Method for fabricating a prism and method for fabricating an optical system

Abstract

A method for fabricating a prism that comprises a first and a second substrate, both translucent, bonded together with an optical thin film interposed at the interface in between and that is used with the interface inclined relative to the optical axis of incident laser light of a wavelength of 420 nm or shorter includes the step of bonding together the first and second substrates of which the difference ΔN1 in refractive index at the wavelength of the laser light fulfills the condition: ΔN1≦|1/(0.3×10 4 ×NA×t)|, where t represents the thickness of the first and second substrates cemented together as measured along the optical axis of the laser light, and NA represents the numerical aperture of the incident laser light.

1. A method for fabricating a prism that comprises a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and that is used with the interface inclined relative to an optical axis of incident laser light of a wavelength of 420 nm or shorter, comprising the step of:
 bonding together the first and second substrates of which a difference ΔN1 in refractive index at the wavelength of the laser light fulfills the following condition: 
   ΔN1≦|1/(0.3×10 4 ×NA×t)| 
 
 
       where
 t represents a thickness of the first and second substrates cemented together as measured along the optical axis of the laser light; and  
 NA represents a numerical aperture of the incident laser light.  
 
     
     
       2. A method for fabricating a prism as claimed in  claim 1 , the prism further comprising a third substrate that is bonded to the second substrate with an optical thin film interposed at an interface in between, the method further comprising the step of:
 bonding together the second and third substrates of which a difference ΔN2 in refractive index at the wavelength of the laser light fulfills the following condition: 
   ΔN2≦|1/(0.3×10 4 ×NA×t)|.  
 
 
     
     
       3. A method for fabricating a prism as claimed in  claim 1 ,
 wherein the optical thin film is one of a polarizing beam splitter film, a beam splitter film, a dichroic film, an anti-reflection film, and a total-reflection film.  
 
     
     
       4. A method for fabricating a prism that comprises a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and that is used with the interface inclined relative to an optical axis of incident laser light of a wavelength of 420 nm or shorter, comprising the step of:
 bonding together the first and second substrates of which a difference in refractive index at the wavelength of the laser light is 1/300 or smaller.  
 
     
     
       5. A method for fabricating a prism as claimed in  claim 4 , the prism further comprising a third substrate that is bonded to the second substrate with an optical thin film interposed at an interface in between, the method further comprising the step of:
 bonding together the second and third substrates of which a difference in refractive index at the wavelength of the laser light is 1/300 or smaller.  
 
     
     
       6. A method for fabricating a prism as claimed in  claim 4 ,
 wherein the optical thin film is one of a polarizing beam splitter film, a beam splitter film, a dichroic film, an anti-reflection film, and a total-reflection film.  
 
     
     
       7. A method for fabricating a prism that comprises a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and that is used with the interface inclined relative to an optical axis of incident laser light of a wavelength of 420 nm or shorter, comprising the step of:
 bonding together the first and second substrates of which a difference in refractive index at the wavelength of the laser light is 1/1500 or smaller.  
 
     
     
       8. A method for fabricating a prism as claimed in  claim 7 , the prism further comprising a third substrate that is bonded to the second substrate with an optical thin film interposed at an interface in between, the method further comprising the step of:
 bonding together the second and third substrates of which a difference in refractive index at the wavelength of the laser light is 1/1500 or smaller.  
 
     
     
       9. A method for fabricating a prism as claimed in  claim 7 ,
 wherein the optical thin film is one of a polarizing beam splitter film, a beam splitter film, a dichroic film, an anti-reflection film, and a total-reflection film.  
 
     
     
       10. A method for fabricating an optical system comprising a light source that emits laser light of a wavelength of 420 nm or shorter and a prism that comprises a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and that is used with the interface inclined relative to an optical axis of incident laser light of a wavelength of 420 nm or shorter, comprising the step of:
 bonding together the first and second substrates of which a difference ΔN1 in refractive index at the wavelength of the laser light fulfills the following condition: 
   ΔN1≦|1/(0.3×10 4 ×NA×t)| 
 
 
       where
 t represents a thickness of the first and second substrates cemented together as measured along the optical axis of the laser light; and  
 NA represents a numerical aperture of the incident laser light.  
 
     
     
       11. A method for fabricating an optical system as claimed in  claim 10 , the prism further comprising a third substrate that is bonded to the second substrate with an optical thin film interposed at an interface in between, the method further comprising the step of:
 bonding together the second and third substrates of which a difference ΔN2 in refractive index at the wavelength of the laser light fulfills the following condition: 
   ΔN2≦|1/(0.3×10 4 ×NA×t)|.  
 
 
     
     
       12. A method for fabricating an optical system as claimed in  claim 10 ,
 wherein the optical thin film is one of a polarizing beam splitter film, a beam splitter film, a dichroic film, an anti-reflection film, and a total-reflection film.  
 
     
     
       13. A method for fabricating an optical system comprising a light source that emits laser light of a wavelength of 420 nm or shorter and a prism that comprises a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and that is used with the interface inclined relative to an optical axis of incident laser light of a wavelength of 420 nm or shorter, comprising the step of:
 bonding together the first and second substrates of which a difference in refractive index at the wavelength of the laser light is 1/300 or smaller.  
 
