HEAD UP DISPLAY BASED ON LASER MEMS EMISSIVE FILM PROJECTION SYSTEM
1. An apparatus, comprising:
- a scan module having one or more laser sources that generate one or more initial laser beams and two or more beam deflectors that deflect the one or more initial laser beams;
a beam optic configured to substantially collimate the one or more initial laser beams to produce one or more collimated laser beams;
one or more beam deflector controllers configured to control the angle of beam deflection from each beam deflector;
relay optics between the two or more beam deflectors configured to image each sequential beam deflector in an optical chain onto the subsequent beam deflector in such a manner that the beam deflecting from the last beam deflector in the optical chain contains a combination or superposition of all the beam deflections of the beam deflectors in the sequence, and maintains a beam divergence of the one or more collimated beams.
An apparatus includes a scan module having one or more laser sources that generate one or more initial laser beams and two or more beam deflectors that deflect the initial laser beam(s). A beam optic substantially collimates the initial laser beam(s) to produce one or more collimated laser beams. one or more beam deflector controllers control the angle of beam deflection from each beam deflector. Relay optics between the two or more beam deflectors image each sequential beam deflector onto the subsequent beam deflector in such a manner that the beam deflecting from the last beam deflector in an optical chain contains a combination or superposition of all the beam deflections of the beam deflectors in the sequence, and maintains a beam divergence of the one or more collimated beams.
- 1. An apparatus, comprising:
a scan module having one or more laser sources that generate one or more initial laser beams and two or more beam deflectors that deflect the one or more initial laser beams; a beam optic configured to substantially collimate the one or more initial laser beams to produce one or more collimated laser beams; one or more beam deflector controllers configured to control the angle of beam deflection from each beam deflector; relay optics between the two or more beam deflectors configured to image each sequential beam deflector in an optical chain onto the subsequent beam deflector in such a manner that the beam deflecting from the last beam deflector in the optical chain contains a combination or superposition of all the beam deflections of the beam deflectors in the sequence, and maintains a beam divergence of the one or more collimated beams.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- 10. An apparatus, comprising:
a scan module having one or more laser sources that generate one or more initial laser beams and two or more beam deflectors that deflect the one or more laser beams; an optic for configuring the initial laser beams to have a specific divergence or focusing angle; relay optics between the two or more beam deflectors configured to image each sequential beam deflector in an optical chain onto the subsequent beam deflector in such a manner that the beam deflecting from the last beam deflector in the optical chain contains a combination or superposition of all the beam deflections of the beam deflectors in the sequence, and results in a desired final beam divergence.
- View Dependent Claims (11, 12, 13, 14, 15)
This Application is a division of U.S. patent application Ser. No. 15/202,476, filed Jul. 5, 2016, the entire contents of which are incorporated herein by reference. U.S. patent application Ser. No. 15/202,476 claims the priority benefit of U.S. Provisional Patent Application No. 62/189,072, filed Jul. 6, 2016, the entire contents of which are incorporated herein by reference.
This Application is related to U.S. Pat. No. 7,295,726, U.S. Patent Application Publication number 20080061026, U.S. patent application Ser. No. 11/465,835, filed Aug. 21, 2006 (now U.S. Pat. No. 7,428,353), and U.S. Provisional Patent Application number 60/526,510, filed Dec. 2, 2003, the contents of all five of which are incorporated herein by reference.
Head-up displays (HUDs) were introduced in automobiles by GM in 1988. In the past decade they have been offered by several automakers, although covering only a small niche of the market. They are now available in many high end car models from various manufacturers, as standard or optional features, thanks to significant R&D progress during the last decade. However, in contradiction to various forecasts, HUDs have still not penetrated the automotive market nearly as much as expected . Automotive safety has been stated as the main driving force for implementing HUDs, which are capable of displaying information without requiring the user to take their eyes off the road, e.g. content from night vision cameras, navigation systems, and others. Studies of driving behavior found that improper lookout, inattention and distraction , as well as “eyes-off-road durations of greater than two seconds”, have significant impact on crash risks . An analysis of rear-end collision avoidance systems concludes that nearly 40% of drivers “appeared to be distracted within five seconds before the crash-imminent alert.” Altogether, it has been found that keeping the driver'"'"'s attention on the road is one of the biggest contributors to avoid accidents. This of course is strongly coupled with the driver'"'"'s vision being aimed ahead of the vehicle, through the car'"'"'s windshield.
