JP2006018325A - Variable optical characteristic optical element, and display device equipped with variable optical characteristic optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a variable optical characteristic optical element having simple structure, keeping the loss of light quantity small, driven at low voltage, and changing optical characteristic without causing blur. <P>SOLUTION: A variable focus lens 1 functioning as the variable optical characteristic optical element has such basic constitution where chiral nematic liquid crystal 2 is held between a plate glass 4 and a lens 5 whose inner sides are respectively coated with transparent electrode film 3 through an alignment layer 6, and enclosed by sealing material 7. The pitch P of the twist of the chiral nematic liquid crystal 2 is set to be very small in comparison with the wavelength λ of light. That means, (1) P<<λ holds. If the pitch P is set to be very small in comparison with the wavelength λ of the light, the lens 5 acts as a lens having a refractive index n' regardless of the polarization of incident light. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical property variable optical element, and more particularly to an optical property variable optical element that changes an optical property and a display device including the optical property variable optical element.

In focusing a zoom lens or an imaging apparatus, the lens is usually moved mechanically.

  However, it is impossible to move the whole or part of the lens system with an electronic endoscope or micromachine eye that is required to be ultra-compact. Even in a salt film camera or the like, it is desirable that zooming and focusing can be performed without moving the lens system in order to reduce weight and cost.

  Therefore, as a means for solving these problems without moving the lens, a variable focus lens has been proposed in, for example, Japanese Patent Application Laid-Open Nos. 5-34656 and 4-345124.

  For example, as shown in FIG. 29, a varifocal lens 201 proposed in Japanese Patent Laid-Open No. 5-34656 includes a chiral nematic liquid crystal 202 in which the major axis of liquid crystal molecules is twisted 360 °, and a transparent electrode film 203 on the inner side. Each of the coated flat glass 204 and Funnelnes substrate 205 is sandwiched through an alignment film 206 and sealed with a sealing material 207.

  In the varifocal lens 201 having such a configuration, when the power source 208 is turned on by the switch 209 and an electric field is applied between the alignment films 206, the chiral nematic liquid crystal 202 becomes homeotropic alignment as shown in FIG. Isotropic with respect to polarized light, and the refractive index of the chiral nematic liquid crystal 202 is lower than the state of FIG. 29 or is equal depending on the direction of polarization.

  In the state of FIG. 29, when the polarization direction of incident light and the major axis of the liquid crystal molecules 210 of the chiral nematic liquid crystal 202 on the incident side (long direction of the ellipsoid in FIG. 29) are equal, the refractive index of the chiral nematic liquid crystal 202 is When the polarization direction of the incident light coincides with the minor axis direction of the liquid crystal molecules on the incident side, the refractive index of the chiral nematic liquid crystal 202 becomes low.

  This is because, in this example, the twist pitch P of the chiral nematic liquid crystal 202 is 10 μ to 30 μ, which is much larger than the wavelength λ of light (approximately 0.4 μ to 0.7 μ for visible light). The light incident from one side proceeds with the polarization rotated following the twist of the liquid crystal molecules. The reason for this is described in, for example, “Katsumi Yoshino and Masanori Ozaki; Fundamentals P91 to P93 of liquid crystal and display application; Corona, Inc.” (hereinafter referred to as Document 1), and the description thereof will be omitted.

  Accordingly, the focal length of the varifocal lens 201 in FIG. 29 is short for the polarization in the long axis direction of the liquid crystal molecules on the incident side, and FIG. 29 is for the polarization in the short axis direction of the liquid crystal molecules on the incident side. The focal length of the variable focal length lens 201 becomes long, and the conventional variable focal length lens 201 becomes a double focal length lens, and only a blurred image is formed.

  The present invention has been made in view of the above circumstances, and has an optical characteristic variable optical element and an optical characteristic that have a simple structure, have little light loss, can be driven by a low voltage, and do not cause blurring, and change optical characteristics. An object of the present invention is to provide a display device including a variable optical element.

のいずれか１つを満たすことを特徴とする光学特性可変光学素子。 The optical property variable optical element of the present invention encloses liquid crystal in a space formed by a pair of members, controls the alignment state of liquid crystal molecules of the liquid crystal by an external physical action, and controls the optical properties of the liquid crystal. In the optical property variable optical element to be changed,
The liquid crystal is at least

An optical property variable optical element characterized by satisfying any one of the above.

であって、ｎｅ は液晶分子長軸方向の偏光に対する屈折率、ｎ０ は液晶分子短軸方向の偏光に対する屈折率、ｄは液晶の厚さ、
φは

である。 However,
P is the twist pitch of the liquid crystal,
λ is the wavelength of the incident light,
Γ is

Where ne is the refractive index for polarized light in the liquid crystal molecule long axis direction, n0 is the refractive index for polarized light in the liquid crystal molecule short axis direction, d is the thickness of the liquid crystal,
φ is

It is.

のいずれか１つを満たすことを特徴とする表示装置。
ただし、
Ｐは液晶のねじれのピッチ、
λは入射光の波長、
Γは

であって、ｎｅ は液晶分子長軸方向の偏光に対する屈折率、ｎ０ は液晶分子短軸方向の偏光に対する屈折率、ｄは液晶の厚さ、
φは

である。 The display device having the optical property variable optical element of the present invention encloses liquid crystal in a space formed by a pair of members, controls the alignment state of the liquid crystal molecules of the liquid crystal by an external physical action, In a display device including an optical property variable optical element that changes the optical properties of liquid crystal,
The liquid crystal is at least

A display device characterized by satisfying any one of the above.
However,
P is the twist pitch of the liquid crystal,
λ is the wavelength of the incident light,
Γ is

Where ne is the refractive index for polarized light in the liquid crystal molecule long axis direction, n0 is the refractive index for polarized light in the liquid crystal molecule short axis direction, d is the thickness of the liquid crystal,
φ is

It is.

  According to the present invention, since the liquid crystal has a small twist pitch compared to the wavelength of light transmitted through the liquid crystal, the structure is simple, the light amount loss is small, the light can be driven with a low voltage, and there is no blurring. There is an effect that the characteristics can be changed.

  Embodiments of the present invention will be described below with reference to the drawings.

