CH715155A1 - Method and device for the optical inspection of preforms. - Google Patents

Abstract

The present invention relates to a method for the optical inspection of preforms and a corresponding device, in which method a preform (20) is conveyed by means of a transport device (30), an image of a side wall surface of the preform (20) by means of a camera device (40a). is produced. The preform (20) is rotated by means of a rotating device (31, 33) about an axis perpendicular to the conveying direction and over an imaging length (L) of the conveying direction. The camera device (40a) is configured such that it can produce an image of the side end wall surface of the preform (20) over the entire image length (L).

Description

description

Technical Field This invention relates to a method and an apparatus for testing workpieces, in particular preforms. In particular, this invention relates to a method and a device for testing preforms, in which a preform is conveyed by means of a transport device, the preforms being rotated about an axis perpendicular to the conveying direction and over an imaging length of the conveying direction, and in which the side wall surface is used by means of a camera device the preforms are mapped over the entire length of the image.

PRIOR ART [0002] The so-called non-destructive workpiece inspection or control now plays an extremely important role in quality assurance in industrial production. In particular, the non-destructive workpiece inspection of preforms has some important advantages over a conventional sample inspection. On the one hand, this non-destructive inspection enables a check of every single preform, i.e. a 100% inspection. In addition, all of the preforms tested retain their overall functionality and thus their use value. These non-destructive testing methods are often used in production to initiate a process correction if necessary and thus ensure consistent quality.

Liquids, especially beverages, are increasingly being traded in plastic bottles and sold to the end user. For hygienic, logistical and cost reasons, disposable bottles are increasingly used. Corresponding plastic containers are required and used in large quantities.

In order to further reduce the transport effort, it has now become established that a “two-stage” production process is used for single-use plastic bottles, in which the two manufacturing stages are generally implemented at different locations. Preforms are usually manufactured in a first company, which is independent of the actual beverage-filling company, and which usually also supplies several companies. The preforms produced by this are still brought as a preform to the beverage-filling operation for transport reasons. Only then are the preforms expanded to their full size in a so-called blow-stretch process and then filled with the liquids.

Despite the large quantities, it is necessary that the plastic bottles - and accordingly also the preforms - have a minimal error rate at best. This is because leaking liquids are at least problematic; in the case of chemical substances, this can also be dangerous. Particularly when filling foodstuffs, there is generally an increased requirement for the lowest possible proportion of defective plastic bottles for reasons of food safety. It can even happen that an entire batch has to be recalled if an error occurs - with the corresponding economic consequences.

Such high quality requirements can ultimately only be met economically by carrying out a regular inspection of the preforms produced, in particular a single item inspection, so that preferably neither systematic nor accidental errors can occur. For this purpose, a wide variety of inspection methods have already been proposed, which are mostly based on an optical inspection, since such an inspection process can be implemented in a comparatively simple and unproblematic manner.

In the optical test methods typically complex test systems are used, which consist of one or more cameras, specially adapted lighting means and special image processing processors. Transport devices are also often used, which are used to transport the preforms to be tested through the test system. During transport, the cameras take static or dynamic images of the preforms and forward them to the image processing processors. These use special test algorithms to detect the presence of defects based on the images supplied and the specified quality standards. A special sorting device removes the detected defective preforms from the system. The test speed plays an extremely important role.

However, a complete inspection of three-dimensional preforms is extremely complicated because the entire side wall surface cannot be captured with a single camera. In many conventional test systems, several cameras are used to solve this problem, for example, with which images of different side wall surfaces of the preform can be recorded. Of course, the use of multiple cameras makes the entire test system considerably more expensive. In addition, particularly powerful image processing processors must be used for simultaneous processing of several images from different side wall surfaces of the preform, which makes the systems even more expensive. Otherwise, a significantly lower test speed must be expected, which has a negative impact on production costs.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to propose a new method and a new device for the optical inspection of preforms which do not have the disadvantages of the prior art. In particular, an object of the present invention is to propose a new method and a new device for the optical inspection of preforms, which enable a quick, precise, efficient and reliable inspection of the entire side wall of preforms.

[0010] According to the present invention, these objects are achieved in particular by the elements of the independent claims. Further advantageous embodiments also emerge from the dependent claims and the description.

