JP7440845B2 - polarization imaging device - Google Patents

Description

Application of Article 30, Paragraph 2 of the Patent Act 43rd Optical Symposium Lecture Proceedings Published June 21, 2018 15 “Polarization Imaging System Using Liquid Crystal Polarization Diffraction Grating” October 2018 Applied Optics Vol., published on the 12th. 57, No. 30, pp. 8870-8875

The present invention relates to a polarization imaging device equipped with an anisotropic diffraction grating, and particularly to a polarization imaging device equipped with an anisotropic diffraction grating whose optical anisotropy is periodically modulated.

Various techniques for measuring the state of polarization have been reported for a long time.
The most typical polarization measurement methods are the rotating analyzer method and the rotating retarder method, which use rotating polarizers and wave plates. In these methods, the temporal waveform of light intensity according to the polarization state of incident light is observed while rotating a polarizing element. Furthermore, the obtained time waveform is subjected to Fourier analysis to restore Stokes parameter information. This method has a long history of research, and is characterized by high measurement accuracy as it has been subjected to various error reductions. However, on the other hand, since the information necessary to restore the Stokes parameters is acquired in multiple steps while rotating the polarizing element over time, this method is not suitable for objects to be measured whose polarization state changes over time. be. Considering the application of polarization measurement to medical devices, remote sensing, etc., it is extremely necessary to measure the polarization state of dynamic objects, and measurement of polarization spatial distribution in snapshots is required.

Prior to the present invention, there are several prior examples of a polarization measurement method using a polarization camera that makes it possible to measure the spatial distribution of polarization in a snapshot.
One example is to distribute wavelength plates or polarizers with their optical axes divided into four directions on a light receiving element array, and perform measurements equivalent to the rotating analyzer method or rotating retarder method per four pixels. (Non-patent Document 1 or 2). This method does not require a mechanical moving part to rotate the polarizing element, and the information necessary to obtain the Stokes parameters can be obtained with a single image acquisition, so static and snapshot imaging polarization measurement is possible. It becomes possible. However, it is necessary to precisely align the positions of the light receiving element array and the polarizing element array, which is not easy to manufacture. Furthermore, due to the discontinuity of the phase difference that occurs at the boundary of the polarizing element array, there is a possibility that diffracted light that is undesirable for measurement may occur.

Another example of prior research that enables snapshot polarization imaging is an imaging polarimeter using a polarization Savard plate that utilizes spatial carriers during polarization interference (Non-Patent Document 3).
This method does not suffer from the effects of diffraction as in the array elements described above. However, this method requires an expensive optical element such as a Savart plate, so it has the disadvantage of being costly.

T. Sato, T. Araki, Y. Sasaki, T. Tsuru, T. Tadokoro, and S. Kawakami, “Compact ellipsometer employing a static polarimeter module with arrayed polarizer and wave-plate elements,” Appl. Opt. 46, 4963 -4967 (2007). G. Myhre, W. L. Hsu, A. Peinado, C. LaCasse, N. Brock, R. A. Chipman, and S. Pau, “Liquid crystal polymer full-stokes division of focal plane polarimeter,” Opt. Express 20, 27393-27409 ( 2012). H. Luo, K. Oka, E. DeHoog, M. Kudenov, J. Schiewgerling, and E. L. Dereniak, “Compact and miniature snapshot imaging polarimeter,” Appl. Opt. 47, 4413-4417 (2008).

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a polarization imaging device that does not require mechanical moving parts and is capable of snapshot polarization imaging measurement, and in particular, a polarization imaging device that does not require highly accurate positioning of polarization elements. More particularly, it is an object of the present invention to provide a polarization imaging device that is relatively inexpensive in terms of cost.
Moreover, in addition to or in addition to the above-mentioned object, it is an object of the present invention to provide a polarization imaging device capable of performing polarization imaging measurement even if the object to be imaged is dynamic.

The present inventors discovered the following invention.
<1> Polarized light obtained by arranging, in order from the imaging target, a lens element, a first liquid crystal retarder, a second liquid crystal retarder, an anisotropic diffraction grating element whose optical anisotropy is periodically modulated, and a light receiving element. Imaging device.
<2> In <1> above, it is preferable that the first liquid crystal retarder and the second liquid crystal retarder each independently act as a variable wavelength plate.

<3> In <1> or <2> above, the first imaging is performed with the 11th retardation of the first liquid crystal retarder set to π/2 and the 21st retardation of the second liquid crystal retarder set to 0. ;
a second imaging in which the 12th retardation of the first liquid crystal retarder is 0 and the 22nd retardation of the second liquid crystal retarder is π/2; and a 13th retardation of the first liquid crystal retarder; 0 and the 23rd retardation of the second liquid crystal retarder is 0;
obtained,
The first Stokes parameter S ₁ from the first imaging,
The polarization spatial distribution is preferably measured by obtaining a second Stokes parameter S ₂ from the second imaging and a third Stokes parameter S ₃ from the third imaging.

<4> In any of the above <1> to <3>, the first imaging, second imaging, and third imaging are performed for 1000 milliseconds or less, preferably 600 milliseconds or less, and more preferably 350 milliseconds or less. , most preferably in 50 milliseconds or less.
<5> In <4> above, the first imaging, second imaging, and third imaging are performed for 1000 milliseconds or less, preferably 600 milliseconds or less, more preferably 350 milliseconds or less, and most preferably 50 milliseconds. It is preferable that the image be captured as follows, and that the polarization spatial distribution of the dynamic imaged object can be measured.

<6> In any one of <1> to <5> above, the anisotropic diffraction grating element has an anisotropic diffraction grating having a plurality of grating vectors with mutually different directions, and the grating vectors are at least different in direction. Preferably, the orientation or birefringence is periodically modulated.
<7> In any of <1> to <6> above, the anisotropic diffraction grating element spatially separates information on the Stokes parameter of the incident light according to the anisotropic orientation and birefringence distribution. , it is preferable to have an anisotropic diffraction grating for converting into intensity information.

<8> In any of the above <1> to <7>, the anisotropic diffraction grating element is at least one type selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. It is preferable to include an anisotropic diffraction grating having a photoreactive polymer film having a photoreactive side chain that causes the reaction.
<9> In any one of <1> to <8> above, the anisotropic diffraction grating element preferably includes an anisotropic diffraction grating made of a photoreactive polymer film.
<10> In any of the above <1> to <9>, the anisotropic diffraction grating element is
I) a first transparent substrate layer; and II) a first photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. The first photoreactive polymer film may include an anisotropic diffraction grating having a first photoreactive polymer film.

