Abstract:
The invention concerns a modifiable assembly of microscopic apertures comprising several plates ( 100, 110 ) coated with an opaque deposition except on transparent parts, for example ( 101, 114, 115 ), capable of sliding relative to one another, separated by an oil layer ( 117 ). The invention is applicable to microscopic apertures for single-point or multiple-point confocal microscopy.

Description:
TECHNICAL FIELD  
       [0001]     The invention concerns a microscopic hole or a set of microscopic holes (pinholes), the number of these holes and/or their size being able to be modified easily. Such a set of pinholes is intended to be used for various applications in optics, in particular in confocal microscopy.  
       STATE OF THE ART  
       [0002]     In confocal microscopy use is usually made of two types of pinhole: 
        holes of fixed size: to modify the size of a hole, it is necessary to replace it with another. Typically several pinholes can be mounted on a wheel having a position corresponding to the use of each of these holes. The movement of the wheel must be very precise.     holes of variable size: functioning on the principle of the iris diaphragm, they require at least three blades which form a hole by crossing one another and are expensive because of the relative complexity of the mechanism.        
 
         [0005]     Conventionally, confocal microscopy systems require the use of a single pinhole. For example, the first embodiment of French patent application number 0103860 of Mar. 22, 2001, as well as the microscope described in FIG. 3 of the U.S. Pat. No. 5,978,095 or the microscope described in the patent application U.S. Pat. No. 5,162,941.  
         [0006]     Other confocal microscopy systems require the use of an array of pinholes. For example, the microscopes described by FIG. 1 of U.S. Pat. No. 5,239,178 or FIG. 3 in the patent U.S. Pat. No. 5,978,095, or the Nipkow disk systems.  
         [0007]     In certain embodiments of a microscope such as the one described in French patent number 0103860 of Mar. 22, 2001, an array of pinholes must be positioned with great precision, which is difficult using a simple technique consisting of exchanging the whole of the array. When “single” pinholes are simply exchanged, as on certain single-point confocal microscopes, their precise positioning is also difficult. In addition, the systems for exchanging arrays of pinholes are necessarily bulky, since their size is the sum of the sizes of each array able to be exchanged.  
         [0008]     In the case of microscopes using an array of pinholes, the size and density of the holes cannot usually be modified. However, this modification is desirable in order to adapt the size of the holes to the wavelength being studied. U.S. Pat. No. 6,002,509 affords a solution to this problem in the case of a Nipkow disk microscope. However, this solution requires the replacement of the array of holes with an array of reflective points. When the technique used consists of using reflective points produced by a multilayer treatment, each wavelength corresponds to a given size and density of the reflective points. It is then not possible to modify the size or density of the holes of the hole with a given wavelength, and the number of different sizes of holes is limited by the performance of the multilayer treatment. When the technique used consists of introducing several concentric rings on the Nipkow disk, a movement of the disk, which is not very practical, is necessary, and the size of the disk rapidly becomes excessive. The technique is difficult to adapt to systems using a fixed array of pinholes.  
       DESCRIPTION OF THE INVENTION  
       [0009]     The object of the invention is a set of one or more pinholes of variable size and/or number, the changes to which are obtained by a simplified method which is precise and inexpensive. In particular, one object of the invention is to produce pinholes which can be modified without problems in positioning and which are of reduced bulk. “Holes” means holes in the optical sense of the term, that is to say small areas through which light can pass, not necessarily void. A “hole” can for example be an interruption in an opaque layer deposited on glass.  
         [0010]     To this end, the object of the invention is a modifiable set of at least one pinhole intended for filtering a light beam, comprising several plates each carrying at least one pinhole, one of these plates carrying at least two pinholes, said several plates being placed against each other and being able to slide with respect to each other,  
         [0011]     in order to form the modifiable set of at least one pinhole by the superimposition of pinholes in said several plates,  
         [0012]     and to modify, by sliding said plates with respect to each other, the number and/or size of the pinholes in said modifiable set of at least one pinhole.  
