Maintaining color consistency in a head-up display system

Abstract

A head-up display (HUD) system for a vehicle includes a windshield of the vehicle having a coating applied thereto and a HUD projector configured to project an image onto an interior surface of the windshield of the vehicle, wherein the coating applied to the windshield provides different reflection properties for different color components of the projected image, and the HUD projector is configured to individually calibrate a polarization of each of the different color components of the projected image to maintain consistent brightness and intensity properties within the image reflected from the interior surface of the windshield.

Description

[0001] The present disclosure relates to a head-up display (HUD) system in a motor vehicle. Head-up displays have become common in modern automobiles. HUDs project useful information such as speed and navigation information into the driver's field of vision. This eliminates the need for the driver to look down to read the vehicle's dashboard. This reduces distraction and allows the driver to focus on the road.

[0002] Modern windshields are coated with various coatings that affect the reflectivity of the windshield and thus the brightness / intensity of the images projected by a HUD system, which are reflected from the windshield to the passengers' eyes. Coatings on a windshield can affect different colors of the projected image differently. For example, a windshield coating may provide lower reflectivity for a red component of the projected image compared to the blue and green components of the projected image, and therefore, red colors within the image reflected to the passenger will have less brightness or intensity.

[0003] DE 10 2016 111 119 A1 describes a laser projection arrangement and a method for generating virtual images. The aim is to provide a solution that enables the display of multiple virtual images at different distances or planes and at different viewing angles, and that is inexpensive to manufacture. For this purpose, an image generation unit generating at least two virtual images differing in their wavelength and / or polarization is arranged, and a holographic optical element is arranged on or in the projection surface.In the image generation unit, two virtual images with different wavelengths and / or different polarizations are generated, and a holographic optical element is provided which has different optical properties for different wavelengths and / or different polarizations, and when projecting the virtual images using the holographic optical element, the virtual images are displayed at different distances from the driver and / or at different viewing angles from the driver due to the different optical properties of the holographic optical element.

[0004] DE 11 2006 001 292 T5 describes an image projection arrangement for projecting an image, comprising: a) a scanner for sweeping a main laser beam along mutually orthogonal scanning directions to project a pattern of scan lines, each having a number of pixels; b) a control device operatively connected to the scanner for causing selected pixels to be illuminated and visualized to form the image; and c) an optical arrangement for generating a plurality of constituent laser beams having respective output powers and mutually orthogonal polarizations, and a polarization beam combiner for combining the constituent laser beams to form the main laser beam with an output power greater than each output power of the constituent laser beams to increase the brightness of the illuminated pixels.

[0005] DE 690 12 420 T2 describes a head-up display for a vehicle capable of reducing ghost images and enabling improved visibility during the day and at night. The head-up display comprises an image source for generating a beam containing image information, an optical combiner for partially reflecting the beam to create a virtual image of the image source visible to the vehicle's user, and a polarizer for insertion between the image source and the combiner. The display further comprises means for selectively inserting the polarizer between the image source and the combiner.

[0006] DE 20 2019 102 486 U1 describes a composite pane comprising an outer pane and an inner pane, which are connected to each other via a thermoplastic intermediate layer, comprising a transparent, electrically conductive coating and a luminescent layer.

[0007] While current systems serve their purpose, it is an object of the invention to provide a new and improved HUD system and method for providing a HUD image to a passenger in a vehicle, wherein the colors of the projected image have a uniform brightness / intensity as perceived by the passenger. Description

[0008] The invention is defined by the claims.

[0009] According to the invention, a head-up display (HUD) system for a vehicle comprises a windshield of a vehicle having a coating applied thereto and a HUD projector configured to project an image onto an interior surface of the windshield of the vehicle, wherein the coating applied to the windshield provides different reflection properties for different color components of the projected image, and the HUD projector is configured to individually calibrate a polarization of each of the different color components of the projected image to maintain consistent brightness and intensity properties within the image reflected from the interior surface of the windshield.

[0010] According to one embodiment, the HUD projector includes a red laser and a first spatial light modulator (SLM) associated with the red laser, the red laser configured 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, the green laser configured 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, the blue laser configured to project a blue component beam through the third SLM to the collimator, the collimator configured 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.

[0011] According to another embodiment, the HUD projector is configured to individually calibrate the polarization of each of the red component beam, the green component beam, and the blue component beam based on the reflective properties of the windshield coating 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.

[0012] According to a further embodiment, the reflection properties of the coating on the windshield are wavelength-dependent.

[0013] According to a further embodiment, 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 the red component beam, the green component beam, and the blue component beam based on the wavelength-dependent reflection properties of the windshield coating.

[0014] According to another embodiment, the system further comprises a first lens arranged between the first SLM and the collimator and capable of calibrating the polarization of the red component beam based on the wavelength-dependent reflection properties of the coating on the windshield, a second lens arranged between the second SLM and the collimator and capable of calibrating the polarization of the green component beam based on the wavelength-dependent reflection properties of the coating on the windshield, and a third lens arranged between the third SLM and the collimator and capable of calibrating the polarization of the blue component beam based on the wavelength-dependent reflection properties of the coating on the windshield.