In particular, these objects of the invention are achieved by a method for the optical inspection of preforms, in which a preform is transported by means of a transport device, an image of a side wall surface of the preform being generated by means of a camera device, the preform being rotated by means of a rotating device an axis perpendicular to the direction of conveyance and is rotated over an imaging length of the conveying direction, and wherein the camera device can produce an image of the side wall surface of the preform over the entire imaging length.

Thanks to the method according to the invention, it is possible to use a camera device to produce an image of the side surface of the preform which corresponds to a larger area than that which could be recorded without rotating the preform. It is therefore no longer necessary for the optical inspection of the side wall surface of preforms to use different camera devices which depict different sides of the preform. In contrast to methods from the prior art, an expensive device for combining images from different cameras from different orientations is no longer required. The process is therefore cheaper and can be carried out faster.

In a first preferred embodiment of the method according to the invention, the imaging length is at least equal to the maximum circumference of the preform. This ensures that the preform is rotated by at least 360 ° over the imaging length. In this way, an image of the side surface of the preform can be generated, the length of which corresponds at least to the circumference of the preform. This allows an optimal optical inspection of opaque preforms with only one camera device.

In a further preferred embodiment of the method according to the invention, the camera device comprises a single camera, the camera being able to produce an image of the side wall surface of the preform over the entire length of the image by means of a tracking mechanism. As a result, a single camera can image the entire side wall surface of a preform. The process is therefore cheaper and can be carried out faster.

In a further preferred embodiment of the method according to the invention, the camera is a line camera, the longitudinal axis of the line camera being aligned parallel to the longitudinal axis of the preform. A very high spatial image resolution in the direction of its longitudinal axis can be achieved with a line scan camera. Nevertheless, a very high imaging speed can be guaranteed.

[0016] In a further preferred embodiment of the method according to the invention, the width of the sensor of the line scan camera is at least equal to the length of the preform. This allows the entire side surface of the preform to be checked with the line scan camera.

In a further preferred embodiment of the method according to the invention, the preform is illuminated with at least one static illuminant over the imaging length. The image quality can thereby be increased. The static illuminant can be selected according to the type of test. For example, the illuminant can be a visible light source, a UV light source, an infrared light source, or a laser.

In a further preferred embodiment of the method according to the invention, the tracking mechanism comprises a rail system, the camera being moved by means of the rail system during the conveyance of the preform over the imaging length parallel to the direction of conveyance. A rail system which enables the camera to be displaced parallel to the direction of transport of the preform represents a particularly simple tracking mechanism with which the camera can produce an image of the side surface of the preform over the entire length of the image.

In a further preferred embodiment of the method according to the invention, the preform is illuminated with a movable lighting device over the imaging length, the movable lighting device being moved with the camera. This enables optimal lighting controls for the preform to be achieved. The movable illuminant can be selected according to the type of test. For example, the illuminant can be a visible light source, a UV light source, an infrared light source or a laser.

In a further preferred embodiment of the method according to the invention, the tracking mechanism comprises a mirror, for example a reflection prism, the mirror being displaced over the image length parallel to the direction of conveyance during the conveyance of the preform, and the image of the preform reflected by the mirror is imaged with the camera. As a result, the camera can be held in place so that vibrations of the camera which would impair the image resolution can be avoided. In addition, a mirror or a reflection prism is lighter than a camera and its movement parallel to the preform is therefore easier to implement and can be done more quickly.

In a further preferred embodiment of the method according to the invention, the preform is illuminated with a movable illuminating device over the imaging length, the movable illuminating device being displaced with the mirror. This enables optimal lighting controls for the preform to be achieved. The movable illuminant can be selected according to the type of test. For example, the illuminant can be a visible light source, a UV light source, an infrared light source or a laser.

In a further preferred embodiment of the method according to the invention, the tracking mechanism comprises a mirror, for example a reflection prima, wherein the mirror is rotated about an image length during the transport of the preform over the image length and the image reflected by the mirror of the preform is imaged with the camera. This means that neither the camera nor the mirror need to be moved. The image resolution and the examination speed can be further increased.

