WO2000066998A2

WO2000066998A2 - Method and device for detecting an image of an essentially cylindrical surface

Info

Publication number: WO2000066998A2
Application number: PCT/AT2000/000104
Authority: WO
Inventors: Gerhard Kucera; Michael Rudolf; Hubert Keller; Franz Seiser
Original assignee: Festo Gesellschaft M.B.H.
Priority date: 1999-04-30
Filing date: 2000-04-26
Publication date: 2000-11-09
Also published as: AU3946200A; WO2000066998A9; ATA77999A; AT408385B; WO2000066998A8; WO2000066998A3

Abstract

The invention relates to a method for detecting an image of an essentially cylindrical surface (13) such as the surface of a hollow space or outer casing of an essentially cylindrical work piece. The inventive method comprises an image detecting unit (1) and an image evaluation unit (2). The image detecting unit (1) is provided with all-round optics (6) which detect light from the entire circumference of the cylindrical surface (13) and projects said light onto a sensor (8). The all-round optics (6) and the cylindrical surface (13) are moved in relation to each other. After a movement along a movement path which can be predetermined has taken place, the image evaluating unit (2) stores the partial image of the surface, whereby said image has just been detected by the sensor (8) and joins all partial images to form an entire image of the surface. The all-round optics (6) and the cylindrical surface (13) are continuously moved in relation to one another.

Description

Method and device for acquiring an image of a substantially cylindrical surface

The invention relates to a method for detecting an image of a substantially cylindrical surface, such as surface of a ^{^} cavity and outer jacket of a substantially cylindrical workpiece.

The term “image processing” denotes the interpretation of an image, object or scene by using contactless sensors with the aim of obtaining information, monitoring machines or processes or checking workpieces. An image processing system usually consists of the components: lighting, Sensor technology with optics, image digitization / image processing and image evaluation / generation of identification and control data.

Today, most image processing systems use white light, infrared and / or UV lamps as lighting and CCD cameras are the most widespread as imaging sensors. The semiconductor CCD cameras have become very cheap, small and light. They are available as a matrix sensor (2D arrangement, usually 780x580 pixels) and also as a line sensor (1D arrangement, from 256 to 8000 pixels). Image processing is used to process the captured image so that it can be evaluated in the subsequent stages with relatively little effort. Here the image is rectified, the noise and redundant redundancies eliminated by data compression. In the next step, the pre-processed image is evaluated, errors classified or objects identified, which is done using appropriately programmed computers. Intelligent evaluation algorithms such as neural networks or fuzzy logic are often used here. At the end of the chain there are output variables that can be used as identification or control data. The most important features of an image processing system are: It works without contact and non-destructively, the results achieved with it are reproducible and objective, i.e. do not depend on the current condition of a human examiner. In addition, the test results - achieved by means of EDP - are particularly easy and clearly documentable.

The present invention relates to the use of an image processing system in the field of surface inspection of - preferably finished - workpieces and specifically relates only to the image acquisition part of such an image processing system.

In many production processes, a visual final inspection of the product is absolutely necessary for quality control. This task is usually carried out manually by specially trained personnel. The importance of surface quality for the end product can be in the following areas:

Operational safety - Ensuring the function of the product Marketing - Optical quality and visual impression of the product Process optimization - feedback to the process

An image processing system offers decisive advantages especially in the field of surface inspection: It inspects objectively, reproducibly, fatigue-free and regardless of the condition of the staff.

It is the object of the present invention to specify a method of the type mentioned at the outset, which runs particularly quickly.

According to the invention, this is achieved by an image acquisition unit and an image evaluation unit, the image acquisition unit having all-round optics, which detects light from the entire circumference of the cylindrical surface and projects it onto an optical sensor, the all-round optics and cylindrical surface being moved relative to one another and after completion of a predeterminable movement path Partial image of the surface that has just been captured by the sensor is stored by the image evaluation unit and all partial images are combined to form an overall image of the surface and the all-round optics and cylindrical surface are continuously moved relative to one another.

The required quickest possible procedure is primarily achieved by the continuous relative movement of the surface compared to the all-round optics. Times in which the all-round optics stand still and which would lead to a slowdown of the overall process are thus completely avoided. In a further embodiment of the invention it can be provided that the speed of the relative movement between the all-round optics and the surface is reduced for the duration of the storage of a partial image.

This ensures that the current partial image can be saved completely and in good time before the projection of the subsequent partial image. The reduction in the speed of movement is associated with a slowing down of the detection process, but this has only an insignificant effect.