[0015] According to a further embodiment, the first lens, the second lens and the third lens are each a waveplate retarder.

[0016] According to another embodiment, the coating on the windshield is an infrared reflective (IRR) coating applied to the windshield and configured to reflect external infrared light away from the windshield, the IRR coating providing a reflectivity of the red component beam that is less than the reflectivity of the green component beam and the blue component beam.

[0017] According to another embodiment, the red laser and the first SLM are rotated relative to the green laser and the second SLM and to the blue laser and the third SLM such that the red component beam is projected to the collimator with less than full P-polarization based on the wavelength-dependent reflection properties of the coating on the windshield.

[0018] According to another embodiment, the system further includes a waveplate retarder disposed between the first SLM and the collimator, capable of calibrating the polarization of the red component beam to less than full P-polarization based on the wavelength-dependent reflection properties of the coating on the windshield.

[0019] According to several aspects of the present description, a method for providing images to a passenger in a vehicle using a head-up display (HUD) system includes projecting an image with a HUD projector onto an interior surface of a windshield of the vehicle, the windshield including a coating applied thereto that provides different wavelength-dependent reflectance properties for different color components of the projected image, and individually calibrating, with the HUD projector, a 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 interior surface of the windshield.

[0020] According to another aspect, projecting the image onto the inner surface of the windshield of the vehicle with the HUD projector further comprises projecting a red component beam from a red laser onto a collimator through a first spatial light modulator (SLM) associated with the red laser, projecting a green component beam from a green laser onto the collimator through a second SLM associated with the green laser, projecting a blue laser beam onto the collimator through a third SLM associated with the blue laser, and the method further comprises collimating the red component beam, the green component beam, and the blue component beam with the collimator into the image projected onto the inner surface of the windshield.

[0021] According to another aspect, individually calibrating the polarization of each of the different color components of the projected image with the HUD projector to maintain consistent brightness and intensity characteristics within the image reflected from the interior surface of the windshield further comprises individually calibrating the polarization of each of the red component beam, the green component beam, and the blue component beam with the HUD projector based on the reflective properties 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 interior surface of the windshield with substantially equal brightness and intensity.

[0022] According to another aspect, individually calibrating, with the HUD projector, the polarization of each of the red component beam, the green component beam, and the blue component beam based on the reflective properties of the coating on the windshield further comprises rotating 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 reflective properties of the coating on the windshield.

[0023] According to a further aspect, individually calibrating the polarization of the red component beam, the green component beam, and the blue component beam with the HUD projector based on the reflection properties of the coating on the windshield further comprises calibrating the polarization of the red component beam based on the wavelength-dependent reflection properties of the coating on the windshield with a first waveplate retarder arranged between the first SLM and the collimator, calibrating the polarization of the green component beam based on the wavelength-dependent reflection properties of the coating on the windshield with a second waveplate retarder arranged between the second SLM and the collimator,and calibrating the polarization of the blue component beam based on the wavelength-dependent reflection properties of the coating on the windshield with a third waveplate retarder disposed between the third SLM and the collimator.

[0024] According to another aspect, the coating on the windshield is an infrared reflective (IRR) coating applied to the windshield and configured to reflect external infrared light away from the windshield, wherein the IRR coating provides a reflectivity of the red component beam that is less than the reflectivity of the green component beam and the blue component beam, and individually calibrating, with the HUD projector, the polarization of each of the red component beam, the green component beam, and the blue component beam based on the reflective properties of the coating on the windshield, further comprises 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,so that the red component beam is projected onto the collimator with less than full P-polarization based on the wavelength-dependent reflection properties of the coating on the windshield.

[0025] According to another aspect, the coating on the windshield is an infrared reflective coating (IRR coating) applied to the windshield and configured to reflect external infrared light away from the windshield, wherein the IRR coating provides a reflectivity of the red component beam that is less than the reflectivity of the green component beam and the blue component beam, and individually calibrating the polarization of each of the red component beam, the green component beam, and the blue component beam with the HUD projector based on the reflective properties of the coating on the windshield,further comprises calibrating the polarization of the red component beam to less than full P-polarization based on the wavelength-dependent reflection properties of the coating on the windshield with a waveplate retarder disposed between the first SLM and the collimator.

