Drop centering device

Abstract

A method for centering a drop of liquid on a given point on a surface. The inventive method consists in forming a bell-mouthed recess, whereby said recess has a curvature at any point at the limit of contact between the drop and the recess that is lower than or opposite to the curvature of a circle (TC) that is tangent to the surface of the recess to said point and at a symmetrical point (CP 2 ) of said surface.

1 . A method for centering a liquid drop ( 2 ) at a given location of a surface ( 4 ), characterized in that it consists of forming at this location a flared hollow ( 6 ) such that, at any point (CP 1 ) of the contact limit between the drop and the hollow, said hollow has a curvature smaller than or opposite to that of a circle (TC) tangent to the hollow surface at said point and at a symmetrical point (CP 2 ) of this surface.  
     
     
         2 . The method of  claim 1 , characterized in that the flared hollow ( 6 ) has the shape of a truncated cone with an axis perpendicular to said surface.  
     
     
         3 . The method of  claim 1 , characterized in that the flared hollow ( 6 ) has the shape of the upper central portion of a torus having an axis perpendicular to the surface.  
     
     
         4 . A method for centering a liquid drop ( 14 ) on the external surface of a convex surface ( 16 ), characterized in that it consists of giving this surface at any point (CP 1 ) of the contact limit with the drop a shape such that this surface has a curvature greater than that of a circle (TC) tangent to this surface at this point and at a symmetrical point (CP 2 ) of this surface.  
     
     
         5 . The method of  claim 4 , characterized in that it consists of forming the convex surface ( 6 ) by revolution against said axis of an arc of a circle having a radius smaller than that of said tangent circle.  
     
     
         6 . A variable-focus lens, including: 
 a wall made of an insulating material ( 4 ),    a drop of a first insulating liquid ( 2 ) arranged on an area of a first surface of the wall,    a second conductive liquid ( 8 ) covering the first  30  surface and the drop, the first and second liquids being non-miscible, having different optical indexes and substantially the same density, and    means ( 12 ) for applying an electric voltage (V) between the conductive liquid and an electrode ( 10 ) arranged on the second surface of said wall,    characterized in that the drop is placed in a flared hollow ( 6 ) of the wall according to the method of  claim 1 .    
     
     
         7 . The variable-focus lens of  claim 6 , characterized in that: 
 the electrode ( 10 ) is a sheet metal,    the flared hollow ( 6 ) is a truncated cone formed by embossing said sheet metal, centered on an axis ( 0 ) perpendicular to the first surface, and the bottom of which is pierced with a centered hole ( 11 ), and    the insulating material wall ( 4 ) is a transparent plastic film flattened against the electrode and the walls of the hollow, and which covers said hole.    
     
     
         8 . The variable-focus lens of  claim 6 , characterized in that: 
 the electrode ( 10 ) is a sheet metal,    the flared hollow ( 6 ) is a truncated cone formed by  20  machining said sheet metal, centered on an axis ( 0 ) perpendicular to the first surface, and the bottom of which is pierced with a centered hole ( 11 ), and    the isolating material wall ( 4 ) is a transparent plastic film flattened against the electrode and the walls of the hollow, and which covers said hole.    
     
     
         9 . A method for centering a liquid drop at a given location of a surface, comprising the steps of forming at this location a drop containment cavity surface such that, at any point (CP 1 ) of the contact limit between the drop and the drop containment cavity surface, said surface has a curvature smaller than or opposite to that of a circle (TC) tangent to the drop containment cavity surface at said point and at a symmetrical point (CP 2 ) of this surface.  
     
     
         10 . A method as claimed in  claim 9 , wherein the drop containment cavity surface is rotationally symmetric.  
     
     
         11 . A variable-focus lens, comprising: 
 a drop of a first insulating liquid arranged in a drop containment cavity having a sidewall with a first surface,    a second conductive liquid covering the first drop, the first and second liquids being non-miscible, having different optical indexes and substantially the same density, and    an electric voltage source selectively connectable between the conductive liquid and an electrode arranged on a second surface of said sidewall,    wherein the configuration of the sidewall is such that, at any point (CP 1 ) of a contact limit between the drop and the drop containment cavity first surface, said surface has a curvature smaller than or opposite to that of a circle (TC) tangent to the drop containment cavity first surface at said point and at a symmetrical point (CP 2 ) of this surface.