     
     
       14. A method for fabricating an optical system as claimed in  claim 13 , the prism further comprising a third substrate that is bonded to the second substrate with an optical thin film interposed at an interface in between, the method further comprising the step of:
 bonding together the second and third substrates of which a difference in refractive index at the wavelength of the laser light is 1/300 or smaller.  
 
     
     
       15. A method for fabricating an optical system as claimed in  claim 13 ,
 wherein the optical thin film is one of a polarizing beam splitter film, a beam splitter film, a dichroic film, an anti-reflection film, and a total-reflection film.  
 
     
     
       16. A method for fabricating an optical system comprising a light source that emits laser light of a wavelength of 420 nm or shorter and a prism that comprises a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and that is used with the interface inclined relative to an optical axis of incident laser light of a wavelength of 420 nm or shorter, comprising the step of:
 bonding together the first and second substrates of which a difference in refractive index at the wavelength of the laser light is 1/1500 or smaller.  
 
     
     
       17. A method for fabricating an optical system as claimed in  claim 16 , the prism further comprising a third substrate that is bonded to the second substrate with an optical thin film interposed at an interface in between, the method further comprising the step of:
 bonding together the second and third substrates of which a difference in refractive index at the wavelength of the laser light is 1/1500 or smaller.  
 
     
     
       18. A method for fabricating an optical system as claimed in  claim 16 ,
 wherein the optical thin film is one of a polarizing beam splitter film, a beam splitter film, a dichroic film, an anti-reflection film, and a total-reflection film.  
 
     
     
       19. A method for fabricating a prism for use in an optical pickup, the prism comprising a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and being used with the interface inclined relative to an optical axis of incident laser light of a wavelength of  420  nm or shorter, the method comprising the steps of:
   combining together the first and second substrates, which have been sorted according to refractive indices thereof, such that a difference ΔN 1  between refractive indices of the first and second substrates fulfills the formula below; and        cementing together the first and second substrates thus combined together,        the formula being        ΔN 1 ≦| 1 / (   0 . 3 × 10     4   ×NA×t )|     
       
         where:  
         
           t represents a thickness of the first and second substrates cemented together as measured along the optical axis of the laser light; and  
         
         
           NA represents a numerical aperture of the incident laser light. 
         
       
     
     
       20. A method for fabricating a prism as claimed in  claim 19 , further comprising the step of sorting the first substrate and the second substrate according to refractive indices thereof. 
     
     
       21. A method for fabricating a prism for use in an optical pickup, the prism comprising a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and being used with the interface inclined relative to an optical axis of incident laser light of a wavelength of  420  nm or shorter, the method comprising the step of:
   combining together the first and second substrates, which have been sorted according to refractive indices thereof, such that a difference between refractive indices of the first and second substrates equals  1 / 3 , 000  or smaller; and        cementing together the first and second substrates thus combined together.     
     
     
       22. A method for fabricating a prism as claimed in  claim 21 , wherein the difference in refractive index between the first and second substrates at the wavelength of the laser light is  1 / 10 , 000  or smaller. 
     
     
       23. A method for fabricating a prism as claimed in  claim 21 , further comprising the step of sorting the first substrate and the second substrate according to refractive indices thereof. 
     
     
       24. A method for fabricating a prism as claimed in  claim 22 , further comprising the step of sorting the first substrate and the second substrate according to refractive indices thereof. 
     
     
       25. A method for fabricating a prism as claimed in  claim 19 , wherein difference ΔN 1  between refractive indices of the first and second substrates at the wavelength of the laser light is  1 / 10 , 000  or smaller. 
     
     
       26. A method for fabricating a prism for use in an optical pickup, the prism comprising a first and a second substrate, both translucent, bonded together with an optical thin film interposed at an interface in between and being used with the interface inclined relative to an optical axis of incident laser light of a wavelength of  420  nm or shorter, the method comprising the step of:
   combining together the first and second substrates, which have been sorted according to refractive indices thereof, such that a difference between refractive indices of the first and second substrates is  1 / 3 , 000  or smaller; and        bonding together the first and second substrates thus combined together.     
     
     
       27. A method for fabricating a prism as claimed in  claim 26 , wherein the difference in refractive index between the first and second substrates at the wavelength of the laser light is  1 / 10 , 000  or smaller. 
     
     
       28. A method for fabricating a prism as claimed in  claim 26 , further comprising the step of sorting the first and second substrates according to refractive indices thereof. 
     
     
       29. A method for fabricating a prism as claimed in  claim 27 , further comprising the step of sorting the first and second substrates according to refractive indices thereof. 
     
     
       30. A method for fabricating a prism as claimed in  claim 26 , the prism further comprising a third substrate bonded to the second substrate with an optical thin film interposed at an interface in between, the method further comprising the step of:
   combining together the second and third substrates, which have been sorted according to refractive indices thereof, such that a difference between refractive indices of the second and third substrate is  1 / 3 , 000  or smaller; and        bonding together the second and third substrates thus combined together.     
     
     
       31. A method for fabricating a prism as claimed in  claim 30 , further comprising the step of sorting the first, second and third substrates according to refractive indices thereof. 
     
     
       32. A method for fabricating a prism as claimed in  claim 30 , wherein the difference in refractive index between the second and third substrates at the wavelength of the laser light is  1 / 10 , 000  or smaller.