JPH06194695A - Optical deflector - Google Patents

Abstract

PURPOSE:To obtain the deflector optical which obtains an extended angle of deflection than the conventional by making incident light, transmitted through a polarizing plate, incident on an incidence surface from one direction and making the normal of the incidence surface unmatch with the incidence direction. CONSTITUTION:This optical deflector is equipped with a wedge type or Fresnel type liquid crystal prism where the incident light transmitted through the polarizing plate is made incident on the incidence surface from the one direction and the emission light is emitted from the emission surface in a direction deflected from the incidence direction. Then the normal of this incidence surface does not match the incidence direction. The wedge type liquid crystal prism is made with 1st and 2nd flat plate shaped transparent substrates 1 and 2 joined at a prescribed vertex angle alpha deg. with a sealant, forming 1st and 2nd transparent conductive films on the inner surfaces of the 1st and 2nd transparent substrates 1 and 2, and further 1st and 2nd horizontal orientation films on the inner surfaces of the 1st and 2nd transparent conductive films are formed. Then nematic liquid crystal 3 having positive dielectric anisotropy is sealed in the wedge shaped space partitioned with the 1st and 2nd transparent substrates 1 and 2.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an optical deflector. This optical deflector can be used for various displays such as a display unit of a computer, a laser printer, a laser radar and the like.

[0002]

2. Description of the Related Art For example, as a wedge type liquid crystal prism, FIG.
The one shown in 9 is known. In this wedge-shaped liquid crystal prism, flat plate-shaped first and second transparent substrates 91 and 92 are joined by a sealant 93 at a predetermined apex angle α (°), and the inner surfaces of the first and second transparent substrates 91 and 92 are First and second transparent conductive films 94 and 95 are formed, and first and second horizontal alignment films 96 and 96 are formed on the inner surfaces of the first and second transparent conductive films 94 and 95, respectively.
97 is formed. Then, each of the first and second transparent substrates 9
A nematic liquid crystal 98 having a positive dielectric anisotropy is enclosed in a wedge-shaped space defined by 1 and 92.

A wedge-shaped liquid crystal prism of this kind is incorporated as a light deflector together with a polarizing plate 99 and the like, and a voltage exceeding the threshold voltage is applied between the first and second transparent conductive films 94 and 95 by the AC power source 8.
When 0 is applied, the liquid crystal 98 loses the balance between the elastic energy and the electric field effect, and starts to be deflected from the central portion where the elastic energy is small. Here, if the incident light Bi transmitted through the polarizing plate 99 is perpendicularly incident on the incident surface 91a of the first transparent substrate 91, the emitted light Bo is emitted as the outgoing surface 92a of the second transparent substrate 92.
To the direction perpendicular to the vertical direction by θ (°). That is, since the movement of the liquid crystal molecules is accompanied by a change in birefringence, the deflection angle θ (°) formed by the incident light Bi and the outgoing light Bo is the difference in birefringence. The difference between the deflection angle and the birefringence has an important effect when the liquid crystal prism is used as a lens or the like (Journal of the Ophthalmological Society of Japan (1988), pages 30 to 33, "focal length variable liquid crystal lens").

[0004]

However, in the conventional optical deflector, since the incident light is always incident perpendicularly on the incident surface of the transparent substrate, the deflection angle is only a few degrees and the liquid crystal prism has It was one of the factors that reduced the utility value.
If the Fresnel type liquid crystal prism is regarded as a combination of a plurality of wedge type liquid crystal prisms, the same applies to an optical deflector using the Fresnel type liquid crystal prism. For example, in the above publication, in the case of a wedge-shaped liquid crystal prism having an apex angle α = 4.7 (°), the deflection angle is 3. by applying a voltage equal to or higher than the threshold voltage.
It is disclosed that it continuously changes in the range of 2 to 2.4 (°). It also discloses that in the case of a Fresnel type liquid crystal prism having an apex angle α = 20 (°), the deflection angle continuously changes in the range of 4 to 1 (°).

The present invention has been made in view of the above-mentioned conventional circumstances, and an object thereof is to provide an optical deflector capable of obtaining a deflection angle wider than that of the conventional one.