  1 to 17 relate to the first embodiment of the present invention, FIG. 1 is a block diagram showing the basic configuration of a variable focus lens, and FIG. 2 shows the refractive index ellipsoid of the chiral nematic liquid crystal molecules of FIG. FIG. 3 is an explanatory diagram for explaining the operation of the variable focus lens of FIG. 1, FIG. 4 is a configuration diagram showing a specific configuration of the variable focus lens of FIG. 1, and FIG. 5 is a first diagram of the variable focus lens of FIG. 6 is a diagram showing a chiral smectic C-phase liquid crystal molecular arrangement of the chiral smectic liquid crystal used in the first modification, FIG. 6 is a configuration diagram showing the configuration of a variable focus lens using the chiral smectic liquid crystal of FIG. 5, and FIG. FIG. 8 is a configuration diagram showing the configuration of a second modification of the variable focus lens of FIG. 1 using chiral cholesteric liquid crystal, and FIG. 9 is a configuration diagram of the variable focus lens of FIG. FIG. 10 is an explanatory diagram for explaining the operation. FIG. 11 is a diagram showing the measured value of the reflectance of the chiral cholesteric liquid crystal shown in FIG. 8, FIG. 11 is a diagram showing the configuration of the second modification of the variable focus lens shown in FIG. 1 using a discotic liquid crystal, and FIG. FIG. 13 is a diagram showing the refractive index ellipsoid of the discotic liquid crystal molecules of FIG. 11, and FIG. 14 is a first view of the discotic liquid crystal of FIG. 12 viewed from the Z direction. FIG. 15 is a second view of the discotic liquid crystal of FIG. 12 viewed from the Z direction, and FIG. 16 is a diagram of a variable focus lens using a magnetic field to change the orientation of the chiral nematic liquid crystal of FIG. FIG. 17 is a block diagram showing the configuration of a variable focus lens using a temperature change to change the alignment of the chiral nematic liquid crystal shown in FIG.

As shown in FIG. 1, a varifocal lens 1 as an optical property variable optical element according to the first embodiment includes a flat glass 4 and a lens each having a chiral nematic liquid crystal 2 and a transparent electrode film 3 coated inside. The twisted pitch P of the chiral nematic liquid crystal 2 is very small compared to the wavelength λ of light. Shall. That means
[Equation 1]
P << λ (1)
It is. Thus, when the pitch P is very small compared to the wavelength λ of light, the lens 5 acts as a lens having a refractive index n ′ regardless of the polarization of the incident light.

ここで、ｎeは液晶分子長軸方向の偏光に対する屈折率
ｎoは液晶分子短軸方向の偏光に対する屈折率
であり、図２にカイラルネマテック液晶２の入射側の液晶分子に対応する屈折率楕円体を示す。ここで、ｘ軸及びｚ軸は、液晶分子の短軸方向、ｙ軸は液晶分子の長軸方向になっている。なお、ｎe＞ｎoとする。 [Equation 2]

Where ne is the refractive index for the polarized light in the long axis direction of the liquid crystal molecule.
No is a refractive index with respect to polarized light in the minor axis direction of the liquid crystal molecule, and FIG. 2 shows a refractive index ellipsoid corresponding to the liquid crystal molecule on the incident side of the chiral nematic liquid crystal 2. Here, the x-axis and the z-axis are the minor axis direction of the liquid crystal molecules, and the y-axis is the major axis direction of the liquid crystal molecules. Note that ne> no.

  Next, the reason why the chiral nematic liquid crystal 2 according to the present embodiment behaves as an isotropic medium having an effective refractive index n ′ by the Jones vector and matrix will be described below.

で与えられる。ただし、
［数４］

［数５］

［数６］

［数７］

［数８］

である。 According to the formula 3.107, the formula 3.110, and the formula 3.126 shown in P85 to 92 of the above-mentioned document 1, when the absolute phase change exp (−iα) is included, it is shown in FIG. Jones matrix Wt for chiral nematic liquid crystal 2 of thickness d
[Equation 3]

Given in. However,
[Equation 4]

[Equation 5]

[Equation 6]

[Equation 7]

[Equation 8]

It is.

  Here, ordinary light is defined as polarization in the minor axis direction of liquid crystal molecules, and extraordinary light is defined as polarization in the major axis direction of liquid crystal molecules, or polarization in the direction when the major axis is projected onto a plane perpendicular to the optical axis. Then, Γ represents the phase difference between ordinary light and extraordinary light by the chiral nematic liquid crystal 2.

  Φ represents the twist angle of the liquid crystal molecules of the chiral nematic liquid crystal 2 in radians. Further, the coordinate systems of the equations (3) and (8) are assumed to be the x, y, and z axes shown in FIG. That is, the x-axis is directed from the front to the back of the paper, and the y-axis is the direction of the major axis of the liquid crystal molecule at the incident surface of the chiral nematic liquid crystal 2.

  Now, it will be examined how Wt in the expression (3) becomes under the condition of the expression (1).

と変形できる。そこで、Ｐ／λ→０の時、式（３）のＷtの極限値ＷtLを求めてみる。 First, equation (1) is
[Equation 9]

And can be transformed. Therefore, when P / λ → 0, the limit value WtL of Wt in equation (3) is determined.

であるから、Ｐ／λ＜＜１のとき
［数１１］

となり、Ｐ／λ→０のとき｜Γ／Φ｜→０となる。 [Equation 10]

Therefore, when P / λ << 1, [Equation 11]

When P / λ → 0, | Γ / Φ | → 0.

［数１３］

［数１４］

［数１５］

と近似でき、Ｐ／λ→０のとき、それぞれ、
［数１６］
Ｘ→Φ （１６）
［数１７］
ｃｏｓＸ→ｃｏｓΦ （１７）
［数１８］

［数１９］

となるので、Ｐ／λ→０のとき
［数２０］

となる。これは屈折率ｎ’＝（ｎe＋ｎo）／２、厚さｄの、光軸に沿って等方な媒質のジョーンズ行列にほかならない。 [Equation 12] under the condition of equation (11)

[Equation 13]

[Formula 14]

[Equation 15]

When P / λ → 0, respectively,
[Equation 16]
X → Φ (16)
[Equation 17]
cosX → cosΦ (17)
[Equation 18]

[Equation 19]

Therefore, when P / λ → 0, [Equation 20]

It becomes. This is nothing but a Jones matrix of an isotropic medium along the optical axis with a refractive index n ′ = (ne + no) / 2 and a thickness d.

  Therefore, since P / λ << 1, the varifocal lens 1 of FIG. 1 acts as a lens having a refractive index n ′ and can realize image formation without blur.

  In the varifocal lens 1 of FIG. 1, when the AC power supply 8 is turned on by the switch 9 and an electric field is applied between the alignment films 6, the chiral nematic liquid crystal 2 is arranged as shown in FIG. Since it is an isotropic medium of no, it becomes a liquid crystal lens having a different focal length compared to the state of FIG. 1, and a variable focus lens without blur can be realized.

  Next, a specific configuration example of the variable focus lens 1 will be described with reference to FIG. As shown in FIG. 4, the varifocal lens 1 has a configuration in which the voltage is continuously variable by the variable resistor 21, and the arrangement of the liquid crystal molecules is intermediate between the above-described FIG. 1 and FIG. It is configured so that it can be brought. Thereby, a liquid crystal lens whose focal length continuously changes can be realized.

  In the case of an intermediate array as shown in FIG. 4, the value of ne is replaced with the refractive index ne ′ of extraordinary light, which is an intermediate value between ne and no, so that the above formulas (3) to (3) (20) is satisfied.