         [0013]     An iris diaphragm also comprises plates sliding with respect to each other. The invention is distinguished in this by the fact that these plates carry pinholes and by the fact that one of the plates carries at least two pinholes. This particular arrangement simplifies the design of the system (in the case of a single pinhole, it is possible to use only two plates) and makes it possible to produce arrays of modifiable pinholes, whilst iris diaphragms are designed only for a single modifiable pinhole.  
         [0014]     A modifiable set of pinholes can also be obtained by a system physically exchanging two sets of pinholes produced on different plates. This solution is used in certain single-point confocal microscopes. The present invention is distinguished from this simple technical solution by the use of several superimposed plates, which makes it possible to modify the array of pinholes by means of movements which are also microscopic, rather than macroscopic as is the case in the state of the art. This simplifies the positioning problems.  
         [0015]     Various techniques for producing plates can be employed. For example, and according to one characteristic of the invention, two of said plates can be transparent windows on which said pinholes are produced by the deposition of an opaque layer by a lithographic method. The opaque layers on these two plates can then be turned towards each other, so that the space separating them is as small as possible. The advantage of this technique is that the windows have good rigidity (deform little).  
         [0016]     According to one characteristic of the invention, at least one of the plates is a fine opaque sheet in which said pinholes are obtained by piercing. This solution is necessary when more than two plates are used. This is because, if only glass plates are used, their thickness does not make it possible to produce an array of holes correctly.  
         [0017]     According to one characteristic of the invention, the plates consisting of fine opaque sheets are placed against each other and held between two thick plates, in order to prevent any deformation of said plates consisting of fine opaque sheets. This is because one difficulty in production is the tendency to the deformation of the fine sheets, which do not have the necessary rigidity and must therefore be placed between thicker supports.  
         [0018]     According to one characteristic of the invention, the plates are separated from each other by layers of a transparent lubricating liquid. This is because, in the contrary case, friction between the plates make correct functioning difficult. Another solution is to use plates which do not touch each other, but this solution is difficult since it requires excellent surface evenness of the plates.  
         [0019]     Sliding of one plate with respect to another can in general take place along two axes. However, the system is simplified, according to one characteristic of the invention, if this sliding takes place along only one axis. In this case, it is possible to use a guide rail to help maintain correct relative positioning of the plates. However, such a rail is expensive and poses problems of positioning. In order to facilitate the relative positioning of the plates, and according to one characteristic of the invention, two adjacent plates sliding with respect to each other along one axis are positioned with respect to each other by microscopic guide rails. A microscopic rail being fragile, it is preferable, according to one characteristic of the invention, to use several microscopic guide rails. These rails can for example be produced by lithography.  
         [0020]     Various solutions can be used for the arrangement of the plates and the distribution of the holes on the plates.  
         [0021]     According to one characteristic of the invention, the modifiable set of pinholes satisfies the following facts: 
        it comprises a first intermediate set of pinholes formed by one or more of said plates, and a second intermediate set of pinholes formed by one or more of said plates,     it comprises a means for making the second intermediate set slide with respect to the first intermediate set so as to pass from a first configuration to a second configuration,     at least one hole in the second intermediate set which is superimposed on a hole in the first intermediate set in the first configuration is not superimposed on a hole in the first intermediate set in the second configuration,        
 
         [0025]     so that the number and/or size of the holes is determined by the number and/or size of the holes in the second intermediate set which are superimposed on the holes in the first intermediate set.  
         [0026]     In this case, the change in configuration is accompanied by a change in the pinhole or pinholes in the second intermediate set which is used. The change in configuration therefore consists of making the plates slide with respect to each other so as to bring a new pinhole in the second intermediate set opposite a pinhole in the first intermediate set. Typically, a discrete number of configurations is used, and the relative movement of the plates takes place step by step.  
         [0027]     According to one characteristic of the invention, the number of holes in the second intermediate set which are superimposed on holes in the first intermediate set in the first configuration differs from the number of holes in the second intermediate set which are superimposed on holes in the first intermediate set in the second configuration, so that the number of holes in the modifiable set of pinholes in the second configuration differs from the number of holes in the modifiable set of pinholes in the first configuration.  
