Vehicle display systems and methods with holographic multifunction RLAD devices

Abstract

The holographic projection display system comprises a group of illumination elements arranged in a fixed lighting array. The grouped illumination elements include a first set of light-emitting diodes (LEDs) emitting light at a first wavelength, each with a specific emission angle towards a reflecting surface, and a second set of LEDs emitting light at a second wavelength, each with a specific emission angle towards the reflecting surface. A multilayer holographic optical element (HOE) array is mounted on the illumination group in front of the two sets of LEDs.The multi-layered HOE arrangement comprises a stacked pair of mutually parallel holographic plates, comprising a first holographic plate recorded with multiple holographic patterns, each optically configured to diffract the wavelength of light emitted by the first light-emitting diodes, and a second holographic plate recorded with multiple holographic patterns, each optically configured to diffract the wavelength of light emitted by the second light-emitting diodes.

Description

The present disclosure relates generally to display systems for motor vehicles. More particularly, aspects of this disclosure relate to digital projection display devices for presenting vehicle information and driving warnings to occupants of motor vehicles.Most current production automobiles, such as the modern automobile, are constructed with a rigid vehicle body, either as a body-to-frame or single body construction, having a passenger compartment for seating and securing the occupants of the vehicle. A windshield (or "windshield" in some countries) is mounted between the front A-pillars of the vehicle body that prevents the unwanted ingress of wind, rain, and debris while providing an aerodynamically shaped window through which the driver views the roadway. Under the windshield and in front of the driver's seat is an instrument panel of the dashboard (colloquially the "instrument cluster" or "IP") that contains an assortment of digital and electromechanical dials, gauges, gauges, and indicators for forwarding information about the vehicle to the driver. A vehicle telecommunications and information ("telematics") unit may be deployed into the dashboard center pillar portion to provide occupants with an on-board computing device that provides a mix of services including feedback and control for various in-vehicle subsystems.To increase driver awareness for vehicle system operation and environmental driving conditions, some modern vehicles supplement the telematics unit and IP with a head-up display (HUD) device with a transparent display panel ("see-through") that displays information within the viewing area of the windshield. An automotive HUD is configured to present information within the field of view of the driver when driving forward, thus reducing unnecessary eye scanning and gaze behavior at the instrument panel and the center pillar. Due to the inherent cost and complexity of integrating a separate transparent display panel of an HUD, some vehicles instead use a reflected light emitting diode (LED) warning display (RLAD) to present warnings and notifications to drivers by projecting source LED light onto an interior surface of the vehicle windshield. However, current RLAD systems are typically capable of projecting only basic geometric shapes in fixed colors and are thus limited in the types of information that can be displayed to the driver.DE 10 2016 117 969 A1 shows a lighting device for a vehicle, comprising a hologram and a light source for illuminating the hologram, wherein the hologram is configured to generate an image in response to the illumination, wherein the hologram comprises a plurality of individual holograms, such that the image comprises a plurality of individual images having different spatial alignments, or wherein the hologram is configured to generate the image with a curved shape, wherein the plurality of individual holograms or the curved shape is configured to enable the image to be viewed in a plane from an angle range greater than 30°.DE 699 12 759 T2 relates to holographic optical components and more particularly to components containing a plurality of holographic optical elements (HOEs) supported on a conventional light transmissive substrate.DE 10 2015 104 085 A1 discloses an imaging device comprising a plurality of light-giving elements arranged in a first direction along a line for generating a plurality of modulatable light beams, a deflection device for adjustably deflecting the light beams in a second direction, wherein the second direction differs from the first direction, and an optical arrangement for collimating the light beams in the second direction, wherein at least one element of the optical arrangement serves as the deflection device.SummaryThe object of the invention is to eliminate the above-mentioned disadvantages. The object is achieved by the subject matter according to claim 1.Vehicle display systems with multi-function holographic RLAD devices, methods of manufacture, and methods of operating such vehicle display systems, and motor vehicles equipped with such display systems are presented below. By way of non-limiting example, a holographic RLAD device includes a fixed group of lighting elements, such as a mixed series of red and green LEDs or laser diodes, arranged in a one-dimensional (1D) or two-dimensional (2D) array. For a given color, each lighting element is set to a particular angle of emission, which can be achieved using light deflection prisms on the LEDs or angled reflectors behind the LEDs. A multilayer holographic optical element (HOE) is mounted in front of the array of illumination elements such that a reference beam emitted from each LED / laser diode passes through the multilayer HOE. In one example, the HOE consists essentially of two stacked and mutually parallel holographic plates, one layer being optically configured to diffract only light of a first wavelength (e.g., green) and the other layer being optically configured to diffract only light of a second wavelength (e.g., red). Each of the holographic layers is recorded with one or more hologram patterns, each of which generates a predefined warning symbol when illuminated with a corresponding wavelength at a respective angle of incidence. Additional or alternative symbols / patterns may be added to the holographic RLAD device module by replacing or adding a new holographic layer instead of having to replace the entire module.Aspects of this disclosure are directed to digital projection display devices having multilayer holographic plate structures for projecting complex and irregular geometric symbols. In one example, a holographic projection display system is shown for projecting images onto a reflective surface, such as the inner surface of a windshield of an automobile. The holographic projection display system includes a group of illumination elements arranged in a predefined pattern and attached to a multilayer HOE array. The grouped lighting