JP2013024921A - Head-up display - Google Patents

Head-up display Download PDF

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JP2013024921A
JP2013024921A JP2011156781A JP2011156781A JP2013024921A JP 2013024921 A JP2013024921 A JP 2013024921A JP 2011156781 A JP2011156781 A JP 2011156781A JP 2011156781 A JP2011156781 A JP 2011156781A JP 2013024921 A JP2013024921 A JP 2013024921A
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liquid crystal
image
light
prism
crystal cell
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JP2011156781A
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Japanese (ja)
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Yasuo Toko
康夫 都甲
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Stanley Electric Co Ltd
スタンレー電気株式会社
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Abstract

PROBLEM TO BE SOLVED: To provide a head-up display in which by changing an applied voltage, a refraction angle of transmitted light can be controlled and a focal length can be changed.SOLUTION: A head-up display includes: an image display device that outputs an image of linear polarization; an optical system that has an optical deflection cell and a lens disposed in a latter part of the optical deflection cell and having a plurality of focal points, and projects the image outputted from the image display device; and a control unit. Based on information from the outside, the control unit changes a voltage applied to the optical deflection cell to change a refraction index of a liquid crystal layer and controls a refraction angle of transmitted light of the image to control a projection position and size of the image.

Description

  The present invention relates to a head-up display.

  Conventionally, a so-called head-up display (HUD) is known as an information display device in a vehicle such as an automobile. The head-up display reflects the display image from the projector provided at the lower part of the windshield toward the driver by a combiner (translucent reflecting member) provided on the windshield, so that the driver can wind the windshield. The front view and the display image, which is a virtual image, are overlapped so as to be visible.

  The height of the driver's viewpoint differs depending on the driver's physique, vehicle seat shape, etc., so the head-up display can be adjusted so that the driver can view the displayed image even if the position of the driver's viewpoint changes. It is requested to do so.

  For example, in Patent Document 1 and Patent Document 2, a reflector that reflects the image light from the display device is provided in front of the combiner, and the tilt of the reflector is obtained so that a clear virtual image can be obtained according to the viewpoint of the driver. A technique for adjusting the position by a mechanical operation unit such as a motor is disclosed.

JP 05-229366 A JP 2003-39982 A

  In the case of responding to the change of the viewpoint position by the mechanical operating unit as in the conventional case, there is an influence on the size and weight of the apparatus. In particular, since the space where the head-up display is mounted is often limited, the size of the apparatus becomes a problem in terms of mounting on a vehicle.

  In addition, the mechanical operating unit may have a problem in long-term reliability, noise may be generated, and an expensive stepping motor or microcomputer may be required.

  Furthermore, when a strong light beam such as sunlight enters the display device as backlight from the combiner side via a reflector, etc., it becomes difficult to see the virtual image, so the brightness of the light source for the backlight is increased to make the virtual image brighter, etc. Countermeasures are necessary.

  An object of the present invention is to provide a head-up display capable of controlling the refraction angle of transmitted light by changing the applied voltage and changing the focal length.

  According to an aspect of the present invention, the image display device includes: an image display device that outputs a linearly polarized image; a light deflection liquid crystal cell; and a lens that is disposed at a subsequent stage of the light deflection liquid crystal cell and has a plurality of focal points. A head-up display having an optical system for projecting an image output from the apparatus and a control unit, wherein the light deflection liquid crystal cell includes a pair of first and second transparent substrates facing each other, and the first A pair of first and second transparent electrodes formed on the second transparent substrate and applying a voltage between the first and second transparent substrates, and one of the first and second transparent substrates. A prism layer having a prism formed thereon; an alignment film formed on the prism layer and subjected to an alignment process in parallel with a polarization direction of an output of the image display device; and the first and second transparent layers Liquid with liquid crystal molecules sandwiched between substrates The control unit changes the refractive index of the liquid crystal layer by changing the voltage applied to the first and second transparent electrodes according to information from the outside, thereby changing the slope of the prism. And a head-up display that controls the refraction angle of the light of the image passing through the interface between the liquid crystal layer and the projection position and size of the image.

  ADVANTAGE OF THE INVENTION According to this invention, the head-up display which can change the focal distance while controlling the refraction angle of the light to permeate | transmit by changing the applied voltage can be provided.

1 is a schematic cross-sectional view of a light deflection liquid crystal cell 100 according to an embodiment of the present invention. 2 is a schematic perspective view of a prism layer 3. FIG. 2 is a schematic plan view of a prism layer 3 on a glass substrate 1. FIG. 1 is a conceptual diagram illustrating a configuration of a head-up display in which a light deflection liquid crystal cell 100 according to an embodiment of the present invention is incorporated in an optical system 20. FIG. FIG. 5 is a conceptual diagram for explaining an example of adjusting the position and size of a virtual image seen from a driver with the viewpoint position fixed in the head-up display shown in FIG. 4. It is a conceptual diagram which shows the example which displays the arrow (virtual image) 27 on the windshield 25 according to a real environment (scenery) using the head-up display of a present Example. It is a conceptual diagram which shows the structural example of the optical system 20 of the head-up display which can prevent incidence | injection to the liquid crystal display device of external light.