  By configuring as shown in FIG. 4, the method of applying the voltage is not limited to continuously variable, and a variable focus lens can be realized even if the applied voltage is selected from several discrete voltage values. it can.

  Here, a practical example of the variable focus lens 1 configured as shown in FIG. 4 will be described in detail.

  Although the limit case of P / λ → 0 is shown in Expression (20), there is a case where the limit value does not always apply in an actual liquid crystal lens and variable focus lens, so the approximate expression of Expression (3) is I will guide you.

［数２２］

となり
［数２３］

を得る。従って、ＷtNの値が等方媒質のジョーンズ行列とほぼ等しいと見なせるためには、｜ｉ・Γ／２Φ｜が０に近ければよい。この時ＷtNは、
［数２４］

に近づくが、この式は、液晶が入射光の偏光方向はΓ／４・Γ／Φだけ回転するが、等方媒質であると見なせることを意味している。 When formula (3) is approximated considering the first order of P / λ, it is as follows. That is, in the equations (12) to (14), up to the first order of P / λ, that is, from the equation (10), the second order or more of P / λ, and the second order of Γ / Φ, leaving the first order of Γ / Φ If you omit the following,
[Equation 21]

[Equation 22]

[Formula 23]

Get. Accordingly, in order that the value of WtN can be regarded as being substantially equal to the Jones matrix of the isotropic medium, it is sufficient that | i · Γ / 2Φ | is close to zero. At this time, WtN is
[Equation 24]

This equation means that the liquid crystal rotates as the polarization direction of incident light by Γ / 4 · Γ / Φ, but can be regarded as an isotropic medium.

つまり、
［数２６］

であれば、ボケのない可変焦点レンズが得られる。式（１０）より
［数２７］

となる。 [Equation 25]

That means
[Equation 26]

If so, a variable focus lens without blur can be obtained. From equation (10), [Equation 27]

It becomes.

であれば良い。 When the variable focus lens of the present invention is used for a lens of a relatively low cost product such as an actual imaging device with a lens, for example, an electronic camera, a VTR camera, an electronic endoscope, etc. Since high resolution may not be required, Equation (26) can relax the condition,
[Equation 28]

If it is good.

であればよい。 High resolution is required for lenses of high-quality products such as lenses for electronic imaging devices with a large number of pixels, film cameras, and microscopes.
[Equation 29]

If it is.

であればよい。 In the case of a lens that is not used for image formation, such as an optical disk lens, the conditions are further relaxed,
[Equation 30]

If it is.

  Note that, in common with this embodiment, when the liquid crystal is arranged in a spiral shape, when the major axis direction of the liquid crystal molecules is not perpendicular to the optical axis, that is, when it is oblique, the equation (1) ) And ne in the expressions (26) to (30) may be replaced with the above ne ′.

  Below are some design examples.

If the thickness d of the chiral nematic liquid crystal 2 is thin, the lens power is weak, which is not useful. If it is thick, it causes light scattering and flare.
[Equation 31]
2μ <d <300μ (31)
About is appropriate. As an example of the wavelength λ of light, considering visible light,
[Formula 32]
0.35μ <λ <0.7μ (32)
It is.

The value of ne-no is determined by the physical properties of the liquid crystal.
[Equation 33]
0.01 <| ne-no | <0.4 (33)
There are a lot of substances. Therefore, as a first design example,
d = 15 μ
λ = 0.5μ
ne-no = 0.2
P = 0.05μ
given that,
Γ / 2Φ = π · 0.2 × 0.05 / 0.5 = 0.02π
Thus, Expression (26), Expression (28), Expression (29), and Expression (30) are satisfied.

As a second design example,
d = 30μ
λ = 0.6μ
ne-no = 0.25
P = 0.3μ
given that,
Γ / 2Φ = π · 0.3 × 0.25 / 0.6 = 0.125π
Thus, Expression (26), Expression (28), Expression (29), and Expression (30) are satisfied.

As a third design example, d = 50 μ
λ = 0.55μ
ne-no = 0.2
P = 0.6μ
given that,
Γ / 2Φ = π · 0.2 × 0.6 / 0.55 = 0.218π
Thus, the expressions (28) and (30) are satisfied.

Furthermore, as a fourth design example, a variable focus lens for near infrared light is considered,
d = 200μ
λ = 0.95μ
ne-no = 0.2
P = 0.7μ
Γ / 2Φ = π · 0.2 × 0.7 / 0.95 = 0.458π
Thus, Expression (26), Expression (28), Expression (29), and Expression (30) are satisfied.

  In each of the above design examples, the chiral nematic liquid crystal has been described as an example. However, in order to make the helical pitch of the chiral nematic liquid crystal smaller than the wavelength of light to be used, it is preferable to mix a chiral agent with the liquid crystal.

  As the chiral agent, a cholesteric liquid crystal or a synthetic optically active compound is used. The following chemical formula (1) and chemical formula (2) show examples of chiral nematic liquid crystals, and chemical formula (3) and chemical formula (4) show examples of chiral agents.

化学式（１）
［化２］

化学式（２）
［化３］

化学式（３）
［化４］

化学式（４）
以上の説明において、可変焦点レンズ１に用いる液晶としては、カイラルネマチック液晶２を用いて説明したが、本実施の形態はこれに限らず、可変焦点レンズの第１の変形例として、図５に示ようなカイラルスメクチック液晶３１を用いて構成することができる。この図５は、カイラルスメクチックＣ相の液晶分子配列を示したもので、これを用いた可変焦点レンズ１ａの構造を図６に示す。 [Chemical 1]

Chemical formula (1)
[Chemical formula 2]

Chemical formula (2)
[Chemical formula 3]

Chemical formula (3)
[Chemical formula 4]

Chemical formula (4)
In the above description, the chiral nematic liquid crystal 2 is used as the liquid crystal used in the variable focus lens 1. However, the present embodiment is not limited to this, and a first modification of the variable focus lens is shown in FIG. A chiral smectic liquid crystal 31 as shown can be used. FIG. 5 shows a chiral smectic C phase liquid crystal molecular arrangement, and FIG. 6 shows the structure of a varifocal lens 1a using the same.

  As shown in FIG. 6, in the chiral smectic liquid crystal 31, when no voltage is applied, the liquid crystal molecules are directed in a specific direction for each layer 31a, and the direction rotates with a constant period P.

  When a voltage is applied to this, the liquid crystal molecules of each layer are aligned in the Z-axis direction of the coordinate system as shown in FIG. 7, and the refractive index of the chiral smectic liquid crystal 31 decreases from n ′ in the state of FIG. 6 to no. Then, the focal length of the variable focus lens 1 changes.

  Also in the first modification shown in FIGS. 5 to 7, the expressions (1) to (30) are applicable, and particularly satisfy the expressions (26), (28), (29), and (30). If so, a variable focus lens with less blur can be obtained. In the configuration of FIG. 6 as well, the voltage applied to the chiral smectic liquid crystal 31 can be continuously changed, and the focal length is continuously changed accordingly.

