Headlight device

Abstract

To provide a headlight device for vehicle capable of generating and radiating illumination light excellent in visibility.SOLUTION: A headlight device for vehicle includes: a light source device generating light; optical means which is disposed on an optical axis of the light source device and projects light from the light source device so that it forms a desired light-distributing distribution; and a polarization direction conversion device changing a polarization direction of the light from the light source device. On the optical axis of light emitted from the light source device, the light source device, the polarization direction conversion device, and the optical means are disposed in this order. The polarization direction conversion device is composed of a liquid crystal panel. The light source device is provided with a first polarizer, and a second polarizer on an incident surface side of the liquid crystal panel comprising the polarization direction conversion device. The light passing the first polarizer of the light source device is made incident to the second polarizer on the incident surface side of the liquid crystal panel.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a headlight device for a vehicle that uses a solid-state light-emitting element. [Background technology]

[0002] With the remarkable development of solid-state light-emitting devices such as LEDs in recent years, lighting devices that use these solid-state light-emitting devices as light sources have been widely used in various lighting fixtures as light sources that are small, lightweight, consume little power, and are environmentally friendly and have a long lifespan.Furthermore, they have also been used as on-board electronic devices such as vehicle headlight devices that have excellent visibility and can be controlled in various ways.

[0003] For example, a conventional vehicle headlight device is already known from Patent Document 1 below, which includes a low beam LED light source array, a high beam LED light source array, a first optical light guide that receives and collimates the low beam light and high beam light from these LED light sources, and a second optical light guide that diffuses the collimated low beam light and high beam light as a combination of diffusion patterns, and in which these arrays and optical light guides are mechanically supported within a casing.

[0004] Furthermore, Patent Document 2 discloses a vehicle lamp that uses a laser light source as a light source and that can adjust brightness with a simple configuration, using a liquid crystal unit. Specifically, the liquid crystal unit is formed with a non-modulation area that can transmit laser light and a modulation area that changes the phase of the polarization component of the laser light by 90 degrees, and the brightness of the ambient light is adjusted by adjusting the range of the modulation area and the non-modulation area using a liquid crystal driver.

[0005] Additionally, Patent Document 3 below discloses an LED lighting device, particularly an LED headlight, that uses multiple LEDs as active light sources and emits light from the active light sources in a predetermined orientation via a collimation optical unit, a mixing optical unit, a field optical unit, etc. In particular, claim 25 and paragraph 0036 etc. state that additional optical elements, such as a polarizing or reshaping lens or reflector, may be arranged as a means for achieving that the light emitted from the active light source reaches the mixing optical system in a desired form. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Special Publication No. 2008-532250 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-207390 [Patent Document 3] Special Publication No. 2013-502679 Summary of the Invention [Problem to be solved by the invention]

[0007] LEDs, which are solid-state light sources, have become effective as light sources in vehicle headlamp devices due to their improved light-emitting efficiency. However, the above-mentioned conventional technology, Patent Document 1, is still insufficient in terms of light utilization efficiency and uniform illumination characteristics, and there is room for various improvements.

[0008] Furthermore, in Patent Document 2, the brightness of ambient light is adjusted by adjusting the range of the modulation area and the non-modulation area by a liquid crystal driver, with non-modulation areas and non-modulation areas formed in advance in the liquid crystal section, but there is no mention of obtaining illumination light with excellent visibility, including its polarized component, in response to the state of the area to be irradiated with illumination light, etc. Furthermore, Patent Document 3 uses additional optical elements such as a polarized lens or reflector as a means for light emitted from an active light source to reach the mixing optical system in a desired form, but there is no mention of obtaining illumination light with excellent visibility, including its polarized component.

[0009] Therefore, the present invention aims to provide a vehicle headlight device that uses a light source device that can be easily used as a modularized surface illumination light source, thereby achieving high utilization efficiency of light emitted from an LED light source, improving uniform illumination characteristics, and generating and emitting illumination light with better visibility by controlling the polarization component in accordance with the condition of the road surface onto which the light is irradiated, etc. [Means for solving the problem]

[0010] As one embodiment for achieving the above object, the vehicle headlight device of the present invention comprises a light source device that generates light, optical means that is arranged on the optical axis of the light source device and projects the light from the light source device so as to form a desired light distribution, and a polarization direction conversion device that changes the polarization direction of the light from the light source device, wherein the light source device, the polarization direction conversion device, and the optical means are arranged in this order on the optical axis of the light emitted from the light source device, the polarization direction conversion device is constituted by a liquid crystal panel, the light source device comprises a first polarizing plate and a second polarizing plate on the incident surface side of the liquid crystal panel that constitutes the polarization direction conversion device, and the light that has passed through the first polarizing plate of the light source device is incident on the second polarizing plate on the incident surface side of the liquid crystal panel. [Effects of the Invention]

