Abstract:
Adjustable pinhole, particularly for the illumination beam path and/or detection beam path of a laser scanning microscope, wherein the pinhole is defined by foil edges which are adjustable relative to one another, and at least two foils, each with at least one straight edge, are advantageously arranged relative to one another and/or connected to one another in such a way that their edges describe an L-shape and the L-shaped connection pieces are arranged on one another in such a way that they define a rhombic or square light passage and they are moved relative to one another for adjusting the pinhole.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    This application claims priority of German Application No. 102 44 850;7, filed Sep. 24, 2002, the complete disclosure of which is hereby incorporated by reference.  
         BACKGROUND OF THE INVENTION  
         [0002]    a) Field of the Invention  
           [0003]    The invention relates to an installable pinhole which may be used in optical instruments such as a laser scanning microscope or the like.  
           [0004]    b) Description of the Related Art  
           [0005]    A scissor-like closure mechanism for a pinhole is described in DE 20205079 U1. Above all, in this connection, the manufacturing accuracy of the angle points which are located opposite one another and which are to be moved relative to one another over the axis of rotation pose a serious obstacle to a reproducible, light-tight closure and exact square shape of the pinhole aperture.  
         OBJECT AND SUMMARY OF THE INVENTION  
         [0006]    It is the primary object of the invention to develop a highly accurate pinhole which can be closed in a light-tight manner and whose aperture has a square shape at values above zero.  
           [0007]    According to the invention, this object is met in that an arrangement of foil edges, whose edges facing toward the pinhole aperture are preferably ground, are moved relative to one another according to the inventive constructions. The decisive advantage in forming the pinhole aperture from foil edges consists in that the comers of the pinhole aperture are entirely sharp-edged and the radius of curvature of the comers is zero. This allows pinhole apertures to be adjusted in a reproducible manner upward from zero.  
           [0008]    The foil edges can be manufactured in a highly precise manner beforehand, for example, by cutting with diamond cutting edges or by laser cutting or etching.  
           [0009]    For the purpose of the preferable movement which should be carried out in a very exact manner so as to be free from play, solid joints are provided in the form of flexible webs at which tilting or rotation occurs.  
           [0010]    Surprisingly, the invention permits an adjustable and reproducible reduction in the size of the pinhole aperture from a zero value and light-tight closure thereof without the risk of the foil edges colliding with one another.  
           [0011]    The invention will be described more fully in the following with reference to the schematic drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    In the drawings:  
         [0013]    [0013]FIG. 1 a  is a schematic description of foil pieces in accordance with the invention;  
         [0014]    [0014]FIG. 1 b  shows, in schematic form, another variant of the invention;  
         [0015]    [0015]FIG. 1 c  shows again, in schematic form, another variant of the invention;  
         [0016]    [0016]FIGS. 2 a ,  2   b  and  2   c  show, in schematic form, three different variants of a second construction in accordance with the invention;  
         [0017]    [0017]FIG. 3 shows an arrangement of the pinhole adjustment with reference to the arrangement according to FIG. 1 a;    
         [0018]    [0018]FIG. 4 shows a broken out section of the arrangement in FIG. 3 in cross-sectional schematic form;  
         [0019]    [0019]FIG. 5 shows a spindle drive in schematic form for moving a plate in the x-direction;  
         [0020]    [0020]FIG. 6 illustrates another aspect of the invention in schematic form;  
         [0021]    [0021]FIGS. 7 a  and  7   b  show two views, in schematic fashion, of sliding glass plates in another form of the invention for forming the pinhole; and  
         [0022]    [0022]FIGS. 8 a ,  8   b  and  8   c  illustrate another construction of the invention in schematic form. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0023]    By foil pieces or foil edges is meant hereinafter essentially the edges located opposite one another when opening and/or closing the pinhole aperture, while the rest of the shape of the foil pieces may vary depending on space requirement and construction.  
