Beam-shaping device

Abstract

A beam shaping device ( 1; 31 ) comprising first ( 3; 33 ) and second ( 4; 37 ) optically transparent substrates, a liquid crystal layer ( 2; 36 ) sandwiched there between, and first ( 5; 34 ) and second ( 6; 35 ) electrodes arranged on a side of the liquid crystal layer ( 2; 36 ) facing the first substrate ( 3; 34 ). The beam shaping device ( 1; 31 ) is controllable between beam-shaping states, each permitting passage of light through the beam-shaping device in a direction perpendicular thereto. The beam shaping device ( 1; 31 ) is configured in such a way that application of a voltage (V) across the first ( 5; 34 ) and second ( 6; 35 ) electrodes results in an electric field having a portion essentially parallel to the liquid crystal layer ( 2; 36 ) in a segment thereof between neighboring portions of the electrodes ( 5, 6; 34; 35 ) and extending substantially from the first substrate ( 3; 34 ) to the second ( 4; 35 ) substrate. In this way a relatively high refractive index gradient can be obtained across short distances, which enables a very efficient beam shaping. The electric field can be achieved by utilizing electrodes provided on one side of the liquid crystal layer, in a so-called in-plane configuration. The device can be used in an autostereoscopic display device, for switching between 2D and 3D modes.

1 . A beam shaping device ( 1 ;  31 ) comprising first ( 3 ;  33 ) and second ( 4 ;  37 ) optically transparent substrates, a liquid crystal layer ( 2 ;  36 ) sandwiched there between, and first ( 5 ;  34 ) and second ( 6 ;  35 ) electrodes arranged on a side of said liquid crystal layer ( 2 ;  36 ) facing said first substrate ( 3 ;  34 ), wherein said beam shaping device ( 1 ;  31 ) is controllable between beam-shaping states, each permitting passage of light through said beam-shaping device in a direction perpendicular thereto, characterized in that said beam shaping device ( 1 ;  31 ) is configured in such a way that application of a voltage (V) across said first ( 5 ;  34 ) and second ( 6 ;  35 ) electrodes results in an electric field including a portion essentially parallel to said liquid crystal layer ( 2 ;  36 ) in a segment thereof between neighboring portions of said electrodes ( 5 ,  6 ;  34 ;  35 ) and extending substantially from said first substrate ( 3 ;  34 ) to said second ( 4 ;  35 ) substrate. 
   
   
       2 . A beam shaping device ( 1 ;  31 ) according to  claim 1 , wherein said first electrode ( 5 ;  34 ) comprises a first set ( 42   a ) of essentially parallel first electrode conductor lines, and said second electrode ( 6 ;  35 ) comprises a first set ( 42   b ) of essentially parallel second electrode conductor lines, said first and second electrodes ( 5 ,  6 ;  34 ,  35 ) being arranged such that at least one conductor pair including neighboring first and second electrode conductor lines is formed. 
   
   
       3 . A beam shaping device ( 31 ) according to  claim 2 , wherein said first electrode ( 34 ) further comprises a second set ( 43   a ) of essentially parallel first electrode conductor lines, and said second electrode ( 35 ) comprises a second set ( 43   b ) of essentially parallel second electrode conductor lines, said first and second electrodes being arranged such that at least one conductor pair including neighboring first and second electrode conductor lines is formed. 
   
   
       4 . A beam shaping device ( 31 ) according to  claim 3 , wherein said second sets ( 43   a, b ) of conductor lines are arranged at an angle with respect to said first sets ( 42   a, b ) of conductor lines. 
   
   
       5 . A beam shaping device ( 50 ) according to  claim 2  further comprising a third electrode ( 52 ) having at least one third electrode conductor line, and a fourth electrode ( 54 ) having at least one fourth electrode conductor line, arranged on an opposite side of said liquid crystal layer ( 2 ) with respect to said first ( 51 ) and second ( 53 ) electrodes. 
   
   
       6 . A beam shaping device ( 50 ) according to  claim 5 , wherein said third ( 52 ) and fourth ( 54 ) electrodes are arranged such that each of said third and fourth electrode conductor lines is essentially perpendicular with a corresponding one of said first ( 51 ) and second ( 53 ) electrode conductor lines. 
   
   
       7 . A beam shaping device ( 1 ) according to  claim 1 , wherein said liquid crystal layer ( 2 ) is homeotropically aligned when not subjected to an electric field. 
   
   
       8 . A beam shaping device ( 1 ) according to  claim 1 , wherein said liquid crystal layer ( 2 ) has a planar uniaxial alignment such that liquid crystal molecules comprised in said liquid crystal layer are perpendicular to an adjacent conductor line when not subjected to an electric field. 
   
   
       9 . A beam shaping arrangement ( 20 ;  30 ) comprising first ( 21 ;  31 ) and second ( 22 ;  32 ) beam shaping devices according to  claim 1  arranged in a stacked structure. 
   
   
       10 . A beam shaping arrangement ( 30 ) according to  claim 9 , wherein said first ( 31 ) and second ( 32 ) beam shaping devices are oriented in relation to each other such that at least a portion of first ( 34 ) and second ( 35 ) electrodes comprised in said first beam shaping device ( 31 ) are perpendicular to a corresponding portion of first ( 40 ) and second ( 41 ) electrodes comprised in said second beam shaping device ( 32 ). 
   
   
       11 . A beam shaping arrangement ( 20 ) according to  claim 9 , comprising a further optical member ( 23 ) adapted to alter a polarization state of a light beam passing through said beam-shaping arrangement ( 20 ). 
   