[0026] According to several aspects of the present disclosure, a vehicle with a head-up display (HUD) system includes a windshield of the vehicle having a coating applied thereto, a HUD projector configured to project an image onto an interior surface of the windshield of the vehicle, the HUD projector including a red laser and a first spatial light modulator (SLM) associated with the red laser, the red laser configured 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, the green laser 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, the blue laser adapted tothat it projects a blue component beam through the third SLM to the collimator, wherein the collimator is configured 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, wherein the coating applied to the windshield is an infrared reflective (IRR) coating capable of reflecting external infrared light away from the windshield, wherein the IRR coating provides a wavelength-dependent reflectivity for the red component beam that is lower than the reflectivity for the green component beam and the blue component beam, and the HUD projector is configured to individually polarize each of the red component beams,of the green component beam and the blue component beam based on the reflection properties of the coating on the windshield so 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.

[0027] 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 is rotated relative to each other to individually calibrate the polarization of the red component beam, the green component beam, and the blue component beam based on the wavelength-dependent reflection properties of the windshield coating.

[0028] According to another aspect, the vehicle further comprises a first waveplate retarder disposed between the first SLM and the collimator and configured to calibrate the polarization of the red component beam based on the wavelength-dependent reflection properties of the coating on the windshield, a second waveplate retarder disposed between the second SLM and the collimator and configured to calibrate the polarization of the green component beam based on the wavelength-dependent reflection properties of the coating on the windshield, and a third waveplate retarder disposed between the third SLM and the collimator and configured to calibrate the polarization of the blue component beam based on the wavelength-dependent reflection properties of the coating on the windshield.

[0029] Further areas of applicability will become apparent from the present description. It should be understood that the description and specific examples are for illustrative purposes only and are not intended to limit the scope of the present disclosure. Brief description of the drawings

[0030] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of this description in any way. Fig. 1 is a schematic diagram of a vehicle according to an exemplary embodiment of the present description; Fig. 2 is a schematic diagram of the HUD system of the present description according to an exemplary embodiment; Fig. 3 is a schematic view of the HUD system, a windshield of a vehicle, and a passenger in the vehicle; Fig. Figure 4 is a schematic view of the HUD system, where the polarization of component beams is achieved by rotating a laser / SLM for each component beam; Fig. Figure 5 is a schematic view of the HUD system, where the polarization of the component beams is performed by lenses arranged between each laser / SLM and a collimator; and Fig. 6 is a schematic flow diagram illustrating a method according to an exemplary embodiment of the present description.

[0031] The illustrations are not necessarily to scale, and some features may be exaggerated or reduced in size, for example, to show details of particular components. In some cases, well-known components, systems, materials, or methods have not been described in detail in order not to obscure the present description. Therefore, specific structural and functional details disclosed herein are not to be construed as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art how to variously employ the present disclosure. Detailed description

[0032] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description. It should be understood that throughout the drawings, corresponding reference characters designate like or corresponding parts and features.As used herein, the term module refers to any hardware, software, firmware, electronic control component, processing logic, and / or processor device, individually or in any combination, including, without limitation, an application-specific integrated circuit (ASIC), an electronic circuit, a processor (common, dedicated, or group) and memory executing one or more software or firmware programs, a combined logic circuit, and / or other suitable components that provide the described functionality. Although the figures shown herein represent an example with particular arrangements of elements, in actual embodiments, additional intervening elements, devices, features, or components may be present. It should also be understood that the figures are illustrative only and are not drawn to scale.

[0033] As used herein, the term "vehicle" is not limited to motor vehicles. While the present technology is primarily described in the context of motor vehicles, it is not limited to motor vehicles. The concepts may be used in a wide variety of applications, including aircraft, watercraft, other vehicles, and consumer electronic components.

[0034] According to an exemplary embodiment, Fig. 1 shows a vehicle 10 with an associated head-up display (HUD) system 11 for generating an image for a passenger within the vehicle 10 in accordance with various embodiments. In general, the head-up display system 11 cooperates with other systems within the vehicle 10 to display various information and infotainment content for the passenger. 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 encloses the components of the vehicle 10. The body 14 and the chassis 12 together may form a frame. The front wheels 16 and the rear wheels 18 are each rotatably connected to the chassis 12 near a corner of the body 14.

[0035] In various embodiments, the vehicle 10 is an autonomous vehicle, and the head-up display system 11 is installed in the autonomous vehicle 10 (hereinafter referred to as autonomous vehicle 10). The autonomous vehicle 10 is, for example, a vehicle that is automatically controlled to transport passengers from one location to another. The autonomous vehicle 10 is depicted as a passenger car in the illustrated embodiment, but it should be understood that any other vehicle, including motorcycles, trucks, sport utility vehicles (SUVs), recreational vehicles (RVs), etc., may also be used. In an exemplary embodiment, the autonomous vehicle 10 is a so-called level four or five automation system. A level four system represents a high degree of automation, i.e.An automated driving system performs all aspects of the dynamic driving task, even if a human driver does not respond appropriately to a request for intervention. A Level 5 system represents "full automation," meaning an automated driving system fully performs all aspects of the dynamic driving task under all road and environmental conditions that a human driver can handle.

