Patent Application
20240272487
An embodiment of the present invention relates to an optical element that controls a distribution of light emitted from a light source.
An optical element which is a so-called liquid crystal lens has been conventionally known in which a change in the refractive index of a liquid crystal is utilized by adjusting a voltage applied to the liquid crystal (for example, see Japanese laid-open patent publication No. 2005-317879, 2010-230887, or 2014-160277). For example, the lighting devices disclosed in the Japanese laid-open patent publications Nos. 2005-317879 and 2010-230877 use a liquid crystal lens to distribute light from a light source in a circular shape. Further, the beam shaping device disclosed in the Japanese laid-open patent publication No. 2014-160277 changes the distribution shape of light by changing patterns of an electrode applied to a liquid crystal.
An optical element according to an embodiment of the present invention includes a plurality of stacked liquid crystal cells. The plurality of liquid crystal cells each includes a first substrate on which a first transparent electrode, a second transparent electrode, and a first alignment film covering the first transparent electrode and the second transparent electrode are provided, a second substrate on which a third transparent electrode, a fourth transparent electrode, and a second alignment film covering the third transparent electrode and the second transparent electrode are provided, and a liquid crystal layer between the first substrate and the second substrate. The plurality of liquid crystal cells includes a first liquid crystal cell. The first liquid crystal cell includes the first transparent electrode and the second transparent electrode extending in a first direction, the third transparent electrode and the fourth transparent electrode extending in a second direction orthogonal to the first direction, the first alignment film aligning liquid crystal molecules in the liquid crystal layer in the second direction when no voltages are applied to the first transparent electrode and the second transparent electrode, and the second alignment film aligning liquid crystal molecules in the liquid crystal layer in the second direction when no voltages are applied to the third transparent electrode and the fourth transparent electrode.
An optical element includes a plurality of stacked liquid crystal cells. The plurality of liquid crystal cells each includes a first substrate on which a first transparent electrode, a second transparent electrode, and a first alignment film covering the first transparent electrode and the second transparent electrode are provided, a second substrate on which a third transparent electrode, a fourth transparent electrode, and a second alignment film covering the third transparent electrode and the second transparent electrode are provided, and a liquid crystal layer between the first substrate and the second substrate. The plurality of liquid crystal cells includes a first liquid crystal cell. The first liquid crystal cell includes the first transparent electrode and the second transparent electrode extending in a first direction, the third transparent electrode and the fourth transparent electrode extending in the first direction, the first alignment film aligning liquid crystal molecules in the liquid crystal layer in a second direction orthogonal to the first direction when no voltages are applied to the first transparent electrode and the second transparent electrode, and the second alignment film aligning liquid crystal molecules in the liquid crystal layer in the second direction when no voltages are applied to the third transparent electrode and the fourth transparent electrode.
An optical element includes a plurality of stacked liquid crystal cells. The plurality of liquid crystal cells each includes a first substrate on which a first transparent electrode, a second transparent electrode, and a first alignment film covering the first transparent electrode and the second transparent electrode are provided, a second substrate on which a third transparent electrode, a fourth transparent electrode, and a second alignment film covering the third transparent electrode and the second transparent electrode are provided, and a liquid crystal layer between the first substrate and the second substrate. The plurality of liquid crystal cells includes a first liquid crystal cell. The first liquid crystal cell includes the first transparent electrode and the second transparent electrode extending in a first direction, the third transparent electrode and the fourth transparent electrode extending in the first direction, the first alignment film aligning liquid crystal molecules in the liquid crystal layer in a second direction orthogonal to the first direction when no voltages are applied to the first transparent electrode and the second transparent electrode, and the second alignment film aligning liquid crystal molecules in the liquid crystal layer in the first direction when no voltages are applied to the third transparent electrode and the fourth transparent electrode.
For example, an optical element in which liquid crystal cells having a lens function are stacked can change the shape of light incident from a light source using the lens function and emit the light. However, when the shape of the light is changed, the emitted light may cause color unevenness. In particular, in an optical element that greatly changes the shape of light from a light source, when light transmitting through the optical element is irradiated on a wall or the like, color unevenness near the outline of the emitted light may become noticeable.
In view of the above problem, an embodiment of the present invention can provide an optical element in which color unevenness in a light distribution is suppressed.
Hereinafter, each of the embodiments of the present invention is described with reference to the drawings. However, the present invention can be implemented in various modes without departing from the gist of the invention and should not be interpreted as being limited to the description of the embodiments exemplified below.
