Abstract:
A planar line generator including a first planar surface extending in a first direction, a second planar surface facing the first planar surface, and a beam splitter in front of the second planar surface, the beam splitter configured to output, from light incident thereon, an undeflected beam, a first beam deflected to a first side of the undeflected beam along the first direction, and a second beam deflected to a second side of the undeflected beam along the first direction, wherein the second planar surface includes a line diffuser configured to receive the undeflected beam, and first and second diffusers having a design different from the line diffuser, the first and second diffusers being configured to receive the first and second beams, respectively.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/953,412, filed on Mar. 14, 2014, and entitled: “Planar High Angle Line Generator,” which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND 
       [0002]    1. Field 
         [0003]    One or more embodiments described herein relate to a planar high angle degree line generator. 
         [0004]    2. Description of the Related Art 
         [0005]    Some applications require a curtain of illumination to be provided on a user, e.g., to detect motion, recognize gestures, and so forth. In order to accurately process the information about the user, a fair amount of power may be required to illuminate the user. Thus, diffusers may be employed to insure uniform and safe illumination with sufficient power. Existing planar line generators are typically limited to about 100 degrees, with extreme roll off with increasing angle. There are effective limitations due to Snell&#39;s law for refractive diffusers and obliquity for diffractive diffusers that curtail projected power at angles above about 50 degrees off axis, i.e., along the optical axis, e.g., for a total angular extent of 100 degrees. 
       SUMMARY 
       [0006]    One or more embodiments is directed to a planar line generator including a first planar surface extending in a first direction, a second planar surface facing the first planar surface, and a beam splitter in front of the second planar surface, the beam splitter configured to output, from light incident thereon, an undeflected beam, a first beam deflected to a first side of the undeflected beam along the first direction, and a second beam deflected to a second side of the undeflected beam along the first direction, wherein the second planar surface includes a line diffuser configured to receive the undeflected beam, and first and second diffusers having a design different from the line diffuser, the first and second diffusers being configured to receive the first and second beams, respectively. 
         [0007]    The first planar surface and the second planar surface may be on a single substrate. 
         [0008]    The first planar surface may be on a first substrate and the second planar surface may be on a second substrate. 
         [0009]    The planar line generator may include a gap between the beam splitter and the line diffuser, the first and second beams being reflected at an interface between the first substrate and the gap. The second substrate may include an indent providing the gap. The first and second beams reflected from the first planar surface, after being reflected at the interface, may avoid the gap. 
         [0010]    The first and second beams may be incident on the first and second diffusers twice, respectively. The planar line generator may inlcude first and second reflective surfaces receiving the first and second beams reflected from the first and second diffusers and reflecting the first and second beams back on to the first and second diffusers, respectively. The first and second reflective surfaces may be reflective diffractive optical elements. The first and second reflective surfaces may be between the first and second substrates. The first and second beams are reflected between the second and first planar surfaces before being incident on the first and second diffusers. Reflections may be due to total internal reflection. 
         [0011]    The first and second diffusers may output asymmetric beams. The first beam may be output from the first diffuser as a first asymmetric beam having evanescent zero and negative orders, and the second beam may be output from the second diffuser as a second asymmetric beam having evanescent zero and positive orders. The asymmetric beams may combine with a symmetric beam output from the line diffuser to realize a line having a higher angle than that output from the line diffuser. 
         [0012]    The first and second diffusers have the same design in symmetric configuration. 
         [0013]    The beam splitter may be on the first planar surface. 
         [0014]    The beam splitter may be between the first planar surface and the second planar surface. 
         [0015]    One or more embodiments is directed to a planar line generator including a first planar surface including extending in a first direction, a second planar surface facing the first planar surface, and a beam splitter on the first planar surface or between the first planar surface and the second planar surface, the beam splitter being configured to output, from light incident thereon, an undeflected beam, a first beam deflected to a first side of the undeflected beam along the first direction, and a second beam deflected to a second side of the undeflected beam along the first direction, the second planar surface including a symmetric diffuser configured to receive the undeflected beam and output a symmetric beam, and first and second asymmetric diffusers, the first and second asymmetric diffusers being configured to receive the first and second beams, respectively, and output first and second asymmetric beams. 
         [0016]    The first beam may be output from the first asymmetric diffuser as a first asymmetric beam having evanescent zero and negative orders, and the second beam may be output from the second asymmetric diffuser as a second asymmetric beam having evanescent zero and positive orders. 