         [0028]     According to one characteristic of the invention, the size of the holes in the second intermediate set which are superimposed on holes in the first intermediate set in the first configuration differs from the size of the holes in the second intermediate set which are superimposed on holes in the first intermediate set in the second configuration, so that the size of the holes in the modifiable set of pinholes in the second configuration differs from the size of the holes in the modifiable set of pinholes in the first configuration.  
         [0029]     These two characteristics of the invention can be combined in order to simultaneously modify the size and number of pinholes. For example, it is possible to use only two plates each constituting an intermediate set, and to vary the size and/or number of holes solely by moving one of these plates along one axis. This solution is effective and simple. However, it is insufficient when it is sought to generate an array of pinholes able to have a high density of pinholes. This is because, in this case, sufficient space is not available on the plate constituting the first intermediate set to conceal the various pinholes in the second intermediate set which must successively be superimposed on the same hole in the first intermediate set. According to one characteristic of the invention, an appropriate solution to this problem consists of continuously moving the plates with respect to each other so that this continuous movement results in a continuous modification of the surface of each pinhole in the modifiable set. It is possible for example to use several identical plates and one reference position for which the pinholes in said several plates are exactly superimposed on each other. So that the reduction in size of the pinholes takes place regularly, it is preferable to generate a translation movement of the i th  plate in a direction oriented at  
         2   ⁢   π     N       
 
 radians in a reference frame common to the N plates constituting the set of pinholes. In the case where N plates are used, the pinholes are preferably polygons with 2N sides, although they can also have other shapes, for example circular. The directions of the translation movement of the plates with respect to each other are then preferably directed along midperpendiculars of the polygons. 
 
         [0031]     According to one characteristic of the invention, the sliding of the plates with respect to each other is obtained by means of an iris diaphragm mechanism. This solution is well adapted to the previous case, where it makes it possible to coordinate the continuous movement of several plates. This iris diaphragm mechanism can, in the case where a rotation of the set of pinholes must be avoided, be supplemented by a supplementary rotation device for compensating for the rotation caused by an iris diaphragm mechanism with a single movable element.  
         [0032]     According to one characteristic of the invention, one of the plates is moved by means of a linear positioner along an axis. This solution is preferred when a technique based on discrete movements is used. It may also be necessary to move one of the plates by means of a two-axis positioner. This solution is one which allows the maximum flexibility.  
         [0033]     When the density of pinholes sought is low, and according to one characteristic of the invention, the modifiable set of pinholes can easily be produced by means of two plates only. In this case it may be a case of thick transparent plates on which the arrays of holes are produced by a lithographic method. This solution is the most simple, in particular because the plates do not deform. However, when the density of pinholes is high, it becomes necessary to use more than two plates, as seen above.  
         [0034]     The modifiable set of pinholes according to the invention may comprise only one pinhole of modifiable size. It is then useful in a single-point confocal microscope. It may, according to one characteristic of the invention, comprise several pinholes of modifiable size, number and/or location, in which case it is useful with a confocal microscope with multipoint illumination. 
     
    
     QUICK DESCRIPTION OF THE FIGURES  
       [0035]      FIG. 1  depicts a fixed plate used in a first embodiment.  
         [0036]      FIG. 2  depicts a movable plate used in this embodiment.  
         [0037]      FIG. 3  depicts the superimposition of the two plates, in this embodiment, forming a single pinhole of small size.  
         [0038]      FIG. 4  depicts the same superimposition in section.  
         [0039]      FIG. 5  depicts a movable plate used in a second embodiment.  
         [0040]      FIG. 6  depicts a fixed plate used in this embodiment.  
         [0041]      FIG. 7  depicts a movable plate used in a third embodiment.  
         [0042]      FIG. 8  depicts a fixed plate used in this third embodiment.  
         [0043]      FIG. 9  depicts a movable plate used in a variant of this third embodiment.  
         [0044]      FIG. 10  depicts a plate used in a fourth embodiment.  
         [0045]      FIG. 11  depicts a device used for preventing leakages of the liquid separating the plates, the device being filled under vacuum.  
         [0046]      FIG. 12  depicts a similar device but comprising an overflow having a breather.  
         [0047]      FIG. 13  depicts a plate used in a fifth embodiment.  
         [0048]      FIG. 14  illustrates the movement of 3 plates in this embodiment.  