<11> In any of the above <1> to <10>, the anisotropic diffraction grating element
III) a second transparent base layer; and IV) a second photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking, and (A-2) photoisomerization. a second photoreactive polymer film having;
has
The above II) first photoreactive polymer film and the above IV) second photoreactive polymer film are arranged to face each other, and the above II) first film and the above IV) second film are arranged so as to face each other. It is preferable to include an anisotropic diffraction grating between which (B) a low molecular liquid crystal layer is arranged.

<12> In any of the above <8> to <11>, the photoreactive polymer film is subjected to interference exposure with desired polarized light to form an arbitrary diffraction pattern on the polymer thin film, thereby forming the polymer thin film. An anisotropic diffraction grating that spatially separates information on the Stokes parameter of incident light according to the anisotropic orientation and birefringence distribution formed in the polymer thin film and converts it into intensity information. It is better.
<13> In any of the above <1> to <12>, it is preferable that the anisotropic diffraction grating element has an anisotropic diffraction grating that has good diffraction efficiency for ±1st-order light.

<14> In any of the above <8> to <13>, the photoreactive polymer film has the following formulas (1) to (6).
(In the formula, A, B, and D each independently represent a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO -O- or -O-CO-CH=CH-;
S is an alkylene group having 1 to 12 carbon atoms, and the hydrogen atoms bonded to them may be replaced with halogen groups;
T is a single bond or an alkylene group having 1 to 12 carbon atoms, and the hydrogen atoms bonded thereto may be replaced with a halogen group;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
Y ₂ is a group selected from the group consisting of a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof; The hydrogen atoms bonded to are each independently -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. may be substituted with an alkyloxy group;
R represents a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, or has the same definition as Y ₁ ;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
Cou represents a coumarin-6-yl group or a coumarin-7-yl group, and the hydrogen atoms bonded to them are each independently -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH- May be substituted with CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyloxy group having 1 to 5 carbon atoms;
One of q1 and q2 is 1 and the other is 0;
q3 is 0 or 1;
P and Q are each independently selected from the group consisting of a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof. group; However, when X is -CH=CH-CO-O-, -O-CO-CH=CH-, P or Q on the side to which -CH=CH- is bonded is an aromatic ring, When the number of P's is 2 or more, the P's may be the same or different; when the number of Q's is 2 or more, the Q's may be the same or different;
l1 is 0 or 1;
l2 is an integer from 0 to 2;
When l1 and l2 are both 0, when T is a single bond, A also represents a single bond;
When l1 is 1, when T is a single bond, B also represents a single bond;
H and I are each independently a group selected from a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, and a combination thereof. )
It is preferable to have a photoreactive polymer having one kind of photoreactive side chain selected from the group consisting of:

<15> In any of the above <8> to <13>, the photoreactive polymer film has the following formulas (7) to (10).
(In the formula, A, B, and D each independently represent a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO -O- or -O-CO-CH=CH-;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
l represents an integer from 1 to 12;
m represents an integer of 0 to 2; m1 and m2 represent integers of 1 to 3;
n represents an integer from 0 to 12 (however, when n = 0, B is a single bond);
Y ₂ is a group selected from the group consisting of a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof; The hydrogen atoms bonded to are each independently -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. may be substituted with an alkyloxy group;
R represents a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, or has the same definition as Y ₁ )
It is preferable to have a photoreactive polymer having one kind of photoreactive side chain selected from the group consisting of:

<16> In any of the above <8> to <13>, the photoreactive polymer film has the following formulas (11) to (13).
(In the formula, A is each independently a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O- , or represents -O-CO-CH=CH-;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
l represents an integer from 1 to 12, m represents an integer from 0 to 2, m1 represents an integer from 1 to 3;
R represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or different substituents thereof; A group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (wherein R ₀ is a hydrogen atom or a carbon number of 1 to 5 ), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms (may be substituted with an oxy group, or represents a hydroxy group or an alkoxy group having 1 to 6 carbon atoms)
It is preferable to have a photoreactive polymer having any one type of photoreactive side chain selected from the group consisting of:

<17> In any of the above <8> to <13>, the photoreactive polymer film has the following formula (14) or (15)
(In the formula, A is each independently a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O-, or represents -O-CO-CH=CH-;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
l represents an integer from 1 to 12, m1 and m2 represent integers from 1 to 3)
It is preferable to have a photoreactive polymer having a photoreactive side chain represented by:

<18> In any of the above <8> to <13>, the photoreactive polymer film has the following formula (16) or (17) (wherein A is a single bond, -O-, -CH ₂ - , -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O-, or -O-CO-CH=CH-;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
l represents an integer from 1 to 12, m represents an integer from 0 to 2)
It is preferable to have a photoreactive polymer having a photoreactive side chain represented by:

<19> In any of the above <8> to <13>, the photoreactive polymer film has the following formula (18) or (19)
(In the formula, A and B each independently represent a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O -, or -O-CO-CH=CH-;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
One of q1 and q2 is 1 and the other is 0;
l represents an integer of 1 to 12, m1 and m2 represent integers of 1 to 3;
R ₁ is a hydrogen atom, -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms (represents oxy group)
It is preferable to have a photoreactive polymer having one kind of photosensitive side chain selected from the group consisting of:

<20> In any of the above <8> to <13>, the photoreactive polymer film has the following formula (20)
(In the formula, A is a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O-, or -O -CO-CH=CH-;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
It is preferable to have a photoreactive polymer having a photoreactive side chain (l represents an integer of 1 to 12, m represents an integer of 0 to 2).

ADVANTAGE OF THE INVENTION According to the present invention, there is provided a polarization imaging device capable of snapshot polarization imaging measurement without requiring mechanical moving parts, particularly a polarization imaging device that does not require highly accurate positioning of polarization elements, and more particularly in terms of cost. It is also possible to provide a relatively inexpensive polarization imaging device.
Further, according to the present invention, in addition to or in addition to the above-mentioned effects, it is possible to provide a polarization imaging device capable of performing polarization imaging measurement even if the object to be imaged is dynamic.