elements comprise at least two sets of light emitting diodes: a first set of light emitting diodes emitting light having a first wavelength and each having a respective angle of emission toward a reflective surface, and a second set of light emitting diodes emitting light having a second wavelength and each having a respective angle of emission toward the reflective surface. The multilayer HOE array is located in front of the arrayed light emitting diodes and includes at least two holographic layers: a first holographic plate recorded with a plurality of holographic patterns each optically configured to diffract the wavelength of light emitted from the first set of light emitting diodes, and a second holographic plate mounted on the first holographic plate and recorded with a plurality of holographic patterns each optically configured to diffract the wavelength of light emitted from the second set of light emitting diodes.Additional aspects of this disclosure are directed to motor vehicles equipped with multi-function holographic RLAD devices. As used herein, the terms "vehicle" and "motor vehicle" may be used interchangeably and interchangeably to include any relevant vehicle platform, such as passenger cars, commercial vehicles, industrial vehicles, off-road and all-terrain vehicles (ATV), motor cycles, agricultural equipment, aircraft, spacecraft, watercraft, and so forth. In one example, a motor vehicle includes a vehicle body having a passenger compartment, multiple road wheels attached to the vehicle body (e.g., via corner modules coupled to a single body or body-to-frame chassis), and other standard original equipment. A prime mover, which may be in the form of an electric traction motor and / or an internal combustion engine (ICE) assembly, is located within the vehicle body and drives the road wheel / wheels to propel the vehicle. It is contemplated that disclosed display designs and features may be equally applicable in vehicle and non-vehicle applications.Continuing with the discussion of the above example, the vehicle is also equipped with a holographic projection display system mounted within the passenger compartment (e.g., on or in the dashboard, rearview mirror, or headliner). The holographic projection display system includes a group of illumination elements arranged in a fixed light array and mounted on a multilayer HOE array. The grouped lighting elements include multiple sets of light emitting diodes, such as a first set of light emitting diodes that emit light at a first wavelength and each have a respective angle of emission toward the vehicle windshield and a second set of light emitting diodes that emit light at a second wavelength different from the first wavelength and each have a respective second angle of emission toward the windshield. The emission angles of the first light emitting diodes are different from each other, and the emission angles of the second light emitting diodes are different from each other.The multilayer HOE array is located in front of the sets of light emitting diodes and includes a plurality of holographic layers, such as a first holographic plate, stacked on and attached to a second holographic plate. The first holographic plate is recorded with a plurality of holographic patterns, each of which is optically configured to diffract only the wavelength of light emitted from the first light emitting diodes at their respective emission angles. Similarly, the second holographic plate is recorded with a plurality of holographic patterns, each of which is optically configured to diffract only the wavelength of light emitted from the second light emitting diodes emitted at their respective emission angles.Aspects of this disclosure are also directed to methods of manufacture and methods of operating any of the holographic projection display devices, vehicle display systems, and motor vehicles described herein. In one example, a method of assembling a holographic projection display system for projecting images onto a reflective surface is presented. This representative method includes, in any order and in any combination with any of the options and features disclosed above and below: arranging a group of lighting elements in a predefined pattern, the group of lighting elements including: a plurality of first light emitting diodes having a first light wavelength and each having a respective first emission angle toward the reflective surface, and a plurality of second light emitting diodes having a second light wavelength and each having a respective second emission angle toward the reflective surface; Attaching a multilayer holographic optical element array to the array of lighting elements before the plurality of first and second light emitting diodes, the multilayer HOE array comprising: a first holographic plate recorded with one or more first holographic patterns each optically configured to diffract the first light wavelength of the first light emitting diodes emitted at one or more of the respective first emission angles; and a second holographic plate attached to the first holographic plate, the second holographic plate recorded with one or more second holographic patterns each optically configured to diffract the second light wavelength of the second light emitting diodes emitted at one or more of the respective second emission angles.For any of the disclosed vehicles, systems, and methods, at least one of the holographic patterns recorded in the first holographic plate may be optically configured to diffract only light of the first wavelength emitted at the respective emission angle of a single one of the first light emitting diodes. Likewise, at least one of the holographic patterns recorded in the second holographic plate may be optically configured to diffract only light of the second wavelength emitted at the respective emission angle of a single one of the second light emitting diodes. As another option, at least one of the holographic patterns recorded in the first holographic plate may be optically configured to diffract only light of the first wavelength emitted at the respective emission angles of two of the first light emitting diodes. Likewise, at least one of the holographic patterns recorded in the second holographic plate may be optically configured to diffract only light of the second wavelength emitted at the respective emission angles of two of the second light emitting diodes. In this example, the respective emission angles of the two first light emitting diodes are different from each other, and the respective emission angles of the two second light emitting diodes are different from each other.For any of the disclosed vehicles, systems, and methods, the second holographic plate may include one or more optically transparent regions lacking a holographic pattern; each optically transparent region may overlap one of the holographic patterns recorded in the first holographic plate. As another option, one of the first holographic patterns may diffract only the light wavelength emitted at the respective emission angle of a respective first light