light passes through the left circularly polarized element 100b. Accordingly, light from the left-circular polarization element 100b to the beam splitter 180 may include both a left-circular polarization component and a right-circular polarization component. That is, light directed from the left circular polarization element 100b to the beam splitter 180 may be unpolarized light. The unpolarized light may be reflected from the beam splitter 180 .

A band-pass filter in which the left-circular polarization element 100b and the right-circular polarization element 100a are arranged side by side may pass light of a specific wavelength band including both a left-circular polarization component and a right-circular polarization component.

29 shows a band pass filter according to the fifth embodiment.

* Referring to FIG. 29 , the band pass filter may include a left circular polarizer 100b disposed on the movable body 20 . The basic operation process of the band pass filter is the same as described above. In the left circular polarization element 100b of FIG. 29, a pitch gradient is formed according to a position. Accordingly, in the left-circular polarization device 100b, the wavelength band in which the light output from the light source 200 reaches the device may vary in a reflected wavelength band. Accordingly, as the area of the left-circular polarization element 100b to which the light reaches by the movable body 20 changes, the wavelength band through which the light passes may also vary. Since the gradient-formed linear polarizer has also been described in detail above, a detailed description thereof will be omitted.

30 shows a band pass filter according to the sixth embodiment.

Referring to FIG. 30 , the band-pass filter may include a beam splitter 180 , a left-circular polarizing element 100b and a right-circular polarizing element 100a connected to the movable bodies 20a and 20b, respectively. As described above, since the pitch gradient is formed in the left-circular polarization element 100b and the right-circular polarization element 100a, light of various wavelength bands can be reflected according to a location where the light arrives. And, the movable body 20 can adjust the area of the polarizing element to which the light reaches.

Some components of light output from the light source 200 and passing through the beam splitter 180 are reflected by the left circular polarization element 100b. Some components of the reflected light have a specific wavelength band and have right-circular polarization characteristics. Then, the reflected right circularly polarized light is converted into left circularly polarized light by the beam splitter. Some components of the reversed left circularly polarized light are reflected by the right circularly polarized element 100a. Accordingly, only light of a specific wavelength band by the combination of the left-circular polarization element 100b and the right-circular polarization element 100a can pass through and be detected by the spectrometer 300 .

31 shows a band pass filter according to the seventh embodiment.

Referring to FIG. 31 , the band-pass filter may include a beam splitter 180 , a left-circular polarization element 100b and a right-circular polarization element 100a. As described above, when the left circularly polarizing element 100b and the right circularly polarizing element 100a are arranged side by side, the spectrometer 300 may detect unpolarized light of a specific wavelength band.

When the left-circular polarizing element 100b and the right-circular polarizing element 100a have a pitch gradient, the position at which light reaches by the movable bodies 20a and 20b of the left-circular polarizing element 100b and the right-circular polarizing element 100a can be adjusted. there is. In addition, various band gaps (pass bands) may be set by a combination of the left-circular polarization element 100b and the right-circular polarization element 100a. As described above, the band pass filter may be implemented as an optical waveguide instead of the beam splitter 180 .

32 shows a band pass filter according to an eighth embodiment.

Referring to FIG. 32 , the band pass filter may include two left-circular polarization elements 100b-1 and 100b-2 and two right-circular polarization elements 100a-1 and 100a-2. The first right-circular polarizing element 100a - 1 and the first left-circular polarizing element 100b - 1 located in the region where the light output from the light source 200 and passing through the beam splitter 180 reaches the left circle of a specific wavelength band, respectively. It can reflect polarized light and right circularly polarized light. Accordingly, light reflected from the first right-circular polarization element 100a - 1 and the first left-circular polarization element 100b - 1 toward the beam splitter 180 may be unpolarized light.

In addition, the second right-circular polarizing element 100a - 2 and the second left-circular polarizing element 100b - 2 positioned in a region to which the light reflected from the beam splitter 180 reaches may adjust a band gap (passage wavelength band). . For example, the circularly polarized wavelength band of the first right-circular polarizing element 100a-1 and the first left-circular polarizing element 100b-1 is between 480 nm and 510 nm, and the second right-circular polarizing element 100a-2 and the second right-circular polarizing element 100b-1 have a wavelength band between 480 nm and 510 nm. The circularly polarized wavelength band of the two-left circular polarizer 100b - 2 may be between 490 nm and 520 nm.

The light reflected from the first right-circular polarization element 100a-1 and the first left-circular polarization element 100b-1 is unpolarized light between 480 nm and 510 nm. And, when the reflected unpolarized light reaches the second right circularly polarized light 100a - 2 , only left circularly polarized light between 490 nm and 520 nm is reflected. Accordingly, unpolarized light having a wavelength range of 480 nm to 490 nm and right-circularly polarized light having a wavelength range of 490 nm to 510 nm may pass through the second right-circular polarization element 100a - 2 . In addition, the second left circularly polarized light element 100b - 2 reflects only the right circularly polarized light between 490 nm and 520 nm. Accordingly, unpolarized light having a wavelength range of 480 nm to 490 nm may pass through the second left circular polarization element 100b - 2 and may be detected by the spectrometer 300 .

As described above, the band pass filter may include an optical waveguide instead of the beam splitter 180 .

33 shows a band pass filter according to the ninth embodiment.

Referring to FIG. 33 , the band pass filter includes two right-circular polarizing elements 100a-1 and 100a-2, two left-circular polarizing elements 100b-1 and 100b-2, and four heaters 160a, 160b, 160c, 160d). The four heaters 160a, 160d, 160c, and 160d are respectively applied to the first and second right-circular polarizing elements 100a-1 and 100a-2 and the first and second left-circular polarizing elements 100b-1 and 100b-2, respectively. heat can be supplied. The wavelength band of the light reflected by the first right-circular polarization element 100a - 1 and the first left-circular polarization element 100b - 1 may be the same. Also, the wavelength band of light reflected by the second right-circular polarization element 100a - 2 and the second left-circular polarization element 100b - 2 may be the same. Each of the heaters 160a, 160b, 160c, and 160d may be set to the same temperature or may be set to different temperatures. Depending on the temperature of the heat supplied from each of the heaters 160a, 160b, 160c, and 160d, the wavelength bands of the right-circular polarization filters 100a-1 and 100a-2 and the left-circular polarization filters 100b-1 and 100b-2 are circularly polarized. may vary.

The first right-circular polarization element 100a-1 and the first left-circular polarization element 100b-1 reflect left-circularly polarized light and right-circularly polarized light, respectively, to reflect unpolarized light of a specific pass wavelength band to the beam splitter 180. can In addition, the second right-circular polarization element 100a - 2 and the second left-circular polarization element 100b - 2 can adjust the pass wavelength band. Since the specific operation of the band pass filter is the same as described above, a detailed description thereof will be omitted.

34 shows a band pass filter according to the tenth embodiment.

Referring to FIG. 34 , the band pass filter may include right-circular polarizing elements 100a-1 and 100a-2 and left-circular polarizing elements 100b-1 and 100b-2 including a movable body. A pitch gradient may be formed in the right-circular polarization elements 100a-1 and 100a-2 and the left-circular polarization elements 100b-1 and 100b-2. For example, the pitch gradient may be formed using a temperature, a concentration of a chiral material, a concentration of an azo dye, a cis-type conversion ratio according to the amount or intensity of UV incident, a pitch distance according to the size of a spacer, and the like.

The gradients of the first right-circular polarization element 100a - 1 and the first left-circular polarization element 100b - 1 may be formed in the same ratio. Also, the gradients of the second right-circular polarization element 100a - 2 and the second left-circular polarization element 100b - 2 may be formed at the same ratio.