  FIG. 1 is a cross-sectional view in the thickness direction schematically showing a light deflection liquid crystal cell (liquid crystal optical element) 100 according to an embodiment of the present invention. The light deflection liquid crystal cell 100 is an optical path conversion element capable of converting (changing) an optical path of light transmitted through the cell by changing an applied voltage.

  A pair of glass substrates on which a transparent electrode was formed (a glass substrate 1 on which a transparent electrode 2 was formed and a glass substrate 11 on which a transparent electrode 12 was formed) were prepared. The glass substrates 1 and 11 each have a thickness of 0.7 mm and are made of alkali-free glass. Each of the transparent electrodes 2 and 12 has a thickness of 150 nm and is made of indium tin oxide (ITO) and is patterned into a desired planar shape.

  A prism layer 3 was formed on the transparent electrode 2 of the glass substrate 1 on one side. The prism layer 3 has a shape in which the prisms 3a are arranged on the base layer 3b. The base layer 3b has a thickness of about 2 μm to 30 μm, for example. In this embodiment, the prism layer 3 is formed using a material (hereinafter, simply referred to as a heat-resistant prism material) having a small change in characteristics (transmittance) with respect to heat treatment at 180 ° C. or higher, such as UV curable acrylic resin. Polyimide, which has been very difficult in the past, by using a material that has little change in characteristics (transmittance) to heat treatment at 180 ° C. or higher, such as UV curable acrylic resin, etc. (can be heat treatment at 180 ° C. or higher). An alignment film for LCD made of, etc. can be formed on the prism. In this specification, “less change in characteristics (transmittance)” indicates a state where the change in characteristics (transmittance) is approximately within 2% of that before the heat treatment. The UV curable acrylic resin has not only heat resistance but also excellent adhesion to glass and has a property of being difficult to adhere to metal (good releasability). Suitable as material for forming prisms according to examples. Epoxy resins are also excellent in heat resistance, and are considered to be usable as materials for forming prisms according to embodiments of the present invention. Polyimide can also be used.

  FIG. 2 is a schematic perspective view of the prism layer 3, and an enlarged view of the cross-sectional shape of the prism 3a is shown on the right side. Each prism 3a has, for example, a triangular prism shape with an apex angle of about 45 ° and a base angle of about 45 ° and about 90 °, and a plurality of prisms 3a are orthogonal to the prism length direction (this direction is defined as the prism width). The direction is lined up in the same direction. The height of the prism 3a is about 20 μm, and the length of the bottom of the prism 3a (prism pitch) is about 20 μm.

  FIG. 3 is a schematic plan view of the prism layer 3 on the glass substrate 1. A method for producing the prism layer 3 will be described. A prism layer 3 mold is formed, and a predetermined amount of heat-resistant prism material 3R (for example, an ultraviolet (UV) curable mold) is formed on the transparent electrode 2 of the glass substrate 1 (vertical 150 mm × width 150 mm × thickness 0.7 mmt). Acrylic resin) was dropped, and a prism mold with a release agent or coating agent was placed at a predetermined position above it, and a thick quartz member was placed on the back side of the substrate for reinforcement. . The size of the mold (the size of the prism formation region) is 80 mm long × 80 mm wide.

After pressing and leaving for 1 minute or longer to sufficiently spread the heat-resistant prism material 3R, ultraviolet rays were irradiated from the back side of the glass substrate 1 to cure the heat-resistant prism material 3R. The irradiation amount of ultraviolet rays was 200 mJ / cm 2 . What is necessary is just to set suitably the irradiation amount of an ultraviolet-ray so that resin may harden | cure. In addition, since ITO absorbs ultraviolet rays, if the film thickness of the transparent electrode is changed, it is necessary to change the ultraviolet irradiation amount.

  After the heat-resistant prism material 3R is cured, quartz, a pressing jig, and the like are removed, and the glass substrate 1 on which the prism layer 3 is formed is pressed down to peel from the prism mold.

  In addition, the magnitude | size of the prism layer 3 is performed by adjusting the dripping amount of the heat resistant prism material 3R. The drop amount was adjusted to form the prism layer 3 in the necessary area A2 (length 60 mm x width 60 mm) of the entire prism formation area A1 (length 80 mm x width 80 mm). The refractive index of the UV curable acrylic resin constituting the prism layer 3 is 1.51.

  The prism layer 3 has a function of changing the traveling direction of light incident from one side and emitted from the other side depending on the angle of the apex angle.