Although the drawings may be schematically represented in terms of width, thickness, shape, and the like of each part as compared with their actual mode in order to make explanation clearer, they are only an example and an interpretation of the present invention is not limited. In addition, in the drawings, the same reference numerals are provided to the same elements as those described previously with reference to preceding figures and repeated explanations may be omitted accordingly.
In the case when a single film is processed to form a plurality of structural bodies, each structural body may have different functions and roles, and the bases formed beneath each structural body may also be different. However, the plurality of structural bodies is derived from films formed in the same layer by the same process and have the same material. Therefore, the plurality of these films is defined as existing in the same layer.
When expressing a mode in which another structure is arranged over a certain structure, in the case where it is simply described as “over”, unless otherwise noted, a case where another structure is arranged directly over a certain structure as if in contact with that structure, and a case where another structure is arranged via another structure over a certain structure, are both included.
An optical element 10 according to an embodiment of the present invention is described with reference to
Light from the light source transmits through the optical element 10. At this time, when no voltages are applied to electrodes of each liquid crystal cell 100 (details of the electrodes are described later.), the light from the light source transmits through the optical element 10 without changing its shape. For example, when the light from the light source has a circular shape, the transmitted light of the optical element 10 maintains a circular shape (see
Two adjacent liquid crystal cells 100 of the plurality of liquid crystal cells 100 are bonded to each other via an optical elastic resin layer 160. For example, a translucent adhesive containing an acrylic resin or an epoxy resin can be used for the optical elastic resin layer 160.
Although four liquid crystal cells 100 are shown in
As shown in
For example, a rigid substrate having light-transmitting properties such as a glass substrate, a quartz substrate, or a sapphire substrate is used as each of the first substrate 110-1 and the second substrate 110-2. Further, a flexible substrate having light-transmitting properties such as a polyimide resin substrate, an acrylic resin substrate, a siloxane resin substrate, or a fluorine resin substrate can also be used as each of the first substrate 110-1 and the second substrate 110-2.
Each of the first transparent electrode 120-1, the second transparent electrode 120-2, the third transparent electrode 120-3, and the fourth transparent electrode 120-4 functions as an electrode for forming an electric field in the liquid crystal layer 150. For example, a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) is used for each of the first transparent electrode 120-1, the second transparent electrode 120-2, the third transparent electrode 120-3, and the fourth transparent electrode 120-4.
The liquid crystal layer 150 can refract transmitted light or change the polarization state of transmitted light according to the alignment state of the liquid crystal molecules. For example, nematic liquid crystal can be used as the liquid crystal of the liquid crystal layer 150. Although a positive liquid crystal is described as the liquid crystal in the present embodiment, a negative liquid crystal can also be adopted by changing the initial alignment directions of the liquid crystal molecules. Further, the liquid crystal preferably contains a chiral agent that imparts twist to the liquid crystal molecules.
Each of the first alignment film 130-1 and the second alignment film 130-2 aligns the liquid crystal molecules in the liquid crystal layer 150 in a predetermined direction. For example, a polyimide resin or the like can be used for each of the first alignment film 130-1 and the second alignment film 130-2. In addition, each of the first alignment film 130-1 and the second alignment film 130-2 may be imparted with alignment properties by an alignment treatment such as a rubbing method or a photo-alignment method. The rubbing method is a method of rubbing the surface of the alignment film in one direction. The photo-alignment method is a method of irradiating an alignment film with linearly polarized ultraviolet rays.
An adhesive material containing epoxy resin, acrylic resin, or the like can be used for the sealing member 140. The adhesive material may be of an ultraviolet curable type or a heat curable type.
As described above, the first liquid crystal cell 100-1, the second liquid crystal cell 100-2, the third liquid crystal cell 100-3, and the fourth liquid crystal cell 100-4 have the same basic structure. However, the arrangement of the transparent electrodes 120 and the alignment properties of the alignment films 130 are different from each other between the first liquid crystal cell 100-1, the second liquid crystal cell 100-2, the third liquid crystal cell 100-3, and the fourth liquid crystal cell 100-4.
