Lighting device, vehicle lighting system

Abstract

To improve the luminance of irradiation light of a lighting device or the like which uses a liquid crystal element.SOLUTION: A lighting device includes: a light source 10; a light focusing part for focusing light so that light emitted from the light source 10 is focused in a prescribed position; a liquid crystal element 15 arranged in a position including the focus point; a first deflection element; a second deflection element; and a projection lens 18 for expanding and projecting an image which is formed by the liquid crystal element 15, the first deflection element and the second deflection element. The liquid crystal element 15 has: a first face substantially orthogonal to a light axis of the projection lens 18, being a range including a position of the focus point; and at least one second face formed around the first face and arranged in a direction which is inclined to the light axis of the projection lens 18. The second face is arranged so that light is made incident to a liquid crystal layer of the liquid crystal element 15 from an azimuth within a range of ±90° or smaller in the best visible azimuth of the liquid crystal element 15 or in an azimuth angle direction with the best visible azimuth as a reference.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a lighting device and a vehicle lighting system.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2019-128449 (Patent Document 1) describes a variable light distribution headlamp as an example of a lighting device using a vertically aligned liquid crystal element. However, there is room for improvement from the viewpoint of improving the brightness of the irradiation light emitted from the lighting device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] One of the objects of the specific aspect according to the present disclosure is to improve the brightness of irradiation light in a lighting device using a liquid crystal element or the like.

Means for Solving the Problems

[0005] [1]One aspect of the lighting device according to the present invention includes: (a) a light source; (b) a condenser that condenses light emitted from the light source so that the light converges at a predetermined position; (c) a liquid crystal layer, and a liquid crystal element disposed corresponding to the position of the focus; (d) a first polarizing element disposed on the light incident surface side of the liquid crystal element; (e) a second polarizing element disposed on the light exit surface side of the liquid crystal element; and (f) a projection lens that enlarges and projects an image formed by the liquid crystal element, the first polarizing element, and the second polarizing element. (g) The liquid crystal element has a first surface that includes the position of the focus and is substantially orthogonal to the optical axis of the projection lens, and at least one second surface that is disposed around the first surface and is disposed in a direction inclined with respect to the optical axis of the projection lens. The second surface is disposed such that light enters the liquid crystal layer of the liquid crystal element from the best viewing orientation of the liquid crystal element or an orientation within a range of ±90° or less in the azimuth direction with respect to the best viewing orientation. [2]One aspect of the vehicle lighting system according to the present invention includes the lighting device of [1] and a controller that is connected to the lighting device and performs operation control.

[0006] According to the above configuration, it is possible to improve the brightness of the irradiation light in a lighting device or the like using a liquid crystal element.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0008] Fig. 1(A) is a diagram showing the configuration of a vehicle lamp system according to an embodiment. The vehicle lamp system shown in Fig. 1(A) includes a vehicle lamp (lamp unit) 1, a controller 2, and a camera 3. This vehicle headlamp system detects the positions of front vehicles, pedestrians' faces, etc. existing around the host vehicle based on the image captured by the camera 3, sets a certain range including the positions of the front vehicles, etc. as a non-irradiation range (dimming area), sets the other ranges as light irradiation ranges, performs selective light irradiation, and irradiates the road surface with light of various shapes.

[0009] The vehicle lamp 1 is disposed at a predetermined position in the front part of the vehicle and forms irradiation light for illuminating the front of the vehicle. Note that one vehicle lamp 1 is provided on each of the left and right sides of the vehicle, but only one is shown here.

[0010] The controller 2 controls the operations of the light source 10 and the liquid crystal element 15 of the vehicle lamp 1. This controller 2 is realized by using a computer system having, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and causing the computer system to execute a predetermined operation program. The controller 2 of the present embodiment turns on the light source 10 according to the operation state of a light switch (not shown) installed in the driver's seat, and sets a light distribution pattern corresponding to an object such as a preceding vehicle (oncoming vehicle, preceding vehicle), a pedestrian, a road sign, a road white line, etc. detected by the camera 3, and supplies a control signal for forming an image corresponding to this light distribution pattern to the liquid crystal element 15.

[0011] The camera 3 captures an image of the front space of the host vehicle to generate an image, and performs a predetermined image recognition process on this image to detect the position, range, size, type, etc. of the object such as the preceding vehicle described above. The detection result by the image recognition process is supplied to the controller 2 connected to the camera 3. The camera 3 is installed at a predetermined position inside the vehicle compartment of the host vehicle (for example, the upper part of the windshield), or at a predetermined position outside the vehicle compartment of the host vehicle (for example, inside the front bumper). When the vehicle is equipped with a camera for other purposes (for example, an automatic braking system, etc.), that camera may be shared.

[0012] Note that the function of the image recognition process in the camera 3 may be replaced by the controller 2. In that case, the camera 3 outputs the generated image to the controller 2, and the image recognition process is performed on the controller 2 side based on this image. Alternatively, both the image and the result of the image recognition process based on it from the camera 3 may be supplied to the controller 2. In that case, the controller 2 may further perform an independent image recognition process using the image obtained from the camera 3.

[0013] The vehicle lamp 1 shown in Fig. 1(A) includes a light source 10, reflectors (reflective members) 11 and 13, a polarizing beam splitter 12, a quarter-wave plate 14, a liquid crystal element 15, an optical compensation plate 16, a polarizing plate 17, and a projection lens 18. These elements are, for example, housed in one housing (case) and integrated. Also, the light source 10 and the liquid crystal element 15 are each connected to a controller 2. In this embodiment, the polarizing beam splitter 12 corresponds to the "first polarizing element", and the polarizing plate 17 corresponds to the "second polarizing element".

