Patent Publication Number: US-2021187496-A1

Title: Glass container comprising a glass bottom with improved properties

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit under 35 USC § 119 of European Application 19219010.6 filed Dec. 20, 2019, the entire contents of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a glass container and to a plurality of glass containers, wherein the glass container or each glass container contained in the plurality of glass containers is characterized by an advantageous contour of the outer surface of the circular glass bottom. The present invention also relates to a process for the determination of a physical property of a material that is contained in such a glass container and to the use of a glass container or of a plurality of glass containers for determining a physical property of a material contained in the glass container. 
     2. Description of Related Art 
     Glass bottles that are used for pharmaceutical purposes (also known as so-called “vials”) are usually prepared from borosilicate glass by hot-forming a borosilicate glass tube. In such a process in a first step the orifice of the vial is formed from the open tube end, wherein this orifice often has the form of a rolled-rim. Thereafter the vial bottom is formed and simultaneously the vial is separated from the residual of the glass tube. For the formation of the vial bottom the glass tube is, for example, secured in a vertical position by means of upper and lower clamping chucks and is then rotated around its longitudinal axis. The rotating glass tube in a certain region is heated by one or two separating gas burners until the heated mass of glass becomes deformable. As soon as this temperature is reached, the tube—under continuing rotation and heating by means of the burner—is extended in axial direction by means of a linear downwards movement of the lower chuck. Thereby the tube in the heated region extends under simultaneous tapering of its diameter, so that a  constriction region in the form of a glass thread is formed. After the downward movement the constriction region is further heated. In this way the glass tube at the constriction region further contracts by means of the flow pressure of the burner gases so that the glass walls in the heated region melt together and finally the connection between the upper and the lower tube region pulls off. Thus, two tube regions (or sections) with closed ends are generated, wherein the lower tube region is the final vial, and the upper tube region is the residual glass tube from which further vials can be formed. 
     During the above-described thermal separation of the lower and the upper tube region, a mem-brane-like bottom is created. In order to provide a bottom thickness that roughly corresponds to the tube wall thickness, the glass in the bottom region has to be kept liquefied under the most massive supply of heat. However, the centrifugal force prevents the glass from penetrating to the centre of the bottom, i. e. to the centre of rotation. A large part gets stuck at about ⅔ of the bottom radius and forms a typical “ring bead”. 
     Furthermore, when the upper and lower tube regions are drawn apart from each other in the process described above and when in the course of that process a progressive, rotationally symmetrical constriction of the tube occurs until only one thread remains, this tread finally breaks off near its upper end where the gas separation burner are located. The thread essentially falls downwards onto the membrane-like floor in the middle, where it forms an accumulation of glass mass called “the knot”. The minimum bottom thickness is usually found between the ring bead and the knot, the thickest part is usually the knot itself. 
     In addition to the formation of structures such as the “ring bead” and the “knot”, further irregular structures such as ultrafine fissures can also be observed on the outside of the glass bottom. Such structures are often the result of bringing the outer surface of the glass bottom of the glass container into contact with molding tools which in a conventional process for producing glass tubes are used to finally shape the circular glass bottom while still being in a molten state. The roughness of the surface of the molding tools also effects the structure on the outer surface of the glass bottom.  
     It has been observed that state of the art glass containers, particularly the state of art pharmaceutical vials that have been prepared by means of the conventional process as described above can often only be inspected optically through the glass bottom to an insufficient extent in an optical inspection machine. The reason for this limited inspection capability is—in addition to the lens effect of the glass bottom caused by the bottom indentation—a non-uniform structure of the outer surface of the glass bottom, which leads to undesired light refracting effects. As a consequence of these light refracting effects a large number of results cannot be interpreted by these inspection machines and the corresponding glass containers are therefore ejected from the automated process. 
     SUMMARY 
     In general, it is an object of the present invention to at least partly overcome a disadvantage arising from the prior art. It is a particular object of the present invention to provide a glass container, preferably a pharmaceutical vial, that shows an improved inspection capability through the glass bottom, compared to glass containers known from the prior art. Moreover, the glass containers, preferably a pharmaceutical vial, should be characterized in that they can be inspected in an optical inspection machine with a reduced number of glass containers that are ejected because the result obtained by optical inspection of that glass container cannot be interpreted. 
     A contribution to solving at least one of the objects according to the invention is made by an embodiment 1 of a glass container comprising as container parts: a glass tube with a first end, a further end, an outer diameter d 1 , an inner diameter d 2  and a glass thickness s 1 , the glass tube being characterized by a longitudinal axis L tube  that passes through the centre of the first and the further end; a circular glass bottom, wherein the circular glass bottom closes the glass tube at the first end, wherein the circular glass bottom comprises an inner surface directed to the inside of the glass container, an outer surface directed to the outside of the glass container and a centre; a curved glass heel extending from an outer end of the circular glass bottom to the first end of the glass tube; wherein at least one, preferably both of the following conditions (α) and (β) is/are fulfilled: 
     (α) if h(x,y) is the two-dimensional distance between a contact plane representing the ground on which the glass container rests with the circular glass bottom being at least partially in contact with the ground, and the outer surface of the circular glass  bottom at a given position x,y, with x=0 and y=0 in the centre of the circular glass bottom, the two-dimensional distance being measured in a direction that is parallel to the longitudinal axis L tube , wherein 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}
 
     is the slope magnitude of the outer surface of the circular glass bottom at the given position x,y, the 75% quantile of the values that have been determined for the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta 
 
     for all given positions x,y within a circular area having a radius of 0.4×d 2 /2 and a centre that corresponds to the centre of the glass bottom, is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm, wherein adjacent positions x,y increase stepwise by 200 μm and wherein h(x,y) delta =h (x,y) max −h(x,y) min , h(x,y) max  being the maximum value for h(x,y) and h(x,y) min  being the minimum value for h(x,y) being determined in that circular area; 
     (β) for the wavefront distortion W( ,φ) of a laser light with a wave length of 520 nm, a beam width of at least 0.6×d 2  and less than 0.85×d 2 , that passes through the circular glass bottom in a direction from the outer surface to the inner surface, that is aligned collinear with L tube  and that has been corrected for piston, tilt and defocus, the peak to valley difference 
       (W( ,φ) corrected ) max −(W( , φ) corrected ) min 
 
     is less than 100 waves, preferably less than 80 waves, more preferably less than 60 waves, even more preferably less than 40 waves, even more preferably less than 30 waves, even more preferably less than 20 waves and even more preferably less than 10 waves. 
     A contribution to solving at least one of the objects according to the invention is also made by an embodiment 1 of a plurality of glass containers, each glass container comprising as contain-er parts a glass tube with a first end, a further end, an outer diameter d 1 , and an inner diameter d 2  and a glass thickness s 1 , the glass tube being characterized by a longitudinal axis L tube  that passes through the centre of the first and the further end; a circular glass bottom, wherein the circular glass bottom  closes the glass tube at the first end, wherein the circular glass bottom comprises an inner surface directed to the inside of the glass container, an outer surface directed to the outside of the glass container and a centre; a curved glass heel extending from an outer end of the circular glass bottom to the first end of the glass tube; wherein at least one, preferably both of the following conditions (α) and (β) is/are fulfilled: 
     (α) if h(x,y) is the two-dimensional distance between a contact plane representing the ground on which the glass container rests with the circular glass bottom being at least partially in contact with the ground, and the outer surface of the circular glass bottom at a given position x,y, with x=0 and y=0 in the centre of the circular glass bottom, the two-dimensional distance being measured in a direction that is parallel to the longitudinal axis L tube , wherein 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}.
 