         [0024]    The foil material can be, e.g., spring steel, spring bronze or aluminum having a thickness of 10 μm, for example. The foil edges can be ground in a composite of, e.g., one hundred individual pre-manufactured foils and punched and then severed or used in the as-delivered state as strip material.  
         [0025]    [0025]FIG. 1 a  schematically shows an illustration of foil pieces F 1 -F 4  which are arranged preferably at right angles in an L-shaped manner; F 1 ; F 2  and F 3 ; F 4  are fixedly connected with one another at connection points V 1 , V 2 . They are fastened in a stationary manner by their ends remote of the connection points (indicated in black by s) to base plates P 1  and P 2  which are displaceable relative to one another in the direction indicated by the arrows; specifically, they are fastened on each plate in such a way that the pinhole aperture opens and closes in a punctiform manner in the direction indicated by the arrows during the synchronous movement of the plates P 1  and P 2 . The foils can be connected with one another and with the plates P 1  and P 2 , for example, by gluing, resistance welding, diffusion welding or ultrasonic welding.  
         [0026]    As a result of the synchronous displacement of the plates P 1  and P 2  in the direction indicated by the arrows, the aperture area between the foil edges connected at points V 1 , V 2  is reduced or enlarged; specifically, pinhole PH is opened when plates P 1 , P 2  approach one another, and vice versa. The pinhole aperture preferably closes in a square manner until becoming a point. When the distance between the plates P 1 , P 2  is further increased, the pinhole aperture is covered in a light-tight manner without the foil edges obstructing or damaging one another.  
         [0027]    Due to the fact that each two foil edges are fastened at right angles one above the other, it is ensured that the right angle formed by them is not subject to any manufacturing problems. The foil edges are prevented from locking up or catching in that F 3  is fastened to F 4  in a shortened manner and therefore does not contact the foil edge of F 2 .  
         [0028]    [0028]FIG. 1 b  shows another variant of the invention. It is formed of cross-shaped foil edges F 5 -F 8  which are arranged in a cross-shaped manner and which are fastened to plates P 1  (F 5 , F 6 ) and P 2  (F 7 , F 8 ), respectively. Two plates P 1 , P 2  are displaceable relative to one another in the direction indicated by the arrows. However, in this case when PI, P 2  approach one another the pinhole PH closes, and vice versa, because F 5 -F 8  and F 6 -F 7  slide over one another in a scissor-like manner, since they are not connected to one another. The aperture of the pinhole is formed in this case by the respective comers of the foil arrangements remote of the plate edges.  
         [0029]    [0029]FIG. 1 c  shows another variant of the invention. Each of the foil edges F 9 , F 10 , F 11 , F 12  has two joints, preferably solid-state joints. The distance between the articulation points G 91  to G 92 , G 101  to G 102 , G 111  to G 112 , and G 121  to G 122  is preferably identical and much larger than the pinhole aperture. Each pair of foils F 9 , F 11  and F 10 , F 12  is connected in an L-shaped manner at their connection points V 3  and V 4  and is fastened in a cross-shaped manner to plates P 1 , P 2  in such a way that the pinhole aperture closes in a punctiform and preferably square-shaped manner, and vice versa, when plates P 1  and P 2  open synchronously in the direction indicated by the arrows. This is carried out in that when the distance between plates P 1 , P 2  is increased synchronously in the direction indicated by the arrows the articulation points G 92  and G 102 , G 112  and G 121  move toward one another perpendicular to the direction indicated by the arrows and close the pinhole aperture, and vice versa. In so doing, the flexible articulation notches at the foils open and close. The shape of the pinhole aperture remains approximately square when opening and closing the pinhole. When the distance between plates P 1 , P 2  increases, the pinhole aperture is finally covered in a light-tight manner without the foil edges obstructing or destroying one another.  
         [0030]    The foil edges are prevented from catching in that F 9  is fastened to F 11  in a shortened manner and therefore does not come into contact with foil edge F 12 .  