The first right-circular polarizing element 100a-1 may be disposed on the 1-1 movable body 20a-1, and the first left-circular polarizing device 100b-1 may be disposed on the 1-2-th movable body 20a-2. there is. The second right-circular polarizing element 100a-2 is disposed on the 2-1-th movable body 20b-1, and the second left-circular polarizing element 100b-2 is disposed on the 2-2-th movable body 20b-2. can be In addition, the 1-1 movable body 20a-1 and the 1-2 movable body 20a-2 may move the same distance. In this case, the 1-1 moving body 20a-1 and the 1-2 moving body 20a-2 use either one of the first right-circular polarizing element 100a-1 and the first left-circular polarizing element 100b by using one of the two moving bodies. -1) can be moved simultaneously. Also, the second-first movable body 20b-1 and the second-second movable body 20b-2 can move the same distance. At this time, the 2-1-th movable body 20b-1 and the 2-2 movable body 20b-2 use one of the two movable bodies to form the second right-circular polarizing element 100a-2 and the second left-circular polarizing element 100b. -2) can be moved simultaneously.

As described above, the first right-circular polarization element 100a-1 and the first left-circular polarization element 100b-1 reflect left-circularly polarized light and right-circularly polarized light, respectively, and emit unpolarized light of a specific pass wavelength band through a beam splitter ( 180) can be reflected. In addition, the second right-circular polarization element 100a - 2 and the second left-circular polarization element 100b - 2 can adjust the pass wavelength band. Since the specific operation of the band pass filter is the same as described above, a detailed description thereof will be omitted.

Meanwhile, the band-pass filter may include a rotator instead of a moving body, and may include an optical waveguide instead of the beam splitter 180 .

Meanwhile, the tunable bandpass filter of the various embodiments described above may be used as a monochromator, a tunable mirror, or a spectrophotometer device including a detector.

35 shows a band pass filter according to an eleventh embodiment.

Referring to FIG. 35 , the band pass filter may include a beam splitter 180 and a notch filter 400 including two layers of a left circle and a right circle polarizer. The light source 200 outputs light. The output light may be unpolarized light or linearly polarized light. Light output from the light source 200 may pass through the beam splitter 180 . The light passing through the beam splitter 180 reaches the notch filter 400 . The notch filter 400 may reflect light of a specific wavelength band (PBG) among the reached light. Since the notch filter 400 includes a right circularly polarized cholesteric liquid crystal and a left circularly polarized cholesteric liquid crystal, the light reflected from the notch filter 400 has both a left circularly polarized component and a right circularly polarized component. For example, the specific wavelength band may be between 490 nm and 510 nm. Light reflected from the notch filter 400 may be reflected from the beam splitter 180 .

The spectrometer 300 may detect only light having a wavelength band of 490 nm to 510 nm among the light output from the light source 200 . That is, the filter shown in FIG. 35 is a band-pass filter that passes only light having a wavelength band between 490 nm and 510 nm.

Meanwhile, an optical waveguide may be disposed instead of the beam splitter. That is, by reflecting or separating the light reflected from the notch filter 400 by a beam splitter or an optical waveguide, a band pass filter that passes the light of the PBG region may be implemented.

36 shows a band pass filter according to the twelfth embodiment.

Referring to FIG. 36 , the band pass filter may include notch filters 400a and 400b having a two-layer structure of two left-circle and right-circle polarizers. The light output from the light source 200 passes through the beam splitter 180 to reach the first notch filter 400a. Light of a specific wavelength among the light reaching the first notch filter 400a is reflected by the first notch filter 400a. As described above, since the notch filter includes a right-circularly polarized cholesteric liquid crystal and a left-circularly polarized cholesteric liquid crystal, the light reflected from the notch filter has both a left-circularly polarized component and a right-circularly polarized component. For example, the specific wavelength may be between 483 nm and 516 nm. The reflected light is reflected by the beam splitter 180 and reaches the second notch filter 400b.

Meanwhile, the wavelength band reflected by the first notch filter 400a may be different from the wavelength band reflected by the second notch filter 400b. For example, the wavelength band reflected by the first notch filter 400a may be between 483 nm and 516 nm, and the wavelength band reflected by the second notch filter 400b may be between 500 nm and 534 nm.

That is, the wavelength band of the light reaching the second notch filter 400b is between 483 nm and 516 nm. In addition, the second notch filter 400b reflects light between 500 nm and 534 nm. Accordingly, the light passing through the second notch filter 400b is between 483 nm and 500 nm. Light passing through the second notch filter 400b may be detected through the spectrometer 300 . A band pass filter capable of adjusting a band gap passing through the first notch filter 400a and the second notch filter 400b having different reflected wavelength bands may be implemented.

37 shows a band pass filter according to the thirteenth embodiment.

Referring to FIG. 37 , there is shown a band pass filter in which notch filters 400a and 400b having two pitch gradients are arranged in line with the light source 200 . In this case, the light source 200 may be a light source in a narrow wavelength region (eg, a 450 nm to 550 nm region) or a light source in a wide wavelength region. In this case, in the case of a light source of a wide wavelength region, a filter that passes only light of a specific wavelength region may be used. For example, a fluorescence dichroic filter 50 (passing only light of a specific wavelength region, for example, only light of 450 nm to 550 nm) may be disposed next to the light source to block unwanted light of a specific wavelength region from the light source. The first notch filter 400a and the second notch filter 400b may include a first movable body 20a and a second movable body 20b, respectively. In addition, the light output from the light source 200 according to the movement of the respective movable bodies 20a and 20b is irradiated to various regions of the first notch filter 400a and the second notch filter 400b, so that the first notch filter ( 400a) and the second notch filter 400b may reflect light from different PBG regions. For example, the first notch filter 400a moves the first movable body 20a to a position that reflects light 61 in a wavelength band of 420 nm to 500 nm, and the second notch filter 400b has a wavelength band of 510 nm The second movable body 20b may be moved so as to reflect the light 63 between 590 nm and 590 nm.

Light output from the light source 200 passes through the fluorescence dichroic filter 50 (only light of 450 nm to 550 nm passes). Light in the 450 nm to 550 nm region passing through the fluorescence dichroic filter reaches the first notch filter 400a. Accordingly, the light passing through the first notch filter 400a is light from which a component in a wavelength band of 420 nm to 500 nm is removed. Light between 500 nm and 550 nm passing through the first notch filter 400a arrives at the second notch filter 400b. In addition, the second notch filter 400b removes light in a wavelength band of 510 nm to 590 nm. Accordingly, the light passing through the second notch filter 400b may include the component 63 in the wavelength band of 500 nm to 510 nm. The filter including the movable body may operate as a tunable band-pass filter having a bandwidth of 10 nm in the range of 450 nm to 550 nm by moving the first movable body 20a and the second movable body 20b.

38 shows a band pass filter according to the fourteenth embodiment.

Referring to FIG. 38 , a band pass filter implemented as a first notch filter 400a including a first rotator 30a and a second notch filter 400b including a second rotator 30b is illustrated. The two notch filters 400a and 400b are arranged in line with the light source 200 . In this case, the light source may be a light source of a narrow wavelength region (eg, a region of 450 nm to 550 nm) or a light source of a wide wavelength region. In this case, in the case of a light source of a wide wavelength range, a filter that passes only light of a specific wavelength range may be used. For example, a fluorescence dichroic filter 50 (passing only light of a specific wavelength region, for example, only light of 450 nm to 550 nm) may be disposed next to the light source to block unwanted light of a specific wavelength region from the light source.

As the first rotator 30a and the second rotator 30b rotate respectively, the PBG positions of the first and second notch filters 400a and 400b may move to a shorter wavelength, respectively, and the rotation angle of the two notch filters may be changed by changing the rotation angle. By encouraging the changed PBG positions to be staggered, a tunable bandpass filter can be implemented. That is, since the PBG positions of the first and second notch filters 400a and 400b are crossed, a band-pass filter through which the light 68 of a specific wavelength region passes may be implemented. The position movement of the PBG by rotation can be rotated clockwise or counterclockwise regardless of the rotation direction.

Further, in FIG. 38 , the first notch filter 400a and the second notch filter 400b may be notch filters each having a pitch gradient according to various methods. In addition, the first notch filter 400a and the second notch filter 400b may be disposed in regions separated by a predetermined distance from the rotation axes of the first and second rotators 30a and 30b, respectively. In addition, the first and second rotators 30a and 30b may rotate at different angles.