     is the slope magnitude of the outer surface of the circular glass bottom at the given position x,y, for at least 90%, more preferably for at least 95%, even more preferred for at least 99% and most preferably for 100% of the glass containers in the plurality of glass containers the 75% quantile of the values that have been determined for the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     for all given positions x,y within a circular area having a radius of 0.4×d 2 /2 and a centre that corresponds to the centre of the glass bottom is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm, wherein adjacent positions x,y increase stepwise by 200 μm and wherein h(x,y) delta =h(x,y) max −h(x,y) min , h(x,y) max  being the maximum value for h(x,y) and h(x,y) min  being the minimum value for h(x,y) being determined in that circular area; 
     (β) for the wavefront distortion W( ,φ) of a laser light with a wave length of 520 nm, a beam width of at least 0.6×d 2  and less than 0.85×d 2 , that passes through the circular glass bottom in a direction from the outer surface to the inner surface, that is aligned collinear with L tube  and that has been corrected for piston, tilt and defocus, for at least 90%, more preferably for at least 95%, even more preferred for at least 99% and most preferably for 100%  the peak to valley difference 
       (W( , φ) corrected ) max −(W( ,φ) corrected ) min 
 
     is less than 100 waves, preferably less than 80 waves, more preferably less than 60 waves, even more preferably less than 40 waves, even more preferably less than 30 waves, even more preferably less than 20 waves and even more preferably less than 10 waves. 
     As used herein, the phrase “plurality of glass containers” in the sense of the present invention preferably comprises at least 10 glass containers, preferably at least 25 glass containers, more preferably at least 50 glass containers, even more preferably at least 75 glass containers and most preferably at least 100 glass containers. Preferably, the plurality of glass containers comprises at most 1000 glass container, more preferably at most 500 glass containers. Furthermore, the plurality of glass containers preferably has been collected arbitrarily and particularly has not been selected with regard to any property. For example, the plurality of glass containers may be the group of containers which are packed together in a typical transport tray. 
     According to a first particular embodiment of the glass container according to the present invention condition or the plurality of glass containers according to the present invention (α) is fulfilled. According to a second particular embodiment of the glass container according to the present invention or the plurality of glass containers according to the present invention condition (β) is fulfilled. According to a third particular embodiment of the glass container according to the present invention or the plurality of glass containers according to the present invention conditions (α) and (β) are fulfilled. 
     If the circular glass bottom of a glass container, particularly the circular glass bottom of a vial, is characterized by an outer surface the contour of which is characterized in that the 75% quantile of the values that have been determined for the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     for all given positions x,y within a circular area having a radius of 0.4×d 2 /2 and a centre that corresponds to the centre of the glass bottom is less than 4100 μm/mm, it has surprisingly been discovered that the inspection capability through the glass bottom can be significantly increased compared to circular glass bottoms of glass containers known from the prior art.  
     In an embodiment 2 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to its embodiment 1, wherein the 75% quantile of the values that have been determined for the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta 
 
     within a circle having a radius of 0.6×d 2 /2 and a centre that corresponds to the centre of the glass bottom is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm. 
     In an embodiment 3 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to its embodiment 1 or 2, wherein the 75% quantile of the values that have been determined for the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta 
 
     within a circle having a radius of 0.8×d 2 /2 and a centre that corresponds to the centre of the glass bottom is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm. 
     In an embodiment 4 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 3, wherein h(x,y) delta  is at least 30 μm, preferably at least 50 μm, more preferably at least 75 μm and even more preferably at least 100 μm. 
     In an embodiment 5 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 4, wherein for the wavefront distortion W( ,φ) of a laser light with a wave  length of 520 nm, a beam width of at least 0.6×d 2  and less than 0.85×d 2 , that passes through the circular glass bottom in a direction from the outer surface to the inner surface, that is aligned collinear with L tube  and that has been corrected for piston, tilt and defocus, the peak to valley difference 
       (W( ,φ) corrected ) max −(W( ,φ) corrected ) min 
 
     is less than 100 waves, preferably less than 80 waves, more preferably less than 60 waves, even more preferably less than 40 waves, even more preferably less than 30 waves, even more preferably less than 20 waves and even more preferably less than 10 waves. 
     In an embodiment 6 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiment 1 to 5, wherein for the wavefront distortion W( ,φ) of a laser light with a wave length of 520 nm, a beam width of at least 0.6×d 2  and less than 0.85×d 2 , that passes through the circular glass bottom in a direction from the outer surface to the inner surface, that is aligned collinear with L tube  and that has been corrected for piston and tilt, the corrected wavefront distortion is point symmetric and wherein for a fixed set of radii    0 =¼,    0 =½ and    0 =1, the azimuthal peak to valley difference 
       (W( ,φ) corrected ) max −(W( ,φ) corrected ) min 
 
     is less than 100 waves, preferably less than 80 waves, more preferably less than 60 waves, even more preferably less than 40 waves, even more preferably less than 30 waves, even more preferably less than 20 waves and even more preferably less than 10 waves. 
     In an embodiment 7 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 6, wherein at least within the range from x=−0.4×d 2 /2 to x=+0.4×d 2 /2 the maximum value for ĥ(x) that the fitted curvature function takes on in that range is ĥ(x) max , ĥ(x) max  being in the range from 0.01 to 0.25 mm when d 1  is in the range from 6 to 14 mm, ĥ(x) max  being in the range from 0.3 to 0.5 mm when d 1  is in the range from 16 to 24 mm and ĥ(x) max  being in the range from 1 to 2 mm when d 1  is in the range from 30 to 50 mm. ĥ(x) usually reaches its maximum value ĥ(x) max  at the centre of the circular glass bottom (x=0). According to a particular embodiment of the glass container or the plurality of glass containers  according to the present invention value ĥ(x) max  represents the bottom indentation t. 
     In an embodiment 8 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 7, wherein the topography of the outer surface of the circular glass bottom is defined by a function ĥ(x), wherein ĥ(x) is the azimuthal average of the distance h between a contact plane representing the ground on which the glass container rests with at least a part of the circular glass bottom being in contact with the ground, and the outer surface of the circular glass bottom at any given position that is located on a circle having the centre and the radius |x|, wherein individual values ĥ are determined for a plurality of circles the radius of which increases stepwise by 500 μm, starting with a circle around the centre having a radius of 500 μm, and wherein the individual values ĥ are determined in the range from x=−0.4×d 2 /2 to x=+0.4×d 2 /2, d 2  having a size such that at least 4 values ĥ, more preferably at least 5 values ĥ, even more preferably at least 6 valuesĥ and most preferably at least 10 values ĥ are determined, wherein the thus obtained individual values ĥ can be fitted in a least square fit with a curvature function (I) 
     
       
         
           
             
               
                 
                   
                     
