Maintaining color consistency for head-up displays

Abstract

A head-up display (HUD) system of a vehicle includes a vehicle windshield including a coating coated thereon, and an HUD projector adapted to project an image onto an interior surface of the vehicle windshield wherein the coating coated on the windshield provides different reflectivity characteristics for different color components of the projected image, the HUD projector is adapted to individually calibrate the polarization of each of the different color components of the projected image to maintain consistent brightness and intensity characteristics within the image reflected from the windshield interior surface.

Description

Technical Field

[0001] The present disclosure relates to a head-up display (HUD) system in a vehicle. Head-up displays are already very common in modern vehicles. The HUD projects useful information such as speed and navigation information into the driver's field of view. This avoids forcing the driver to look down at the instruments on the vehicle dashboard and thus away from the road. This reduces driver distraction and keeps the driver's line of sight focused on the road at all times. Background Art

[0002] Modern windshields include various coatings disposed thereon, which affect the reflectivity of the windshield and thus the brightness / intensity of the image reflected by the windshield to the passenger's eyes that is projected by the HUD system. The coatings on the windshield may have different effects on different colors of the projected image. For example, compared to the blue and green components of the projected image, the windshield coating may reduce the reflectivity of the red component of the projected image. Therefore, the red in the image reflected to the passenger will appear with a lower brightness or intensity.

[0003] Although current systems achieve their intended purpose, there is still a need for a new and improved HUD system and method for providing a HUD image to a passenger within a vehicle, in which the colors of the projected image have consistent brightness / intensity as perceived by the passenger. Summary of the Invention

[0004] According to several aspects of the present disclosure, a head-up display (HUD) system for a vehicle includes a vehicle windshield and a HUD projector. The vehicle windshield includes a coating applied thereto. The HUD projector is adapted to project an image onto the inner surface of the vehicle windshield, wherein the coating applied to the windshield provides different reflectivity characteristics for different color components of the projected image, and the HUD projector is adapted to individually calibrate the polarization of each of the different color components of the projected image to maintain consistent brightness and intensity characteristics in the image reflected from the inner surface of the windshield.

[0005] According to another aspect, the HUD projector includes a red laser and a first spatial light modulator (SLM) associated with the red laser, wherein the red laser is adapted to project a red component beam through the first SLM to a collimator; a green laser and a second SLM associated with the green laser, wherein the green laser is adapted to project a green component beam through the second SLM to the collimator; and a blue laser and a third SLM associated with the blue laser, wherein the blue laser is adapted to project a blue component beam through the third SLM to the collimator, wherein the collimator is adapted to collimate the red component beam, the green component beam, and the blue component beam into an image projected onto the inner surface of the windshield.

[0006] According to another aspect, the HUD projector is adapted to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the reflectivity characteristics of the coating on the windshield, such that each of the red component beam, the green component beam, and the blue component beam is reflected from the inner surface of the windshield with substantially equal brightness and intensity.

[0007] According to another aspect, the reflectivity characteristics of the coating on the windshield are wavelength-dependent.

[0008] According to another aspect, each of the red laser and the first SLM, the green laser and the second SLM, and the blue laser and the third SLM are rotated relative to each other to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0009] According to another aspect, the system further includes a first lens positioned between the first SLM and the collimator and adapted to calibrate the polarization of the red component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield; a second lens positioned between the second SLM and the collimator and adapted to calibrate the polarization of the green component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield; and a third lens positioned between the third SLM and the collimator and adapted to calibrate the polarization of the blue component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0010] According to another aspect, the first lens, the second lens, and the third lens are all wave plate retarders.

[0011] According to another aspect, the coating on the windshield is an infrared reflective (IRR) coating that is coated on the windshield and adapted to reflect external infrared light from the windshield, and the IRR coating provides a lower reflectivity for the red component beam than for the green component beam and the blue component beam.

[0012] According to another aspect, the red laser and the first SLM are rotated relative to the green laser and the second SLM and the blue laser and the third SLM such that the red component beam is projected onto the collimator in a manner with less than full P polarization based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0013] According to another aspect, the system further includes a wave plate retarder positioned between the first SLM and the collimator and adapted to calibrate the polarization of the red component beam to less than full P polarization based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0014] According to several aspects of the present disclosure, a method of providing an image to a passenger within a vehicle using a head-up display (HUD) system includes projecting an image onto an inner surface of a vehicle windshield using a HUD projector, wherein the windshield includes a coating applied thereto that provides different wavelength-dependent reflectivity characteristics for different color components of the projected image, and calibrating the polarization of each of the different color components of the projected image individually using the HUD projector to maintain consistent brightness and intensity characteristics within the image reflected from the inner surface of the windshield.

[0015] According to another aspect, projecting an image onto an inner surface of a vehicle windshield using a HUD projector further includes: projecting a red component beam onto a collimator using a red laser through a first spatial light modulator (SLM) associated with the red laser, projecting a green component beam onto the collimator using a green laser through a second SLM associated with the green laser, projecting a blue component beam onto the collimator using a blue laser through a third SLM associated with the blue laser, and the method further includes collimating the red component beam, the green component beam, and the blue component beam using the collimator into an image projected onto the inner surface of the windshield.