In addition, in order to pass only light of a specific wavelength region after the light sources of FIGS. 37 and 38, other filters may be used instead of the fluorescence dichroic filter (passing only light of a specific wavelength region, for example, only light of 450 nm to 550 nm). . For example, a longpass filter (passes only light above a specific wavelength, for example, 400 nm or more) or a shortpass filter (passes only light below a specific wavelength, for example, 550 nm or less) can be appropriately included to block the unwanted wavelength region. there is.

39 is a diagram illustrating an output waveform of a band pass filter according to an embodiment of the present disclosure. As shown in FIG. 39 , one band-pass filter may pass various wavelength bands of light according to various gradients formed in the right-circular polarizing element and the left-circular polarizing element. For example, the waveform of the band-pass filter shown in FIG. 39 shows that light of continuous and various wavelength bands can pass from a wavelength of about 460 nm to a wavelength of about 750 nm.

Up to now, various embodiments of a band pass filter using a linear polarizer have been described. As described above, the embodiment of the band pass filter is not limited to the embodiment shown in the drawings. If a specific wavelength (or frequency) band can be passed using the various linear polarizers described above, a band pass filter may be implemented by combining the various linear polarizers.

On the other hand, in the case of an anti-reflection coating in a wide wavelength region, for example, 400 nm to 1000 nm, an intensity of 1% to 3% of light may pass through the light band of the notch filter depending on the quality of the anti-reflection coating. In the case of a low-power light source, in some cases, 1% to 3% of transmitted light can be neglected, but it may not be negligible in a precision optical sensor or device. The characteristics of the pass filter or the notch filter may be deteriorated. This is because a high-power laser has a large energy, so some components of light in a wavelength region that must be reflected pass through the polarizing element. Therefore, there is a need for a filter that not only provides a 0% transmission effect that completely blocks the light band of the notch filter, but also has 100% excellent characteristics even when light from a high-power laser is incident. For example, the high-power laser may mean a laser having a power of 30 mW or more of a CW laser. However, the above-described criterion is an example, and the criterion for classifying a high-power laser may vary.

Hereinafter, a notch filter and a band pass filter having excellent characteristics even when a high-power laser is used as a light source will be described. It goes without saying that the band pass filter and the notch filter described below can also be used in a light source of a low-power laser.

40 and 43 are views for explaining a method of implementing a filter including a plurality of cholesteric liquid crystal layers according to an embodiment of the present disclosure.

Referring to FIG. 40( a ), an embodiment of a filter is illustrated. One circular polarizer may have characteristics of a band-pass filter according to an angle of incident light. That is, the circular polarizer may be a filter.

The filter is a pair of substrates (110a, 110b), polyimide layers (120a, 120b) coated on one surface of each of the pair of substrates (110a, 110b), chiral injected between the polyimide layers (120a, 120b) and a cholesteric liquid crystal layer 140 including a material. The cholesteric liquid crystal layer 140 is polymerized by ultraviolet rays or heat. The cholesteric liquid crystal may be a material that can be polymerized by ultraviolet rays or heat. The polyimide layers 120a and 120b may be subjected to a rubbing treatment in some cases. In addition, the other surfaces of the pair of substrates 110a and 110b may be coated with anti-reflection (AR) layers 125a and 125b. That is, the anti-reflection layers 125a and 125b may be coated on the outer surface of the filter. One substrate 100b coated with the polyimide layer 120b of the filter is removed.

Referring to FIG. 40(b) , a view in which one substrate 110b coated with the polyimide layer 120b of the filter is removed is shown. After one substrate 110b of the filter is removed, a cell is manufactured using the spacer 130-1.

40(c) shows a device including a new cell. A cell is manufactured using the substrate 110b coated with the polyimide layer 120b and the new spacer 130-1. Then, a nematic liquid crystal and a chiral material are injected into the fabricated cell. After injection of the chiral material, the cholesteric liquid crystal layer is polymerized by ultraviolet rays or heat. The cholesteric liquid crystal may be a material that can be polymerized by ultraviolet rays or heat.

40(d) shows a filter having a two-layer structure having left-circle and right-circular polarization characteristics, each including a new cholesteric liquid crystal layer 140a by injecting a nematic liquid crystal and a chiral material into the manufactured cell. . As described above, when the left-handed chiral material is included in the cholesteric liquid crystal layer 140 of FIG. 40A , the new cholesteric liquid crystal layer 140a includes the right-handed chiral material. On the other hand, when the cholesteric liquid crystal layer 140 of FIG. 40(a) contains a right-handed chiral material, the new cholesteric liquid crystal layer 140a includes a left-handed chiral material. When a left-handed chiral material is included, the cholesteric liquid crystal layer has a right-circular polarization property, and when a right-handed chiral material is included, the cholesteric liquid crystal layer has a left-circular polarization property. The manufacturing order of the cholesteric liquid crystal layer having left-circular polarization characteristics and the cholesteric liquid crystal layer having right-circular polarization characteristics may be changed. In addition, the concentration of injected chiral molecules may be adjusted to match the positions of the PBG in the existing cholesteric liquid crystal layer 140 and the new cholesteric liquid crystal layer 140a. One substrate 100b coated with the polyimide layer 120b of the filter is removed.

Referring to FIG. 40(e), a view in which one substrate 110b coated with the polyimide layer 120b of the filter is removed is shown. After one substrate 110b of the filter is removed, an additional cell is manufactured using the spacer 130-2.

40(f) shows a device including an additional cell. A cell is manufactured using the substrate 110b coated with the polyimide layer 120b and a new spacer 130-2. Then, a nematic liquid crystal and a chiral material are injected into the fabricated cell. The cholesteric liquid crystal layer is polymerized by ultraviolet rays or heat.

FIG. 40(g) shows a filter including a new cholesteric liquid crystal layer 140b by injecting a nematic liquid crystal and a chiral material into the manufactured cell. As described above, one substrate 100b coated with the polyimide layer 120b of the filter is removed, and a nematic liquid crystal and a chiral material are injected into the cell between the spacers 130 - 3 . The cholesteric liquid crystal layer 140b is polymerized by ultraviolet rays or heat.

40(h) shows a filter having a four-layer structure having sequentially left-circle and right-circular polarization characteristics. That is, the filter having a four-layer structure includes a cholesteric liquid crystal layer 140 having a right-circular polarization characteristic from the bottom, a cholesteric liquid crystal layer 140a having a left-circular polarization characteristic, and a cholesteric liquid crystal layer 140b having a right-circular polarization characteristic. ), the cholesteric liquid crystal layer 140c having left-circular polarization characteristics may be disposed in the order. Alternatively, the cholesteric liquid crystal layer 140 having left-circular polarization characteristics, the cholesteric liquid crystal layer 140a having a right-circular polarization characteristic, the cholesteric liquid crystal layer 140b having left-circular polarization characteristics, and a right circular polarization characteristic They may be disposed in the order of the cholesteric liquid crystal layers 140c.

Also, the filter can be manufactured in other ways.

Referring to Figure 41 (a), an embodiment of the filter is shown. The filter is a pair of substrates (110a, 110b), polyimide layers (120a, 120b) coated on one surface of each of the pair of substrates (110a, 110b), chiral injected between the polyimide layers (120a, 120b) and a cholesteric liquid crystal layer 140 including a material. The chiral substance may be a levorotatory chiral substance or a dextrorotatory chiral substance. The cholesteric liquid crystal layer 140 may be formed by injecting a chiral dopant mixture between the spacers 130 and polymerizing it by ultraviolet rays or heat. The polyimide layers 120a and 120b may be subjected to a rubbing treatment in some cases. Each of the substrates 110a and 110b coated with the polyimide layers 120a and 120b is removed.

Referring to FIG. 41( b ), a filter from which each of the substrates 110a and 110b is removed is shown. When each of the substrates 110a and 110b is removed, a polymerized cholesteric liquid crystal layer 140 may be obtained.