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     wherein c and h 0  being free fitting parameters, and 
     wherein Δc is the standard deviation error for constant c when fitting the individual values ĥ(x) with curvature function (I) and wherein the relative standard deviation error Δc/c is less than 0.1. 
     In an embodiment 9 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to its embodiment 8, wherein for the individual values ĥ that have been determined in the range from x=−0.6×d 2 /2 to x=+0.6×d 2 /2 the relative standard deviation error Δc/c is less than 0.1. 
     In an embodiment 10 of the glass container or the plurality of glass containers according to the invention the glass container or in the plurality of glass containers is designed according to its embodiment 8 or 9, wherein for the individual values ĥ that have been determined in the range from x=−0.8×d 2 /2 to x=+0.8×d 2 /2 the relative standard deviation error Δc/c is less than 0.1.  
     In an embodiment 11 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 8 to 10, wherein for the individual values ĥ that have been determined in the range from x=−0.4×d 2 /2 to x=+0.4×d 2 /2 the relative standard deviation error Δc/c is less than 0.09. 
     In an embodiment 12 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 8 to 11, wherein for the individual values ĥ that have been determined in the range from x=−0.6×d 2 /2 to x=+0.6×d 2 /2 the relative standard deviation error Δc/c is less than 0.09. 
     In an embodiment 13 of the glass container or the plurality of glass containers according to the invention the glass container or in the plurality of glass containers is designed according to anyone of its embodiments 8 to 12, wherein for the individual values ĥ that have been determined in the range from x=−0.8×d 2 /2 to x=+0.8×d 2 /2 the relative standard deviation error Δc/c is less than 0.09. 
     In an embodiment 14 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 8 to 13, wherein the relative standard deviation error Δc/c is less than 0.08, preferably less than 0.07, more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03. 
     In an embodiment 15 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 14, wherein for any cut surface of the circular glass bottom that is obtainable by cutting the circular glass bottom in a plane that includes the longitudinal axis L tube  the following condition is fulfilled: s 2   max /s 1 ×(s 2   max /s 2   min −1)≤1.1; preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤1.0; more preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.9; even more  preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.8; even more preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.7; even more preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.6; even more preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.5; even more preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.4; even more preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.3; even more preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.2; most preferably s 2   max /s 1 ×(s 2   max /s 2   min −1)≤0.1; wherein s 2   max  corresponds to the maximum glass thickness of the circular glass bottom and s 2   min  to the minimum glass thickness of the circular glass bottom as determined within a given cut surface at least within the range from x=−0.4×d 2 /2 to x=+0.4×d 2 /2, the centre of the circular glass bottom being at position x=0, wherein s 2   min  and s 2   max  are both measured in a direction that is parallel to the longitudinal axis L tube . 
     In an embodiment 16 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to its embodiment 15, wherein s 2   max  and s 2   min  are determined within a given cut surface at least within the range from x=−0.6×d 2 /2 to x=+0.6×d 2 /2. 
     In an embodiment 17 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to its embodiment 15 or 16, wherein s 2   max  and s 2   min  are determined at least within a given cut surface within the range from x=−0.8×d 2 /2 to x=+0.8×d 2 /2. 
     In an embodiment 18 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 17, wherein the glass container comprises a top region in which the inner diameter is d 4  and a body region in which the inner diameter of the glass tube is d 2 , wherein d 2 &gt;d 4  and wherein the glass container comprises a shoulder that connects the body region with the top region. Preferably, the shoulder is characterized by a shoulder angle α, wherein α is in the range from 10 to 70°, preferably in the range from 15 to 60°, more preferably in the range from 20 to 50°, even more preferably in the range from 25 to 40° and most preferably in the range from 27° to 33°.  
     In an embodiment 19 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to its embodiment 18, wherein the glass container in the container part from the glass bottom up to the shoulder is rotation-symmetric around the longitudinal axis L tube  that goes perpendicular through the centre of the glass bottom. 
     In an embodiment 20 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to its embodiment 18 or 19, wherein d 4  is in the range from 5 to 20 mm, preferably in the range from 7 to 14 mm and more preferably in the range from 6 to 8 mm. 
     In an embodiment 21 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 18 to 20, wherein throughout the body region the glass thickness s 1  of the glass tube is in a range from ±0.2 mm, preferably ±0.1 mm, more preferably ±0.08 mm and most preferably ±0.05 mm, in each case based on a mean value of this glass thickness in the body region. 
     In an embodiment 22 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 21, wherein d 2  is in the range from 10 to 60 mm, preferably in the range from 12 to 50 mm, more preferably in the range from 12 to 30 mm, even more preferably in the range from 12 to 25 mm and most preferably in the range from 12 to 17 mm. 
     In an embodiment 23 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 22, wherein s 1  is in the range from 0.5 to 3.0 mm, preferably in the range from 0.7 to 1.8 mm, more preferably in the range from 0.8 to 1.2 mm, even more preferably in the range from 0.9 to 1.1 mm and most preferably in the range from 0.95 to 1.05 mm. 
     In an embodiment 24 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 23, wherein the glass container has a mass of glass m g  and an interior  volume V i  and wherein the following condition is fulfilled: m g /V i   0.75 &lt;2.0, preferably m g /V i   0.75 &lt;1.75. 
     In an embodiment 25 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 24, wherein the glass container has an interior volume V i  in a range from 2 to 150 ml, preferably from 3 to 100 ml, more preferably from 3 to 50 ml, even more preferably from 3 to 15 ml, most preferably from 3 to 7 ml. 
     In an embodiment 26 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 25, wherein the glass container has a height h 1  in the range from 15 to 100 mm, preferably in the range from 20 to 60 mm, more preferably in the range from 25 to 55 mm, even more preferably in the range from 30 to 50 mm and most preferably in the range from 34 to 46 mm. 
     In an embodiment 27 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 26, wherein d 1  is in the range from 13 to 65 mm, preferably in the range from 15 to 55 mm, more preferably in the range from 15 to 35 mm, even more preferably in the range from 15 to 30 mm and most preferably in the range from 15 to 20 mm. 
     In an embodiment 28 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 27, wherein at least one of the properties of the glass container selected from the group consisting of s 1 , d 1 , h 1  and t is within the requirements defined in DIN EN ISO 8362-1:2016-06. 
     In an embodiment 29 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 28, wherein the glass container is a packaging container for a medical or a pharmaceutical packaging good or both. A preferred pharmaceutical packaging good is a  pharmaceutical composition. Preferably, the glass container  1  is suitable for packaging parenteralia in accordance with section 3.2.1 of the European Pharmacopoeia, 7th edition from 2011. 
     In an embodiment 30 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 29, wherein the glass container is a vial. 
     In an embodiment 31 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 30, wherein the glass is of a type selected from the group consisting of a borosilicate glass, an aluminosilicate glass, soda lime glass and fused silica. As used herein the term “Soda lime glass” according to the invention is an alkaline/alkaline earth/silicate glass according to table 1 of ISO 12775 (1 st  edition 1997-10-15). 
     In an embodiment 32 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 31, wherein the glass container comprises a pharmaceutical composition. 
     In an embodiment 33 of the glass container or the plurality of glass containers according to the invention the glass container or the plurality of glass containers is designed according to anyone of its embodiments 1 to 32, wherein the glass container comprises a closure at the top of the glass container, preferably a lid. 
     A contribution to solving at least one of the objects according to the invention is also made by a process for the determination of a physical property of a material that is contained in a glass container comprising as process step: 
     providing a glass container or a plurality of glass containers according to anyone of embodiments 1 to 33, wherein the glass container or each glass container in the plurality of glass containers contains the material;  
     determining the physical property of the material by a radiation that passes through the bottom of the glass container. 
     In an embodiment 2 of the process according to the invention the process is designed according to its embodiment 1, wherein the material is a pharmaceutical composition, preferably a liquid or solid pharmaceutical composition, more preferably a freeze-dried product or a liquid comprising at least one drug dissolved or dispersed therein. 
     In an embodiment 3 of the process according to the invention the process is designed according to its embodiment 1 or 2, wherein the physical property of the material is determined by radiation in an optical inspection machine, preferably in an automated optical inspection machine. 
     In an embodiment 4 of the process according to the invention the process is designed according to anyone of its embodiment 1 to 3, wherein the physical property is selected from the group consisting of the transmission, the colour, the refractive index and the absorption at a given wavelength of electromagnetic radiation. 
     A contribution to solving at least one of the objects according to the invention is also made by the use of a glass container or a plurality of glass containers according to anyone of embodiments 1 to 33 for determining a physical property of a material contained in the glass container. 
     Process For Producing the Glass Container 