  Returning to FIG. 1, the description will be continued. The glass substrate 1 with prism and the other glass substrate 11 with ITO were washed with a washing machine. The cleaning method was performed in the order of brush cleaning using an alkaline detergent, pure water cleaning, air blow, ultraviolet irradiation, and infrared drying. The cleaning method is not limited to this, and high pressure spray cleaning, plasma cleaning, or the like may be performed.

  Next, an alignment film 13 was formed of polyimide or the like on the prism layer 3 and the transparent electrode 12 of the other glass substrate 11. By forming the alignment film 13 on the prism layer 3, the alignment regulating force can be made sufficient. Here, Nissan Chemical Industries SE-130 was formed by flexographic printing to a thickness of 80 nm and baked at 180 ° C. for 1.5 hours. After firing, the alignment film 13 was subjected to an alignment treatment. The alignment direction of the alignment film 13 is such that when the two glass substrates are overlapped to form a cell, the alignment film 13 on the prism layer 3 and the rubbing direction of the alignment film 13 on the transparent electrode 12 of the other glass substrate 11 are different. It was determined to be anti-parallel. The material of the alignment film is not limited to the above, and many commercially available polyimide alignment film materials can be used.

Next, the alignment film 13 on the prism layer 3 was optically aligned as an alignment process. Here, a method of irradiating the glass substrate 11 with light polarized with ultraviolet rays from the normal direction was used. That is, irradiation was performed from a direction inclined by 45 ° with respect to the inclined surface of the prism layer 3. The wavelength of the polarizing filter used for exposure was 310 nm, and exposure was performed for 120 seconds at an illuminance of 8.5 mW / cm 2 (irradiation amount: about 1 J / cm 2 ). The light orientation direction was such that the polarization direction of the polarizing filter used for exposure and the prism direction (x direction in FIG. 2) were parallel. The alignment direction of the liquid crystal molecules is arranged so as to be orthogonal to the polarization direction of the ultraviolet light. As a result, liquid crystal molecules were aligned in a direction perpendicular to the prism direction (y direction in FIG. 2). Note that a rubbing process may be performed as an alignment process on the alignment film 13 on the prism layer 3. When the rubbing process is performed, for example, the pressing amount is 0.8 mm in the y direction in FIG.

  By using photo-alignment as the alignment method, uniform liquid crystal alignment can be obtained even on the uneven prism layer 3. As a result, the image quality of the projected image is significantly improved compared to the rubbing process.

  On the other alignment film 13 of the glass substrate 11 with ITO, a rubbing process was performed as an alignment process. In order to achieve strong anchoring, a rubbing treatment was performed by pushing the material strongly with a push amount of 0.8 mm. The rubbing was performed in the direction of the arrow 18 in FIG. 1 (the direction opposite to the x direction in FIG. 2) so as to be anti-parallel to the tilt direction of the prism layer 3. Note that photo-alignment may be performed on the alignment film 13 of the glass substrate 11.

  Next, a main sealant 16 containing 2 wt% to 5 wt% of a gap control agent was formed on the glass substrate 1 on the side where the prism layer 3 was formed. As a forming method, screen printing or a dispenser is used. The gap control agent was selected so that the thickness of the liquid crystal layer 15 including the base layer (2 μm to 30 μm) of the prism layer 3 and the height of the prism (0 μm to 20 μm) was, for example, 10 μm to 35 μm. Since the prism layer 3 changes in height depending on the position, the thickness of the liquid crystal layer 15 also changes accordingly.

  Here, a plastic ball made by Sekisui Chemical having a diameter of 45 μm was selected as the gap control agent, and 4 wt% was added to the sealing agent ES-7500 made by Mitsui Chemicals to make the main sealing agent 16.

  On the glass substrate 11 on the side where the prism is not formed, plastic balls made of Sekisui Chemical having a diameter of 21 μm as a gap control agent 14 were dispersed using a dry gap spreader.

  Next, both the glass substrates 1 and 11 were overlapped, and the main sealant was cured by heat treatment in a state where pressure was constantly applied by a press machine or the like. Here, heat treatment was performed at 150 ° C. for 3 hours.

  A liquid crystal layer 15 was formed by vacuum-injecting liquid crystal into the empty cell thus prepared. In the examples, a liquid crystal manufactured by Merck with a positive Δε, Δn = 0.212, ne = 1.716, and no = 1.504 was used. Note that the larger the Δn of the liquid crystal is, the more the image can be bent. However, since the liquid crystal with a large Δn may not have a good orientation, the present embodiment has a relatively large Δn and an excellent orientation. Materials were used.

  After injection of the liquid crystal, pressing was performed to discharge excess liquid crystal, and then an end sealant was applied to the injection port and sealed. After sealing, heat treatment was performed at 120 ° C. for 1 hour to adjust the alignment state of the liquid crystal. In this way, the light deflection liquid crystal cell 100 was produced.