[0014] The light source 10 emits light under the control of the controller 2. This light source 10 is composed of, for example, a light-emitting element such as several white LEDs (Light Emitting Diodes) and a drive circuit. Note that the configuration of the light source 10 is not limited to this. For example, as the light source 10, a laser element, or even a light source generally used in vehicle lamps such as an incandescent lamp or a discharge lamp can be used.

[0015] The reflector 11 is arranged corresponding to the light source 10, reflects and condenses the light emitted from the light source 10 so that the light converges at a predetermined position, guides it in the direction of the polarizing beam splitter 12, and makes it incident on the liquid crystal element 15. The reflector 11 is, for example, a reflecting mirror having an elliptical reflecting surface. In this case, the light source 10 can be arranged near the focal point of the reflecting surface of the reflector 11. Note that a condenser lens may be used as the condensing part instead of the reflector 11.

[0016] The polarizing beam splitter 12 is a transmissive-reflective type polarizing element that transmits polarized light in a specific direction of the incident light and reflects polarized light in a direction orthogonal to this, and is arranged on the light incident surface side of the liquid crystal element 15. As such a polarizing beam splitter 12, for example, a wire grid type polarizing element or a multilayer film polarizing element can be used.

[0017] The reflector 13 is provided at a position where the light reflected by the polarizing beam splitter 12 can be incident, and reflects the incident light in the direction of the polarizing beam splitter 12.

[0018] The quarter-wave plate 14 is disposed on the optical path between the polarization beam splitter 12 and the reflector 13, and imparts a phase difference to the incident light. In the present embodiment, the light reflected by the polarization beam splitter 12 passes through the quarter-wave plate 14, is reflected by the reflector 13, and passes through the quarter-wave plate 14 again, whereby the polarization direction is rotated by 90° and the light re-enters the polarization beam splitter 12. Thereby, the re-entering light is in a state where it is more likely to pass through the polarization beam splitter 12, so the utilization efficiency of the light is improved. Instead of the quarter-wave plate 14, as shown in the vehicle lamp 1a of the modified embodiment shown in Fig. 1(B), a half-wave plate 14a may be arranged at a position where the reflected light from the reflector 13 enters without the reflected light from the polarization beam splitter 12 entering.

[0019] The liquid crystal element 15 is disposed at a position including the focal points of the light reflected and condensed by the reflectors 11 and 13, respectively, and is arranged so that the light is incident thereon. The liquid crystal element 15 includes a plurality of pixel portions (light modulation portions) that can be independently controlled. In the present embodiment, the liquid crystal element 15 has a driver (not shown) for applying a driving voltage to each pixel portion. The driver applies a driving voltage for driving each pixel portion of the liquid crystal element 15 individually based on a control signal supplied from the controller 2. As shown in the figure, the light incident on the liquid crystal element 15 is incident at a wide angle with respect to the light incident surface of the liquid crystal element 15. Specifically, the light is incident at a wide angle of about 40° to 60° with respect to the normal direction of the light incident surface.

[0020] The optical compensation plate 16 is for compensating the phase difference of the light transmitted through the liquid crystal element 15 and increasing the degree of polarization, and is disposed on the light exit surface side of the liquid crystal element 15. Specifically, the phase difference of the optical compensation plate 16 is set so that the phase difference added to the phase difference of the liquid crystal layer 15 becomes 0 or a value close thereto. The optical compensation plate 16 may be omitted.

[0021] The polarizing plate 17 is disposed on the light-emitting surface side of the liquid crystal element 15. The polarizing beam splitter 12, the polarizing plate 17, and the liquid crystal element 15 disposed therebetween form an image corresponding to the light distribution pattern of the light irradiated forward of the host vehicle.

[0022] The projection lens 18 is disposed at a position where the light reflected and condensed by the reflectors 11 and 13 and transmitted through the liquid crystal element 15 can be incident, and projects the incident light forward of the host vehicle. The projection lens 18 is disposed such that its focal point corresponds to the position of the liquid crystal layer of the liquid crystal element 15. The optical axis of the projection lens 18 extends along the left-right direction in the figure as indicated by the one-dot chain line in the figure.

[0023] FIG. 2(A) is a schematic cross-sectional view showing a configuration example of the liquid crystal element. Here, a segment display type liquid crystal element is exemplified. Specifically, the exemplified liquid crystal element 15 includes a first substrate 51 and a second substrate 52 disposed opposite to each other, a plurality of wiring portions 53, a common electrode (opposing electrode) 54, an insulating layer (insulating film) 55, a plurality of pixel electrodes 56, alignment films 57 and 58, and a liquid crystal layer 59.

[0024] The first substrate 51 and the second substrate 52 are each, for example, a rectangular substrate in plan view and are disposed opposite to each other. As each substrate, for example, a light-transmissive substrate such as a glass substrate or a plastic substrate can be used. Spherical spacers (not shown) made of, for example, a resin film are dispersedly disposed between the first substrate 51 and the second substrate 52, and the substrate gap is maintained at a desired size (for example, about several μm) by these spherical spacers. Note that instead of the spherical spacers, columnar bodies made of resin or the like may be provided on the first substrate 51 side or the second substrate 52 side and used as spacers. In the present embodiment, it is assumed that the substrates are arranged such that the first substrate 51 faces the polarizing plate 17 and the second substrate 52 faces the polarizing beam splitter 12. That is, it is assumed that the first substrate 51 side is the light-emitting side of the liquid crystal element 15 and the second substrate 52 is the light-incident side of the liquid crystal element 15.

[0025] The plurality of wiring portions 53 are provided on the lower layer side of the insulating layer 55 on one side of the second substrate 52. These wiring portions 53 are formed by appropriately patterning a transparent conductive film such as indium tin oxide (ITO). Each wiring portion 53 is for applying a voltage from a driver to each pixel electrode 56.

[0026] The common electrode 54 is provided on one side of the first substrate 51. The common electrode 54 is integrally provided so as to face each pixel electrode 56 of the second substrate 52. The common electrode 54 is formed by appropriately patterning a transparent conductive film such as indium tin oxide (ITO).