In the first liquid crystal cell 100-1 and the second liquid crystal cell 100-2, the first transparent electrode 120-1 and the second transparent electrode 120-2 extend in the x-axis direction, and the third transparent electrode 120-3 and the fourth transparent electrode 120-4 extend in the y-axis direction. That is, in the first liquid crystal cell 100-1 and the second liquid crystal cell 100-2, the extending direction of each of the first transparent electrode 120-1 and the second transparent electrode 120-2 is the x-axis direction, and the extending direction of each of the third transparent electrode 120-3 and the fourth transparent electrode 120-4 is the y-axis direction. The first transparent electrode 120-1 and the second transparent electrode 120-2 have a comb-teeth shape, and the first transparent electrode 120-1 and the second transparent electrode 120-2 are arranged alternately in the y-axis direction. Further, the third transparent electrode 120-3 and the fourth transparent electrode 120-4 have a comb-teeth shape, and the third transparent electrode 120-3 and the fourth transparent electrode 120-4 are arranged alternately in the x-axis direction.
In the third liquid crystal cell 100-3 and the fourth liquid crystal cell 100-4, the first transparent electrode 120-1 and the second transparent electrode 120-2 extend in the y-axis direction, and the third transparent electrode 120-3 and the fourth transparent electrode 120-4 extend in the x-axis direction. That is, in the third liquid crystal cell 100-3 and the fourth liquid crystal cell 100-4, the extending direction of each of the first transparent electrode 120-1 and the second transparent electrode 120-2 is the y-axis direction, and the extending direction of each of the third transparent electrode 120-3 and the fourth transparent electrode 120-4 is the x-axis direction. The first transparent electrode 120-1 and the second transparent electrode 120-2 have a comb-teeth shape, and the first transparent electrode 120-1 and the second transparent electrode 120-2 are arranged alternately in the x-axis direction. Further, the third transparent electrode 120-3 and the fourth transparent electrode 120-4 have a comb-teeth shape, and the third transparent electrode 120-3 and the fourth transparent electrode 120-4 are arranged alternately in the y-axis direction.
In addition, although the extending direction of the first transparent electrode 120-1 and the second transparent electrode 120-2 is orthogonal to the extending direction of the third transparent electrode 120-3 and the fourth transparent electrode 120-4, the extending directions may intersect with a slight deviation (within approximately +10 degrees) from orthogonality.
Further, the optical element 10 can control a distribution of unpolarized light by including at least two liquid crystal cells 100. Therefore, the optical element 10 does not require providing a pair of polarizing plates that, for example, are provided on the front and back surfaces of the liquid crystal display element.
Here, properties of light transmitting through the liquid crystal cell 100 are described with reference to
The liquid crystal molecules closer to the first substrate 110-1 are aligned in a convex arc shape in the x-axis direction with respect to the first substrate 110-1 by the influence of the lateral electric field between the first transparent electrode 120-1 and the second transparent electrode 120-2. Further, the liquid crystal molecules closer to the second substrate 110-2 are aligned in a convex arc shape in the y-axis direction with respect to the second substrate 110-2 by the influence of the lateral electric field between the third transparent electrode 120-3 and the fourth transparent electrode 120-4. At this time, the alignment direction of the liquid crystal molecules in the center between the first substrate 110-1 and the second substrate 110-2 (the liquid crystal molecules located near the top of the liquid crystal molecules in the above-mentioned convex arc shape) are hardly changed due to any lateral electric field. In addition, since the first substrate 110-1 and the second substrate 110-2 are far apart with a sufficient inter-substrate distance, the lateral electric field between the first transparent electrode 120-1 and the second transparent electrode 120-2 of the first substrate 110-1 does not affect the alignment of the liquid crystal molecules on the side of the second substrate 110-2, or is negligibly small. Similarly, the lateral electric field between the third transparent electrode 120-3 and the fourth transparent electrode 120-4 of the second substrate 110-2 does not affect the alignment of the liquid crystal molecules on the side of the first substrate 110-1, or is negligibly small. Therefore, the liquid crystal molecules in the twisted state before the generation of the lateral electric field maintain the twisted state even after the generation of the lateral electric field as shown in
Further, the case in which the light transmits through the liquid crystal cell 100 shown in
In
In contrast, since the S-polarization component of the second polarized light 1000-2 incident on the liquid crystal cell 100 is different from the alignment direction of the liquid crystal molecules on the side of the first substrate 110-1, the second polarized light 1000-2 is not diffused (See (2) in
Next, a configuration of an alignment of the liquid crystal molecules different from the above-mentioned alignment is described.
Further, the case in which the light transmits through the liquid crystal cell 100 shown in
In contrast, since the S-polarization component of the second polarized light 1000-2 incident on the liquid crystal cell 100 is different from the alignment direction of the liquid crystal molecules on the side of the first substrate 110-1, the second polarized light 1000-2 is not diffused (See (2) in
As can be seen from the above, in the liquid crystal cell 100, the alignment of the liquid crystal molecules in the liquid crystal layer 150 can be controlled by the extending direction of the transparent electrode 120, the rubbing direction of the alignment film 130, and the voltages applied to the transparent electrodes 120. Therefore, the optical element 10 can diffuse light in a predetermined direction by using the optical rotation and refractive index distribution of liquid crystal molecules of each of the plurality of liquid crystal cells 100.