Referring to FIG. 41( c ), a plurality of polymerized cholesteric liquid crystal layers in which the polymerized cholesteric liquid crystal layer is divided into several small pieces is shown. If the plurality of cholesteric liquid crystal layers 140-1, 140-2, and 140-3 obtained in the process of FIGS. 41 (a) and 41 (b) are cholesteric liquid crystal layers having right-circular polarization characteristics, the same In this way, a cholesteric liquid crystal layer having left-circular polarization properties can also be obtained. Alternatively, if the plurality of cholesteric liquid crystal layers 140-1, 140-2, and 140-3 obtained in the process of FIGS. 41 (a) and 41 (b) are cholesteric liquid crystal layers having left-circular polarization characteristics, the same In this way, a cholesteric liquid crystal layer having a right-circular polarization characteristic can also be obtained. For convenience of explanation, it is assumed that the plurality of cholesteric liquid crystal layers 140-1, 140-2, and 140-3 obtained in the process of FIGS. 41(a) and 41(b) are liquid crystal layers having right-circular polarization characteristics. do. That is, in FIG. 41(c) , a plurality of cholesteric liquid crystal layers 140-1, 140-2, and 140-3 having a right-circular polarization characteristic and a plurality of cholesteric liquid crystal layers 140a-1 having a left-circular polarization characteristic are shown. , 140a-2, 140a-3) are shown. Although three cholesteric liquid crystal layers each having different characteristics are illustrated in FIG. 41(c) , other numbers of cholesteric liquid crystal layers may be manufactured, such as two or four. In addition, the cholesteric liquid crystal layers 140-1, 140-2, 140-3, 140a-1, 140a-2, and 140a-3 may be manufactured to have a constant chiral concentration or to have a pitch gradient. The filter may be manufactured by alternately stacking cholesteric liquid crystal layers having different characteristics.

41(d) shows a filter manufactured by alternately stacking cholesteric liquid crystal layers having different characteristics. That is, the filter is sequentially between the pair of substrates 110a and 110b, the polyimide layers 120a and 120b coated on one surface of each of the pair of substrates 110a and 110b, and the polyimide layers 120a and 120b. The cholesteric liquid crystal layers 140-1 and 140-2 having a right-circular polarization characteristic, the cholesteric liquid crystal layers 140a-1 and 140a-2 having a left-circular polarization characteristic, and the cholesteric liquid crystal layer are alternately stacked with It may include spacers 130 , 130 - 1 , 130 - 2 , and 130 - 3 positioned in the . If necessary, the other surfaces of the substrates 110a and 110b may be coated with anti-reflection layers 125a and 1250b. Meanwhile, the filter may be manufactured by stacking a plurality of cholesteric liquid crystal layers having the same characteristics.

41(e) shows a filter in which a plurality of cholesteric liquid crystal layers having the same characteristics are stacked. As shown in FIG. 41(e), the filter may be manufactured by stacking a plurality of cholesteric liquid crystal layers 140-1, 140-2, 140-3, and 140-4 having right-circular polarization characteristics. In addition, the filter may be manufactured by stacking a plurality of cholesteric liquid crystal layers 140a-1, 140a-2, 140a-3, and 140a-4 having left-circular polarization characteristics. On the other hand, the cholesteric liquid crystal layer may be manufactured in another way.

Referring to FIG. 42(a-1), a cell manufactured in another manner is shown. The cell may be manufactured by spin-coating the cholesteric liquid crystal 140 including the chiral material on the polyimide layer 120a-coated substrate 110a. The cholesteric liquid crystal may be obtained by removing the substrate 110a coated with the polyimide layer 120a from the manufactured cell.

Referring to FIG. 42(b-1), the separated cholesteric liquid crystal 140 is shown. As described above, the cholesteric liquid crystal containing the left-handed chiral material has right-circular polarization characteristics with respect to transmitted light, and the cholesteric liquid crystal containing the right-handed chiral material has left-circular polarization characteristics with respect to the transmitted light. . A plurality of cholesteric liquid crystals having different characteristics may be manufactured by dividing the liquid crystal into several small pieces. In addition, as described in FIG. 41(d), a filter may be manufactured by sequentially and alternately stacking cholesteric liquid crystals having different characteristics, and as described in FIG. 41(e), a plurality of filters having the same characteristics A filter may be manufactured by laminating a cholesteric liquid crystal. On the other hand, the filter may be manufactured in other ways.

Referring to FIG. 43, the cholesteric liquid crystal divided into a plurality of pieces is shown. Similar to that described in FIG. 41(d), a filter may be manufactured by sequentially and alternately stacking pieces of cholesteric liquid crystal having different characteristics, and similarly as described in FIG. A filter may be manufactured by stacking pieces of cholesteric liquid crystal. When the cholesteric liquid crystal fragment was divided, the cholesteric liquid crystal was divided with the xy plane as the reference plane. A filter including a cholesteric liquid crystal layer can be manufactured by dividing one cholesteric liquid crystal into several and stacking them.

A filter including a plurality of cholesteric liquid crystal layers may have excellent filter performance even when high-power laser light is input. That is, the filter including the relatively thick cholesteric liquid crystal layer can effectively block (or reflect) light of a certain wavelength band even when high-power laser light is input. Various embodiments for implementing a notch filter and a band pass filter will be described below.

44 to 45 are views for explaining the structure of a filter including a plurality of cholesteric liquid crystal layers according to an embodiment of the present disclosure.

Referring to FIG. 44 , a filter including a plurality of circularly polarized elements is illustrated. The filter includes a plurality of right-circular polarization elements 100a and a plurality of left-circular polarization elements 100b. 44 shows two right-circular and left-circular polarizing elements 100a and 100b, respectively, but the filter may include various numbers of right-circular and left-circular polarizing elements 100a and 100b. An anti-reflection layer may be coated on the outermost surface of each of the right-circular and left-circular polarizers 100a and 100b. In addition, the cholesteric liquid crystal layer included in the right-circle and left-circular polarizers 100a and 100b may include a chiral material of a certain concentration or have a pitch gradient.

The right-circular polarization element 100a and the left-circular polarization element 100b of the filter may be alternately disposed at a preset interval. Accordingly, an air layer may exist between the right-circular polarization element 100a and the left-circular polarization element 100b. When the right-circular polarizing element 100a is disposed first, the circularly polarizing element 100a, the left-circular polarizing element 100b, the right-circular polarizing element 100a, and the left-circularly polarizing element 100b may be disposed in this order. . Alternatively, when the left circularly polarizing device 100b is disposed first, the left circularly polarizing device 100b, the right circularly polarizing device 100a, the left circularly polarizing device 100b, and the right circularly polarizing device 100a may be disposed.

Referring to FIG. 45 , another structure of a filter including a plurality of circular polarizing elements is illustrated.

The filter includes a plurality of right-circular polarization elements 100a and left-circular polarization elements 100b. The right-circular polarizing element 100a may include a substrate coated with a polyimide layer on one surface, a cholesteric liquid crystal layer positioned between the polyimide layers and including a left-handed chiral material, and the left-circular polarizing element 100b has one surface. The substrate on which the polyimide layer is coated, may include a cholesteric liquid crystal layer positioned between the polyimide layer and including a preferential chiral material. The right-circular polarization element 100a and the left-circular polarization element 100b may be alternately disposed, and an index matching material layer 145 may be interposed between the right-circular polarization element 100a and the left-circular polarization element 100b. The index matching material layer 145 is a material having substantially the same refractive index as that of the substrate (eg, glass). When light passes through the left-circular polarization element 100b and is incident on the next-positioned right-circular polarization element 100a, it may serve to prevent the light from being reflected. For example, the index matching material 145 may include a paste or index matching oil having no absorption for incident light.

Meanwhile, an anti-reflection layer may be coated on a surface other than the surface to which the index matching material layer 145 is attached of the right-circular polarization element 100a and the left-circular polarization element 100b. That is, the anti-reflective layer may be coated on the outermost both surfaces (a, b) of the filter.