[0016] According to another aspect, calibrating the polarization of each of the different color components of the projected image individually using the HUD projector to maintain consistent brightness and intensity characteristics within the image reflected from the inner surface of the windshield further includes: using the HUD projector to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the reflectivity characteristics of the coating on the windshield such that each of the red component beam, the green component beam, and the blue component beam reflects from the inner surface of the windshield with substantially equal brightness and intensity.

[0017] According to another aspect, individually calibrating the polarization of each of the red component beam, the green component beam, and the blue component beam based on the reflectivity characteristics of the coating on the windshield using the HUD projector further includes rotating each of the red laser and the first SLM, the green laser and the second SLM, and the blue laser and the third SLM relative to each other to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0018] According to another aspect, using an HUD projector, separately calibrating the polarization of each of a red component beam, a green component beam, and a blue component beam based on the reflectivity characteristics of a coating on a windshield further includes using a first waveplate retarder positioned between a first SLM and a collimator to calibrate the polarization of the red component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield, using a second waveplate retarder positioned between a second SLM and the collimator to calibrate the polarization of the green component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield, and using a third waveplate retarder positioned between a third SLM and the collimator to calibrate the polarization of the blue component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0019] According to another aspect, the coating on the windshield is an infrared reflective (IRR) coating that is coated on the windshield and adapted to reflect external infrared light from the windshield, and the IRR coating provides a lower reflectivity of the red component beam than that of the green component beam and the blue component beam. Separately calibrating the polarization of each of a red component beam, a green component beam, and a blue component beam based on the reflectivity characteristics of a coating on a windshield using an HUD projector further includes rotating the red laser and the first SLM relative to the green laser and the second SLM and the blue laser and the third SLM such that the red component beam is projected onto the collimator in a manner less than full P polarization based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0020] According to another aspect, the coating on the windshield is an infrared reflective (IRR) coating that is coated on the windshield and adapted to reflect external infrared light from the windshield, and the IRR coating provides a lower reflectivity of the red component beam than that of the green component beam and the blue component beam. Separately calibrating the polarization of each of a red component beam, a green component beam, and a blue component beam based on the reflectivity characteristics of a coating on a windshield using an HUD projector further includes using a waveplate retarder positioned between the first SLM and the collimator to calibrate the polarization of the red component beam to be less than full P polarization based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0021] According to several aspects of the present disclosure, a vehicle having a head-up display (HUD) system includes a vehicle windshield that includes a coating applied thereto; a HUD projector adapted to project an image onto an inner surface of the vehicle windshield, including a red laser and a first spatial light modulator (SLM) associated with the red laser, wherein the red laser is adapted to project a red component beam through the first SLM onto a collimator, a green laser and a second SLM associated with the green laser, wherein the green laser is adapted to project a green component beam through the second SLM onto the collimator, and a blue laser and a third SLM associated with the blue laser, wherein the blue laser is adapted to project a blue component beam through the third SLM onto the collimator, wherein the collimator is adapted to collimate the red component beam, the green component beam, and the blue component beam into an image projected onto the inner surface of the windshield; the coating applied to the windshield is an infrared reflective (IRR) coating adapted to reflect external infrared light from the windshield, the IRR coating provides a wavelength-dependent reflectivity for the red component beam that is less than the reflectivities of the green component beam and the blue component beam, and the HUD projector is adapted to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the reflectivity characteristics of the coating on the windshield such that each of the red component beam, the green component beam, and the blue component beam reflects from the inner surface of the windshield with substantially equal brightness and intensity.

[0022] According to another aspect, each of the red laser and the first SLM, the green laser and the second SLM, and the blue laser and the third SLM are rotated relative to each other to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0023] According to another aspect, the vehicle further includes a first waveplate retarder positioned between the first SLM and the collimator and adapted to calibrate the polarization of the red component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield; a second waveplate retarder positioned between the second SLM and the collimator and adapted to calibrate the polarization of the green component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield, and a third waveplate retarder positioned between the third SLM and the collimator and adapted to calibrate the polarization of the blue component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

[0024] Based on the description provided herein, further applicable fields will become apparent. It should be understood that the specification and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Description of the Drawings

[0025] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way.

[0026] Figure 1 is a schematic view of a vehicle according to an exemplary embodiment of the present disclosure;

[0027] Figure 2 is a schematic view of the HUD system of the present disclosure according to an exemplary embodiment;

[0028] Figure 3 is a schematic view of the HUD system, the vehicle windshield, and the in-vehicle passengers;

[0029] Figure 4 is a schematic view of the HUD system, in which the polarization of the component beams is accomplished by rotating the laser / SLM for each component beam;

[0030] Figure 5 is a schematic view of the HUD system, in which the polarization of the component beams is accomplished by lenses positioned between each laser / SLM and the collimator; and

[0031] Figure 6 is a schematic flow chart showing a method according to an exemplary embodiment of the present disclosure.