Figure 2 shows a schematic diagram of an OC grating with simple grating vectors. FIG. 3 is a diagram showing the dependence of the diffraction characteristics of an OC type diffraction grating on the amplitude ratio angle Ψ of incident light. FIG. 2 is a diagram illustrating the configuration of a polarization imaging device used in Examples. This is an image resulting from imaging measurement using a scarab beetle as a subject and using the polarization imaging device used in Examples.

<Polarization imaging device>
The present application provides a polarization imaging device including an anisotropic diffraction grating.
"Polarization," which is the property that the locus of the electric field vector of electromagnetic waves is biased, is widely used as a characteristic of electromagnetic waves. When electromagnetic waves interact with a substance (reflection, scattering, absorption, etc.), the polarization state of the electromagnetic wave changes, and this change in polarization contains various information specific to the substance. That is, by measuring the polarization characteristics of a subject, information unique to the substance can be investigated in a non-contact and non-destructive manner. The polarization imaging device of the present application can perform snapshot imaging measurement of the spatial distribution of Stokes parameters (parameters that describe the polarization state) of scattered light from a subject.

In the polarization imaging device of the present application, a lens element, a first liquid crystal retarder, a second liquid crystal retarder, an anisotropic diffraction grating element whose optical anisotropy is periodically modulated, and a light receiving element are arranged in order from the object to be imaged. It will be done.
Note that in the polarization imaging device of the present application, other elements than the above-mentioned elements may be arranged as desired.

<Anisotropic diffraction grating element>
The polarization imaging device of the present application includes an anisotropic diffraction grating element whose optical anisotropy is periodically modulated. The principle of Stokes parameter measurement using the anisotropic diffraction grating element will be explained below.
The polarization state of electromagnetic waves can be expressed by a Stokes vector (S ₀ , S ₁ , S ₂ , S ₃ ) consisting of four elements.
Here, S ₀ : Total light intensity, S ₁ : Difference between 0deg linear polarization component and 90deg linear polarization component, S ₂ : Difference between 45deg linear polarization component and -45deg linear polarization component, S ₃ : Right-handed circular polarization component. This means the difference in left-handed circularly polarized light components, and is called the Stokes parameter.
When the amplitude ratio angle and phase difference between the 0 degree linearly polarized light component and the 90 degree linearly polarized light component are respectively Ψ and Δ, each Stokes parameter is defined by the following equation (1).

By determining these four elements from the intensity information of the light reflected, scattered, and transmitted from the subject, it is possible to clarify the polarization characteristics of the subject.
The polarization imaging device of the present application is characterized by imaging and measuring these Stokes parameters by acquiring images three times. The principle of polarization detection of this device is based on an anisotropic diffraction grating element whose optical anisotropy is periodically modulated.
Before describing the configuration of the apparatus, etc., the diffraction characteristics of an anisotropic diffraction grating produced by polarization hologram recording will be described.

Generally, in a recording material having polarization sensitivity, the direction of optical anisotropy and the magnitude of birefringence are recorded according to the polarization direction and polarization ellipticity of irradiated polarized light. Now, let us consider that two right-handed circularly polarized lights and a left-handed circularly polarized light having the same amplitude are given a certain crossing angle to interfere with each other, and the resulting optical electric field is irradiated onto a polarized recording material (unless otherwise specified in this application, This case is called OC interference (Orthogonal circular polarization interference). In this case, assuming that the direction and magnitude of the induced anisotropy depend on the polarization direction and light intensity, the Jones matrix representing the induced anisotropy distribution is expressed by the following equation (2). Here, Δγ=πΔnd/λ, Δn is the maximum value of polarization-induced birefringence, d is the film thickness of the recording material, and λ is the wavelength of the diffracted light.

Furthermore, by expanding equation (2), we can obtain equation (3) below. From equation (3), when we calculate the intensity of the diffracted light for the incident polarized light given by equation (4), we can obtain equation (5) below. T ^OC _± expressed by is obtained.
Therefore, it can be seen that the intensity of the diffracted light of the anisotropic grating formed by OC recording by OC interference depends on the phase difference of the incident light. Hereinafter, for the sake of simplicity, this lattice will be referred to as an OC lattice.

As mentioned above, an anisotropic diffraction grating formed in a polarization recording material by polarization hologram recording exhibits diffraction characteristics that depend on the incident polarization state. Therefore, it becomes possible to spatially separate polarization information of incident light as intensity information.

It is preferable that the anisotropic diffraction grating has a high diffraction efficiency for ±1st-order light. In the OC grating, the ideal phase difference with the best diffraction efficiency for ±1st-order light can be found from the above equation (4).
Specifically, in the case of an OC grating, the diffraction efficiency is 5% or more, that is, the phase difference (δ = 2πΔnd/λ) is in the range of 0.448 + 2πm to 5.82 + 2πm (m: natural number), preferably 50% or more. Efficiency, that is, phase difference (δ = 2πΔnd/λ), is in the range of 1.57 + 2πm to 4.71 + 2πm (m: natural number), ideally 100% diffraction efficiency, that is, phase difference (δ = 2πΔnd/λ), is 3 .14+2πm (m: natural number) is preferable.

Anisotropic grating elements can be prepared as follows.
That is, the anisotropic diffraction grating element has a photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. It is preferable to include an anisotropic diffraction grating having a polymer film.
Further, it is preferable that the anisotropic diffraction grating element includes an anisotropic diffraction grating made of a photoreactive polymer film. In this case, it is necessary to improve the diffraction efficiency of the ±1st-order light obtained from the diffraction pattern formed on the photoreactive polymer film, so the photoreactive polymer used for the photoreactive polymer film is It is preferable to use a polymer that can induce a large phase difference, specifically, a phase difference in the range described above, by interference exposure with polarized light.

The anisotropic grating element is
I) a first transparent substrate layer; and II) a first photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. The first photoreactive polymer film may include an anisotropic diffraction grating having a first photoreactive polymer film.

In addition, the anisotropic diffraction grating element is
III) a second transparent base layer; and IV) a second photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking, and (A-2) photoisomerization. a second photoreactive polymer film having;
has
The above II) first photoreactive polymer film and the above IV) second photoreactive polymer film are arranged to face each other, and the above II) first film and the above IV) second film are arranged so as to face each other. It is preferable to include an anisotropic diffraction grating between which (B) a low molecular liquid crystal layer is arranged.