For future HUD applications, researchers have proposed different scenarios based on advanced environmental recognition technologies to support and alert the user. For example, systems could highlight traffic signs or obstacles on the road, alerting the driver of what to expect ahead in all road conditions. These extended “augmented reality” versions may utilize parts or the whole windshield of the car to cover whole outside scenario. In contrast to “augmented reality”, the stated safety increase based on the HUD use is primarily derived from the fact that all necessary information from the dashboard is displayed on the windshield and that it is highly simplified and not overloading the driver . Bringing all strings together leads to the conclusion that an automotive head-up display is intended to project much of the regular information the driver would otherwise get from the dashboard, displayed in a minimalistic and common way to minimize driver distraction. This information may include vehicle speed, gear, radio settings, and navigation information.
A light engine creates the necessary light with a monochrome or multi-color content for the projection. Recently, there has been increased focus on MEMS-based laser-scanning light engines due to their compact size and saturated color content capability . This light is projected onto a screen surface, also termed the exit pupil expander or EPE , which is typically a diffuser plate placed at an adequate distance from the projector to achieve needed image size. This screen, typically several centimeters on the diagonal, is actually viewed by the driver due to the alignment of folding mirrors and lenses which make it visible “through” the windshield or a separate combiner plate. The optical path between the diffuser plate and the combiner may include a fairly complex set of folding mirrors and aspheric mirrors or lenses to achieve both a larger virtual image size as well as a greater perceived distance between the driver and the virtual image. In existing HUDs, total distance of the virtual image to the driver may be between 1.5 m to 2 m.
This type of display offers a number of very desirable properties, for example the long focal distance to the image for driver'"'"'s additional comfort and the fact that the information is mostly available only to the driver and not viewable by others. On the other hand it is less efficient (electrical power to actual viewable optical brightness) and bears severe challenges which we will briefly outline. The image on the diffuser plate has to pass several mirrors and/or lenses, each of which result in some brightness loss. Furthermore, the final reflection from the transparent windshield or combiner plate is low (typically less than 25% reflected), i.e. the image transmitted through the windshield to the area above the vehicle is brighter than the one viewed by the driver. But the real challenges in brightness and inefficiency happen prior to this optical train. RGB lasers have low efficiency, especially green lasers, which limits the maximum brightness of the system. Laser combining optics which form a single laser beam, and MEMS projectors can have a further 50% loss. The diffuser plate can have efficiency below 50%.
Regarding the forming of the image content itself, there is an additional inefficiency. A typical non-distracting HUD image is mostly empty space and a small percent of the available image area contains content. Due to the various beam retrace considerations in laser raster projection (active video time vs. complete period of one raster) and the small amount of content, lasers are actually utilized only a few percent of the time. Given the upper limitation on power in the RGB lasers (e.g. 50 mW for green,) the fact that the laser is turned on for roughly ˜5% of the time to form images ˜10-20 times lower brightness. Finally, it is found that if drivers wear polarized glasses, the display may become invisible because of its strong polarization.
One alternative approach to the “virtual image HUD” described above is a “windshield display”, displaying content directly onto the windshield itself so that it can be viewed by the driver and other passengers. In 2007 we published  results of a project for an automotive customer to create a prototype windshield display system which could cover as much windshield area as possible. This concept was enabled by mostly transparent fluorescent emissive “Superimaging” films  that were applied to the surface of the windshield or embedded in a windshield. The films contain nano particles which are substantially transparent in visible wavelengths due to their small size, however when illuminated by a 405 nm laser beam they emit incoherently and in all directions at longer wavelengths, e.g. in blue or red colors. The result is that the windshield itself has readable content presented on it while otherwise remaining transparent. In this approach all of the optical losses associated with the forming of the virtual image at a distance beyond the windshield are avoided, resulting in superior brightness. Furthermore, the resulting image on the treated windshield is viewable from almost every angle, which removes the restrictive “eye-box” challenge for the drivers.
Regardless of whether the virtual image HUD or windshield display methodology is used, our proposal is to improve the efficiencies and driver feeling by employing a single, efficient laser source, replacing the diffuser plate methodology with emissive films or remote phosphors, and displaying vector graphics content instead of rastering bitmap images. The key advantages are listed below:
No speckle noise: One of the major problems with laser-based displays is speckle noise . This phenomenon based on interference of the coherent laser light is a significant drawback which trumps many advantages of the laser-based optical sources and therefore a wide variety of methodologies is employed to reduce this effect . The methodologies add design complexity and moving optical parts and while only reducing the problem. In our proposed methodology where images are generated incoherently on emissive materials, speckle noise is virtually non-existent.
No polarization dependence: Unlike laser based picoprojectors or LCDs, the phosphor-emitted images are not polarized and eliminate the dimming issue for users wearing polarized (sun) glasses.