In a further preferred embodiment of the method according to the invention, the preform is illuminated over the imaging length with a movable illuminant, the movable illuminant being rotated with the mirror. This enables optimal lighting controls for the preform to be achieved. The movable illuminant can be selected according to the type of test. For example, the illuminant can be a visible light source, a UV light source, an infrared light source or a laser.

In a further preferred embodiment of the method according to the invention, the rotating device comprises two belts, the two belts not rotating at the same speed over the imaging length. As a result, simultaneous rotation and conveyance of the preform over the length of the image can be achieved very simply and inexpensively.

In a further preferred embodiment of the method according to the invention, the rotating device comprises a rotating belt and a static guide. This makes it even easier to turn and move the preform.

In a further preferred embodiment of the method according to the invention, the transport device comprises a vacuum belt, by means of which the preforms are held.

In a further preferred embodiment of the method according to the invention, the preforms are checked with further cameras for checking the thread area, the neck area and the bottom of the preforms, the further cameras being aligned parallel to the longitudinal axis of the preform. This means that not only the side surface but also the entire preform can be checked optically.

At this point it should be mentioned that in addition to the described method for the optical inspection of preforms according to the invention, the present invention also relates to a corresponding device for the optical inspection of preforms.

BRIEF DESCRIPTION OF THE DRAWINGS In the following, embodiment variants of the present invention are described using examples. The examples of the designs are illustrated by the following attached figures:

Fig. 1 shows a schematic representation of a preform;

2 schematically shows a top view of a first preferred embodiment of the present invention;

3 schematically shows a top view of a second preferred embodiment of the present invention;

4 schematically shows a top view of a third preferred embodiment of the present invention;

5 schematically shows a top view of a fourth preferred embodiment of the present invention;

6 schematically shows a top view of a fifth preferred embodiment of the present invention.

Preferred embodiments of the invention Fig. 1 shows schematically a preform 20, the integrity and quality of which is to be checked by means of the present invention. A preform 20 comprises a threaded region 21, a neck region 22, a body region 23 and a bottom 24. The entire side wall surface 25 of the preform 20 is checked by the present invention by means of the camera device 40. So that the entire side wall surface 25 can be inspected, the preform 20 is preferably rotated about its longitudinal axis S in front of the camera device 40. Preferred embodiments of the test method according to the invention and the test device according to the invention are presented in detail below.

2 shows a schematic top view of a device 10 for the optical inspection of preforms, which can be used to implement the method according to a preferred embodiment of the present invention. The preforms 20 to be tested are introduced into the device 10 in the direction of transport A by means of a suitable device (not shown). The device 10 comprises a transport device 30, which is used to transport the preforms 20 to be tested. The transport device 30 comprises a first rotating belt

31, whose length B corresponds essentially to the entire length of the device 10, and a second belt

32, which is divided into two rotating belts 32 ', 32 and a static guide 33, preferably made of plastic or rubber. Over the length L, in this embodiment, the static guide 33 and the first rotating belt 31 form the rotating device 36 for rotating the preforms. Of course, the preforms could also be rotated by means of two belts that do not rotate at the same speed, or with one rotating and one non-rotating belt.

The transport device 30 additionally comprises an upper guide 34, by means of which the preforms 20 can be held. The upper guide 34 can advantageously be a static plastic guide or a belt rotating from above in the running direction. The transport device 30 also includes the light cabinets 35a and 35b for tracking the preforms and for triggering the image, and a rotary encoder (not shown here) for measuring the conveying speed of the preforms.

As explained above, the preforms 20 are inserted into the device 10 in the direction of transport A. In the preferred embodiment of FIG. 2, the belts 31, 32 ′ and 32 rotate at the same speed V. Accordingly, the preforms 20 are first conveyed in the direction of transport A after being introduced into the device 10 until they reach the static guide 33 , Over the length L of the static guide 33, the preforms 20 not only move translationally in the conveying direction A but also rotate about their longitudinal axis S, which is perpendicular to the conveying direction A. As soon as the preforms 20 reach the belt 32, they are conveyed again in a purely translatory manner by means of belts 31 and 32.

The length L of the static guide 33 is advantageously at least equal to the circumference of the preforms 20 with diameter D. The circumference is calculated on the basis of the maximum diameter D of the preforms 20 (see FIG. 1). The preforms 20 thus rotate over the length L by at least an angle of 360 °.