<<First and second transparent base layer>>
The first and second transparent base layers are made of transparent bases.
As the transparent substrate, for example, glass; plastic such as acrylic or polycarbonate; etc. can be used, although it depends on the characteristics used as the polarization imaging device. For example, the transparent substrate preferably has the property of transmitting polarized ultraviolet rays.

<<(B) Low molecular liquid crystal layer>>
Here, as the low-molecular liquid crystal contained in the low-molecular liquid crystal layer (B), nematic liquid crystal, ferroelectric liquid crystal, etc., which are conventionally used in liquid crystal display elements, etc. can be used.
Specifically, as low molecular liquid crystals, cyanobiphenyls such as 4-cyano-4'-n-pentylbiphenyl and 4-cyano-4'-n-feptyloxybiphenyl; cholesteryl esters such as cholesteryl acetate and cholesteryl benzoate; carbonate esters such as 4-carboxyphenylethyl carbonate and 4-carboxyphenyl-n-butyl carbonate; phenyl esters such as benzoic acid phenyl ester and phthalic acid biphenyl ester; benzylidene-2-naphthylamine, 4'- Schiff bases such as n-butoxybenzylidene-4-acetylaniline; benzidines such as N,N'-bisbenzylidenebenzidine and p-dianisalbenzidine; 4,4'-azoxydianisole, 4,4'- Examples include, but are not limited to, azoxybenzenes such as di-n-butoxy azoxybenzene; liquid crystals such as phenylcyclohexyl, terphenyl, and phenylbicyclohexyl as shown below; and the like.

Note that by subjecting the photoreactive polymer film described above to interference exposure with desired polarized light and forming an arbitrary diffraction pattern on the polymer thin film, information on the Stokes parameter of light incident on the polymer thin film can be obtained. It is preferable to use an anisotropic diffraction grating that is spatially separated according to the anisotropic orientation formed in the polymer thin film and the distribution of birefringence and converted into intensity information.

<<Photoreactive polymer film>>
The photoreactive polymer film described above has a photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. Preferably, it is formed with a polymer.
In this specification, photoreactivity refers to the property of causing either (A-1) photocrosslinking or (A-2) photoisomerization; and both reactions.
The photoreactive polymer preferably has (A-1) a side chain that causes a photocrosslinking reaction.

The photoreactive polymer is i) a polymer that exhibits liquid crystallinity in a predetermined temperature range and has a photoreactive side chain.
It is preferable that the photoreactive polymer ii) reacts with light in a wavelength range of 250 nm to 450 nm and exhibits liquid crystallinity in a temperature range of 50 to 300°C.
Preferably, the photoreactive polymer has iii) a photoreactive side chain that reacts with light in the wavelength range of 250 nm to 450 nm, especially polarized ultraviolet light.
The photoreactive polymer preferably has iv) a mesogenic group in order to exhibit liquid crystallinity in a temperature range of 50 to 300°C.

As described above, the photoreactive polymer has a photoreactive side chain that exhibits photoreactivity. The structure of the side chain is not particularly limited, but it has a structure that causes the reaction shown in (A-1) and/or (A-2) above, and (A-1) has a structure that causes a photocrosslinking reaction. is preferred. (A-1) A structure that causes a photocrosslinking reaction is preferable because the structure after the reaction can stably maintain the orientation of the photoreactive polymer for a long period of time even when exposed to external stress such as heat. .
It is preferable for the side chain structure of the photoreactive polymer to have a rigid mesogenic component because this stabilizes the alignment of the liquid crystal.

Examples of mesogenic components include, but are not limited to, biphenyl groups, terphenyl groups, phenylcyclohexyl groups, phenylbenzoate groups, and azobenzene groups.

The structure of the main chain of the photoreactive polymer includes, for example, hydrocarbons, radically polymerizable groups such as (meth)acrylate, itaconate, fumarate, maleate, α-methylene-γ-butyrolactone, styrene, vinyl, maleimide, norbornene, and At least one selected from the group consisting of siloxane can be mentioned, but is not limited thereto.
Furthermore, the side chain of the photoreactive polymer is preferably a side chain consisting of at least one of the following formulas (1) to (6).

In the formula, A, B, and D each independently represent a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO- Represents O- or -O-CO-CH=CH-;
S is an alkylene group having 1 to 12 carbon atoms, and the hydrogen atoms bonded to them may be replaced with halogen groups;
T is a single bond or an alkylene group having 1 to 12 carbon atoms, and the hydrogen atoms bonded thereto may be replaced with a halogen group;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
Y ₂ is a group selected from the group consisting of a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof; The hydrogen atoms bonded to are each independently -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. may be substituted with an alkyloxy group;
R represents a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, or has the same definition as Y ₁ ;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
Cou represents a coumarin-6-yl group or a coumarin-7-yl group, and the hydrogen atoms bonded to them are each independently -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH- May be substituted with CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyloxy group having 1 to 5 carbon atoms;
One of q1 and q2 is 1 and the other is 0;
q3 is 0 or 1;
P and Q are each independently selected from the group consisting of a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof. group; However, when X is -CH=CH-CO-O-, -O-CO-CH=CH-, P or Q on the side to which -CH=CH- is bonded is an aromatic ring, When the number of P's is 2 or more, the P's may be the same or different; when the number of Q's is 2 or more, the Q's may be the same or different;
l1 is 0 or 1;
l2 is an integer from 0 to 2;
When l1 and l2 are both 0, when T is a single bond, A also represents a single bond;
When l1 is 1, when T is a single bond, B also represents a single bond;
H and I are each independently a group selected from a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, and a combination thereof.

The side chain is preferably any one type of photoreactive side chain selected from the group consisting of the following formulas (7) to (10).
where A, B, D, Y ₁ , X, Y ₂ and R have the same definitions as above;
l represents an integer from 1 to 12;
m represents an integer of 0 to 2; m1 and m2 represent integers of 1 to 3;
n represents an integer from 0 to 12 (however, when n=0, B is a single bond).

The side chain is preferably any one type of photoreactive side chain selected from the group consisting of the following formulas (11) to (13).
where A, X, l, m, m1 and R have the same definitions as above.