     The glass container according to the present invention or the glass containers contained in the plurality of glass containers according to the present invention is preferably produced by means of an embodiment 1 of a process for the preparation of a glass container from a glass tube in a glass processing machine, wherein the glass tube comprises a first portion with a first end, a second portion with a second end and a longitudinal axis L tube  that passes through the centre of the first and the second end, wherein the glass processing machine comprises a plurality of processing stations and pairs of first and second clamping chucks which are adapted and arranged to hold the glass tube while rotating the glass tube around its longitudinal axis L tube  and to transport the rotating glass tube from one glass container processing station to the next one, wherein the first clamping chucks hold  the glass tube at first portion and the second clamping chucks hold the glass tube at the second portion, wherein the process comprises the steps of heating the glass tube at a defined position between the first portion and the second portion by means of at least one separation gas burner to a temperature above the glass transition temperature, preferably above its softening temperature, while the glass tube is rotating around its longitudinal axis L tube ; pulling apart the first portion and the second portion of the heated glass tube, while the heated glass tube is still rotating around its longitudinal axis L tube , in a direction that is substantially parallel to the longitudinal axis L tube  by moving the first and the second clamping chucks away from each other, thereby forming a glass thread and separating the first portion from the second portion by pulling apart the glass thread, the part of the mass of the glass thread that remains at a portion of the glass tube forming a circular bottom at one end of that portion; characterized in that, while moving away the first and the second clamping chucks in process step III), at least one separation gas burner follows at least one portion of the glass tube selected from the first portion and the second portion in a direction that is substantially parallel to the direction in which the first and the second clamping chucks are moved away from each other, the at least one separation gas burner thereby following the one end of at least one portion of the glass tube selected from the first portion and the second portion. 
     Surprisingly, it has been discovered that—if at least one separation gas burner follows at least one portion of the glass tube in the separation process—an advantageous bottom geometry of the glass container can be obtained, compared to the bottom geometry obtained in a prior art process in which the separation gas burners remain in a fixed position. The present invention thus simplifies the production of vials by creating the required bottom geometry during the separation process and thereby enables a new, unprecedented quality of the bottom geometry that is ideal for automated inspection processes, both unfilled and filled. 
     As used herein, the term “softening temperature” of the glass is the temperature at which the glass has a viscosity (determined according to ISO 7884-6:1987) of 10 7.6  dPa×sec. 
     In an embodiment 2 of the process for the preparation of a glass container, the process is designed according to its embodiment 1, wherein in process step II) two diametrically opposed  separation gas burners are used which are arranged such that the glass tube rotates centrally between the two flames generated by these two separation gas burners. 
     In an embodiment 3 of the process for the preparation of a glass container, the process is designed according to its embodiment 1 or 2, wherein the first and second clamping chucks are adapted and arranged to hold the glass tube in a vertical position; wherein the first portion of the glass tube corresponds to the lower portion of the glass tube having a lower end and the second portion of the glass tube corresponds to the upper portion of the glass tube having an upper end; wherein the first clamping chucks are arranged as upper clamping chucks holding the upper portion of the glass tube and the second clamping chucks are arranged as lower clamping chucks holding the lower part of the glass tube; wherein in process step III) the lower portion of the glass tube is pulled downwards by moving downwards the lower clamping chucks and wherein, while pulling downwards the lower portion, the at least one separation gas burner is moved downwards in a direction that is substantially parallel to the direction in which the lower clamping chucks are moved downwards, the at least one separation gas burner thereby following the upper end of the lower portion. 
     In an embodiment 4 of the process for the preparation of a glass container, the process is designed according to its embodiment 3, wherein in process step III) the lower clamping chucks are moved downwards at a point of time t and the at least one separation gas burner is moved downwards at a point of time t′=t+Δt. 
     In an embodiment 5 of the process for the preparation of a glass container, the process is designed according to its embodiment 4, wherein Δt=0 sec. In this particular embodiment of the process the at least one separation gas burner and the lower clamping chucks (and thus also the lower portion of the glass tube) are moved downwards simultaneously. 
     In an embodiment 6 of the process for the preparation of a glass container, the process is designed according to its embodiment 4, wherein Δt is in the range from 0.01 to 1.0 sec, preferably in the range from 0.03 to 0.8 sec, more preferably in the range from 0.05 to 0.4 sec and even more preferably in the range from 0.1 to 0.2 sec.  
     In an embodiment 7 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 2 to 6, wherein in process step III) the at least one separation gas burner is moved downwards starting from a position Y′ 0  to a stop position Y′ stop  and the lower clamping chucks is moved downwards starting from a position Y 0  and, preferably after the at least one separation gas burner has stopped at position Y′ stop , to stop at a position Y stop . 
     In an embodiment 8 of the process for the preparation of a glass container, the process is designed according to its embodiment 7, wherein |Y′ stop −Y′ 0 |&lt;|Y stop −Y 0 |. According to this embodiment it is thus preferred that the distance with which the at least one separation gas burner is moved downwards is smaller than the distance with which the lower clamping chucks are moved downward. 
     In an embodiment 9 of the process for the preparation of a glass container, the process is designed according to its embodiment 8, wherein (|Y′ stop −Y′ 0 |/|Y stop −Y 0 |) (i. e. the ratio of the distance with which the burner has been moved downwards to the distance with which the lower clamping chucks have been moved downwards) is in the range from 0.1 to 1, preferably in the range from 0.2 to 0.95, more preferably in the range from 0.3 to 0.9, even more preferably in the range from 0.4 to 0.85, even more preferably in the range from 0.5 to 0.8 and most preferably in the range from 0.6 to 0.75. 
     In an embodiment 10 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 2 to 9, wherein the downward movements of the at least one separation gas burner and the lower clamping chucks are independent from each other. In this context it is particularly preferred that the downward movements of the at least one separation gas burner and the lower clamping chucks are accomplished through independent servo drives. 
     In an embodiment 11 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 2 to 10, wherein the downward movements of the at least one separation gas burner and the lower clamping chucks are both linear synchronous with each other.  
     In an embodiment 12 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 2 to 11, wherein the distance between the at least one separation gas burner and the upper end of the lower portion is kept constant when the at least one separation gas burner follows the upper end of the lower portion. 
     In an embodiment 13 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 2 to 12, wherein the outer surface of the upper end of the lower portion does not come into contact with any part of the glass processing machine while the final shape of the circular glass bottom is formed. 
     In an embodiment 14 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 2 to 13, wherein after process step III) in a further process step IV) the thickness of the glass in the circular glass bottom is equalized by heating the circular glass bottom, while still having a temperature above the glass transition temperature and while still rotating the lower portion of the glass tube around its longitudinal axis L tube , with at least one bottom shaping gas burner, thereby forming the final shape of the circular glass bottom. 
     In an embodiment 15 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 2 to 13, wherein after process step III) in a further process step IV) the thickness of the glass in the circular glass bottom is equalized by bringing the outer surface of the circular glass bottom, while still having a temperature above the glass transition temperature and while still rotating the lower portion of the glass tube around its longitudinal axis L tube , into contact with a molding tool, thereby forming the final shape of the circular glass bottom. 
     In an embodiment 16 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 2 to 13, wherein after process step III) in a further process step IV) the thickness of the glass in the circular glass bottom is equalized by heating the circular glass bottom, while still having a temperature above the glass transition temperature and while still rotating the lower portion of the glass tube around its longitudinal axis L tube , with at least one bottom shaping gas burner, followed by a process step of bringing the outer surface of the circular glass bottom, while still having a temperature above the glass transition temperature and  while still rotating the lower portion of the glass tube around its longitudinal axis L tube , into contact with a molding tool, thereby forming the final shape of the circular glass bottom. 
     In an embodiment 17 of the process for the preparation of a glass container, the process is designed according to anyone of its embodiments 14 to 16, wherein the process comprises the further process step of heating the lower portion of the glass tube at the lower end by means of at least one further gas burner to a temperature above its glass transition temperature while rotating the glass tube around its longitudinal axis L tube  and forming an orifice, preferably an orifice in the form of a flange or a rolled rim, at the lower end of the glass tube, wherein the processing stations of the glass processing machine are arranged along at least one circle, wherein the glass tube is passed along this circle from one processing station to the next one while rotating around its longitudinal axis L tube , and wherein process steps I) to IV) are all carried out at processing stations which are arranged within the same circle. 
     Glass Container 
     The glass container according to the invention or the glass container contained in the plurality of glass containers according to the invention may have any size or shape which the skilled person deems appropriate in the context of the invention. Preferably, the top region of the glass container comprises an opening, which allows for inserting a pharmaceutical composition into the interior volume of the glass container. A preferred glass container is a pharmaceutical glass container, more preferably one selected from the group consisting of a vial, an ampoule or a combination thereof, wherein a vial is particularly preferred. 
     For the use in this document, the interior volume V i  represents the full volume of the interior of the glass container. This volume may be determined by filling the interior of the glass container with water up to the brim and measuring the volume of the amount of water which the interior can take up to the brim. Hence, the interior volume as used herein is not a nominal volume as it is often referred to in the technical field of pharmacy. This nominal volume may for example be less than the interior volume by a factor of about 0.5. 
     The following are particularly preferred embodiments of the glass container according to the  present invention (or of the glass container contained in the plurality of glass containers according to the present invention). When reference is made to the relative standard deviation error Δc/c, the values for Δc and c are preferably determined by fitting the individual values ĥ (x) that have been obtained within the range from x=−0.8×d 2 /2 to x=+0.8×d 2 /2 with curvature function (I). When reference is made to the 75% quantile of the values that have been determined for the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta ,
 