Here, when the design example of the variable focus lens 1a using the chiral smectic liquid crystal 31 is shown, as a parameter,
d = 25μ
λ = 0.55μ
ne-no = 0.3
P = 0.1μ
Then,
Γ / 2Φ = π · 0.3 × 0.1 / 0.55 = 0.0545π
Thus, Expression (26), Expression (28), Expression (29), and Expression (30) are satisfied.

  In addition, “4- (n-hexyloxy) phenyloxy-4”-(2-methylbutyl) biphenyl-4′-carboxylate ”which is an example of the molecular structure of the smectic liquid crystal 31 is shown in the chemical formula (5). . Note that the pitch P is approximately 0.2 μm.

化学式（５）
また、可変焦点レンズの第２の変形例として、図８に示ように、カイラルコレステリック液晶４１を用いた可変焦点レンズ１ｂを構成することができる。 [Chemical formula 5]

Chemical formula (5)
As a second modification of the variable focus lens, as shown in FIG. 8, a variable focus lens 1b using a chiral cholesteric liquid crystal 41 can be configured.

  In the chiral cholesteric liquid crystal 41, the alignment direction of the liquid crystal molecules is parallel to the lens surface in each layer, the azimuth angle is a period P, and changes in a spiral in the Z-axis direction. In this state, equations (1) to (30) apply.

  When a voltage is applied, the orientation of the liquid crystal molecules disappears as shown in FIG. 9, and the focal length changes.

  Note that the chiral cholesteric liquid crystal has a selective reflection property and totally reflects right or left circularly polarized light in the vicinity of the wavelength λs = Pn ′. FIG. 10 shows an example of measured values of the reflectance of the chiral cholesteric liquid crystal with respect to natural polarization.

  Therefore, it is desirable that the wavelength λs is outside the wavelength range of the light used in the variable focus lens 1b. In other words, it is necessary for Pn ′ to be outside the wavelength range of light using the variable focus lens 1b in order to obtain a liquid crystal lens with better transmittance and no coloration.

If it ’s visible light,
[Formula 34]
Pn ′ <0.4μ (34)
It is necessary to be.

  Note that selective reflection may occur even in the chiral smectic C-phase liquid crystal of FIG. 5, which is the first modification described above, and for the above reason, the equation (34) is also applied to the example of FIG.

As a design example of the variable focus lens 1b using the chiral cholesteric liquid crystal 41,
d = 15 μ
ne-no = 0.4
λ = 0.45μ
P = 0.01μ
n ′ = 1.7
Then,
Γ / 2Φ = π · 0.4 × 0.01 / 0.45 = 0.0089π
Thus, Expression (26), Expression (28), Expression (29), and Expression (30) are satisfied, and since Pn ′ = 0.17μ, Expression (34) is also satisfied.

  Chemical formula (6) is an example of chiral cholesteric liquid crystal, and is a chemical formula of cholesterol benzoate.

化学式（６）
また、可変焦点レンズの第３の変形例として、図１１に示ように、ディスコチック液晶５１を用いてもよく、電圧が加わると、図１２のようにディスコチック液晶５１の配向が変り、凸レンズとしての焦点距離が長くなる。つまり、ディスコチック液晶５１は、図１３に示す屈折率楕円体のように、負の１軸性結晶であるので、凸レンズとしての焦点距離が長くなるのである。 [Chemical 6]

Chemical formula (6)
As a third modification of the variable focus lens, a discotic liquid crystal 51 may be used as shown in FIG. 11, and when a voltage is applied, the orientation of the discotic liquid crystal 51 changes as shown in FIG. As a result, the focal length becomes longer. That is, since the discotic liquid crystal 51 is a negative uniaxial crystal like the refractive index ellipsoid shown in FIG. 13, the focal length as a convex lens becomes long.

  In this case, when FIG. 12 is viewed from the Z direction, if the molecules of the discotic liquid crystal 51 are not oriented in one direction as shown in FIG. 14 or FIG. The array need not draw a helix. Therefore, the expressions (1) to (30) may not be satisfied.

This is common to the variable focus lens described in the present embodiment, each modified example, and other embodiments described later. However, it is blurred that the helical pitch P is smaller than the wavelength λ of the light used. For example, in the case of visible light, in an optical device used with 0.4 μ <λ <0.7 μ,
[Equation 35]
0.0001μ <P <0.4μ (35)
Is a desirable condition. [Equation 36] to further reduce blur
0.0001μ <P ≦ 0.2μ (36)
It is desirable that The lower limit of P is determined from the size of the liquid crystal molecules themselves.

  In the present embodiment and each modification, an electric field has been used to change the alignment of each liquid crystal. However, the present invention is not limited to this, and a coil 55 and an iron core 56 are used as shown in FIG. For example, the magnetic field H may be applied to the chiral cholesteric liquid crystal 41 to change it. FIG. 16 shows an example of a variable focal lens of the chiral cholesteric liquid crystal 41, but the present invention may be applied to a variable focal lens of the chiral nematic liquid crystal 2 or the chiral smectic liquid crystal 31.

  In order to change the orientation of each liquid crystal, as shown in FIG. 17, for example, the orientation of the chiral cholesteric liquid crystal 41 may be changed by changing the temperature using a heater 58. The present invention can also be applied to variable focus lenses such as liquid crystal, chiral nematic liquid crystal 2, or chiral smectic liquid crystal 31. In this configuration, changing the temperature causes a phase transition in the liquid crystal and changes the focal length of the lens. The lens is a Fresnel lens 60 and the power of the variable focus lens is increased without increasing the thickness of the liquid crystal. Here, the Fresnel lens 60 and the lens 5 may have an aspheric shape according to the application.

  FIG. 18 is a block diagram showing the configuration of a variable focus lens according to the second embodiment of the present invention.

  Since the second embodiment is almost the same as the first embodiment, only different points will be described, and the same components are denoted by the same reference numerals and description thereof will be omitted.

  In the second embodiment, a diffractive optical element (also referred to as DOE or HOE) is made of liquid crystal to form a variable focus lens.

  As shown in FIG. 18, the varifocal lens 61 of the second embodiment includes an alignment film between a lens 62 having a chiral nematic liquid crystal 2 coated with a transparent electrode film 3 on the inside and a parallel glass 63. 6 and is sealed with a sealing material 7.

The lens 62 has a Fresnel lens shape, but the concavo-convex portion is at the level of the wavelength of light, and the width W of one ring zone of the lens 62 is
[Equation 37]
W ・ θ = m ・ λ (37)
Decide on. Here, θ is the refraction angle of the light beam in the annular zone, and m is the diffraction order.

  When the refractive index of the chiral nematic liquid crystal 2 is changed by applying a voltage, the order of diffraction changes, so that the focal length of the variable focus lens 61 can be changed discontinuously.