As can be seen in FIG. 2, the device 10 also comprises a first camera device 40. In this preferred embodiment, the camera device 40 comprises only one camera 40a, which can be moved parallel to the conveying direction by means of a tracking mechanism 41. In this preferred embodiment, the tracking mechanism 41 takes the form of a rail system 42. The tracking mechanism 41 also has a drive mechanism (not shown) by means of which the camera 40a can be moved translationally and parallel to the conveying direction A. The speed of the camera 40a in the conveying direction A is advantageously equal to the conveying speed V of the preforms 20. Thus, the camera 40a can image and check the entire side wall surface 25 of a preform 20 over the length L. The image of the entire side wall surface is then analyzed using an analysis device (not shown) in order to discover and sort out the defective preforms. Even if in this preferred embodiment the camera device 40 comprises only one camera 40a, it is of course possible to record the entire side wall surface of the preform 20 by means of a plurality of cameras 40a, which are arranged next to one another and in parallel in the conveying direction A. In this case, the tracking mechanism 41 can be omitted.

The camera 40a is preferably a line camera, the length of the line sensor of the camera 40a being the same as the length of the side wall surface 25 of the preforms 20. Line scan cameras have the great advantage that they enable a very high image resolution in one imaging direction and at the same time a very high recording speed.

Since the camera 40a is moved parallel to the preforms 20 at speed V, and since the preforms 20 rotate over the length L by at least an angle of 360 °, a high-resolution image of the entire side wall surface of the preforms 20 can be obtained using only one Camera are recorded. Since only one camera 40a is required, the test method can be carried out at a very high speed. In addition, and since the device 10 comprises only one camera 40a, a special device for composing images from different cameras is not necessary. The device 10 can thus be produced inexpensively. In order for the camera 40a to be moved at exactly the same speed as the preforms, the conveying speed V can be measured by means of light cabinets 35a and 35b.

In order to be able to take meaningful pictures of the side walls of the preforms, the device 10 also has a static lighting means 43. The lighting means 43 is advantageously configured such that it optimally illuminates the preform over the entire length L. Even if in FIGS. 2 to 6 the static lighting means 43 is shown on the side of the static guide 33, which corresponds to a rear light configuration, it is also conceivable that the static lighting means 43 on the side of the camera 40a, which means a light configuration corresponds to attach. The static illuminant 43 can be, in particular, a conventional visible light source, an infrared light source, a UV source, a laser or a combination thereof. As a result, the lighting means 43 can be adapted to the specific test.

The device advantageously also includes the movable lighting means 43 ', which is configured in such a way that it optimally illuminates the area of the preform 20 which is imaged by the camera 40a. The movable lighting means 43 'can advantageously be connected directly to the camera 40a or can also be mounted movably on the rail system 42. Similar to the static illuminant 43, the moveable illuminant 43 'may in particular be a conventional visible light source, an infrared light source, a UV source, a laser or a combination thereof. As a result, the lighting means 43 'can be adapted to the specific test.

While the side wall surface 25 of the preforms 20 can be optimally imaged and checked by means of the camera 40a, the device 10 for imaging and checking the neck area 22, the threaded area 21 and the bottom 24 of the preforms additionally comprises the further cameras 50, 51 and 52. The cameras 50, 51, 52 are arranged parallel to the longitudinal axis S of the preforms and can be both surface cameras and line cameras.

Even if in this and in the further preferred embodiments of the present invention the rotation of the preforms 20 is generated by means of the rotating belt 31 and the static guide 33, it is also conceivable that the rotation of the preforms also generated by means of two rotating belts which will rotate at different speeds.

Figure 3 shows a second preferred embodiment of the present invention. In comparison to the device 10 of FIG. 2, the camera 40a cannot be moved in this embodiment. The device 10 comprises a mirror 44 in the form of a reflection prism, which takes over the function of the tracking mechanism 41 in this embodiment. Of course, it goes without saying that a plane mirror could be used instead of a reflection prism. The reflection prism 44 can be driven by a drive 45, e.g. by means of a linear motor, parallel to the conveying direction A and at the conveying speed V of the preforms 20. In addition, the reflection prima 44 is oriented in such a way that the camera 40a can image the side wall surface 25 of the preform 20 over the entire imaging length L. As in the first preferred embodiment of the present invention, camera 40a is preferably a line scan camera. Thanks to the displaceable reflection prism 44, the entire side wall surface of the preforms 20 can be optimally imaged by means of the camera 40a.