[0032] The accompanying drawings are not necessarily drawn to scale, and some features may be enlarged or minimized to show details of particular components. In some cases, well-known components, systems, materials, or methods have not been described in detail to avoid obscuring the present disclosure. Accordingly, the specific structural and functional details disclosed herein should not be construed as limiting, but only as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to employ the present disclosure in various ways. Detailed Description

[0033] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application or use. In addition, there is no intention to be bound by any express or implied theory presented in the aforementioned technical field, background technology, summary of the invention or the following specific embodiments. It should be understood that throughout the drawings, corresponding reference numerals represent similar or corresponding parts and features. The term "module" as used herein refers to any hardware, software, firmware, electronic control component, processing logic and / or processor device, alone or in any combination, including but not limited to: application specific integrated circuits (ASICs), electronic circuits, processors (shared, dedicated or group) and memories that execute one or more software or firmware programs, combinational logic circuits and / or other suitable components that provide the described functions. Although the drawings shown herein depict examples with certain element arrangements, additional intermediate elements, devices, features or components may be present in actual embodiments. It should also be understood that the drawings are merely illustrative and may not be drawn to scale.

[0034] As used herein, the term "vehicle" is not limited to automobiles. Although this technology is primarily described in conjunction with automobiles, it is not limited to automobiles. These concepts can be used in a variety of applications, such as aircraft, ships, other vehicles, and consumer electronics components.

[0035] According to an exemplary embodiment, Figure 1 A vehicle 10 is shown having an associated head-up display (HUD) system 11 for generating images for passengers within the vehicle 10, according to various embodiments. Generally speaking, the system 11 works in conjunction with other systems within the vehicle 10 to display various information and infotainment content to the passengers. The vehicle 10 generally includes a chassis 12, a body 14, front wheels 16, and rear wheels 18. The body 14 is disposed on the chassis 12 and substantially surrounds the components of the vehicle 10. The body 14 and chassis 12 can together form a vehicle frame. The front wheels 16 and rear wheels 18 are each rotatably coupled to the chassis 12 near respective corners of the body 14.

[0036] In various embodiments, vehicle 10 is an autonomous vehicle, and system 11 is incorporated into autonomous vehicle 10 (hereinafter referred to as autonomous vehicle 10). For example, autonomous vehicle 10 is a vehicle that is automatically controlled to transport passengers from one location to another. Although vehicle 10 is depicted as a passenger car in the illustrated embodiment, it should be understood that any other vehicle may also be used, including motorcycles, trucks, sport utility vehicles (SUVs), recreational vehicles (RVs), etc. In an exemplary embodiment, autonomous vehicle 10 is a so-called level 4 or level 5 automation system. A level 4 system represents "high automation" and refers to the driving mode-specific performance of an autonomous driving system in all aspects of a dynamic driving task, even if the human driver does not appropriately respond to an intervention request. A level 5 system represents "full automation" and refers to the full-time performance of an autonomous driving system in all aspects of a dynamic driving task under all road and environmental conditions that a human driver can manage.

[0037] As shown, autonomous vehicle 10 generally includes a propulsion system 20, a driveline 22, a steering system 24, a braking system 26, a sensor system 28, an actuator system 30, at least one data storage device 32, a controller 34, and a communication system 36. In embodiments where autonomous vehicle 10 is an electric vehicle, there may be no driveline 22. In various embodiments, propulsion system 20 may include an internal combustion engine, an electric motor such as a traction motor, and / or a fuel cell propulsion system. Driveline 22 is configured to transfer power from propulsion system 20 to the front wheels 16 and rear wheels 18 of the vehicle according to selectable gear ratios. According to various embodiments, driveline 22 may include a stepped automatic transmission, a continuously variable transmission, or other suitable transmissions. Braking system 26 is configured to provide braking torque to the front wheels 16 and rear wheels 18 of the vehicle. In various embodiments, braking system 26 may include friction brakes, brake-by-wire, a regenerative braking system (such as an electric motor), and / or other suitable braking systems. Steering system 24 affects the position of the front wheels 16 and rear wheels 18. Although depicted as including a steering wheel for illustrative purposes, in some embodiments contemplated within the scope of the present disclosure, steering system 24 may not include a steering wheel.

[0038] The sensor system 28 includes one or more sensing devices 40a - 40n that sense observable conditions of the external environment and / or the internal environment of the autonomous vehicle 10. The sensing devices 40a - 40n can include, but are not limited to, radar, lidar, global positioning system, optical cameras, thermal cameras, ultrasonic sensors, and / or other sensors. The cameras can include two or more digital cameras spaced a selected distance apart from each other, where the two or more digital cameras are used to obtain a stereoscopic image of the surrounding environment in order to obtain a three-dimensional image. The sensing devices 40a - 40n can include sensors that monitor dynamic variables of the vehicle, such as the speed of the vehicle, acceleration, the number of times brakes are applied, etc. The actuator system 30 includes one or more actuator devices 42a - 42n that control one or more functions of the vehicle 10, such as, but not limited to, the propulsion system 20, the transmission system 22, the steering system 24, and the braking system 26.