[0036] As illustrated, the autonomous vehicle 10 generally includes a propulsion system 20, a transmission system 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 an embodiment where the autonomous vehicle 10 is an electric vehicle, a transmission system 22 may not be present. The propulsion system 20, in various embodiments, may include an internal combustion engine, an electric machine such as a traction motor, and / or a fuel cell propulsion system. The transmission system 22 is configured to transfer the power of the propulsion system 20 to the front wheels 16 and the rear wheels 18 of the vehicle according to selectable gear ratios. According to various embodiments, the transmission system 22 may include a continuously variable automatic transmission, a continuously variable transmission, or other suitable transmission.The braking system 26 is configured to apply braking torque to the front wheels 16 and the rear wheels 18 of the vehicle. In various embodiments, the braking system 26 may include friction brakes, brake-by-wire systems, a regenerative braking system such as an electric machine, and / or other suitable braking systems. The steering system 24 influences the position of the front wheels 16 and the rear wheels 18. Although a steering wheel is shown for illustrative purposes, the steering system 24 may not include a steering wheel in some embodiments contemplated by the present description.

[0037] 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 may include, but are not limited to, radars, lidars, global positioning systems, optical cameras, thermal imaging cameras, ultrasonic sensors, and / or other sensors. The cameras may include two or more digital cameras spaced apart from each other, with the two or more digital cameras used to obtain stereoscopic images of the environment to create a three-dimensional image. The sensing devices 40a-40n may include sensors that monitor dynamic variables of the vehicle, such as its speed, acceleration, the number of brake applications, etc.The actuator system 30 includes one or more actuator devices 42a-42n that control one or more features of the vehicle 10, such as, but not limited to, the drive system 20, the transmission system 22, the steering system 24, and the braking system 26.

[0038] The controller 34 for the vehicle includes at least one processor 44 and a computer-readable storage device or medium 46. The at least one data processor 44 may be any custom or off-the-shelf processor, a central processing unit (CPU), a graphics processing unit (GPU), an auxiliary processor among a plurality of processors associated with the controller 34, a semiconductor-based microprocessor (in the form of a microchip or chipset), a macroprocessor, any combination thereof, or generally any device for executing instructions. The computer-readable storage devices or media 46 may include volatile and non-volatile memory, 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 while the at least one data processor 44 is powered off. The computer-readable storage devices or media 46 can be implemented using any number of known storage devices such as PROMs (Programmable Read-Only Memory), EPROMs (Electrically Erasable PROMs), EEPROMs (Electrically Erasable PROMs), flash memory, or other electrical, magnetic, optical, or combination storage devices capable of storing data, some of which represent executable instructions used by the controller 34 in controlling the vehicle 10.

[0039] The instructions may comprise one or more separate programs, each containing an ordered list of executable instructions for implementing logical functions. The instructions, when executed by the at least one processor 44, receive and process signals from the sensor system 28, perform logic, calculations, methods, and / or algorithms to automatically control the components of the autonomous vehicle 10, and generate control signals for the actuator system 30 to automatically control the components of the autonomous vehicle 10 based on the logic, calculations, methods, and / or algorithms. Although in Fig. 1 only one controller 34 is shown, embodiments of the autonomous vehicle 10 may include any number of controllers 34 that communicate via any suitable communication medium or combination of communication media and that cooperate to process the sensor signals, perform logic, calculations, methods and / or algorithms, and generate control signals to automatically control features of the autonomous vehicle 10.

[0040] In various embodiments, one or more instructions of controller 34 are included in a trajectory planning system and, when executed by at least one data processor 44, generate a trajectory output that accounts for kinematic and dynamic constraints of the environment. For example, the instructions receive process sensor and map data as input. The instructions execute a graph-based approach with an adapted cost function to handle various road scenarios, both urban and highway.

[0041] The communication system 36 is configured to wirelessly communicate information to and from other remote entities 48, such as 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 over a wireless local area network (WLAN) using IEEE 802.11 standards or using cellular data communication. However, additional or alternative communication methods, such as a dedicated short-range communication channel (DSRC), are also contemplated within the scope of this description.DSRC channels refer to short- to medium-range, one-way or two-way wireless communication channels specifically designed for automotive use, along with a set of protocols and standards.

[0042] As in Fig. As shown in Figure 2, the HUD system 11 includes a passenger monitoring system 52 with a camera 54 that can monitor the head and eye position of the passenger 50. A passenger monitoring system 52, often referred to as a driver monitoring system or DMS, is an artificial intelligence (AI)-based vehicle safety technology that monitors the alertness of the passenger 50 via the camera 54. The purpose of the passenger monitoring system 52 is to identify the passenger and detect their level of alertness using software and to warn in case of drowsiness, distraction, etc., in order to avoid accidents. The main functions of the DMS are driver identification, distraction detection, fatigue detection, specific activity detection, eye blink detection, emotion detection, and gaze tracking.In the context of the HUD system 11 of the present description, the primary purpose of the driver monitoring system 52 is to monitor the position of the eyes and head of the passenger 50, as well as the direction of gaze of the passenger 50, in order to determine the images to be displayed by the HUD system and their placement.