     this term has been determined for all given positions x,y within a circular area having a radius of 0.8×d 2 /2. When reference is made to the parameters s 2   max /s 1 ×(s 2   max /s 2   min −1), the corresponding value is also preferably determined within the range from x=−0.8×d 2 /2 to x=+0.8×d 2 /2. 
     According to a first preferred embodiment of the glass container according to the present invention (or of the glass container contained in the plurality of glass containers according to the present invention) the glass container is a vial with an overflow capacity equal to or larger than 1 ml up to maximal 5 ml, preferably a vial with a size designation “2R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is in the range from 0.4 to 2 mm, preferably in the range from 0.8 to 1.3 mm and more preferably in the range from 0.9 to 1.15 mm; d 1  is in the range from 13 to 19 mm, preferably in the range from 14 to 18 mm and more preferably in the range from 15 to 17 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.01 to 0.75 mm, preferably in the range from 0.05 to 0.5 mm and even more preferably in the range from 0.08 to 0.12 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more  preferably less than 0.5. 
     According to a second preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 4 ml up to maximal 8 ml, preferably a vial with a size designation “4R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is preferably in the range from 0.9 to 1.15 mm; d 1  is in the range from 13 to 19 mm, preferably in the range from 14 to 18 mm and even more preferably in the range from 15 to 17 mm; Δc/c less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.01 to 0.75 mm, preferably in the range from 0.05 to 0.5 mm and even more preferably in the range from 0.08 to 0.12 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to a third preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 8 ml up to maximal 10.75 ml, preferably a vial with a size designation “6R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is preferably in the range from 0.9 to 1.15 mm; d 1  is in the range from 19 to 25 mm, preferably in the range from 20 to 24 mm and even more preferably in the range from 21 to 23 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.01 to 0.75 mm, preferably in the range from 0.05 to 0.5 mm and even more preferably in the  range from 0.08 to 0.12 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to a fourth preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 10.75 ml up to maximal 12.5 ml, preferably a vial with a size designation “8R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is preferably in the range from 0.9 to 1.15 mm; d 1  is in the range from 19 to 25 mm, preferably in the range from 20 to 24 mm and even more preferably in the range from 21 to 23 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.01 to 0.75 mm, preferably in the range from 0.05 to 0.5 mm and even more preferably in the range from 0.08 to 0.12 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to a fifth preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 12.5 ml up to maximal  16.25 ml, preferably a vial with a size designation “10R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is preferably in the range from 0.9 to 1.15 mm; d 1  is in the range from 21 to 27 mm, preferably in the range from 22 to 26 mm and even more preferably in the range from 23 to 25 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.01 to 0.75 mm, preferably in the range from 0.05 to 0.5 mm and even more preferably in the range from 0.08 to 0.12 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to a sixth preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 16.25 ml up to maximal 22.5 ml, preferably a vial with a size designation “15R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is in the range from 0.4 to 2 mm and preferably in the range from 0.9 to 1.15 mm; d 1  is in the range from 21 to 27 mm, preferably in the range from 22 to 26 mm and even more preferably in the range from 23 to 25 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.01 to 0.75 mm, preferably in the range from 0.05 to 0.5 mm and even more preferably in the range from 0.08 to 0.12 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than  3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to a seventh preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 22.5 ml up to maximal 29.25 ml, preferably a vial with a size designation “20R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is in the range from 0.5 to 2.5 mm, preferably in the range from 0.9 to 1.6 mm and even more preferably in the range from 1.15 to 1.25 mm; d 1  is in the range from 27 to 33 mm, preferably in the range from 28 to 32 mm and even more preferably in the range from 29 to 31 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.05 to 0.75 mm, preferably in the range from 0.1 to 0.5 mm and even more preferably in the range from 0.15 to 0.25 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to an eighth preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 29.25 ml up to maximal 35 ml, preferably a vial with a size designation “25R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following  conditions is/are fulfilled: s 1  is in the range from 0.5 to 2.5 mm, preferably in the range from 0.9 to 1.6 mm and even more preferably in the range from 1.15 to 1.25 mm; d 1  is in the range from 27 to 33 mm, preferably in the range from 28 to 32 mm and even more preferably in the range from 29 to 31 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.05 to 0.75 mm, preferably in the range from 0.1 to 0.5 mm and even more preferably in the range from 0.15 to 0.25 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to a ninth preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 35 ml up to maximal 49.75 ml, preferably a vial with a size designation “30R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is in the range from 0.5 to 2.5 mm, preferably in the range from 0.9 to 1.6 mm and even more preferably in the range from 1.15 to 1.25 mm; d 1  is in the range from 27 to 33 mm, preferably in the range from 28 to 32 mm and even more preferably in the range from 29 to 31 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.05 to 0.75 mm, preferably in the range from 0.1 to 0.5 mm and even more preferably in the range from 0.15 to 0.25 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than  3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to a tenth preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 49.75 ml up to maximal 92.5m1, preferably a vial with a size designation “50R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following conditions is/are fulfilled: s 1  is in the range from 0.4 to 2.5 mm, preferably in the range from 1.3 to 1.8 mm and even more preferably in the range from 1.45 to 1.55 mm; d 1  is in the range from 37 to 43 mm, preferably in the range from 38 to 42mm and even more preferably in the range from 39 to 41 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.075 to 1.2 mm, preferably in the range from 0.1 to 0.75 mm and even more preferably in the range from 0.15 to 0.25 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     According to an eleventh preferred embodiment of the glass container according to the present invention the glass container is a vial with an overflow capacity of larger than 92.5 ml up to maximal 150 ml, preferably a vial with a size designation “100R” according to DIN EN ISO 8362-1:2016-06, wherein it is furthermore preferred that at least one, preferably all of the following  conditions is/are fulfilled: s 1  is in the range from 0.4 to 2.5 mm, preferably in the range from 1.3 to 1.8 mm and even more preferably in the range from 1.65 to 1.75 mm; d 1  is in the range from 44 to 50 mm, preferably in the range from 45 to 49 mm and even more preferably in the range from 46 to 48 mm; Δc/c is less than less than 0.1, preferably less than 0.09, more preferably less than 0.08, even more preferably less than 0.07, even more preferably less than 0.06, even more preferably less than 0.05, even more preferably less than 0.04 and even more preferably less than 0.03; ĥ(x) max  is in the range from 0.075 to 1.2 mm, preferably in the range from 0.1 to 0.75 mm and even more preferably in the range from 0.15 to 0.25 mm; the 75% quantile of the values that have been determined the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
     is less than 4100 μm/mm, preferably less than 3900 μm/mm, more preferably less than 3700 μm/mm, even more preferably less than 3500 μm/mm, even more preferably less than 3300 μm/mm, even more preferably less than 3100 μm/mm, even more preferably less than 2900 μm/mm, even more preferably less than 2500 μm/mm and even more preferably less than 2000 μm/mm; s 2   max /s 1 ×(s 2   max /s 2   min −1) is less than 1.1, preferably less than 0.8 and even more preferably less than 0.5. 
     Glass 
     The glass of the container may be any type of glass and may consist of any material or combination of materials which the skilled person deems suitable in the context of the invention. Preferably, the glass is suitable for pharmaceutical packaging. Particularly preferable, the glass is of type I, more preferably type I b, in accordance with the definitions of glass types in section 3.2.1 of the European Pharmacopoeia, 7 th  edition from 2011. Additionally, or alternatively preferable to the preceding, the glass is selected from the group consisting of a borosilicate glass, an aluminosilicate glass, soda lime glass and fused silica; or a combination of at least two thereof. For the use in this document, an aluminosilicate glass is a glass which has a content of Al 2 O 3  of more than 8 wt.-%, preferably more than 9 wt.-%, particularly preferable in a range from 9 to 20 wt.-%, in each case based on the total weight of the glass. A preferred aluminosilicate glass has a content of B 2 O 3  of less than 8 wt.-%, preferably at maximum 7 wt.-%, particularly preferably in a range from 0 to 7 wt.-%, in each case based on the total weight of the glass. For the use in this document, a borosilicate glass  is a glass which has a content of B 2 O 3  of at least 1 wt.-%, preferably at least 2 wt.-%, more preferably at least 3 wt.-%, more preferably at least 4 wt.-%, even more preferably at least 5 wt.-%, particularly preferable in a range from 5 to 15 wt.-%, in each case based on the total weight of the glass. A preferred borosilicate glass has a content of Al 2 O 3  of less than 7.5 wt.-%, preferably less than 6.5 wt.-%, particularly preferably in a range from 0 to 5.5 wt.-%, in each case based on the total weight of the glass. In a further aspect, the borosilicate glass has a content of Al 2 O 3  in a range from 3 to 7.5 wt.-%, preferably in a range from 4 to 6 wt.-%, in each case based on the total weight of the glass. 
     A glass which is further preferred according to the invention is essentially free from B. Therein, the phrase “essentially free from B” refers to glasses which are free from B which has been added to the glass composition by purpose. This means that B may still be present as an impurity, but preferably at a proportion of not more than 0.1 wt.-%, more preferably not more than 0.05 wt.-%, in each case based on the weight of the glass. 
     Measurement Methods 
     The following measurement methods are to be used in the context of the invention. Unless otherwise specified, the measurements have to be carried out at an ambient temperature of 23° C., an ambient air pressure of 100 kPa (0.986 atm) and a relative atmospheric humidity of 50%. 
     Determination of Individual ĥ-Values 
     The distance between the outer surface of the circular glass bottom and the ground is determined by means of non-contact profilometer (cyberSCAN CT 300; cyberTECHNOLOGIES, Eching-Dietersheim, Germany) and a chromatic sensor (Precitec CHRocodile S 3000) using the ASCAN software. As shown in  FIG. 4 , for the determination of the individual values for ĥ, for any given circle the centre of which corresponds to the centre of the glass bottom the distance h between contact plane representing the ground and the outer surface of the circular glass bottom is determined in regularly steps of 5° (i. e. 72 measuring points per circle), serving as data points for an azimuthal average. For a more precise measurement, the 72 single measuring points are defined as the moving average of additional measuring points (i. e. five additional measuring points are  averaged to obtain a single measuring point) along the same circle. The first circle is a circle having a diameter of 500 μm and the radius increases for the following circles stepwise by 500 μm (which means that the radius of the second circle is 1,000 μm, the radius of the third circle is 1,500 μm and so on). 
     Fitting the curvature function ĥ (x) with the individual ĥ-values 
     In order to characterize the mean curvature of the glass bottom, the height function (I) 
     