[0011] According to the present invention, by using a light source device that can be manufactured at low cost, is small, can be easily modularized, and has high light utilization efficiency, it is possible to achieve the excellent effect of providing a headlight device for a vehicle that consumes low power, is environmentally friendly, has a long life, and is capable of controlling the polarization direction for each illumination area in accordance with a control signal, thereby obtaining light that is optimal for the driving scene. [Brief explanation of the drawings]

[0012] [Figure 1] 1A is a perspective view showing the overall configuration of a vehicle headlight device according to an embodiment of the present invention, which is applied as a headlight for an automobile, and FIG. 1B is a perspective view showing an enlarged view of a part of the vehicle headlight device; [Figure 2] 1A is a perspective view showing the overall configuration of a vehicle headlight device according to an embodiment of the present invention, and FIG. 1B is a perspective view showing the expanded configuration thereof. [Figure 3] 1A is a side cross-sectional view of the overall configuration of a vehicle headlight device according to a first embodiment of the present invention, and FIG. 1B is a side cross-sectional view of the overall configuration of a vehicle headlight device according to a modified example. [Figure 4] 1 is a perspective view showing the configuration of a visible light illumination unit centered around a collimator unit of a headlight device for a vehicle according to a first embodiment of the present invention. [Figure 5] 4 is a top cross-sectional view illustrating the operation of a visible light illumination unit centered around a collimator unit in the vehicle headlight device according to the first embodiment of the present invention. FIG. [Figure 6] 2 is a partially enlarged cross-sectional view showing the structure and operation of a collimator of a collimator unit in the vehicle headlight device according to the first embodiment of the present invention. FIG. [Figure 7] 1A is a developed perspective view showing the overall configuration of a polarization direction conversion device for a vehicle headlight device according to a first embodiment of the present invention, and FIG. 1B is a partially enlarged cross-sectional view thereof. [Figure 8] 1A is a diagram showing an arrangement of a polarization direction conversion device in a vehicle headlight device according to a first embodiment of the present invention, and FIG. 1B is a diagram showing an arrangement of a modification of the arrangement of the polarization direction conversion device in a vehicle headlight device according to a first embodiment of the present invention. [Figure 9]3A and 3B are state diagrams illustrating the operation of the polarization direction conversion device in the vehicle headlight device according to the first embodiment of the present invention when no voltage is applied (a) and when a voltage is applied (b). [Figure 10] 1A is an explanatory diagram illustrating headlight control in a headlight device for a vehicle according to a first embodiment of the present invention, and FIG. 1B is an explanatory diagram illustrating a headlight illumination area in a headlight device for a vehicle according to a first embodiment of the present invention. [Figure 11] 3 is a diagram showing an example of the angular characteristics of reflectance for a material with a refractive index of 1.5 for p-polarized light and s-polarized light in the vehicle headlight device according to the first embodiment of the present invention. FIG. [Figure 12] 10A is a developed perspective view showing the overall configuration of a vehicle headlight device according to a second embodiment of the present invention, and FIG. 10B is a side cross-sectional view thereof. [Figure 13] 10A is a perspective view illustrating the polarization state of a visible light illumination unit in a vehicle headlight device according to a second embodiment of the present invention, and FIG. 10B is a cross-sectional view thereof. [Figure 14] 10 is a graph showing the transmittance of a polarizing film against the wavelength of light incident on a polarizing mirror for s-polarized light and p-polarized light at different angles of incidence in a headlight device for a vehicle according to Example 2 of the present invention. [Figure 15] FIG. 10 is a characteristic diagram showing the spectral irradiance of sunlight in a vehicle headlight device according to a second embodiment of the present invention. [Figure 16] FIG. 10 is a perspective view showing the overall configuration of an infrared illumination unit in a vehicle headlight device according to a second embodiment of the present invention. [Figure 17] 10A is a developed perspective view showing the internal configuration of a vehicle headlight device according to a third embodiment of the present invention, and FIG. 10B is a cross-sectional view thereof. [Figure 18] FIG. 10 is an exploded perspective view of a modified example (fourth embodiment) of the headlight device of the present invention, in which the visible light illumination unit is small relative to the LCD panel. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments (examples) of the present invention will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to the following description, and various changes and modifications can be made by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in the drawings for explaining the present invention, parts having the same functions are denoted by the same reference numerals, and repeated explanations thereof may be omitted.

[0014] First, Fig. 1 shows a perspective view and a partial enlarged view of a vehicle 1 equipped with a vehicle headlight device using a solid-state light-emitting element according to an embodiment of the present invention. Fig. 1(a) shows the entire vehicle 1 equipped with a vehicle headlight device 100 of the present invention, and Fig. 1(b) shows an enlarged view of the headlight device portion of the vehicle.

[0015] Fig. 2(a) is an overall perspective view of the headlight device 100 shown in Fig. 1(b), and Fig. 2(b) shows its internal configuration in an exploded state. In addition, Fig. 3(a) shows a side cross section of the headlight device 100, and Fig. 3(b) shows a side cross section of a headlight device according to a modified example.