  When the alignment treatment of the alignment film 13 is performed by photo-alignment, it is necessary to perform from liquid crystal injection to heat treatment as quickly as possible. This is because the alignment regulating force of the optical alignment of the alignment film 13 on the prism layer 3 is not so strong, and a phenomenon of alignment (fluid alignment) in the direction affected by the flow of liquid crystal during liquid crystal injection is observed. In order to solve this problem, high-temperature treatment is performed, and the liquid crystal is once brought to an isotropic phase temperature or higher so that the flow alignment can be eliminated and the liquid crystal can be re-oriented in the direction caused by the original photo-alignment. However, in this method, the flow alignment becomes stable after a long time since the liquid crystal is injected, and it cannot be completely erased by some heat treatment (this is called alignment memory property). Therefore, it is desirable to perform from the liquid crystal injection to the heat treatment as quickly as possible, and it is desirable to perform the heat treatment within 3 hours if possible and within 24 hours at the latest.

  In the light deflecting liquid crystal cell 100 of the example, the major axis of the liquid crystal molecules is orthogonal to the prism length direction when no voltage is applied, and the major axis of the liquid crystal molecules rises in the substrate normal direction when the voltage is applied. The liquid crystal used in the examples shows a refractive index of 1.716 with respect to a polarization component whose electric vector oscillation direction is parallel to the major axis direction of the liquid crystal molecule, and the electric vector oscillation direction is in the major axis direction of the liquid crystal molecule. A refractive index of 1.504 is shown for the vertical polarization component.

  The refractive index of the UV curable acrylic resin constituting the prism layer 3 is 1.51, and the vibration direction of the electric vector is equivalent to the refractive index of the liquid crystal with respect to the polarization component perpendicular to the major axis direction of the liquid crystal molecules. . Note that the difference between the refractive index of the first material and the refractive index of the second material is within 3% (more preferably within 2%) of the refractive index of the first material or the refractive index of the second material. ), It is assumed that the refractive indexes of both materials are equal.

  Therefore, in the light deflecting liquid crystal cell 100 according to the embodiment, the liquid crystal layer refractive index (1.504) and the prism layer 3 refractive index (1.51) are applied when a voltage is applied in which the long axis of the liquid crystal molecules rises in the normal direction of the substrate. Therefore, the action of the prism disappears and the incident light travels straight as it is. On the other hand, when no voltage is applied (including when a low voltage is applied), the refractive index of the liquid crystal layer and the refractive index of the prism layer 3 are different, so that the action of the prism occurs and the incident light is refracted.

  Note that a minute groove for air bleeding may be formed on the prism forming die. Further, the mold and the substrate may be superposed in a vacuum. Note that the liquid crystal injection method is not limited to vacuum injection, and, for example, a One Drop Fill (ODF) method may be used.

  In the light deflection liquid crystal cell 100 of the embodiment, a rectangular electrode pattern that is wider than the prism pattern and intersects at 90 ° between the upper and lower substrates is used, terminals are taken from both substrates, and the main seal portion The electrodes were not crossed. The short circuit is suppressed by not crossing the electrodes of the upper and lower substrates at the main seal portion. If a terminal is to be taken from one side, a structure in which a gold ball for vertical conduction is added to the main seal may be adopted.

  The liquid crystal cell 100 produced as described above was incorporated into a projector optical system, and the state of image change was observed. The liquid crystal display device arranged in advance on the liquid crystal projector was arranged in such a manner that the polarizing direction of the polarizing plate and the liquid crystal cell 100 were aligned in parallel with each other. By connecting a pin terminal or the like to the transparent electrode of the liquid crystal cell 100, electrical connection is established, and an AC voltage can be applied to the liquid crystal cell 100. The liquid crystal cell 100 was disposed outside the projector lens. In addition, a multifocal lens was disposed outside the liquid crystal cell 100. The multifocal lens used here is the same as the multifocal lens 31 of the optical system 20 shown in FIG. 4 to be described later, and is a convex lens having a different focal length depending on the location (a type in which the focal length becomes shorter as the lens thickness becomes thinner). ) Is cut in half.

  When a voltage was applied to the liquid crystal cell 100, it was observed that the position of the image projected by the projector moved up and down by the voltage. In addition, the image size and focal length were also changed by the multifocal lens. At this time, it was possible to change only the position, focal length, and size of the image with almost no deterioration in image quality.

  Note that the liquid crystal molecules have an elongated molecular shape, and polarized light in a certain direction (long axis direction of the liquid crystal molecules) can be bent, but polarized light in a certain direction is transmitted as it is. Therefore, the polarization direction in which the light emitted from the light source is emitted via the head-up display or the liquid crystal display device for the projector is parallel to the direction of the alignment treatment performed on the liquid crystal display device side of the liquid crystal cell 100. Otherwise, all the light cannot be bent.

  FIG. 4 is a conceptual diagram showing a configuration of a head-up display in which the light deflection liquid crystal cell 100 according to the embodiment of the present invention is incorporated in the optical system 20.

  The optical system 20 of the head-up display is mounted below the windshield 25 of the vehicle 30. Light from the light source 21 such as an LED is incident on the liquid crystal display device 22 in a state in which the light distribution is controlled so as to be parallel light to some extent. The image by the light 26 displayed on the liquid crystal display device 22 is transmitted through the light deflecting liquid crystal cell 100 arranged in parallel with the display surface of the liquid crystal display device 22 and reflected upward by the reflecting plate (mirror) 24. The image is projected onto the windshield 25 also serving as a combiner. The liquid crystal display device 22 uses a polarizing plate, and the image light 26 emitted from the liquid crystal display device 22 is in a linearly polarized state. The direction of the light deflection liquid crystal cell 100 is aligned so that the axis of polarization is parallel to the liquid crystal molecule alignment direction in the projection plane when the light deflection liquid crystal cell 100 is off. In addition, a multifocal lens 31 having a plurality of focal points is disposed in the optical axis of the rear stage of the light deflection liquid crystal cell 100 (between the reflector 24 and the windshield 25 in this embodiment). The control unit 28 controls the voltage applied to the light deflection liquid crystal cell 100 to adjust the angle at which the light deflection liquid crystal cell 100 bends the image light 26, and the position of the image light 26 incident on the multifocal lens 31. And the angle can be adjusted.

  The multifocal lens 31 has a plurality of focal points, for example, a first region and a second region, each having a different focal length, and preferably a focal point intermediate between the first region and the second region. A third region (one or a plurality of regions) having a distance is included. In the first to third regions, the focal length may change stepwise or may change continuously.

  In this embodiment, a multifocal lens 31 having a shape in which a convex lens whose focal length continuously changes depending on a region (a type in which the focal length decreases as the lens thickness decreases) is cut in half. When light is bent at the maximum angle without applying a voltage to the light deflection liquid crystal cell 100, the region through which the light passes is defined as a first region R1 having the shortest focal length, and the voltage is applied to the light deflection liquid crystal cell 100. When light is not bent (approached straight) when applied, the region through which the light passes is defined as the second region R2 having the longest focal length, and an intermediate voltage is applied to the light deflection liquid crystal cell 100 so that the light is transmitted. The region through which the light passes when bent to some extent is defined as a third region R3 having a focal length intermediate between the first region and the second region.

  In the above example, the case where one lens has a plurality of focal lengths has been described. However, the multifocal lens 31 may be configured by combining a plurality of single focal lenses. In this case, for example, a single focus lens may be disposed corresponding to each of the first to third regions R1 to R3.

  In addition, the multifocal lens 31 is not limited to the above example, and for example, a variable focus lens, a liquid crystal lens whose focal length can be changed by voltage, or the like can be used. When the lens capable of controlling the focal length is used as the multifocal lens 31, the control unit 28 controls the focal length of the multifocal lens 31 in accordance with the angle at which the light deflection liquid crystal cell 100 bends the light 26 of the image. To do. For example, in the optical system 20 shown in FIG. 4, control is performed so that the focal length of the multifocal lens 31 becomes shorter as the angle at which the light deflection liquid crystal cell 100 bends the light 26 of the image (the angle at which the light bends downward) increases. To do.

  Note that, as described above, the focal length of each of the first to third regions R1 to R3 is such that the focal length of the region R1 is the shortest, the focal length of the region R2 is the longest, and the focal length of the region R3 is the longest. Depending on the desired visual effect (relationship with the angle at which the light is deflected by the light deflection liquid crystal cell 100), for example, the region R1 and the region R2 are equivalent focal lengths, and the region R3 The focal length may be shorter or longer, or the region R2 may have the shortest focal length and the region R1 may have the longest focal length.

  FIG. 5 is a conceptual diagram for explaining an example of adjusting the position and size of a virtual image that can be seen from a driver in the head-up display shown in FIG. 4 while fixing the viewpoint position.

  In this example, the prism layer 3 is oriented so that the light incident from the liquid crystal display device 22 bends downward. At this time, the alignment direction of the liquid crystal molecules in the liquid crystal layer 15 of the light deflection liquid crystal cell 100 is orthogonal to the prism direction. With the material and prism angle used in this embodiment, the light is bent by a maximum of about 12 ° by the light deflection liquid crystal cell 100. Although the optical path length that can be taken by the head-up display is limited by the installation space on the vehicle 30, for example, in this embodiment, the optical path length is 50 cm, so the image by the light 26 projected on the windshield 25 Can move the position up and down about 10 cm. Note that by increasing the optical path length of the head-up display, the position of the projected image can be adjusted within a larger range.