   
       12 . A lighting device comprising a beam shaping device according to  claim 1 , and a light-source, such as a light-emitting diode or a semiconductor laser, arranged such that a light beam emitted by said light-source passes through said beam shaping device. 
   
   
       13 . A device as claimed in  claim 1 , wherein the beam shaping device further comprises a layer between the first and second electrodes and the liquid crystal layer. 
   
   
       14 . A device as claimed in  claim 13 , wherein the distance between the neighboring portions of said electrodes wires is p, the thickness of the layer is d solid , the permittivity of a substrate in contact with the liquid crystal layer is ε sub  and the component of the permittivity of the liquid crystal material parallel to the extraordinary axis is ε LC , and wherein:
   0.7≦a1<12,     in which       a 1=ε LC   ×d   solid   /p.      
   
   
       15 . A device as claimed in  claim 14 , wherein 0.9<a2<3.6, in which
     a 2=ε LC /ε sub .   
   
   
       16 . A device as claimed in  claim 1 , further comprising a conductor layer on the opposite side of the liquid crystal layer to the first and second electrodes. 
   
   
       17 . A device as claimed in  claim 16 , further comprising a second insultator layer on the opposite side of the liquid crystal layer to the electrodes, the second insulator layer having a thickness d ground,  wherein:
   0.9<b1<14.4     and     0.4<b2<6.4,     in which       b 1=ε LC   ×d   solid   /p        and       b 2=ε LC   ×d   ground   /p.      
   
   
       18 . A device as claimed in  claim 16 , further comprising control means for applying a variable voltage to the conductor layer. 
   
   
       19 . A device as claimed in  claim 18 , wherein the control means is adapted to: apply a first ac voltage to the first electrode; and apply a second ac voltage to the second electrode. 
   
   
       20 . A device as claimed in  claim 19 , wherein the first and second ac voltages are in antiphase with the same frequency, and wherein the variable voltage has a different phase or higher frequency. 
   
   
       21 . A device as claimed in  claim 16 , further comprising control means for applying a dc voltage to the conductor layer, and wherein the control means is adapted to: apply a first ac voltage to the first electrode; and apply a second ac voltage to the second electrode. 
   
   
       22 . A device as claimed in  claim 21 , wherein the first and second ac voltages each comprise first and second superposed components, the first components of the first and second voltages being in antiphase with the same frequency, and the second components being the same and having a different phase or higher frequency. 
   
   
       23 . A device as claimed in  claim 1 , further comprising an opaque layer in the region of the electrodes and aligned with a region of lowest beam shaping effect, the opaque layer being opaque at least when the device is driven in the lensing mode. 
   
   
       24 . A device as claimed in  claim 23 , comprising an analyzer on the opposite side of the liquid crystal layer to the first and second electrodes, and the analyzer being configured such that in the lensing mode of the device, light traveling through the device and exiting the LC layer at the side of the analyzer at the position of electrodes is blocked at least partially by the analyzer. 
   
   
       25 . A switchable autostereoscopic display device comprising:
 a display panel having an array of display pixel elements for producing a display, the display pixel elements being arranged in rows and columns; and   an imaging arrangement which directs the output from different pixel elements to different spatial positions to enable a stereoscopic image to be viewed, arranged such that display pixel outputs for both eyes of a viewer are simultaneously directed,   wherein the imaging arrangement is electrically switchable between a 2D mode and a 3D mode and comprises a beam shaping device as claimed in  claim 1 .   
   
   
       26 . A method of controlling a beam shaping device ( 1 ;  31 ), the beam shaping device comprising first ( 3 ;  33 ) and second ( 4 ;  37 ) optically transparent substrates, a liquid crystal layer ( 2 ;  36 ) sandwiched there between, and first ( 5 ;  34 ) and second ( 6 ;  35 ) electrodes arranged on a side of said liquid crystal layer ( 2 ;  36 ) facing said first substrate ( 3 ;  34 ), wherein the method comprises:
 controlling the beam shaping device between beam-shaping states, each permitting passage of light through said beam-shaping device in a direction perpendicular thereto by applying a voltage (V) across said first ( 5 ;  34 ) and second ( 6 ;  35 ) electrodes thereby to generate an electric field including a portion essentially parallel to said liquid crystal layer ( 2 ;  36 ) in a segment thereof between neighboring portions of said electrodes ( 5 ,  6 ;  34 ;  35 ) and extending substantially from said first substrate ( 3 ;  34 ) to said second ( 4 ;  35 ) substrate.   
   
   
       27 . A method as claimed in  claim 26 , wherein the beam shaping device further comprises a conductor layer on the opposite side of the liquid crystal layer to the electrodes, and the method further comprises applying a first ac voltage to the first electrode and applying a second ac voltage to the second electrode. 
   
   
       28 . A method as claimed in  claim 27  further comprising applying a variable voltage to the conductor layer, and wherein the first and second ac voltages are in antiphase with the same frequency, and wherein the variable voltage has a different phase or higher frequency. 
   
   
       29 . A method as claimed in  claim 27 , further comprising applying a dc voltage to the conductor layer, and wherein the first and second ac voltages each comprise first and second superposed components, the first components of the first and second voltages being in antiphase with the same frequency, and the second components being the same and having a different phase or higher frequency. 
   
   
       30 . A method as claimed in  claim 26 , wherein the beam shaping device further comprises a conductor layer on the opposite side of the liquid crystal layer to the electrodes, and the method further comprises applying, within a time unit, a voltage to the conductor layer that is different from the average voltage applied to neighboring first and second electrodes. 
   
   
       31 . A method as claimed in  claim 26  for controlling the lens function of a lens of an autostereoscopic display device.