[0016] Example 1 As shown in these figures, the headlight device 100 is basically composed of a visible light illumination unit 10, which is a light source device, and a so-called projector lens 50, which is an optical system for irradiating the illumination light emitted from the illumination unit onto the space in front of the vehicle 1 and onto the road surface on which the vehicle 1 is traveling. Furthermore, instead of the projector lens 50, a reflecting mirror 60 may be used to configure the projection optics, or as shown in Fig. 3(b), the headlight device 100 may be composed of both the projector lens 50 and the reflecting mirror 60.

[0017] As is clear from these figures, in headlight device 100 according to the embodiment of the present invention, polarization direction conversion device 20 is arranged along the optical axis in part of the optical path of the illumination light from visible light illumination unit 10, to change (modulate) the polarization direction of the illumination light from visible light illumination unit 10. Note that, compared to Figure 3(a), the structure shown in Figure 3(b) allows for more precise control of the illumination direction and intensity due to the flexibility of the shape of the reflecting surface by bending the illumination light beam in a predetermined direction using reflecting mirror 60.

[0018] Next, each of the components of the headlight device 100 according to the embodiment of the present invention will be described in detail below.

[0019] <Visible light lighting unit> A visible light illumination unit 10, which is a light source device of the present invention, includes an LED substrate 11 on the front surface of which are mounted one or more semiconductor light source elements LEDs (Light Emitting Diodes), which are solid-state light sources (described later), and their control circuits, etc., and a heat sink 12 is attached to the back surface of the substrate to dissipate heat generated from the LEDs into the surrounding air. In this example, a total of 15 LEDs are arranged in a 5 (horizontal) x 3 (vertical) grid on the LED substrate 11. Furthermore, a collimator unit 13, which will be described below, is attached to the light-emitting surface side of the LED substrate 11.

[0020] As shown in Figure 4, this collimator unit 13 is constructed by arranging collimators 131 (in this example, 5 (horizontal) x 3 (vertical) = 15 pieces) on a plane inside a plate-shaped frame body, each collimator 131 corresponding to one or more LEDs 111 mounted on the LED substrate 11.

[0021] Each collimator 131 is formed of a translucent, heat-resistant resin such as polycarbonate or silicone. As shown in FIGS. 5 and 6, each collimator 131 has a cone-shaped outer peripheral surface 132 obtained by rotating a substantially parabolic cross section, and a recess 134 at its apex with a convex portion (i.e., a convex lens surface) 133 formed in its central portion. The central portion of the flat portion has a convex lens surface 135 (or a concave lens surface) that protrudes outward. The parabolic surface (outer peripheral surface) 132 that forms the cone-shaped outer peripheral surface of the collimator 131 is set within an angle range that allows total reflection of the light emitted from the LED 111 toward the periphery within the parabolic surface, or a reflective surface is formed on the surface. Such collimators can be easily and inexpensively manufactured, for example, by a general molding process.

[0022] On the other hand, the LEDs 111 are mounted at predetermined positions on the surface of the LED substrate 11, which is the circuit board on which they are mounted, and as is clear from the figure, this LED substrate 11 is positioned and fixed relative to the collimator 131 so that each LED 111 is located in the center of the recess 134 of the corresponding collimator 131.

[0023] With this configuration, the collimator 131 described above focuses light emitted from the LED 111, particularly light emitted upward from the central portion (to the right in the figure), into parallel light by two convex lens surfaces 133 and 135 formed on the LED light incident and exit surfaces of the collimator 131, as indicated by the arrows in the figure. Light emitted from other portions toward the periphery is also reflected by the parabolic surface (outer peripheral surface) 132 that forms the conical outer peripheral surface of the collimator 131, and similarly focuses and becomes parallel light. In other words, the collimator 131, which has a convex lens in its central portion and a parabolic surface (outer peripheral surface) 132 formed on its peripheral portion, can extract almost all of the light generated by the LED 111 as parallel light. This significantly improves the utilization efficiency of the generated light.

[0024] Next, as is clear from the drawing, a polarization conversion element 14 and further a convex lens 15 for controlling light distribution (a free-form surface, for example, which has a large degree of freedom in controlling light distribution, may be used as the lens surface) are attached to the front surface of the above-mentioned collimator unit 13. In this example, a specific polarized wave is selected and used by the polarization conversion element 14.

[0025] 5, the polarization conversion element 14 is configured by combining a plurality of light-transmitting members 141 in the shape of a column with a parallelogram cross section (hereinafter referred to as a parallelogram prism) and a plurality of light-transmitting members 142 in the shape of a column with a triangular cross section (hereinafter referred to as a triangular prism), which are arranged in an array parallel to a plane perpendicular to the optical axis of the collimated light from the collimator unit 13. Furthermore, a polarization beam splitter (hereinafter referred to as a "PBS") film and a reflective film are alternately provided at the interface between adjacent light-transmitting members arranged in the array, and a 1 / 2λ phase wave plate 143 is provided at the exit surface from which light incident on the polarization conversion element 14 and transmitted through the PBS film exits.