         [0031]    [0031]FIG. 2 shows a new construction, wherein every two foil edges F 13 , F 14 , F 15 , F 16  are arranged in a slightly V-shaped manner relative to one another by pairs, i.e., they enclose a small angle relative to one another. In FIG. 2 a , one pair of foils is synchronously displaced relative to the other with respect to its center axis between the individual foils, preferably perpendicular to one another in the direction indicated by the arrows. A perpendicular relative displacement, preferably by synchronous movement of both pairs of foils by means of two motors (not shown) results in large adjusting paths when adjusting the pinhole aperture with high accuracy, so that path measuring systems can be dispensed with, as the case may be.  
         [0032]    In FIG. 2 b , the slightly V-shaped aperture angle between the foil edges is varied in that the foils F 17  and F 18  are rotated around axes A 1  and A 2  and foils F 19  and F 20  are rotated around axes A 3  and A 4  in opposite directions and preferably synchronous with the opening and closing of the pinhole aperture.  
         [0033]    In FIG. 2 c , the axes of rotation A 5 , A 6  and A 7 , A 8  are on the opposite sides of the pairs of foils F 21 , F 22  and F 23 , F 24 . The rotation of the foils is preferably carried out synchronously and in the same direction.  
         [0034]    [0034]FIG. 3 shows an arrangement for pinhole adjustment with reference to the arrangement of the foil edges according to FIG. 1 a . However, the displacement of the plates P 1 , P 2  can be carried out in an analogous manner when using the foil edge arrangement according to FIGS. 1 b, c.  The stepping motor SM shown here is fixed with respect to rotation only at the plate P 1  and drives spindles SP 1  and SP 2  which have threads with different pitches and which, by means of nuts M 1  and M 2 , cause the guide part F 1  connected to P 1  and P 2  to move perpendicular to the displacing movement of P 1 , P 2 . Parts F and P are preferably formed of one piece and are connected together by springing webs (parallel spring joints). The parts can be manufactured, for example, by laser cutting, etching, erosion or punching.  
         [0035]    The stepping motor SM is arranged so as to be fixed with respect to rotation and freely displaceable relative to plate P 1 . It synchronously drives the spindles SP 1  and SP 2  having threads with different pitch (e.g., threads M3x0.5 and M2,6x0.45 result in a pitch difference of 50 μm).  
         [0036]    Spindle SP 2  is driven by stepping motor SM so as to screw into the nut M 2  fastened to the frame F 2 , whereupon the stepping motor SM which is fixed with respect to rotation is displaced along axis A by the spindle displacement in the direction indicated by the arrows.  
         [0037]    Nut M 1  which is fastened to the guide part F 1  is displaced relative to nut M 2  due to the differential thread by an amount approximately 10 times less than that of the stepping motor SM. This causes a very high sensitivity in the adjustment of F 1 .  
         [0038]    The diagonal spring webs ST 5 , ST 6  which spread apart or close when the motor shaft rotates are fastened to guide part F 1  which is connected by spring webs (parallel spring joint) to the frame and open and close the plates P 1 , P 2  and, therefore, the pinhole.  
         [0039]    While the frame F 2  is connected to plates P 1 , P 2  for parallel guidance thereof by a plurality of webs ST 1 -ST 4  (two parallel spring joints), plates P 1 , P 2  are connected respectively to F 1  by webs ST 5 , ST 6  which are supported in a springing manner and which are arranged diagonal to the displacement direction of P 1  and P 2  and diagonal to F 1 , F 2 . In this way, a displacement of F 1  in the direction indicated by the arrows is transformed into a displacement of plates P 1  and P 2 , and the resulting adjustment of the pinhole aperture is carried out according to FIG. 1 or  2 .  
         [0040]    [0040]FIG. 3 schematically shows a broken out portion AS which can accommodate a path measuring system as shown by way of example in FIG. 4. It measures the relative movement of the plates P 1 , P 2  and, therefore, the size of the diagonals of the pinhole aperture.  