[0006]

In the optical deflector of the present invention, the incident light transmitted through the polarizing plate is incident on the incident surface from one direction,
An optical deflector having a wedge-type or Fresnel-type liquid crystal prism that emits outgoing light in a direction deflected from the outgoing surface with respect to the one direction, and a normal line of the incoming surface does not coincide with the one direction. It is characterized by.

[0007]

In the optical deflector of the present invention, the incident light transmitted through the polarizing plate is incident on the incident surface with an inclination, so that the emitted light emitted from the emitting surface is emitted in a state where the deflection angle is enlarged.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS This optical deflector incorporates the wedge type liquid crystal prism shown in FIG. 1 together with a polarizing plate and the like not shown. The wedge-shaped liquid crystal prism is similar to the above-mentioned conventional one, and the first and second flat plate-shaped transparent substrates 1 and 2 are joined by a sealant at a predetermined apex angle α (°) to form the first and second transparent substrates. First and second transparent conductive films (not shown) are formed on the inner surfaces of the transparent substrates 1 and 2, respectively, and first and second horizontal alignment films are further formed on the inner surfaces of the first and second transparent conductive films. . A nematic liquid crystal 3 having a positive dielectric anisotropy is enclosed in the wedge-shaped space defined by the first and second transparent substrates 1 and 2. A voltage exceeding the threshold voltage can be applied from the AC power supply between the first and second transparent conductive films.

In this optical deflector, the calculation method and the result of the relationship between the incident angle to the liquid crystal prism and the outgoing angle will be described. 1. Derivation of basic formula (1) Setting of symbols etc. As shown in Table 1, first and second transparent substrates 1 and 2 and liquid crystal 3
And the thicknesses of the first and second transparent substrates 1 and 2 are set.

[0010]

[Table 1] In addition, enter the following conditions in the figure.

PO: incident light x axis: axis within the plane of the first transparent substrate 1 perpendicular to the wedge top side y axis: axis within the plane of the first transparent substrate 1 parallel to the wedge top side z axis: first transparent substrate Axis H ₀ perpendicular to the 1st plane: incident angle with respect to z-axis (angle formed by one direction of incident light and incident plane determined by xy coordinates) D ₁ : 1st transparent substrate from P point Angle formed by the foot lowered to the x-axis (incident deflection angle) α: Wedge vertical angle However, the calculation range is as follows.

0 ≦ H ₀ <90 (°) 0 ≦ D ₁ <180 (°) (2) Optical path in the first transparent substrate 1 The incident point on the incident surface of the first transparent substrate 1 is (0, 0, 0). 2) and FIG. Where SNE
From the law of LL, sin H ₀ = n _K1 · sin H ₁ and coordinates (x, y, z)
Is (-T ₁ · tan H ₁ · cos D ₁ , T ₁ · tan H ₁ ·
sin D _1, a -T _1). (3) Optical Path in Liquid Crystal 3 The exit angle H ₂ to the liquid crystal 3 has the following relationship.

N _K1 · sin H ₁ = n _L · sin H ₂ Here, as shown in FIG. 4, the incident point P on the upper surface of the liquid crystal 3 is the origin, and the exit point from the liquid crystal 3 is O. Let N be the foot descended from the point P to the emission surface of the lower surface of the liquid crystal 3. Let l be the distance from point P to the top side. Let Q be a foot below the O point along the lower surface of the liquid crystal 3 with respect to the yz plane passing through the P point.

Accordingly, if the angle between the line segment connecting the N point and the (-1, 0, 0) point and the line segment ON is D ₄ , then D
₄ is the incident deflection angle with respect to the second transparent substrate 2. Then, when the light incident at the deflection angle D ₁ is incident on the second transparent substrate 2 from the lower surface of the liquid crystal 3, the incident angle H _{3 is} caused by the normal line PN.
Therefore, the traveling direction of light is bent from the D ₁ direction to the D ₄ direction.

The incident angle H ₃ on the second transparent substrate 2 will be determined below. From the relationship of FIG. 4, the direction cosine of the unit vector of the vector PO is (−sin H ₂ · cos D ₁ , sin H ₂ · sin
D ₁ , −cos H ₂ ) and the direction cosine of the unit vector of the vector PN is (−sin α, 0, −cos α).