［数３９］

［数４０］
ｍ1 ≠ｍ2 （４０）
となる。 In other words, if the jagged height of a certain annular zone is h and the refractive index of the lens 62 is ng,
[Equation 38]

[Equation 39]

[Equation 40]
m1 ≠ m2 (40)
It becomes.

  However, when m1 and m2 are different integers, if h, m1, m2, n ', no and ng satisfy the expressions (38) to (40), the variable focus lens 61 has the order m1. With m 2, a diffractive optical element with optimized diffraction efficiency is obtained.

  The focal length is changed to f1 / m1 and f1 / m2 depending on whether the switch 9 is turned on or off. Here, f1 is the focal length of the first-order diffractive optical element. In practice, the expressions (38) and (39) may be satisfied approximately.

  Hereinafter, application examples of the above-described embodiments and their modifications will be described.

  As shown in FIG. 19, an electronic endoscope 71 as a first device using the variable focus lens of each of the above-described embodiments and modifications thereof is a light guide 72 that transmits illumination light to be irradiated to a subject. The illumination lens 73 is irradiated with the illumination light from the illumination lens 73, and the subject image is incident through the objective lens 74. A variable focus lens 75 is disposed in the vicinity of the diaphragm 76, and an image is formed on the imaging surface of the CCD 78 by the optical lens 77, signal processing is performed by the signal processing device 79, and a subject image is displayed on the monitor 80. In this configuration, the variable focus lens 75 is used for focus adjustment, and realizes an electronic endoscope having an autofocus function.

  Further, in the second apparatus using the variable focus lens according to the above-described embodiment and each modification thereof, as shown in FIG. An imaging device 89 for processing and displaying a subject image on a monitor 84, and two variable focus lenses 85 and 86 are provided between an objective lens 81 and a CCD 83 via a diaphragm 88, and the focal length is changed in conjunction with the objective lens 81 and the CCD 83. By doing so, both zooming and focusing are realized. These are actually used in an electronic camera, a TV camera, and the like, and driving of the variable focus lenses 85 and 86 is performed by a control circuit 87 so as to perform zooming while focusing.

  In FIG. 20, the variable focus lenses 85 and 86 are concave and convex lenses, respectively, but may be convex or convex or a combination of convex and concave lenses.

  FIG. 21 shows another application example of the liquid crystal satisfying the expression (1), which is an example used for the diaphragm 91 of the optical system.

  The diaphragm 91 has a structure sandwiched between transparent members 92 and 93 made of a transparent material that seals the chiral nematic liquid crystal 2 that is the liquid crystal satisfying the formula (1). The cross-sectional shape of the contacting part is a sawtooth shape or a triangle. The diaphragm 91 has a rotationally symmetric shape with respect to the optical axis.

  In FIG. 21, the light beam a incident on the center of the diaphragm 91 from the left and right passes through as it is, but the light beam b incident on the peripheral part is totally reflected by the boundary surface between the chiral nematic liquid crystal 2 and the transparent member 93 to the side. The diaphragm 91 is bent and cannot pass through the diaphragm 91, and the diaphragm 91 is in a narrowed state.

In FIG. 22, the chiral nematic liquid crystal 2 is in a homeotropic orientation when a voltage is applied to the diaphragm 91, so that the light beam b goes straight without being totally reflected at the boundary surface between the transparent member 93 and the chiral nematic liquid crystal 2. However, the effective diameter of the diaphragm is wider than that in FIG. When the refractive index of the transparent member 93 is n93 [Equation 41]
0.8no <n93 <1.3no (41)
If so, the light beam b travels almost straight in the state of FIG.

である。 The condition for the total reflection of the light ray a in the state of FIG. 21 is as follows.
[Formula 42]

It is.

  Further, the chiral nematic liquid crystal 2 may satisfy the formula (26), the formula (28), the formula (29), or the formula (30) practically instead of the formula (1).

  As the liquid crystal, in addition to the chiral nematic liquid crystal 2, the above-described chiral smectic liquid crystal 31, chiral cholesteric liquid crystal 41, discotic liquid crystal 51, and polymer dispersed liquid crystal or polymer liquid crystal in which liquid crystal is dispersed in a polymer. Etc. can also be used. In the case of the chiral smectic liquid crystal 31 or the chiral cholesteric liquid crystal 41, it is more preferable that the formula (34) is also satisfied. Moreover, although it can be said that it is common to all the liquid crystals, it is better if the expressions (35) and (36) are satisfied.

  FIG. 23 shows an example of the second diaphragm 101 using the chiral nematic liquid crystal 2. A difference from the diaphragm 91 of FIG. 21 is that the periphery of the transparent member 102 in place of the transparent member 93 is a DOE (diffractive optical element), and the periphery of the transparent member 102 has a wavelength λ of light to be used. That is, it has a saw blade shape.

In the state of FIG. 23, [Equation 43]
no <n102 (43)
Therefore, the light b1 and b2 in the peripheral portion are bent outward by diffraction, absorbed by the light absorbing material 103, and not transmitted to the rear of the diaphragm 101. Note that n102 is the refractive index of the transparent member 102.

Since FIG. 23 shows the state when the voltage is turned off, the liquid crystal has a chiral nematic arrangement [Equation 44].
0.9n '<n102 <1.2n' (44)
Therefore, b1 and b2 are almost straight and operate as a state where the aperture is substantially open.

  As the shape of the DOE, in order to further improve the operation as a diaphragm by determining the refraction angle θ in Expression (37) and increasing the diffraction efficiency, it is more preferable to satisfy Expression (38) to Expression (40) ( However, ng is replaced with n102).

  As the liquid crystal, in addition to the chiral nematic liquid crystal 2, the above-described chiral smectic liquid crystal 31, chiral cholesteric liquid crystal 41, discotic liquid crystal 51, polymer dispersed liquid crystal in which liquid crystal is dispersed in a polymer, polymer liquid crystal, or the like is also used. Can do. In the case of the chiral smectic liquid crystal 31 or the chiral cholesteric liquid crystal 41, it is more preferable that the formula (34) is also satisfied.

  The liquid crystal needs to satisfy the formula (1). However, in practice, the formula (26), the formula (28), the formula (29), or the formula (30) may be satisfied instead of the formula (1).

  If the transparent member 92 is also a DOE, a larger refraction angle can be obtained, and a high performance aperture can be obtained.

  Note that the voltage applied to the diaphragm 101 may be continuously variable, and in that case, the diaphragm in which the transmittance around the diaphragm 101 continuously changes is convenient.

  The diaphragms 91 and 101 can be used for the diaphragm 76 of the electronic endoscope 71 in FIG. 19, the diaphragm 88 of the imaging device 80 in FIG. Since the electronic endoscope 71 and the imaging device 80 always include a power source, the power source can be used also for a liquid crystal element, which is convenient.

  Further, if the aperture 101 has no A portion at the center of the transparent member 102 and has a saw-tooth shape on the entire surface, an aperture capable of changing the amount of light can be obtained without changing the beam diameter. In order to have an effect similar to that of the optical element with variable transmitted light amount, one of the expressions (38) and (39) is preferably satisfied approximately, and the expressions (38) and (39) are simultaneously satisfied. It is better not to be satisfied (equation (40) needs to be satisfied).