[0026] The above-mentioned free-form surface lens 15 is disposed on the exit surface side of this polarization conversion element 14. This free-form surface lens 15 has its exit surface, or its entrance surface, or both the exit and entrance surfaces, configured with free-form surfaces. With this free-form surface lens 15, as shown by the arrows in Fig. 5, in order to achieve distant illumination, the exit direction of light rays can be controlled by the lens surface shape, for example, by making the light distribution stronger in the center, thereby making it possible to obtain illumination light with a desired luminous intensity distribution.

[0027] In the headlight device 100 equipped with the visible light illumination unit 10, the detailed configuration of which has been described above, the light emitted from the LED 111 is converted into approximately parallel light by the action of the collimator unit 13. Thereafter, the light is converted into linearly polarized light by the polarization conversion element 14, and further, the polarization direction of the light is changed and adjusted (controlled) as appropriate by the polarization direction conversion device 20, which will be described in detail below, depending on the road surface condition and the like. Thereafter, a desired luminous intensity distribution is formed by the free-form surface lens 15, and the light is enlarged and projected by the projector lens 50, or by the projector lens 50 and the reflecting mirror 60, and is irradiated onto the space and road surface in front of the vehicle.

[0028] <Polarization direction conversion device> Polarization direction conversion device 20 uses a control signal, which will be described later, to realize the function of appropriately changing and adjusting (controlling) the illumination light from visible light illumination unit 10, including its polarization direction, to optimize it for the vehicle's driving scene, i.e., in accordance with the state of the optical road surface, etc. Specifically, in this embodiment, as shown in Fig. 7, it is configured with a TN (Twisted Nematic) LCD (Liquid Crystal Display), and controls the illumination light, including its polarization direction, that passes through the LCD surface position corresponding to the road surface onto which the illumination light from visible light illumination unit 10 is irradiated.

[0029] 7(a) and (b), the LCD panel constituting the polarization direction conversion device 20 is composed of a large number of pixels (e.g., 1920 vertical × 1080 horizontal) formed by sandwiching a liquid crystal composition 23 between a pair of glass substrates 22, 22 with alignment films formed on opposing surfaces, and light incident on one surface is transmitted through each cell and emitted from the other surface. At this time, by applying a voltage (control signal) between the alignment films arranged opposite each pixel, the properties of the liquid crystal composition constituting each cell through which the light passes can be changed, thereby making it possible to change and adjust, including the desired polarization.

[0030] FIG. 8(a) shows a configuration in which polarizers 31 and 32 are arranged in front of and behind the LCD panel 20, similar to the case of a typical TN-type LCD panel. As shown in the figure, the LCD panel 20 is positioned on the optical path of illumination light from a visible light illumination unit 10, which serves as a light source. In this example, to improve the contrast performance of the resulting image, a polarizer 31 (referred to as the "incident-side polarizer") is arranged at the position where the illumination light beam is incident, thereby improving the degree of polarization by transmitting p-polarized light. Similarly, a polarizer 32 (referred to as the "exit-side polarizer") that absorbs p-polarized light is arranged on the light-exit side of the LCD panel 20. As a result, the degree of polarization of the p-polarized light beam generated by the light source device is improved by the incident-side polarizer 31, and high contrast performance can be achieved by the polarization direction conversion function of the LCD panel. FIG. 8(b) shows a modified configuration in which the rear exit-side polarizer 32 is removed from the LCD panel 20 configured as described above.

[0031] The function (operation) of converting the polarization direction of incident light at each pixel in the polarization direction conversion device 20 made up of the above-mentioned TN LCD panel will be described below with reference to FIG.

[0032] According to the polarization direction conversion device 20 made up of the above-described TN LCD panel, as shown in Fig. 9(a), when no voltage is applied between the alignment films of each pixel, the polarization direction is rotated, for example, converting p-polarized light to s-polarized light (see the white arrow in the figure) and passing through the exit-side polarizer 32 (so-called white mode). On the other hand, as shown in Fig. 9(b), when a predetermined voltage (V) is applied, the polarization direction does not change. Therefore, light that remains p-polarized is blocked by the exit-side polarizer 32 (so-called black mode).

[0033] Therefore, in the polarization direction conversion device 20 according to the embodiment of the present invention, the transmittance (polarization degree) of p-polarized light in the exit-side polarizer 32 is increased, i.e., the p-polarized light blocking rate is set low (adjusted appropriately) so that p-polarized light can also be obtained at the exit side. As an example, when controlling the transmittance of the exit-side polarizer 32 to transmit or block light, the transmittance of p-polarized light is preferably set in the range of 0.01 to 0.1%. On the other hand, to achieve both polarization conversion and contrast (transmittance / absorbance), a transmittance of p-polarized light in the range of 1 to 40% is preferable. When the purpose is polarization conversion, the transmittance of p-polarized light is preferably 80% or higher. As shown in FIG. 8(b), the exit-side polarizer 32 may not be used. Alternatively, as shown in FIG. 8(b) above, a structure in which the exit-side polarizer 32 is not provided (removed) on the exit side of the LCD panel may be used.