Therefore, the incident angle H ₃ is cos H ₃ = si
It is expressed as n H ₂ · cos D ₁ · sin α + cos α · cos H ₂ . Next, the deflection angle D ₄ upon incidence on the second transparent substrate 2 is obtained. 5 and 6 show the positional relationship in the cross section. In FIG. 5, RO is a projection on the second transparent substrate 2 when passing through the liquid crystal 3.
As described above, the deflection angle at the time of incidence on the first transparent substrate 1 is expressed as shown in the figure, and it can be seen that it is twisted.

When the coordinates of the P point are (0,0,0) and the coordinates of the O point are (x, y, z), the coordinates of the R point are (0,0,-).
The coordinates of tan α) and Q point are (0, y, −tan α), and the coordinates of T point are (0, y, z).

The length of TQ is -tan α-z, OT
Is x, and the length of OQ is (x ² + (tan α + z)
² ) ^1/2 , the length of NR is sin α · tan α.

Therefore, tan D ₄ = RQ / OU = y / ((x ² + (tan α + z)
² ) ^1/2 −sin α · tan α). Next, the coordinates (x, y, z) of the O point are obtained. The equation of the lower surface of the liquid crystal 3 (upper surface of the second transparent substrate 2) is z + tan α = −tan α · x. The equation of the line segment PO is x / (− sin H ₂ · cos D ₁ ) = y / (sin H ₂ · sin D ₁ = z / (− cos H ₂ ) = t with t as a parameter. , T = tan α / (cos H ₂ + tan α ・
sin H ₂ · cos D ₁ ) is obtained. The coordinates (x, y, z) are given as described above.

Further, tan D _4, from 5, taking into account the sign _{tan D 4 = y · cos α} / (- x-sin 2 α) can be written as. (4) Optical Path Below Second Transparent Substrate 2 The exit angle H ₄ into the second transparent substrate 2 is expressed as n _L · sin H ₃ = n _K2 · sin H ₄ .

Assuming that the point of incidence on the second transparent substrate 2 is the origin, the coordinates (x, y, z) of the point of emission are (-T ₂ ·. tan H ₄・ cos
D ₄ , T ₂ · tan H ₄ · sin D ₄ , −T ₂ ). Since these coordinates are rotated by α with respect to the coordinate system having the origin at the point O in FIG. 4, the coordinate system is converted around the y-axis passing through the point O with reference to FIG. 7.

The chord length r is r = (x ² + z ² ) ^1/2 ,
The deflection angle θ is θ = tan ⁻¹ (z / x), and from these, the coordinates (x, y, z) of the emission point are ((x ² + z ² ) ^1/2 · cos (θ−α), y , (X ² +
z ² ) ^1/2 · sin (θ-α)).

From the inside of the second transparent substrate 2, the deflection angle is D ₄
It does not change. Further, the exit angle H ₅ from the second transparent substrate 2 into the air is expressed as sin H ₅ = n _K2 · sin H ₄ . Thus, the incident angle H ₀ , the deflection angle D ₁ and the apex angle α
The exit position H ₅ , the exit angle H ₅ and the deflection angle D ₄ of the liquid crystal prism were determined. (5) Direction of outgoing light viewed from incident light In order to find the direction of outgoing light viewed from incident light, the PO axis corresponding to the incoming light is set as a new X axis, and the coordinate system is converted as shown in FIG.

Here, the Y axis is in the xy plane. The unit vector in the x-y-z coordinate system of the vector PO that is the X axis is (sin H ₀ · cos D ₁ , −sin H ₀ · sin D ₁ ,
cos H ₀ ), similarly, the Y-axis and Z-axis unit vectors are (sin D ₁ , cos D ₁ , 0) and (−cos H ₀ · cos, respectively).
D ₁ , cos H ₀ · sin D ₁ , sin H ₀ ).

By the way, the second tilted by α in the xz plane
X ^* axis transparent substrate 2 side, taking Z ^* axis perpendicular thereto. This is shown in FIG. When the unit vector of the X ^* , y, Z ^* axes is expressed in the xyz plane, the unit vector of the X ^* axis is (cos α, 0, −sin α), and the unit vector of the y axis is (0 , 1, 0) The unit vector of the Z ^* axis becomes (sin α, 0, cos α).