The side chain is preferably a photoreactive side chain represented by the following formula (14) or (15).
where A, Y ₁ , l, m1 and m2 have the same definitions as above.

The side chain is preferably a photoreactive side chain represented by the following formula (16) or (17).
where A, X, l and m have the same definitions as above.

The side chain is preferably a photoreactive side chain represented by the following formula (18) or (19).
(wherein A, B, Y ₁ and R ₁ have the same definitions as above.
One of q1 and q2 is 1 and the other is 0;
l represents an integer of 1 to 12, m1 and m2 represent integers of 1 to 3;

The side chain is preferably a photoreactive side chain represented by the following formula (20).
where A, Y ₁ , X, l and m have the same definitions as above.

Further, as a component forming the photoreactive polymer film, a polymer having one type of liquid crystalline side chain selected from the group consisting of the following formulas (21) to (31) may be included. For example, when the photoreactive side chain of the above-mentioned polymer forming the photoreactive polymer film does not have liquid crystallinity, or when the main chain of the above-mentioned polymer forming the photoreactive polymer film has liquid crystallinity. In the case where the component forming the photoreactive polymer film does not have a liquid crystalline side chain, it is preferable that the component forming the photoreactive polymer film has one type of liquid crystalline side chain selected from the group consisting of the following formulas (21) to (31).
where A, B, q1 and q2 have the same definitions as above;
Y ₃ is a group selected from the group consisting of a monovalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a nitrogen-containing heterocycle, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof. and each hydrogen atom bonded to them may be independently substituted with -NO ₂ , -CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyloxy group having 1 to 5 carbon atoms;
R ₃ is a hydrogen atom, -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, nitrogen-containing Represents a heterocycle, an alicyclic hydrocarbon having 5 to 8 carbon atoms, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms;
l represents an integer from 1 to 12, m represents an integer from 0 to 2, however, in formulas (23) to (24), the sum of all m is 2 or more, and formulas (25) to (26) ), the sum of all m is 1 or more, and m1, m2 and m3 each independently represent an integer from 1 to 3;
R ₂ is a hydrogen atom, -NO ₂ , -CN, a halogen group, a monovalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a nitrogen-containing heterocycle, and an alicyclic hydrocarbon having 5 to 8 carbon atoms, and represents an alkyl group or an alkyloxy group;
Z ₁ and Z ₂ represent a single bond, -CO-, -CH ₂ O-, -CH=N-, -CF ₂ -.

<<Production method of photoreactive polymer membrane>>
The above photoreactive polymer film can be produced by polymerizing the photoreactive side chain monomer having the above photoreactive side chain, and in some cases combining the photoreactive side chain monomer with the above monomer having the liquid crystalline side chain. can be obtained by copolymerizing. For example, it can be manufactured by referring to [0062] to [0090] of WO2017/061536 (all contents of this publication are incorporated into the present application by reference).

<First and second liquid crystal retarders>
The polarization imaging device of the present invention includes first and second liquid crystal retarders.
The first and second liquid crystal retarders are not particularly limited as long as they can provide desired retardation in the first to third imaging.
In particular, in the first to third imaging, a short period of time, specifically on the order of milliseconds, more specifically 1000 milliseconds or less, preferably 600 milliseconds or less, more preferably 350 milliseconds or less, most preferably Preferably, the desired retardation can be provided in 50 milliseconds or less.

It is preferable that the first liquid crystal retarder and the second liquid crystal retarder each independently act as a variable wavelength plate.
Specifically, it should work as follows.
During the first imaging, it is preferable that the 11th retardation of the first liquid crystal retarder be π/2 and the 21st retardation of the second liquid crystal retarder be zero.
Further, during the second imaging, it is preferable that the 12th retardation of the first liquid crystal retarder be zero and the 22nd retardation of the second liquid crystal retarder be π/2.
Furthermore, during the third imaging, it is preferable that the 13th retardation of the first liquid crystal retarder be zero and the 23rd retardation of the second liquid crystal retarder be zero.

In the first to third imaging, the first Stokes parameter S ₁ , the second Stokes parameter S ₂ , and the third Stokes parameter S ₃ can be obtained as follows.
That is, during the first imaging, each linearly polarized light component passes through the first liquid crystal retarder and is coaxially converted into RCP and LCP, respectively. In addition, each coaxially converted circularly polarized light component, RCP and LCP, which has passed through the first liquid crystal retarder, passes through the second liquid crystal retarder and is transferred to the anisotropic diffraction grating while maintaining the polarization state. The incident circularly polarized light components are spatially separated as ±1st-order diffracted light and imaged on the light receiving element array. At this time, since the ±1st-order light is converted from the 0deg and 90deg linear polarization components of the incident light, the spatial distribution of _S1 can be obtained by taking the difference between the light intensity distributions of both components.

In the second imaging, as described above, the retardation of the first liquid crystal retarder is set to zero, and the retardation of the second liquid crystal retarder is set to π/2.
By the second imaging, +45 deg and -45 deg linearly polarized light components of the light to be measured are spatially separated as ±1st order diffracted light and imaged on the light receiving element array, and the spatial distribution of S ₂ is determined.

In the third imaging, as described above, the retardation of the first liquid crystal retarder is set to zero, and the retardation of the second liquid crystal retarder is set to zero.
By the third imaging, the RCP component and LCP component of the incident light enter the anisotropic diffraction grating while maintaining the polarization state, and the spatial distribution of _S3 is determined from the difference in the intensity of the diffracted light.

By doing as described above, the first to third Stokes parameters S ₁ to S ₃ can be obtained by imaging three times.
Note that the first imaging, the second imaging, and the third imaging do not necessarily have to be performed in that order.
By varying the retardation of the first and second liquid crystal retarders at a desired response speed, the first to third Stokes parameters S ₁ to S ₃ can be determined at a speed that matches the response speed. Further, if the first to third Stokes parameters S ₁ to S ₃ can be determined at high speed, polarization imaging can be performed even if the object to be imaged is dynamic. Therefore, it is preferable to use first and second liquid crystal retarders having desired retardation response speeds.