  By changing the voltage applied to the light deflection liquid crystal cell 100, the position where the image by the light 26 is projected onto the windshield 25 is moved downward, and the position of the projected image (virtual image) 27 viewed from the same viewpoint position P. Is moved from P1 to P2 and P3. A position bent without maximum voltage (12 ° in this embodiment) without applying a voltage is the position P1, and the optical path (optical axis) at that time is OP1. Further, the state where the voltage is not applied and the light is not bent is the position P3, and the optical path (optical axis) at that time is OP3. Furthermore, the state in which the intermediate voltage is applied is P2, and the optical path (optical axis) at that time is OP2.

  The light 26 of the image that passes through the optical path (optical axis) OP1 passes through the first region R1 that is the thin part of the multifocal lens 31 (the part that has the shortest focal length while passing through the optical paths OP1 to OP3). It passes through and is projected onto the windshield 25 as a projection image 27s smaller than the projection image passing through the other optical path OP2 or OP3. At this time, since the focal length is shortened, the projected image 27s appears far away.

  The light 26 of the image passing through the optical path (optical axis) OP2 is a third region where the lens thickness of the multifocal lens 31 is an intermediate portion (a portion having an intermediate focal length while passing through the optical paths OP1 to OP3). It passes through R3 and is projected onto the windshield 25 as a projection image 27m that is larger than the other optical paths OP1 and smaller than the projection image passing through OP3. At this time, since the focal length is longer than that of the projection image 27s, the projection image 27m appears closer to the projection image 27s.

  The light 26 of the image passing through the optical path (optical axis) OP3 passes through the second region R2, which is the portion where the lens thickness of the multifocal lens 31 is thick (the portion where the focal length is the longest through the optical paths OP1 to OP3). It passes through and is projected on the windshield 25 as a projection image 271 larger than the projection images passing through the other optical paths OP1 and OP2. At this time, since the focal length is longer than the projected images 27s and 27m, the projected image 27l appears closer than the projected images 27s and 27m.

  With the above configuration, by changing the voltage applied to the light deflection liquid crystal cell 100, the position at which the image 26 is projected onto the windshield 25 is moved downward, and the optical path 26 of the image changes along with the movement. Thus, by passing through portions of the multifocal lens 31 having different focal lengths, the size projected onto the windshield 25 can be increased and displayed closer as it moves downward.

  Even when the multifocal lens 31 having another configuration is used, the position where the image of the light 26 is projected onto the windshield 25 is moved downward, and the focal length of the multifocal lens 31 is set to be long. As a result, the above-described effects can be obtained. For example, when a plurality of single focus lenses are used in combination, a lens having the shortest focal length is disposed in the first region R1 on the optical path OP1, and the second region R2 on the optical path OP3 is the most focused. A lens having a long distance may be provided, and a lens having an intermediate focal length may be disposed in the third region R3 on the optical path OP2. In the case of using a liquid crystal lens or a variable focus lens, the position where the image by the light 26 is projected onto the windshield 25 may be moved downward and controlled to increase the focal length thereof.

  In recent years, the number of vehicles equipped with car navigation systems is increasing, but it may be difficult to know which alley the driver should turn in, such as when there are many alleys. Therefore, as shown in FIG. 6, the head-up display of this embodiment is used to display the direction of travel on the windshield 25 and the arrow (virtual image) 27 according to the actual environment (scenery), and the intersection where the vehicle should actually bend is displayed. Can be strongly recognized. In FIG. 6A, an intersection that should actually bend (hereinafter simply referred to as “target intersection”) is indicated by an arrow 27. When the vehicle moves forward from this state, as shown in FIG. 6 (B), the target intersection approaches, and accordingly, the position where the arrow 27 and the target intersection can be seen shifts, but the light deflection liquid crystal cell 100 By controlling the voltage applied to, the display position of the arrow 27 is moved downward and the size thereof is increased, so that the position of the arrow 27 can always be adjusted to the position where the target intersection is visible.

  In the case of the example shown in FIG. 6, the control unit 28 obtains position information of the vehicle 30 (distance information to the target intersection, elevation information by the 3D sensor, steering angle information, etc.) from a car navigation system or the like mounted on the vehicle 30. The voltage acquired is controlled, and the voltage applied to the light deflection liquid crystal cell 100 is controlled based on the acquired position information. For example, as the distance to the target intersection decreases, the voltage applied to the light deflection liquid crystal cell 100 is increased, the angle at which the light 26 of the image is bent by the light deflection liquid crystal cell 100 is reduced, and the projection projected onto the windshield 25. The position of the image (arrow) 27 is moved downward. At this time, the light 26 of the image passes through a portion where the focal length of the multifocal lens 31 is relatively long, and the size of the projection image (arrow) 27 becomes large so that it appears to be close.

  In this way, by moving the position and size of the projection image (arrow) 27 in accordance with the progress (position) of the vehicle 30, the driver can drive without making a mistake in the target intersection. Further, the brightness of the projected image 27 of the arrow can be set to be darker when the distance from the vehicle 30 to the target intersection is far, and can be emphasized by setting the brightness to be brighter as it approaches. Therefore, the head-up display using the light deflecting liquid crystal cell 100 according to the embodiment of the present invention displays the arrow 27 or the like on the windshield 25 as in the above example, and displays the traveling direction in synchronization with the actual scenery. It is suitable for a navigation system.