emitting diode, and one of the second holographic patterns may diffract only the light wavelength emitted at the respective emission angle of a respective second light emitting diode. In this case, the first holographic pattern overlaps the second holographic pattern such that light diffracted by the overlapping holographic patterns is combined to project a combined image of a third light wavelength (e.g., yellow) different from the first and second wavelengths (e.g., red and green). In addition, the respective emission angle of the respective first light emitting diode can be different from the respective emission angle of the respective second light emitting diodes.For any of the disclosed vehicles, systems, and methods, an optically clear adhesive layer, a mounting bracket, and / or a set of fasteners may be used to attach the first holographic plate to the second holographic plate. As another option, the holographic projection display system may employ a plurality of light prisms or reflectors, each of which is disposed adjacent a respective one of the light emitting diodes to direct a reference beam emitted therefrom at the respective emission angle of the diode. As yet another option, the multiple sets of light emitting diodes may be mounted in a fixed light array that includes either a single row (1D) of diodes or multiple rows (2D) of diodes. The sets of light emitting diodes may be embodied as light emitting diodes, laser diodes or a combination of both. As another option, the first holographic plate may be mounted on and substantially parallel to the second holographic plate. Each of the holographic plates may be a substantially flat and optically transparent one-piece plate structure.The foregoing summary does not represent every embodiment or aspect of the present disclosure. Rather, the foregoing summary provides a summary of only some of the novel concepts and features set forth herein. The above features and advantages, as well as other features and attendant advantages of this disclosure, will be readily apparent from the following detailed description of the illustrated examples and representative ways of carrying out the disclosure when taken in conjunction with the accompanying drawings and the appended claims. Moreover, this disclosure expressly includes all combinations and sub-combinations of the elements and features set forth above and below.Brief Description of the DrawingsFIG. 1 is a front perspective view of a portion of a passenger compartment of a representative motor vehicle having a multi-mode information display system with a multi-function holographic RLAD device, in accordance with aspects of the present disclosure. FIG. 2 is a schematic illustration of a representative holographic projection display system in accordance with aspects of the present disclosure. FIG. 3 is a schematic illustration of another representative holographic projection display system in accordance with aspects of the present disclosure. FIG. 4 is a flow diagram illustrating a control protocol for a representative display system for operating a multi-function holographic RLAD device, which may correspond to non-transitory, memory-stored instructions executable by a resident or remote microprocessor, a control module, a logic circuit, a central controller or other integrated circuit (IC) device, or a network of circuits / modules / microprocessors / controllers / IC devices (collectively "controller"), in accordance with aspects of the disclosed concepts.The present disclosure is susceptible to various modifications and alternative forms, and some representative embodiments of the disclosure are shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the novel aspects of this disclosure are not limited to the particular forms illustrated in the above-listed drawings. Rather, this disclosure covers all modifications, equivalents, combinations, permutations, groupings, and alternatives falling within the scope of this disclosure, such as those encompassed by the appended claims.DETAILED DESCRIPTIONThis disclosure is susceptible to embodiment in many different forms. Representative embodiments of the disclosure are shown in the drawings and will be described in detail herein, it being understood that these embodiments are provided as an illustration of the disclosed principles and not as limitations on the broad aspects of the disclosure. To this extent, elements and limitations described, for example, in the sections of the Summary, Introduction, Summary, Brief Description of the Drawings and Detailed Description, but not expressly recited in the claims, should not be individually or jointly incorporated into the claims by way of inference, inference, or otherwise. Moreover, the denomination of "first / r / s", "second / r / s", "third / r / s" and so forth in the specification or claims is not used per se to produce a serial or numerical limitation; unless expressly stated otherwise, these terms may be used to facilitate reference to similar features in the specification and drawings and to distinguish between similar elements in the claims.For purposes of this disclosure, unless expressly excluded: the singular includes the plural and vice versa (for example, indefinite articles "a / r / s" and "a / r / s" should generally be construed to mean "one / e / s or more"); the words "and" and "or" are intended to be both conjunctival and disjunctive; the words "any" and "all" are intended to mean both "any and all"; and the words "including", "including", "comprising", "having", and the like are intended to mean "including without limitation". Finally, directional adjectives and adverbes such as front, rear, inside, outside, starboard, port, vertical, horizontal, up, down, front, rear, left, right, and so forth may be present with respect to a motor vehicle, such as a forward direction of travel of a motor vehicle when the vehicle is operatively oriented on a horizontal travel surface.Referring now to the drawings, wherein like reference numerals refer to like features throughout the several views, there is shown in FIG. 1 a representative motor vehicle, generally designated 10, and shown herein as sedan passenger cars for purposes of discussion. The illustrated motor vehicle 10-also referred to herein for short as a "motor vehicle" or "vehicle"-is merely an example application by which aspects of this disclosure may be implemented. Likewise, use of the present concepts to project information onto a front windshield of a motor vehicle should be appreciated as a non-limiting implementation of disclosed features. Thus, it should be appreciated that aspects and features of this disclosure may be effected to project information onto other vehicle surfaces (e.g., rear and rear windows, side door panels, and so forth) used for any logically relevant type of motor vehicle and equally implemented for motor vehicle and non-motor vehicle applications. Moreover, only selected components of the motor vehicle and vehicle display system are shown and described in detail herein. However, the vehicles and systems discussed