[0027] The insulating layer 55 is provided on the upper side of each wiring portion 53 so as to cover them on one side of the second substrate 52. In this embodiment, the insulating layer 55 is provided so as to cover substantially the whole on one side of the second substrate 52. This insulating layer 55 is, for example, a SiO2 film or a SiON film, and can be formed by a vapor phase process such as a sputtering method or a solution process. Note that an organic insulating film may be used as the insulating layer 55. The layer thickness of the insulating layer 55 is, for example, about 1 μm.

[0028] The plurality of pixel electrodes 56 are provided on the upper side of the insulating layer 55 on one side of the second substrate 52. These pixel electrodes 56 are formed by appropriately patterning a transparent conductive film such as indium tin oxide (ITO). In this embodiment, a pixel portion is formed at a portion where each pixel electrode 56 and the common electrode 54 face each other.

[0029] Each pixel electrode 56 is physically and electrically connected to any one of the wiring portions 53 through a through hole provided in the insulating layer 55. Thus, by providing each pixel electrode 56 and each wiring portion 53 in different layers, it is not necessary to provide wiring between the pixel electrodes 56, so that the gap between the pixel electrodes 56 can be reduced, the aperture ratio can be improved, and the amount of transmitted light can be increased. In addition, the degree of freedom in layout of each wiring portion 53 is also increased.

[0030] The alignment film 57 is disposed above the pixel electrodes 56 so as to cover them on one surface side of the first substrate 51. The alignment film 58 is disposed above the common electrode 54 so as to cover it on one surface side of the second substrate 52. These alignment films 57 and 58 are for regulating the alignment state of the liquid crystal layer 59. Each of the alignment films 57 and 58 is subjected to a uniaxial alignment treatment such as rubbing treatment, etc., and has a uniaxial alignment regulating force for defining the alignment of the liquid crystal molecules in the liquid crystal layer 59 along that direction. The directions of the alignment treatment for each of the alignment films 57 and 58 are set, for example, to be staggered (antiparallel). The pretilt angle in the vicinity of the interface between each of the alignment films 57 and 58 and the liquid crystal layer 59 is, for example, about 89°.

[0031] The liquid crystal layer 59 is provided between the first substrate 51 and the second substrate 52. The liquid crystal layer 59 is formed, for example, using a nematic liquid crystal material having fluidity. In this embodiment, the liquid crystal layer 59 has a negative dielectric anisotropy and is formed using a liquid crystal material to which a left-handed chiral material is added. The addition amount of the chiral material can be set, for example, so that d / p = 0.31. Here, d is the layer thickness of the liquid crystal layer 59, and p is the chiral pitch. The layer thickness of the liquid crystal layer 59 can be, for example, about 4 μm.

[0032] Note that, as long as the liquid crystal element 15 can freely modulate transmitted light to form a desired image, there are no particular limitations on its internal structure or driving method. For example, in the above-described configuration example, an example where the wiring and the pixel electrode are formed in different layers is shown, but it is not limited thereto, and they may be formed in the same layer. Further, as the liquid crystal element 15, an active matrix type liquid crystal element configured by associating a thin film transistor with each pixel may be used, or a simple matrix type liquid crystal element in which a plurality of stripe-shaped transparent electrodes are arranged opposite to each other and each region where the transparent electrodes overlap is used as a pixel portion may be used. Furthermore, as the liquid crystal element 15, a segment display type liquid crystal element having a plurality of pixel electrodes of arbitrary shapes provided on one substrate and one (or a plurality of) counter electrodes provided on the other substrate may be used. In this case, multiplex driving or static driving may be adopted for the driving method.

[0033] FIG. 2(B) is a diagram for explaining the direction of the uniaxial alignment treatment for each alignment film. Here, the direction of the uniaxial alignment treatment for each alignment film when the liquid crystal element 15 is viewed in plan from the first substrate 11 side is shown. As shown in the figure, for example, it is assumed that the transmission axis b1 of the polarizing plate 17 on the front side (light emitting side) is arranged in the 90° - 270° azimuth, and the transmission axis b2 of the polarizing beam splitter 12 on the back side (light incident side) is arranged in the 0° - 180° azimuth. Then, the direction a1 of the uniaxial alignment treatment in the alignment film 57 of the first substrate 51 corresponding to the front side is set to the 225° azimuth, and the direction a2 of the uniaxial alignment treatment in the alignment film 58 of the second substrate 52 corresponding to the back side is set to the 45° azimuth. That is, the directions a1 and a2 of each uniaxial alignment treatment are arranged so as to form an angle of 45° with respect to the respective transmission axes b1 and b2. In practice, due to positional deviation during manufacturing or the like, a difference may occur in the relative angle. Therefore, the relative angle between the directions a1 and a2 of the uniaxial alignment treatment with respect to the respective transmission axes b1 and b2 is allowed to be in the range of, for example, about 45° ± 5°.

[0034] The alignment film 57 of the first substrate 51 has a uniaxial alignment regulating force along the direction a1 in the initial state where no voltage is applied to the liquid crystal layer 59, and the alignment film 58 of the second substrate 52 has a uniaxial alignment regulating force along the direction a2 in the initial state where no voltage is applied to the liquid crystal layer 59. Thereby, the liquid crystal layer 59 becomes a uniform alignment (monodomain alignment) that receives the uniaxial alignment regulating force from the respective alignment films 57 and 58 in the initial alignment state. Also, when a voltage is applied to the liquid crystal layer 59, the alignment direction of the liquid crystal molecules changes so as to fall in a direction approaching horizontal to the substrate surfaces of the respective substrates 51 and 52, and a twisted alignment is manifested under the influence of the chiral material. For example, when a voltage of 2.5 times or more the threshold voltage of the liquid crystal material is applied to the liquid crystal layer 59, the substantial alignment direction of the liquid crystal molecules is in the 180° azimuth (direction c1 in the drawing) near the interface between the liquid crystal layer 59 and the first substrate 51 corresponding to the front side, and the substantial alignment direction of the liquid crystal molecules is in the 90° azimuth (direction c2 in the drawing) near the interface between the liquid crystal layer 59 and the second substrate 52 corresponding to the back side.

