Diffractive optical element and method for manufacturing same

Abstract

A diffractive optical element includes at least a first diffractive element and a second diffractive element. The conditional expression 0.5≦D/DS≦0.9 is preferably satisfied where DS denotes the summation of the optimum designed groove height of the first diffractive element d1S and that of the second diffractive element d2S, and D denotes the summation of an actual groove height of the first diffractive element d1 and that of the second diffractive element d2. At least one of the first diffractive element and the second diffractive element is made of glass. At least one of the first diffractive element and the second diffractive element is made of resin. The optimum designed value of groove heights of the diffractive optical element are determined so as to satisfy a condition for correcting chromatic aberration at both d-line and g-line.

What is claimed is:  
     
         1 . A diffractive optical element comprising: 
 at least a first diffractive element and a second diffractive element, wherein    the following conditional expression is satisfied:    0.5≦D/DS≦0.9    where DS denotes a summation of optimum designed groove heights of the diffractive optical elements, and D denotes a summation of actual groove heights of the diffractive optical elements.    
     
     
         2 . The diffractive optical element according to  claim 1 , wherein at least one of the first diffractive element and the second diffractive element is made of glass.  
     
     
         3 . The diffractive optical element according to  claim 2 , wherein at least one of the first diffractive element and the second diffractive element is made of resin.  
     
     
         4 . The diffractive optical element according to  claim 3 , wherein the optimum designed groove heights of the diffractive optical elements are determined so as to satisfy a condition for correcting chromatic aberration at both d-line and g-line.  
     
     
         5 . The diffractive optical element according to  claim 2 , wherein the optimum designed groove heights of the diffractive optical elements are determined so as to satisfy a condition for correcting chromatic aberration at both d-line and g-line.  
     
     
         6 . The diffractive optical element according to  claim 1 , wherein at least one of the first diffractive element and the second diffractive element is made of resin.  
     
     
         7 . The diffractive optical element according to  claim 6 , wherein the optimum designed groove heights of the diffractive optical elements are determined so as to satisfy a condition for correcting chromatic aberration at both d-line and g-line.  
     
     
         8 . A diffractive optical element comprising: 
 a first diffractive element and a second diffractive element: and    the first and second diffractive elements being made of different materials with each other, closely laminated with each other to form grooves of a diffraction grating having a predetermined shape at the cemented surface of the first and the second diffractive elements;    wherein one of these diffractive elements is made of material for molding and the other diffractive element is made of ultraviolet-curable resin; and    wherein the following conditional expression is satisfied:    7.0 μm≦h≦18.0 μm    where h denotes the groove height of the diffraction grating.    
     
     
         9 . The diffractive optical element according to  claim 8 , wherein the material for molding is glass and the following conditional expressions are satisfied:  
       1.55≦ndG≦1.65 55νdG≦65 1.50≦ndR≦1.60 νdR≦40  where ndG denotes refractive index of the glass at d-line, νdG denotes Abbe number of the glass, ndR denotes refractive index of the ultraviolet-curable resin at d-line, and νdR denotes Abbe number of the resin.    
     
     
         10 . The diffractive optical element according to  claim 8 , wherein the material for molding is glass and the following conditional expressions are satisfied:  
       1.63≦ndG≦1.73 50νdG≦60 1.58≦ndR≦1.68 νdR≦35  where ndG denotes refractive index of the glass at d-line, νdG denotes Abbe number of the glass, ndR denotes refractive index of the ultraviolet-curable resin at d-line, and νdR denotes Abbe number of the resin.    
     
     
         11 . A diffractive optical element comprising: 
 a first diffractive element and a second diffractive element: and    the first and second diffractive elements being made of different materials with each other, closely laminated with each other to form grooves of a diffraction grating having a predetermined shape at the cemented surface of the first and the second diffractive elements;    wherein one of these diffractive elements is made of material for molding and the other diffractive element is made of ultraviolet-curable resin; and    wherein a pitch of the grooves of the diffraction grating is 70 μm or more.    
     
     
         12 . The diffractive optical element according to  claim 11 , wherein the material for molding is glass and the following conditional expressions are satisfied:  
       1.55≦ndG≦1.65 55νdG≦65 1.50≦ndR≦1.60 νdR≦40  where ndG denotes refractive index of the glass at d-line, νdG denotes Abbe number of the glass, ndR denotes refractive index of the ultraviolet-curable resin at d-line, and νdR denotes Abbe number of the resin.    
     
     
         13 . The diffractive optical element according to  claim 11 , wherein the material for molding is glass and the following conditional expressions are satisfied:  
       1.63≦ndG≦1.73 50νdG≦60 1.58≦ndR≦1.68 νdR≦35  where ndG denotes refractive index of the glass at d-line, νdG denotes Abbe number of the glass, ndR denotes refractive index of the ultraviolet-curable resin at d-line, and νdR denotes Abbe number of the resin.    
     
     
         14 . A diffractive optical element comprising: 
 a first transparent member on which grooves of a diffraction grating is formed;    a second transparent member having a plane or curved surface; and    an adhesive agent for cementing the grooves of the diffraction grating of the first transparent member with the plane or curved surface of the second transparent member.    
     
     
         15 . The diffractive optical element according to  claim 14 , wherein the first transparent member is made of material for molding.  
     