The first and second liquid crystal retarders can be manufactured as follows.
That is, two substrates with liquid crystal alignment films are prepared. After aligning the liquid crystal alignment films of two substrates with liquid crystal alignment films in a predetermined direction, the predetermined directions are made to match, the liquid crystal alignment film sides are made to face each other, and the gap between the opposing liquid crystal alignment films is set to a predetermined value. Distance and prepare cells.
A liquid crystal retarder can be obtained by filling the gap of the cell with a low-molecular liquid crystal. Here, as the low-molecular liquid crystal, nematic liquid crystal or ferroelectric liquid crystal, which are conventionally used in liquid crystal display elements, etc., described in "(B) Low-molecular liquid crystal layer" above can be used. Those illustrated can be used.
In addition, in the above description, it has been described that a rubbing alignment type is used as the liquid crystal alignment film, but a photo alignment type may be used instead of the rubbing alignment type.
The obtained first and second liquid crystal retarders preferably have first and second voltage application means. A voltage is applied to the liquid crystal retarder by the first and second voltage application means, and the voltage preferably provides a desired retardation, for example the retardation described above.

<Lens element>
The polarization imaging device of the present invention has a lens element. The lens element is not particularly limited as long as it has the function of forming an image on the light-receiving element described later.
<Light receiving element>
The polarization imaging device of the present invention has a light receiving element. The light receiving element is not particularly limited as long as the above-mentioned first to third Stokes parameters S ₁ to S ₃ can be determined from the imaged data. Note that in order to increase the measurement speed of the first to third Stokes parameters S ₁ to S ₃ , it is preferable that the light receiving element has a response speed commensurate with the measurement speed.

The polarization imaging device of the present invention will be explained using the drawings.
FIG. 3 is a diagram illustrating an outline of the polarization imaging device of the present invention. Note that FIG. 3 is an example for explanation, and the polarization imaging device of the present invention is not limited to the device shown in FIG. 3.
The polarization imaging device 1 of the present invention includes an imaging lens 2, a color filter 3, a first liquid crystal retarder 4, a second liquid crystal retarder 5, an anisotropic diffraction grating 6, and a light receiving element 7.
The imaging lens 2 is arranged at a variable distance from the light receiving element array so that the focus can be adjusted.
Since the diffraction angle of the anisotropic diffraction grating 6 is wavelength dependent, a problem may arise in which an image becomes blurred due to angular dispersion for white light. Therefore, a color filter 3 is inserted to reduce the influence of dispersion. An anisotropic diffraction grating 6 whose retardation is optimized according to the observation wavelength is used in combination with an interference filter of the corresponding frequency band.

By introducing the imaging section (imaging lens 2, light receiving element 7, for example, a light receiving element array), it is possible to perform imaging measurement without being limited to point measurement.
Generally, to obtain the Stokes parameter, each light intensity of the 0deg linear polarization component, 90deg linear polarization component, 45deg linear polarization component, -45deg linear polarization component, right-handed circularly polarized component, and left-handed circularly polarized component in equation (1) is required. , and Fourier analysis methods such as the rotation phase transfer method are used. However, since these methods require multiple measurements in principle, they are not suitable for measuring objects whose states change over time.
On the other hand, in the polarization imaging device of the present invention, the information necessary for measuring the Stokes parameter is spatially separated and acquired as intensity information, thereby making it possible to perform polarization imaging measurement in a snapshot. Furthermore, by using the first and second liquid crystal retarders having desired retardation response speeds, it is possible to measure even dynamic objects. One of the features is that it is inexpensive because it does not require expensive optical elements including a diffraction grating.

The polarization image values of the present invention can be applied to various fields because they can be measured two-dimensionally, whether it is a dynamic object or a static object. Examples include, but are not limited to, the medical field, the field of automatic driving technology for automobiles, the field of security, etc.
EXAMPLES Hereinafter, the present invention will be specifically explained using examples, but the present invention is not limited only by these examples.

<Preparation of anisotropic diffraction grating>
As a recording material, a photocrosslinkable polymer liquid crystal (4-(4-methoxycinnamoyloxy)biphenyl side groups (P6CB)) represented by the following formula was used.
P6CB was dissolved in dichloromethane and spin coated onto a glass substrate to a thickness of 300 nm.
Two glass substrates coated with P6CB films were prepared and pasted together with the P6CB films facing each other to create an empty cell having a gap of 9 μm. The prepared empty cell was irradiated with an ultraviolet laser having a wavelength of 325 nm emitted from a He-Cd laser with an exposure energy of 600 mJ/cm ² while causing OC interference. After irradiation, heat treatment was performed in an oven at 150° C. for 15 minutes, and after the heat treatment, low molecular liquid crystal ZLI4792 (manufactured by Merck & Co., Ltd.) was injected into the cell to produce a cell type OC lattice. The diameter of the produced anisotropic diffraction grating was 8 mm.
The obtained anisotropic diffraction grating had a function in which the optical anisotropy was periodically modulated, specifically, a function to spatially separate right-handed circularly polarized light and left-handed circularly polarized light in the ±1st-order optical directions. .

<Production of first and second liquid crystal retarders>
The first and second liquid crystal retarders were each manufactured as follows.
A substrate with a polyimide film on one side is created by spin-coating a polyimide precursor solution produced by reacting cyclobutanetetracarboxylic dianhydride and diaminodiphenyl ether onto a glass substrate whose surface is coated with indium tin oxide (ITO). was prepared. The obtained polyimide film was subjected to alignment treatment by rubbing.
Two substrates having the polyimide films subjected to the alignment treatment were prepared, and the polyimide film sides were made to face each other, and the alignment directions of the alignment treatments were made to match, thereby producing an empty cell having a gap of 13.5 μm.
A first liquid crystal retarder was obtained by injecting a low-molecular liquid crystal ZLI4792 (manufactured by Merck & Co.) into the cell.
In addition, a second liquid crystal retarder was obtained in the same manner as the first liquid crystal retarder.
The first liquid crystal retarder and the second liquid crystal retarder were each provided with first and second voltage applying means, and could have a desired retardation by applying a voltage.

<Production of polarization imaging device>
A polarization imaging device was manufactured according to the schematic diagram of a polarization imaging device shown in FIG.
Specifically, as shown in FIG. 3, the polarization imaging device includes, in order from the subject, an imaging lens, a color filter (FL532-3 manufactured by Thorlabs (center wavelength 532 nm), the first liquid crystal retarder obtained above, The second liquid crystal retarder obtained above, the anisotropic diffraction grating obtained above, and a light receiving element were arranged to serve as a light receiving element.A commercially available camera (α6000 manufactured by SONY) was used as the light receiving element.