[0035] FIG. 3(A) is a diagram showing a measurement example of the transmittance characteristics of the liquid crystal element. Also, FIG. 3(B) is a diagram for explaining the arrangement of the measurement system in the transmittance measurement. As shown in FIG. 3(B), the polar angle θ is defined with reference to an axis substantially orthogonal to each substrate surface of the liquid crystal element, and the azimuth angle φ is defined with reference to an axis substantially horizontal to each substrate surface of the liquid crystal element. The relative arrangement relationship between the liquid crystal element and each polarizing plate (front-side polarizing plate, back-side polarizing plate) is as shown in FIG. 2(B). In this measurement system, the light from the light source is configured to pass through the liquid crystal element and be received by the light receiver, and the polar angle θ and the azimuth angle φ can be variably set at that time.

[0036] In Fig. 3(A), axes are set concentrically with respect to the polar angle θ, the center of the circle corresponding to the polar angle θ = 0°, and the outermost circumference corresponding to the polar angle θ = 40°. Also, with respect to the azimuth angle φ, the left - right direction in the figure corresponds to 0° - 180°, and the up - down direction in the figure corresponds to 90° - 270°. Further, this measurement example is for the case where a sufficiently high voltage (for example, 12 V), which is 2.5 times or more the threshold voltage, is applied to the liquid crystal layer 59 of the liquid crystal element 15. As shown in the figure, the best viewing azimuth is the azimuth of φ = 225° (half - past - seven azimuth), and as shown by the specific numerical example of the transmittance at this azimuth in the figure, the transmittance tends to increase as the polar angle θ increases. Also, the transmittance is relatively high at two azimuths orthogonal to the best viewing azimuth, but the transmittance is relatively low in the anti - viewing direction (the azimuth of φ = 45°), which is an azimuth different from the best viewing azimuth by 180°. This is because in the liquid crystal layer 59 when a voltage is applied, a monodomain alignment occurs in which the liquid crystal molecules are inclined and aligned in one direction. That is, it can be said that the transmittance relatively increases in the range from the best viewing azimuth to ±90° or less (the range from 135° to 315°) with the best viewing azimuth as a reference, and conversely, the transmittance relatively decreases in the range from the anti - viewing azimuth to less than ±90° (the range greater than 315° and up to 0° and the range from 0° to less than 135°) with the anti - viewing azimuth as a reference. Note that such a tendency is the same when the above - described polarizing beam splitter 12 is used as the polarizing element, and is also the same when a transmissive - reflective polarizing plate using an optical multilayer film is used. From the above discussion, by arranging the liquid crystal element 15 (specifically, the liquid crystal layer 59) to tilt corresponding to the best viewing azimuth or an azimuth within ±90° or less thereof (more preferably, within the range from ±45° or less from the best viewing azimuth), it is possible to obtain the knowledge that the maximum luminous intensity of the irradiation light from the vehicle lamp 1 can be increased by utilizing the transmittance when the above - described polar angle θ is increased.

[0037] FIG. 4(A) is a diagram showing a configuration (reference configuration) when the liquid crystal element is not tilted. Here, for easy understanding of the explanation, the main components, i.e., the liquid crystal element 15, the polarizing beam splitters 12 and 17 before and after it, and the projection lens 18, are shown. Also, the illustrated light propagation direction is the propagation direction of the light incident on the liquid crystal element 15 in FIG. 1, specifically, an axis that is horizontal in the left - right direction in FIG. 1 and passes through the liquid crystal element 15. Further, the light propagation direction is parallel to the optical axis of the projection lens 18. The optical axis of the projection lens 18 mentioned here is an imaginary straight line passing through the center and the focal point of the projection lens 18.

[0038] Based on the arrangement shown in FIG. 4(A), an axis parallel to each substrate of the liquid crystal element 15 and along the left - right direction (the direction orthogonal to the paper surface) of the liquid crystal element 15 is defined as the x - axis, and an axis parallel to each substrate of the liquid crystal element 15 and along the up - down direction (the up - down direction of the paper surface) of the liquid crystal element 15 is defined as the y - axis. Both the x - axis and the y - axis are axes that intersect the light propagation direction. In the present embodiment, the x - axis corresponds to the 0° - 180° direction shown in FIG. 2(B) described above, and the y - axis corresponds to the 90° - 270° direction shown in FIG. 2(B) described above. Also, in the arrangement shown in FIG. 4(A), the x - axis corresponds to the left - right direction of the vehicle lamp 1, and the y - axis corresponds to the up - down direction of the vehicle lamp 1. In the state shown in FIG. 4(A), the rotation angles of the liquid crystal element 15 about the x - axis and the y - axis are both 0°. Also, the alignment direction of the liquid crystal molecules at approximately the center in the layer - thickness direction in the liquid crystal layer 59 of the liquid crystal element 15 is set as the 45° azimuth in FIG. 3(B). This is a direction that makes an angle of 45° with respect to each of the x - axis and the y - axis in the figure.