         [0049]      FIG. 15  shows a supplementary plate used in this embodiment.  
         [0050]      FIG. 16  shows in front view the device driving 3 identical plates on the principle in  FIG. 14 .  
         [0051]      FIG. 17  shows this device in section, supplemented by a fourth plate.  
         [0052]     FIGS.  18  to  21  relate to a method of guiding the plates by means of microscopic rails.  
         [0053]      FIG. 18  depicts a movable plate carrying rails.  
         [0054]      FIG. 19  depicts a movable plate carrying rails corresponding to those of  FIG. 18 .  
         [0055]      FIG. 20  depicts in section the assembly of two plates produced on plates of thick glass.  
         [0056]      FIG. 21  depicts in section the assembly of two plates produced on metallic sheets. 
     
    
     FIRST EMBODIMENT  
       [0057]     This first embodiment makes it possible to obtain, by step by step sliding, a movable plate  110  constituting a second intermediate set, with respect to a fixed plate  100  constituting a first intermediate set, a single pinhole of modifiable size in the form of a disk.  FIG. 1  depicts the plate  100  comprising a hole  101 .  FIG. 2  depicts the plate  110  comprising holes  111 ,  112 ,  113 ,  114 ,  115  aligned on an axis  116 . The modifiable pinhole is formed by the two plates A and B placed one against the other.  FIG. 3  depicts the modifiable pinhole obtained when the hole  114  is superimposed on the hole  101 .  FIG. 4  depicts the same superimposition in section along a plane passing through the axis  116 . In the position of the plates which is depicted in  FIGS. 3 and 4 , only the hole  114  can have light passing through it, and the diameter of the modifiable hole is that of the hole  114 .  
         [0058]     The plate  110  must be mounted on a positioner making it possible to move it in the direction of the axis  116  passing through the set of holes  111  to  115 . By sliding the plate  110  with respect to the plate  100 , by means of the positioner, it is possible to superimpose any one of the holes  111  to  115  on the hole  101  and therefore to obtain five distinct diameters of the modifiable pinhole. When for example the hole  113 , instead of the hole  114 , is superimposed on the hole  101 , the diameter of the modifiable hole is increased and becomes equal to the diameter of the hole  113 .  
         [0059]     The pinholes in the plate  110  are not necessarily aligned on the same straight line, however this solution makes it possible to move the plate  110  only along one axis, which minimizes costs. In general terms, it is possible to obtain as many holes with different characteristics as there are holes formed in the plate  110 . A guide rail can be used so that the movement of the plate B with respect to the plate A is restricted to the direction of the axis  116 .  
         [0060]     The plates  100  and  110  can be glass plates whose opaque parts are metallic layers obtained by a lithographic process. These metallic layers are shown in thick lines in  FIG. 4 . The two plates are separated by a fine layer  117  of optical liquid, for example oil, in order to prevent any solid rubbing.  
         [0061]     When the optical liquid is maintained solely by capillary attraction, as indicated in  FIG. 4 , the qualities of the layer are liable to degrade over time by partial evaporation, and the liquid is also liable to spread into the parts of the optical system other than the areas where its presence is required. In order to avoid these problems the system can be made impermeable as indicated in  FIG. 14  by means of a flexible closure  500 , for example made from plastic, which closes the whole of the system. The liquid can then be injected under vacuum between the two plates and into the area included inside the flexible closure  500 . This device makes it possible to reconcile the movement of the plates  110  and  100  with the absence of leakages of liquid. One alternative to filling under vacuum is the overflow system depicted in  FIG. 15 . A tube  105  leads into a reservoir  502  provided with a breather and raised up and ensures the maintenance of a level of optical liquid in the area included between the plates.  
         [0062]     In all the embodiments use will preferably be made of glass plates with opaque layers obtained by lithography and turned towards each other, separated by an optical liquid and equipped with a system preventing leakages of liquid. These technological aspects will not be repeated in the remainder of the explanations.  