       
         
           
             
               
                 
                   
                     
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     is fitted to at least four nodes H i (x i ) of the radial height profile using a common least square fitting, implemented in standard mathematical software packages, e.g. the “curve_fit” function of the open source scipy.optimize package:
 
https://docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.curve_fit.html
 
     For the fit the variable parameters are c and h 0  are used. These variables are varied to obtain the minimum of 
     
       
         
           
             
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     wherein standard deviation error (or fitting error) for constant c is referred to as “Δc”. The standard deviation error is defined as Δc=√{square root over (σ 2 )} (σ 2  being the variance). 
     The curvature c directly affects imaging through the glass bottom. The offset height h 0  depends on the reference system. In the case of referencing to the standing area, the offset height h 0 ≈t (but only in rare cases equal).  
     Determination of the slope at position x,y and of the h(x,y) max - and h(x,y) min  value 
     The two-dimensional distance between the outer surface of the circular glass bottom and the ground is again determined by means of a non-contact profilometer (cyberSCAN CT 300; cyberTECHNOLOGIES, Eching-Dietersheim, Germany) and a chromatic sensor (Precitec CHRocodile S 3000). For the determination of the h(x,y)-values, the glass bottom is divided into an array of square parts 112 having an edge length of 200 μm as shown in  FIG. 6A . At the centre of each of these square parts 112 the distance between the outer surface 106 of the glass bottom 104 and the ground is determined for individual measurement points 112 that are located in the centre of the square parts 112 as shown in  FIG. 6A . From the thus obtained values h(x,y) only those values are selected that have been obtained for measurement points 135 that are located within a circle having a radius of 0.4×d 2 /2 (or a radius of 0.6×d 2 /2 or 0.8×d 2 /2) as shown in  FIG. 6A . 
     From the thus obtained h(x,y)-values the slope-values are calculated using an appropriate mathematical software, for example the “Slope Analysis” function of the Mx software version 8.0.0.3 (Zygo, part of AMETEK, Inc.). The slope magnitude can be calculated as slope magnitude=√{square root over ((dh/dx) 2 +(dh/dy) 2 )}. 
     For this calculation with the Mx software a slope lateral resolution as well as integration length of the edge length of the square parts 112 can be used, here 200 μm. The h(x,y) max -value corresponds to the highest h(x,y)-value and the h(x,y) min -value corresponds to the lowest h(x,y)-value that have been determined within the circle having a radius of 0.4×d 2 /2 (or a radius of 0.6×d 2 /2 or 0.8×d 2 /2). 
     Determination of Wavefront Distortion 
     A polar coordinate system is used to fit a continuous wavefront W( , φ) to the measured nodes W i . The wavefront is defined on the unit circle, thus ρ=1 corresponds to 
     
       
         
           
             r 
             = 
             
               
                 
                   
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                 2 
               
               = 
               
                 A 
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                 2 
               
             
           
         
       
     
      With 2W&lt;A&lt;(2W+2 mm) and A being the measurement diameter of the Shack-Hartmann sensor. This continuous wavefront can again be expressed in Zernike terms by a superposition of Zernike polynomials (described by Thibos et al.: “ Standards for Reporting the Optical Aberrations of Eyes ”; Journal of Refractive Surgery; Vol. 18 (2002); pages S652-S660) as W( ,φ)=Σa i Z i . 
     Here the coefficients a have been computed with the inner product 
       a i =∫∫Z i W( ,φ)d dφ,
 
     where   has been integrated from 0 to 1 and φ from 0 to 2 p. We define the corrected wavefront distortion W( ,φ) corrected   
         W ( ,φ) corrected = W ( ,φ)− a   0   Z   0   −a   1   Z   1   −a   2   Z   2   −a   4   Z   4 
 
     as the wavefront with piston (Z 0 ), tilt (Z 1 , Z 2 ) and defocus (Z 4 ) subtracted. The OSA/ANSI indexing conventions as described in Thibos et al. are used. A setup to measure the wavefront distortion W( ,φ) is shown in  FIG. 10 . 
     Determination of s 2   max  and s 2   min    
     The measurement of the thickness of the circular glass bottom was performed using a CHRocodile M4 high resolution measuring head (Precitec GmbH &amp; Co. KG, Lemgo, Germany) with a measuring range of 200-3000 μm and a resolution of 0.1 μm. A step width of 0.1 mm was selected laterally. 
     Wall Thicknesses and Diameters 
     The wall thickness s 1  of the glass container at a given position as well as the outer diameter (d 1 ) of the glass container at a given position are determined in accordance with DIN ISO 8362-1:2016-06. The inner diameter (d 2 ) can be calculated from s 1  and d 1 .  
     EXAMPLE 
     A glass tube (Fiolax® clear, Schott AG, Germany) having an outer diameter d 1  of 30 mm and a wall thickness s 1  of 1.1 mm is loaded into the head of a rotary machine. While rotating around its major axis the glass tube is heated to its softening point with two separation gas burners as shown in  FIG. 8  and the heated glass is pulled along its major axis by moving downwards the lower clamping chucks for stretching and creating a container closure in the form of a circular glass bottom. When moving downwards the lower clamping chucks, the separation gas burners are moved in the same direction as the lower clamping chucks. The ratio of the distance with which the separation gas burners have been moved downwards to the distance with which the lower clamping chucks have been moved downwards (|Y′ stop −Y′ 0 |/|Y stop −Y 0 |; see  FIG. 9 ) was 0.72. 
     Furthermore, the burner was moved downwards with a time offset (Δt) of 0.085 sec. In a Comparative Example representing the prior-art process the burner remains at a fixed position when the lower clamping chucks are moved downwards. The glass containers prepared as described above are characterized by a volume of 20 ml. 
     
       
         
           
               
               
               
             
               
                   
               
               
                   
                 Inventive Example 
                 Comparative Example 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Δc/c 
                 0.034 
                 0.27 
               
            
           
           
               
               
               
               
               
            
               
                 peak to valley difference 
                 31  
                 waves 
                 148  
                 waves 
               
            
           
           
               
               
               
            
               
                 (W(    , φ) corrected ) max  − (W(    , φ) corrected ) min   
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 75% quantile for the term 
                 3300  
                 μm/mm 
                 4130  
                 μm/mm 
               
            
           
           
               
               
               
            
               
                 {square root over ((dh/dx) 2  + (dh/dy) 2 )} × d1/h(x, y) delta   
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 s2 max   
                 1.36  
                 mm 
                 1.55  
                 mm 
               
               
                 s2 min   
                 1.27  
                 mm 
                 0.87  
                 mm 
               
            
           
           
               
               
               
            
               
                 s2 max /s1 × (s2 max /s2 min  − 1) 
                 0.088 
                 1.101 
               
               
                 optical inspection capability 
                 see FIG. 11C 
                 see FIG. 11C 
               
               
                   
                 on the right 
                 on the left 
               
               
                   
               
            
           
         
       
     