  For example, if the equation (38) is completely seen and the equation (39) is incomplete, the light of the order m1 is different in both states of FIGS. The diaphragm 101 operates as a density variable filter for m1 light.

  Further, when both the expressions (38) and (39) are observed, the diaphragm 101 operates as an optical shutter for the light of the following expression m1 or m2. Even in this case, if the voltage is continuously changed from the state shown in FIG. 23 to FIG. 24, ne in the equations (38) and (39) can be replaced by ne ′ that continuously changes. It can be operated as a variable optical element (note that it is necessary to consider equation (2)).

  FIG. 25 is an example of a variable prism (or variable optical deflector) 111 using liquid crystal satisfying any one of formula (1), formula (26), formula (28), formula (29), and formula (30). is there.

  In this variable prism 111, as shown in FIG. 25, the chiral nematic liquid crystal 2 is disposed between the transparent member 112 and the transparent member 113 having a wedge shape or a saw blade shape. For example, if the refractive index of the transparent member 112 is made equal to the refractive index n ′ of the chiral nematic liquid crystal 2, the light from the left and right in FIG.

  Here, when a voltage is applied to the variable prism 111, the alignment of the liquid crystal becomes homeotropic as shown in FIG. 26, and the refractive index of the chiral nematic liquid crystal 2 falls to no, so that the light is refracted to the upper right. If the voltage is continuously variable, the light refraction angle changes continuously, which is convenient.

  As the liquid crystal, in addition to the chiral nematic liquid crystal 2, the above-described chiral smectic liquid crystal 31, chiral cholesteric liquid crystal 41, discotic liquid crystal 51, polymer dispersed liquid crystal in which liquid crystal is dispersed in a polymer, polymer liquid crystal, or the like is also used. be able to. In the case of the chiral smectic liquid crystal 31 or the chiral cholesteric liquid crystal 41, it is more preferable that the formula (34) is also satisfied.

  A variable prism can also be obtained by making the shape of the saw blade fine and using the transparent member 112 as a diffractive optical element. At this time, it is preferable to satisfy Expression (37), and if Expression (38), Expression (39), and Expression (40) are satisfied, an optical element having a high aperture effect can be obtained (in this case, ng Represents the refractive index of the transparent member 112).

  The variable prism 111 can be used for electronic cameras, TV cameras, film cameras, binoculars, and the like for preventing blurring.

  By the way, the principle of the spatial modulation of light rays used in the diaphragms 91 and 101 and the variable prism 111 can be used for a display.

  FIG. 27 is an example of the display 121 using liquid crystal satisfying any one of the formula (1), the formula (26), the formula (28), the formula (29), and the formula (30).

  In this display 121, as shown in FIG. 27, a liquid crystal 124 is disposed between a transparent member 122 having a saw-tooth shaped cross section and a transparent member 123. It is assumed that the refractive index of the transparent member 122 is substantially equal to n ′. In the liquid crystal 124, a variable voltage is applied to a desired pixel by the individual electrode 125, and the light from the lamp 126 is sequentially transmitted through the transparent member 123, the liquid crystal 124, and the transparent member 122 through the color filter 127. It is like that.

  In the display 121 configured as described above, for example, in a pixel to which no voltage is applied, such as the pixel A, the arrangement of the liquid crystal 124 is twisted nematic, so the light from the lamp 125 goes straight, so the pixel looks bright.

  Further, in a pixel to which a high voltage is applied such as the B pixel, the arrangement of the liquid crystal 124 is homeotropic, so that the light from the lamp 125 is strongly refracted by the transparent member 122 and appears dark to the human eye.

  When an intermediate voltage is applied as in the C pixel, the light from the lamp 125 is refracted in the middle between A and B, so it looks somewhat bright to the human eye. The feature is that it is bright because a polarizing plate is not used unlike a normal display.

  FIG. 28 shows an example of a reflective display 130 that uses a reflector 131 instead of the lamp 125.

  In the reflective display 130, as shown in FIG. 28, the incident light is reflected and appears bright in a pixel such as the pixel A to which no voltage is applied. In addition, since a voltage is applied to the pixel B, the incident light is refracted, and is eventually absorbed and scattered so that it looks dark. For pixel C, it is in the middle.

  In addition to these displays that change the refractive power of light, a type that uses total reflection, such as the diaphragm 91 described above, and a type that uses a diffractive optical element, such as the diaphragm 101, can be considered in order to realize brightness and darkness of the pixels.

  In addition to the chiral nematic liquid crystal 2, the liquid crystal used in the above display examples is a chiral smectic liquid crystal 31, a chiral cholesteric liquid crystal 41, a discotic liquid crystal 51, and a polymer dispersed liquid crystal or polymer in which the liquid crystal is dispersed in a polymer. A liquid crystal or the like can also be used.

  The liquid crystal used for the display may satisfy one of formula (1), formula (26), formula (28), formula (29), and formula (30). In the case of the chiral smectic liquid crystal 31 or the chiral cholesteric liquid crystal 41, it is more preferable that the formula (34) is also satisfied.

  In the diaphragm diffractive optical element, prism, and display device using the liquid crystal described above, when the wavelength of the light used is visible light, higher performance can be achieved by satisfying Expression (35) or Expression (36). Can be obtained.

  In addition, if the infrared cut filter effect is given to the liquid crystal used in each of the above embodiments by mixing an infrared absorbing substance, the infrared cut filter can be omitted when used in an electronic imaging system used for visible light, and the cost is reduced. It is advantageous for reduction and space saving. In the case of an imaging system in which the light used is not visible light, a filter can be omitted by mixing a substance that cuts non-observation light into the liquid crystal, and the same effect is obtained.

In the optical element having the variable characteristics using the liquid crystal in each of the above embodiments, it is ideal that the expression (1) is satisfied, but the expression (1) is not always satisfied when used in an actual product. If you do not need to be so precise,
[Equation 45]
P <λ (45)
If it is good.

If you want a little higher accuracy,
[Equation 46]
P <λ / 2 (46)
It is even better when is satisfied.

In illumination systems, low-cost optical devices, etc.
[Equation 47]
P <2λ (47)
But it can be practical.

  Note that when the discotic liquid crystal 51 is used, there is a case where the formula (45), the formula (46), or the formula (47) may not be satisfied.

  In all the embodiments described so far, in addition to the chiral nematic liquid crystal 2, the liquid crystal is a chiral smectic liquid crystal 31, a chiral cholesteric liquid crystal 41, a discotic liquid crystal 51, and a polymer dispersion in which the liquid crystal is dispersed in a polymer. A liquid crystal, a polymer liquid crystal, or the like can also be used.