[0039] FIG. 4(B) is a diagram showing a configuration example when the liquid crystal element is disposed obliquely. In the illustrated example, the liquid crystal element 15 is disposed by being rotated by a predetermined angle about the x-axis. The clockwise rotation angle in the figure is defined as positive, and the counterclockwise rotation angle is defined as negative. In the illustrated example, the rotation angle in the x-axis direction is set to a negative value. By disposing the liquid crystal element 15 obliquely so as to be non-orthogonal and non-parallel to the optical axis of the projection lens 18 in this way, the light propagation direction intersects the liquid crystal layer 59 of the liquid crystal element 15 obliquely. In other words, the liquid crystal element 15 is disposed so that the optical axis of the projection lens 18 and the layer thickness direction of the liquid crystal layer 59 form an angle greater than 0° and less than 90°. Although not shown, the liquid crystal element 15 can be disposed at a position rotated by a predetermined angle about the y-axis in the same manner. Further, as shown in FIG. 4(C), the liquid crystal element 15 can be disposed at a position rotated by a predetermined angle about both the x-axis and the y-axis.

[0040] FIGS. 5(A) to 5(C) are diagrams showing measurement examples of the relative luminous intensity at the center of the projected image 10 m ahead of the light emitted from the projection lens. Specifically, with the luminous intensity of the transmitted light in the reference arrangement shown in FIG. 4(A) being set to 100%, it is a graph obtained by determining the rotational angle dependence of the luminous intensity ratio. FIG. 5(A) shows the rotational angle dependence of the luminous intensity ratio when the liquid crystal element 15 is rotated and disposed about the x-axis. This arrangement corresponds to the case of rotating about the 0°-180° azimuth in FIG. 3(B) described above. It can be seen that the luminous intensity ratio increases at the rotation angle corresponding to the case of rotating to the 270° azimuth where the transmittance increases, that is, at the rotation angle with a negative value, and the luminous intensity ratio decreases at the rotation angle with a positive value. That is, in this measurement example, the negative rotation angle corresponds to the range within ±90° of the optimum viewing azimuth, and the positive rotation angle corresponds to the range within less than ±90° of the anti-viewing azimuth. Note that the rotation angle is up to ±40° in correspondence with the fact that the incident angle of light incident on the liquid crystal element 15 at a wide angle is generally in this range.

[0041] FIG. 5(B) shows the rotational angle dependence of the luminous intensity ratio when the liquid crystal element 15 is arranged by rotating it around the y-axis. This arrangement corresponds to the case where it is rotated around the 90°-270° azimuth in FIG. 3(B) described above. It can be seen that the luminous intensity ratio increases at a rotational angle corresponding to the case of rotating to the 180° azimuth where the transmittance increases, that is, at a negative rotational angle, and decreases at a positive rotational angle. That is, in this measurement example, the negative rotational angle corresponds to the range within ±90° of the optimal viewing azimuth, and the positive rotational angle corresponds to the range less than ±90° of the anti-viewing azimuth.

[0042] FIG. 5(C) shows the rotational angle dependence of the luminous intensity ratio when the liquid crystal element 15 is arranged by rotating it around the x-axis and the y-axis. This arrangement corresponds to the case where it is rotated around the 135°-315° azimuth in FIG. 3(B) described above. It can be seen that the luminous intensity ratio increases at a rotational angle corresponding to the case of rotating to the 225° azimuth where the transmittance increases, that is, at a negative rotational angle, and decreases at a positive rotational angle. That is, in this measurement example, the negative rotational angle corresponds to the range within ±90° of the optimal viewing azimuth, and the positive rotational angle corresponds to the range less than ±90° of the anti-viewing azimuth. Also, the increase in the luminous intensity ratio is larger compared to the case where only the x-axis or only the y-axis is the center.

[0043] In this way, by arranging the liquid crystal element 15 in an inclined manner such that the light propagation direction (the optical axis L of the projection lens 18) intersects obliquely with the liquid crystal layer 59, it is possible to increase the luminous intensity ratio. That is, it is possible to improve the luminous intensity (brightness) of the irradiation light emitted from the vehicle lamp 1. However, when the liquid crystal element 15 itself is inclined, the layer thickness of the liquid crystal layer 59 in the light propagation direction increases. If the liquid crystal layer thickness is d and the inclination angle of the liquid crystal element 15 is θ, the substantial liquid crystal layer thickness when the liquid crystal element 15 is inclined is d / cosθ. However, if an optical compensation plate having negative uniaxial optical anisotropy is arranged between the liquid crystal element 15 and the polarizing beam splitter 12 or between the liquid crystal element 15 and the polarizing plate 17, the increase in retardation due to the increase in the substantial liquid crystal layer thickness can be optically compensated. However, if the wavelength distributions of the refractive indices of the liquid crystal layer and the optical compensation plate do not match, complete optical compensation cannot be obtained over the entire visible wavelength range and light leakage may occur. Also, since the polarizing plate 17 on the emission side of the liquid crystal element 15 is inclined relative to the liquid crystal element 15, light leakage may occur due to the shift of the absorption axis.

[0044] Fig. 6 illustrates the planar structure of the liquid crystal element 15. In the illustrated liquid crystal element 15, it can be said that it is preferable to arrange the liquid crystal element 15 such that the light propagation direction becomes the normal direction of the incident surface / emission surface of the liquid crystal element 15 particularly in the "high illuminance band" where the luminous intensity of the projection light near the center is high. This high illuminance band is, for example, a portion that contributes to the light distribution near the center in front of the vehicle and is a portion where the light is focused. On the other hand, when the projection light becomes spot light in order to increase the luminous intensity in the high illuminance band, in order to increase the luminous intensity at a position away from the center, by making the light propagation direction (the optical axis L of the projection lens 18) inclined rather than the normal direction with respect to the incident surface / emission surface of the liquid crystal element 15, it is considered possible to suppress the light leakage in the high illuminance band and increase the luminous intensity in the wide region other than the high illuminance band to improve the light utilization efficiency. Hereinafter, based on such findings, a configuration example of the liquid crystal element 15 applicable to the vehicle lamp 1 will be described. In the following, in order to distinguish each configuration example, the reference numerals attached to the liquid crystal elements are appropriately set as 15a, 15b, 15c, and 15d. All are configuration examples applicable as the liquid crystal element 15 in the vehicle lamp 1 described above.

