During high sunlight situations, people may wear sunglasses, including polarized sunglasses, while viewing a traditional head-up display (HUD). Such people may see ghost images on the traditional HUD, which are caused by reflections as a result of lighting interacting with the multiple internal surfaces of the components of the traditional HUD, specifically a thin-film transistor (TFT) liquid crystal display (LCD), an active polarization modulator such as a twisted nematic (TN) cell, and a hot mirror. When the TN cell and the hot mirror are placed in front of the TFT-LCD, four additional optical surfaces are introduced and ghost images are induced by these surfaces. Such ghost images and reflections can make it difficult for a user to clearly view the images on the traditional HUD. For example, ghost images reduce the contrast of the display content.
This section provides a general summary of the present disclosure and is not a comprehensive disclosure of its full scope or all of its features, aspects, and objectives.
Disclosed herein are example implementations of a head-up display (HUD). One example HUD includes a thin-film transistor liquid crystal display (TFT-LCD), an active polarization modulator, and a wavelength filter. The active polarization modulator and the wavelength filter are optically bonded to the TFT-LCD.
Also disclosed herein are example implementations of a system for a HUD. One example system includes an active polarization modulator front plate and a coating. The coating is adjacent to the active polarization modulator front plate. The system also includes an active polarization modulator rear plate, and an LCD front plate. The system further includes a first reflective polarizer and an LCD rear plate. The first reflective polarizer is adjacent to the active polarization modulator rear plate and the LCD front plate. The system further includes a second reflective polarizer. The second reflective polarizer is adjacent to the LCD rear plate.
Also disclosed herein are example implementations of a display device compatible with polarized sunglasses. One example display device includes a display for displaying information and a half-wave plate. The display includes stacked components to reduce internal surfaces. The half-wave plate is coupled to the display and arranged to receive S-polarized light from the display. The stacked components reduce a ghost image on the display.
The disclosure is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to-scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity.
The following description is merely exemplary in nature and is not intended to limit the disclosure in its application or uses. For purposes of clarity, the same reference numbers are used in the description and drawings to identify similar elements.
A head-up display (HUD) panel that offers both improved viewing by a user wearing polarized sunglasses and improved viewing in high sunlight situations is desirable. Certain embodiments of the present disclosure may, for example, relate to a HUD panel that offers improved viewing by a user wearing polarized sunglasses and improved viewing in high sunlight situations. Certain embodiments may combine the internal surfaces of components of the HUD panel, eliminating the reflections and ghost images. For example, one or more embodiments may describe stacking discrete components in a picture generation unit (PGU) of the HUD to provide a compact PGU design. One or more embodiments may describe reducing or eliminating extra optical surfaces, which traditionally result from stacking discrete components, like a TFT-LCD, an active polarization modulator, such as a TN cell, and a hot mirror. Reducing or eliminating the extra optical surfaces may reduce or eliminate ghosting.
The term HUD is used herein to refer to display devices employed in components or systems, such as but not limited to a window of a vehicle, lens, or visor.
Light passing through the HUD panel 200 may be reflected or polarized. For example, light that is P-polarized is polarized parallel to a plane of incidence which in a HUD is the plane formed by gut rays 108 and 110. Light that is S-polarized is polarized perpendicular to a plane of incidence. A TFT-LCD polarizes light in either P-polarization or S-polarization.
In one example embodiment, the stacked HUD TFT-LCD can be configured as follows: 1) the anti-reflection and infrared cut-off coating 202 is positioned adjacent the active polarization modulator front plate 204; 2) the first LC 206 is positioned between the active polarization modulator front plate 204 and the active polarization modulator rear plate 208; 3) the first reflective polarizer 210 is positioned adjacent the LCD front plate 212; 4) the second LC 214 is positioned between the LCD front plate 212 and the LCD rear plate 216; and 5) the second reflective polarizer 218 is positioned adjacent the LCD rear plate 216. The HUD panel 200 can include additional and/or fewer components and configurations and is not limited to those illustrated in
The HUD panel 200 can be incorporated into a windshield of a vehicle. For a windshield HUD (WHUD) to be compatible with polarized sunglasses, the HUD panel 200 includes an electro-optical element, such as the TN cell 220 to modulate the polarization from the TFT-LCD 222. The HUD panel 200 may include a wavelength filter, such as the hot mirror 224, to increase the sunlight resistance of the TFT-LCD 222. In a traditional HUD panel 200, adding these two extra elements in front of the TFT-LCD 222 introduces four additional optical surfaces, which can induce ghost images. These ghost images reduce the contrast of the WHUD content. To eliminate the ghosting, the HUD panel 200 is stacked in such a configuration to eliminate the additional optical surfaces. For example, by properly stacking various elements, such as the TFT-LCD 222, the TN cell 220, and the hot mirror 224, the additional optical surfaces are eliminated. As described in one or more embodiments, properly stacking various elements of the HUD panel 200 may include stacking the hot mirror 224 in front of the TN cell 220, which is stacked in front of the LCD 222. In this configuration, a PGU of the WHUD system can maintain its polarized sunglasses compatibility and sunlight resistance requirements.