According to a preferred embodiment of the invention it can be provided that the speed of the relative movement between the all-round optics and the surface is chosen to be the same throughout.

A slight slowing down of the process sequence just mentioned is thus completely avoided.

According to a first embodiment of the invention it can be provided that the surface is kept still and the all-round optics is moved further relative to the surface.

This variant is particularly suitable for workpieces that are large and / or heavy compared to the all-round optics and therefore can only be moved with greater effort than these.

In this connection it can be provided that the optical sensor is held stationary with respect to the all-round optics and the light detected by the all-round optics. preferably using optical fibers or mirror systems, is projected onto the optical sensor.

The spatial separation of the all-round optics and sensor thus achieved means that the part of the image acquisition unit to be moved can be manufactured with very small geometric dimensions. In connection with the detection of cavity surfaces, this means that the method according to the invention can also be used for cavities with very small diameters.

In contrast to the embodiment just mentioned, provision can also be made for the optical sensor to be rigidly connected to the all-round optics and to be moved together with the latter in relation to the surface.

Under certain circumstances, complicated systems for light transmission and the costs associated with their production can be avoided.

According to a second embodiment of the invention, it can be provided that the all-round optics are held immovably and the surface is moved further relative to the all-round optics.

This design variant should be selected in particular if the surface whose image is to be captured is that of an endless strand of workpieces, e.g. an extruded plastic strand, a glass strand or the like.

Furthermore, it can be provided that the image evaluation unit recognizes defects in the surface by comparing the overall surface image with a reference image.

Another object of the invention is to provide a device of the simplest possible design for carrying out the method just discussed. According to a first variant of the invention, this is achieved by an image acquisition unit and an image evaluation unit, the image acquisition unit having all-round optics, which detects light from the entire circumference of the cylindrical surface and projects it onto an optical sensor, the all-round optics and cylindrical surface being held movable relative to one another and the optical sensor is a ring sensor. According to a second variant of the invention, this is achieved by an image acquisition unit and an image evaluation unit, the image acquisition unit having all-round optics, which detects light from the entire circumference of the cylindrical surface and projects it onto an optical sensor, the all-round optics and cylindrical surface being kept movable relative to one another and optical sensor is a matrix sensor. Both types of sensors can be read out particularly quickly, so that a smooth execution of the method according to the invention is ensured. In a further embodiment of the invention it can be provided that the optical sensor is implemented in CMOS technology or in CCD technology. Both technologies show sufficient for the application area in question

Functional reliability.

Furthermore, it can be provided that the all-round optics and, if appropriate, the optical sensor are fixed on a linear drive that can be moved continuously.

This ensures the further movement of the all-round optics along a completely straight line and thus a constant spacing of the all-round optics from the surface.

In a further embodiment of the invention, it can be provided that the linear drive is formed by an electrical spindle drive, since such drives can be produced in a relatively simple manner with the travel accuracy required in the context in question.

In this connection it can be provided that the threaded spindle of the

Spindle drive is formed by an electrical stepper or servo motor, because such drives are particularly easy to control.

According to another possible embodiment, it can be provided that the linear drive is formed by a pneumatic smooth-running cylinder.

Such a drive also has the necessary travel accuracy.

The invention is described in more detail with reference to the accompanying drawings, in which particularly preferred exemplary embodiments are shown. It shows:

1 shows a block diagram of a device according to the invention;

Fig. 2 and 3 skew of all-round optics 6 with ring sensors 8 in principle

Presentation;

4a, b an area or matrix sensor and a ring sensor each in plan;

5 shows the surface 13 of a hole to be inspected in an oblique view;

6 shows the overall picture of the bore according to FIG. 5;

7 shows the circuit diagram of an image capturing component 9 which is held in CMOS technology;

8a, b two possible courses of the speed of the relative movement between

All-round optics and surface to be recorded Diagram form;

9 shows a section through an inventive device for detecting a

Outer surface;

9a, b a ring sensor that can be used in the device according to FIG

Area sensor in each case in the floor plan.

In Fig.l is a block diagram of an inventive device for inspecting the

Surface of a cavity shown. With the help of this device, the surfaces of bores as well as the inner surfaces of cups and drinking glasses can be inspected. The principle of the invention is not, however, applicable to them

Examples limited, but rather can be used with any type of cavity.

In addition, the images of other cylindrical surfaces, namely the

Outer surface of cylindrical workpieces, according to the principle of the invention be recorded. The basic structure of the necessary devices is the same. A device suitable for inspecting cavity surfaces is therefore described below.

According to FIG. 1, such a device essentially comprises two main components, namely on the one hand the image acquisition unit 1 and on the other hand the image evaluation unit 2.