Next, the extending directions of the transparent electrodes 120 and the alignment directions of the liquid crystal molecules in the liquid crystal layer 150 in the optical element 10 are described.
In order to obtain a light distribution having a cross shape by the optical element 10, in each of the first liquid crystal cell 100-1, the second liquid crystal cell 100-2, the third liquid crystal cell 100-3, and the fourth liquid crystal cell 100-4, high voltages are applied to the first transparent electrode 120-1 and the third transparent electrode 120-3, and low voltages are applied to the second transparent electrode 120-2 and the fourth transparent electrode 120-4.
In the first liquid crystal cell 100-1, when voltages are applied to the transparent electrodes 120 as described above, the liquid crystal molecules closer to the first substrate 110-1 are aligned in a convex arc shape in the y-axis direction, and the liquid crystal molecules closer to the second substrate 110-2 rotate from the y-axis direction to the x-axis direction to be aligned in a convex arc shape in the x-axis direction. Since the liquid crystal molecules in the first liquid crystal cell 100-1 are not in a twisted state, the liquid crystal layer 150 does not have optical rotation. In the second liquid crystal cell 100-2, the liquid crystal molecules closer to the first substrate 110-1 rotate from the x-axis direction to the y-axis direction to be aligned in a convex arc shape in the y-axis direction, and the liquid crystal molecules closer to the second substrate 110-2 are aligned in a convex arc shape in the x-axis direction. Since the liquid crystal molecules in the second liquid crystal cell 100-2 are not in a twisted state, the liquid crystal layer 150 does not have optical rotation. In the third liquid crystal cell 100-3, the liquid crystal molecules closer to the first substrate 110-1 rotate from the y-axis direction to the x-axis direction to be aligned in a convex arc shape in the x-axis direction, and the liquid crystal molecules closer to the second substrate 110-2 are aligned in a convex arc shape in the y-axis direction. Since the liquid crystal molecules in the third liquid crystal cell 100-3 are not in a twisted state, the liquid crystal layer 150 does not have optical rotation. In the fourth liquid crystal cell 100-4, the liquid crystal molecules closer to the first substrate 110-1 are aligned in a convex arc shape in the x-axis direction, and the liquid crystal molecules closer to the second substrate 110-2 rotate from the x-axis direction to the y-axis direction to be aligned in a convex arc shape in the y-axis direction. Since the liquid crystal molecules in the fourth liquid crystal cell 100-4 are not in a twisted state, the liquid crystal layer 150 does not have optical rotation. Therefore, when light transmits through the optical element 10, the P-polarization component and the S-polarization component of the light at the time of incidence on the optical element 10 are controlled as shown in Table 2.
As can be seen from Table 2, in the optical element 10, the P-polarization component of the incident light is diffused four times in the x-axis direction, and the S-polarized light component is diffused four times in the y-axis direction. Further, in the optical element 10, both the P-polarization component and the S-polarization component are diffused not only on the side of the first substrate 110-1 but also on the side of the second substrate 110-2.
As described above, in the optical element 10 according to an embodiment of the present invention, a light distribution having a cross shape can be obtained by increasing the number of times of diffusion compared to the conventional optical element. Therefore, color unevenness in the light distribution having a cross shape can be suppressed. Further, since the number of times of diffusion can be increased without increasing the number of liquid crystal cells 100 in the optical element 10, a decrease in transmittance and an increase in manufacturing cost can be suppressed.
An optical element 20 according to an embodiment of the present invention is described with reference to
As can be seen from Table 3, the third liquid crystal cell 200-3 and the fourth liquid crystal cell 200-4 have the same structure as the first liquid crystal cell 200-1 and the second liquid crystal cell 200-2, respectively. In other words, the optical element 20 has a structure in which the first liquid crystal cells 200-1 and the second liquid crystal cell 200-2 are alternately stacked.
In order to obtain a light distribution having a cross shape by the optical element 20, in each of the first liquid crystal cell 200-1, the second liquid crystal cell 200-2, the third liquid crystal cell 200-3, and the fourth liquid crystal cell 200-4, high voltages are applied to the first transparent electrode 220-1 and the third transparent electrode 220-3, and low voltages are applied to the second transparent electrode 220-2 and the fourth transparent electrode 220-4.