[0034] According to the polarization direction conversion device 20 described above, the angle at which a specific incident polarized wave is rotated (twisted) changes depending on the voltage applied to the light distribution film of each pixel constituting the TN-type LCD panel, making it possible to appropriately select (control) the illumination light beam irradiated onto the road surface according to the road surface conditions. As a result, the transmittance of the exit-side polarizing plate 32 changes, and the intensity of the illumination light beam changes according to the applied voltage. In other words, it is possible to appropriately control the illumination light beam irradiated onto the road surface, including its polarization direction, according to its irradiation position (i.e., the position of the pixel constituting the LCD panel), thereby obtaining better illumination light that improves the driver's visibility.

[0035] Specifically, a TN-type LCD panel (normally white panel) used as a polarization direction converter rotates the polarization direction when no voltage is applied, converting p-polarized light to s-polarized light. However, when a certain voltage is applied, the polarization direction remains unchanged. Furthermore, because the angle at which a specific incident polarized light rotates (twists) changes depending on the applied voltage, the polarization direction of the illumination light beam can be controlled by appropriately setting the polarization degree (the ratio of the transmittance of a specific polarized light to the transmittance of the other polarized light) of the polarizer on the output side (or by not using a polarizer on the output side). For convenience of explanation, a TN-type LCD panel is described, but a TFT (Thin Film Transistor) LCD panel may also be used as a polarization direction converter.

[0036] Next, a technology will be described below for controlling the polarization direction and light distribution characteristics of the headlight using the headlight device 100 according to an embodiment of the present invention, which is equipped with the polarization direction conversion device 20 described above, in accordance with the steering angle, an external signal from the forward monitoring camera, and a control signal generated in response to ON / OFF of the control device.

[0037] A method for controlling the brightness, illumination range, and polarization degree of a headlight device of a moving vehicle will be described with reference to Fig. 10. Fig. 10(a) is a top view of a moving vehicle, and reference numeral 113 denotes a sensing camera for monitoring the front, which detects the presence or absence of a vehicle or obstacle ahead, and in this example, the vehicle headlight device automatically controls the illumination range and intensity of the illumination light of the vehicle headlight device.

[0038] In the example shown in Figure 10(b), the vehicle headlight device irradiates p-polarized light in the so-called low-beam range that illuminates an area close to the vehicle, particularly in rainy weather, to reduce reflections from puddles on the road surface. On the other hand, at the same time, s-polarized light can be irradiated in the distant range where vehicles ahead and obstacles traveling in the distance can be seen. In this way, the vehicle headlight device according to the embodiment of the present invention can selectively irradiate light of the optimal polarization in the required light illumination range, and as a result, a significant improvement in visibility can be expected.

[0039] Furthermore, the vehicle headlight device according to the embodiment of the present invention detects movement of the gaze point by monitoring the steering angle and the position of the driver's eyes with a camera, and automatically changes the illumination area from 116-1 to 116-2 accordingly. At this time, by modulating the luminous flux intensity (brightness) from the lighting device in accordance with the control signal, it is possible to optimize the luminous flux illumination intensity and illumination area even while the gaze point is moving. The area indicated by the dashed line in Figure 1(b) shows the illumination area when the vehicle headlight device is turned on without control.

[0040] For example, in bad weather, etc., in order to prevent the illumination light from the light source device from reflecting off the road surface or from raindrops / fog, it is recommended to configure the device to convert the light into p-polarized light, which is linearly polarized light that oscillates in a plane perpendicular to the road surface. On the other hand, in order to improve the visibility of objects in the distant field of view while driving, it is recommended to irradiate s-polarized light, which has a higher reflectivity than p-polarized light, as shown in Figure 11. In other words, a vehicle headlight device with excellent visibility can be realized by selectively using specific polarization depending on the object and distance, rather than using conventional headlights that irradiate natural light.

[0041] As described above, the vehicle headlight device described above employs LEDs, resulting in a vehicle headlight device that is low in power consumption and environmentally friendly, has a long lifespan, can be manufactured at low cost, is small, can be easily modularized, has high light utilization efficiency, and is capable of selectively irradiating light including light of the optimal polarization in the illumination range, thereby generating illumination light with excellent visibility, and is therefore highly functional. In other words, a vehicle headlight device is provided that can obtain light optimal for the vehicle's driving situation.