The image capturing unit 1 has all-round optics 6, which captures light from the entire circumference of the cylindrical surface 13 and projects it onto an optical sensor 8, 8 '(see FIG. 2, 3). The electrical output of this sensor 8, 8 'is connected to the image evaluation unit 2.

Said sensor 8,8 'is not so large that the entire surface of the object to be inspected

Cavity could be projected onto it, rather only a section - which, as explained in more detail below, a ring disk-shaped, the entire circumference

Section of the surface is to be projected onto it.

The image of the entire cavity must therefore be captured step by step, for what

All-round optics 6 and cylindrical surface 13 can be moved relative to each other and after

Conclusion of a predeterminable movement path, the partial image of the surface that has just been detected by the sensor 8, 8 'is stored by the image evaluation unit 2.

Those obtained during the further movement of the surface relative to the all-round optics 6

Partial images are combined into a total image of the surface in a manner also described below.

According to FIG. 1, the image acquisition unit 1 comprises an endoscope 3, which is fixed on the slide 5 of a linear drive 4 which is mounted in a translationally displaceable manner.

This linear drive 4 can be of any design, for example, a

Spindle drive (threaded spindle is rotatably driven about its longitudinal axis, slide 5 has an internal thread which is penetrated by the threaded spindle) or a pneumatic linear drive (smooth-running pneumatic cylinder, its free

Piston rod end forms the carriage 5) can be specified. The drive of the

Threaded spindle is preferably carried out by an electrical step or

Servo motor, which - as will be discussed in more detail below - continuously drive the threaded spindle.

The already mentioned all-round optics 6 are fixed at the tip of the endoscope 3. With the

The term “all-round optics” is understood in connection with FIG. 1 to be an objective which, due to its design, is permeable to any light which is incident on it in a plane running approximately normal to its geometric axis of symmetry 7 (see FIG. 2)

As seen from the symmetry axis 7 of the all-round optics 6, a “360-degree view” is possible.

The relative movement between surface 13 and all-round optics 6 is here achieved in that the surface 13 or the workpiece on which this surface 13 is located is kept still and the all-round optics 6 is moved relative to the surface 13. Another component of the image acquisition unit 1 is the optical sensor 8, 8 'onto which the light passing through the all-round optics 6 is projected. Such image sensors are known per se and are designed, for example, as ring sensors 8 or as surface or matrix sensors 8 '.

This sensor is particularly preferably designed as a ring sensor 8, which means that its individual image acquisition components 9 are arranged in a ring. In the simplest case, these image acquisition components 9 are fixed on the lateral surface of a cylindrical support 10, as shown in FIG. With this design, the light incident through the all-round optics 6 does not need to be deflected, but can be made to fall directly on the sensor 8.

A further, more common design of a ring sensor 6, as shown in FIG. 3, is to mount the individual image acquisition components 9 on a flat carrier surface 11, but to arrange them there in a ring. The light incident through the all-round optics 6 must be redirected to this ring-shaped sensor 8, which can be done, for example, by a deflecting mirror which is designed as a desk mirror 12. Such a desk mirror 12 has, as can be seen from FIG. 3, the shape of a truncated cone, the outer surface of which is mirrored. It is also possible to forward the incident light using a light guide.

Both types of ring sensors 8 only have a single image line, so that, in contrast to surface sensors 8 '(cf. FIG. 4 a), they cannot detect a larger image, but only an image line.

In the case of a surface or matrix sensor 8 ', as shown in FIG. 4a in detail, the image acquisition components 9 are arranged in the form of a rectangular matrix, so that a larger-area image can be projected onto this sensor design. Both sensor designs can be used according to the invention, which will be explained further below.

Furthermore, both ring sensors 8 and area sensors can be constructed in different technologies, the most common examples being CMOS technology and CCD technology. The technology of the sensor 8, 8 'is also not essential to the invention and is therefore freely selectable.

In addition, the position of the sensor 8, 8 'can be selected, whereby there are basically two possibilities for this: On the one hand — especially if the sensor 8, 8 ′ is designed according to FIG. 2 — the sensor 8, 8 ′ could also be at the tip of the endoscope 3, namely within the all-round optics 6. The electrical signals generated by it and corresponding to the light incident on the sensor 8, 8 ′ must then be forwarded to the image processing unit 2 by means of corresponding electrical lines 24. On the other hand, the sensor 8,8 'could be fixed outside the all-round optics 6, for example at the other end of the endoscope 3 or otherwise on the slide 5 of the linear drive 4 his. The light incident through the all-round optics 3 would have to be fed to the sensor 8,8 ', which can be done, for example, by means of light guides or mirror systems. Using the last-described embodiment, the endoscope 3 can be designed with a smaller diameter, so that it can also be used for the inspection of narrower cavities.