[0043] The HUD system 11 further includes a computing unit 56 that communicates with a system controller 34A and the passenger monitoring system 52. The system controller 34A may be the vehicle's controller 34 or a separate controller associated with the vehicle's controller and configured to support communication between the HUD system 11 and other systems within the vehicle 10 and to receive data from sensors 40a-40n within the vehicle 10. The computing unit 56 is configured to calculate an image 58 and encode the image 58 to a HUD projector 60. The HUD projector 60 may be any display suitable for projecting holographic images.

[0044] With reference to Fig. 3, the HUD projector 60 of the head-up system 11 is configured to project an image 58 onto an interior surface 62 of a 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 configured 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, the green laser 66G being configured to project a green component beam 70G through the second SLM 68G onto the collimator 72, and finally, a blue laser 66B and a third SLM 68B associated with the blue laser 66B, the blue laser 66B being configured to project a blue component beam 70B through the third SLM 68B onto the collimator 72. The collimator 72 is configured 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 interior surface 62 of the windshield 64.

[0045] The first SLM 68R is irradiated with light from the red laser 66R, and the first SLM 68R diffracts the red laser light with an encoded hologram. Upon irradiation, each pixel of the first SLM 68R generates a wavefront with a phase corresponding to the phase of the position of the hologram encoded at that pixel. The diffracted red laser light with the encoded hologram (the red component beam 70R) then propagates to the collimator 72. The second SLM 68G is irradiated with light from the green laser 66G, and the second SLM 68G diffracts the green laser light with an encoded hologram. Upon irradiation, each pixel of the second SLM 68G generates a wavefront with a phase corresponding to the phase of the position of the hologram encoded at that pixel. The diffracted green laser light with the hologram encoded therein (the green component beam 70R) then propagates to the collimator 72.The third SLM 68B is irradiated with light from the blue laser 66B, and the third SLM 68B diffracts the blue laser light with an encoded hologram. Upon irradiation, each pixel of the third SLM 68B generates a wavefront with a phase corresponding to the phase of the position of the hologram encoded at that pixel. The diffracted blue laser light with the encoded hologram (the blue component beam 70R) then propagates to the collimator 72.

[0046] The windshield 64 of the vehicle is provided with a coating 74. The coating 74 may be a polymer or ceramic coating that is either sprayed or applied to the interior or exterior surface of the windshield 64 and dried or cured. The coating 74 may also be a solid layer or film of a polymer or glass material that is applied to either the interior or exterior surface of the windshield 64. The coating 74 is applied to the windshield 64 to provide beneficial properties to the passenger 50 in the vehicle 10. For example, the coating 74 may tint the windshield 64 or provide glare protection.

[0047] Such coatings provide different reflection properties for different color components of the projected image 58. In particular, the coating 74 provides different reflectivity of a light beam based on the wavelength and thus the color of the light beam. Therefore, the coating 74 provides different reflectivity for the red component beam 70R, the green component beam 70G, and the blue component beam 70B of the image 58. This means that the brightness and intensity of a particular light beam may be reduced due to the lower reflectivity of the coating 74.

[0048] In an exemplary embodiment, the coating 74 is an infrared reflective (IRR) coating applied to the windshield 64 and is adapted to reflect external infrared light away from the windshield 64. The IRR coating 74 provides a reflectivity of the red component beam 70R that is less than the reflectivity of the green component beam 70G and the blue component beam 70B. Thus, when the image 50 is reflected from the interior surface 62 of the windshield 64 toward the eyes of the passenger 50, the reflection of the red component beam 70R is less efficient than the reflection of the green component beam 70G and the blue component beam 70B. Therefore, the red aspects of the projected image 58, when viewed by the passenger 50, appear less bright and less intense than the green and blue aspects.

[0049] The HUD projector 60 is configured to individually calibrate a polarization of the various color components of the projected image 58 to ensure consistent brightness and intensity within the image 58 when the image 58 is reflected from the interior surface 62 of the windshield 64. Thus, the HUD projector 60 is capable of individually calibrating the polarization of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B based on the reflective properties 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 interior surface 62 of the windshield 64 with substantially equal brightness and intensity.

[0050] The red component beam 70R is projected by the red laser 66R and through the first SLM 68R with full P-polarization. Similarly, the green component beam 70G is projected by the green laser 66G and through the second SLM 68G with full P-polarization, and the blue component beam 70B is projected by the blue laser 66B and through the third SLM 68B with full P-polarization. Light is an electromagnetic wave, and the electric field of this wave oscillates perpendicular to the direction of propagation. Light is said to be unpolarized if the direction of this electric field fluctuates randomly over time. Many common light sources such as sunlight, halogen lamps, LED spotlights, and incandescent bulbs produce unpolarized light. If the direction of the light's electric field is precisely defined, it is called polarized light.The two orthogonal linear polarization states that are most important for reflection and transmission are called P-polarization and S-polarization. In P-polarized light, the electric field is polarized parallel to the plane of incidence, while in S-polarized light, the electric field is perpendicular to this plane.