In this embodiment, the TN cell 220 can be separated from TFT-LCD 222. The TN cell 220 and the TFT-LCD 222 do not share the same linear polarizer. TFT-LCD 222 can have a front linear polarizer (e.g., the second linear polarizer 228) and the TN cell 220 can have its own linear polarizer (e.g., the first linear polarizer 226) on a surface toward the TFT-LCD 222. The linear polarizers 226, 228 can be absorptive to reduce ghost image visibility. There is an air gap 230 in between these two linear polarizers 226, 228. Air flow can be forced to pass through the air gap 230 in order to take heat away from both linear polarizers 226, 228.
Table 1 shown below illustrates power consumption comparisons of PGUs to meet 950 cd/m2 V-polarized Brightness and 15000 cd/m2 Total Brightness requirements.
As shown in Table 1, a PGU with the active TN cell 220 is more efficient than an S-polarized TFT-LCD PGU, a 45° linear polarized TFT-LCD PGU, and a 42° linear polarized TFT-LCD PGU. The WHUD system with the active TN cell 220 is therefore more efficient. The WHUD system with the active TN cell 220 has lower light energy absorption on an LCD in an ON condition for the V-polarized brightness and an OFF condition for the total brightness. In this example, V-polarized refers to the light that is vertically polarized to the ground. There can be some power in V-polarization while the output from the PGU are all S-polarization due to the windshield azimuth angle. Furthermore, using the active TN cell 220 in the HUD panel 200 results in a lower temperature rise on the LCD and a lower current demand for a light-emitting diode (LED).
The TN cell 220 can be positioned or sandwiched between two plates made of glass. The hot mirror 224 is an optical mirror reflecting infrared (IR) and allowing visible light to pass through. The hot mirror 224 may need a substrate to carry a thin film coating. Usually the thin film is designed to be low reflection in the visible light spectrum and high reflection in the infrared spectrum. Thus, the TN cell 220 can be the substrate of the thin film coating to provide both polarization control and hot mirror 224 functions simultaneously. This stacked configuration of the HUD panel 200 eliminates two surfaces. The TN cell 220 and hot mirror 224 are integrated in the HUD panel 200 and can be optically bonded to the TFT-LCD 222 to eliminate another two surfaces. After this integration, the HUD panel 200 has only two optical surfaces, which is the same amount of optical surfaces as a traditional TFT-LCD 222.
A first polarizer, such as the first reflective polarizer 210 can be located on a front plate, such as the LCD front plate 212 of the TFT-LCD 222. The first reflective polarizer 210 can be a reflective type to reflect the excess amount of solar radiation from heating the entire stack. A second polarizer, such as the second reflective polarizer 218, can be located on a rear TFT-LCD plate, such as the LCD rear plate 216. The second reflective polarizer 218 can also be a reflective type to reflect the unusable portion of the flux from backlight from heating the entire stack. Such example configurations can prevent or reduce ghosting and stray light.
The display panel 703 can be configured either to output S-polarized light 306 or P-polarized light 308. The either S-polarized light 306 or P-polarized light 308 can travel between the display panel 703 and the half-wave plate 704 along an optical axis 712. For illustrative purposes, either the S-polarized light 306 or P-polarized light 308 is polarized in the direction of 708 while the direction 714 is orthogonal to the direction of 708.
The HUD panel 200 can include a half-wave plate 704 coupled to the either S-polarized or P-polarized display panel 703. The half-wave plate 704 can be arranged to receive any polarization of light from the display panel 703.
The HUD panel 200 can also include a voltage waveform generator 706. The voltage waveform generator 706 can be coupled to the half-wave plate 704. The voltage waveform generator 706 can be configured to orient a fast axis 710. The voltage waveform generator 706 can orient the fast axis 710 at 45 degrees with respect to the linear polarized light polarization from display panel 703 to modulate the polarization to the orthogonal direction perpendicular to optical axis, or to any other desirable linear polarization state via other desirable fast axis angle with respect to the linear polarized light polarization from display panel 703. The voltage waveform generator 706 can be an ON/OFF switch. For example, by switching the polarization of PGU to the P state (e.g. the ON state), the image content can be seen by a person wearing polarized sunglasses. By switching the polarization of PGU to the S state (e.g. the OFF state), the image content cannot be seen by a person wearing polarized sunglasses.
When sunlight is at the top of the atmosphere at radiation level 810, the spectral irradiance 802 peaks at approximately 2 W/m2/nm in the visible light spectrum 806. The spectral irradiance 802 decreases as the wavelengths increase through the IR light spectrum 808. The radiation level 810 can be approximated to the radiation level 812 which is the 5250 degrees Celsius black-body radiation. At radiation level 814, the radiation is at sea level and absorption from atmosphere molecules causes the spectral irradiance 802 begins to plateau.
Diagram 902 includes the reflective polarizer 904. The reflective polarizer 904 can be on the TN cell 220 or on the TFT-LCD 222. In this configuration, sunlight 906 passes through the reflective polarizer 904 in a direction 908. Approximately 50% of the visible light from sunlight 906 is transmitted in the direction 908 and 50% of the visible light from sunlight 906 is reflected in a direction 910.
Diagram 912 includes a hot mirror 914. The hot mirror 914 can be the TN cell 220 or the hot mirror 224. In this configuration, sunlight 906 passes through the hot mirror 914 in a direction 908. Most of the visible light from sunlight 906 is transmitted in the direction 908 and most of the IR light is reflected in a direction 916.
While the disclosure has been described in connection with certain embodiments, it is to be understood that the disclosure is not to be limited to the disclosed embodiments but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the scope of the appended claims, which scope is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures as is permitted under the law.