Both possible arrangements have in common that the sensor 8, 8 'is rigidly connected to the all-round optics 6 and is moved together with the latter in relation to the surface.

In addition, as shown in FIG. 1 with dashed lines, it is also possible to position the sensor 8,8 'outside the linear drive 4, i.e. to be arranged stationary with respect to the all-round optics 6 and to transmit the light detected by the all-round optics 6 to the sensor 8, 8 ', which can preferably be done using light guides 23 or mirror systems. This embodiment is also particularly suitable for the inspection of cavities with small diameters.

Illumination of the cavity is also provided, which is preferably also fixed on the endoscope 3.

An image of the surface of a bore is recorded by means of a system constructed in this way as described below with reference to FIG. 5. For the sake of clarity, FIG. 5 shows only the surface 13 of a hole, but not the workpiece within which this hole is actually made. The particularly preferred embodiment of the sensor 8 as a CMOS ring sensor is also assumed: the endoscope 3 comprising at least the all-round optics 6, possibly also the CMOS ring sensor 8, is pushed into the hole to be inspected along its axis of symmetry 14. If the endoscope 3 is pushed so far into the bore that the image of a first annular disk-shaped section 15, the height h of which corresponds to the component height p of the ring sensor 8, strikes the ring sensor 8, this ring sensor 8 is read out by the image processing unit 2. The predeterminable movement path, after the conclusion of which the partial image of the surface 13 just detected by the sensor 8, 8 'is stored by the image evaluation unit 2, corresponds to a pixel height p in the case of a single-line ring sensor 8.

In order to be able to carry out this reading, the image processing unit 2 has the components clocked in FIG. 1, switches 16, intermediate storage 17 and total image storage 18. Each image capturing component 9 of the sensor 8 delivers a value, the size of which corresponds to the intensity of the image capturing in question. Component 9 corresponds to falling light. A CMOS ring sensor 8 comprising 2048 image acquisition components 9 (= pixels) is preferably used, so that the output of the CMOS ring sensor 8 comprises 2048 electrical signals. These signals are fed to the switch 16, which is connected to an intermediate memory 17 which has a number of memory locations corresponding to the number of image acquisition components 9. Is like described the endoscope 3 so far in the bore that the light of the first annular disc-shaped section 15 strikes the ring sensor 8, the switch 16 is controlled by a displacement sensor 19, ie caused to switch through, whereby the current

Sensor values are present at the buffer store 17 and are stored there. In this

Intermediate memory 17 downstream total image memory 18 in the

Finally, intermediate values 17 are combined to form an overall image 21 of the surface, simply by storing the values of each surface section

15, 20, 22 in the relevant line of an image file (see Fig. 6).

After an image line has been recorded, the endoscope 3 is moved further into the bore until the ring sensor 8 lies at the level of a second section 20 and the ring sensor 8 is read out again. Then the endoscope 3 is moved again and the ring sensor

8 read out. These steps are repeated until the endoscope 3 has been passed through the entire bore.

There are ring-shaped sections 15, 20, 22 of the bore surface from

Ring sensor 8 is detected, which is combined by the downstream image processing unit 2 to form an entire, leveled image of the surface (see FIG. 6). The height h of each detected strip-shaped section 15, 20, 22 of the surface 13 is as high as one

Image recording element 9 (= pixel) of the ring sensor 8.

The CMOS ring sensors 8 used with preference worked very quickly, they indicate

Acquisition rates in the range of 25 kHz, which means that they can be read out 25,000 times per second. It is precisely the use of such CMOS ring sensors that makes it possible to cycle the endoscope 3 — not as may be suspected, as the above detailed functional explanation may suggest, but instead to pass it continuously through the bore in the manner according to the invention and to record said strip-like surface sections 15, 20, 22 during this uninterrupted movement and save it in the overall image file.

With the wording "uninterrupted" in the context of this description and

Claims understood a movement, the speed of which at no time

Zero drops. The speed of the relative movement is preferably between

All-round optics 6 and surface 13 are consistently chosen to be of the same height, so that there is a continuous movement (see FIG.

But it is also within the scope of the invention that the speed of said

Relative movement is reduced for the duration of the storage of a partial image (cf.

Fig. 8b).

The CMOS ring sensor 8 is therefore read out each time a path corresponding to the pixel height h is covered, but without stopping the endoscope 3.