The second preferred embodiment of the present invention has the advantage over the first embodiment that the reflection prism 44 is lighter than the camera 40a. As a result, the translational movement of the prism 44 is simpler and can be carried out more precisely. In addition, and since the camera 40a is fixedly mounted, vibrations which result from the movement of the camera 40a and which could impair the image quality can be avoided. The device 10 of the second preferred embodiment also includes the movable illumination means 43 ′, which preferably shifts simultaneously with the reflection prism 44. The reflection prism is advantageously semitransparent in the direction between the movable illuminant 43 ′ and the preform 20. As a result, the illuminant can be placed directly behind the reflection prism 44. In this embodiment, the device 10 may comprise a second fixed lighting means 43 in addition to or instead of the movable lighting means 43 ′. By means of a semi-transparent mirror 48, which can also be a semi-transparent prism, the light from the illuminating means 43 comes onto the prism 44, which redirects the light to the preform 20. The advantage of using the semitransparent prism 48 and the illuminant 43 is that the illuminant 43 can be placed laterally and does not have to be moved simultaneously with the prism 44, which increases the quality of the image of the preform 20.

In the embodiments of Figures 2 and 3, the slidable member, i.e. the camera 40a or the mirror 44 in the form of a reflection prism, shifted purely translationally. As a result, the movable element must be moved back to the original position after the side wall surface of a preform 20 has been completely imaged, so that the next preform can be checked. In order to enable the highest possible number of preforms to be tested, this return movement must take place as quickly as possible, which cannot be done without technical difficulties. Therefore, the third, fourth and fifth preferred embodiments, which are illustrated in FIGS. 4 to 6, represent good alternatives to a purely translatory return movement of the displaceable element.

In the third preferred embodiment of the present invention, which is shown schematically in Fig. 4, the reflection prima 44 and the movable lighting means 43 'are mounted on a closed carriage mechanism 46. As soon as the preform 20 has reached the belt 32, the reflection prism 44 and the illuminant 43 ′ are conveyed back to the original position by means of the carriage mechanism 46. Of course, a plurality of prisms 44 and lighting means 43 ′ can be mounted on the carriage mechanism 46, so that a very large number of preforms 20 can be imaged and checked per unit of time. Of course, it goes without saying that one or more plane mirrors could also be used instead of the reflection prisms in this embodiment.

Even if the other cameras 50, 51 and 52 are not shown in FIG. 4, it is of course clear that the third embodiment of the device 10 can also include these cameras.

Fig. 5 shows a schematic representation of a fourth preferred embodiment of the present invention. In this embodiment, the reflection prism 44 and the movable lighting means 43 ′ are mounted on a rotary motor so as to be rotatable about an axis that is essentially perpendicular to the direction of conveyance A. This embodiment has the advantage that the rotational movement of the reflection prism 44 and the movable illuminant 43 'can take place at a very high rotational speed, which enables a large number of preforms 20 to be imaged per unit of time. Of course, the rotational movement of the reflection prism 44 and the movable illuminant 43 'could be oscillating, making a complete rotation unnecessary. Of course, it goes without saying that one or more plane mirrors could also be used instead of the reflection prisms in this embodiment. In this embodiment, the device 10 may comprise a second fixed lighting means 43 in addition to or instead of the movable lighting means 43 ′. By means of a semi-transparent mirror 48, which can also be a semi-transparent prism, the light from the illuminating means 43 comes onto the prism 44, which redirects the light to the preform 20. The advantage of using the semitransparent prism 48 and the illuminant 43 is that the illuminant 43 can be placed laterally and does not have to be moved simultaneously with the prism 44, which increases the quality of the image of the preform 20.

In this fourth embodiment too, the camera 40a preferably takes the form of a line scan camera. As can be seen in the detailed view shown in FIG. 5, a plurality of reflection prisms 44 and lighting means 43 ′ can be mounted on the rotary motor. This again enables the number of preforms 20 to be increased per unit of time, which can be checked by means of device 10.