So far, various structures of filters for high-power laser light sources have been described. Hereinafter, specific examples of the notch filter and the band pass filter will be described.

46 to 48 are views for explaining a notch filter including a plurality of cholesteric liquid crystals according to an embodiment of the present disclosure.

Referring to FIG. 46 , a notch filter according to an exemplary embodiment is illustrated. The notch filter may include a plurality of right-circular polarization elements 100a and left-circular polarization elements 100b. A notch filter including a plurality of right-circular polarization elements 100a and left-circular polarization elements 100b may be manufactured by the method and structure described with reference to FIGS. 40 to 45 . The plurality of right-circular polarization elements 100a and left-circular polarization elements 100b may include a chiral material having a constant concentration or may have a pitch gradient.

Light is output from the light source 200 . The light source 200 may include a high-power laser. The light output from the light source 200 may be unpolarized light or linearly polarized light. Unpolarized light and linearly polarized light consist of 50% right-circularly polarized light and 50% left-circularly polarized light, respectively.

The plurality of right circularly polarized light elements 100a reflect left circularly polarized light of a specific wavelength PBG and transmit right circularly polarized light. In addition, the left circularly polarized light element 100b reflects the right circularly polarized light of a specific wavelength and transmits the left circularly polarized light. That is, since the left circularly polarized light component in the PBG is removed from the right circularly polarized light element 100a and the right circularly polarized light component is removed from the left circularly polarized light element 100b, the light passing through the two polarizing elements is a waveform from which all wavelengths in the PBG are removed. can have Light passing through the notch filter may be detected through the spectrometer 300 .

Meanwhile, the notch filter may include a rotator. The rotator can rotate the notch filter. The notch filter may be disposed in an area separated by a predetermined distance (d) from the rotation axis of the rotator. The light source 200 may be disposed on the same axis as the diameter of the rotator, and the light source 200 and the spectrometer 300 may also be disposed on the same axis.

The rotator may change the angle of incidence of the light incident on the notch filter or the position of the notch filter on which the light is incident. Accordingly, since the angle of incidence of light or the position of the incident notch filter is changed according to the rotation of the rotator, the position of the PBG of the notch filter may be changed.

Meanwhile, the right-circular polarization element 100a and the left-circular polarization element 100b included in the notch filter may have a pitch gradient according to the various methods described above. The light output from the light source 200 may be irradiated to various regions of the right-circular polarization element 100a and the left-circular polarization element 100b according to the rotation of the rotator. The right-circular polarization element 100a and the left-circular polarization element 100b may reflect light of different wavelength (or frequency) bands according to a region to which light is irradiated by the pitch gradient. Accordingly, the notch filter may remove light of various wavelength bands according to the rotation of the rotator. That is, in the notch filter, the position of the PBG may change according to the rotation of the rotator. For example, when the notch filter contains a constant concentration of a chiral material, the bandwidth of the changeable wavelength may be about 100 nm to 150 nm, and when the notch filter has a pitch gradient, the bandwidth of the changeable wavelength may be about 400 nm to 500 nm there is.

Referring to FIG. 47 , a notch filter according to another embodiment is illustrated. The notch filter may include a plurality of right-circular polarization elements 100a and left-circular polarization elements 100b in which a gradient of a chiral concentration is formed. Also, the right-circular polarization element 100a and the left-circular polarization element 100b may include a first movable body 20a and a second movable body 20b, respectively. The first and second movable bodies 20a and 20b may respectively move the right-circular polarizing element 100a and the left-circular polarizing element 100b on which the gradient is formed. The first and second movable bodies 20a and 20b may move the same distance. In some cases, the first and second movable bodies 20a and 20b may move different distances from each other.

As the first and second movable bodies 20a and 20b move, the light output from the light source 200 may be irradiated onto various regions of the right-circular polarization element 100a and the left-circular polarization element 100b. Since the light output from the light source is irradiated to various regions of the right-circular polarizing element 100a and the left-circular polarizing element 100b in which the gradient is formed, the notch filter can remove light of various wavelength bands. That is, in the notch filter, the position of the PBG may change according to the movement of the first and second movable bodies 20a and 20b. The number of right-circular polarizing elements 100a and left-circularly polarizing elements 100b included in the notch filter may be variously set as needed.

Meanwhile, the notch filter may change the bandwidth by using two notch filter sets.

Referring to FIG. 48 , a notch filter system capable of changing a wavelength and a bandwidth at the same time is shown. The notch filter system may include a first set of notch filters and a second set of notch filters. Each notch filter set may include a plurality of right-circular polarizing elements 100a and 100a-1 and left-circular polarizing elements 100b and 100b-1 in which a chiral concentration gradient is formed. In addition, the right-circular polarization elements 100a and 100a-1 and the left-circular polarization elements 100b and 100b-1 may include a first movable body 20a and 20a-1 and a second movable body 20b and 20b-1, respectively. there is. The first and second movable bodies 20a, 20a-1, 20b, and 20b-1 may respectively move the right-circular polarizing elements 100a and 100a-1 and the left-circularly polarizing elements 100b and 100b-1 having gradients formed therein. . The movable bodies 20a, 20a-1, 20b, and 20b-1 of the first notch filter set and the second notch filter set may move the same distance. In some cases, the movable bodies 20a and 20b of the first notch filter set and the movable bodies 20a-1 and 20b-1 of the second notch filter set may move different distances from each other.

The light output from the light source 200 according to the movement of the first and second movable bodies 20a, 20a-1, 20b, and 20b-1 is the right-circular polarization element 100a, 100a-1 and the left-circular polarization element 100b, 100b. It can be applied to various areas of -1). As the light output from the light source is irradiated to various regions of the right-circular polarizing elements 100a and 100a-1 and the left-circular polarizing elements 100b and 100b-1 with gradients formed, the notch filter system can remove light of various wavelength bands. there is.

For example, the bandwidth of each of the first and second sets of notch filters may be approximately 50 nm. The first notch filter set may remove light having a bandwidth of 50 nm from 490 nm to 540 nm by the movable bodies 20a and 20b of the first notch filter set. At the same time, the second notch filter set can remove light having a bandwidth of 50 nm from 520 nm to 570 nm by the movable bodies 20a-1 and 20b-1 of the second notch filter set. Accordingly, light having a band width of 80 nm from 420 nm to 570 nm may be removed from the light passing through the first and second notch filter sets. According to the movement of the movable bodies 20a, 20b, 20a-1, and 20b-1 included in the first and second notch filter sets, the bandwidth may be varied from 50 nm to 100 nm. The number of notch filter sets may be variously set as needed.

So far, various embodiments for implementing the notch filter have been described. An embodiment of implementing a band pass filter will be described below.

49 to 54 are views for explaining a band pass filter including a plurality of cholesteric liquid crystals according to an embodiment of the present disclosure. The band pass filter shown in FIGS. 49 to 54 does not include a beam splitter. In addition, the plurality of right-circular polarization elements 100a and left-circular polarization elements 100b included in the band pass filter may include a chiral material of a certain concentration or have a pitch gradient. In addition, the number of right-circular polarization elements 100a and left-circular polarization elements 100b included in the band pass filter may be set in various ways according to the output power of the light source.

49 , a band pass filter according to an embodiment is illustrated. The band pass filter may include a plurality of right-circular polarizers 100a. A band pass filter including a plurality of right-circular polarizers 100a may also be manufactured using the method and structure described with reference to FIGS. 40 to 45 .

The light source 200 and the spectrometer 300 may be arranged to form a predetermined angle together with the band pass filter. As an embodiment, as shown in FIG. 49 , the angle formed by the light source 200 - the band pass filter - the spectrometer 300 may be any angle depending on the purpose. For example, the angle at which the light is incident is 45 It can also be Light output from the light source 200 may be incident on the band pass filter at a predetermined angle.

The light output from the light source 200 may be reflected by the band pass filter and detected by the spectrometer 300 . The light source may include a high-power laser. The light output from the light source 200 may be unpolarized light or linearly polarized light. Unpolarized light and linearly polarized light consist of 50% right-circularly polarized light and 50% left-circularly polarized light, respectively.