  FIG. 7 is a conceptual diagram showing a configuration example of the optical system 20 of the head-up display capable of preventing the external light from entering the liquid crystal display device.

  Although the basic configuration is the same as the example shown in FIG. 5, the positional relationship between the light deflection liquid crystal cell 100 and the liquid crystal display device 22 is different. The light deflection liquid crystal cell 100 is disposed at a predetermined distance from the liquid crystal display device 22. This distance is at least when the light is bent at a maximum angle (in this example, 12 °) possible with the light deflection liquid crystal cell 100, the external light 29 incident on the light deflection liquid crystal cell 100 from the direction of the windshield 25 is the liquid crystal display device. This distance is sufficient to prevent the light from entering the 22 display surface.

  Generally, when a strong light beam 29 such as sunlight enters the optical system 20 from the direction of the windshield 25 as backlight, the virtual image 27 becomes difficult to see. This is because the incident external light 29 is scattered on the surface of the liquid crystal display device 22 and the brightness of the projected image of the liquid crystal display device 22 is relatively lowered, so that the contrast ratio is lowered.

  In this case, measures such as increasing the luminous intensity of the light source 21 for the backlight to make the virtual image 27 brighter are necessary, but the contrast ratio is expressed by “illuminated part luminance / non-illuminated part luminance”. A large improvement effect cannot be obtained only by increasing the luminance of the light source.

  In the present embodiment, by restricting the incidence of the light beam 29 such as sunlight on the liquid crystal display device 22, the above-described increase in the non-lighting portion luminance can be suppressed and the problem can be solved.

  When outside light 29 such as sunlight comes in the direction in which the liquid crystal display device 22 is incident, for example, a sensor (not shown) or the like senses that the light 29 has entered the liquid crystal display device 22, and the control unit The voltage applied to the light deflection liquid crystal cell 100 is adjusted by 28, and the optical path is switched so that the light 29 is released so that the sunlight 29 does not enter the liquid crystal display device 22. At this time, although the position of the projected image 27 may slightly deviate from the optimum position, the driver can recognize the projected image. With such a configuration, it is possible to take a countermeasure against backlight without setting the luminance of the light source 21 high.

  In the example of FIG. 7, the light rays that pass through the regions R1 and R3 of the multifocal lens are refracted, and the light rays 26 from the liquid crystal display device and the external light 29 follow different optical paths. Here, by setting a sufficiently long optical path from the multifocal lens 31 to the light deflection liquid crystal cell 100 or the liquid crystal display device 22, the outside light 29 is configured not to reach the light deflection liquid crystal cell 100 or the liquid crystal display device 22. Can do. Since the outside light 29 does not reach, the outside light 29 does not affect the virtual image 27.

  In the example of FIG. 7, the light beam that passes through the multifocal lens region R <b> 2 follows the optical path between the front glass 25 and the light deflection liquid crystal cell 100 where the external light 29 and the projected image light 26 are substantially the same. In this case, the switching of the optical path described above works effectively.

  As described above, according to the embodiment of the present invention, the focal distance can be changed depending on the display position of the projection image 27, so that the focus movement of the eyes can be reduced. In addition, the projected display is intuitively easy to understand. Furthermore, since the projected image 27 can be displayed near the focal point of the eye, the movement of the line of sight can be reduced.

  Further, according to the embodiment of the present invention, if the light emitted from the liquid crystal display device 22 is linearly polarized light, the light deflecting liquid crystal cell 100 can bend all the light. The angle at which light can be bent by the light deflecting liquid crystal cell 100 varies depending on the cell structure (prism shape, refractive index anisotropy of liquid crystal, etc.), but can be bent up to about 18 °. is there.

  Further, according to the embodiment of the present invention, the position of the projected image by the projector optical system such as the head-up display can be continuously controlled by the voltage without the mechanical operation unit. Therefore, it is possible to adjust the position of the image according to the height of the viewpoint. Furthermore, it is possible to adjust the height of the viewpoint, the position of the projected image, and the position of the actual landscape.

  In the above-described embodiment, the head-up display mounted on the vehicle 30 has been described as an example. However, since the angle can be adjusted according to the movement, the pitch posture of the ship, helicopter, agricultural machine, etc. varies greatly. It is also suitable for a head-up display mounted on an object.

  Further, according to the embodiment of the present invention, it is possible to take measures against backlight of the projector optical system without increasing the luminance of the light source.

  In the above-described embodiment, only an example in which light is bent up and down by the light deflecting liquid crystal cell 100 has been described. However, by changing the direction of the prism layer 3, the light can be bent in the left-right direction or the oblique direction. Further, by using two light deflection liquid crystal cells 100, it is possible to bend light in the vertical direction and the horizontal direction.

