Display, instrument panel, optical system and optical instrument

Abstract

A multiple depth display provided for displaying images at different depths comprises a single display device ( 61 ), for displaying all of the images. An optical system ( 62, 63, 64 ) is disposed in front of the display device ( 61 ). The optical system comprises first and second spaced-apart partial reflectors ( 62, 63 ) and polarization optics ( 64 ) for providing first and second light paths for first and second images or sequences of images displayed by the device ( 61 ). The first light path ( 65 ) comprises partial transmission through the first reflector ( 62 ), partial reflection from the second reflector ( 63 ), partial reflection from the first reflector ( 62 ), and partial transmission through the second reflector ( 65 ) towards a viewing region.

1 . An optical system for providing a first light path which is longer than a physical length of the system,
 said optical system comprising first and second spaced-apart partial reflectors and providing the first light path for a first light incident on the first reflector,   the first light path comprising at least partial transmission through the first reflector towards the second reflector, at least partial reflection from the second reflector towards the first reflector, at least partial reflection from the first reflector towards the second reflector, and at least partial transmission through the second reflector,   the optical system being arranged substantially to prevent emission from the second reflector of the first light not reflected during reflection by the first and second reflectors,   wherein light incident on the second partial reflector for the first time does not leave the optical system.   
     
     
         2 . A system as claimed in  claim 1 , in which the optical system is arranged to change the polarization of the first light during passage along the first path. 
     
     
         3 . A system as claimed in  claim 2 , in which the optical system is arranged to change the polarization of the first light during passage along the first path between incidence on the second reflector and reflection from the first reflector. 
     
     
         4 . A system as claimed in  claim 1 , in which the optical system is arranged to provide a second light path of length different from that of the first path. 
     
     
         5 . A system as claimed in  claim 4 , in which the second light path comprises at least partial transmission through the first reflector towards the second reflector and at least partial transmission through the second reflector. 
     
     
         6 . A systems claimed in  claim 5 , in which the optical system is arranged substantially to prevent emission from the second reflector of the second light not transmitted by the second reflector. 
     
     
         7 . A system as claimed in  claim 4 , in which the optical system is switchable between a first mode, in which the first light propagates along the first light path, and a second mode, in which light propagates along the second light path. 
     
     
         8 . A system as claimed in  claim 1 , in which the first and second reflectors are substantially plane. 
     
     
         9 . A system as claimed in  claim 1 , in which the first and second reflectors are substantially parallel. 
     
     
         10 . A system as claimed in  claim 1 , in which the first and second reflectors comprise a reflective linear polariser and a partially transmissive mirror, respectively, and the optical system comprises: a circular polariser with the second reflector disposed between the first reflector and the circular polariser; a quarter wave plate disposed between the first and second reflectors; and a switchable half wave plate disposed between the first reflector and the circular polariser. 
     
     
         11 . A system as claimed in  claim 1 , in which the first and second reflectors comprise a partially transmissive mirror and at least one reflective circular polariser, respectively. 
     
     
         12 . A system as claimed in  claim 11 , in which the optical system comprises a quarter wave plate. 
     
     
         13 . A system as claimed in  claim 12 , in which the optical system comprises a switchable half wave plate. 
     
     
         14 . An optical instrument comprising a system as claimed in  claim 1 . 
     
     
         15 . An instrument as claimed in  claim 14 , comprising any one of a telescope, a monocular, a pair of binoculars and a camera. 
     
     
         16 . A display comprising a display device for modulating a first light with a first image or sequence of images and an optical system arranged to increase the perceived depth of the location of the first image or sequence, the optical system comprising first and second spaced-apart partial reflectors and providing a first light path for the first light from the device to a viewing region, the first light path comprising at least partial transmission through the first reflector towards the second reflector, at least partial reflection from the second reflector towards the first reflector, at least partial reflection from the first reflector towards the second reflector, and at least partial transmission through the second reflector towards the viewing region. 
     