[0051] Coating 74 enables a wavelength-dependent variation in the reflectivity of P-polarized light. The polarization of light is measured in degrees, with fully S-polarized light being zero degrees (0°) and fully P-polarized light being ninety degrees (90°). In the example described above, the IRR coating reduces the reflectivity of fully P-polarized red light, thereby negatively affecting the brightness and intensity of the red component beam 70R.

[0052] In order for the HUD projector 60 to individually calibrate the polarization of each of the different color components of the projected image 58, 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 full P-polarization (90°) and toward a stronger S-polarization (0°). 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°.By adjusting the polarization of the red component beam 70R, the reduction in reflectivity caused by the coating 74 is reduced, so that the red component beam 70R is reflected from the inner surface 62 of the windshield 64 with a brightness and intensity substantially equal to that of the green component beam 70G and the blue component beam 70B.

[0053] As with reference to Fig. 4, in an exemplary embodiment, 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 are rotated relative to one another to individually calibrate the polarization of the red component beam 70R, the green component beam 70G, and the blue component beam 70B. The calibration of the polarization of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is based on the wavelength-dependent reflectance properties of the coating 74 on the windshield 64 and how the coating 74 specifically affects the reflectance for the red component beam 70R, the green component beam 70G, and the blue component beam 70B.

[0054] In the above example, the IRR coating does not adversely 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 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 indicated by arrow 76, to calibrate the polarization of the red component beam 70R alone to 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.

[0055] Alternatively, the red laser 66R and the first SLM 68R may be rotated along with the rotation 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 are calibrated to reduce the negative effects of the coating 74 on the relativity of the red component beam 70R, the green component beam 70G, and the blue component beam 70B. The amount of rotation 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 individually based on the relative effects of the coating 74 on the reflectivity of each.In this way, the polarization of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is calibrated to both improve the overall brightness / intensity of the red component beam 70R, the green component beam 70G, and the blue component beam 70B and to ensure that the reflectivity and brightness / intensity of the red, green, and blue component beams 70R, 70G, 70B are uniform.

[0056] With reference to Fig. 5, in another exemplary embodiment, the HUD system 11 includes a first lens 78R disposed between the first SLM 68R and the collimator 72 and operable to calibrate the polarization of the red component beam 70R based on the wavelength-dependent reflective properties of the coating 74 on the windshield 64 as the red component beam 70R passes through the first lens 78R. A second lens 78G is disposed between the second SLM 68G and the collimator 72 and operable to calibrate the polarization of the green component beam 70G based on the wavelength-dependent reflective properties of the coating 74 as the green component beam 70G passes through the second lens 78G.A third lens 78B is arranged between the third SLM 68B and the collimator 72 and serves to calibrate the polarization of the blue component beam 70B based on the wavelength-dependent reflection properties of the coating 74.

[0057] In one example, the first lens 78R calibrates only the polarization of the red component beam 70R to less than full P polarization, so 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.

[0058] In another example, the first lens 78R, the second lens 78G, and the third lens 78B simultaneously calibrate the polarization of the red component beam 70B, the green component beam 70G, and the blue component beam 70B to reduce the negative effects of the coating 74 on the reflectivity of the red component beam 70R, the green component beam 70G, and the blue component beam 70B. The extent of calibration of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is individually calculated based on the relative effects of the coating 74 on their respective reflectivity.In this way, the polarization of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B is calibrated to both improve the overall brightness / intensity of each of the red component beam 70R, the green component beam 70G, and the blue component beam 70B and to ensure that the reflectivity and brightness / intensity of the red, green, and blue component beams 70R, 70G, 70B are uniform.

[0059] In an exemplary embodiment, the first lens 78R, the second lens 78G, and the third lens 78B are each a waveplate retarder. Waveplate retarders transmit light and change its polarization state without attenuating, deflecting, or shifting the beam. They do this by delaying (or slowing down) a polarization component relative to its orthogonal component. Each waveplate retarder 78R, 78G, 78B is an optical device that changes the polarization state of a light wave passing through it. Birefringent polarizers rely on the dependence of the refractive index on the polarization of light. Different polarizations are refracted at different angles, which can be used to select specific polarizations of light.In an exemplary embodiment, each lens (waveplate retarder) 78R, 78G, 78B is a birefringent polarizer capable of adjusting the ratio of S-polarization to P-polarization in the red, green, and blue components of the beams 70R, 70G, 70B projected therethrough.