Further, FIG. 10 shows the emission position relationship on the X ^* -Z ^* plane. The unit vector (X ^* , y, Z ^* ) of the light emitted from the liquid crystal prism is (−sin H ₅ · cos D ₄ ,
sin H ₅ · sin D ₄ , −cos H ₅ ). Therefore, in consideration of the relationship from FIG. 9, the unit vector (X ^* ,
y, Z ^* ) is expressed in x-y-z system coordinates as follows: x = X ^* · cos α + Z ^* · sin α y = sin H ₅ · sin D ₄ z = −X ^* · sin α + Z ^* · cos α Becomes

Similarly, from the relationship shown in FIG.
When the −z system coordinate is expressed by the aimed XYZ system coordinate, X = x · sin H ₀ · cos D ₁ −y · sin H ₀ · sin D ₁ + z · cos H ₀ Y = x · sin D a _{1 + y · cos D 1 Z} = -x · cos H 0 · cos D 1 + y · cos H 0 · sin D 1 + z · sin H 0.

Therefore, for example, the front 10 of the liquid crystal prism
The locus (Y ′, Z ′) of the ray on the YZ plane of (m) is Y ′ = − 10000 · Y / X Z ′ = − 10000 · Z / X. 2. The dependence of the laser twist angle on the incident deflection angle is shown below.

When a laser is used as the incident light and the physical properties of the material and the incident angle are given, the trajectory of the light beam on the YZ plane in front of the liquid crystal prism 10 (m) is changed by changing the refractive index of the liquid crystal and the incident deflection angle. obtain. The method of taking coordinate axes is as described above.
In FIGS. 11 to 14, the wedge apex angle is 10 (°) and the incident angles are 30 (°), 50 (°), 60 (°), and 70 (°), respectively.
The results are shown below. Similarly, in FIGS. 15 to 18, the apex angle is 30 (°) and the incident angles are 0 (°) and 1 respectively.
The results when 0 (°), 30 (°), and 50 (°) are shown. In the figure, the refractive index and the deflection angle are shown as parameters.

Here, the refractive index of the first and second transparent substrates 1 and 2 was changed to 1.520 on the assumption of glass plates, and the refractive index of the liquid crystal 3 was changed to 1.1 to 2.0. Further, there is an equiangular line every 5 or 10 (°) from the center point O on the screen 10 (m) ahead. Therefore, the light ray entering the O point direction perpendicular to the paper surface shows a locus drawn on the screen 10 (m) forward (the center point O is on the screen when the liquid crystal has a refractive index of 1.0). It is a locus.)

11 and 15 show the characteristics of the general locus. That is, when the incident angle is 0 (°) in FIG.
Even if the deflection angle is changed, the coordinate system only rotates, the locus is drawn radially around the point O, and the locus of the refractive index is a circle. Further, FIG. 12 shows a case where the light beam is incident while being inclined. Deflection angle 0 (°)
Then, the top side of the liquid crystal prism is placed in the Y-axis direction in the coordinate system viewed from the incident light direction. Here, when the deflection angle is increased, the liquid crystal prism is rotated counterclockwise by the deflection angle in the coordinate system viewed from the incident light direction, and the installed positional relationship is achieved. As the deflection angle increases from 0 (°) to 132 (°), the locus with a refractive index of 2.0 monotonically increases with the angle from the center point O. Further, when it exceeds 132 (°), it decreases monotonically and the refractive index giving the maximum deflection angle is 2.
It is decreasing from 0. In this decreasing deflection angle range, light rays are totally reflected at the interface (fourth interface) between the second transparent substrate 2 which is the exit surface from the liquid crystal prism and the air. 13,
14 shows that the deflection angle causing total reflection decreases as the incident angle increases, and FIGS. 15 to 18 show that the deflection angle causing total reflection decreases as the apex angle increases.

Therefore, it is understood that the optical deflector of the present invention can obtain a larger deflection angle than that when the incident light is simply incident perpendicularly on the incident surface.