The plurality of right circularly polarized light elements 100a reflect left circularly polarized light of a specific wavelength PBG and transmit right circularly polarized light. Accordingly, since the band pass filter including the plurality of right circularly polarized light elements 100a reflects only the left circularly polarized light component in the PBG, the spectrometer 300 can detect a waveform through which only left circularly polarized light of a certain band is passed.

Meanwhile, a band pass filter including a plurality of left circular polarization elements may also be implemented. Since the band-pass filter including a plurality of left-circular polarization elements reflects only the right-circularly polarized light component in the PBG, the spectrometer 300 can detect a waveform through which only the right-circularly polarized light of a certain band is passed.

Referring to FIG. 50 , a band pass filter according to another embodiment is illustrated. The band pass filter may include a plurality of right-circular polarization elements 100a and left-circular polarization elements 100b. Each of the left-circle and right-circle polarization elements 100a and 100b may have a pitch of a certain concentration or may have a pitch gradient according to various methods of the above-described embodiment. Also, a band pass filter including a plurality of right-circular polarization elements 100a and left-circular polarization elements 100b may be manufactured by the method and structure described with reference to FIGS. 40 to 45 .

The light source 200 and the spectrometer 300 are arranged to form a predetermined angle together with the band-pass filter, so that light reflected by the band-pass filter may be detected by the spectrometer 300 . The light source may include a high-power laser. The plurality of right circularly polarized light elements 100a reflect left circularly polarized light of a specific wavelength PBG and transmit right circularly polarized light. The plurality of left circularly polarized light elements 100b reflect right circularly polarized light of a specific wavelength and transmit left circularly polarized light. That is, since the left circularly polarized light component in the PBG is reflected from the right circularly polarized light element 100a and the right circularly polarized light component is reflected from the left circularly polarized light element 100b, the light reflected from both polarization elements is a waveform that reflects all wavelengths in the PBG. can have That is, the spectrometer 300 may detect a waveform through which unpolarized light of a certain band is passed.

Meanwhile, the band-pass filter may include a movable body so that the positions of the optical band gaps between them coincide with each other, and the wavelength of the band-pass filter may be varied by moving the positions.

Referring to FIG. 51 , a band pass filter according to another embodiment is illustrated.

The band pass filter may include two right-circular polarizers 100a and 100a-1. The light output from the light source 200 reflects left-circularly polarized light of a specific wavelength by the first right-circularly polarized light element 100a. As an example, the specific wavelength may be between 490 nm and 540 nm. The reflected left circularly polarized light reaches the second right circularly polarized element 100a - 1 .

Meanwhile, the polarized wavelength band of the second right-circular polarizing element 100a - 1 may be different from that of the first right-circular polarizing element 100a. As an embodiment, the wavelength band of the second right-circular polarizer 100a - 1 may be between 510 nm and 560 nm. The wavelength band of light reaching the second right-circular polarization element 100a - 1 is left-circularly polarized light between 490 nm and 540 nm. In addition, the second right circularly polarized light element 100a-1 reflects left circularly polarized light between 510 nm and 560 nm. Accordingly, the light passing through the second right-circularly polarized light element 100a-1 is left-circularly polarized light between 490 nm and 510 nm. Accordingly, the band width of light may be reduced by the second right-circular polarization element 100a - 1 .

As described above, the band pass filter may include a left circular polarization element instead of a right circular polarization element. If the wavelength bands are the same, the light passing through the band pass filter including the left circular polarization element is right circularly polarized light between 490 nm and 510 nm.

Meanwhile, the first right-circular polarization element 100a and the second right-circular polarization element 100a-1 may include movable bodies 20a and 20a-1, respectively. When the first right-circular polarization element 100a and the second right-circular polarization element 100a - 1 are moved by the movable bodies 20a and 20a - 1 , the wavelength band detected by the spectrometer 300 may change. In addition, the band-pass filter may include the above-described rotator instead of the movable bodies 20a and 20a-1 to rotate the first right-circular polarizing element 100a.

52 , a band pass filter according to another embodiment is illustrated.

The band pass filter includes a reflector including a first right-circular polarizing element 100a and a first left-circular polarizing element 100b, and a second right-circular polarizing element 100a-1 and a second left-circular polarizing element 100b-1. It may include a band cutting unit. Each of the left-circle and right-circle polarizers 100a, 100b, 100a-1, and 100b-1 may have a pitch of a certain concentration or may have a pitch gradient according to the above-described various embodiments. The light output from the light source 200 reflects left-circularly polarized light of a specific wavelength by the first right-circular polarizing element 100a of the reflection unit, and reflects right-circularly polarized light of the same specific wavelength by the first left-circularly polarizing element 100b. make it Accordingly, the light reflected by the reflection unit is unpolarized light. As an example, the specific wavelength may be between 490 nm and 540 nm. The reflected unpolarized light reaches the band cut.

Meanwhile, the wavelength band polarized by the band cutting unit may be different from the wavelength band of the reflection unit. As an embodiment, the wavelength band of the second right-circular polarization element 100a - 1 and the second left-circular polarization element 100b - 1 may be between 510 nm and 560 nm. The wavelength band of the light reaching the band cutting part is unpolarized light between 490 nm and 540 nm. In addition, the second right circularly polarized light element 100a-1 of the band cutting unit reflects left circularly polarized light between 510 nm and 560 nm, and the second left circularly polarized light 100b-1 reflects right circularly polarized light between 510 nm and 560 nm. . Accordingly, the light passing through the second right-circular polarization element 100a-1 and the second left-circular polarization element 100b-1 is unpolarized light between 490 nm and 510 nm.

Meanwhile, the right-circular polarization elements 100a and 100a-1 and the left-circular polarization elements 100b and 100b-1 may include movable bodies 20a, 20a-1, 20b, and 20b-1, respectively. The first right-circular polarizing element 100a, the first left-circular polarizing element 100b, the second right-circular polarizing element 100a-1 and the second left-circular polarizing element are formed by the movable bodies 20a, 20b, 20a-1, and 20b-1. When (100b-1) is moved, the wavelength band detected by the spectrometer 300 may change. Also, the band pass filter may include the above-described rotator instead of the movable bodies 20a, 20a-1, 20b, and 20b-1 to rotate the first right-circular polarizing element 100a and the first left-circular polarizing element 100b.

Referring to FIG. 53 , a band pass filter according to another embodiment is illustrated. The band pass filter may include a reflector including the first right-circular polarizing element 100a and a band-cutting part including the second and third right-circular polarizing elements 100a-1 and 100a-2. Each of the right-circular polarizers 100a, 100a-1, and 100a-2 may have a pitch of a certain concentration or may have a pitch gradient according to various embodiments described above. The light output from the light source reflects left-circularly polarized light of a specific wavelength by the first right-circularly polarized light element 100a. As an example, the specific wavelength may be between 490 nm and 540 nm. The reflected left circularly polarized light arrives at the band cut.

Meanwhile, the polarized wavelength bands of the second and third right-circular polarizing elements 100a-1 and 100a-2 of the band cutting unit may be different from each other. As an embodiment, the wavelength band of the second right-circular polarizing element 100a-1 may be between 515 nm and 560 nm, and the wavelength band of the third right-circular polarizing element 100a-2 may be between 460 nm and 510 nm. The wavelength band of the light reaching the band cut is left circularly polarized light between 490 nm and 540 nm. In addition, the second right-circularly polarized light element 100a-1 reflects left-circularly polarized light between 515 nm and 560 nm. Accordingly, the light passing through the second right-circular polarization element 100a-1 is left-circularly polarized light between 490 nm and 515 nm. In addition, the third right circularly polarized light element 100a - 2 reflects left circularly polarized light between 460 nm and 510 nm. Accordingly, the light passing through the third right-circular polarization element 100a - 2 is left-circularly polarized light between 510 nm and 515 nm. An ideal band-pass filter can be implemented by removing both sides of the bandwidth at the band cutting part of the band-pass filter.