below may include numerous additional and alternative features and other available peripheral hardware for carrying out the various methods and functions of this disclosure.To protect vehicle occupants from bad weather and road dirt, a front windshield 18 is located between two A-pillars 24 at a front end of a passenger compartment 14 of a vehicle body 12 of the motor vehicle 10. A lower edge of the front window frame 16 is defined by a dashboard trim 20, whereas an upper edge is defined by a roof rail 22, and the two side edges of the frame 16 are defined by a pair of A-pillars 24 (only one of which is visible; a second mirrored mating piece is located on the opposite side of the window frame 16). Also present within the vehicle cabin 14 is a control-supporting center pillar 26 that houses a vehicle telematics unit, represented in FIG. 1 by a touch screen interactive video display device 28 and a user input button 30. The touch screen video display 28 is operable to receive user input via soft touch controls and simultaneously display images, texts, and video-based content. A digital instrument panel (IP) 32 is housed within a front instrument panel 34 in front of a steering wheel 36 and displays gauges, instrumentation, and controls for monitoring and regulating selected operations of the vehicle 10 (e.g., speedometer, tachometer, odometer, fuel gauge, engine temperature gauge, warning lights, and so forth). It should be appreciated that disclosed display devices and related features per se are not limited to the specific passenger compartment layout depicted in FIG. 1.Embedded in an upper surface of the front dashboard 34 is a multi-function holographic RLAD device 150 that is part of an in-vehicle enhanced display system (EDS) for dynamically presenting information to vehicle occupants to improve the operation of the automobile 10. For example, the holographic RLAD device 150 is operable to selectively project graphical images and data onto the front windshield 18 to present vehicle-related and non-vehicle-related information of various forms, including real-time operation of vehicle systems, environmental driving conditions, infotainment features, personalized occupant-specific data, and so forth. The holographic RLAD device 150, the touchscreen electronic video display 28, the button 30, and the digital IP 32 communicate, wired or wirelessly, with a programmable electronic control unit (ECU) 38. the vehicle ECU 38 can systematically monitor various sensors, system components, and / or other relevant inputs, both manually and automatically, and identify information based on these monitored inputs that is passed to the vehicle occupants or to passing pedestrians, vehicles, and so forth, and determine a graphical representation of the selected information. This ECU 38 may communicate directly with various systems, subsystems, and components, or alternatively or additionally, the ECU 38 may communicate over a distributed computing network, such as a LAN / CAN system, a satellite system, the Internet, and so forth. Various vehicle sensors may be prompted to monitor vehicle speed, engine speed, transmission state, engine coolant temperature, fuel level and economy, oil level, tire pressure, wheel slip, battery state of charge (SOC), battery range, mileage, navigation information, and / or any other parameter representative of vehicle operation.The front windshield unit 18 functions as both an aerodynamic, splitter resistant windshield and a reflective display surface onto which alerts, icons, and other data are projected by the holographic RLAD device 150. In particular, the RLAD display device 150 is capable of dynamically displaying images on the front windshield 18 that are overlaid through the windshield 18 within a forward field of view of an occupant. For example, an EDS graphics engine executing as a dedicated software application or discrete control module within the ECU 38 includes display software stored as processor-executable code that translates data and user requests into graphical representations of desired information. To provide "see-through" functionality, the front windshield 18 remains sufficiently transparent to allow occupants of the vehicle 10 to clearly see objects outside the passenger compartment 14 through the front windshield 18 while selected images are displayed by the RLAD display 150 within one or more deployed viewing areas. As a non-limiting example, the front windshield unit 18 of FIG. 1 includes transparent display areas A 1 onto which images and data within a driver's field of view are projected. It is certainly within the scope and spirit of this disclosure that the front windshield unit 18 provides additional or alternative transparent display areas, any or all of which may include different shapes, sizes, and / or positions from those shown in the drawings.FIGS. 2 and 3 illustrate two representative examples of holographic projection display systems 250 and 350, which may be embodied as a multi-function holographic RLAD device 150 for dynamically displaying information to a driver of an automobile 10 of FIG. 1. Although different in appearance, it is contemplated that any of the options and features described herein with reference to the display system 250 of FIG. 2 may be incorporated individually or jointly into the display system 350 of FIG. 3, and vice versa. By way of example, and not limitation, both display systems 250, 350 may be typified by two interoperable subsystems: (1) a mixed group of lighting elements 252 and 352 arranged in a preset light pattern; and (2) a multilayer holographic optical element (HOE) array 254 and 354 fixedly attached to the light group 252, 352 and located in front of the light emitting diodes 256A, 256B, 356A, and 356B in the light group 252, 352. Each group of lighting elements 252, 352 includes at least two different sets of light emitting diodes: (1) a primary colored (first) set of (first) light emitting diodes 256A, 356A sharing a common (first) light wavelength (e.g., green); and (2) an auxiliary colored (second) set of light emitting diodes 256B, 356B sharing another common (second) light wavelength (e.g., red). It may be desirable for the light emitting diodes 256A, 256B, 356A, 356B in a given light group 252, 352 to be mounted in a fixed light array with either a single rectilinear row (1D) of diodes (FIG. 3 ) or multiple rectilinear rows and columns (2D) of diodes (FIG. 2 ). Alternatively, the grouped lighting elements 252, 352 may be arranged in a 3D array of diodes and / or in a pivotable / displaceable array of diodes. It is also contemplated that each of light emitting diodes 256A, 256B, 356A, and 356B may take any suitable lighting element form factor, including a single color LED, an RGB LED, an SMD LED, a semiconductor laser diode, a fiber optic laser, and so forth.In contrast to conventional RLAD and HUD system configurations, each light emitting diode 256A, 356A in the primary light emitting diode set may have a respective (first) light emission angle (e.g., first and second primary beam angles θ A1 and θ A2) directed toward a reflective surface 218 and different from the light emission angles of the other light emitting diodes 256A, 356A in this set. For example, all four of the green light emitting diodes 256A in FIG. 2 have respective beam angles that are different from each other, and all four of the red light emitting diodes 256B in FIG. 2 have respective beam angles that are different from each other. Similarly, each light emitting diode 256B, 356B in the auxiliary light emitting diode set has a respective (second) light emission angle (e.g., first and second auxiliary beam angles θ B1 and θ B2) different from the light emission angles of the other light emitting diodes 256B, 356B in this set. Although shown in FIG. 2 as having a total of eight (8) diodes - four green light emitting diodes 256A and four red light emitting diodes 256B - and in FIG. 3 as having a total of four (4) diodes - one green light emitting diode 356A and three red light emitting diodes 356B - the mixed group of lighting elements 252, 352 may include any number and combination of light emitting diodes that correspond to an intended application.Each illumination element may be adjusted to its particular angle of emission using, for example, a light deflection prism mounted in front of the illumination element or an angled light reflector mounted behind the illumination element. For example, in FIG. 2, a primary (first) set of light reflectors 258A are packaged within a protective display system housing 260 having the illumination element group 252 and the HOE array 254. Each of these light reflectors 258A is disposed immediately behind or rewrites a respective light emitting diode 256A and reflects a reference light beam emitted therefrom at the respective emission angle of this diode 256A. An additional (second) set of light reflectors 258B is also packaged within the display system housing 260; each light reflector 258B is disposed immediately behind or rewrites a respective light emitting diode 256B and reflects a reference light beam emitted therefrom at the respective emission angle of that diode 256B.By way of comparison, FIG. 3 shows a primary (first) set of light prisms 358A packaged within a protective display system housing 360 having the lighting element group 352 and the HOE array 354. Each of these light prisms 358A is disposed immediately before or at a desired lateral offset from a respective light emitting diode 356A and refracts a reference light beam emitted therefrom at the respective emission angle of that diode 356A. An additional (second) set of light prisms 358B is also packaged within the display system housing 360; each light prism 358B is disposed immediately before or at a desired lateral offset from a respective light emitting diode 356B and refracts a reference light beam emitted therefrom at the respective emission angle of that diode 356B. It is also contemplated that the display systems 250, 350 may omit some or all of the illustrated prisms and deflectors instead of individually aligning each illumination element to a particular beam angle.The multi-layer HOE array 254, 354 is shown disposed between the illumination element group 252, 352 and the reflective surface 218, 318 such that a reference beam emitted from each light emitting diode 256A, 256B, 356A, 356B passes through the HOE array 254, 354 and projects one or more warning symbols 220A- 220C and 320A- 320C onto the reflective surface 218, 318. Each HOE array 254, 354 includes at least two holographic layers: a primary (first) holographic plate 262A and 362A recorded with one or more primary (first) holographic patterns 264A, 364A; and (2) an additional (second) holographic plate 262B and 362B adjacent to the primary holographic plate 262A, 362A and recorded with one or more additional (second) holographic patterns 264B, 364B. According to the illustrated example, each of the holographic plates 262A, 262B, 362A, 362B may be fabricated as a substantially flat and optically transparent, one-piece plate structure of a writable light-sensitive material (e.g., photopolymerizable monomers and glass). As another option, the primary holographic plate 262A, 362A may be physically coupled to the additional holographic plate 262B, 362B, for example, via an optically clear adhesive layer 266, a mounting bracket, a set of fasteners, and so forth. For example, the primary holographic plate 262A of FIG. 2 is shown mounted directly on and substantially parallel to the additional holographic plate 262B.With continued reference to FIGS. 2 and 3, each of the holographic patterns 264A, 364A recorded on the primary holographic plates 262A, 362A is optically configured to diffract the common light wavelength (e.g., green) emitted from the primary light emitting diodes 256A, 356A at their respective emission angles. Similarly, each of the additional holographic patterns 264B, 364B is optically configured to diffract the common light wavelength (e.g., red) emitted by the additional light emitting diodes 256B, 356B at their respective emission angles. The holographic plates 262A, 362A, 262B, 362B may be wholly or partly formed of light-sensitive material that locally changes its internal refractive index and / or light absorption coefficient depending on the incident light intensity. An interference pattern formed by the interference between light from a reference beam and light from an object, both coherent or partially coherent, can illuminate the photosensitive material and produces a variation in refractive index / absorption on the plate. The interference pattern may be different for different combinations of reference beam(s) and thus the distribution of the change in refractive index or absorption on the plate.Each recorded holographic pattern can diffract the wavelength of light emitted by a single one of the illumination elements. For example, the rightmost holographic pattern 364B of FIG. 3 may diffract only the (red) light wavelength emitted by the rightmost supplemental light emitting diode 356B at its respective light emission angle (e.g., +5° from vertical), whereas the middle holographic pattern 364B of FIG. 3 may diffract only the (red) light wavelength emitted by the middle supplemental light emitting diode 356B at its respective light emission angle (e.g., -15° from vertical). In other words, none of these holographic patterns 364B is optically configured to diffract light of a different wavelength or light of a different angle. As a comparison point, the leftmost primary holographic pattern 364A of FIG. 3 may diffract only the (green) light wavelength emitted from the leftmost primary light emitting diode 356A at its respective light emission angle (e.g., -25° from vertical) and not the (red) light wavelength emitted from the leftmost additional light emitting diode 356B. Conversely, the leftmost additional holographic pattern 364B of FIG. 3 may diffract only the (red) light wavelength emitted by the leftmost additional light emitting diode 356B at its respective light emission angle (e.g., +10° from vertical) and not the (green) light wavelength emitted