[0039] The vehicle controller 34 includes at least one processor 44 and a computer-readable storage device or medium 46. The at least one data processor 44 can be any custom or commercially available processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor among multiple processors associated with the vehicle controller 34, a semiconductor-based microprocessor (in the form of a microchip or chipset), a macroprocessor, any combination thereof, or any device commonly used to execute instructions. The computer-readable storage device or medium 46 can include, for example, volatile and non-volatile storage devices such as read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operating variables when the at least one data processor 44 is powered off. The computer-readable storage device or medium 46 can be implemented using any of a variety of known storage devices, such as PROM (programmable read-only memory), EPROM (electrical PROM), EEPROM (electrically erasable PROM), flash memory, or any other electrical, magnetic, optical, or combination storage device capable of storing data, where some of the data represents executable instructions used by the controller 34 in controlling the vehicle 10.

[0040] These instructions can include one or more separate programs, each program including an ordered list of executable instructions for implementing a logical function. When executed by the at least one processor 44, the instructions receive and process signals from the sensor system 28, execute logic, calculations, methods, and / or algorithms for automatically controlling components of the autonomous vehicle 10, and generate control signals to the actuator system 30 to automatically control components of the autonomous vehicle 10 based on the logic, calculations, methods, and / or algorithms. Although Figure 1Only one controller 34 is shown, but embodiments of the autonomous vehicle 10 can include any number of controllers 34 that communicate and cooperate via any suitable communication medium or combination of communication media to process sensor signals, execute logic, computations, methods, and / or algorithms, and generate control signals to automatically control the functions of the autonomous vehicle 10.

[0041] In various embodiments, one or more instances of instructions of the vehicle controller 34 are instantiated in a trajectory planning system and, when executed by at least one data processor 44, generate a trajectory output that addresses the kinematic and dynamic constraints of the environment. For example, the instructions receive process sensor and map data as inputs. These instructions execute graph-based methods and custom cost functions to handle different road scenarios in urban and highway settings.

[0042] The communication system 36 is configured to wirelessly communicate information with other remote entities 48, such as but not limited to other vehicles ("V2V" communication), infrastructure ("V2I" communication), remote systems, remote servers, cloud computers, and / or personal devices. In an exemplary embodiment, the communication system 36 is a wireless communication system configured to communicate via a wireless local area network (WLAN) using the IEEE 802.11 standard or via cellular data communication. However, additional or alternative communication methods, such as dedicated short-range communication (DSRC) channels, are also considered within the scope of the present disclosure. A DSRC channel refers to a one-way or two-way short-range to medium-range wireless communication channel designed specifically for automotive use, as well as a corresponding set of protocols and standards.

[0043] Reference Figure 2 , the HUD system includes a passenger monitoring system 52. The passenger monitoring system 52 includes a camera 54 adapted to monitor the head and eye positions of the passenger 50. The passenger monitoring system 52, commonly referred to as a driver monitoring system or DMS, is an artificial intelligence (AI)-based vehicle safety technology that monitors the attention of the passenger 50 via the camera 54. The purpose of the passenger monitoring system 52 is to identify the passenger and detect the level of vigilance through software and provide alerts in cases of drowsiness, distraction, etc. to avoid accidents. The main functions of the DMS are driver ID, distraction detection, drowsiness detection, specific activity detection, blink detection, emotion recognition, and eye tracking. The main purpose of the driver monitoring system 52 used within the HUD system 11 of the present disclosure is to monitor the position of the eyes and head of the passenger 50 and the direction of the passenger 50's gaze to determine the images to be displayed by the HUD system and the arrangement of such images.

[0044] The HUD system 11 further includes a computing engine 56 that communicates with the system controller 34A and the passenger monitoring system 52. The system controller 34A can be the vehicle controller 34 or can be a separate controller that communicates with the vehicle controller and is adapted to support communication between the system 11 and other systems within the vehicle 10 and receive data from sensors 40a - 40n within the vehicle 10. The computing engine 56 is adapted to compute an image 58 and encode the image 58 to the HUD projector 60. The HUD projector 60 can be any display suitable for projecting a holographic image.

[0045] Reference Figure 3 , the HUD projector 60 of the head-up display system 11 is adapted to project the image 58 onto the inner surface 62 of the windshield 64 of the vehicle 10. In an exemplary embodiment, the HUD projector 60 includes a red laser 66R and a first spatial light modulator (SLM) 68R associated with the red laser 66R, wherein the red laser 66R is adapted to project a red component beam 70R through the first SLM 68R onto a collimator 72. The HUD projector further includes a green laser 66G and a second SLM 68G associated with the green laser 66G, wherein the green laser 66G is adapted to project a green component beam 70G through the second SLM 68G onto the collimator 72, and finally includes a blue laser 66B and a third SLM 68B associated with the blue laser 66B, wherein the blue laser 66B is adapted to project a blue component beam 70B through the third SLM 68B onto the collimator 72. The collimator 72 is adapted to collimate the red component beam 70R, the green component beam 70G, and the blue component beam 70B into the image 58 projected onto the inner surface 62 of the windshield 64.