[0042] In addition to the above-described controls, in this embodiment of the present invention, the polarization direction, intensity, and illumination area of ​​the headlights are controlled in accordance with a control signal generated in response to the steering angle, external signals from a lane observation camera, and the ON / OFF state of the control device. As a result, the headlights change between the conventional high beam and low beam. For example, when the headlights illuminate a puddle on the road surface during rainy weather, they use p-polarized light, which has less reflection, and s-polarized light, which makes distant objects easier to see. At this time, the illumination area can be optimized by modulating the intensity of the illumination light as well.

[0043] The headlight device according to the embodiment of the present invention has been described in detail above, focusing on its main constituent elements. Below, other embodiments including modifications thereof will be described in detail.

[0044] Example 2 12(a) and 12(b) show a configuration in which a polarizing mirror or polarizing plate 30 is further provided at an angle on the output side of the liquid crystal panel (LCD panel) that constitutes the polarization direction conversion device 20 in the vehicle headlight device 100, the basic configuration of which has been described above. With this configuration, by controlling the on / off of the LCD panel that constitutes the polarization direction conversion device 20 to finely control the light distribution, it is possible to provide illumination that ensures long-distance visibility while suppressing dazzle to vehicles traveling in the oncoming lane or the same lane. Furthermore, by using a color liquid crystal display element (specifically, a color filter is provided on one side of the LCD panel glass substrate in FIG. 7, although not shown here) for the LCD panel that constitutes the polarization direction conversion device 20, it is possible to display information indicating the driving status of the vehicle, including its speed and direction, and various other information related to vehicle driving, on the road using illumination light, not only at night but also during the day.

[0045] In these figures, the LCD panel 20 is shown arranged on the optical path of illumination light from the visible light illumination unit 10, which is a light source device, more specifically, between the free-form surface lens 15 of the visible light illumination unit 10 and the projector lens 50. Also, reference numeral 21 in the figures denotes an FPC (Flexible Printed Circuits) electrically connected to the LCD panel 20, and the LCD panel 20 is controlled by a control signal input from a control circuit (not shown here) via the FPC 21.

[0046] Incidentally, when an LCD panel 20 is provided in a vehicle headlight device 100, it is conceivable that the panel may be burned or its characteristics may be deteriorated due to irradiation with sunlight incident from outside. For this reason, in this embodiment, as a preventative measure, a polarizing mirror 30 is further disposed between the LCD panel 20 and the projector lens 50. Note that the same effect can be obtained by disposing a reflective polarizing plate in place of the polarizing mirror 30 in the above-mentioned position.

[0047] Next, when projecting information onto the road surface, the distance of the image projected onto the road surface through the projector lens 50 varies for each pixel of the LCD panel 20, resulting in a decrease in focus performance. Therefore, in order to reduce the amount of defocus that occurs in the image projected onto the road surface, it is preferable to arrange the LCD panel at an angle with respect to the optical axis. Therefore, in this embodiment, as shown in Fig. 12, the LCD panel 20 is arranged with its emission surface tilted upward by an angle θp (e.g., 10 to 15 degrees) with respect to the optical axis. Furthermore, although the LCD panel 20 shown in Fig. 12 is tilted with respect to the optical axis, when the LCD panel is used as a normal headlamp without displaying information on the road surface, the LCD panel does not need to be tilted with respect to the optical axis.

[0048] Furthermore, at this time, the polarization direction of the light emitted from the LED 111 is rotated by 90 degrees when it passes through the LCD panel 20. For this reason, it is desirable that the above-mentioned polarization conversion element 14 be configured so as to convert the light from the visible light illumination unit 10 into linearly polarized light (p-polarized light: polarized light parallel to the paper surface) that oscillates in a plane horizontal to the road surface, as shown in FIG. 13(a). In this embodiment, the polarization conversion element 14 is configured by combining a columnar light-transmitting member 141 having a parallelogram cross section (hereinafter referred to as a parallelogram column) and a columnar light-transmitting member 142 having a triangular cross section (hereinafter referred to as a triangular column), as shown in FIG. 13(b), and is configured by arranging a plurality of such members in an array parallel to a plane perpendicular to the optical axis of the collimated light from the collimator unit 13. Furthermore, PBS films and reflective films are alternately provided at the interfaces between adjacent light-transmitting members arranged in an array, and a 1 / 2λ phase wave plate 143 is provided at the exit surface from which light that enters the polarization conversion element 14 and is reflected by the PBS film exits, making it possible to irradiate p-polarized light.

