Lens unit and see-through type display apparatus including the same

Abstract

A see-through type display apparatus includes a see-through type optical system configured to transmit a first image via a first-path light, which is light traveling on a first path, to an ocular organ of a user, and a second image via a second-path light, which is light traveling on a second path, to the ocular organ of the user; and an incident light-dependent lens unit provided between the see-through type optical system and the ocular organ of the user and having different refractive powers according to characteristics of incident light, where the incident light-dependent lens unit has a positive first refractive power with respect to the first-path light and has a second refractive power different from the first refractive power with respect to the second-path light.

What is claimed is: 
     
         1 . A see-through type display apparatus comprising:
 a see-through type optical system configured to transmit a first image by a first-path light, which is light traveling on a first path, to an ocular organ of a user, and a second image by a second-path light, which is light traveling on a second path, to the ocular organ of the user; and   an incident light-dependent lens unit provided between the see-through type optical system and the ocular organ of the user and having different characteristics according to polarization directions of incident light,   wherein the incident light-dependent lens unit comprises:
 a first lens having a focal length varying according to the polarization directions of the incident light; and 
 a second lens joined to the first lens and having a constant focal length regardless of the polarization directions of the incident light. 
   
     
     
         2 . The see-through type display apparatus of  claim 1 , wherein the incident light-dependent lens unit is configured to function as a convex lens with respect to the first-path light and to function as a flat plate with respect to the second-path light. 
     
     
         3 . The see-through type display apparatus of  claim 1 , wherein the first lens has a positive first focal length with respect to the first-path light when the first-path light is incident on the first lens and has a first polarization direction,
 the first lens has a negative second focal length with respect to the second-path light when the second-path light is incident on the first lens and has a second polarization direction,   the second lens has a positive third focal length with respect to the first-path light when the first-path light is incident on the second lens and has the first polarization direction, and   the second lens has the positive third focal length with respect to the second-path light when the second-path light is incident on the second lens and has the second polarization direction.   
     
     
         4 . The see-through type display apparatus of  claim 3 , wherein an absolute value of the positive first focal length and an absolute value of the negative second focal length are equal to each other, and
 the absolute value of the negative second focal length and an absolute value of the positive third focal length are equal to each other.   
     
     
         5 . A compound lens unit comprising:
 a first lens having a focal length that varies according to polarization directions of incident light; and   a second lens joined to the first lens and having a constant focal length regardless of the polarization directions of the incident light.   
     
     
         6 . The compound lens unit of  claim 5 , wherein the first lens has a positive first focal length with respect to an incident light having a first polarization direction and has a negative second focal length with respect to an incident light having a second polarization direction, and
 the second lens has a positive third focal length with respect to the incident light having the first polarization direction and the incident light having the second polarization direction.   
     
     
         7 . The compound lens unit of  claim 6 , wherein an absolute value of the positive first focal length and an absolute value of the negative second focal length are equal to each other. 
     
     
         8 . The compound lens unit of  claim 6 , wherein an absolute value of the negative second focal length and an absolute value of the positive third focal length are equal to each other. 
     
     
         9 . The compound lens unit of  claim 5 , wherein the first lens is a flat plate type lens, and
 the second lens is a convex lens.   
     
     
         10 . The compound lens unit of  claim 5 , wherein the compound lens unit is configured to function as a convex lens with respect to an incident light having a first polarization direction and to function as a flat plate with respect to an incident light having a second polarization direction orthogonal to the first polarization direction.