         [0017]    The symmetric diffuser may be a line diffuser. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    Features and advantages will become apparent to those of skill in the art by describing in detail exemplary embodiments with reference to the attached drawings, in which: 
           [0019]      FIG. 1  illustrates a schematic side view of a planar high angle line generator in accordance with a first embodiment; 
           [0020]      FIG. 2  illustrates a schematic side view of a planar high angle line generator in accordance with a second embodiment; 
           [0021]      FIG. 3  illustrates a schematic side view of a planar high angle line generator in accordance with a third embodiment; and 
           [0022]      FIG. 4  illustrates a schematic side view of a planar high angle line generator in accordance with a fourth embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. As used herein, a high angle line generator refers to a generator that outputs a line, e.g., substantially uniform light with an angular extent of greater than 120 degrees in on axis, i.e., ±60 degrees relative to the optical axis, and less than 1 degree in the orthogonal axis. 
         [0024]      FIG. 1  illustrates a schematic side view of a planar high angle line generator  100  in accordance with a first embodiment. As shown therein, the planar high angle line generator  100  may include a first planar surface  110  and a second planar surface  120 , facing the first planar surface and receiving light output from the first planar surface  110 . The first and second planar surfaces  110 ,  120  may be opposite surfaces of a single, e.g., the same, substrate  130 , i.e., the planar high angle line generator  100  may be monolithic. The first and second planar surfaces  110 ,  120  may extend along a first direction and the input light may be incident on the first planar surface  110  along a second direction, orthogonal to the first direction. 
         [0025]    The first planar surface  110  may include a beam splitter  112 , e.g., a 3×1 grating, which, when an input beam IB is incident thereon, outputs a zero order or undeflected beam B 0 , a first deflected beam B 1 , e.g., a +1 order beam, and a second deflected beam B 2 , e.g., a −1 order beam. Thus, the first and second deflected beams are on opposite sides of the undeflected beam B 0  along the first direction. 
         [0026]    The undeflected beam B 0  propagates through the substrate  130  towards the second planar surface  120  along the second direction to be incident on a line diffuser  122 . The line diffuser  122  outputs a beam B 0 S that is symmetric with respect to the second direction about a zero order output from the line diffuser  122 . As can be seen therein, the line diffuser  122  alone does not generate a high angle line. Single surface linear diffusers are limited to about 100 degrees full angle. 
         [0027]    The first and second deflected beams B 1 , B 2  propagate at an angle to the second direction in, e.g., within, the substrate  130 . The material of the substrate  130  and the angles of the first and second deflected beams B 1 , B 2  may be selected such that the first and second deflected beams are reflected at the second planar surface  120  due to total internal reflection, back towards the first planar surface  110 , where the first and second deflected beams are again totally reflected back towards first and second diffusers  124 ,  126  on the second planar surface  120 . 
         [0028]    Alternatively, instead of relying on total internal reflection, a mirror could be provided on the first and second planar surfaces  110 ,  120  to direct the first and second beams B 1 , B 2  onto the first and second diffusers, respectively. Reflection within the substrate  130  may be used to increase spacing between the line diffuser  122  and the first and second diffusers  124 ,  126  or to increase the size of the planar high angle line generator  100  for other reasons, e.g., ease of alignment to other elements. Alternatively, if the substrate  130  is thick enough along the second direction to provide sufficient separation between the line diffuser  122  and the first and second diffusers  124 ,  126 , the first and second beams may propagate directly from the beam splitter  112  to the first and second diffusers  124 ,  126 . 
         [0029]    These first and second diffusers  124 ,  126  may have a same design and be of a design other than a line diffuser. For example, the first and second diffusers may have a roll-off that is 1-D Gaussian or super-Gaussian. Such first and second diffusers may be realized using a two-phase level diffractive. Beams B 1 A and B 2 A output from the first and second diffusers  124 ,  126  will have the zero-th order and half the orders that are evanescent and thus do not propagate. In particular, the first asymmetric beam B 1 A has evanescent zero and negative orders and the second asymmetric beam B 2 A has evanescent zero and positive orders. Most of the evanescent behavior of light output from the first and second diffusers  124 ,  126  is due to the high incident angle. Thus, the beams B 1 A and B 2 A will be asymmetric with respect to the second direction about a zero order output from the first and second diffusers  124 ,  126 . 
         [0030]    The asymmetric beams B 1 A and B 2 A combine with the symmetric beam BS 0  to provide a high angle line, i.e., a line having a higher angle than realized by the symmetric beam BS 0  alone. The use of the asymmetric outputs allows distortion to be compensated and roll-off to be corrected. 