[Appendix]
(Additional Item 1) A liquid crystal is sealed in a space formed by a pair of members, and an optical characteristic variable that changes the optical characteristics of the liquid crystal by controlling the alignment state of the liquid crystal molecules of the liquid crystal by an external physical action. In the optical element,
The optical characteristic variable optical element, wherein the liquid crystal has a smaller twist pitch than the wavelength of light transmitted through the liquid crystal.

(Additional Item 2) The variable optical property optical element according to Additional Item 1, wherein the optical characteristic variable optical element is a variable focus lens that varies a focal length of the liquid crystal.

(Additional Item 3) The optical property variable optical element according to Additional Item 1, wherein the optical characteristic variable optical element is a diaphragm for changing a transmitted light amount of the liquid crystal.

(Additional Item 4) The variable optical property optical element according to Additional Item 1, wherein the optical characteristic variable optical element is a prism that changes a transmission direction of transmitted light of the liquid crystal.

(Additional Item 5) One of the pair of members is a diffractive member,
The optical characteristic variable optical element according to Additional Item 1, wherein the optical characteristic variable optical element is a diffraction element that changes a diffraction efficiency of the diffraction member by changing a focal length of the liquid crystal.

(Additional Item 6) Liquid crystal is sealed in a space formed by a pair of members, and the alignment state of the liquid crystal molecules of the liquid crystal is controlled by a physical action from the outside, and the optical characteristic variable for changing the optical characteristic of the liquid crystal. In a display device including an optical element,
The display device, wherein the liquid crystal has a smaller twist pitch than the wavelength of light transmitted through the liquid crystal.

(Additional Item 7) According to the additional items 1 to 6, wherein at least one of Expression (28), Expression (29), Expression (30), Expression (45), Expression (46), and Expression (47) is satisfied. The optical property variable optical element or the display device according to any one of the above.

(Additional Item 8) As the liquid crystal, any one of a chiral nematic liquid crystal, a chiral cholesteric liquid crystal, a chiral smectic liquid crystal, a polymer liquid crystal, a liquid crystal dispersed in a polymer, and a discotic liquid crystal is used. Item 8. The optical property variable optical element or the display device according to any one of Items 1 to 7.

(Additional Item 9) The optical characteristic according to any one of Additional Items 1 to 7, wherein P · n ′ is shorter than a wavelength of light to be used, and the liquid crystal is a chiral cholesteric liquid crystal or a chiral smectic liquid crystal. Variable optical element or display device.

(Additional Item 10) The optical property variable optical element or the display device according to any one of Additional Items 1 to 9, wherein the expression (35) or the expression (36) is satisfied.

(Additional Item 11) A diffractive optical element including the optical property variable optical element according to Additional Item 6, which satisfies formula (37).

(Additional Item 12) A diffractive optical element including the optical characteristic variable optical element according to Additional Item 6, which satisfies Expression (37), Expression (38), Expression (39), and Expression (40).

(Additional Item 13) A stop including the optical characteristic variable optical element according to any one of Additional Item 3 or Additional Items 7 to 10 that satisfies Formula (41) or Formula (42).

(Additional Item 14) A stop including the optical characteristic variable optical element according to any one of Additional Items 6 to 10 that satisfies Expression (37).

(Additional Item 15) A stop including the optical property variable optical element according to any one of Additional Items 6 to 10, which satisfies Expression (37), Expression (38), Expression (39), and Expression (40).

(Additional Item 16) A diffractive optical element including the optical property variable optical element according to any one of Additional Items 6 to 10 that satisfies Formula (43) or Formula (44).

(Additional Item 17) An optical element having variable characteristics made of a discotic liquid crystal (Appendix Item 18) The external physical action is an action of changing at least one of an electric field, a magnetic field, and a temperature. Item 11. The optical property variable optical element or the display device according to any one of Items 1 to 10.

(Additional Item 19) An optical element capable of changing the amount of transmitted light that satisfies at least one of Expression (28), Expression (29), Expression (30), Expression (45), Expression (46), and Expression (47).

(Additional Item 20) The optical element with variable transmitted light amount according to Additional Item 19, which satisfies at least one of Expression (38) or Expression (39) and Expression (40).

(Additional Item 21) An electronic imaging apparatus using the optical element according to Additional Items 1 to 20.

(Additional Item 22) A reflective display device using the optical elements of Additional Items 6 to 10.

1 is a configuration diagram showing a basic configuration of a variable focus lens according to a first embodiment of the present invention. Diagram showing the refractive index ellipsoid of the chiral nematic liquid crystal molecule in FIG. Explanatory drawing explaining the effect | action of the variable focus lens of FIG. Configuration diagram showing a specific configuration of the variable focus lens of FIG. The figure which shows the liquid crystal molecular arrangement | sequence of the chiral smectic C phase of the chiral smectic liquid crystal used for the 1st modification of the variable focus lens of FIG. The block diagram which shows the structure of the variable focus lens using the chiral smectic liquid crystal of FIG. Explanatory drawing explaining the effect | action of the variable focus lens of FIG. 1 is a configuration diagram showing the configuration of a second modification of the variable focus lens of FIG. 1 using chiral cholesteric liquid crystal. Explanatory drawing explaining the effect | action of the variable focus lens of FIG. The figure which shows the measured value of the reflectance of the chiral cholesteric liquid crystal of FIG. Configuration diagram showing a configuration of a second modification of the variable focus lens of FIG. 1 using a discotic liquid crystal. Explanatory drawing explaining the effect | action of the variable focus lens of FIG. The figure which shows the refractive index ellipsoid of the molecule | numerator of the discotic liquid crystal of FIG. First view when the discotic liquid crystal of FIG. 12 is viewed from the Z direction. The second figure when the discotic liquid crystal of FIG. 12 is viewed from the Z direction. 1 is a configuration diagram showing the configuration of a variable focus lens that uses a magnetic field to change the alignment of the chiral nematic liquid crystal in FIG. 1 is a configuration diagram showing a configuration of a variable focus lens using temperature change to change the alignment of the chiral nematic liquid crystal of FIG. The block diagram which shows the structure of the variable focus lens which concerns on the 2nd Embodiment of this invention. The block diagram which shows the structure of the 1st apparatus provided with the variable focus lens of each embodiment. The block diagram which shows the structure of the 2nd apparatus provided with the variable focus lens of each embodiment. The block diagram which shows the structure of the 1st application example to which the variable focus lens of each embodiment is applied. Explanatory drawing explaining the effect | action of the 1st application example of FIG. The block diagram which shows the structure of the 2nd application example to which the variable focus lens of each embodiment is applied. Explanatory drawing explaining the effect | action of the 2nd application example of FIG. The block diagram which shows the structure of the 3rd application example to which the variable focus lens of each embodiment is applied. Explanatory drawing explaining the effect | action of the 3rd application example of FIG. The block diagram which shows the structure of the 4th application example to which the variable focus lens of each embodiment is applied. The block diagram which shows the structure of the 5th application example to which the variable focus lens of each embodiment is applied. Configuration diagram showing the configuration of a conventional variable focus lens Explanatory drawing explaining the effect | action of the variable focus lens of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Variable focus lens 2 ... Chiral nematic liquid crystal 3 ... Transparent electrode film 4 ... Flat glass 5 ... Lens 6 ... Orientation film 7 ... Sealing material 8 ... AC power supply 9 ... Switch 21 ... Variable resistance