[0046] The first SLM 68R is irradiated by light from the red laser 66R, and the first SLM 68R diffracts the red laser with an encoded hologram. When irradiated, each pixel of the first SLM 68R will generate a wavefront, and the phase of the wavefront corresponds to the phase of the position of the hologram encoded at that pixel. The diffracted red laser together with the hologram encoded therein (red component beam 70R) then propagates to the collimator 72. The second SLM 68G is irradiated by light from the green laser 66G, and the second SLM 68G diffracts the green laser with an encoded hologram. When irradiated, each pixel of the second SLM 68G will generate a wavefront, and the phase of the wavefront corresponds to the phase of the position of the hologram encoded at that pixel. The diffracted green laser together with the hologram encoded therein (green component beam 70R) then propagates to the collimator 72. The third SLM 68B is irradiated by light from the blue laser 66B, and the third SLM 68B diffracts the blue laser with an encoded hologram. When irradiated, each pixel of the third SLM 68B will generate a wavefront, and the phase of the wavefront corresponds to the phase of the position of the hologram encoded at that pixel. Thereafter, the diffracted blue laser together with the hologram encoded therein (blue component beam 70R) propagates to the collimator 72.

[0047] The vehicle windshield 64 includes a coating 74 applied thereto. The coating 74 can be a polymer or ceramic coating that is sprayed or coated and dried or cured on the inner or outer surface of the windshield 64. The coating 74 can also be a solid layer or sheet of polymer or glass material positioned adjacent to and against the inner or outer surface of the windshield 64. The coating 74 is applied to the windshield 64 to provide a function useful for the passengers 50 inside the vehicle 10. For example, the coating 74 can provide coloring or anti-glare properties of the windshield 64.

[0048] This coating provides different reflectivity characteristics for different color components of the projected image 58. Specifically, the coating 74 provides different beam reflectivities based on the wavelength of the beam and thus based on the color of the beam. Therefore, the coating 74 will provide different reflectivities for the red component beam 70R, green component beam 70G, and blue component beam 70B of the image 58. This means that the brightness and intensity of a specific beam may be attenuated due to the lower reflectivity of the coating 74.

[0049] For example, in an exemplary embodiment, the coating 74 is an infrared reflective (IRR) coating that is applied to the windshield 64 and adapted to reflect external infrared light from the windshield 64. The reflectivity of the red component beam 70R provided by the IRR coating 74 is less than the reflectivities of the green component beam 70G and the blue component beam 70B. Therefore, when the image 50 is reflected from the inner surface 62 of the windshield 64 to the eyes of the passenger 50, the reflection of the red component beam 70R is less effective than the reflections of the green component beam 70G and the blue component beam 70B. Accordingly, when the passenger 50 views the projection image 58, the brightness and intensity of the red portion of the projection image 58 will be lower than those of the green and blue portions.

[0050] The HUD projector 60 is adapted to individually calibrate the polarization of each of the different color components of the projection image 58 so as to maintain consistent brightness and intensity characteristics within the image 58 when the image 58 is reflected from the inner surface 62 of the windshield 64. Accordingly, the HUD projector 60 is adapted to individually calibrate the polarization of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B based on the reflectivity characteristics of the coating 74 on the windshield 64 such that each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is reflected from the inner surface 62 of the windshield 64 with substantially equal brightness and intensity.

[0051] The red component beam 70R is projected from the red laser 66R and passes through the first SLM 68R in a fully P-polarized manner. Similarly, the green component beam 70G is projected from the green laser 66G and passes through the second SLM 68G in a fully P-polarized manner, and the blue component beam 70B is projected from the blue laser 66B and passes through the third SLM 68B in a fully P-polarized manner. Light is an electromagnetic wave, and the electric field of the wave oscillates perpendicular to the direction of propagation. If the direction of the electric field fluctuates randomly with time, the light is called unpolarized light. Many common light sources (such as sunlight, halogen lamps, LED spotlights, and incandescent bulbs) produce unpolarized light. If the direction of the electric field of the light is well-defined, it is called polarized light. The two most important orthogonal linear polarization states for reflection and transmission are called P-polarization and S-polarization. P-polarized light has an electric field polarized parallel to the plane of incidence, while S-polarized light is perpendicular to that plane.

[0052] The coating 74 provides a wavelength-dependent variation in the reflectivity of P-polarized light. The polarization of light is measured in degrees, where fully S-polarized light is 0 degrees (0°) and fully P-polarized light is ninety degrees (90°). In the above exemplary embodiment, the IRR coating reduces the reflectivity of fully P-polarized red light, and thus the brightness and intensity of the red component beam 70R are negatively affected.