Higher efficiency and lower cost laser sources: Lasers at the 405 nm and 445-450 nm wavelengths are widely used in blue ray DVDs and other applications and have become widely popular in 3D laser printing systems and many other applications where efficient laser sources are needed at a highly competitive consumer price point. Typical efficiency of a single mode 405 nm laser diode with approx. 200 mW of output power is 20% (−5V and 200 mA). As a comparison, green laser diodes used in picoprojector type HUDs achieve at most 5% and remain very costly.
Less complex optical design: A single (color) laser diode source requires very simple optics without any dichroic mirrors and combiners as used to combine red, green, and blue lasers into a single co-axial beam. RGB lasers are not only difficult to align (especially over automotive temperature range) while reducing optical efficiency, but they are also relatively costly. With a single laser, complex color control hardware and algorithms can also be avoided.
High optical resolution: The laser based display with 405 nm wavelength can have a higher optical resolution than an RGB based display, due to the shorter wavelength laser, especially if compared with RGB'"'"'s red wavelength of ˜638 nm. In the case of vector graphics this results in increased image sharpness and clarity.
The objective of the work that led to embodiments of the present invention was to develop and demonstrate an optical-MEMS based, very low cost and versatile platform for displaying content on Head-Up-Displays using emissive films. Use of MEMS mirrors with potential for use of wide-angle lenses provides the possibility of projecting in a very large volume. At the same time the technology provides low-cost production, high speed, small size, and very low power consumption.
A brief discussion of this work is included in the abstract to a presentation for SPIE Photonics West 2015 by Veljko Milanović et al, entitled “High Brightness MEMS Mirror Based Head-Up Display (HUD) Modules with Wireless Data Streaming Capability”, which is incorporated herein by reference.
An additional objective was to provide different modes of image projection for displays based on scanning mirrors, namely both vector graphics mode and bitmap/raster graphics mode, in the same system. This is what we termed “mixed mode display” and it would allow display of highly bright vector content or video content or some mixed variety, in different viewable areas, to the driver. This objective is addressed by novel optical arrangements of two or more MEMS mirrors with relay optics in between mirrors allowing for the final beam deflection and image projection to be a superposed combination of the two or more beam deflecting MEMS mirrors. These laser beam-deflecting or laser beam-steering scan heads are designed to allow fast rate rastering or vector scanning, or combination of both types of scans, or increased field of regard scans.
A controller which controls the two-axis movement of the MEMS mirror and the emission of the laser source in order to display desired content, a laser source directed by a MEMS mirror to a fluorescent emissive screen, and optics which cause the image emitted by the screen appear as a virtual image to a viewer looking through a substantially transparent substrate or window.
A high brightness Head-Up Display (HUD) module was demonstrated with a fast, dual-axis MEMS mirror that displays vector images and text, utilizing its ˜8 kHz bandwidth on both axes. Two methodologies were evaluated: in one, the mirror steers a laser at wide angles of >48° on transparent multi-color fluorescent emissive film and displays content directly on the windshield, and in the other the mirror displays content on reflective multi-color emissive phosphor plates reflected off the windshield to create a virtual image for the driver. The display module is compact, consisting of a single laser diode, off-the-shelf lenses and a MEMS mirror in combination with a MEMS controller to enable precise movement of the mirror'"'"'s X- and Y-axis. The MEMS controller offers both USB and wireless streaming capability and we utilize a library of functions on a host computer for creating content and controlling the mirror. Integration with smart phone applications is demonstrated, utilizing the mobile device both for content generation based on various messages or data, and for content streaming to the MEMS controller via Bluetooth interface. The display unit is highly resistant to vibrations and shock, and requires only ˜1.5 W to operate, even with content readable in sunlit outdoor conditions. The low power requirement is in part due to a vector graphics approach, allowing the efficient use of laser power, and also due to the use of a single, relatively high efficiency laser and simple optics.
In the following Detailed Description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the figure(s) being described. Because components of described embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.
According to an embodiment of the present invention, a system consists of a MEMS scan module 100, a Fluorescent Emissive Sheet (FES) 106, projection optics and light shaping reflectors 108, a viewing screen 109 and the viewer 112. A part of the projection is lost 110 and one virtual projection image is directed to the user 111. The users'"'"' view should be adjusted to viewer eyebox 112 to see the virtual projection. The MEMS scan module consists of a laser source of <460 nm wavelength with optics 101 to reduce the beam and fit onto a MEMS mirror 103 and a controller 104. The controller is used for content generation and adjusting the displayed content on the projection surface. The controller is used to steer the MEMS device to draw vector content and drive the laser, and can be controlled wirelessly from a mobile device, or can be connected to a computer. The MEMS mirrors are capable of scanning about two axes. Examples of suitable MEMS mirrors are described, e.g., in U.S. Pat. No. 7,295,726, U.S. Patent Application Publication number 20080061026, U.S. patent application Ser. No. 11/465,835, and U.S. Provisional Patent Application No. 60/526,510, the contents of all four of which have been incorporated herein by reference above. The FES may be a transparent emissive film by Sun Innovations or any other vendor, which is excited by 405 nm wavelength laser, converts the energy and emits in a single color, e.g. ˜450 nm blue color, or a combination of colors to form white.