[0033]

As described above in detail, since the optical deflector of the present invention has the structure described in the claims,
It is possible to obtain a deflection angle that is wider than in the past. Therefore, by using this optical deflector, it is possible to increase the utility value for various displays such as a display unit of a computer, a laser printer, a laser radar and the like.

[Brief description of drawings]

FIG. 1 is a perspective view of a wedge-shaped liquid crystal prism, which is related to a part of an optical deflector according to an embodiment.

FIG. 2 is an explanatory diagram showing a positional relationship of a part of the optical deflector of the embodiment.

FIG. 3 is an explanatory diagram showing the positional relationship of a part of the optical deflector of the embodiment.

FIG. 4 is an explanatory diagram showing the positional relationship of a part of the optical deflector of the embodiment.

FIG. 5 is an explanatory diagram showing the positional relationship of a part of the optical deflector of the embodiment.

FIG. 6 is an explanatory diagram showing a positional relationship of a part of the optical deflector of the embodiment.

FIG. 7 is an explanatory diagram relating to a part of the optical deflector of the embodiment and for converting the coordinate system.

FIG. 8 is an explanatory diagram relating to a part of the optical deflector of the embodiment and for converting the coordinate system.

FIG. 9 is an explanatory diagram relating to a part of the optical deflector of the embodiment and for converting the coordinate system.

FIG. 10 is an explanatory diagram showing the positional relationship of a part of the optical deflector of the embodiment.

FIG. 11 is a projection view showing a trajectory of light rays in front of the liquid crystal prism when a liquid crystal prism having an apex angle of 10 ° is adopted and incident light is made incident at an incident angle of 30 ° according to the optical deflector of the embodiment. is there.

FIG. 12 is a projection view showing a trajectory of light rays in front of the liquid crystal prism when a liquid crystal prism having an apex angle of 10 ° is adopted and incident light is incident at an incident angle of 50 ° according to the optical deflector of the embodiment. is there.

FIG. 13 is a projection view showing a trajectory of light rays in front of the liquid crystal prism when a liquid crystal prism having an apex angle of 10 ° is adopted and incident light is made incident at an incident angle of 60 ° according to the optical deflector of the embodiment. is there.

FIG. 14 is a projection view showing a trajectory of a light beam in front of the liquid crystal prism when a liquid crystal prism having an apex angle of 10 ° is adopted and incident light is incident at an incident angle of 70 ° according to the optical deflector of the embodiment. is there.

FIG. 15 is a projection view showing a trajectory of a light beam in front of the liquid crystal prism when a liquid crystal prism having an apex angle of 30 ° is adopted and incident light is incident at an incident angle of 0 ° according to the optical deflector of the embodiment. is there.

FIG. 16 is a projection view showing a trajectory of light rays in front of a liquid crystal prism when a liquid crystal prism having an apex angle of 30 ° is adopted and incident light is incident at an incident angle of 10 ° according to the optical deflector of the embodiment. is there.

FIG. 17 is a projection view showing a trajectory of light rays in front of the liquid crystal prism when a liquid crystal prism having an apex angle of 30 ° is adopted and incident light is incident at an incident angle of 30 ° according to the optical deflector of the embodiment. is there.

FIG. 18 is a projection view showing a trajectory of light rays in front of a liquid crystal prism when a liquid crystal prism having an apex angle of 30 ° is adopted and incident light is made incident at an incident angle of 50 ° according to the optical deflector of the embodiment. is there.

FIG. 19 is a cross-sectional view of a wedge-shaped liquid crystal prism relating to a part of a conventional optical deflector.

[Explanation of symbols]

1 ... 1st transparent substrate 2 ... 2nd transparent substrate 3 ...
Liquid crystal PO ... Direction in which incident light is incident on the incident surface of the first transparent substrate α ... Apex angle H ₀ ... Incident angle

Claims (1)

[Claims] 1. Light having a wedge-type or Fresnel-type liquid crystal prism in which incident light transmitted through a polarizing plate is incident on an incident surface from one direction, and emitted light is emitted from the emission surface in a direction deflected with respect to the one direction. An optical deflector, wherein the normal line of the incident surface does not coincide with the one direction.