In the first liquid crystal cell 200-1, when voltages are applied to the transparent electrodes 220 as described above, the liquid crystal molecules closer to each of the first substrate 210-1 and the second substrate 210-2 are aligned in a convex arc shape in the y-axis direction. Since the liquid crystal molecules in the first liquid crystal cell 200-1 are not in a twisted state, the liquid crystal layer does not have optical rotation. In the second liquid crystal cell 200-2, the liquid crystal molecules closer to each of the first substrate 210-1 and the second substrate 210-2 are aligned in a convex arc shape in the x-axis direction.
Since the liquid crystal molecules in the second liquid crystal cell 200-2 are not in a twisted state, the liquid crystal layer does not have optical rotation. The third liquid crystal cell 200-3 and the fourth liquid crystal cell 200-4 have the same configuration as the first liquid crystal cell 200-1 and the second liquid crystal cell 200-2, respectively. Therefore, when light transmits through the optical element 20, the P-polarization component and the S-polarization component of the light at the time of incidence on the optical element 20 are controlled as shown in Table 4.
As can be seen from Table 4, in the optical element 20, the P-polarization component of the incident light is diffused four times in the x-axis direction, and the S-polarized light component is diffused four times in the y-axis direction. Further, in the optical element 20, both the P-polarization component and the S-polarization component are diffused not only on the side of the first substrate 210-1 but also on the side of the second substrate 210-2.
As described above, in the optical element 20 according to an embodiment of the present invention, a light distribution having a cross shape can be obtained by increasing the number of times of diffusion compared to the conventional optical element. Therefore, color unevenness in the light distribution having a cross shape can be suppressed. Further, since the number of times of diffusion can be increased without increasing the number of liquid crystal cells 200 in the optical element 20, a decrease in transmittance and an increase in manufacturing cost can be suppressed.
An optical element 30 according to an embodiment of the present invention is described with reference to
As can be seen from Table 5, the third liquid crystal cell 300-3 and the fourth liquid crystal cell 300-4 have the same structure as the first liquid crystal cell 300-1 and the second liquid crystal cell 300-2, respectively. In other words, the optical element 30 has a structure in which the first liquid crystal cells 300-1 and the second liquid crystal cell 300-2 are alternately stacked.
In order to obtain a light distribution having a cross shape by the optical element 30, in each of the first liquid crystal cell 300-1, the second liquid crystal cell 300-2, the third liquid crystal cell 300-3, and the fourth liquid crystal cell 300-4, high voltages are applied to the first transparent electrode 320-1 and the third transparent electrode 320-3, and low voltages are applied to the second transparent electrode 320-2 and the fourth transparent electrode 320-4.
In the first liquid crystal cell 300-1, when voltages are applied to the transparent electrodes 320 as described above, the liquid crystal molecules closer to the first substrate 310-1 rotate from the x-axis direction to the y-axis direction to be aligned in a convex arc shape in the y-axis direction, and the liquid crystal molecules closer to the second substrate 310-2 are aligned in a convex arc shape in the y-axis direction. Since the liquid crystal molecules in the first liquid crystal cell 300-1 are not in a twisted state, the liquid crystal layer does not have optical rotation. In the second liquid crystal cell 300-2, the liquid crystal molecules closer to the first substrate 310-1 are aligned in a convex arc shape in the x-axis direction, and the liquid crystal molecules closer to the second substrate 310-2 rotate from the y-axis direction to the x-axis direction to be aligned in a convex arc shape in the x-axis direction. Since the liquid crystal molecules in the second liquid crystal cell 300-2 are not in a twisted state, the liquid crystal layer does not have optical rotation. The third liquid crystal cell 300-3 and the fourth liquid crystal cell 300-4 have the same configuration as the first liquid crystal cell 300-1 and the second liquid crystal cell 300-2, respectively. Therefore, when light transmits through the optical element 30, the P-polarization component and the S-polarization component of the light at the time of incidence on the optical element 30 are controlled as shown in Table 6.
As can be seen from Table 6, in the optical element 30, the P-polarization component of the incident light is diffused four times in the x-axis direction, and the S-polarized light component is diffused four times in the y-axis direction. Further, in the optical element 30, both the P-polarization component and the S-polarization component are diffused not only on the side of the first substrate 310-1 but also on the side of the second substrate 310-2.