     As can be seen, adjusting the outer contour of the circular glass bottom in order to ensure that the 75% quantile of the values for the term 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}×d1/h(x,y) delta  
 
      for all given positions x,y within a circular area having a radius of 0.4×d 2 /2 is less than 4100 μm/mm significantly improves the optical inspection capability of the glass container. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a cross-sectional view of a glass container according to the invention, wherein for the purpose of an improved illustration the parts of the glass container (i. e. glass tube  101 , glass bottom  104  and curved glass heel  107 ) have been separated from each other; 
         FIG. 2  shows a cross-sectional view of a glass container  100  according to the invention in which the individual container parts shown in  FIG. 1  (i. e. glass tube  101 , glass bottom  104  and curved glass heel  105 ) are arranged in the usual way; 
         FIGS. 3A-C  show a cross-sectional view of the bottom area of a glass container  100  according to the invention and illustrate the different areas in which individual values for ĥ or ĥ(x) can be determined; 
         FIGS. 4A-4B  show the arrangement of concentrical circles  111  along which the individual values for ĥ are determined ( FIG. 4A ) and the way in which the azimuthal average for ĥ is obtained for a given circle  111  ( FIG. 4B ); 
         FIG. 5  shows a graph of the individual values for ĥ that have been determined for a given circular glass bottom  104  and the fitted function ĥ (x) (dashed line); 
         FIGS. 6A-B  show the experimental setup that has been used to determine the two-dimensional distance h(x,y) and the slope magnitude of the outer surface of the glass bottom at a given position x,y; 
         FIGS. 7A-B  show in a side view the localization of plane  113  that is used to determine s 2   max  and s 2   min  in the circular glass bottom  104  of the glass container  100  ( FIG. 7A ) and the localization of s 2   max  and s 2   min  as well as the width of the area within which these values are to be determined in an exemplary bottom cross-section ( FIG. 7B );  
         FIGS. 8A-8D  show the process for the preparation of a glass container  100  according to the present invention; 
         FIG. 9  shows the movement of the separation gas burners  120  and the lower clamping chucks  119  at the time at which the lower clamping chucks  119  are moved downwards; 
         FIG. 10  shows the experimental set up for the characterization of wavefront distortions caused by the outer contour of the circular glass bottom  104 ; 
         FIGS. 11A-C  show the simulation results for the passage of an image through a distorted glass bottom  104 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a cross-sectional view of a glass container according to the invention, wherein for the purpose of an improved illustration the parts of the glass container (i. e. glass tube  101 , glass bottom  104  and curved glass heel  107 ) have been separated from each other. The glass container  100  comprises a glass tube  101  with a first end  102  and a further end  103 , the glass tube  101  having an outer diameter d 1 , an inner diameter d 2  and a wall thickness s 1 . The glass tube  101  is further characterized by a longitudinal axis L tube  that passes through the centre of the first end  102  and the further end  103 . The glass tube further comprises a circular glass bottom  104 , wherein the circular glass bottom  104  closes the glass tube  101  at the first end  102 , wherein the circular glass bottom  104  comprises an inner surface  105  directed to the inside of the glass container  100 , an outer surface  106  directed to the outside of the glass container  100  and a centre  110 . The glass container further comprises a curved glass heel  107  extending from an outer end  108  of the circular glass bottom  104  to the first end  102  of the glass tube  101 . As can also be seen in  FIG. 1 , the glass bottom is preferably characterized by a bottom indentation t which usually takes on the maximum value in the centre  110  of the circular glass bottom  104 .  FIG. 2  shows a glass container  100  in which the individual container parts shown in  FIG. 1  (i. e. glass tube  101 , glass bottom  104  and curved glass heel  107 ) are arranged in the usual way.  
       FIG. 3A, 3B and 3C  show a cross-sectional view of the bottom area of a glass container  100  according to the invention and illustrate the different areas (x±0.4×d 2 /2 in  FIG. 3A , x±0.6×d 2 /2 in  FIG. 3B  and x±0.8×d 2 /2 in  FIG. 3C ) in which the distance h between a contact plane  109  and the outer surface  106  of the circular glass bottom  104  at a given position x, with x=0 in the centre  110  of the circular glass bottom  104 , is determined. The individual values of h can be applied to determine ĥ and ĥ(x). 
       FIG. 4A  shows the arrangement of concentrical circles  111  along which the individual values for ĥ are determined. As shown in  FIG. 4B , for the determination of the individual values for ĥ, for any given circle the distance h between contact plane  109  representing the ground on which the glass container  100  rests and the outer surface  106  of the circular glass bottom  104  is determined in regularly steps of 5° (i. e. 72 measuring points per circle; for the sake of clarity only 5 steps are shown in  FIG. 4B ), serving as data points for an azimuthal average. The first circle  111  is a circle having a diameter of 500 μm and the radius increases for the following circles stepwise by 500 μm (which means that the radius of the second circle is 1,000 μm, the radius of the third circle is 1,500 μm and so on). 
     From the thus obtained values for h the azimuthal average corresponds to the individual value ĥ that has been determined for any given circle  111 .  FIG. 5  shows a graph of the individual values for ĥ that have been determined for a given circular glass bottom  104  and the fitted function ĥ(x) (see the dashed line). The fitted function is represented by formula (I) 
     
       
         
           
             
               
                 
                   
                     
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                           × 
                           
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                             2 
                           
                         
                         
                           1 
                           + 
                           
                             
                               1 
                               - 
                               
                                 
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     in which c and h 0  serve as individual fitting parameters. The above function is the curvature function of a sphere having the radius R with c=1/R. Values for c (and also for the standard deviation error (Δc) indicating how exactly the determined individual values of ĥ can be reproduced using the curvature function given above) are determined using an appropriate mathematical software (ASCAN-Software) as described in the “Test method”-section above.  
       FIGS. 6A and 6B  show the experimental setup that has been used to determine the two-dimensional distance h(x,y) and the slope magnitude 
       √{square root over ((dh/dx) 2 +(dh/dy) 2 )}
 