[0053] To calibrate the polarization of each color component of the projection image 58 individually by the HUD projector 60, the HUD projector 60 must calibrate the polarization by making the polarization less P-polarized. In other words, the fully P-polarized light must be adjusted away from fully P-polarized (90°) and more towards S-polarized (0°). Referring again to the above exemplary embodiment, to increase the reflectivity of the red component beam 70R, the red component beam 70R is calibrated to have a polarization of, for example, 45°. The adjustment of the polarization of the red component beam 70R reduces the reduction in reflectivity caused by the coating 74. Thus, the red component beam 70R is reflected from the inner surface 62 of the windshield 64 with a brightness and intensity substantially equal to those of the green component beam 70G and the blue component beam 70B.

[0054] Reference Figure 4 , in the exemplary embodiment, each of the red laser 66R and the first SLM 68R, the green laser 66G and the second SLM 68G, and the blue laser 66B and the third SLM 68B is rotated relative to each other to individually calibrate the polarization of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B. The calibration of the polarization of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is based on the wavelength-dependent reflectivity characteristics of the coating 74 on the windshield 64 and how the coating 74 specifically affects the reflectivity of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B.

[0055] In the above example, the IRR coating does not negatively affect the reflectivity of the green component beam 70G and the blue component beam 70B, or at least not to the extent that the IRR coating negatively affects the reflectivity of the red component beam 70R. Thus, the red laser 66R and the first SLM 68R can be rotated relative to the green laser 66G / second SLM 68G and the blue laser 66B / third SLM 68B, as shown by the arrow 76, to individually calibrate the polarization of the red component beam 70R to less than full P-polarization, such that the reflectivity of the red component beam 70R approaches the reflectivity of the green component beam 70G and the blue component beam 70B, thereby making the reflectivities and brightness / intensities of the red, green, and blue component beams 70R, 70G, 70B consistent. '

[0056] Alternatively, the red laser 66R and the first SLM 68R can rotate with the rotation of each of the green laser 66G / second SLM 68G and the blue laser 66B / third SLM 68B, wherein each of the red laser 66R / first SLM 68R, the green laser 66G / second SLM 68G, and the blue laser 66B / third SLM 68B is calibrated to reduce the relative negative impact of the coating 74 on the reflectivity of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B. Based on the relative impact of the coating 74 on the reflectivity of each component beam, the rotation amount of each of the red laser 66R / first SLM 68R, the green laser 66G / second SLM 68G, and the blue laser 66B / third SLM 68B is calculated separately. Thus, the polarization of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is calibrated to improve the overall brightness / intensity of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B while ensuring the consistency of the reflectivity and brightness / intensity of the red, green, and blue component beams 70R, 70G, 70B.

[0057] Reference Figure 5 , in another exemplary embodiment, the HUD system 11 further includes a first lens 78R positioned between the first SLM 68R and the collimator 72 and adapted to calibrate the polarization of the red component beam 70R based on the wavelength-dependent reflectivity characteristics of the coating 74 on the windshield 64 when the red component beam 70R passes through the first lens 78R. A second lens 78G is positioned between the second SLM 68G and the collimator 72 and adapted to calibrate the polarization of the green component beam 70G based on the wavelength-dependent reflectivity characteristics of the coating 74 when the green component beam 70G passes through the second lens 78G. A third lens 78B is positioned between the third SLM 68B and the collimator 72 and adapted to calibrate the polarization of the blue component beam 70B based on the wavelength-dependent reflectivity characteristics of the coating 74.

[0058] In an example, the first lens 78R alone calibrates the polarization of the red component beam 70R to be less than full P polarization, such that the reflectivity of the red component beam 70R is close to the reflectivity of the green component beam 70G and the blue component beam 70B, thereby making the reflectivity and brightness / intensity of the red, green, and blue component beams 70R, 70G, 70B consistent.

[0059] In another example, the first lens 78R, the second lens 78G, and the third lens 78B simultaneously calibrate the polarization of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B to reduce the negative impact of the coating 74 on the reflectivity of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B. The calibration amount for each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is calculated separately based on the relative impact of the coating 74 on the reflectivity of each component beam. Therefore, the polarization of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is calibrated to improve the overall brightness / intensity of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B while ensuring the consistency of the reflectivity and brightness / intensity of the red, green, and blue component beams 70R, 70G, 70B.

[0060] In an exemplary embodiment, the first lens 78R, the second lens 78G, and the third lens 78B are all waveplate retarders. A waveplate retarder transmits light and changes its polarization state without attenuating, deviating, or shifting the light beam. They achieve this by retarding (or delaying) the polarization of one component with respect to its orthogonal component. Each waveplate retarder 78R, 78G, 78B is an optical device that changes the polarization state of the light wave passing through it. Birefringent polarizers rely on the dependence of the refractive index on the polarization of light. Different polarizations will be refracted at different angles, which can be used to select certain polarizations of light. In an exemplary embodiment, the lenses (waveplate retarders) 78R, 78G, 78B are all birefringent polarizers adapted to adjust the ratio of the S polarization to the P polarization in the red, green, and blue component beams 70R, 70G, 70B projected through them.