       SECOND EMBODIMENT  
       [0063]     This second embodiment makes it possible to obtain an array of pinholes of modifiable size by step by step sliding of a movable plate  300  on a fixed plate  310 .  FIG. 5  depicts an example of a plate  300  and  FIG. 6  depicts the corresponding plate  310 . The array of modifiable pinholes is formed by plates  310  and  300  placed against each other. When the hole  301  in the plate  300  is superimposed on the hole  311  in the plate  310 , the orientation of the plates not being modified compared with the drawing, the array of modifiable pinholes has the appearance of the plate  310  alone, that is to say all the holes in the plate  310  are left free by the plate  300 . When the hole  302  in the plate  300  is superimposed on the hole  311  in the plate  310 , the diameter of the holes in the array of modifiable pinholes is decreased. When the holes  303 ,  304 ,  305  are successively superimposed on the hole  311  in the plate  310 , the diameter of the holes in the array of modifiable pinholes is on each occasion decreased. There is therefore in this example an array of modifiable pinholes whose diameter can take 5 distinct values. In general terms, it is possible to produce on this principle an array comprising a large number of pinholes each able to take various sizes or shapes.  
       THIRD EMBODIMENT  
       [0064]     This third embodiment makes it possible to obtain holes of variable size and number by sliding a movable plate  320  carrying a second intermediate set of holes on a fixed plate  330  carrying a first intermediate set of holes.  FIG. 7  depicts an example of a plate  320  used and  FIG. 8  depicts the corresponding plate  330 . When the hole  321  in the plate  320  is superimposed on the hole  331  in the plate  330 , the array of modifiable pinholes has the appearance of the plate  330  alone, that is to say the 12 holes in the plate  330  are left free by the plate  320 . When for example the hole  322  in the plate  320  is superimposed on the hole  331  in the plate  330 , the diameter of the holes in the array of modifiable pinholes is decreased but their number is constant. When the hole  323  in the plate  320  is superimposed on the hole  331  in the plate  330 , the number of pinholes in the set of modifiable pinholes becomes equal to 4 instead of 12, their diameter being equal to that of the holes in the plate  330 , that is to say 6 holes in the plate  330  are concealed by the opaque part of the plate  320 , and the other 4 holes are left free. When the hole  324  in the plate  320  is superimposed on the hole  331  in the plate  330 , the modifiable set of pinholes comprises 4 holes of reduced diameter. This example therefore constitutes a modifiable set of pinholes, the number of pinholes being able to be equal to 4 or 12, and the diameter of each hole being able to take 5 distinct values. In general terms it is possible to produce on this principle a modifiable array comprising a large number of holes, the size and number of which are both modifiable.  
         [0065]     Another example of this embodiment uses the same plate  330  but the second intermediate set is formed by the plate  340  depicted in  FIG. 9 . When the hole  341  in the plate  340  is superimposed on the hole  331  in the plate  330 , the array of pinholes modifiable to the appearance of the plate  330  alone, that is to say the 12 holes in the plate  330 , are left free by the plate  340 . When for example the hole  342  in the plate  340  is superimposed on the hole  331  in the plate  330 , the diameter of the holes in the array of modifiable pinholes is decreased but their number is constant. When the hole  343  in the plate  340  is superimposed on the hole  332  in the plate  330 , the number of pinholes in the set of modifiable pinholes becomes equal to 1 instead of 12, their diameter being equal to that of the holes in the plate  330 , that is to say 11 holes in the plate  330  are concealed by the opaque part of the plate  340  and the other 1 hole is left free. When the hole  344  in the plate  340  is superimposed on the hole  332  in the plate  330 , the modifiable set of pinholes comprises only 1 hole of reduced diameter. This example therefore constitutes a modifiable set of pinholes, the number of pinholes being able to be equal to 1 or 12, and the diameter of each hole being able to take 5 distinct values. This type of array of pinholes is particularly useful in a confocal microscope which it is wished to be able to use both in multipoint mode and in single-point mode.  
       FOURTH EMBODIMENT  
       [0066]     This fifth embodiment makes it possible to obtain square holes of continuously variable size. It uses two identical plates depicted for example by  FIG. 10 . When the hole  401  in the first plate is exactly superimposed on the hole  401  in the second plate a set of square holes equivalent to the first plate alone is obtained. When the two plates are moved with respect to each other along the axis  402 , the size of the square holes resulting from the superimposition of the plates is decreased.  