[0060] In another exemplary embodiment, each lens / waveplate retarder 78R, 78G, 78B includes a retarding layer with an inorganic birefringent film. The inorganic birefringent film may include columnar nanostructures formed on the lens / waveplate retarder 78R, 78G, 78B by oblique deposition. The columnar structure of inorganic material formed on the lens / waveplate retarder 78R, 78G, 78B defines a birefringent film that retards the propagation of the light beam through the retarding layer, resulting in an adjustment of the ratio of S-polarization and P-polarization of the component beam 70R, 70G, 70B exiting the lens / waveplate retarder 78R, 78G, 78B.

[0061] By controlling the thickness and angular orientation of the columnar nanostructures, the ratio of S-polarization and P-polarization of the red component beam 70R, the green component beam 70G, and the blue component beam 70B projected by the first, second, and third lens / waveplate retarders 78R, 78G, 78B can be adjusted for a particular application (reducing the P-polarization), taking into account the relative negative effects of the coating 74 on the reflectivity of the red, green, and blue component beams 70R, 70G, 70B.

[0062] In one exemplary embodiment, the inorganic birefringent film is grown directly on the lens / waveplate retarder 78R, 78G, 78B. In another exemplary embodiment, the inorganic birefringent film is formed separately and then laminated to the lens / waveplate retarder 78R, 78G, 78B.

[0063] 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 birefringent properties of the liquid crystal lens vary as the voltage applied to the liquid crystal lens is varied. The birefringent properties of the liquid crystal lens are manipulated by changing the alignment of the liquid crystal molecules within the liquid crystal lens as the voltage applied to the liquid crystal lens is changed.

[0064] With reference to Fig.6, a method 100 for providing images to a passenger 50 in a vehicle 10 using a head-up display (HUD) system 11 includes, beginning with block 102, projecting an image 58 with a HUD projector 60 onto an interior surface 62 of a windshield 64 of the vehicle 10, the windshield 64 including a coating 74 applied thereto that provides different wavelength-dependent reflectance characteristics for different color components of the projected image 58, and, moving to block 104, individually calibrating, with the HUD projector 60, a polarization of each of the different color components of the projected image 58 to maintain consistent brightness and intensity characteristics within the image 58 reflected from the interior surface 62 of the windshield 64.

[0065] In an exemplary embodiment, projecting the image 58 with the HUD projector 60 onto the interior surface 62 of the windshield 64 of the vehicle 10 in block 102 further comprises projecting a red component beam 70R with a red laser 66R through a first spatial light modulator (SLM) 68R associated with the red laser 66R to a collimator 72, proceeding to block 108, a green component beam 70G with a green laser 66G through a second SLM 68G associated with the green laser 66G to the collimator 72, and proceeding to block 110, a blue component beam 70B with a blue laser 66B through a third SLM 68B associated with the blue laser 66B to the collimator 72.The method 100 further includes, continuing to block 112, collimating the red component beam 70R, the green component beam 70G, and the blue component beam 70B with the collimator 72 into the image 58 projected onto the inner surface 62 of the windshield 64.

[0066] In another exemplary embodiment, individually calibrating the polarization of each of the various color components of the projected image 58 with 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 in block 104 further comprises individually calibrating, with the HUD projector 60, the polarization of each, proceeding to block 114, of the red component beam 70R, proceeding to block 116, of the green component beam 70G, and proceeding to block 118, of the blue component beam 70B based on the reflective properties 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 reflects from the inner surface 62 of the windshield 64 with substantially equal brightness and intensity. becomes.

[0067] In another exemplary embodiment, individually calibrating, with the HUD projector 60, the polarization of each of the red component beam 70R in block 114, the green component beam 70G in block 116, and the blue component beam 70B in block 118 based on the reflective properties of the coating 74 on the windshield 64, further comprises rotating each of the red laser 66R and the first SLM 68R, rotating 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 one another to individually calibrate the polarization of the red component beam 70B, the green component beam 70G, and the blue component beam 70B based on the wavelength-dependent reflective properties of the coating 74 on the windshield 64. to calibrate.

[0068] In another exemplary embodiment, individually calibrating, with the HUD projector 60, the polarization of each of the red component beam 70R in block 114, the green component beam 70G in block 116, and the blue component beam 70B in block 118 based on the reflective properties of the coating 74 on the windshield 64, wherein the polarization of the red component beam 70R is calibrated based on the wavelength-dependent reflective properties of the coating 74 on the windshield 64 with a first waveplate retarder 78R disposed between the first SLM 68R and the collimator 72, calibrating the polarization of the green component beam 70G based on the wavelength-dependent reflective properties of the coating 74 on the windshield 64 with a second waveplate retarder 78G disposed between the second SLM 68G and the collimator 72,and calibrating the polarization of the blue component beam 70B based on the wavelength-dependent reflection properties of the coating 74 on the windshield 64 with a third waveplate retarder 78B disposed between the third SLM 68B and the collimator 72.