FIG. 6 shows a fifth preferred embodiment of the present invention, in which softer belts 32 'are absent, and in which the preforms 20 are introduced directly into the region of the transport device 30 which corresponds to the static guide 33. As a result, the entire length B of the device 10 can be shortened. The imaging principle of the side wall surface 25 of the preform 20 in this embodiment is the same as that of the fourth preferred embodiment. As can be seen in the detailed view shown in FIG. 6, a plurality of reflection prisms 44 and lighting means 43 ′ can be mounted on the rotary motor. Of course, it goes without saying that one or more plane mirrors could also be used instead of the reflection prisms in this embodiment. In this embodiment too, the device 10 can comprise a second fixed lighting means 43 in addition to or instead of the movable lighting means 43 '. By means of a semi-transparent mirror 48, which can also be a semi-transparent prism, the light of the illuminating means 43 comes onto the prism 44, which transmits the light onto the preform 20. The advantage of using the semi-transparent prism 48 and the illuminating means 43 is that the illuminating means 43 can be placed laterally and does not have to be moved simultaneously with the prism 44, which increases the quality of the image of the preform 20.

The invention is not limited to the described embodiments. It will be readily apparent to the person skilled in the art that further developments and modifications are readily possible within the scope of the protected invention. Device elements can be replaced with other elements that perform the same or similar functions as needed. Additional facilities and elements can also be provided. These and other measures and elements fall within the scope of the invention, which is defined by the claims.

Claims (32)