[0061] In another exemplary embodiment, each lens / waveplate retarder 78R, 78G, 78B includes a retardation layer having an inorganic birefringent film. The inorganic birefringent film may include columnar nanostructures formed on the lens / waveplate retarders 78R, 78G, 78B by oblique deposition. The columnar structure of the inorganic material formed on the lens / waveplate retarders 78R, 78G, 78B defines a birefringent film that retards the propagation of the light beam through the retardation layer, resulting in an adjustment of the ratio of the S polarization to the P polarization of the component beams 70R, 70G, 70B leaving the lens / waveplate retarders 78R, 78G, 78B.

[0062] By controlling the thickness and angular orientation of the columnar nanostructures, taking into account the relative negative impact of the coating 74 on the reflectivity of the red, green, and blue component beams 70R, 70G, 70B, the ratio of the S polarization and P polarization of the red component beam 70R, green component beam 70G, and blue component beam 70B projected by the first, second, and third lens / waveplate retarders 78R, 78G, 78B can be adjusted (reducing P polarization) for a particular application.

[0063] In an exemplary embodiment, the inorganic birefringent film is grown directly on the lens / waveplate retarders 78R, 78G, 78B. In another exemplary embodiment, the inorganic birefringent film is formed separately and then laminated to the lens / waveplate retarders 78R, 78G, 78B.

[0064] In another exemplary embodiment, the retardation layer of each of the lens / waveplate retarders 78R, 78G, 78B includes a liquid crystal lens connected to a voltage source, wherein the birefringence characteristics of the liquid crystal lens vary with the voltage applied to the liquid crystal lens. When the voltage applied to the liquid crystal lens changes, the birefringence characteristics of the liquid crystal lens are manipulated by changing the orientation of the liquid crystal molecules within the liquid crystal lens.

[0065] Reference Figure 6 , a method 100 of using a head-up display (HUD) system 11 to provide an image to a passenger 50 within a vehicle 10 includes, starting at block 102, projecting an image 58 onto an inner surface 62 of a windshield 64 of the vehicle 10 using a HUD projector 60, wherein the windshield 64 includes a coating 74 applied thereto that provides different wavelength-dependent reflectivity characteristics for different color components of the projected image 58, and moving to block 104, individually calibrating the polarization of each of the different color components of the projected image 58 using the HUD projector 60 to maintain consistent brightness and intensity characteristics within the image 58 reflected from the inner surface 62 of the windshield 64.

[0066] In an exemplary embodiment, projecting the image 58 onto the inner surface 62 of the windshield 64 of the vehicle 10 by the HUD projector 60 at block 102 further includes: moving to block 106, projecting the red component beam 70R onto the collimator 72 by the red laser 66R through the first spatial light modulator (SLM) 68R associated with the red laser 66R; moving to block 108, projecting the green component beam 70G onto the collimator 72 by the green laser 66G through the second SLM 68G associated with the green laser 66G; and moving to block 110, projecting the blue component beam 70B onto the collimator 72 by the blue laser 66B through the third SLM 68B associated with the blue laser 66B. The method 100 further includes moving to block 112 and collimating the red component beam 70R, the green component beam 70G, and the blue component beam 70B by the collimator 72 into the image 58 projected onto the inner surface 62 of the windshield 64.

[0067] In another exemplary embodiment, separately calibrating the polarization of each color component of the projected image 58 at block 104 by the HUD projector 60 to maintain consistent brightness and intensity characteristics in the image 58 reflected from the inner surface 62 of the windshield 64 further includes: separately calibrating the polarization of the red component beam 70R (moving to block 114), the green component beam 70G (moving to block 116), and the blue component beam 70B (moving to block 118) by the HUD projector 60 based on the reflectivity characteristics of the coating 74 on the windshield 64 such that each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is reflected from the inner surface 62 of the windshield 64 with substantially equal brightness and intensity.

[0068] In another exemplary embodiment, separately calibrating the polarization of each of the red component beam 70R (at block 114), the green component beam 70G (at block 116), and the blue component beam 70B (at block 118) by the HUD projector 60 based on the reflectivity characteristics of the coating 74 on the windshield 64 further includes: rotating each of the red laser 66R and the first SLM 68R, the green laser 66G and the second SLM 68G, and the blue laser 66B and the third SLM 68B relative to each other to separately calibrate the polarization of each of the red component beam 70B, the green component beam 70G, and the blue component beam 70B based on the wavelength-dependent reflectivity characteristics of the coating 74 on the windshield 64.

[0069] In another exemplary embodiment, based on the reflectivity characteristics of the coating 74 on the windshield 64, separately calibrating the polarization of each of the red component beam 70R (at block 114), the green component beam 70G (at block 116), and the blue component beam 70B (at block 118) using the HUD projector 60 further includes: using a first waveplate retarder 78R positioned between the first SLM 68R and the collimator 72 to calibrate the polarization of the red component beam 70R based on the wavelength-dependent reflectivity characteristics of the coating 74 on the windshield 64, using a second waveplate retarder 78G positioned between the second SLM 68G and the collimator 72 to calibrate the polarization of the green component beam 70G based on the wavelength-dependent reflectivity characteristics of the coating 74 on the windshield 64, and using a third waveplate retarder 78B positioned between the third SLM 68B and the collimator 72 to calibrate the polarization of the blue component beam 70B based on the wavelength-dependent reflectivity characteristics of the coating 74 on the windshield 64.

