fig1 shows an inspection apparatus 10 for inspecting a cigarette formation 11 comprising cigarettes 12 arranged in three layers . the inspection apparatus 10 has two light sources 13 and 14 , which each preferably comprise a laser but may also comprise another bright light source , for example an arrangement of bright light - emitting diodes . the emitted light is therefore monochromatic and coherent or monochromatic and non - coherent or non - monochromatic and non - coherent . the light sources 13 , 14 are either turned on permanently , or , alternatively , may be operated in a pulsed fashion , so that they generate short flashes of light . the light beams 15 , 16 issuing from the light sources 13 , 14 each pass to an optical arrangement or to a lens - diaphragm system 17 , 18 or to a hologram , which convert the light beams 15 , 16 in each case in three light bands 19 , 20 , 21 and 22 , 23 , 24 . these light bands 19 to 24 fall onto cigarette heads 25 of the cigarettes 12 , where the light bands 19 to 24 have the configuration of strip - like portions 26 to 31 , as illustrated in fig2 . fig2 shows the end areas of the cigarette heads 25 from fig1 . the cigarette formation 11 comprises three layers , the outer two layers comprising seven cigarettes and the middle layer comprising six cigarettes . for each layer , two strip - like portions 26 and 27 , and 28 and 29 , and 30 and 31 impinge on the end areas . the respective upper strip - like portions 26 , 28 , 30 originate from the light source 13 illustrated at the top of fig1 . the lower strip - like portions 27 , 29 , 31 correspondingly originate from the lower light source 14 . each strip - like portion 26 to 31 covers a wide region of the end area of the respective cigarette heads 25 , to be precise in each case somewhat less than half of the end area of a cigarette head . therefore , essentially total coverage of the cigarette end area is obtained by two strip - like portions . this has the advantage that it is thereby possible to evaluate virtually the entire end area . fig1 shows a detector 32 , which receives light 33 reflected from the end areas . the detector 32 has an optical arrangement 34 , which serves for focusing the reflected light 33 onto a sensor . this sensor contained in the detector 32 as a ccd chip having a multiplicity of two - dimensionally arranged ccd elements . as a result , it is possible to generate the images of the strip - shaped portions 26 to 31 on the end areas of the cigarette heads on the ccd chip . the individual ccd elements each output a signal which flows to an evaluation device . the inspection apparatus 10 that is described is preferably situated on the cigarette turret of a cigarette packaging machine . however , it may also be arranged in a similar form on the cigarette magazine and there perform presorting or ejection of individual cigarettes by means of an ejector arranged on the magazine , as is described in the published german patent application de 36 20 735 a1 . in the case of an inspection apparatus arranged on the cigarette turret , the identification of a defective cigarette leads to the entire cigarette formation 11 being ejected . for this purpose , the inspection apparatus generates an error signal which causes the ejector to perform ejection . fig3 shows a section along the line iii — iii from fig2 that is to say a longitudinal section through a cigarette head 25 . this cigarette head 25 has a filter piece 35 set back relative to the end of the tip sleeve 36 . the incident light bands 20 , 23 irradiate the strip - shaped portions 28 , 30 at the end of the filter piece 35 . in addition , the light bands 20 , 23 also irradiate the end of the tip sleeve 36 at end portions 37 , 38 . these portions 28 , 29 , 37 , 38 illustrate the illuminated portions in the case of a recessed filter cigarette . a similar picture would be produced for a papyrossi cigarette , the filter piece 35 in that case being replaced by tobacco , however . the broken lines illustrated in fig3 show the conditions for an excessively long cigarette 12 . in the case of such a defective cigarette , the end area 39 of the filter piece 35 would end offset to the right , as would the end edge of the tip sleeve 40 . in the case of a properly formed cigarette , the portions 28 and 29 are at a specific distance from one another , as are the portions 37 , 38 or the distances between the portions 28 and 37 or 38 and also 29 and 38 or 37 . defects of the cigarette heads can be inferred from these distances . specifically , as shown in fig3 these portions 28 , 29 , 37 , 38 are displaced away from the formation if a cigarette is too long . thus , the portion 28 is displaced to the broken line 28 ′ shown , and 29 is displaced to the broken line 29 ′ shown , and the end portions 37 and 38 are also displaced to broken lines 37 ′ and 38 ′, respectively . fig4 a shows a longitudinal section through a cigarette head 41 of a tobaccoless cigarette with an end area 42 . fig4 b shows the image produced on the detector 32 when the end area 42 is illuminated by two light bands which impinge as strip - like portions on the end area 42 . two images 43 , 44 of strip - like portions , which illuminate a multiplicity of pixels 45 illustrated as dots , impinge on the end area 42 . the doubly traced circular line 6 is an imaginary representation of the cigarette paper 47 surrounding the cigarette head 41 . the images 43 , 44 have a central portion 48 and 49 , respectively , which corresponds to the tobacco - side end area regions illuminated by the respective strip - like portions . these central portions 48 , 49 are bounded by in each case two point - like end portions 50 to 53 . these point - like end portions 50 to 53 correspond to bright light spots at the locations at which the strips of light impinge on the filter paper . fig4 c shows the image generated or calculated by an evaluation device . this image need not necessarily be displayed . it is sufficient for the data on which this image is based to be calculated in order to implement the invention . a respective centroid line 54 , 55 is determined from the central portions 48 , 49 . the centroid lines 54 , 55 are advantageously calculated in such a way that they lie parallel to one another . in addition , the end portions 50 to 53 are each combined to form a centroid 56 to 59 . fig5 a shows a cigarette which is too short by comparison with the cigarette illustrated