Vibration-resistant interferometer apparatus

Abstract

A half mirror 4 divides a luminous flux emitted from a low-coherence light source 1 into two luminous fluxes, a secondary reference plate 6 is held integrally with a reference plate 16 , and a secondary sample 8 is held integrally with a sample 17 . A first luminous flux which is obtained through dividing by the half mirror 4 is reflected at a mirror 5 and which reaches a secondary reference surface 6 a , is reflected at the secondary reference surface 6 a , returns along the same optical path, and is transmitted through the half mirror 4 . The second luminous flux reaches a secondary sample surface 8 a , is reflected at the secondary sample surface 8 a , returns along the same optical path, and is combined with the first luminous flux at the half mirror 4 . The optical path length difference between the first luminous flux and the second luminous flux coincides with approximately twice the optical distance between a reference surface 16 a and a sample surface 17 a.

1 . A vibration-resistant interferometer apparatus that is a light wave interferometer apparatus in which a luminous flux emitted from a light source is divided into two luminous fluxes by luminous flux dividing means, one of said two luminous fluxes is detoured by a prescribed optical path length relative to the other one, and then said two luminous fluxes are recombined into one luminous flux to form an irradiating luminous flux, and interference fringes produced through optical interference between a luminous flux obtained through said irradiating luminous flux being reflected at a reference surface and a luminous flux obtained through said irradiating luminous flux being transmitted through said reference surface and then reflected at a sample surface are obtained; 
 wherein said light source is a low-coherence light source for which said luminous flux emitted from said light source has a coherence length shorter than twice the optical distance between said reference surface and said sample surface, or a wavelength-modulated light source adjusted such that the coherence length is equivalent to the coherence length possessed by such a low-coherence light source when an image of said interference fringes is captured by an imaging element;    wherein said irradiating luminous flux is obtained by reflecting a first luminous flux out of said two luminous fluxes via said reference surface or a secondary reference surface that is held such that the relative positional relationship thereof with said reference surface does not change, and reflecting a second luminous flux out of said two luminous fluxes via said sample surface or a secondary sample surface that is held such that the relative positional relationship thereof with said sample surface does not change and faces in the same direction as said sample surface, and then recombining said first luminous flux and said second luminous flux into said one luminous flux such that the axis of said first luminous flux and the axis of said second luminous flux substantially coincide with one another; and    wherein said prescribed optical path length coincides with approximately twice the optical distance between said reference surface and said sample surface, in which said approximately twice is within the range of said coherence length of said luminous flux emitted from said light source.    
   
   
       2 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said luminous flux dividing means is said reference surface or said secondary reference surface, a luminous flux reflected at said reference surface or said secondary reference surface is taken as said first luminous flux, a luminous flux transmitted through said reference surface or said secondary reference surface, reflected at said sample surface or said secondary sample surface, and then transmitted through said reference surface or said secondary reference surface is taken as said second luminous flux, and said first luminous flux and said second luminous flux are recombined into said one luminous flux at said reference surface or said secondary reference surface to form said irradiating luminous flux.  
   
   
       3 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said luminous flux dividing means is a beam splitter, one of said two luminous fluxes obtained through the dividing by said beam splitter is irradiated onto said reference surface or said secondary reference surface and the reflected luminous flux is taken as said first luminous flux, the other one of said two luminous fluxes is irradiated onto said sample surface or said secondary sample surface and the reflected luminous flux is taken as said second luminous flux, and said first luminous flux and said second luminous flux are recombined into said one luminous flux at said beam splitter to form said irradiating luminous flux.  
   
   
       4 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein a reflecting surface that reflects said luminous flux emitted from said light source is disposed on a side of said reference surface from which said irradiating luminous flux is incident, said luminous flux is irradiated substantially perpendicularly onto said reference surface and said sample surface via said reflecting surface, and said first luminous flux which has been reflected at said reference surface and said second luminous flux which has been transmitted through said reference surface and then reflected at said sample surface are combined at the position of said reference surface to form said irradiating luminous flux.  
   
   
       5 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said secondary reference surface is disposed substantially in the same plane as said reference surface, and/or said secondary sample surface is disposed substantially in the same plane as said sample surface.  
   
   
       6 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said secondary reference surface and/or said secondary sample surface has optical path length adjustment means for moving said secondary reference surface and/or said secondary sample surface in a direction along the axis of the incident luminous flux, and optical axis adjustment means for adjusting the inclination of the axis of the reflected luminous flux relative to the axis of the incident luminous flux.  
   
   
       7 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said secondary reference surface or said secondary sample surface can be moved by a piezoelectric element.  
   
   
       8 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said prescribed optical path length substantially equals twice said optical distance between said reference surface and said sample surface.  
   
   
       9 . The vibration-resistant interferometer apparatus according to  claim 1 , further having light amount changing means for at least one of said two luminous fluxes.  
   
   
       10 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said luminous flux emitted from said light source is linearly polarized light having a prescribed oscillation plane, or is made to be linearly polarized light having a prescribed oscillation plane by being transmitted through a prescribed polarizing element.  
   
   
       11 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein a sample having said sample surface is a transparent thin sheet, and said coherence length of said luminous flux emitted from said light source is set to be shorter than twice the optical distance of the thickness of said transparent thin sheet.  
   
   
       12 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said sample surface is a reference reflecting mirror surface, a light-transmitting sample transmitting object is disposed between said reference surface and said reference reflecting mirror surface, said irradiating luminous flux and a luminous flux obtained through reflection of said irradiating luminous flux by said reference reflecting mirror surface are transmitted through said sample transmitting object, and phase distribution measurement is carried out on said sample transmitting object.  
   
   
       13 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein a condensing lens is disposed in said second luminous flux, and the condensing point of said second luminous flux by said condensing lens is positioned on said sample surface.  
   
   
       14 . The vibration-resistant interferometer apparatus according to  claim 1 , wherein said low-coherence light source is a light emitting diode, a super luminescent diode, or a halogen lamp.  
   
   
       15 . The vibration-resistant interferometer apparatus according to  claim 5 , wherein a hole is formed in a central portion of said sample surface, and said secondary sample surface is disposed inside said hole.  
   
   
       16 . The vibration-resistant interferometer apparatus according to  claim 11 , wherein said transparent thin sheet is a film.