Claims (20)

In an optical property variable optical element that encloses liquid crystal in a space formed by a pair of members, controls the alignment state of liquid crystal molecules of the liquid crystal by an external physical action, and changes the optical properties of the liquid crystal.
The liquid crystal is at least

An optical property variable optical element characterized by satisfying any one of the above.
However,
P is the twist pitch of the liquid crystal,
λ is the wavelength of the incident light,
Γ is

Where ne is the refractive index for polarized light in the liquid crystal molecule long axis direction, n0 is the refractive index for polarized light in the liquid crystal molecule short axis direction, d is the thickness of the liquid crystal,
φ is

It is. 2. The optical characteristic variable optical element according to claim 1, wherein P · n ′ is out of a range of a wavelength of light to be used.
Where n 'is

P is the twist pitch of the liquid crystal.   The optical property variable optical element according to claim 1, wherein the optical property variable optical element is a variable focus lens that changes a focal length of the liquid crystal.   The optical property variable optical element according to claim 1, wherein the optical property variable optical element is a stop for changing a transmitted light amount of the liquid crystal.   The optical property variable optical element according to claim 1, wherein the optical property variable optical element is a prism that changes a transmission direction of transmitted light of the liquid crystal. One of the pair of members is a diffractive member,
2. The optical property variable optical element according to claim 1, wherein the optical property variable optical element is a diffraction element that changes a diffraction efficiency of the diffraction member by changing a focal length of the liquid crystal. In an optical property variable optical element that encloses liquid crystal in a space formed by a pair of members, controls the alignment state of liquid crystal molecules of the liquid crystal by an external physical action, and changes the optical properties of the liquid crystal.
The liquid crystal is at least

Satisfy any one of
The optical characteristic variable optical element is a variable focus lens that varies a focal length of the liquid crystal,
An optical property variable optical element characterized by satisfying the following condition (31):
2μ <d <300μ (31)
However,
P is the twist pitch of the liquid crystal,
λ is the wavelength of the incident light,
Γ is

Where ne is the refractive index for polarized light in the liquid crystal molecule long axis direction, n0 is the refractive index for polarized light in the liquid crystal molecule short axis direction, d is the thickness of the liquid crystal,
φ is

It is.   A display device comprising the optical property variable optical element according to claim 1. A liquid crystal is sealed in a space formed by a pair of members, and includes an optical property variable optical element that controls the alignment state of the liquid crystal molecules of the liquid crystal by an external physical action and changes the optical properties of the liquid crystal. In the display device,
The liquid crystal is at least

A display device characterized by satisfying any one of the above.
However,
P is the twist pitch of the liquid crystal,
λ is the wavelength of the incident light,
Γ is

Where ne is the refractive index for polarized light in the liquid crystal molecule long axis direction, n0 is the refractive index for polarized light in the liquid crystal molecule short axis direction, d is the thickness of the liquid crystal,
φ is

It is. 10. The display device according to claim 8, wherein P · n ′ is outside the wavelength range of light to be used, and the liquid crystal is a chiral cholesteric liquid crystal or a chiral smectic liquid crystal.
Where n 'is

It is.   The display device according to claim 8, wherein the formula 0.0001 μm <P <0.4 μm or the formula 0.0001 μm <P ≦ 0.2 μm is satisfied. The optical characteristic variable optical element according to claim 6, wherein the diffractive element satisfies the formula W · θ = m · λ.
Where W is the width of the annular zone of the full-nel lens shape, θ is the refraction angle at the annular zone of the full-nel lens shape, m is the diffraction order (integer), and λ is the wavelength of the incident light. The diffraction element has the formula W · θ = m · λ,

The optical characteristic variable optical element according to claim 6, wherein the expression m1 ≠ m2 is satisfied.
Where n 'is

W is the width of the annular zone of the full-nel lens shape, θ is the refraction angle at the annular zone of the full-nel lens shape, m is the diffraction order (integer), λ is the wavelength of the incident light, m1 and m2 are the diffraction orders (integer) , Ng is the refractive index of the lens when the member on the incident side of the pair of members forming the space for enclosing the liquid crystal is a lens, and the surface of the lens in contact with the liquid crystal has a concave-convex shape. The aperture is of the formula 0.8no <n <1.3no or

The optical property variable optical element according to claim 4, wherein:
However, n is the refractive index of the transparent member which has a saw-tooth shaped uneven surface. The optical characteristic variable optical element is a stop for changing the amount of light transmitted through the liquid crystal, and the stop has the formula 0.8no <n <1.3no or

The display device according to claim 9, wherein:
However, n is the refractive index of the transparent member which has a saw-tooth shaped uneven surface. 5. The optical property variable optical element according to claim 4, wherein the optical property variable optical element is a diaphragm for varying a transmitted light amount of the liquid crystal, and the diaphragm satisfies a formula W · θ = m · λ. .
Here, W is the width of the annular zone of the full-nel lens shape, θ is the refraction angle at the annular zone of the full-nel lens shape, m is the diffraction order (integer), and λ is the wavelength of the incident light. One of the pair of members is a diffractive member,
The optical characteristic variable optical element is a diffractive element that changes the diffraction efficiency of the diffractive member by changing the focal length of the liquid crystal, and the diffractive element has the formula no <n or the formula 0.9n ′ <n <. The display device according to claim 9, wherein 1.2n ′ is satisfied.
Where n 'is

n0 is a refractive index with respect to polarized light in the minor axis direction of the liquid crystal molecule, n is a pair of members forming a space for enclosing the liquid crystal, and the surface of the transparent member on the emission side that touches the liquid crystal has a sawtooth-shaped unevenness. The refractive index of the transparent member on the emission side when a diffractive optical element is formed.   An optical characteristic variable optical element comprising a discotic liquid crystal and a driving device for driving the discotic liquid crystal.

Any one of the optical characteristic variable optical elements with variable transmission light quantity, characterized by satisfying any one of the above.
However,
P is the twist pitch of the liquid crystal,
λ is the wavelength of the incident light,
Γ is

Where ne is the refractive index for polarized light in the liquid crystal molecule long axis direction, n0 is the refractive index for polarized light in the liquid crystal molecule short axis direction, d is the thickness of the liquid crystal,
φ is

It is.

Or

20. The variable optical property variable optical element according to claim 19, wherein at least one of the following expression is satisfied: m1 ≠ m2.
Where n 'is

m1 and m2 are diffraction orders (integers), ng is a lens on the incident side of a pair of members forming a space for enclosing liquid crystal, and the surface of the lens in contact with the liquid crystal has a rugged lens shape. The refractive index of the lens.

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