Patent Application
20090109513
The present invention generally relates to binocular eyewear displays and more particularly to a method and apparatus for aligning the two images of a binocular eyewear display with respect to their vertical and horizontal orientation, and magnification.
Binocular displays include head mounted displays such as glasses and helmet mounted displays wherein a virtual image is presented to each eye. The image, usually created by a microdisplay, for example an LCD screen, may be presented to the eye by means of refractive or reflective optics, for example, through a lens system. Ideally the virtual images presented to each eye are perfectly aligned and the user perceives a single image similar to their perception of real images. If the virtual images are misaligned, the user may experience discomfort, for example, eye strain, headache, and nausea.
Commercial binocular eyewear are aligned mechanically during manufacture and some misalignment is common. Furthermore, misalignment of binocular eyewear may occur during use due to physical shock or exposure to temperature or humidity. Although there are no widely accepted standards for alignment, there have been several studies to determine acceptable values of binocular image alignment. A compilation of the desired alignment tolerances to avoid user discomfort is as shown in the following table as disclosed in Melzer & Moffitt, Head Mounted Displays—Designing for the User, New York: McGraw-Hill, 1997 (ISBN 0070418195).
Although vendors of commercial eyewear displays are aware of the need for binocular image alignment, products today are not shipped with any alignment specifications.
Systems have been disclosed wherein a user of the binocular eyewear may take corrective steps to bring the misalignment within certain tolerances. See for example, in US 2003/0184860, the user operates a device to move a dot until it is aligned with another dot, and in WO 2006/058188, the user adjusts first and second display panels until images of display panel indicia shown on the viewing screen are located relative to baseline indicia.
However, users of systems requiring user intervention to properly align the system may find it burdensome to perform such intervention, especially when it may be required each time the system is activated.
Accordingly, it is desirable to provide a method and apparatus for aligning the two images of a binocular eyewear display with respect to their vertical and horizontal orientation, and magnification. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
Embodiments of the present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.
Commercial binocular eyewear is aligned mechanically at manufacture and some misalignment is common. Alignment refers to the image presented to one eye being aligned with the image presented to the other eye. The illustration shown in
Mechanical means of alignment may involve mechanical adjustment of either the image source, for example a microdisplay, or by adjustment of optical components between the image source and the eye, for example a lens. Because of the very small image alignment tolerances, the required mechanical adjustment may be prohibitively expensive to execute during or after manufacture of the device. The mechanical precision required may be on the order of 1 micron to 1 mm depending on the mechanism used to make the adjustment. One limitation is that it can be difficult or expensive to realign the images after the device is manufactured because it may require disassembly and of the eyewear display and for some components to be debonded. Also, it is not possible to correct for misalignment that may result from changes in temperature at which the device operates.
Horizontal or vertical image alignment of the image presented to both eyes is accomplished by shifting pixels in one or both of the images presented by the image generating devices 704. In the chart below, it is shown that by shifting an image by one pixel shifts results in an angular change of 1.5 to 3.75 minutes of arc for the selected resolutions. This enables the very tight vertical and horizontal image alignment tolerances to be met simply through the electronic image adjustment. This chart uses values for a typical eyewear display with a 25 degree diagonal field of view with a 4:3 aspect ratio for the image.
Although adjustments for vertical and horizontal image alignment can be accomplished by shifting the image on a microdisplay, obtaining proper alignment with respect to rotation and magnification may be a more complex manipulation of the initial image. A microcomputer may be required to calculate the corrected image.
By measuring the optical misalignment, e.g., at the factory or subsequently at a sales or repair facility, and storing misalignment parameters such as vertical, horizontal, rotation, and magnification, in memory integral to the eyewear, correction may be made automatically without user interaction to bring the alignment within desired limits. A first image is presented to a first eye and a second image is presented to a second eye. A microcomputer may adjust at least one of the first and second images, e.g., by shifting or rotating the image, in accordance with the stored parameters. Additionally, the optical misalignment may be measured at a plurality of temperatures and humidity with the misalignment at each temperature and humidity stored. Subsequently, the misalignment at a current temperature and/or humidity may be adjusted in accordance with the stored values.
In a typical binocular optical system employed for head mounted displays, such as a see through optical system, one or more reflecting surfaces made of a solid inserted material, e.g., a mirror, are used to redirect the internally directed image. Several exemplary embodiments are described herein of an apparatus and method for redirecting and aligning this internally directed image with electrowetting technology that selectively redirects the image in an X and Y direction and selectively focuses the image. This method allows for alignment without complex hardware alignment systems.