<Imaging measurement>
In this example, imaging measurements were performed using a scarab beetle as a subject that exhibits selective reflection characteristics with respect to circularly polarized light.
Specifically, first, the first and second voltage application means are adjusted so that the retardation of the first liquid crystal retarder is π/2 and the retardation of the second liquid crystal retarder is zero, The first imaging was performed.
During the first imaging, each linearly polarized light component was transmitted through a first liquid crystal retarder and coaxially converted into RCP and LCP, respectively.
In addition, each coaxially converted circularly polarized light component, RCP and LCP, which has passed through the first liquid crystal retarder, passes through the second liquid crystal retarder and is transferred to the anisotropic diffraction grating while maintaining the polarization state. The incident circularly polarized light components were spatially separated as ±1st-order diffracted light and imaged on the light receiving element array. At this time, the ±1st-order light is converted from the 0deg and 90deg linear polarization components of the incident light, so by taking the difference between the light intensity distributions of both components, the spatial distribution of _S1 was found. .

Next, a second imaging was performed.
In the second imaging, the first and second voltage application means were adjusted so that the retardation of the first liquid crystal retarder was zero and the retardation of the second liquid crystal retarder was π/2.
By the second imaging, +45 deg and -45 deg linearly polarized light components of the measured light were spatially separated as ±1st-order diffracted light and imaged on the light receiving element array, and the spatial distribution of S ₂ was determined.

Finally, a third image was taken.
In the third imaging, the first and second voltage application means were adjusted so that the retardation of the first liquid crystal retarder was zero and the retardation of the second liquid crystal retarder was zero.
In the third imaging, the RCP component and LCP component of the incident light entered the anisotropic diffraction grating while maintaining the polarization state, and the spatial distribution of _S3 was determined from the difference in the intensity of the diffracted light.

It was possible to capture images in 333 milliseconds from the first image capture to the third image capture.
The results from the first imaging to the third imaging are shown in FIG. Note that in FIG. 4, from the left side, (a) a camera image, and (b) Stokes distributions S ₁ to S ₃ restored from the camera image are shown. Note that (c) shows the Stokes distributions S ₁ to S ₃ measured by the rotary phase transfer method. Further, in FIG. 4, first imaging, second imaging, and third imaging are shown in order from the top.
From FIG. 4, it was confirmed that each element of the spatial distribution of Stokes parameters can be restored from a single captured image according to this example. Even when compared with the conventional method, the rotary transfer retarder method, results are in good agreement.
Furthermore, it has been found that while the conventional rotating analyzer method requires at least four images to be taken, in the present invention, only the first to third images are sufficient, and fewer images need to be taken.
Furthermore, since it is possible to acquire images with a response speed of milliseconds, it is possible to measure polarization spatial distribution with high temporal resolution, and specifically, to measure polarization spatial distribution even if the imaging target is dynamic.
Furthermore, compared to a conventional method using a polarizer array, in which the spatial resolution is limited to four pixels, the present invention has the advantage that the spatial resolution per pixel of the camera can be fully utilized. .

Claims (18)

A polarization imaging device comprising a lens element, a first liquid crystal retarder, a second liquid crystal retarder, an anisotropic diffraction grating element whose optical anisotropy is periodically modulated, and a light receiving element arranged in order from the object to be imaged. There it is,
a first image formed with an 11th retardation of the first liquid crystal retarder set to π/2 and a 21st retardation of the second liquid crystal retarder set to 0;
second imaging in which a twelfth retardation of the first liquid crystal retarder is set to 0 and a twenty-second retardation of the second liquid crystal retarder is set to π/2; and
third imaging performed with a 13th retardation of the first liquid crystal retarder set to 0 and a 23rd retardation of the second liquid crystal retarder set to 0;
obtained,
The first Stokes parameter S ₁ from the first imaging ,
a second Stokes parameter S ₂ from the second imaging , and
The polarization imaging device described above, wherein a third Stokes parameter S ₃ is obtained from the third imaging, and a polarization spatial distribution is measured . 2. The apparatus of claim 1, wherein the first liquid crystal retarder and the second liquid crystal retarder each independently act as a variable wavelength plate. The apparatus according to claim 1 or 2, wherein the first imaging, the second imaging, and the third imaging are performed in 1000 milliseconds or less. The apparatus according to claim 1 or 2, wherein the first imaging, the second imaging, and the third imaging are performed in 1000 milliseconds or less, and a polarization spatial distribution of a dynamic imaging target can be measured. The anisotropic diffraction grating element has an anisotropic diffraction grating having a plurality of grating vectors having mutually different directions, and the grating vectors are periodically modulated in at least anisotropic orientation or birefringence. The device according to any one of items 1 to 4 . The anisotropic diffraction grating element has an anisotropic diffraction grating that spatially separates Stokes parameter information of incident light according to anisotropic orientation and birefringence distribution and converts it into intensity information. Apparatus according to any one of claims 1 to 5 . The anisotropic diffraction grating element has a highly photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. The device according to any one of claims 1 to 6 , comprising an anisotropic diffraction grating having a molecular film. The anisotropic diffraction grating element has a highly photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. The device according to any one of claims 1 to 6 , comprising an anisotropic diffraction grating made of a molecular film. The anisotropic diffraction grating element is
I) a first transparent substrate layer; and II) a first photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. 9. The device according to any one of claims 1 to 8 , comprising an anisotropic diffraction grating having a first photoreactive polymer film having: The anisotropic diffraction grating element is
I) first transparent base layer;
II) A first photoreactive polymer having a first photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking and (A-2) photoisomerization. film;
III) a second transparent base layer; and IV) a second photoreactive side chain that causes at least one reaction selected from the group consisting of (A-1) photocrosslinking, and (A-2) photoisomerization. a second photoreactive polymer film having;
has
The above II) first photoreactive polymer film and the above IV) second photoreactive polymer film are arranged to face each other, and the above II) first film and the above IV) second film are arranged so as to face each other. The device according to any one of claims 1 to 9 , comprising an anisotropic diffraction grating between which (B) a low molecular weight liquid crystal layer is arranged. Information on the Stokes parameter of light incident on the photoreactive polymer film is obtained by exposing the photoreactive polymer film to interference exposure with desired polarized light and forming an arbitrary diffraction pattern on the photoreactive polymer film. according to claims 7 to 10, which is an anisotropic diffraction grating that spatially separates and converts into intensity information according to the anisotropic orientation and birefringence distribution formed in the photoreactive polymer film. Apparatus according to any one of the clauses. The photoreactive polymer film has the following formulas (1) to (6):
(In the formula, A, B, and D each independently represent a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO -O- or -O-CO-CH=CH-;
S is an alkylene group having 1 to 12 carbon atoms, and the hydrogen atoms bonded to them may be replaced with halogen groups;
T is a single bond or an alkylene group having 1 to 12 carbon atoms, and the hydrogen atoms bonded thereto may be replaced with a halogen group;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
Y ₂ is a group selected from the group consisting of a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof; The hydrogen atoms bonded to are each independently -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. may be substituted with an alkyloxy group;
R represents a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, or has the same definition as Y ₁ ;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
Cou represents a coumarin-6-yl group or a coumarin-7-yl group, and the hydrogen atoms bonded to them are each independently -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH- May be substituted with CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyloxy group having 1 to 5 carbon atoms;
One of q1 and q2 is 1 and the other is 0;
q3 is 0 or 1;
P and Q are each independently selected from the group consisting of a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof. group; However, when X is -CH=CH-CO-O-, -O-CO-CH=CH-, P or Q on the side to which -CH=CH- is bonded is an aromatic ring, When the number of P's is 2 or more, the P's may be the same or different; when the number of Q's is 2 or more, the Q's may be the same or different;
l1 is 0 or 1;
l2 is an integer from 0 to 2;
When l1 and l2 are both 0, when T is a single bond, A also represents a single bond;
When l1 is 1, when T is a single bond, B also represents a single bond;
H and I are each independently a group selected from a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, and a combination thereof. )
The device according to any one of claims 7 to 11 , comprising a photoreactive polymer having any one type of photoreactive side chain selected from the group consisting of:

The photoreactive polymer film has the following formulas (7) to (10).
(In the formula, A, B, and D each independently represent a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO -O- or -O-CO-CH=CH-;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
l represents an integer from 1 to 12;
m represents an integer of 0 to 2; m1 and m2 represent integers of 1 to 3;
n represents an integer from 0 to 12 (however, when n = 0, B is a single bond);
Y ₂ is a group selected from the group consisting of a divalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, an alicyclic hydrocarbon having 5 to 8 carbon atoms, and a combination thereof; The hydrogen atoms bonded to are each independently -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms. may be substituted with an alkyloxy group;
R represents a hydroxy group, an alkoxy group having 1 to 6 carbon atoms, or has the same definition as Y ₁ )
The device according to any one of claims 7 to 11 , comprising a photoreactive polymer having any one type of photoreactive side chain selected from the group consisting of:

The photoreactive polymer film has the following formulas (11) to (13):
(In the formula, A is each independently a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O- , or represents -O-CO-CH=CH-;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
l represents an integer of 1 to 12, m represents an integer of 0 to 2, m1 represents an integer of 1 to 3;
R represents a ring selected from a monovalent benzene ring, a naphthalene ring, a biphenyl ring, a furan ring, a pyrrole ring, and an alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or different substituents thereof; It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (wherein R ₀ is a hydrogen atom or a carbon number of 1 to 5 ), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms (may be substituted with an oxy group, or represents a hydroxy group or an alkoxy group having 1 to 6 carbon atoms)
The device according to any one of claims 7 to 11 , comprising a photoreactive polymer having any one type of photoreactive side chain selected from the group consisting of:

The photoreactive polymer film has the following formula (14) or (15)
(In the formula, A is each independently a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O-, or represents -O-CO-CH=CH-;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
l represents an integer from 1 to 12, m1 and m2 represent integers from 1 to 3)
The device according to any one of claims 7 to 11 , comprising a photoreactive polymer having a photoreactive side chain represented by:

The photoreactive polymer film has the following formula (16) or (17) (where A is a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH -CO-, -CH=CH-CO-O-, or -O-CO-CH=CH-;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
l represents an integer from 1 to 12, m represents an integer from 0 to 2)
The device according to any one of claims 7 to 11 , comprising a photoreactive polymer having a photoreactive side chain represented by:

The photoreactive polymer film has the following formula (18) or (19)
(In the formula, A and B each independently represent a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O -, or -O-CO-CH=CH-;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
One of q1 and q2 is 1 and the other is 0;
l represents an integer of 1 to 12, m1 and m2 represent integers of 1 to 3;
R ₁ is a hydrogen atom, -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, a halogen group, an alkyl group having 1 to 5 carbon atoms, or an alkyl group having 1 to 5 carbon atoms (represents oxy group)
The device according to any one of claims 7 to 11 , comprising a photoreactive polymer having any one type of photosensitive side chain selected from the group consisting of:

The photoreactive polymer film has the following formula (20)
(In the formula, A is a single bond, -O-, -CH ₂ -, -COO-, -OCO-, -CONH-, -NH-CO-, -CH=CH-CO-O-, or -O -CO-CH=CH-;
Y ₁ represents a ring selected from monovalent benzene ring, naphthalene ring, biphenyl ring, furan ring, pyrrole ring, and alicyclic hydrocarbon having 5 to 8 carbon atoms, or the same or It is a group in which 2 to 6 different rings are bonded via a bonding group B, and the hydrogen atoms bonded to them are each independently -COOR ₀ (in the formula, R ₀ is a hydrogen atom or a group having 1 to 1 carbon atoms) 5), -NO ₂ , -CN, -CH=C(CN) ₂ , -CH=CH-CN, halogen group, alkyl group having 1 to 5 carbon atoms, or alkyl group having 1 to 5 carbon atoms May be substituted with an alkyloxy group;
X is a single bond, -COO-, -OCO-, -N=N-, -CH=CH-, -C≡C-, -CH=CH-CO-O-, or -O-CO-CH= When it represents CH- and the number of X is 2, the Xs may be the same or different;
12. The polymer according to any one of claims 7 to 11 , comprising a photoreactive polymer having a photoreactive side chain (l represents an integer of 1 to 12, m represents an integer of 0 to 2). equipment.

Images