There are a number of different possible configurations for the relay optics 605, 607 and the beam deflectors 603, 609. By way of example, and not by way of limitation, in some implementations, the relay optics 605, 607 may include one or more of the following: off-axis parabolic reflectors, off-axis elliptical reflectors, off-axis toroidal reflectors, free-form reflectors, or free-form refractors or combinations of two or more of these. By way of example, and not by way of limitation, in some implementations, one of the beam deflectors 603, 609 may be configured to scan about one optical axis and the other beam deflector may be configured to scan about another optical axis, substantially orthogonal to the first optical axis. By way of example, and not by way of limitation, in other implementations, one of the beam deflectors 603, 609 may be configured to scan about one optical axis and the other beam deflector may be a dual-axis beam deflector, configured to scan about two orthogonal optical axes. By way of example, and not by way of limitation, in some implementations, one of the beam deflectors 603, 609 may be configured to scan about at least one optical axis and the other beam deflector is configured to synchronize with the first optical deflector, deflecting the beam about substantially the same optical axis to result in increased total beam deflection.
According to some aspects of the present disclosure, a scan module may include one or more laser sources, an optic, one or more beam deflectors, and relay optics between the two or more beam deflectors. The laser sources generate one or more initial laser beams and the beam deflectors deflect the one or more laser beams. The optic configures the initial laser beams to have a specific divergence or focusing angle. One or more beam deflector controllers coupled to the beam deflectors control the angle of beam deflection from each beam deflector. The relay optics are configured to image each sequential beam deflector onto the subsequent beam deflector in such a manner that the beam deflecting from the last beam deflector in the optical chain contains a combination or superposition of all the beam deflections of the beam deflectors in the sequence, and results in a desired final beam divergence.
In some implementations of the above-described apparatus, the incidence angle of the initial laser beam onto the first beam deflector may be configured to lie substantially in the plane of beam deflection of the same deflector. In some implementations of the above-described apparatus, the incidence angle of the laser beam deflected by the first beam deflector when it lies in its origin un-deflected position, and the relay optics may be configured to lie substantially in the plane of the beam deflection of the second reflector.
In some implementations of the above-described apparatus, the relay optic may be an off-axis parabolic reflector or an off-axis elliptical reflector or an off-axis toroidal reflector.
We demonstrated two concepts for higher brightness head-up displays. They are directly applicable to any displays in human field of view such as in helmets, aircraft, ships or e.g. retail store windows, automotive displays, and displays for reading. Both the virtual image HUD and the direct windshield display embodiment of the concept are focused on eliminating the need for costly, low optical power, and inefficient RGB laser modules. We demonstrated that higher power and higher efficiency 405 nm lasers are able to display multi-color content with high brightness, no speckle noise and no polarization sensitivity by facilitating emissive films and phosphor plates. In its simple form they were able to perform, battery powered, even in bright sunlight outdoor conditions. Lastly, we showed that a simple mobile device application in conjunction with after-market hardware could be utilized to achieve a high quality HUD.
Additional aspects of the present disclosure may be discerned from the accompanying paper entitled “High Brightness MEMS Mirror Based Head-Up Display (HUD) Modules with Wireless Data Streaming Capability” by Veljko Milanović, Abhishek Kasturi, and Volker Hachtel, presented at SPIE Conference on MOEMS and Miniaturized Systems XIV, San Francisco, Calif. Feb. 11, 2015, the entire contents of which are incorporated herein by reference and which is submitted herewith as an Appendix.
While the above is a complete description of the preferred embodiments of the present invention, it is possible to use various alternatives, modifications, and equivalents. Therefore, the scope of the present invention should be determined not with reference to the above description but should, instead, be determined with reference to the appended claims, along with their full scope of equivalents. Any feature, whether preferred or not, may be combined with any other feature, whether preferred or not. In the claims that follow, the indefinite article “A” or “An” refers to a quantity of one or more of the item following the article, except where expressly stated otherwise. The appended claims are not to be interpreted as including means-plus-function limitations, unless such a limitation is explicitly recited in a given claim using the phrase “means for”. Any element in a claim that does not explicitly state “means for” performing a specified function, is not to be interpreted as a “means” or “step” clause as specified in 35 USC § 112, ¶ 6. Although certain process steps may appear in a certain order in the claims, the steps are not required to be carried out in any particular order unless a particular order is otherwise specified by the claim language.
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