claims 1. A method for the optical inspection of preforms, in which a preform (20) is conveyed by means of a transport device (30), an image of a side wall surface of the preform (20) being generated by means of a camera device (40), characterized in that by means of a rotating device (36) rotates the preform (20) about an axis perpendicular to the conveying direction and over an imaging length (L) of the conveying direction, and that the camera device (40) can produce an image of the side wall surface of the preform over the entire imaging length (L) , 2. The method according to claim 1, characterized in that the imaging length (L) is at least equal to the maximum circumference of the preform (20). 3. The method according to any one of claims 1 or 2, characterized in that the camera device (40) comprises a single camera (40a) and that by means of a tracking mechanism (41), the camera (40a) an image of the side end wall surface of the preform over the entire image length (L) can generate. 4. The method according to claim 3, characterized in that the camera (40a) is a line camera, wherein the longitudinal axis of the line camera is aligned parallel to the longitudinal axis (S) of the preform (20). 5. The method according to claim 4, characterized in that the width of the sensor of the line scan camera is at least equal to the length of the preform (20). 6. The method according to any one of claims 1 to 5, characterized in that the preform is illuminated with at least one static lighting means (43, 43) over the imaging length (L). 7. The method according to any one of claims 3 to 6, characterized in that the tracking mechanism (41) comprises a rail system (42), and that by means of the rail system (42) the camera (40a) during the transport of the preform (20) over the Image length (L) is shifted parallel to the direction of transport. 8. The method according to claim 7, characterized in that the preform is illuminated with a movable illumination means (43 ') over the imaging length (L), the movable illumination means (43') being displaced with the camera (40a). 9. The method according to any one of claims 3 to 6, characterized in that the tracking mechanism (41) comprises a mirror (44), for example a reflection prism, the mirror (44) during the conveyance of the preform (20) over the length of the image (L) is shifted parallel to the direction of conveyance, and that the image of the preform (20) reflected by the mirror (44) is imaged by the camera (40a). 10. The method according to claim 9, characterized in that the preform is illuminated with the movable illuminating means (43 ') over the imaging length (L), the movable illuminating means (43') being displaced with the mirror (44). 11. The method according to any one of claims 3 to 6, characterized in that the tracking mechanism (41) comprises a mirror (44), for example a reflection prism, the mirror (44) during the conveyance of the preform (20) over the length of the image (L) is rotated about an axis perpendicular to the direction of conveyance, and that the image of the preform (20) reflected by the mirror (44) is imaged by the camera (40a). 12. The method according to claim 11, characterized in that the preform is illuminated with the movable lighting means (43 ') over the imaging length (L), the movable lighting means (43') with the mirror (44) over the imaging length (L) is rotated. 13. The method according to any one of the preceding claims, characterized in that the rotating device (36) comprises two rotating belts (31,32), wherein the belts (31,32) do not rotate at the same speed over the imaging length (L). 14. The method according to any one of claims 1 to 11, characterized in that the rotating device (36) comprises a rotating belt (31) and a static guide. 15. The method according to any one of the preceding claims, characterized in that the transport device (30) comprises a vacuum belt, by means of which the preforms are held. 16. The method according to any one of the preceding claims, characterized in that the preforms with further cameras (50, 51, 52) for checking the threaded area (21), the neck area (22) and the bottom (24) of the preforms (20) checked the other cameras (50, 51, 52) are aligned parallel to the longitudinal axis (S) of the preform (20). 17. Device (10) for the optical inspection of preforms, comprising a transport device (30) for conveying the preforms (20), a camera device (40) for imaging a side wall surface of the preform (20), characterized in that the device (10) comprises a rotating device (36) for rotating the preform (20) about an axis perpendicular to the conveying direction and over an imaging length (L) of the conveying direction, and that the device (10) is configured such that the side wall surface extends over the entire imaging length (L) of the preform (20) can be imaged with the camera device (40). 18. The apparatus according to claim 16, characterized in that the imaging length (L) is at least equal to the maximum circumference of the preform (20). 19. Device according to one of claims 17 or 18, characterized in that the camera device (40) comprises a single camera (40a) and that the device (10) comprises a tracking mechanism (41) which is configured such that over the entire Imaging length (L) the side wall surface of the preform (20) can be imaged with the camera (40a). 20. The apparatus according to claim 19, characterized in that the camera (40a) is a line camera, wherein the longitudinal axis of the line camera is aligned parallel to the longitudinal axis (S) of the preform (20). 21. The apparatus according to claim 20, characterized in that the width of the sensor of the line camera is at least equal to the length of the preform (20). 22. Device according to one of claims 17 to 21, characterized in that the device comprises at least one static lighting means (43, 43), by means of which the preform can be illuminated over the imaging length (L). 23. Device according to one of claims 19 to 22, characterized in that the tracking mechanism (41) comprises a rail system (42), that the camera (40a) is mounted on the rail system (42), and that the camera (40a) is parallel is displaceable to the direction of transport. 24. The device according to claim 23, characterized in that the device (10) comprises a movable illumination means (43 ') for illuminating the preform (20) over the imaging length (L), the movable illumination means (43') with the camera ( 40a) is displaceable. 25. Device according to one of claims 17 to 21, characterized in that the tracking mechanism (41) comprises a mirror (44), for example a reflection prism, which can be displaced parallel to the direction of conveyance and over the imaging length (L), the mirror (44) is oriented such that the image of the preform (20) reflected by the mirror (44) can be imaged over the entire imaging length (L) by the camera (40a). 26. The device according to claim 25, characterized in that the device (10) comprises the movable lighting means (43 ') for illuminating the preform (20) over the imaging length (L), the movable lighting means (43') with the mirror ( 44) is displaceable. 27. Device according to one of claims 17 to 21, characterized in that the tracking mechanism (41) comprises at least one mirror (44), for example a reflection prism, which can be rotated about an axis perpendicular to the direction of conveyance, by means of rotation of the mirror ( 44) the camera (40a) can image the image of the preform (20) reflected by the mirror (44) over the entire image length (L). 28. The device according to claim 27, characterized in that the device (10) comprises the movable illumination means (43 ') for illuminating the preform (20) over the imaging length (L), the movable illumination means (43') with the reflection prism ( 44) is rotatable. 29. The device according to one of claims 17 to 28, characterized in that the rotating device (36) comprises two rotating belts (31, 32), the belts (31, 32) being rotatable at uneven speed over the imaging length (L). 30. Device according to one of claims 17 to 29, characterized in that the rotating device (36) comprises a rotating belt (31) and a static guide. 31. Device according to one of claims 17 to 30, characterized in that the transport device (30) comprises a vacuum belt. 32. Device according to one of claims 17 to 31, characterized in that the device (10) further cameras (50, 51, 52) for optical inspection of the threaded area (21), the neck area (22) and the bottom (24) of the Preforms (20) comprises, wherein the further cameras (50, 51, 52) are aligned parallel to the longitudinal axis (S) of the preform (20). c =>