Abstract:
Disclosed is a counting chamber for optical detection of particles that are present in a fluid, comprising two substantially transparent and substantially parallel plates of material, between which the fluid can be introduced. At least one of the plates includes a visible reference, which comprises a relief formed on the surface of the plate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a counting chamber for optical detection of particles that are present in a fluid, comprising two substantially transparent and substantially parallel plates of material, between which the fluid can be introduced, wherein at least one of said plates includes a visible reference. 
     2. Description of the Related Art 
     Such counting chambers can be used for examining blood, urine or sperm and all other fluids. 
     The term reference is understood to means a visible image, in particular an image which visibly delimits parts of the counting chamber when a person is viewing the counting chamber through a microscope. The particles that are present in the fluid can be quantified in that case by counting or estimating the number of particles that are present in a specific delimited section. 
     The reference can also be a gauge, which is divided into units of length, so that it is possible to determine the size of the particles that are present in the fluid. 
     It is important that the reference, or the image, consists of lines which reduce the visibility of the fluid to a minimum degree. It is possible to use extremely thin lines for that purpose, but such lines are difficult to place and, in addition, they do not show up very well at all times. 
     The object of the invention is to provide a counting chamber including a reference which reduces the degree of visibility in the counting chamber only slightly, and which is nevertheless readily perceptible to the eye. 
     Another object of the invention is to provide a counting chamber which meets the necessary quality requirements, and which can nevertheless be manufactured at low cost. For hygienic reasons, single use is strongly preferred. 
     SUMMARY OF THE INVENTION 
     According to the invention, in order to accomplish that objective, the reference comprises a relief formed on the surface of one of said plates. In practice it has become apparent that a line formed on a surface of at least one of the plates of material in the form of a relief, preferably in the form of a rib projecting from the surface, shows up very well, even if it has a small width, when counting chamber is being viewed through a microscope. 
     Preferably, the two plates of material are inseparably joined together, for example by means of a glued joint, thus providing a relatively inexpensive, disposable product, that is, a counting chamber for single use. 
     Preferably, the relief is formed on the inner surface of one of the plates of material, as a result of which the relief extends into the fluid that is present in the counting chamber, as it were. 
     Such a relief is preferable to a relief that has been formed in a plate of material by, for example, being scratched or etched therein. A thin, straight line is difficult to realise by means of such a method. 
     In one preferred embodiment, said two plates of material and said relief are transparent, wherein the material of the plates is preferably glass. 
     In another preferred embodiment, said material is a plastic. 
     Preferably, said relief consists of a material which extends outwards from the surface of the plate of material, that is, from said plate of material into the space within the counting chamber. 
     In one preferred embodiment, said reference comprises a grid substantially consisting of lines that intersect each other perpendicularly. In that case the space within the counting chamber appears to be divided into sections upon viewing the contents of the counting chamber, and the number of particles in one section can be counted or estimated. 
     When the lines, although being readily visible, consist of a transparent material, it is also possible to perceive the particles that are located on a line, which is advantageous when counting said particles. 
     In another preferred embodiment, said reference comprises a rule provided with a graduation, which makes it possible to determine the size of the particles that are present in said fluid. 
     Preferably, said relief has been formed in a material different from the material of the plate, for example a synthetic material such as an epoxy resin or an acrylate, which has been applied to the material of the plate. Preferably, said other material has been applied to the plate of material in liquid form and subsequently been compressed by means of a stamp, in which a negative of the relief is present. In that case it is possible to form a relief in the shape of thin, straight ribs, which constitute the reference. After the relief has been formed in this manner, said other material can be cured by exposing it to radiation, for example UV radiation. It is also possible to use infrared radiation. 
     In another preferred embodiment, said relief comprises grooves that extend into said other material from the surface thereof. 
     The invention furthermore relates to a method for manufacturing a counting chamber for optical detection of particles that are present in a fluid, wherein two substantially transparent plates of material are joined together in parallel relationship, so that a space is created between said plates, into which said fluid can be introduced, wherein at least one of said plates is previously provided with a visible reference, wherein said reference is formed by forming a relief on the surface of one of said plates. 