         [0041]    A light source LED is fixedly arranged on plate P 2 . A spatially resolving sensor S which is located across from it on P 2  and which detects the movement of a measurement scale MR, in this case a transparent grid ruler, based on the detected grid change is assigned to the light source LED. Measuring systems of this kind are commercially available with an accuracy from 0.1 μm. Commercial measuring systems of this kind make it possible, in addition, to reference the stepping motor drive.  
         [0042]    Based on the detected relative movement of the plates P 1 , P 2 , the actual pinhole aperture can be detected online and can also be correlated with an optical measurement in different pinhole aperture states. A referencing of the stepping motor drive can also be carried out in a simple manner in that an additional optical detector, not shown, detects the light of a light source, not shown, passing through the pinhole aperture when opening the pinhole aperture and, at that time, resolves the referencing of the stepping motor drive in a highly accurate manner.  
         [0043]    [0043]FIG. 5 shows a spindle drive comprising a stepping motor SM 1  and nuts M 3 , M 4  which ensures a movement of a plate PLX in x-direction. This plate is connected by fastening points BF 1 , for example, with fastening points BF on the displacement device according to FIG. 4, so that the entire pinhole arrangement according to FIG. 4 is displaceable in x-direction and—with another arrangement that can be connected to the arrangement according to FIG. 5—also in y-direction. This ensures an x-displacement and y-displacement of the pinhole vertical to the optical axis, for example, for centering purposes.  
         [0044]    [0044]FIG. 7 shows two thin glass plates GL 1 , GL 2  which are displaceable relative to one another, for example, object carriers of a microscope which are displaceable relative to one another in the direction indicated by the arrows and are partially coated, for example, by means of a high-precision lithography process. This coating is carried out in a mirror-symmetric manner for GL 1  and GL 2  in such a way that a preferably right-angled, sharp-edged angle W 1 , W 2  of the coating remains open and forms the pinhole PH when plates GL 1 , GL 2  are located above one another. In order that the plates do not slide directly on one another, which can damage the coating, thin Teflon strips TS can be provided on at least one plate at the edges outside the active area of the pinhole PH; the thin Teflon strips ensure frictionless sliding and are preferably oriented in the direction of displacement. Teflon slides with an almost ideal absence of friction only on a smooth glass surface. Therefore, there should not be any chrome coating on the glass plates in the area of the Teflon coating. An immersion liquid may be applied between the glass plates to prevent reflection losses at the surfaces of the glass plates GL 1  and GL 2  facing each other.  
         [0045]    [0045]FIG. 8 shows another construction of an adjustable pinhole comprising foils FL 1 -FL 4  arranged at lever joints H 1 -H 4 . The arrangement is based on an arrangement of the foil edges according to FIG. 2 c.    
         [0046]    The lever joints H 1 -H 4  which are preferably of identical length are connected to one another in an articulated manner and form an adjustable rhombus. The adjustment is carried out at points A 1 , A 2  by means of guiding together or spreading apart lever arms HA 1 , HA 2  which are connected to A 1  and A 2  and which are supported at fulcrums A 3 , A 4 .  
         [0047]    When HA 1  and HA 2 , for example, are moved relative to one another (direction indicated by the arrows in FIG. 8 b ), the following rotational movements are brought about: FL 1  in counterclockwise direction; FL 2  in clockwise direction; FL 3  in counterclockwise direction; FL 4  in clockwise direction, so that two foils FL respectively move relative to one another and the pinhole is accordingly closed. When HA 1  and HA 2  are spread apart, this has the opposite result.  
         [0048]    [0048]FIG. 8 c  shows a complete arrangement in which a pinhole adjustment can be carried out by an arrangement analogous to that shown in FIG. 3 by means of an individual stepping motor SM.  
         [0049]    While the foregoing description and drawings represent the present invention, it will be obvious to those skilled in the art that various changes may be made therein without departing from the true spirit and scope of the present invention.