[0045] Figs. 7(A) and 7(B) are schematic perspective views showing a configuration example of a liquid crystal element applicable to a vehicle lamp. In the liquid crystal element 15a of the configuration example shown in Fig. 7(A), the high-luminance band described above is arranged in association with a position P that intersects the optical axis L. For a certain range (first surface) including this position P, the optical axis L of the projection lens 18 and the incident surface / exit surface of the liquid crystal element 15a are configured to be substantially orthogonal. Also, in the X direction in the figure, outside a certain range (second surface) including the position P, the liquid crystal element 15a is curved. Such a curved liquid crystal element 15a can be realized, for example, by using a resin substrate as the first substrate 51 and the second substrate 52, or by using a thin glass substrate.

[0046] Fig. 8 is a schematic cross-sectional view showing the structure of the liquid crystal layer in the liquid crystal element of the configuration example shown in Fig. 7(A). Fig. 8 corresponds to a cross-section viewed from the Y direction shown in Fig. 7(A). As shown in the figure, the liquid crystal layer 59 of the liquid crystal element 15a has a shape along the shapes of the first substrate 51 and the second substrate 52 that are arranged to face each other with the liquid crystal layer 59 therebetween. Specifically, it has a flat and plate-shaped first portion 59a and two curved second portions 59b arranged on both sides thereof. In this liquid crystal element 15a, the light incident side interface 59c and the light exit side interface 59d of the first portion 59a are substantially orthogonal to the optical axis L of the projection lens 18, and the light incident side interface 59e and the light exit side interface 59f of each second portion 59b are arranged in a direction obliquely intersecting the optical axis L of the projection lens 18.

[0047] In this liquid crystal element 15a, it can be said that at least the light incident side interface 59c of the first portion 59a corresponds to the first surface described above, and at least the light incident side interface 59e of each second portion 59b corresponds to the second surface described above. In other words, in the liquid crystal element 15a, the surface on the side that does not contact the liquid crystal layer 59 and overlaps the first portion 59a of the first substrate 51 to the second substrate 52 corresponds to the first surface, and the surface on the side that does not contact the liquid crystal layer 59 and overlaps each second portion 59b of the first substrate 51 to the second substrate 52 can also be considered to correspond to the second surface. By arranging in this way, light can be incident on the second portion 59b of the liquid crystal element 15a from the best viewing orientation or an orientation within a range of ±90° or less based on this.

[0048] Although illustration and detailed description are omitted, the liquid crystal element having the configuration example shown in FIG. 7(B) also has a similar liquid crystal layer structure.

[0049] In the configuration example shown in FIG. 7(A), the left end side of the liquid crystal element 15a in the figure is curved so as to approach the polarizing plate 17 in the Z direction, and the right end side of the liquid crystal element 15a in the figure is curved so as to approach the polarization beam splitter 12 in the Z direction. That is, the liquid crystal element 15 is flat in a certain range including the position P, and both sides are curved in symmetric directions with this certain range in between. The liquid crystal element 15b having the configuration example shown in FIG. 7(B) is the same, except that the direction of curvature is changed to the Y direction in the figure.

[0050] By using these liquid crystal elements 15a and 15b, the light propagation direction can be inclined with respect to the incident surface / exit surface on both end sides of the liquid crystal elements 15a and 15b, so that the transmittance can be increased. In addition to curving both sides in the X direction of the liquid crystal element 15a and both sides in the Y direction of the liquid crystal element 15b as shown in the figure, the liquid crystal element itself may be configured to be bent so as to be inclined at a certain angle. When curved, it is considered that a wider projection light can be obtained by increasing the inclination angle as the distance from the central position P increases, and at the same time, it is considered that the glare at the center can be suppressed. Although the configuration example of the liquid crystal element curved in the X direction or the Y direction is shown in the illustrated example, it may be configured to be curved or bent in both the X direction and the Y direction.

[0051] FIG. 9(A) is a schematic perspective view showing a configuration example of a liquid crystal element applicable to a vehicle lamp. The liquid crystal element 15c in the configuration example shown in FIG. 9(A) includes a liquid crystal panel portion 20 having a flat liquid crystal layer 59 and configured in a flat plate shape, a first prism 21 disposed between the liquid crystal panel portion 20 and a polarization beam splitter 12, and a second prism 22 disposed between the liquid crystal panel portion 20 and a polarizing plate 17. The configuration of the liquid crystal panel portion 20 is the same as that of the liquid crystal element 15 shown in FIG. 2 described above. By using such a first prism 21 and a second prism 22, a function equivalent to the case where the liquid crystal element itself is curved or bent can be obtained. That is, by utilizing the refractive effect of light by the first prism 21 and the second prism 22, the light incident on the liquid crystal layer 59 of the liquid crystal panel portion 20 and the light emitted from the liquid crystal layer 59 can be made the same as in the case of using the liquid crystal element 15a shown in FIG. 7(A) described above. Note that the "prism" in this specification refers to an optical element capable of obtaining at least an action of refracting light.

[0052] In the illustrated example, the first prism 21 and the second prism 22 are shown separated from the liquid crystal panel portion 20 for easy understanding of the configuration. However, it is preferable that the first prism 21 and the second prism 22 are each disposed in close contact with the liquid crystal panel portion 20. In that case, it is preferable to arrange an optically matching adhesive between each of the first prism 21 and the second prism 22 and the liquid crystal panel portion 20 to achieve bonding. Thereby, light loss at the interface can be suppressed.