[0070] In another exemplary embodiment, the coating 74 on the windshield 64 is an infrared reflective (IRR) coating 74 that is coated on the windshield 64 and adapted to reflect external infrared light from the windshield 64, and the reflectivity of the red component beam 70R provided by the IRR coating 74 is less than the reflectivities of the green component beam 70G and the blue component beam 70B. Separately calibrating the polarization of each of the red component beam 70R (at block 114), the green component beam 70G (at block 116), and the blue component beam 70B (at block 118) using the HUD projector 60 based on the reflectivity characteristics of the coating 74 on the windshield 64 further includes: rotating the red laser 66R and the first SLM 68R relative to the green laser 66G and the second SLM 68G and the blue laser 66B and the third SLM 68B such that, based on the wavelength-dependent reflectivity characteristics of the coating 74 on the windshield 64, the red component beam 70R is projected onto the collimator 72 in a manner less than full P polarization.

[0071] In another exemplary embodiment, the coating 74 on the windshield 64 is an infrared reflection (IRR) coating 74 that is applied to the windshield 64 and adapted to reflect external infrared light from the windshield 64, and the reflectivity of the red component beam 70R provided by the IRR coating 74 is less than the reflectivities of the green component beam 70G and the blue component beam 70B. Based on the reflectivity characteristics of the coating 74 on the windshield 64, individually calibrating the polarization of each of the red component beam 70R (at block 114), the green component beam 70G (at block 116), and the blue component beam 70B (at block 118) using the HUD projector 60 further includes: using a wave plate retarder 78R positioned between the first SLM 68R and the collimator 72 to calibrate the red component beam 70R to be less than fully P polarized based on the wavelength-dependent reflectivity characteristics of the coating 74 on the windshield 64.

[0072] The description of the present disclosure is merely exemplary in nature, and variations that do not depart from the gist of the present disclosure are intended to fall within the scope of the present disclosure. Such variations should not be regarded as a departure from the spirit and scope of the present disclosure.

Claims

1. A head-up display (HUD) system for a vehicle, comprising: A vehicle windshield, which includes a coating applied thereto; And An HUD projector adapted to project an image onto the inner surface of the vehicle windshield; Wherein, the coating applied to the windshield provides different reflectivity characteristics for different color components of the projected image; and The HUD projector is adapted to individually calibrate the polarization of each of the different color components of the projected image to maintain consistent brightness and intensity characteristics within the image reflected from the inner surface of the windshield.

2. The HUD system according to claim 1, wherein, The HUD projector includes: A red laser and a first spatial light modulator (SLM) associated with the red laser, wherein the red laser is adapted to project a red component beam through the first SLM onto a collimator; A green laser and a second SLM associated with the green laser, wherein the green laser is adapted to project a green component beam through the second SLM onto the collimator; and A blue laser and a third SLM associated with the blue laser, wherein the blue laser is adapted to project a blue component beam through the third SLM onto the collimator; Wherein, the collimator is adapted to collimate the red component beam, the green component beam, and the blue component beam into the image projected onto the inner surface of the windshield.

3. The HUD system according to claim 2, wherein, The HUD projector is adapted to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the reflectivity characteristics of the coating on the windshield, such that each of the red component beam, the green component beam, and the blue component beam is reflected from the inner surface of the windshield with substantially equal brightness and intensity.

4. The HUD system according to claim 3, wherein, The reflectivity characteristics of the coating on the windshield are wavelength-dependent.

5. The HUD system according to claim 4, wherein, Each of the red laser and the first SLM, the green laser and the second SLM, and the blue laser and the third SLM is rotated relative to each other to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

6. The HUD system according to claim 4, further comprising: A first lens positioned between the first SLM and the collimator and adapted to calibrate the polarization of the red component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield; A second lens positioned between the second SLM and the collimator and adapted to calibrate the polarization of the green component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield; And A third lens positioned between the third SLM and the collimator and adapted to calibrate the polarization of the blue component beam based on the wavelength-dependent reflectivity characteristics of the coating on the windshield.

7. The HUD system according to claim 6, wherein, The first lens, the second lens, and the third lens are all waveplate retarders.

8. The HUD system according to claim 4, wherein, The coating on the windshield is an infrared reflection IRR coating that is coated on the windshield and adapted to reflect external infrared light from the windshield, and the reflectance of the red component beam provided by the IRR coating is less than the reflectances of the green component beam and the blue component beam.

9. The HUD system according to claim 8, wherein, The red laser and the first SLM are rotated relative to the green laser and the second SLM and the blue laser and the third SLM such that the red component beam is projected onto the collimator in a manner less than full P polarization based on the wavelength-dependent reflectance characteristics of the coating on the windshield.

10. The HUD system according to claim 8, further comprising a waveplate retarder positioned between the first SLM and the collimator and adapted to calibrate the polarization of the red component beam to less than full P polarization based on the wavelength-dependent reflectance characteristics of the coating on the windshield.

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