As described above, in the optical element 30 according to an embodiment of the present invention, a light distribution having a cross shape can be obtained by increasing the number of times of diffusion compared to the conventional optical element. Therefore, color unevenness in the light distribution having a cross shape can be suppressed. Further, since the number of times of diffusion can be increased without increasing the number of liquid crystal cells 300 in the optical element 30, a decrease in transmittance and an increase in manufacturing cost can be suppressed.
A shape of the light distribution obtained by the optical element 30 is not limited to the cross shape. When voltages applied to the transparent electrodes 320 are controlled, various shapes of the light distribution can be obtained. For example, in each of the first liquid crystal cell 300-1 and the second liquid crystal cell 300-2, high voltages are applied to the first transparent electrode 320-1 and the third transparent electrode 320-3, and low voltages are applied to the second transparent electrode 320-2 and the fourth transparent electrode 320-4. Further, in the third liquid crystal cell 300-3, no voltages are applied to the first transparent electrode 320-1 and the second transparent electrode 320-2, and a high voltage and a low voltage are applied to the third transparent electrode 320-3 and the fourth transparent electrode 320-4, respectively. Furthermore, in the fourth liquid crystal cell 300-4, a high voltage and a low voltage are applied to the first transparent electrode 320-1 and the second transparent electrode 320-2, respectively, and no voltages are applied to the third transparent electrode 320-3 and the fourth transparent electrode 320-4.
In the first liquid crystal cell 300-1, when voltages are applied to the transparent electrodes 320 as described above, the liquid crystal molecules closer to the first substrate 310-1 rotate from the x-direction to the y-axis direction so as to be aligned in a convex arc shape in the y-axis direction, and the liquid crystal molecules closer to the second substrate 310-2 are aligned in a convex arc shape in the y-axis direction. Since the liquid crystal molecules in the first liquid crystal cell 300-1 are not in a twisted state, the liquid crystal layer does not have optical rotation. In the second liquid crystal cell 300-2, the liquid crystal molecules closer to the first substrate 310-1 are aligned in a convex arc shape in the x-axis direction, and the liquid crystal molecules closer to the second substrate 310-2 rotate from the y-axis direction to the x-axis direction so as to be aligned in a convex arc shape in the x-axis direction. Since the liquid crystal molecules in the second liquid crystal cell 300-2 are not in a twisted state, the liquid crystal layer does not have optical rotation. In the third liquid crystal cell 300-3, the liquid crystal molecules closer to the first substrate 310-1 are aligned in the x-direction, and the liquid crystal molecules closer to the second substrate 310-2 are aligned in a convex arc shape in the y-direction. Since the liquid crystal molecules in the third liquid crystal cell 300-3 are in a twisted state, the liquid crystal layer has optical rotation. In the fourth liquid crystal cell 300-4, the liquid crystal molecules closer to the first substrate 310-1 are aligned in a convex arc in the y-axis direction, and the liquid crystal molecules closer to the second substrate 310-2 are aligned in the x-axis direction. Since the liquid crystal molecules in the fourth liquid crystal cell 300-4 are in a twisted state, the liquid crystal layer has optical rotation. Therefore, when light transmits through the optical element 30, the P-polarization component and the S-polarization component of the light at the time of incidence on the optical element 30 are controlled as shown in Table 7.
As can be seen from Table 7, when voltages applied to the transparent electrodes 320 are controlled in the optical element 30, the P-polarization component of the incident light is diffused three times and the S-polarization component of the incident light is diffused three times. Specifically, the P-polarization is diffused twice and once in the x-axis direction and the y-axis direction, respectively. The S-polarization component is diffused once and twice in the x-axis direction and the y-axis direction, respectively. Both the P-polarization component and the S-polarization component are diffused not only in the x-axis direction but also in the y-axis direction, and the number of times of the diffusion each in the x-axis direction and the y-axis direction is the same, so that a light distribution having a circular shape is obtained.
A shape of the light distribution obtained by the optical element 30 is not limited to the circular shape. For example, in the first liquid crystal cell 300-1 and the third liquid crystal cell 300-3, no voltages are applied to the first transparent electrode 320-1 and the second transparent electrode 320-2, and a high voltage and a low voltage are applied to the third transparent electrode 320-3 and the fourth transparent electrode 320-4, respectively. In the second liquid crystal cell 300-2 and the fourth liquid crystal cell 300-4, high voltages are applied to the first transparent electrode 320-1 and the third transparent electrode 320-3, and low voltages are applied to the second transparent electrode 320-2 and the fourth transparent electrodes 320-4.
