The present invention relates generally to projection systems, and more specifically to scanned beam projection systems.
Polarizing beam splitters typically have qualities that enable the splitting of an electromagnetic beam into two orthogonally polarized beams. For simplicity, this description refers to electromagnetic beams as “light,” but the various embodiments of the invention are not limited to electromagnetic beams in the visible spectrum.
An example polarized beam splitter is shown at 100 in
Light beam 110 has P-polarized components 114 and S-polarized components 112, and has an angle of incidence α with respect to hypotenuse face 150. Angle of incidence (AOI) α is shown as 45 degrees in
In the following detailed description, reference is made to the accompanying drawings that show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. It is to be understood that the various embodiments of the invention, although different, are not necessarily mutually exclusive. For example, a particular feature, structure, or characteristic described herein in connection with one embodiment may be implemented within other embodiments without departing from the spirit and scope of the invention. In addition, it is to be understood that the location or arrangement of individual elements within each disclosed embodiment may be modified without departing from the spirit and scope of the invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims, appropriately interpreted, along with the full range of equivalents to which the claims are entitled. In the drawings, like numerals refer to the same or similar functionality throughout the several views.
Polarizing beam splitter 100 is described above with reference to
Polarization rotating component 420 has optical qualities such that two passes through the component results in a polarization rotation of substantially 90 degrees. For example, polarization rotating component 420 may be a quarter-wave retarder oriented such that it rotates a linearly polarized light beam by 90 degrees after two passes. The various embodiments of the present invention are not limited by the manner in which polarization rotating component 420 is implemented.
Scanning mirror 430 provides a reflective surface to reflect the light beam back through polarization rotating component 420 to hypotenuse face 150. In some embodiments, scanning mirror 430 scans back and forth in one or two dimensions such that the AOI at the hypotenuse face varies. In some embodiments, scanning mirror 430 is implemented as part of a micro-electronic machine (MEMS) device capable of scanning in one or two dimensions in response to drive electronics (not shown).
In operation, P-polarized light is sourced on a first path by polarized light source 410. Polarized light source 410 sources light that is P-polarized relative to the hypotenuse face 150. P-polarized light is polarized in the plane defined by the incoming light vector and a vector normal to the hypotenuse face.
The P-polarized light that passes through the hypotenuse face also passes through polarization rotating component 420. The polarization of the light emerging from polarization rotating component 420 is altered, as shown by the arrows crossing the light vector between polarization rotating component 420 and scanning mirror 430 in
As shown in
The S-polarized light reflects off hypotenuse face 150 and is directed away from the scanned beam display engine. In some embodiments, scanning mirror 430 changes its orientation such that the light reflected back to hypotenuse face 150 has an AOI that varies from angles smaller than 45 degrees to angles larger than 45 degrees. This is shown in
The scanned beam that is reflected from scanning mirror 430 is substantially S-polarized after passing through polarization rotating component 420, and so is substantially reflected by hypotenuse face 150, even though the AOI on the hypotenuse face varies. In some embodiments, the AOI on hypotenuse face varies from angles smaller than 45 degrees to angles larger than 45 degrees). In other embodiments, the AOI on hypotenuse face 150 takes on angles larger than 45 degrees, and in still other embodiments, the AOI on hypotenuse face 150 takes on angles smaller than 45 degrees. In all of these embodiments, the incident light is substantially S-polarized, and so it is substantially reflected off hypotenuse face 150.
Polarizing beam splitter plate 950 may be fabricated with optically transparent material such as glass or polymer, and may include a thin film coating to perform the polarizing beam split. In some embodiments, one face of polarizing beam splitter 950 includes the thin film coating, and in other embodiments the thin film coating is applied to an internal face that is created when two plates are bonded. The polarizing face of polarizing beam splitter plate 950 that transmits P-polarized light and reflects S-polarized light is referred to herein as a hypotenuse face for consistency with the terminology used for cube polarizing beam splitters. The hypotenuse face may or may not be an actual hypotenuse of a triangular shape.