         [0031]      FIG. 2  illustrates a schematic side view of a planar high angle line generator  200  in accordance with a second embodiment. As shown therein, the planar high angle line generator  200  may include a first planar surface  210  and a second planar surface  220 , facing the first planar surface  210  and receiving light output from the first planar surface  210 . The first and second planar surfaces  210 ,  220  may extend along a first direction and the input light may be incident on the first planar surface  210  along a second direction, orthogonal to the first direction. 
         [0032]    Different from the first embodiment, the first planar surface  210  may be on a first planar substrate  230  and the second planar surface  220  may be on a second substrate  240 , different from the first substrate  230 , that includes an indent  245  providing a gap  250  between the beam splitter  112  and the line diffuser  122 . This gap  250  may be filled with air, an index matching polymer therein, or glass such that the higher orders output by the beam splitter  112  are reflected back towards the first planar surface  210  to provide separation of the orders. 
         [0033]    As can be seen in  FIG. 2 , the undeflected beam B 0  passes through the indent  245  to be incident on the line diffuser  122 . The first and second deflected beams B 1  and B 2  may be reflected back toward the first planar surface  210 , where they are reflected, either due to total internal reflection or a reflective material provided on the first planar surface  210 , back toward the second planar surface  220  onto the first and second diffusers  124 ,  126  thereon. This configuration allows for a thinner, i.e., in the second direction, overall planar high angle line generator  200 . 
         [0034]      FIG. 3  illustrates a schematic side view of a planar high angle line generator  300  in accordance with a third embodiment. As shown therein, the planar high angle line generator  300  may include a first planar surface  310  and a second planar surface  320 , facing the first planar surface  310  and receiving light output from the first planar surface  310 . The first and second planar surfaces  310 ,  320  may extend along a first direction and the input light IB may be incident on the first planar surface  310  along a second direction, orthogonal to the first direction. 
         [0035]    Like the second embodiment, the first planar surface  310  may be on a first planar substrate  330  and the second planar surface  320  may be on a second substrate  340  that includes an indent  345  providing a gap  350  between the beam splitter  112  and the line diffuser  122 . This gap  350  may be filled with air, an index matching polymer, or glass such that the higher orders output by the beam splitter  112  to be reflected back towards the first planar surface  310  to provide separation of the orders. 
         [0036]    Different from the second embodiment, the planar high angle line generator  300  may include an embedded reflective surface or reflective diffractive optical element (DOE)  360  in either the first substrate  330  or the second substrate  340 . Thus, if there are significant reflections from diffusers  324 ,  326 , this embedded reflective  360  will reflect light back towards extended or segmented diffusers  324 ,  326  for improved efficiency, such that the first and second diffusers  324 ,  326  output a total of four asymmetric beams Ba 1   a , B 1 Ab, B 2 Aa, and B 2 Ab. Alternatively, if the second substrate  340  is thin, a reflective  360 ′ may be provided on the first planar surface  310 . When a reflective DOE is used, the DOE may be designed to perform additional beam steering or provide an alternate diffusion function. 
         [0037]      FIG. 4  illustrates a schematic side view of a planar high angle line generator  400  in accordance with a fourth embodiment. As shown therein, the planar high angle line generator  400  may include a first planar surface  410  and a second planar surface  420 , facing the first planar surface  410  and receiving light output from the first planar surface  410 . The first and second planar surfaces  410 ,  420  may extend along a first direction and the input light IB may be incident on the first planar surface  410  along a second direction, orthogonal to the first direction. 
         [0038]    Like the second and third embodiments, the first planar surface  410  may be on a first planar substrate  430  and the second planar surface  420  may be on a second substrate  440 . However, unlike the second and third embodiments, there is no indent providing a gap between the beam splitter and the line diffuser. Instead a beam splitter  412  is in either the first substrate  430  or the second substrate  440 . 
         [0039]    By way of summation and review, by providing diffusers outputting asymmetric beams on opposite sides of a line diffuser in accordance with embodiments, roll-off and distortion of the line diffuser may be compensated, resulting in a high angle line. By using a beam splitter on a first planar surface and such diffusers on a second planar surface facing the first planar surface, the high angle line may be simply realized. 
         [0040]    Embodiments of the present invention have been disclosed herein and, although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. For example, the indent may be in the first substrate or partially provided in both the first and second substrates. Also, light propagating in the substrate or substrates may be emitted at the edge of the device and contribute to the intensity of the line at higher deflected angles. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.