by the leftmost primary light emitting diode 356A.Each recorded holographic pattern can diffract the wavelength of light emitted by a selected combination of the illumination elements. For example, the leftmost holographic pattern 264A of FIG. 2 may diffract only the (green) light wavelength emitted by the two left-side primary light emitting diodes 256A at their respective light emission angles (e.g., projecting a larger and brighter animal warning symbol 220A). This holographic pattern 264A does not diffract light of another wavelength (red) or light of another angle (regardless of color). On the other hand, the rightmost holographic pattern 264B of FIG. 2 may diffract only the (red) light wavelength emitted by the two right side supplemental light emitting diodes 256B at their respective light emission angles (e.g., projecting a larger and brighter animal warning symbol 220C). This holographic pattern 264B does not diffract light of another wavelength (green) or light of another angle (regardless of color). As another option, one or both of the holographic layers may include one or more optically transparent regions, such as transparent windows 368A of the primary holographic plate 362A in FIG. 3, which lack a holographic pattern and overlap one or more of the holographic patterns of the adjacent holographic plate, which may allow a brighter projected symbol.Selected recorded holographic patterns can be optically aligned with each other to combine their diffracted light and thereby produce symbols of a different wavelength. As noted above, the leftmost primary holographic symbol 364A of FIG. 3 may diffract only the (green) light wavelength emitted from the leftmost primary light emitting diode 356A at its respective light emission angle, and the leftmost additional holographic symbol 364B of FIG. 3 may diffract only the (red) light wavelength emitted from the leftmost additional light emitting diode 356B at its respective light emission angle. However, the two leftmost holographic patterns 364A, 364B of FIG. 3 are optically aligned, for example, with the additional symbol 364B disposed between the primary symbol 364A and the two matched light emitting diodes 356A, 356B, such that reference beams emitted therefrom pass through both of the leftmost holographic patterns 364A, 364B. In doing so, light diffracted by these optically overlapping holographic patterns 364A, 364B combines to emit an enlarged warning symbol 320A of a new (yellow) light wavelength different from the wavelengths of the two matching light emitting diodes 356A, 356B.An attendant advantage of disclosed holographic projection display systems over existing RLAD devices is the ability to display complex symbols and text rather than just basic geometric shapes (e.g., reflection of flashing lights shaped as dots, triangles, octagons, and so forth). Attendant advantages of disclosed holographic projection display systems over existing HUD devices may include reduced part costs and packaging space. Current provider solutions using a masked approach to providing static warnings have low light efficiency; disclosed holographic projection display systems allow for increased light efficiencies and thus may provide increased symbol brightness (e.g., at least about 4800 nits). The use of angle and wavelength multiplexing of holograms can be used to enable disclosed holographic projection display systems to achieve a variety of warnings. A variety of warnings may also be achieved by zonking the HOE with separate light sources.Referring to the flowchart of FIG. 4, an improved method or control protocol for operating an in-cabin display system of a motor vehicle, such as the automobile 10 of FIG. 1, with a holographic RLAD device, such as the display systems 250 and 350 of FIGS. 2 and 3, is generally described at 400 in accordance with aspects of the present disclosure. Some or all of the operations illustrated in FIG. 4 and described in greater detail below may be representative of an algorithm corresponding to non-transitory processor-executable instructions stored, for example, in main or auxiliary or remote storage (e.g., resident vehicle storage device and / or remote cloud computing service database). These instructions may be executed, for example, by a microprocessor, a central controller, a dedicated control module, logic circuitry, or other module or device, or network of controllers / modules / devices (e.g., resident vehicle ECU 38 of FIG. 1 and / or remote server-class cloud computing terminal) to perform any or all of the functions associated with the disclosed concepts described above and below. It should be appreciated that the order of execution of the illustrated operation blocks may be changed, additional operation blocks may be added, and some of the operations described herein may be modified, combined, or eliminated.The method 400 begins at the start of the terminal block 401 of FIG. 4 with memory-stored, processor-executable instructions for initializing a holographic projection display control protocol for a motor vehicle. This routine may be initialized in real time, near real time, continuously, systematically, sporadic, and / or at predefined time intervals, for example every 10 or 100 milliseconds during operation of the motor vehicle 10. As yet another option, terminal block 401 may be initialized in response to a user command request (e.g., via telematics input controllers 28, 30), a resident vehicle control request (e.g., from ECU 38), or a broadcast request signal received from a central backoffice (BO) vehicle service system (e.g., from the cloud host service). In one example, method 400 may be automatically initialized in response to a key-on event in which a driver of vehicle 10 presses a start key and simultaneously shifts vehicle 10 to drive gear (D) or low gear (L 1 / L 2). Upon completion of some or all of the control operations illustrated in FIG. 4, the method 400 may transition to and temporarily end the end of the terminal block 417, or may optionally return to the terminal block 401 and run in a continuous loop (e.g., until the vehicle 10 is switched back to the park position (P) and shut down).In transitioning from the terminal block 401 to the object detection process block 403, the method 400 detects a target object, such as a vehicle, pedestrian, roadway obstacle, danger, or animal, in front of the vehicle 10 using one or more of a networked array of in-vehicle sensing devices (e.g., cameras, RADAR array, LiDAR detector, capacitive sensors, and so forth). In response to detecting a target object, the method 400 automatically executes the object identification process block 405 to categorize and track the detected object. The method 400 then proceeds to the threshold distance decision block 407 to determine whether or not a target distance to the target object is less than a predefined threshold distance at which a warning is triggered for this type of target object (e.g., 100 feet for pedestrians or 30 feet for vehicle). If not (block 407=NO), the method 400 may return to process block 403 and continue