The light path 902 from the polarized light source 410 is a P-polarized collimated beam that passes through polarizing beam splitter plate 950 and polarization rotating component 420. The light reflects off scanning mirror 430, passes back through polarization rotating component 420, and is incident on the hypotenuse face of polarizing beam splitter plate 950 at varying angles of incidence. This light is substantially S-polarized, and so is substantially 100% reflected.
The polarization rotating component 420 is shown at an angle such that any reflective surfaces are not normal to the light path, but this is not a limitation of the present invention. Reflected light 710 is shown redirected outside the image field of view.
Beam combining device 1010 may be any type of optical device having the desired properties. For example, beam combining device 1010 may be a dichroic filter or mirror, or dielectric mirror. Further, beam combining device 1010 may be manufactured using any suitable method, including thin film deposition methods.
Polarized light from both light sources 410 and 1020 are combined to create a composite P-polarized beam at 1002. This composite beam is then transmitted through the remainder of the scanned beam display engine as described above.
Optical beam processing device 1300 includes beam combining components 1310 and 1320 to combine laser light beams into a composite beam, a polarizing beam splitter hypotenuse face 1330 having optical qualities described above, and a polarization rotating component 1332 also having optical qualities as described above.
In operation, P-polarized green laser light enters device 1300 at face 1304, and is combined with P-polarized red laser light by beam combining component 1310. The P-polarized green/red laser light is combined with P-polarized blue laser light by beam combining component 1320 to create a composite P-polarized light beam. The composite P-polarized light beam is substantially 100% transmitted by hypotenuse face 1330, and passes through the polarization rotating component on face 1332. The light beam is reflected off scanning mirror 430, and arrives back at hypotenuse face 1330 as substantially S-polarized light. Scanning mirror 430 scans on two axes, causing the reflected beam to arrive at hypotenuse face 1330 at varying angles. The S-polarized light arriving at hypotenuse face 1330 at varying angles is substantially 100% reflected away from the scanned beam display engine.
In operation, P-polarized green laser light enters device 1400 at face 1404, and is reflected off reflector 1410. The P-polarized green light is then combined with P-polarized red laser light by beam combining component 1310. The P-polarized green/red laser light is combined with P-polarized blue laser light by beam combining component 1320 to create a composite P-polarized light beam. The composite P-polarized light beam is substantially 100% transmitted by hypotenuse face 1330, and passes through the polarization rotating component on face 1332. The light beam is reflected off scanning mirror 430, and arrives back at hypotenuse face 1330 as substantially S-polarized light. Scanning mirror 430 scans on two axes, causing the reflected beam to arrive at hypotenuse face 1330 at varying angles of incidence. The S-polarized light arriving at hypotenuse face 1330 at varying angles is substantially 100% reflected away from the scanned beam display engine.
The optical beam processing devices 1300 and 1400 include reflectors, beam combining components, polarizing beam splitter hypotenuse faces, and polarization rotating components separated by transparent media. In the examples of
The various components within the optical beam processing devices may be implemented as layers between the sections of transparent media. For example, each of the reflectors, beam combining components, hypotenuse face, and polarization rotating component may be thin film coatings that are applied to sections of transparent media prior to bonding.
As shown in
Various embodiments of the present invention are able to combine light from multiple color light sources, and project an image. The light sources may be laser diodes driven by currents that represent red, green, and blue radiance values for pixels in an image. The light is combined to create a composite beam that is directed at a scanning mirror that rotates on two axes to sweep the composite beam in both horizontal and vertical directions. In some embodiments, the beam may sweep back and forth horizontally in a sinusoidal pattern. Further, in some embodiments, the beam may sweep up and down vertically in a sinusoidal pattern. In general, the beam may be swept in any combination of horizontal and vertical patterns, including linear and non-linear patterns. Pixels may be displayed when the beam is sweeping in one direction or in both directions. For example, in some embodiments, pixels may be displayed as the beam sweeps down in the vertical direction, but not when the beam sweeps back up. Also for example, in some embodiments, pixels may be displayed as the beam sweeps down as well as when the beam sweeps up in the vertical direction.
By passing a P-polarized composite beam through a polarizing beam splitter at a substantially constant angle, and reflecting the scanned S-polarized composite beam at various angles, the characteristics of polarized beam splitters can be used to great advantage, while reducing energy loss.