[0049] On the other hand, the polarizing mirror 30 (see FIG. 12 ) is mounted with its exit surface tilted downward at an angle θo of 45 degrees or more, preferably 60 degrees, relative to the optical axis. In this embodiment, as shown in FIG. 12 , the angle θo is set to 60 degrees (θo = 60°). By setting the tilt angle θo of the polarizing mirror 30 to 45 degrees or more, the reflectance of externally incident s-polarized light can be increased while maintaining a high transmittance of p-polarized light. Furthermore, by tilting the exit surface of the polarizing mirror 30 downward rather than upward relative to the optical axis, as shown in the figure, it is possible to set a larger angle θs of the polarizing mirror's normal plane relative to sunlight incident from above relative to the horizontal (optical axis) direction. FIG. 14 shows the transmittance characteristics of the polarizing film designed for the polarizing mirror 30. It can be seen that the polarizing mirror selectively reduces the transmittance of s-polarized light, and that this effect increases as the incident angle increases. Therefore, the polarizing mirror 30 reduces the transmittance of the s-polarized component of sunlight, weakening the intensity of sunlight reaching the LCD panel 20, thereby preventing / suppressing burning and deterioration of the characteristics of the LCD panel 20 due to sunlight.

[0050] As shown in Figure 15, sunlight has sufficient spectral irradiance in wavelengths outside the visible light range of 380 nm to 780 nm, particularly in the near-infrared and infrared ranges of wavelengths above 780 nm. Therefore, by designing polarizing mirror 30 to have low transmittance for infrared light, the infrared components contained in sunlight can be reduced, further preventing burning and performance degradation caused by sunlight. Furthermore, since the thickness t of polarizing mirror 30, which is positioned at an angle, can cause coma and astigmatism, the thickness t is preferably 1.5 mm or less, and 0.6 mm or more from the viewpoint of strength.

[0051] In addition, when the LCD panel 20 is provided as described above, the free-form surface of the free-form surface lens 15 provided on the exit surface side of the polarization conversion element 14 in the visible light illumination unit 10 is set so as to condense the light so that the distribution of light incident on the LCD panel 20 is stronger at the center, thereby making it possible to achieve the illumination light irradiation over a long distance required for a headlight device.

[0052] According to the headlight device described above in detail, light emitted from LED 111 is converted into approximately parallel light by collimator unit 13 and then converted into s-polarized light parallel to the plane of the paper by polarization conversion element 14. This emitted light is then focused by free-form surface lens 15 so that the light intensity at the center is increased and irradiated onto LCD panel 20, where it is optically modulated into image light of various information, transmitted through LCD panel 20, and emitted to polarizing mirror 30. In this process, the s-polarized light converted by polarization conversion element 14 is converted into p-polarized light by LCD panel 20, so that the light is efficiently transmitted through polarizing mirror 30; specifically, 80% or more of the light is transmitted through polarizing mirror 30. The light transmitted through polarizing mirror 30 is further magnified and projected by projector lens 50 and irradiated onto the road surface and / or ahead.

[0053] 12, in addition to the LCD panel 20, an infrared lighting unit 40 that emits infrared light can also be provided. Note that this infrared lighting unit 40 emits infrared light for an infrared sensor (not shown) that detects the situation outside the vehicle at night, for example. In the illustrated example, the headlight device uses the polarizing mirror 30 to superimpose the infrared light from the infrared lighting unit 40 on the illumination light from the visible light lighting unit 10, and irradiates the superimposed infrared light onto the road surface in front of the vehicle as illumination light.

[0054] 16, the infrared illumination unit 40 is configured by attaching one or more semiconductor infrared LEDs (Light Emitting Diodes) 41, which are solid-state light sources, to an infrared LED collimator unit 42, similar to the above-described visible light illumination unit. In the illustrated example, as an example, a plurality of (seven) infrared LEDs 41 are arranged in a row, and each is fixed so as to be positioned at the center of a recess (see reference numeral 134 in FIG. 6) of an infrared LED collimator 421 that constitutes the infrared LED collimator unit 42. Although not shown here, it will be obvious to those skilled in the art that the infrared LED 41, like the above-described LED 111, is also arranged on a substrate on which a control circuit and the like are mounted, and that a heat sink for dissipating heat generated by the LED into the surrounding air is attached to the back surface of the substrate.

[0055] 12, the infrared lighting unit 40 is disposed using the polarizing mirror 30 described above, that is, as an example, it is disposed below the optical axis of the polarizing mirror 30, which is attached with its emission surface tilted at a desired angle relative to the optical axis. In this way, the infrared light emitted from the infrared LED 41 is reflected by the surface of the polarizing mirror 30, and is superimposed on the illumination light from the visible light lighting unit 10, and is then irradiated onto the road surface in front of the vehicle. In this case, it is desirable to set the installation angle so that the component of sunlight reflected by the polarizing mirror 30 does not enter the infrared lighting unit 40.

[0056] Thus, according to the second embodiment described above in detail, by incorporating an infrared lighting unit capable of irradiating infrared light together with an LCD panel that enables light distribution control while preventing deterioration due to sunlight, a headlight device with even better functionality can be manufactured at low cost, similar to the first embodiment described above, and the effect of facilitating miniaturization and modularization can be achieved.