scanning for oncoming target objects.Upon determining that the target distance to the target object is less than the threshold warning distance (block 407= JA), the method 400 may responsive execute the threshold speed decision block 409 to determine whether a current vehicle speed of the host vehicle reaches or exceeds a predefined threshold warning speed at which a warning is triggered (e.g., ≥ 25 miles per hour (MPH)). If not (block 409=NO), the method 400 may return to process block 405 and continue tracking the detected target object. Upon determining that the current speed of the host vehicle is equal to or greater than the threshold warning speed (block 409= JA), the method 400 may responsive execute the HOLOGRAPHIC WARNING PROCESS BLOCK 411 and activate the holographic projection display system (e.g., the RLAD device 150 of FIG. 1 ), including illuminating the corresponding LED or LEDs associated with the holographic warning symbol corresponding to the detected target object.After activating the holographic projection display system, the method 400 may proceed to CONTINUE THE RISK DECISION BLOCK 413 to determine whether or not the detected target object is no longer a potential risk. For example, method 400 may determine whether or not the speed of the host vehicle has been reduced to below the threshold warning speed and / or the target distance to the target object is now greater than the threshold warning distance and / or the target object is no longer detected. Upon determining that the target object continues to be a potential hazard (block 413= JA), the method 400 may return to process block 411 and continue displaying the holographic warning icon corresponding to the detected target object (which may then be augmented, lightened, flashing, or accompanied by an audible or tactile warning). If the target object is no longer a potential risk (block 413= JA), the method 400 may in response execute the HOLOGRAPHIC WARP ACTIVATION PROCESS BLOCK 415 and deactivate the LED(s) or LEDs for the holographic warning symbol corresponding to the detected target object. The method 400 may then return to process block 403, or may proceed to terminal block 417 and end temporarily.To produce a projected warning symbol having a different color than that of the individual illumination elements (e.g., yellow symbol of green and red LEDs), the desired warning symbol pattern is separately recorded in each HOE film intended for the individual layer, the film layers are laminated together with the recorded symbol patterns optically overlapping, and each layer is illuminated with a corresponding reconstructed beam that is the same as the reference beam. It is contemplated that a projected symbol may be configured as an analogous representation of speed, such as a series of horizontally oriented blocks, each corresponding to a respective vehicle speed (e.g., extreme left block=5 mph, second block from left=10 mph, third block from left=15 mph, and so forth). As another example implementation, a projected symbol may be configured as an analog representation of delta from the set speed (e.g., extreme left block = +1-5 mph, second block from left = +6-10 mph, third block from left = +11-15 mph, and so forth). In another example implementation, a projected symbol may be configured as an analogous representation of the fuel level (e.g., extreme left block=remain 2 gallons, second block from left=remain 4 gallons, third block from left=remain 4 gallons, and so forth) or a battery state of charge warning 220D (e.g., extreme left block=remain 60 miles (mi) range (R), second block from left=remain 100 mi R, third block from left=150 mi R, and so forth).Aspects of this disclosure may be implemented, in some embodiments, by a computer-executable program of instructions, such as program modules, generally referred to as software applications or application programs, executed by any of the controllers or controller variants described herein. Software may include, in non-limiting examples, routines, programs, objects, components, and data structures that perform particular tasks or implement particular types of data. The software may interface to enable a computer to respond according to an input source. The software may also cooperate with other code segments to initiate a plurality of tasks in response to data received in conjunction with the source of the received data. The software may be stored on any of a variety of storage media, such as CD-ROM, magnetic disk, and semiconductor memory (for example, various types of RAM or ROM).Moreover, aspects of the present disclosure may be implemented with a variety of computer system and computer network configurations, including multiprocessor systems, microprocessor-based or programmable consumer electronics, minicomputers, mainframe computers, and the like. Additionally, aspects of the present disclosure may be implemented in distributed computing environments where tasks are performed by resident and remote processing devices connected through a communication network. In a distributed computing environment, program modules may reside in both local and remote computer storage media, including storage devices. Aspects of the present disclosure may therefore be implemented in conjunction with various hardware, software, or a combination thereof in a computer system or other processing system.Any of the methods described herein may include machine readable instructions for execution by: (a) a processor, (b) a controller, and / or (c) any other suitable processing device. Any algorithm, software, control logic, protocol, or method disclosed herein may be embodied as software stored on a tangible medium, such as, for example, flash memory, solid state drive (SSD) memory, hard disk drive (HDD) memory, CD-ROM, digital versatile disk (DVD), or other storage devices. The entire algorithm, control logic, protocol, or method, and / or portions thereof may alternatively be executed by a device other than a controller and / or executed in firmware or dedicated hardware in an available manner (e.g., implemented by an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable logic device (FPLD), discrete logic, and so forth). Further, although specific algorithms may be described with reference to flowcharts and / or workflow diagrams presented herein, many other methods for implementing the example machine readable instructions may alternatively be used.Aspects of the present disclosure have been described in detail with reference to the illustrated embodiments; however, those skilled in the art will appreciate that many modifications may be made thereto without departing from the scope of the present disclosure. The present disclosure is not limited to the precise construction and composition disclosed herein; any and all modifications, changes, and variations apparent from the foregoing descriptions are within the scope of the disclosure as defined by the appended claims. Moreover, the present concepts expressly include all combinations and sub-combinations of the above elements and features.