In general, polarizing beam splitters in the various embodiments of the present invention may be oriented to direct light away from scanned beam display engines in any direction. For example, polarizing beam splitter 1550 can point in any direction as long as the scanned beam arrives at the polarizing beam splitter substantially P-polarized.
Although previous figures show one, two, and three light sources, the various embodiments of the present invention are not so limited. For example, any number of light sources may be utilized without departing from the scope of the present invention.
Mobile device 1600 includes laser projector 1601 to create an image with light 1608. Similar to other embodiments of projection systems described above, mobile device 1600 may include a scanned beam display engine with a polarizing beam splitter, a polarization rotating component, and a scanning mirror to accomplish high efficiency image generation.
In some embodiments, mobile device 1600 includes antenna 1606 and electronic component 1605. In some embodiments, electronic component 1605 includes a receiver, and in other embodiments, electronic component 1605 includes a transceiver. For example, in GPS embodiments, electronic component 1605 may be a GPS receiver. In these embodiments, the image displayed by laser projector 1601 may be related to the position of the mobile device. Also for example, electronic component 1605 may be a transceiver suitable for two-way communications. In these embodiments, mobile device 1600 may be a cellular telephone, a two-way radio, a network interface card (NIC), or the like.
Mobile device 1600 also includes memory card slot 1604. In some embodiments, a memory card inserted in memory card slot 1604 may provide a source for video data to be displayed by laser projector 1601. Memory card slot 1604 may receive any type of solid state memory device, including for example, Multimedia Memory Cards (MMCs), Memory Stick DUOs, secure digital (SD) memory cards, and Smart Media cards. The foregoing list is meant to be exemplary, and not exhaustive.
Method 1700 is shown beginning with block 1710 in which a light beam is passed through a hypotenuse face of a polarizing beam splitter, where the light beam includes P-polarized light with respect to the hypotenuse face. In some embodiments, the hypotenuse face may be a face in a cube polarizing beam splitter or a polarizing beam splitter plate. In other embodiments, the hypotenuse face may be part of an optical beam processing device, such as those shown in previous figures.
In some embodiments, the light beam has a substantially constant angle of incidence on the hypotenuse face. For example, in some embodiments, the light beam has an angle of incidence of substantially 45 degrees. In other embodiments, the light beam has an angle of incidence of other than 45 degrees.
The light may be monochromatic visible light, or may be visible light that includes multiple colors. Further, the light may be a composite collimated beam such as those shown above in
At 1720, the light beam is passed through a polarization rotating component that has optical qualities such that two passes through the polarization rotating component rotates a polarization of the light beam by substantially 90 degrees. In some embodiments, the polarization rotating component may be a quarter-wave retarder or the like. The polarization rotating component may be implemented in any manner, including as a thin film on a face of transparent media such as glass or polymer. In some embodiments, the polarization rotating component is positioned such that no reflective surfaces are orthogonal to the light path to keep reflected light out of the image field of view.
At 1730, the light beam is reflected off a scanning mirror back to the polarization rotating component, and at 1740, the light beam is passed back through the polarization rotating component to create an S-polarized light beam. The scanning mirror may rotate on one or two axes to scan the light beam back and forth and up and down as it passes back through the polarization rotating component and hits the hypotenuse face. Accordingly, the angle of incidence on the hypotenuse face is not substantially constant. In some embodiments, the angle of incidence varies from angles smaller than 45 degrees to angles larger than 45 degrees. In other embodiments, the angle of incidence varies at angles above 45 degrees, and in still further embodiments, the angle of incidence varies at angles below 45 degrees.
At 1740, the scanned S-polarized light beam is reflected off the hypotenuse face away from the scanned beam display engine. The reflected light may produce an image. For example, in some embodiments, the polarized light is produced by color laser diodes that produce color light at various intensities that correspond to individual pixels in an image, and the scanning mirror scans the beam so that the individual pixels are displayed in various locations within a scan pattern. A laser projection system results.
Although the present invention has been described in conjunction with certain embodiments, it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art readily understand. Such modifications and variations are considered to be within the scope of the invention and the appended claims.