  In the above-described embodiment, the light deflection liquid crystal cell 100 is disposed between the liquid crystal display device 22 and the reflection plate 24. However, the light deflection liquid crystal cell 100 is disposed on the reflection plate 24 or between the reflection plate 24 and the multifocal lens 31. It may be.

  Further, the multifocal lens 31 and the reflection plate 24 may be formed at once by forming a reflective metal on the multifocal lens.

  Further, the light deflection liquid crystal cell 100 of the example has a high transmittance as compared with a liquid crystal optical element using a polarizing plate. The light transmittance of each cell is expected to be 90% or higher, and 95% or higher due to the antireflection coating.

  Further, in the above-described embodiment, a triangular prism is used and the base angles are 45 ° and 90 °, but the base angle is not limited to this. For light rays that are perpendicularly incident on the substrate, the slope rising from the substrate at an appropriately gentle angle constitutes a prism, and the surface rising at a base angle close to vertical does not constitute a prism. With such a configuration, each cell can be easily deflected in one direction.

  In the above embodiment, the pitch of the triangular prisms is 20 μm. The prism pitch is preferably in the range of 1 μm to 100 μm.

  The shape of the prism is not limited to that shown in the embodiment, and for example, the cross-sectional shape may be a sine curve.

  Further, as a light source, in addition to a light emitting diode (LED), for example, an HID lamp, a field emission (FE) light source, a fluorescent lamp, and the like are conceivable.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited thereto. It will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

DESCRIPTION OF SYMBOLS 1, 11 Glass substrate 2, 12 Transparent electrode 3 Prism layer 3a Prism 3b Base layer 13 Orientation film 14 Gap control agent 15 Liquid crystal layer 20 Optical system 21 Light source 22 Liquid crystal display device 24 Reflector 25 Front glass (combiner)
26 Image Light 27 Projected Image 28 Control Unit 29 External Light 30 Vehicle 31 Multifocal Lens 100 Light Deflection Liquid Crystal Cell

Claims (1)

  1. An image display device for outputting linearly polarized images;
    An optical system including a light deflection liquid crystal cell and a lens having a plurality of focal points arranged at a subsequent stage of the light deflection liquid crystal cell, and projecting an image output from the image display device;
    A head-up display having a control unit,
    The light deflection liquid crystal cell is
    A pair of first and second transparent substrates facing each other;
    A pair of first and second transparent electrodes formed on the first and second transparent substrates and applying a voltage between the first and second transparent substrates;
    A prism layer having a prism formed above one of the first and second transparent substrates;
    An alignment film formed on the prism layer and subjected to an alignment process in parallel with the polarization direction of the output of the image display device;
    A liquid crystal layer sandwiched between the first and second transparent substrates and having liquid crystal molecules,
    The control unit changes a refractive index of the liquid crystal layer by changing a voltage applied to the first and second transparent electrodes according to information from the outside to change an interface between the inclined surface of the prism and the liquid crystal layer. A head-up display that controls the projection position and size of the image by controlling the refraction angle of the light of the image passing through the screen.
JP2011156781A 2011-07-15 2011-07-15 Head-up display Withdrawn JP2013024921A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2011156781A JP2013024921A (en) 2011-07-15 2011-07-15 Head-up display

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2011156781A JP2013024921A (en) 2011-07-15 2011-07-15 Head-up display

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JP2013024921A true JP2013024921A (en) 2013-02-04

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014181025A (en) * 2013-03-15 2014-09-29 Honda Motor Co Ltd Solid head-up display comprising dynamic focal plane
CN104199188A (en) * 2014-09-01 2014-12-10 望新(上海)科技有限公司 Vehicle HUD light source system
JP2016064760A (en) * 2014-09-25 2016-04-28 アイシン・エィ・ダブリュ株式会社 Virtual image display device
US10215583B2 (en) 2013-03-15 2019-02-26 Honda Motor Co., Ltd. Multi-level navigation monitoring and control
US10339711B2 (en) 2013-03-15 2019-07-02 Honda Motor Co., Ltd. System and method for providing augmented reality based directions based on verbal and gestural cues

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014181025A (en) * 2013-03-15 2014-09-29 Honda Motor Co Ltd Solid head-up display comprising dynamic focal plane
US10215583B2 (en) 2013-03-15 2019-02-26 Honda Motor Co., Ltd. Multi-level navigation monitoring and control
US10339711B2 (en) 2013-03-15 2019-07-02 Honda Motor Co., Ltd. System and method for providing augmented reality based directions based on verbal and gestural cues
CN104199188A (en) * 2014-09-01 2014-12-10 望新(上海)科技有限公司 Vehicle HUD light source system
JP2016064760A (en) * 2014-09-25 2016-04-28 アイシン・エィ・ダブリュ株式会社 Virtual image display device

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