Claims

A holographic projection display system (250, 350) for projecting images onto a reflective surface (218), the holographic projection display system (250, 350) comprising: a group of illumination elements (252, 352) arranged in a predefined pattern, the group of illumination elements (252, 352) comprising: a plurality of first light emitting diodes (256A, 356A) having a first light wavelength and each having a respective first angle of emission toward the reflective surface (218), and a plurality of second light emitting diodes (256B, 356B) having a second light wavelength and each having a respective second angle of emission toward the reflective surface (218); and a multilayer holographic optical element (HOE) array (254, 354) mounted on the group of illumination elements (252, 354, A method of manufacturing a semiconductor device according to the invention is provided in a semiconductor device including: a first holographic plate (262A, 362A) recorded with a plurality of first holographic patterns (264A, 364A) each optically configured to diffract the first light wavelength of the first light emitting diodes (256A, 356A) emitted at one or more of the respective first emission angles; and a second holographic plate (262B, 362B) recorded on the first holographic plate (262A, 362A); the second holographic plate (262B, 362B) recorded with a plurality of second holographic patterns (264B, 364B) each optically configured to diffract the second light wavelength of the second light emitting diodes (256B, 362B), 356b) emitted at one or more of the respective second emission angles, wherein one of the first holographic patterns (264A, 364A) diffracts only the first light wavelength emitted at the respective first emission angles from two of the first light emitting diodes (256A, 356A), and one of the second holographic patterns (264B, 364B) diffracts only the second light wavelength emitted at the respective second emission angles from two of the second light emitting diodes (256B, 356B).The holographic projection display system (250, 350) of claim 1, wherein one of the first holographic patterns (264A, 364A) diffracts only the first light wavelength emitted at the respective first emission angle of a respective one of the first light emitting diodes (256A, 356A), and one of the second holographic patterns (264B, 364B) diffracts only the second light wavelength emitted at the respective second emission angle of a respective one of the second light emitting diodes (256B, 356B).The holographic projection display system (250, 350) of claim 1, wherein the second holographic plate (262B, 362B) comprises an optically transparent region that lacks holographic patterns and overlaps one of the first holographic patterns (264A, 364A) of the first holographic plate (262A, 362A).The holographic projection display system (250, 350) of claim 1, wherein the respective first emission angles of the two of the first light emitting diodes (256A, 356A) are different from each other and the respective second emission angles of the two of the second light emitting diodes (256B, 356B) are different from each other.The projection type holographic display system (250, 350) of claim 1, wherein: one of the first holographic patterns (264A, 364A) diffracts only the first light wavelength emitted at the respective first emission angle of a respective one of the first light emitting diodes (256A, 356A), one of the second holographic patterns (264B, 364B) diffracts only the second light wavelength emitted at the respective second emission angle of a respective one of the second light emitting diodes (256B, 356B), and the one of the first holographic patterns (264A, 364A) overlaps the one of the second holographic patterns (264B, 364B) such that light diffracted by the overlapping holographic patterns is combined to emit an image of a third light wavelength, different from the first and second light wavelengths.The holographic projection display system (250, 350) of claim 4, wherein the respective first angle of emission of the respective one of the first light emitting diodes (256A, 356A) is different from the respective second angle of emission of the respective one of the second light emitting diodes (256B, 356B).The holographic projection display system (250, 350) of claim 1, further comprising an optically clear adhesive layer (266) securing the first holographic plate (262A, 362A) to the second holographic plate (262B, 362B).The holographic projection display system (250, 350) of claim 1, further comprising: a plurality of first light prisms (358A) or reflectors each disposed adjacent a respective one of the first light emitting diodes (256A, 356A) and configured to direct a first reference beam emitted therefrom at the respective first emission angle; and a plurality of second light prisms (358B) or reflectors each disposed adjacent a respective one of the second light emitting diodes (256B, 356B) and configured to direct a second reference beam emitted therefrom at the respective second emission angle.The holographic projection display system (250, 350) of claim 1, wherein the predefined pattern comprises the plurality of first (256A, 356A) and second (256B, 356B) light emitting diodes mounted in a fixed light array with a single row or multiple rows of diodes.

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