Lamp unit, vehicular lamp system

Abstract

To obtain projection images with high contrast when selective light irradiation is performed forward of its own vehicle. A lamp unit for a vehicular lamp system performing selective light irradiation to the surroundings of the own vehicle includes: a light source; an optical shutter part that modulates light emitted from the light source; and an optical system that projects the light transmitted through the optical shutter part. The optical shutter part includes: polarizers; a liquid crystal element disposed between the polarizers and where the initial alignment of liquid crystal molecules is horizontally aligned and causes an alignment change in the in-plane direction upon electric field application; a first optical plate which is a positive A-plate disposed between the polarizers closer to the light source and the liquid crystal element; and a second optical plate which is a positive C-plate disposed between the first optical plate and the liquid crystal element.

What is claimed is: 
     
         1 . A lamp unit used for a vehicular lamp system that performs selective light irradiation to the surroundings of a vehicle comprising:
 a light source;   an optical shutter part that modulates light emitted from the light source; and   an optical system that projects the light transmitted through the optical shutter part;   wherein the optical shutter part comprises:   a pair of polarizers;   a liquid crystal element disposed between the pair of polarizers and in which the initial alignment of liquid crystal molecules is horizontally aligned and causes an alignment change in the in-plane direction upon application of an electric field;   a first optical plate which is a positive A-plate disposed between one of the pair of polarizers closer to the light source and the liquid crystal element; and   a second optical plate which is a positive C-plate disposed between the first optical plate and the liquid crystal element.   
     
     
         2 . The lamp unit according to  claim 1 ,
 wherein the pair of polarizers are arranged such that their absorption axes are substantially orthogonal to each other;   the liquid crystal element is disposed such that the alignment direction of the initial alignment is substantially parallel to any one of the absorption axes of the pair of polarizers; and   the first optical plate has its slow axis arranged substantially parallel to the alignment direction of the initial alignment of the liquid crystal element.   
     
     
         3 . The lamp unit according to  claim 1 ,
 wherein the pair of polarizers are absorption type polarizers or wire grid polarizers.   
     
     
         4 . The lamp unit according to  claim 2 ,
 wherein the second optical plate is disposed such that its optical axis is in the thickness direction (light traveling direction).   
     
     
         5 . The lamp unit according to  claim 2 ,
 wherein the liquid crystal element is configured to use a positive dielectric anisotropy Δε and contains no chiral material, or a nematic liquid crystal material having a negative dielectric anisotropy Δε.   
     
     
         6 . The lamp unit according to  claim 3 ,
 wherein the liquid crystal element is configured to use a positive dielectric anisotropy Δε and contains no chiral material, or a nematic liquid crystal material having a negative dielectric anisotropy Δε.   
     
     
         7 . A vehicular lamp system comprising:
 the lamp unit according to  claim 1 ;   a detecting part for detecting a target object present surrounding the vehicle; and   a driving part which sets the light distribution pattern according to the position of the target object and drives the lamp unit.   
     
     
         8 . The vehicular lamp system according to  claim 7 ,
 wherein the pair of polarizers are arranged such that their absorption axes are substantially orthogonal to each other;   the liquid crystal element is disposed such that the alignment direction of the initial alignment is substantially parallel to any one of the absorption axes of the pair of polarizers; and   the first optical plate has its slow axis arranged substantially parallel to the alignment direction of the initial alignment of the liquid crystal element.   
     
     
         9 . The vehicular lamp system according to  claim 7 ,
 wherein the pair of polarizers are absorption type polarizers or wire grid polarizers.   
     
     
         10 . The vehicular lamp system according to  claim 8 ,
 wherein the second optical plate is disposed such that its optical axis is in the thickness direction (light traveling direction).   
     
     
         11 . The vehicular lamp system according to  claim 8 ,
 wherein the liquid crystal element is configured to use a positive dielectric anisotropy Δε and contains no chiral material, or a nematic liquid crystal material having a negative dielectric anisotropy Δε.   
     
     
         12 . The vehicular lamp system according to  claim 9 ,
 wherein the liquid crystal element is configured to use a positive dielectric anisotropy Δε and contains no chiral material, or a nematic liquid crystal material having a negative dielectric anisotropy Δε.   
     
     
         13 . The vehicular lamp system according to  claim 10 ,
 wherein the liquid crystal element is configured to use a positive dielectric anisotropy Δε and contains no chiral material, or a nematic liquid crystal material having a negative dielectric anisotropy Δε.   
     
     
         14 . The vehicular lamp system according to  claim 7 ,
 wherein the detecting part is a camera which captures an image in front of the vehicle.