[0069] In another exemplary embodiment, the coating 74 on the windshield 64 is an infrared reflective (IRR) coating 74 applied to the windshield 64 and configured to reflect external infrared light away from the windshield 64, wherein the IRR coating 74 provides a reflectivity of the red component beam 70R that is less than the reflectivity of the green component beam 70G and the blue component beam 70B, and individually calibrating with the HUD projector 60 the polarization of each of the red component beams 70R in block 114,of the green component beam 70G in block 116 and the blue component beam 70B in block 118 based on the reflective properties of the coating 74 on the windshield 64 further comprises 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 the red component beam 70R is projected onto the collimator 72 with less than full P-polarization based on the wavelength-dependent reflective properties 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 applied to the windshield 64 and configured to reflect external infrared light away from the windshield 64, wherein the IRR coating 74 provides a reflectivity of the red component beam 70R that is less than the reflectivity of the green component beam 70G and the blue component beam 70B, and individually calibrating the polarization of each of the red component beam 70R with the HUD projector 60, in block 114, the green component beam 70G in block 116, and the blue component beam 70B in block 118 based on the reflective properties of the coating 74 on the windshield 64, further comprises calibrating the polarization of the red component beam 70R with a waveplate retarder 78R,disposed between the first SLM 68R and the collimator 72, to less than full P-polarization based on the wavelength-dependent reflection properties of the coating 74 on the windshield 64.

Claims

[1] Head-up display system (11), HUD system (11), for a vehicle (10), comprising: a windshield (64) of the vehicle (10) having a coating (74) applied thereto; and a head-up display projector (60), HUD projector (60) configured to project an image (58) onto an interior surface (62) of the windshield (64) of the vehicle (10); wherein the coating (74) applied to the windshield (64) provides different reflection properties for different color components of the projected image (58); and wherein the HUD projector (60) is configured to individually calibrate a polarization of each of the different color components of the projected image (58) to maintain consistent brightness and intensity characteristics within the image (58) reflected from the inner surface (62) of the windshield (64). [2] HUD system (11) according to claim 1, wherein the HUD projector (60) comprises: a red laser (66R) and a first spatial light modulator (68R), SLM (68R) associated with the red laser (66R), the red laser (66R) being configured to project a red component beam (70R) through the first SLM (68R) onto a collimator (72); a green laser (66G) and a second SLM (68G) associated with the green laser (66G), the green laser (66G) being configured to project a green component beam (70G) through the second SLM (68G) onto the collimator (72); and a blue laser (66B) and a third SLM (68B) associated with the blue laser (66B), the blue laser (66B) configured to project a blue component beam (70B) through the third SLM (68B) onto the collimator (72); wherein the collimator (72) is configured 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). [3] The HUD system (11) of claim 2, wherein the HUD projector (60) is configured 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 different reflective properties of the coating (74) of 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. [4] HUD system (11) according to claim 3, wherein the different reflection properties of the coating (74) on the windshield (64) are wavelength dependent. [5] The HUD system (11) of claim 4, wherein 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) are rotated relative to each other to individually calibrate the polarization of the red component beam (70R), the green component beam (70G), and the blue component beam (70B) based on the wavelength-dependent different reflection properties of the coating (74) of the windshield (64). [6] HUD system (11) according to claim 4, further comprising: a first lens (78R) disposed between the first SLM (68R) and the collimator (72) and configured to calibrate the polarization of the red component beam (70R) based on the wavelength-dependent different reflection properties of the coating (74) on the windshield (64); a second lens (78G) disposed between the second SLM (68G) and the collimator (72) and configured to calibrate the polarization of the green component beam (70G) based on the wavelength-dependent different reflection properties of the coating (74) on the windshield (64); and a third lens (78B) disposed between the third SLM (68B) and the collimator (72) and configured to calibrate the polarization of the blue component beam (70B) based on the wavelength-dependent different reflection properties of the coating (74) on the windshield (64). [7] The HUD system (11) of claim 6, wherein each of the first lens (78R), the second lens (78G), and the third lens (78B) is a waveplate retarder. [8] The HUD system (11) of claim 4, wherein the coating (74) on the windshield (64) is an infrared reflective coating, IRR coating, applied to the windshield (64) and configured to reflect external infrared light away from the windshield (64), the IRR coating (74) providing a reflectivity of the red component beam (70R) that is less than the reflectivity of the green component beam (70G) and the blue component beam (70B). [9] The HUD system (11) of claim 8, wherein the red laser (66R) and the first SLM (68R) are rotated relative to the green laser (66G) and the second SLM (68G) and to the blue laser (66B) and the third SLM (68B) such that the red component beam (70R) is projected onto the collimator (72) with less than full P-polarization based on the wavelength dependence of the coating (74) of the windshield (64). [10] The HUD system (11) of claim 8, further including a waveplate retarder disposed between the first SLM (68R) and the collimator (72) and configured to calibrate the polarization of the red component beam (70R) to less than full P-polarization based on the wavelength-dependent different reflective properties of the coating (74) and different reflective properties of the windshield (64).

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