[0053] The first prism 21 has a flat surface on the side facing the liquid crystal panel section 20 and has another surface that is partially curved and inclined on the side not facing the liquid crystal panel section 20. The shape of the inclined surface of the first prism 21 can be the same as the case where the liquid crystal element 15a itself is curved as shown in FIG. 7(A) described above. Specifically, the other surface of the first prism 21 has a flat first surface that is substantially orthogonal to the optical axis L of the projection lens 18 within a certain range including the position where it intersects the optical axis L of the projection lens 18. Outside a certain range in the X direction in the figure, on the right side in the figure, it curves so as to gradually approach the polarization beam splitter 12, and on the left side in the figure, it has a second surface that curves and inclines so as to gradually move away from the polarization beam splitter 12.

[0054] Similarly, the second prism 22 has a flat surface on the side facing the liquid crystal panel section 20 and has another surface that is partially curved and inclined on the side not facing the liquid crystal panel section 20. The shape of the inclined surface of the second prism 22 can be the same as the case where the liquid crystal element 15a itself is curved as shown in FIG. 7(A) described above. Specifically, the other surface of the second prism 22 has a flat first surface that is substantially orthogonal to the optical axis L of the projection lens 18 within a certain range including the position where it intersects the optical axis L of the projection lens 18. Outside a certain range in the X direction in the figure, on the left side in the figure, it curves so as to gradually approach the polarizing plate 17, and on the right side in the figure, it has a second surface that curves so as to gradually move away from the polarizing plate 17.

[0055] Note that, regarding the direction of curvature of each of the other surfaces of the first prism 21 and the second prism 22, in the illustrated example, it is in one direction, but it is also possible to curve it in two directions. As the material of each of the first prism 21 and the second prism 22, for example, glass, quartz, acrylic resin, etc. can be used.

[0056] FIG. 9(B) is a schematic perspective view showing a configuration example of a liquid crystal element applicable to a vehicle lamp. The liquid crystal element 15d in the configuration example shown in FIG. 9(B) includes a liquid crystal panel portion 20 configured in a flat plate shape with a flat plate-shaped liquid crystal layer 59, a first flat plate-shaped prism 21a disposed between the liquid crystal panel portion 20 and the polarization beam splitter 12, and a second flat plate-shaped prism 22a disposed between the liquid crystal panel portion 20 and the polarizing plate 17. The configuration of the liquid crystal panel portion 20 is the same as that of the liquid crystal element 15 shown in FIG. 2 described above. By using such a first flat plate-shaped prism 21a and second flat plate-shaped prism 22a, a function equivalent to that in the case of curving the liquid crystal element itself can be obtained. That is, the light incident on the liquid crystal layer of the liquid crystal panel portion 20 and the light emitted from the liquid crystal layer can be made the same as in the case of using the liquid crystal element 15a shown in FIG. 7(A) described above. Further, the first flat plate-shaped prism 21a and the second flat plate-shaped prism 22a are flat plate-shaped prisms configured in a Fresnel lens shape, and compared with the first prism 21 and the second prism 22 shown in FIG. 9(A), the optical system including the liquid crystal element 15d can be made more compact.

[0057] The first flat plate-shaped prism 21a has a flat surface on the side facing the liquid crystal panel portion 20 and an other surface that is partially curved and inclined on the side not facing the liquid crystal panel portion 20. The other surface of the first flat plate-shaped prism 21a has a flat first surface that is substantially orthogonal to the optical axis L of the projection lens 18 within a certain range including the position where it intersects the optical axis L of the projection lens 18, and has a second surface formed of a cross-sectionally serrated uneven surface outside a certain range in the X direction in the figure.

[0058] The second flat plate-shaped prism 22a has a flat surface on the side facing the liquid crystal panel portion 20 and an other surface that is partially curved and inclined on the side not facing the liquid crystal panel portion 20. The other surface of the second flat plate-shaped prism 22a has a flat first surface that is substantially orthogonal to the optical axis L of the projection lens 18 within a certain range including the position where it intersects the optical axis L of the projection lens 18, and has a second surface formed of a cross-sectionally serrated uneven surface outside a certain range in the X direction in the figure.

[0059] In the illustrated example, for the sake of clarity of the configuration, the first flat prism 21a and the second flat prism 22a are shown separated from the liquid crystal element 15d. However, it is preferable that the first flat prism 21a and the second flat prism 22a be arranged in close contact with the liquid crystal panel portion 20, respectively. In that case, it is preferable to arrange an optically matchable adhesive between each of the first flat prism 21a and the second flat prism 22a and the liquid crystal panel portion 20 for joining, thereby suppressing light loss at the interface.

[0060] The first flat prism 21a shown in Fig. 9(B) is formed by dividing the second surface on the other surface of the first prism 22 shown in Fig. 9(A) above into a plurality of regions and configuring it like a Fresnel lens, and has fine sawtooth-like uneven structures on both sides in the X direction. In the first flat prism 21a, the inclination angle of the surface of each fine prism constituting the uneven structure facing the polarization beam splitter 12 has an angular distribution that can pseudo-replicate the second surface of the first prism 21 shown in Fig. 9(A) above. Here, "pseudo-replicable" means that if the surfaces formed by the sawtooth-like uneven structures are joined together, the same surface as the second surface of the first prism 21 shown in Fig. 9(A) can be obtained and optically equivalent functions can be obtained. The inclination angle of the surface of the uneven structure increases as it approaches both ends in the X direction.

[0061] Similarly, the second flat prism 22a is formed by dividing the second surface on the other surface of the second prism 22 shown in Fig. 9(A) above into a plurality of regions and configuring it like a Fresnel lens, and has fine sawtooth-like uneven structures on both sides in the X direction. In the second flat prism 22a, the inclination angle of the surface of each fine prism constituting the uneven structure facing the polarizing plate 17 has an angular distribution that can pseudo-replicate the second surface of the second prism 22a shown in Fig. 9(A) above. Here, "pseudo-replicable" means that if the surfaces formed by the sawtooth-like uneven structures are joined together, the same surface as the second surface of the second prism 22 shown in Fig. 9(A) can be obtained and optically equivalent functions can be obtained. The inclination angle of the surface of the uneven structure increases as it approaches both ends in the X direction.