[0057] Example 3 17 shows an example of a configuration in which a shade 60 is provided inside the headlight device in addition to the configuration of the above-mentioned first or second embodiment. Note that this shade 60 makes it possible to form a headlight cut-off line (light distribution) required for beams (so-called low beams) in which light rays from automotive lamps pass each other when vehicles pass each other. As shown in the figure, this shade 60 is made of a light-blocking member formed into a predetermined shape, and is positioned and fixed near the focal point of the projector lens 50.

[0058] Such a shade 60 makes it possible to form an illumination light irradiation pattern, such as a cut line required for low beams (so-called low beams), by blocking a portion of the illumination light from the above-mentioned visible light illumination unit 10. In addition to the fixed type as shown in the figure, this shade 60 can also be made movable by providing a rotation mechanism such as an electric motor (not shown here), so that it can also be used in conjunction with high beams (so-called high beams).

[0059] As described above, according to the third embodiment, it is possible to manufacture a headlight device with even better functionality at low cost, and it is possible to reduce the size of the headlight device and facilitate modularization.

[0060] Example 4 Furthermore, FIG. 18 shows a configuration example in which the visible light illumination unit 10, which is a light source device, is small relative to the LCD panel 20, as a modification of the configuration of the above embodiment. When the visible light illumination unit 10 is small compared to the LCD panel 20, it is necessary to use the free-form surface lens 15 to narrow the substantially parallel light emitted from the polarization conversion element 14 to match the size of the LCD panel 20. In Fig. 18, the free-form surface lens 15 achieves narrowing by making the entrance surface and exit surface each convex and by increasing the distance between the polarization conversion element and the LCD panel 20. Furthermore, in order to emit the light from the small LCD panel 20 at a wide light distribution angle via the projector lens 50, the focal length of the projector lens 50 is shortened and the distance between the LCD panel 20 and the projector lens 50 is also shortened.

[0061] As described above, according to Example 4, by using a smaller LED panel, a headlight device with excellent functionality can be manufactured at low cost, and the headlight device can be made smaller and more easily modularized. Furthermore, according to the vehicle headlight device of the present invention described above in detail, it is possible to realize a vehicle headlight device with high light utilization efficiency, low power consumption, excellent environmental protection, and a long life.

[0062] The above describes vehicles equipped with headlight devices according to various embodiments of the present invention. However, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments describe the entire system in detail to clearly explain the present invention, and the present invention is not necessarily limited to a system including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations. [Explanation of symbols]

[0063] 100...headlight device, 10...visible light illumination unit, 11...LED substrate, 111...LED, 12...heat sink, 13...collimator unit, 131...collimator, 132...outer peripheral surface, 133...convex portion (convex lens surface), 134...concave portion, 135...convex lens surface, 14...polarization conversion element, 143...1 / 2λ phase wave plate, 15...free-form surface lens, 20...polarization direction conversion device (TN type LCD panel (liquid crystal panel)) , 30...polarizing mirror, 40...infrared lighting unit, 41...infrared LED, 42...infrared LED collimator unit, 50...projector lens, 60...reflecting mirror, 110...automobile, 113...forward monitoring camera, 115...headlight device's illumination area near the vehicle, 116-1...headlight device's illumination area far from the vehicle (before control), 116-2...headlight device's illumination area far from the vehicle (after control), 117...forward vehicle.

Claims

1. A headlight device for a vehicle, a light source device that generates light; an optical means disposed on the optical axis of the light source device, for projecting light from the light source device so as to form a desired light distribution; a polarization direction conversion device that changes the polarization direction of light from the light source device, the light source device, the polarization direction conversion device, and the optical means are arranged in this order on the optical axis of the light emitted from the light source device, the polarization direction conversion device is composed of a liquid crystal panel, the light source device includes a first polarizing plate; a second polarizing plate provided on the incident surface side of the liquid crystal panel constituting the polarization direction conversion device; A headlight device, wherein light that has passed through the first polarizing plate of the light source device is incident on the second polarizing plate located on the incident surface side of the liquid crystal panel.

2. The headlight device according to claim 1, A headlight device, wherein the transmission axis of the first polarizing plate of the light source device is different from the transmission axis of the second polarizing plate located on the incident surface side of the liquid crystal panel.

3. 3. The headlight device according to claim 2, a transmission axis of the first polarizer of the light source device and a transmission axis of the second polarizer on the incident surface side of the liquid crystal panel are perpendicular to each other.

4. The headlight device according to claim 1, A headlight device, wherein the liquid crystal panel constituting the polarization direction conversion device has a structure in which a third polarizing plate on the exit side is not disposed.

5. The headlight device according to claim 1, A headlight device, wherein a third polarizer on the exit side of the liquid crystal panel that constitutes the polarization direction conversion device has a light blocking rate that is smaller than the light blocking rate of polarized light of the second polarizer on the incident side.

6. The headlight device according to claim 1, The headlight device, wherein the optical means is composed of either a projector lens or a reflecting mirror, or both.

7. The headlight device according to claim 1, A headlight device further comprising a free-form surface lens provided on the light output surface side of the light source device.

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