     of the outer surface  106  of the glass bottom  104  at a given position x,y. The distance h(x,y) between the outer surface  106  of the circular glass bottom  104  and the ground at a given position x,y is determined by means of a non-contact profilometer. For the determination of the individual values of the two-dimensional distance h(x,y), the glass bottom  104  is divided into an array of square parts  112  having an edge length of 200 μm. At the centre of each of these square parts  112  the distance between the outer surface  106  of the glass bottom  104  and the ground is determined at measurement point  135  as shown in  FIG. 6A  (the individual measurement points  135  are evaluated in an order following the arrows shown in  FIG. 6A ) and addressed to the corresponding x and y values of the respective square and stored as an individual value of h(x,y). From the thus obtained values for the two-dimensional distance h(x,y) only those values are selected for calculating the slope magnitude and for determining h(x) max  and h(x) min  that have been obtained for measurement points  135  that are located within a circular area  136  having a radius of 0.4×d 2 /2 (or within a circular area  137  having a radius of 0.6×d 2 /2 or within a circular area  138  having 0.8×d 2 /2) as shown in  FIG. 6A . 
     From the thus obtained h(x,y)-values the slope magnitude representing the slope of between measurement points for different x and y, preferably between neighboring measurement points, is calculated using an appropriate mathematical software, for example the “Slope Analysis” function of the Mx software. 
     The h(x,y) max -value corresponds to the highest h(x,y)-value and the h(x,y) min -value corresponds to the lowest h(x,y)-value that have been determined within the circular area  136  having a radius of 0.4×d 2 /2 (or within the circular area  137  having a radius of 0.6×d 2 /2 or within the circular area  138  having a radius of 0.8×d 2 /2). 
       FIG. 7A  shows in a side view the localization of plane  113  that is used to determine s 2   max  and s 2   min  in the bottom  104  of the glass container  100 . Plane  113  corresponds to the plane that is centrically located in the glass container  100  and that comprises the longitudinal axis L tube  of the  glass container  100  (indicated by the dashed line in  FIG. 7A ), i. e. the axis that goes perpendicular through the centre  110  of the bottom  104  (see  FIG. 7B ).  FIG. 7B  shows the localization of s 2   max  and s 2   min  as well as the width of the area within which these values are to be determined in an exemplary bottom cross-section. As can be seen, s 2   max  and s 2   min  are determined within an area that extends over about 65% of the area of the circular glass bottom, wherein the centre of this area is located in the centre  110  of the circular glass bottom  104 . 
       FIGS. 8A-D  show the process for the preparation of a glass container  100  that displays a glass bottom as define herein. In a first process step I) the glass tube  101  having an upper portion  116  with an upper end  117  and a lower portion  114  with a lower end  115  is held by means of upper and lower clamping chucks  118 , 119  in a vertical position. The glass tube  101  is heated at a defined position between the lower and the upper portion  114 , 116  by means of two opposed separation gas burners  120  to a temperature above the glass transition temperature while the glass tube  101  is rotating around its longitudinal axis L tube  (see  FIG. 8A ). In process step II) the lower portion  114  of the glass tube  101  is pulled downwards by moving downwards the lower clamping chucks  119  while the glass tube  101  is rotating around its longitudinal axis L tube  (see  FIG. 8B ). When moving downwards the lower clamping chucks  119  and thus also the lower portion  114  of the glass tube  101 , a glass thread  121  is formed (see also  FIG. 8B ). When further moving downwards the lower portion  114 , this portion is separated from the upper portion  116  by pulling apart the glass thread  121 , the part of the mass of the glass thread  121  that remains at the lower portion  114  of the glass tube  101  forming a circular bottom  104  (see  FIGS. 8C and 8D ). The process for the preparation of a glass container according to the present invention is characterized in that, while pulling downwards the lower portion  114 , the at least one separation gas burner  120  does not remain at the same position as it is observed in the process known from the prior art, but is moved downwards in a direction that is substantially parallel to the direction in which the lower clamping chucks  119  are moved downwards (indicated by the arrows beneath the separation gas burners  120  in  FIG. 8A ), the at least one separation gas burner  120  thereby following the upper end  122  of the lower portion  114 . 
       FIG. 9  shows the movement of the separation gas burners  120  and the lower clamping chucks  119  at the time at which the lower clamping chucks  119  are moved downwards. In the embodiment of the process shown in  FIG. 9 , the lower clamping chucks  119  are moved  downwards at a point of time t and the at least one separation gas burner  120  is moved downwards at a point of time t′=t+Δt, wherein Δt can be zero (which means that the lower clamping chucks  119  and the at least one separation gas burner  120  are moved downwards simultaneously) or Δt can be larger than zero. In this case the at least one separation gas burner  120  is moved downwards with a time delay in relation to the lower clamping chucks  119 . As can also be seen in the embodiment of the process shown in  FIG. 9 , the at least one separation gas burner  120  is moved downwards starting from a position Y′ 0  to a position Y′ stop  and the lower clamping chucks  119  start from a position Y 0  and, preferably after the at least one separation gas burner  120  has stopped at position Y′ stop , to stop at a position Y stop , wherein |Y′ stop −Y′ 0 |&lt;|Y stop −Y 0 |. According to this embodiment it is thus preferred that the distance with which the at least one separation gas burner  120  is moved downwards is smaller than the distance with which the lower clamping chucks  119  are moved downward. 
       FIG. 10  shows the experimental setup to characterize wavefront distortions caused by the outer shape of the glass bottom  104  of a glass container  100  (which in  FIG. 10  is a vial), independent of the imaging system eventually used for the inspection. A collimated laser beam  130  of 1/e 2  diameter (2W=3 mm) and wavelength of 520 nm from a laser source  132  (e.g. Thorlabs PL201, in order to cover 70% of d 2  for vial with d 2 =13 mm it has been extended to 2W=9 mm with the Beamexpander Thorlabs GBE01-A) is directed towards the glass bottom  104  of a vial  100  standing on a transparent support  128 . Since the inspection is usually carried out with a filled vial  100 , the vial  100  is filled with water  127  up to a height that completely covers the inner surface  105  of the glass bottom  104 . Practically this can be achieved with a fill height of 10 mm. The effect of the inner surface  105  of the glass bottom  104  on the optical imaging can be neglected since n vial −n filling ≈0.01&lt;n vial −n air ≈0.5, thus the inner surface  105  of the glass bottom  104  has a much smaller effect on the wavefront. However, in this measurement it is intended to completely eliminate the influence of the inner surface  105  of the glass bottom  104  and for that purpose an index-matching liquid of n=n vial  is selected. One crucial factor of the measurement is the inner neck diameter d 4  of the vial  100 . In order to characterize the wavefront distortion for a laser diameter that is larger diameter than d 4 , the top region of the vial  100  is removed along a cutting plane  126 . Thus, if no further imaging optic (e. g. another beam expander used in reverse) is used, the measurement aperture  124  of the Shack-Hartmann sensor  123  determines the diameter of the  wavefront measurement. For the experimental set up used herein a Shack-Hartmann sensor  123  with a large aperture  124  of 11.26mm×11.26 mm has been used (WFS40-7AR, Thorlabs Inc.). Thus, in this setup it would be necessary to shrink the beam size with another beam expander, if vials with d 2  larger than 13 mm are investigated. 
     The Shack-Hartmann sensor  123  contains an array micro-lenses  133  that images a characteristic dot pattern onto a CCD. For a planar wavefront  129 , the dot pattern has the same spacing as the spacing of the micro-lens array. However, if the wavefront is aberrated when passing through the glass bottom to obtain the aberrated wavefront  125 , any aberrations locally displace the dot laterally in the direction of the distortion (as shown in  FIG. 3  of the publication “History and Principles of Shack-Hartmann Wavefront Sensing”; Ben C. Platt and Roland Shack; Journal of Refractive Surgery; Vol. 17 (2001), pages S573-S577). This way, the distortion can be mapped onto the nodes W i  the micro-lens array the Shack-Hartmann-Sensor  123  provides. 
       FIGS. 11  A-C show the simulation results for the passage of an image through a distorted glass bottom  104 . The form of the glass bottom  104  follows real measurements, which were obtained by measuring and averaging the height at several 500 μm spaced rings and fitting a spline function through all radial nodes ( FIG. 11B , wherein the figure on the left represents the outer contour of a state-of-the-art glass bottom  104  and the figure on the right represents the outer contour of a glass bottom  104  in a glass container according to the present invention). An ideal objective of NA 0.5 is assumed for the vial  100  (filled with 20 mm of water). The effect of the inner surface  105  of the vial bottom  104  has been neglected. While the optical power caused by the curvature of the vial bottom can be easily corrected by shifting the image plane (so called defocus correction), higher order aberrations cannot: The state-of-the-art glass bottom  104  significantly distorts the image and even after defocus correction, the image at the image plane  134  remains blurred due to spherical aberrations (see the figure on the left of  FIG. 11C ). The glass bottom  104  in the glass container  104  according to the present invention is less flat, but with significant lower radial variation. The image itself after defocus correction is only slightly perturbed (see  FIG. 11C  on the right) and is suitable for analysis, e.g. particle detection.  
     LIST OF REFERENCE NUMERALS 
       100  glass container 
       101  glass tube 
       102  first end of the glass tube  101   
       103  second end of the glass tube  101   
       104  circular glass bottom 
       105  inner surface of the circular glass bottom  104   
       106  outer surface of the circular glass bottom  104   
       107  curved glass heel 
       108  outer end of the circular glass bottom 
       109  contact plane representing the ground 
       110  centre of the glass bottom  104  or the circle  111   
       111  Circle 
       112  square in the centre of which h(x,y) is determined 
       113  cut surface 
       114  first or lower portion of the glass tube  101   
       115  first or lower end of the first or lower portion  114   
       116  second or upper portion of the glass tube  101   
       117  second or upper end of the second or upper portion  116   
       118  first or upper clamping chucks 
       119  second or lower clamping chucks 
       120  separation gas burner 
       121  glass thread 
       122  upper end of portion  114 , 116 , preferably of lower portion  114   
       123  Shark-Hartmann-sensor 
       124  aperture for measuring range of the Shark-Hartmann-sensor  123   
       125  wavefront aberrated by the circular glass bottom  104   
       126  cutting plane if top region has to be removed for measurement 
       127  H 2 O (filling height: 10 mm) 
       128  transparent support 
       129  undisturbed wavefront  
       130  collimated laser beam (width: 1/e 2  at 2W) 
       131  laser source (520 nm) 
       132  plane of object 
       133  lens (NA 0.5) 
       134  plane of image 
       135  measurement point 
       136  circular area having a radius of 0.4×d 2 /2 
       137  circular area having a radius of 0.6×d 2 /2 
       138  circular area having a radius of 0.8×d 2 /2