In the first liquid crystal cell 300-1, when voltages are applied to the transparent electrodes 320 as described above, the liquid crystal molecules closer to the first substrate 310-1 are aligned in the x-axis direction, and the liquid crystal molecules closer to the second substrate 310-2 are aligned in a convex arc shape in the y-axis direction. Since the liquid crystal molecules in the first liquid crystal cell 300-1 are in a twisted state, the liquid crystal layer has optical rotation. The third liquid crystal cell 300-3 and the fourth liquid crystal cell 300-4 have the same configuration as the first liquid crystal cell 300-1 and the second liquid crystal cell 300-2, respectively. Therefore, when light transmits through the optical element 30, the P-polarization component and the S-polarization component of the light at the time of incidence on the optical element 30 are controlled as shown in Table 8.
As can be seen from Table 8, when voltages applied to the transparent electrodes 320 are controlled in the optical element 30, the P-polarization component of the incident light is diffused three times and the S-polarization component of the incident light is diffused three times. Specifically, the P-polarization is diffused twice and once in the x-axis direction and the y-axis direction, respectively. The S-polarization component is diffused twice and once in the x-axis direction and the y-axis direction, respectively. Both the P-polarization component and the S-polarization component are diffused not only in the x-axis direction but also in the y-axis direction, and the number of times of the diffusion in the x-axis direction is more than the number of times of the diffusion in the y-axis direction, so that a light distribution having an elliptical shape is obtained.
As described above in Modification 1 and Modification 2, not only the light distribution having a cross shape but also the light distribution having a circular shape or an elliptical shape can be obtained in the optical element 30 according to an embodiment of the present invention.
An optical element 40 according to an embodiment of the present invention is described with reference to
In order to obtain a light distribution having a cross shape by the optical element 40, in each of the first liquid crystal cell 400-1, the second liquid crystal cell 400-2, the third liquid crystal cell 400-3, and the fourth liquid crystal cell 400-4, high voltages are applied to the first transparent electrode 420-1 and the third transparent electrode 420-3, and low voltages are applied to the second transparent electrode 420-2 and the fourth transparent electrode 420-4.
In the first liquid crystal cell 400-1, when voltages are applied to the transparent electrodes 420 as described above, the liquid crystal molecules closer to the first substrate 410-1 are aligned in a convex arc shape in the y-axis direction, and the liquid crystal molecules closer to the second substrate 410-2 are aligned in the y-axis direction. Since the liquid crystal molecules in the first liquid crystal cell 400-1 are not in a twisted state, the liquid crystal layer does not have optical rotation. In the second liquid crystal cell 400-2, the liquid crystal molecules closer to the first substrate 410-1 are aligned in a convex arc shape in the x-axis direction, and the liquid crystal molecules closer to the second substrate 410-2 are aligned in a convex arc shape in the x-axis direction. Since the liquid crystal molecules in the second liquid crystal cell 400-2 are not in a twisted state, the liquid crystal layer does not have optical rotation. In the third liquid crystal cell 400-3, the liquid crystal molecules closer to the first substrate 410-1 rotate from the x-axis direction to the y-axis direction to be aligned in a convex arc shape in the y-axis direction, and the liquid crystal molecules closer to the second substrate 410-2 are aligned in a convex arc shape in the y-axis direction. Since the liquid crystal molecules in the third liquid crystal cell 400-3 are not in a twisted state, the liquid crystal layer does not have optical rotation. In the fourth liquid crystal cell 400-4, the liquid crystal molecules closer to the first substrate 410-1 are aligned in a convex arc shape in the x-axis direction, and the liquid crystal molecules closer to the second substrate 410-2 rotate from the y-axis direction to the x-axis direction to be aligned in a convex arc shape in the x-axis direction. Since the liquid crystal molecules in the fourth liquid crystal cell 400-4 are not in a twisted state, the liquid crystal layer does not have optical rotation. Therefore, when light transmits through the optical element 40, the P-polarization component and the S-polarization component of the light at the time of incidence on the optical element 40 are controlled as shown in Table 10.
As can be seen from Table 10, in the optical element 40, the P-polarization component of the incident light is diffused four times in the x-axis direction, and the S-polarized light component is diffused four times in the y-axis direction. Further, in the optical element 40, both the P-polarization component and the S-polarization component are diffused not only on the side of the first substrate 410-1 but also on the side of the second substrate 410-2.
As described above, in the optical element 40 according to an embodiment of the present invention, a light distribution having a cross shape can be obtained by increasing the number of times of diffusion compared to the conventional optical element. Therefore, color unevenness in the light distribution having a cross shape can be suppressed. Further, since the number of times of diffusion can be increased without increasing the number of liquid crystal cells 400 in the optical element 40, a decrease in transmittance and an increase in manufacturing cost can be suppressed.