       FIFTH EMBODIMENT  
       [0067]     This fifth embodiment is particularly adapted to the case where a high density of pinholes is sought. In a basic version, it requires the use of 3 plates which move continuously with respect to each other. They are driven by means of a diaphragm device with modified iris in order to compensate for the rotation of the whole. The pinholes are hexagonal.  
         [0068]     The three plates carry arrays of identical holes which, in a reference position, are superimposed on each other.  FIG. 13  shows a plate  1000  comprising pinholes, for example  1001 . The broken lines, for example  1002 , delimit hexagonal locations not carrying any hole. In the reference position, the appearance of the modifiable set of pinholes is the same as the appearance of each of the plates and is therefore depicted by  FIG. 13 .  
         [0069]     The size of the holes in the modifiable set of pinholes is modified by moving the plates with respect to each other in the manner indicated by  FIG. 14 . This figure depicts part of the array of pinholes. In the figure, the broken lines depict the limits of the pinholes in each of the three plates and the intersection of these holes, which constitutes the effective hole of the modifiable array, has been depicted in white. The arrows show the direction of movement of the plates from the reference position. By moving the plates in the direction of the arrows the width of the holes is decreased continuously. The shape of the holes of the modifiable set of pinholes is not modified when their width decreases. This is due to the fact that there are 3 plates, that the holes have 2×3=6 sides, and that the directions of the movement are along the midperpendiculars of the hexagons.  
         [0070]     In a version also making it possible to modify the density of pinholes, a fourth plate is necessary. This plate is depicted in  FIG. 15 . The set of modifiable pinholes obtained by means of three plates and depicted in  FIG. 13  in the reference position constitutes a first intermediate set. The plate in  FIG. 14  constitutes a second intermediate set. When the hole  1010  in the plate in  FIG. 15  is superimposed on the hole  1001  in the first intermediate set in  FIG. 13 , the density of pinholes is at a maximum. When the hole  1013  in the plate in  FIG. 15  is superimposed on the hole  1001  in the first intermediate set in  FIG. 13 , the number of pinholes per unit surface area is divided by 4. When the hole  1012  in the plate in  FIG. 15  is superimposed on the hole  1001  in the first intermediate set in  FIG. 13 , the number of pinholes per unit surface area is divided by 9. When the hole  1011  in the plate in  FIG. 15  is superimposed on the hole  1001  in the first intermediate set in  FIG. 13 , the number of pinholes per unit surface area is divided by 16.  
         [0071]     The three identical plates depicted in  FIG. 13  can be driven by means of an iris diaphragm drive system depicted in  FIGS. 16 and 17 . The plates in  FIG. 13  are the plates  1040 ,  1041 ,  1042  depicted in FIG.  17 . These plates are metallic sheets tensioned over circular holding rings  1022 ,  1021 ,  1020  and carrying holes produced for example by laser piercing. These three fixing rings are connected to two control rings  1023 ,  1024 . For example, the internal ring  1020  is connected to the control ring  1023  by a bar  1028  turning freely about an axis  1029  fixed in the control ring  1023 . The internal ring  1020  is connected to the control ring  1024  by a bar  1026  turning freely about an axis  1027  fixed in the control ring  1024 . The housing  1031  of the axis  1027  is oversized so as to be able to combine a rotation and translation with respect to the axis  1027 . A tie rod  1030  is used for keeping the housing  1031  in abutment on the axis  1027 . The other two holding rings are connected in a similar manner to the control rings. When the two control rings turn simultaneously in opposite directions and by an equal angle, the three plates move in translation with an angle of 120 degrees between the directions of each movement axis, as indicated in  FIG. 14 .  
         [0072]      FIG. 17  also depicts the fourth plate  1051  which is a sheet tensioned on a holding ring  1050 . The holding ring  1050  is mounted on a two-axis positioner.  
         [0073]     The plates  1051  and  1042  are themselves pressed on thick plates of glass  1052  and  1043 . When the whole of the system is in position the two glass plates  1052  and  1043  prevent deformations of the sheets (plates)  1042 ,  1041 ,  1040 ,  1051  carrying pinholes.  