As described above, the band pass filter may include a plurality of left-circular polarization elements instead of the plurality of right-circular polarization elements. If the wavelength bands are the same, light passing through a band pass filter including a plurality of left circularly polarized light is right circularly polarized light between 510 nm and 515 nm.

Meanwhile, each of the right-circular polarization elements 100a, 100a-1, and 100a-2 may include movable bodies 20a, 20a-1, and 20a-2. When each of the right-circular polarizers 100a, 100a-1, and 100a-2 is properly moved by the movable bodies 20a, 20a-1, and 20a-2, the wavelength band detected by the spectrometer 300 may change. In addition, the band-pass filter may include the above-described rotator instead of the movable body 20a to rotate the first right-circular polarizing element 100a.

Referring to FIG. 54 , a band pass filter according to another embodiment is illustrated.

The band pass filter includes a reflector including a first right-circular polarizing element 100a and a first left-circular polarizing element 100b, and a second right-circular polarizing element 100a-1 and a second left-circular polarizing element 100b-1. a first band cutting unit, and a second band cutting unit including a third right-circular polarizing element 100a-2 and a third left-circular polarizing element 100b-2. Each of the right-circular polarizing elements 100a, 100a-1, and 100a-2 and the left-circular polarizing elements 100b, 100b-1, and 100b-2 has a pitch of a certain concentration or has a pitch gradient according to the various embodiments described above. can The light output from the light source 200 reflects left-circularly polarized light of a specific wavelength by the first right-circular polarizing element 100a of the reflection unit, and reflects right-circularly polarized light of the same specific wavelength by the first left-circular polarizing element 100b. make it Accordingly, the light reflected by the reflection unit is unpolarized light. As an example, the specific wavelength may be between 490 nm and 540 nm. The reflected unpolarized light arrives at the first bandcut.

Meanwhile, the wavelength band polarized by the first band cutting unit may be different from the wavelength band of the reflection unit. As an embodiment, the wavelength band of the second right-circular polarization element 100a - 1 and the second left-circular polarization element 100b - 1 may be between 515 nm and 560 nm. The wavelength band of the light reaching the first band cutting part is unpolarized light between 490 nm and 540 nm. In addition, the second right circularly polarized light element 100a-1 of the first band cutting unit reflects left circularly polarized light between 515 nm and 560 nm, and the second left circularly polarized light 100b-1 reflects right circularly polarized light between 515 nm and 560 nm. reflect Accordingly, the light passing through the first band cutting portion is unpolarized light between 490 nm and 515 nm. The light passing through the first band cutting section arrives at the second band cutting section.

Meanwhile, the wavelength band polarized by the second band cutting unit may be different from the wavelength band of the reflection unit and the first band cutting unit. As an embodiment, the wavelength band of the third right-circular polarization element 100a - 2 and the third left-circular polarization element 100b - 2 may be between 460 nm and 510 nm. The wavelength band of the light reaching the second band cutting part is unpolarized light between 490 nm and 515 nm. In addition, the third right-circular polarization element 100a-2 of the second band cutting unit reflects left-circularly polarized light between 460 nm and 510 nm, and the third left-circular polarization element 100b-2 reflects right-circularly polarized light between 460 nm and 510 nm. reflect Accordingly, the light passing through the second band cutting portion is unpolarized light between 510 nm and 515 nm.

On the other hand, each of the right-circular polarizing elements 100a, 100a-1, and 100a-2 and the left-circular polarizing elements 100b, 100b-1, 100b-2 has a movable body 20a, 20a-1, 20a-2, 20b, 20b- 1, 20b-2) may be included. Each of the polarizing elements 100a, 100a-1, 100a-2, 100b, 100b-1, 100b-2 is moved by the movable bodies 20a, 20a-1, 20a-2, 20b, 20b-1, and 20b-2. When properly moved, the wavelength band detected by the spectrometer 300 may be changed. In addition, the band pass filter may include the above-described rotator instead of the movable body 20a to rotate the first right-circular polarizing element 100a and the first left-circular polarizing element 100b.

Up to now, an embodiment for implementing a band pass filter has been described. A composite filter including the functions of a notch filter and a band pass filter will be described below.

55 is a view for explaining a composite filter including a band pass filter and a notch filter according to an embodiment of the present disclosure.

Referring to FIG. 55 , the composite filter includes first and second right-circular polarizing elements 100a and 100a-1, first and second left-circular polarizing elements 100b and 100b-1, and first and second switches 40a and 40b. ) may be included. The first and second switches 40a and 40b function to pass or block incident light according to on/off.

The light source 200 , the first spectrometer 300a , the first right-circular polarization element 100a , the second switch 40b , and the first left-circular polarization element 100b may be disposed on the same axis. In addition, the second spectrometer 300b, the second right-circular polarization element 100a-1, the first switch 40a, and the second left-circular polarization element 100b-1 may also be disposed on the same axis.

The first and second right-circular polarizing elements 100a and 100a-1 and the first and second left-circular polarizing elements 100b and 100b-1 reflect light of a specific wavelength region to be incident on the next element on the optical path. It may be arranged to form a predetermined angle with respect to the axis of the incident light. The second right-circular polarizing element 100a-1 is disposed at a position where the light reflected from the first right-circular polarizing element 100a can be incident, and the second left-circular polarizing element 100b-1 is the first left-circular polarizing element ( 100b) may be disposed at a position where the reflected light may be incident. The light output from the light source 200 may reach the first right-circular polarization element 100a. The first spectrometer 300a detects the light transmitted through the first left-circular polarization element 100b, and the second spectrometer 300b detects the light transmitted through the second left-circular polarization element 100b-1 and the second left-circular polarization element. The light reflected by (100b-1) is detected.

First, a case in which the first switch 40a is turned off and the second switch 40b is turned on will be described.

When the first switch 40a is turned off, light reflected from the second right-circular polarization element 100a-1 and passing through the second left-circular polarization element 100b-1 to reach the second spectrometer 300b is blocked. Accordingly, a first path through which light reaches the first spectrometer 300a through the light source 200, the first right-circular polarization element 100a, and the first left-circular polarization element 100b, and the light source 200 and the first right-circular polarization element 100b A second path through which light reaches the second spectrometer 300b through the device 100a, the first left-circular polarization element 100b, and the second left-circular polarization element 100b-1 is formed.

The first right-circularly polarized light element 100a reflects left-circularly polarized light of a specific wavelength band. If the specific wavelength band is between 490 nm and 540 nm, the light passing through the first right circularly polarized light element 100a may have a waveform from which a component of the left circularly polarized light in the 490 nm to 540 nm band is removed. The light passing through the first right-circular polarization element 100a arrives at the first left-circular polarization element 100b.

The first left circularly polarized light element 100b reflects right circularly polarized light of a specific wavelength band. If the specific wavelength band is between 490 nm and 540 nm, the light passing through the first left circularly polarized light element 100b may have a waveform from which the component of the right circularly polarized light in the 490 nm to 540 nm band is removed. Accordingly, light detected by the first spectrometer 300a through the first right-circular polarization element 100a and the first left-circular polarization element 100b may have a waveform from which all light components between 490 nm and 540 nm are removed. Accordingly, the first spectrometer 300a may detect a waveform of light that has passed through the notch filter.

In the second path, the light passing through the first right-circular polarization element 100a arrives at the first left-circular polarization element 100b with a waveform from which the component of the left-circular polarization light in the 490 nm to 540 nm band is removed. Only right-circularly polarized light between 490 nm and 540 nm is reflected by the first left-circular polarizing element 100b and directed toward the second left-circular polarizing element 100b-1. If the reflection wavelength band of the second left circular polarizer 100b-1 is between 460 nm and 510 nm, the light reflected from the second left circular polarizer 100b-1 reflects only the components of the right circularly polarized light in the 490 nm to 510 nm band . Accordingly, it is possible to reduce the bandwidth of the wavelength of the light reflected by the second left circular polarizer. The light reflected from the second left circular polarizer 100b - 1 is directed to the second spectrometer 300b. Accordingly, the second spectrometer 300b may detect the waveform of the light of the second path that has passed through the right-circular polarization and band-pass filter.