A shape of the light distribution obtained by the optical element 40 is not limited to the cross shape. When voltages applied to the transparent electrodes 420 are controlled, various shapes of the light distribution can be obtained. For example, in each of the first liquid crystal cell 400-1 and the second liquid crystal cell 400-2, high voltages are applied to the first transparent electrode 420-1 and the third transparent electrode 420-3, and low voltages are applied to the second transparent electrode 420-2 and the fourth transparent electrode 420-4. Further, in the third liquid crystal cell 400-3, no voltages are applied to the first transparent electrode 420-1 and the second transparent electrode 420-2, and a high voltage and a low voltage are applied to the third transparent electrode 420-3 and the fourth transparent electrode 420-4, respectively. Furthermore, in the fourth liquid crystal cell 400-4, a high voltage and a low voltage are applied to the first transparent electrode 420-1 and the second transparent electrode 420-2, respectively, and no voltages are applied to the third transparent electrode 420-3 and the fourth transparent electrode 420-4.
In the first liquid crystal cell 400-1, when voltages are applied to the transparent electrodes 420 as described above, the liquid crystal molecules closer to the first substrate 410-1 are aligned in a convex arc shape in the y-axis direction, and the liquid crystal molecules closer to the second substrate 410-2 are aligned in a convex arc shape in the y-axis direction. Since the liquid crystal molecules in the first liquid crystal cell 400-1 are not in a twisted state, the liquid crystal layer does not have optical rotation. In the second liquid crystal cell 400-2, the liquid crystal molecules closer to the first substrate 410-1 are aligned in a convex arc shape in the x-axis direction, and the liquid crystal molecules closer to the second substrate 410-2 are aligned in a convex arc shape in the x-axis direction. Since the liquid crystal molecules in the second liquid crystal cell 400-2 are not in a twisted state, the liquid crystal layer does not have optical rotation.
In the third liquid crystal cell 400-3, the liquid crystal molecules closer to the first substrate 410-1 are aligned in the x-direction, and the liquid crystal molecules closer to the second substrate 410-2 are aligned in a convex arc shape in the y-direction. Since the liquid crystal molecules in the third liquid crystal cell 400-3 are in a twisted state, the liquid crystal layer has optical rotation. In the fourth liquid crystal cell 400-4, the liquid crystal molecules closer to the first substrate 410-1 are aligned in a convex arc in the x-axis direction, and the liquid crystal molecules closer to the second substrate 410-2 are aligned in the y-axis direction. Since the liquid crystal molecules in the fourth liquid crystal cell 400-4 are in a twisted state, the liquid crystal layer has optical rotation. Therefore, when light transmits through the optical element 40, the P-polarization component and the S-polarization component of the light at the time of incidence on the optical element 30 are controlled as shown in Table 11.
As can be seen from Table 11, when voltages applied to the transparent electrodes 420 are controlled in the optical element 40, the P-polarization component of the incident light is diffused three times and the S-polarization component of the incident light is diffused three times. Specifically, the P-polarization is diffused twice and once in the x-axis direction and the y-axis direction, respectively. The S-polarization component is diffused once and twice in the x-axis direction and the y-axis direction, respectively. Both the P-polarization component and the S-polarization component are diffused not only in the x-axis direction but also in the y-axis direction, and the number of times of the diffusion each in the x-axis direction and the y-axis direction is the same, so that a light distribution having a circular shape is obtained.
As described above in the Modification section, not only the light distribution having a cross shape but also the light distribution having a circular shape can be obtained in the optical element 40 according to an embodiment of the present invention.
Within the scope of the present invention, those skilled in the art may conceive of examples of changes and modifications, and it is understood that these examples of changes and modifications are also included within the scope of the present invention. For example, additions, deletions, or design changes of constituent elements, or additions, omissions, or changes to conditions of steps as appropriate based on the respective embodiments described above are also included within the scope of the present invention as long as the gist of the present invention is provided.
Further, other effects which differ from those brought about by the embodiment, but which are apparent from the description herein or which can be readily predicted by those skilled in the art, are naturally understood to be brought about by the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-179072 | Nov 2021 | JP | national |
This application is a Continuation of International Patent Application No. PCT/JP2022/032203, filed on Aug. 26, 2022, which claims the benefit of priority to Japanese Patent Application No. 2021-179072, filed on Nov. 1, 2021, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/032203 | Aug 2022 | WO |
| Child | 18647842 | US |