     Preferably, a different material in liquid form is applied to said plate of material, after which it is compressed by means of a stamp, in which a negative of said relief is present. Preferably, said other material is cured by exposing it to UV radiation. 
     The invention furthermore relates to a method for optical detection of particles that are present in a fluid, wherein said fluid is introduced into a counting chamber comprising two substantially transparent and substantially parallel plates of material, wherein at least one of said plates is provided with a visible reference, wherein said reference comprises a relief that has been formed on the surface of one of said plates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to explain the invention more fully, an embodiment of a counting chamber will now be explained in more detail with reference to the drawing. 
         FIG. 1  is a top plan view of a counting chamber; 
         FIG. 2  is a side elevation of the counting chamber of  FIG. 1 ; 
         FIG. 3  is a sectional view along line III—III in  FIG. 1 ; and 
         FIG. 4  is a larger-scale detail of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The figures show the embodiment only schematically, and for the sake of clarity the dimensions are not shown in their actual proportions in all cases. 
       FIGS. 1 and 2  show in elevation the counting chamber consisting of two glass plates  1 ,  2 , which are joined by film of glue  3 . Said film of glue  3  does not cover the entire area between the glass plates  1 ,  2 , but only the area  4  in  FIG. 1 , which surrounds an area that forms chamber  5 . 
     Film of glue  3  has a specific thickness, in order to space the glass plates  1 ,  2  a specific, constant distance apart. Said specific thickness of the film of glue  3  can be achieved by putting spherical particles into the glue, for example glass spheres having a diameter equal to the desired distance between glass plates  1 ,  2 . 
     Chamber  5  is enclosed by the two glass plates  1 ,  2  and the film of glue  3 , therefore. It is possible to gain access to chamber  5  from the outside via openings  6 ,  12 . Chamber  5  can be filled through one of said openings  6 ,  12  with a fluid which contains particles that need to be quantified or classified. The other opening  12 ,  6  thereby functions to vent chamber  5 . 
       FIG. 3  is a sectional view of the counting chamber, and  FIG. 4  shows the encircled part  7  of  FIG. 3  on a larger scale, so that the reference  8  that is present on lower glass plate  1  is visible. 
     Reference  8  consists of a film of epoxy resin that has been applied to lower glass plate  1 , in which a relief has been formed. In the illustrated embodiment, said relief consists of two groups of eleven mutually parallel ribs each, which extend perpendicularly to each other. 
       FIG. 4  shows one of said groups of ribs  9  in sectional view. A rib  10  extending perpendicularly thereto is shown in elevation. The circumference of the film of epoxy resin is substantially circular, as is shown in  FIG. 1 . 
     Said two groups of eleven ribs  9 ,  10  each form a grid comprising a hundred square sections, as is shown in  FIG. 1 . Also other patterns comprising more or fewer ribs are possible, wherein the angle that ribs include between themselves may also be an angle other than a straight one. 
     The spacing between the two glass plates  1 ,  2  and the thickness of reference  8  must be selected so that reference  8  and the upper glass plate  2  are spaced a desired distance apart. After all, said spacing determines the amount of fluid that is present within a grid section when chamber  5  is being viewed through a microscope. The number of particles that are present in said amount can be counted or estimated thereby. 
     In  FIG. 1 , reference  8  is shown unproportionally large. The spacing between the ribs of the grid is, for example, 0.001–1 mm. The spacing between the glass plates  1 ,  2  is, for example, 0.1 mm. 
     Reference  8  may also comprise a rule or other gauge provided with a graduation, whether or not in combination with the grid. 
     Reference  8  has been formed on glass plate  1  by compressing a drop of a liquid epoxy resin on glass plate  1  by means of a stamp, in which a negative of the relief is present. The curing process of the epoxy resin can be accelerated by exposing it to UV radiation, which can take place through glass plate  1 . 
     In order to make it easier to detach of the stamp, a suitable substance can be applied to the surface thereof, which is done each time before the stamp comes into contact with the epoxy resin or other material. 
     The illustrated embodiment is merely an example of a counting chamber, also other embodiments are possible.