     
         16 . The diffractive optical element according to  claim 15 , wherein the adhesive agent is made of ultraviolet-curable resin.  
     
     
         17 . The diffractive optical element according to  claim 16 , wherein the following conditional expressions are satisfied:  
       1.55≦ndG≦1.70 50νdG≦65  
       1.50≦ndR≦1.65 νdR≦45  where ndG denotes refractive index at d-line of the first transparent member and νdG denotes Abbe number of the first transparent member, ndR denotes refractive index at d-line of the adhesive agent, and νdR denotes Abbe number the adhesive agent.    
     
     
         18 . The diffractive optical element according to  claim 17 , wherein the following conditional expression is satisfied:  
       h≦16.0 μm  where h denotes the groove height of the diffraction grating.    
     
     
         19 . The diffractive optical element according to  claim 18 , wherein a pitch of the grooves of the diffraction grating is 80 μm or more.  
     
     
         20 . The diffractive optical element according to  claim 16 , wherein the following conditional expression is satisfied:  
       h≦16.0 μm  where h denotes the groove height of the diffraction grating.    
     
     
         21 . The diffractive optical element according to  claim 20 , wherein a pitch of the grooves of the diffraction grating is 80 μm or more.  
     
     
         22 . The diffractive optical element according to  claim 15 , wherein the following conditional expressions are satisfied:  
       1.55≦ndG≦1.70 50νdG≦65 1.50≦ndR≦1.65  
       νdR≦45  where ndG denotes refractive index at d-line of the first transparent member and νdG denotes Abbe number of the first transparent member, ndR denotes refractive index at d-line of the adhesive agent, and νdR denotes Abbe number the adhesive agent.    
     
     
         23 . The diffractive optical element according to  claim 22 , wherein the following conditional expression is satisfied:  
       h≦16.0 μm  where h denotes the groove height of the diffraction grating.    
     
     
         24 . The diffractive optical element according to  claim 23 , wherein a pitch of the grooves of the diffraction grating is 80 μm or more.  
     
     
         25 . The diffractive optical element according to  claim 15 , wherein the following conditional expression is satisfied:  
       h≦16.0 μm  where h denotes the groove height of the diffraction grating.    
     
     
         26 . The diffractive optical element according to  claim 14 , wherein the adhesive agent is made of ultraviolet-curable resin.  
     
     
         27 . The diffractive optical element according to  claim 26 , wherein the following conditional expressions are satisfied:  
       1.55≦ndG≦1.70 50νdG≦65 1.50≦ndR≦1.65 νdR≦45  where ndG denotes refractive index at d-line of the first transparent member and νdG denotes Abbe number of the first transparent member, ndR denotes refractive index at d-line of the adhesive agent, and νdR denotes Abbe number the adhesive agent.    
     
     
         28 . The diffractive optical element according to  claim 27 , wherein the following conditional expression is satisfied:  
       h≦16.0 μm  where h denotes the groove height of the diffraction grating.    
     
     
         29 . The diffractive optical element according to  claim 28 , wherein a pitch of the grooves of the diffraction grating is 80 μm or more.  
     
     
         30 . The diffractive optical element according to  claim 27 , wherein a pitch of the grooves of the diffraction grating is 80 μm or more.  
     
     
         31 . The diffractive optical element according to  claim 26 , wherein the following conditional expression is satisfied:  
       h≦16.0 μm  where h denotes the groove height of the diffraction grating.    
     
     
         32 . The diffractive optical element according to  claim 14 , wherein the following conditional expressions are satisfied:  
       1.55≦ndG≦1.70 50νdG≦65 1.50≦ndR≦1.65 νdR≦45  where ndG denotes refractive index at d-line of the first transparent member and νdG denotes Abbe number of the first transparent member, ndR denotes refractive index at d-line of the adhesive agent, and νdR denotes Abbe number the adhesive agent.    
     
     
         33 . The diffractive optical element according to  claim 32 , wherein the following conditional expression is satisfied:  
       h≦16.0 μm  where h denotes the groove height of the diffraction grating.    
     
     
         34 . The diffractive optical element according to  claim 33 , wherein a pitch of the grooves of the diffraction grating is 80 μm or more.  
     
     
         35 . The diffractive optical element according to  claim 32 , wherein a pitch of the grooves of the diffraction grating is 80 μm or more.  
     
     
         36 . A method for manufacturing a diffractive optical element comprising steps of; 
 a first step that forms grooves of a diffraction grating on a surface of a first transparent member;    a second step that drips an adhesive agent onto the grooves of the diffraction grating on the surface of the first transparent member;    a third step that attaches a second transparent member having a plane or curved surface to the adhesive agent; and    a fourth step that cures the adhesive agent.    
     
     
         37 . The method for manufacturing a diffractive optical element according to  claim 36  wherein the first step is composed of; 
 a hardening step that the first transparent member is pressed, formed and hardened by using a mold on which the grooves of the diffraction grating are formed; and  
 a removing step that removes the hardened first transparent member from the mold.  
 
     
     
         38 . The method for manufacturing a diffractive optical element according to  claim 37  wherein the fourth step is composed of an irradiating step that irradiates the adhesive agent with an ultraviolet light.  
     
     
         39 . The method for manufacturing a diffractive optical element according to  claim 36  wherein the fourth step is composed of an irradiating step that irradiates the adhesive agent with an ultraviolet light.