Next, a case in which the first switch 40a is turned on and the second switch 40b is turned off will be described.

When the second switch 40b is turned off, light reaching the first left circular polarization element 100b and the first spectrometer 300b is blocked. Accordingly, the light reaches the second spectrometer 300b through the light source 200, the first right-circular polarization element 100a, the second right-circular polarization element 100a-1, and the second left-circular polarization element 100b-1. A third path is formed.

In the case of the third path, the first right-circularly polarized light element 100a reflects left-circularly polarized light of a specific wavelength band. If the specific wavelength band is between 490 nm and 540 nm, the light reflected from the first right-circularly polarized light element 100a includes only left-circularly polarized light components in the 490 nm to 540 nm band. The second right-circular polarization element 100a - 1 may reflect left-circularly polarized light of a wavelength band different from that of the first right-circular polarization element 100a. When the wavelength band of the second right-circular polarization element 100a-1 is between 460 nm and 510 nm, the light reflected from the second right-circular polarization element 100a-1 includes only a component of the left-circular polarization light in a band of 490 nm to 510 nm. Accordingly, the bandwidth of the wavelength of the light reflected by the second right-circular polarization element 100a - 1 may be reduced. The light reflected from the second right-circular polarizing element 100a-1 reaches the second left-circular polarizing element 100b-1.

The second left-circular polarization element 100b - 1 may reflect right-circularly polarized light of a wavelength band different from that of the first left-circular polarization element 100b. Since the light incident on the second left-circular polarization element 100b-1 reflects only the components of the right-circular polarization light in the 490 nm to 510 nm band, it is reflected by the second right-circular polarization element 100a-1 and is reflected by the second left-circular polarization element 100b-1. ), left circularly polarized light is passed through without any influence. Accordingly, the light detected by the second spectrometer may have a waveform including only the left circularly polarized light component between 490 nm and 510 nm. Accordingly, the second spectrometer 300b may detect the waveform of the left circularly polarized third path light that has passed through the band pass filter.

Finally, a case in which both the first and second switches 40a and 40b are turned on will be described.

The light output from the light source 200 forms a first path passing through the first right-circular polarization element 100a and the first left-circular polarization element 100b. The waveform of the light passing through the first path is the same as when the above-described first switch 40a is turned off and the second switch 40b is turned off. Accordingly, the first spectrometer 300a may detect a waveform of light that has passed through the notch filter.

Then, the light output from the light source 200 forms a second path passing through the first right-circular polarization element 100a, the first left-circular polarization element 100b, and the second left-circular polarization element 100b-1. Accordingly, the second spectrometer 300b may detect the waveform of the light of the second path passing through the right-circularly polarized band pass filter.

And at the same time, the light output from the light source 200 forms a third path passing through the first right-circular polarization element 100a, the second right-circular polarization element 100a-1, and the second left-circular polarization element 100b-1. . The second spectrometer 300b may detect the waveform of the light of the third path passing through the left circularly polarized band pass filter. Therefore, in the second spectrometer 300b, the right circularly polarized light incident through the second path and the left circularly polarized light incident through the third path are combined and passed through an unpolarized band pass filter between 490 nm and 510 nm in the wavelength region. It can detect the light wave. Therefore, when both the first and second switches 40a and 40b are turned on, the first spectrometer 300a may detect a waveform of light that has passed through the notch filter, and at the same time, the second spectrometer 300b has unpolarized light. It is possible to detect the waveform of light that has passed through the band-pass filter.

The first and second right-circular polarization elements 100a and 100a - 1 and the first and second left-circular polarization elements 100b and 100b - 1 are respectively connected to the movable bodies 20a and 20b to move their positions. In addition, the cholesteric liquid crystal layers included in the first and second right-circular polarizing elements 100a and 100a-1 and the first and second left-circular polarizing elements 100b and 100b-1 include a chiral material of a certain concentration. or have a pitch gradient. Accordingly, the composite filter can change the position of the notch filter and the position and width of the band of the band pass filter by means of a movable body. Meanwhile, in the case of using only the first and second right-circular polarizing elements 100a and 100a-1 or using only the first and second left-circular polarizing elements 100b and 100b-1 in the configuration of the above-described composite filter, the transmissive band-pass filter can be implemented.

56 is a diagram illustrating an output waveform of a filter according to an embodiment of the present disclosure.

56(a) shows the waveform of the notch filter. As shown in FIG. 56(a), the notch filter can vary the wavelength and can almost completely remove the light component in the band region.

56(b) shows the waveform of the band pass filter. As shown in FIG. 56(b), the band-pass filter can vary the wavelength, and shows a waveform close to an ideal waveform.

100: circular polarizer
110a, 110b, 110c: substrate 120a, 120b, 120c: polyimide layer
130, 130a: spacer 140, 140a, 140b, 140c: cholesteric liquid crystal
150: ND filter 160: heater
170: power
200: light source 300: spectrometer
400: notch filter

Claims (7)

a pair of substrates extending in a horizontal direction;
a liquid crystal alignment layer coated on one surface of each of the pair of substrates;
a plurality of spacers disposed between the pair of substrates or the liquid crystal alignment layer;
a cholesteric liquid crystal (CLC) layer positioned in the space secured by the spacer and including either a left-handed chiral material or a right-handed chiral material;
a continuous pitch adjusting means for circularly polarizing light of a wavelength band that is continuously changed according to a region along the horizontal direction; including,
The chiral material arranges the nematic liquid crystals included in the cholesteric liquid crystal in a spiral, and the nematic liquid crystal is formed by the boundary condition between the cholesteric liquid crystal and the substrate formed by the liquid crystal alignment layer. It is arranged only at 180 degrees or 360 degrees at the position in contact with the alignment layer,
The plurality of spacers have different sizes along the horizontal direction,
The pair of substrates form wedge cells with different intervals continuously along the horizontal direction,
The continuous pitch adjusting means includes a power supply for supplying a voltage to the pair of substrates,
The pair of substrates includes a first substrate and a second substrate,
The power is respectively connected to the first substrate and the second substrate,
A first factor is a change in the intensity of a voltage applied by the power source or an electric field formed by the power source, a second factor is the wedge cell, and a third factor is a boundary condition between the cholesteric liquid crystal and the substrate. when doing,
A circular polarizing device in which a pitch gradient continuously changing along a horizontal direction of the substrate is formed in the cholesteric liquid crystal layer according to the first to third factors.
delete delete delete The method of claim 1,
a right-circular polarizing element including the left-handed chiral material in the cholesteric liquid crystal (CLC) layer and allowing light of a right-circle component to pass therethrough; and
A left-circular polarizing element including the preferential chiral material and allowing light of a left-circle component to pass therethrough is disposed adjacent to the cholesteric liquid crystal (CLC) layer;
Left-circle component light of a specific wavelength band reflected by the right-circular polarizer and
All of the right-circular component light of a specific wavelength band reflected by the left-circular polarizer is blocked,
The specific wavelength band of the right-circular polarizing element is continuously adjusted along the horizontal direction of the right-circular polarizing element by the continuous pitch adjusting means provided in the right-circular polarizing element;
The specific wavelength band of the left-circular polarizing element is continuously adjusted in a horizontal direction of the left-circular polarizing element by the continuous pitch adjusting means provided in the left-circular polarizing element.
The method of claim 1,
a right-circular polarizing element including the left-handed chiral material in the cholesteric liquid crystal (CLC) layer and allowing light of a right-circle component to pass therethrough; and
At least one of a left-circular polarizing element including the preferential chiral material in the cholesteric liquid crystal (CLC) layer and allowing light of a left-circle component to pass therethrough;
Left-circle component light of a specific wavelength band reflected by the right-circular polarizer and
A circular polarizing element for outputting at least one of the right-circular component light of a specific wavelength band reflected by the left-circular polarizing element.
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