[0062] Note that, regarding the bending directions of the respective second surfaces of the first prism 21a and the second prism 22a, although they are in one direction in the illustrated example, it is also possible to bend them in two directions. As the material of each of the first prism 21a and the second prism 22a, for example, glass, quartz, acrylic resin, etc. can be used. Also, it may be molded with a mold using an ultraviolet effect type resin or the like on a flat glass substrate.

[0063] According to each of the above embodiments, it is possible to improve the brightness of the irradiation light in a lighting device or the like using a liquid crystal element.

[0064] Note that the present disclosure is not limited to the content of the above-described embodiments, and various modifications can be made and implemented within the scope of the gist of the present disclosure. For example, in the above-described embodiments, a vehicle lamp is cited as an example of a lighting device, but the application scope of the present disclosure is not limited thereto. For example, the configuration according to the present disclosure can be applied to various lighting devices such as street lamps, level crossing lighting devices, and direction guidance lighting devices. Also, the optical system of the vehicle lamp is not limited to the configuration of the above-described embodiments. Also, the configuration of the liquid crystal element is not limited to the configuration of the above-described embodiments. Also, in the above-described embodiments (the embodiments shown in FIGS. 8(A) and 8(B)), the first prism 21 to the first flat prism 21a are arranged between the liquid crystal panel unit 20 and the polarization beam splitter 12, but the positions of the polarization beam splitter 12 and the first prism 21 to the first flat prism 21a may be interchanged. That is, the polarization beam splitter 12 may be arranged between the first prism 21 to the first flat prism 21a and the liquid crystal panel unit 20. Similarly, the positions of the polarizing plate 17 and the second prism 22 to the second flat prism 22a may be interchanged, and the polarizing plate 17 may be arranged between the second prism 22 to the second flat prism 22a and the liquid crystal panel unit 20.

Explanation of Reference Numerals

[0065] 1: Vehicle lamp, 2: Controller, 3: Camera, 10: Light source, 11, 13: Reflector, 12: Polarizing beam splitter, 14: 1 / 2 wavelength plate, 15, 15a, 15b, 15c, 15d: Liquid crystal element, 16: Optical compensation plate, 17: Polarizing plate, 18: Projection lens, 20: Liquid crystal panel section, 21: First prism, 21a: First flat prism, 22: Second prism, 22a: Second flat prism, 51: First substrate 51, 52: Second substrate, 53: Wiring, 54: Common electrode (opposing electrode), 55: Insulating layer (insulating film), 56: Pixel electrode, 57, 58: Alignment film, 59: Liquid crystal layer

Claims

1. A light source, a condenser that condenses the light emitted from the light source so that the light forms a focus at a predetermined position, a liquid crystal element including a liquid crystal layer and disposed at a position including the focus, a first polarizing element disposed on the light incident surface side of the liquid crystal element, a second polarizing element disposed on the light emission surface side of the liquid crystal element, a projection lens that enlarges and projects an image formed by the liquid crystal element, the first polarizing element, and the second polarizing element, comprising: the liquid crystal element has a first surface that includes the position of the focus and is substantially orthogonal to the optical axis of the projection lens, and at least one second surface that is disposed around the first surface and is disposed in a direction inclined with respect to the optical axis of the projection lens, the second surface is disposed such that the light enters the liquid crystal layer of the liquid crystal element from the best viewing orientation of the liquid crystal element or an orientation within a range of ±90° or less in the azimuth direction based on the best viewing orientation, an illumination device.

2. the liquid crystal element is configured by disposing the liquid crystal layer between substrates disposed opposite to each other, the liquid crystal layer has a flat first portion and a bent or curved second portion. the first surface is provided on the first portion, the second surface is provided on the second portion, the illumination device according to claim 1.

3. the liquid crystal element has a flat liquid crystal panel portion having the flat liquid crystal layer disposed between substrates disposed opposite to each other, a first prism disposed between the liquid crystal panel portion and the first polarizing element, and a second prism disposed between the liquid crystal panel portion and the second polarizing element, the first prism has the first surface and the second surface provided on the side facing the first polarizing element, the second prism has the first surface and the second surface provided on the side facing the second polarizing element, the illumination device according to claim 1.

4. the liquid crystal element has a flat liquid crystal panel portion having the flat liquid crystal layer disposed between substrates disposed opposite to each other, a first flat prism disposed between the liquid crystal panel portion and the first polarizing element, and a second flat prism disposed between the liquid crystal panel portion and the second polarizing element, the first flat prism has the first surface and the second surface provided on the side facing the first polarizing element, the second flat prism has the first surface and the second surface provided on the side facing the second polarizing element, The second surface of the first flat prism and the second surface of the second flat prism are each pseudo-formed by a concavo-convex structure with a sawtooth cross-section. The lighting device according to claim 1.

5. Assuming that the first flat prism connects the surfaces facing the first polarizing element of the sawtooth cross-sectional concavo-convex structure, the second surface is reproduced, and an optically equivalent function can be obtained. Assuming that the second flat prism connects the surfaces facing the second polarizing element of the sawtooth cross-sectional concavo-convex structure, the second surface is reproduced, and an optically equivalent function can be obtained. The lighting device according to claim 4.

6. The first polarizing element and / or the second polarizing element is a transmissive-reflective polarizing plate or an optical multilayer film polarizing plate having a wire grid. The lighting device according to any one of claims 1 to 5.

7. The liquid crystal element is a liquid crystal element with monodomain vertical alignment. The lighting device according to any one of claims 1 to 6.

8. A vehicle lighting system including the lighting device according to any one of claims 1 to 7 and a controller connected to the lighting device for performing operation control.

Images