     
         17 . A display as claimed in  claim 16 , in which the optical system is arranged substantially to prevent transmission to the viewing region of the first light not reflected during reflection by the first and second reflectors 
     
     
         18 . A display as claimed in  claim 16 , in which the optical system is arranged to change the polarization of the first light during passage along the first path. 
     
     
         19 . A display as claimed in  claim 18 , in which the optical system is arranged to change the polarization of the first light during passage along the first path between incidence on the second reflector and reflection from the first reflector. 
     
     
         20 . A display as claimed in  claim 16 , in which the device is arranged to modulate a second image or sequence of images and the optical system is arranged to provide a second light path from the device to the viewing region of length different from that of the first path to provide a perceived depth of location of the second image or sequence different from that of the first image or sequence. 
     
     
         21 . A display as claimed in  claim 20 , in which the second light path comprises at least partial transmission through the first reflector towards the second reflector and at least partial transmission through the second reflector towards the viewing region. 
     
     
         22 . A display as claimed in  claim 21 , in which the optical system is arranged substantially to prevent transmission to the viewing region of the second light not transmitted by the second reflector. 
     
     
         23 . A display as claimed in  claim 20 , in which the display is switchable between a first mode displaying the first image or sequence and a second mode displaying the second image or sequence to change the perceived depth of image location. 
     
     
         24 . A display as claimed in  claim 20 , in which the display is arranged to display the first and second images or sequences simultaneously or time-sequentially to give the appearance of one of the first and second images or sequences overlaid above the other of the first and second images or sequences. 
     
     
         25 . A display as claimed in  claim 16 , in which the first and second reflectors are substantially plane. 
     
     
         26 . A display as claimed in  claim 16 , in which the first and second reflectors are substantially parallel. 
     
     
         27 . A display as claimed in  claim 26 , in which the first and second reflectors are substantially parallel to a display surface of the device. 
     
     
         28 . A display as claimed in  claim 16 , in which the device comprises a liquid crystal device. 
     
     
         29 . A display as claimed in  claim 16 , in which the first and second reflectors overlie substantially the whole of an image displaying region of the device. 
     
     
         30 . A display as claimed in any one of  claim 16 , in which the first and second reflectors comprise a reflective linear polariser and a partially transmissive mirror, respectively, disposed between the device and a circular polariser and the optical system comprises a quarter wave plate disposed between the first and second reflectors and a switchable half wave plate disposed between the first reflector and the circular polariser. 
     
     
         31 . A display as claimed in  claim 16 , in which the first and second reflectors comprise a partially transmissive mirror and at least one reflective circular polariser, respectively. 
     
     
         32 . A display as claimed in  claim 31 , in which the optical system comprises a quarter wave plate. 
     
     
         33 . A display as claimed in  claim 32 , in which the optical system comprises a switchable half wave plate. 
     
     
         34 . A display as claimed in  claim 16 , in which the first and second reflectors comprise a partially transmissive mirror and a reflective linear polariser, respectively, and the optical system comprises a quarter wave plate disposed between the first and second reflectors and a patterned retarder or polarization rotator disposed between the first reflector and the device. 
     
     
         35 . A display as claimed in  claim 34 , comprising a collimated backlight and in which the optical system comprises a diffuser. 
     
     
         36 . A display as claimed in  claim 35 , in which the partially transmissive mirror comprises a mirror having an array of apertures and the diffuser comprises an array of lenses aligned with the apertures. 
     
     
         37 . A display as claimed in  claim 33 , in which the patterned retarder or rotator is switchable to a uniform unpatterned state. 
     
     
         38 . A display as claimed in  claim 33 , in which the patterned retarder or rotator comprises a patterned quarter wave plate. 
     
     
         39 . A display as claimed in  claim 34 , in which the patterned retarder or rotator comprises a uniform quarter wave plate and a patterned half wave plate or patterned 90° polarisation rotator. 
     
     
         40 . A display as claimed in  claim 34 , in which the patterned retarder or rotator comprises a liquid crystal cell. 
     
     
         41 . A display as claimed in  claim 40 , in which the liquid crystal cell comprises a patterned electrode arrangement.