         [heading-0074]     Method of Guiding and Positioning the Plates  
         [0075]     In certain embodiments the plates carrying pinholes move in translation with respect to each other along a single axis. For example, in the first embodiment, the second and fourth embodiments, and also in the fifth embodiment with regard to the three plates moving by means of an iris diaphragm mechanism. This solution simplifies the system in that each plate moves with respect to another along a single axis. As indicated above a guide rail can be used for guiding the plates. However, a macroscopic guide rail is difficult to produce with the required precision. In order to obtain good positioning of the plates it is possible to replace such a guide rail with a set of microscopic guide rails.  
         [0076]     FIGS.  18  to  20  illustrate the embodiment of a set of microscopic guide rails in a system with two plates of the type described in the first embodiment.  FIG. 18  shows the female part  1101 ,  1102 ,  1103  of the rails, produced by lithography in the same way as the pinholes, on the movable plate.  FIG. 19  shows the male part  1111 ,  1112 ,  1113  of the rails, produced by lithography on the fixed plate, but by means of a supplementary metallic layer.  FIG. 20  shows in section the assembly of the rails  1103  and  1113 . The cross-section is produced along a cutting axis  1114  of the fixed plate and along a cutting axis  1104  of the movable plate, these two axes being deemed to be superimposed in the position depicted. The fixed glass plate  1120  carries a metallic layer  1122  leaving the pinhole  1115  free. It also carries a supplementary metallic layer  1113  constituting the male part of the guidance system. This male part is produced by lithography and the remains of a layer of resin  1125  have also been shown. The object of this layer of resin is to protect the bottom metallic layer  1122  when the rail  1113  is formed. The movable plate  1120  carries a metallic layer  1123  leaving free the pinhole  1105  and the female part  1103  of the guide rail. The space  1123  included between the two plates is filled with a lubricating liquid for preventing solid friction. The male part  1113  fits in the groove  1103  in order to guide the movement. The superimposition of the pinholes  1115  and  1105  produces a pinhole of reduced size.  
         [0077]     This guidance method can be adapted to the case where the plates are metallic sheets, as in the fifth embodiment. In this case male or female rails can be produced on each side of each sheet. The glass plates are then replaced by the metallic sheets. The diagram in  FIG. 21  is equivalent to that in  FIG. 20  but illustrates the case of plates formed by fine metallic sheets. The plate  1134  carries the male rail  1132  separated from the plate by a layer of protective resin  1133  used for producing the rail  1132  by lithography. The plate  1137  carries the female rail  1138  produced by lithography in a metallic layer  1135  separated from the plate by a resin  1139 . The space between the two plates is filled with a lubricating liquid. A guide rail has been shown only on one side of each plate but it is possible to produce one on each side of each plate. In the case of the fifth embodiment, the guide rails which separate each metallic sheet guided by two adjacent sheets participate in the maintenance of the shape of the metallic sheets and in the prevention of deformations. Naturally sheet number  1051  in  FIG. 17  can be guided by this method only if its movement is restricted to a single direction.  
         [heading-0078]     Industrial Applications  
         [0079]     The present set of pinholes can be used in a confocal microscope with single-point or multipoint illumination or in a confocal microscope intended to alternate the two illumination modes. For example, if a set of pinholes of the type described in the fourth embodiment replaces the set of pinholes used in the system described by FIG. 1 of U.S. Pat. No. 5,239,178 it becomes possible to modify the size and number of these pinholes and possibly to alternate between a multipoint and a single-point operating mode. Likewise, the array of pinholes in the fourth embodiment of the present invention can replace, with the same effect, the array of pinholes used in FIG. 3 of the U.S. Pat. No. 5,978,095. By using a modifiable array of pinholes according to the present invention in the microscope described by one of the first two embodiments of French patent application number 0103860 of Mar. 22, 2001, it is possible to easily modify the diameter of the pinholes or their number, which affects the speed/resolution or speed/penetration depth compromise in the sample. The pinhole described in one of the first two embodiments of the present invention can also replace the interchangeable pinholes or the “iris” diaphragms normally used in single-point confocal microscopes with laser scanning.