A low cost reflective display technology, electrowetting light valves, may be used to produce an angled reflective surface. Typical electrowetting devices use a DC, or low frequency, voltage to change the wetting properties of a drop of oil in water in relation to a hydrophobic surface, thereby changing the position of the oil. The amount of the movement of the oil, and therefore the angle of reflection, depends on the magnitude of the applied voltage. Thus, a slight change in the angle of reflection may be accomplished by a change in the magnitude of the voltage.
In operation, without voltage applied, the layer of oil 516 is located in the optical path, and any applied image 528 is reflected back towards where it originated (
The angle of reflection is maintained by continual application of applied voltage. However, the leakage current is tremendously small, and a desired angle of reflection can be maintained for minutes after the voltage source 524 is disconnected. In the illustrated known display, voltage levels can alternatively be applied to the display 500 once to set the desired angle of reflection, and then they are re-applied at intervals (for example, 2 minutes), to refresh the charge.
These electrowetting devices described herein may be fabricated using known lithographic processes as follows. The fabrication of integrated circuits, microelectronic devices, micro electro mechanical devices, microfluidic devices, and photonic devices, involves the creation of several layers of materials that interact in some fashion. One or more of these layers may be patterned so various regions of the layer have different electrical or other characteristics, which may be interconnected within the layer or to other layers to create electrical components and circuits. These regions may be created by selectively introducing or removing various materials. The patterns that define such regions are often created by lithographic processes. For example, a layer of photoresist material is applied onto a layer overlying a wafer substrate. A photomask (containing clear and opaque areas) is used to selectively expose this photoresist material by a form of radiation, such as ultraviolet light, electrons, or x-rays. Either the photoresist material exposed to the radiation, or that not exposed to the radiation, is removed by the application of a developer. An etch may then be applied to the layer not protected by the remaining resist, and when the resist is removed, the layer overlying the substrate is patterned. Alternatively, an additive process could also be used, e.g., building a structure using the photoresist as a template.
Though various lithography processes, e.g., photolithography, electron beam lithography, and imprint lithography, ink jet printing, may be used to fabricate the light electrowetting device 500, a printing process is preferred. Ink compositions typically comprise four elements: 1) functional element, 2) binder, 3) solvent, and 4) additive. The binder, solvent and additives, together, are commonly referred to as the carrier which is formulated for a specific printing technology e.g. tailored rheology. The function of the carrier is the same for graphic arts and printed electronics: dispersion of functional elements, viscosity and surface tension modification, etc. A variety of printing techniques, for example, Flexo, Gravure, Screen, inkjet may be used. The Halftone method, for example, allows the full color range to be realized in actual printing.
Referring now to
The image generating device 704 may, for example, comprise an input (not shown) for wired or wireless coupling or an electronic device for receiving and reading video data from a DVD or the like. The optics system 706 includes a reflective surface 712 and optionally a lens 714 for displaying an image to an eye 716. It should be understood that there are many types of optical systems that may include, for example, mirrors and/or waveguides. It should be understood the present invention should not be limited by the type of image receiving device 704 or the type of optics system 706 described herein.
When an image, which typically would comprise a video stream, is received by the image receiving device 704, it is transmitted to the electrowetting device 708 which reflects the image to the reflective surface 712. The image then proceeds through the lens 714 for viewing.
The microcomputer 718 may be coupled between the image receiving device 704 and the electrowetting device 708 for determining necessary adjustments and for adjusting the voltage applied to the electrowetting device 708 and thereby modifying the angle of reflection. The microcomputer 718 may be integrated into the binocular display device 700 as shown or may reside elsewhere and be coupled electronically to the binocular display device 700. The microcomputer 718 may further include an environmental sensor for sensing, for example, the temperature and/or humidity, and wherein the voltage is adjusted for changes in temperature and/or humidity.
When the binocular display device 700 is fabricated, misalignment parameters are recorded. When an image is to be displayed, the microcomputer 718 retrieves these misalignment parameters and adjusts the voltage applied to the electrowetting device 708 to compensate for the misalignment of the binocular display device 700.
While it may be apparent that an electrowetting device described in
An alternative method to provide alignment in both the X and Y direction would be to employ the electrowetting device shown in
Referring to
This electrowetting focusing device 1300 is incorporated in the exemplary embodiment of a binocular display device 1500 as shown in
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.