in fig4 a . the cigarette illustrated in fig5 a is shorter by the distance a than the cigarette illustrated in fig4 a . as a result of this , the central portions 48 , 49 illustrated in fig5 b are closer together than those illustrated in fig4 b . the same applies to the end portions 50 to 53 . this is a consequence of the light bands which run toward one another with increasing distance and lead to the portions being moved closer together . the same applies correspondingly to the centroid lines 54 , 55 and centroids 56 to 59 illustrated in fig5 c . this displacement results in a shorter distance c in fig5 c than a corresponding larger portion b in fig4 c . fig6 a again shows the cigarette head 41 of a filterless cigarette , in which , however , some of the tobacco filling is missing . this leads to a hole 60 . therefore , in the image 43 of an upper strip of light on the detector , which image encompasses an upper portion of the end of the cigarette head 41 , an irregularity is discernible in the upper central portion 48 in fig6 b . this is because the central section 48 of the image 43 is not oriented essentially horizontally but rather slopes away to the side . fig6 c shows the centroid lines 54 , 55 calculated from this . the centroid line 54 illustrated in fig6 c is displaced toward the center of the cigarette by comparison with the centroid line 54 illustrated in fig4 c . this is a consequence of the hole 60 . since the lower image 44 in fig6 b corresponds to that illustrated in fig4 b , the centroid line 55 in fig6 c is at the same position as in fig4 c . the distance between the centroid lines 54 , 55 now no longer corresponds to the desired distance b in accordance with fig4 c , but rather is smaller than said desired distance . a defective cigarette can be inferred from this . a further special feature of the illustrations in accordance with fig6 b and 6 c emerges from the fact that the intrinsically slanted portion 48 is converted into a straight centroid line 54 . this orientation — compelled computationally — of the centroid lines serves for determining the distance between the centroid lines 54 and 55 more simply . fig7 a shows the cigarette head 61 of a recessed filter cigarette with a filter piece 62 and a hollow tip 63 . the strips of light which impinge as strip - like portions on the cigarette head 61 are represented as images 64 , 65 on the detector 32 in accordance with fig7 b . in the case of such a correctly formed cigarette , central portions 66 , 67 are situated in a manner displaced toward the cigarette axis . the end portions 50 to 53 , by contrast , are located at the same position as in fig5 b for a completely filled cigarette . fig7 c shows calculated centroid lines 68 , 69 , which , in the case of a proper recessed filter cigarette , are at a distance which is less than the distance c illustrated in fig4 c . in addition , the centroids 56 to 59 in fig7 c are situated at a horizontal position that differs from that of the centroid lines 68 , 69 . this is due to the fact that the light bands or strip - shaped portions which impinge on the cigarette head 61 are displaced toward the cigarette axis , since these portions are set back in the axial direction , that is to say are at a greater distance from the inspection apparatus . fig8 a once again shows a cigarette head 61 of a recessed filter cigarette , in which case , however , the filter 62 is formed defectively since it has been obliquely clipped . as a result , the central portions 66 , 67 of the images 64 , 65 are situated at a different position in fig8 b compared with fig7 b . however , the end portions 50 to 53 of the images 64 , 65 are situated at the same position as in fig7 b . fig8 c shows the centroid lines 68 , 69 produced from the images in accordance with fig8 b , and also the centroids 56 to 59 . the centroids 56 to 59 are not displaced relative to fig7 c , whereas the centroid lines 68 and 69 in fig8 b are displaced upward compared with fig7 c . in addition , they are at a smaller distance from one another . the differentiation between centroid lines 54 , 55 to 68 , 69 and centroids 56 to 59 makes it possible to ascertain one or four reference points on the edge of the cigarette casing or tip sleeve . as a result , it is possible to make statements about set - back filters or holes in the tobacco even in a quantitative manner , that is to say that statements can be made about distances between the end edge of a cigarette and possible holes or the depth of a tip sleeve in the case of recessed filter cigarettes or papyrossi cigarettes . by way of example , it is possible to verify by measurement whether a tip sleeve having a setpoint depth of 5 mm lies within tolerance limits of ± 1 mm . the inspection method described and also the inspection apparatus described allow a very high measurement accuracy . furthermore , a snapshot of a cigarette head or of the cigarette heads of a cigarette formation suffices for inspecting the length of a cigarette , the depth of a tip sleeve , the form of a cigarette head and also the filling with tobacco or filter . as a result , a cigarette head can be measured in one motion . as a result — unlike in other known inspection methods in which , by way of example , a plunger is pressed onto a cigarette head — this contactless method enables a cigarette packaging or production machine to be operated at high speed . the invention therefore opens up a host of possibilities for the inspection of cigarette heads .
the invention relates to a method for inspecting cigarette heads , where light radiates in at least two strip - like portions , which are incident from different directions , onto the end area of a cigarette head and light reflected from the end area is received by a detector and evaluated . known methods of this type have the disadvantage that they are inaccurate and do not allow exact statements to be made about the state of cigarettes . therefore , the invention is based on the problem of improving the inspection of cigarettes . this problem is solved by virtue of the fact that , in the course of evaluation , a distance between two lines which are produced from a signal generated by the detector and correspond to the strip - shaped portions is determined in order to establish the position of that region of the cigarette head which is irradiated by the portions . furthermore , the invention relates to a corresponding apparatus .