The basic structure of an image acquisition system using CMOS technology

Component, that is a pixel of the CMOS ring sensor 8, is shown in FIG. such

Sensors offer many advantages over conventional CCD sensors. In particular they have a higher dynamic range: While CMOS sensors have about 120 dB, which allows detailed recordings even in high-contrast environments, CCD sensors, on the other hand, only have 70 to a maximum of 80dB. This significantly higher modulation range makes it easier to identify defects on reflective surfaces, such as those that can occur during die inspection in die-cast parts.

CMOS sensors do not show the blooming effect that occurs with CCD sensors if a very bright light beam remains in the same place for too long. Pixels saturated by the intense lighting can no longer hold their charge, so that they flow to neighboring pixels and also saturate them. The image information of the affected pixels is lost. As can be seen from the above explanations, the sampling frequency, i.e. the frequency with which the ring sensor 8 is read out can be directly proportional to the travel speed of the endoscope 3. In order to achieve this coupling of sampling frequency and travel speed, the displacement sensor 19 is connected to the linear drive 4. This displacement sensor 19 triggers the switch 16 by one pixel height each time the endoscope 3 is moved, so that the image evaluation device 2 is caused to read out the ring sensor 8. An advantage of this triggered scanning is that the travel speed of the endoscope 3 can be freely selected within wide limits. Thus, e.g. in blind holes are gently braked without changing the resolution in the captured image. If the coupling of the covered endoscope path and scanning is made changeable, i.e. the length of the path, after which a new scan has to be carried out, is kept changeable, the recorded image can be given a variable resolution: if the endoscope path between two scans is increased, the resolution of the image in this area is reduced, conversely, the endoscope path between two scans is reduced, the resolution of the image increases. Areas of the hole that are of no interest (e.g. because experience has shown that surface defects do not occur there or because defects in such areas are less interesting for assessing the quality of the hole) can be scanned with reduced resolution and at a higher speed.

The processing of the overall image 21 of the surface, i.e. its examination for any existing defects in the bore surface 13 is carried out by the image evaluation unit 2, which, in addition to the total memory 18, comprises a computer on which corresponding image processing software runs, which recognizes defects in the surface by comparing the overall surface image with a reference image. In deviation from the previous discussion, it is possible to project the light passing through the all-round optics 6 onto a matrix sensor 8 'shown in FIG. 3, where it likewise strikes in a ring.

The most important functional difference to the ring sensor 8 is that not only one line, the height h of which corresponds to the pixel height p, is projected onto this sensor 8 ^' , but rather that the portion projected onto the sensor 8 'is a wider, but also a ring-shaped portion of the surface 13. In order to record the overall image of the surface 13, a smaller number of partial images must therefore be recorded.

The predeterminable movement path, after the completion of which the partial image of the surface 13 just detected by the sensor 8, 8 'is stored by the image evaluation unit 2, corresponds in the case of a surface sensor 8' to the width of the surface section which can be projected onto the sensor 8 '.

Even when a matrix sensor 8 'is used, there is an uninterrupted displacement of the endoscope 3, which can be continuous movement according to FIG. 8a or can take place at a reduced speed during the storage of the partial images (cf. FIG. Δb).

As mentioned at the beginning, in order to obtain an overall image, it is only important to move the all-round optics 6 and surface 13 relative to one another. This relative movement can also be achieved in that the all-round optics 6 are held immovably and the surface is moved relative to the all-round optics 6. For this purpose, the workpiece having the surface 13 is simply fixed on the slide 5 of the linear drive 6. Here, too, the optical sensor 8,8 'can be arranged in the immediate vicinity of the all-round optics 6 and its outputs can be connected to the image evaluation device 2 by means of electrical lines 24, or an objectionable arrangement of the all-round optics 6 and the sensor 8,8' can be provided, the the light passing through the all-round optics 6 is fed to the sensor 8.8 'by means of light guides and / or mirror systems.

As already mentioned, the principle according to the invention can also be used to record the image of the outer lateral surface of a cylindrical body.

An image acquisition unit 1 suitable for this is shown in FIG. The most significant difference from the previously discussed device for recording the image of a cavity surface lies in the other design of the all-round optics 6.

The term "all-round optics" in connection with the detection of an essentially cylindrical outer jacket is understood to mean a lens which is designed such that it can detect light from the entire circumference of the outer jacket surface. From the axis of symmetry 7 of such an all-round lens 6, one is therefore seen "All-round view" possible around the entire circumference of the outer jacket.

A possible embodiment of such an all-round optics 6 is shown in FIG. 9: It consists of a prismatic mirror body which is designed as a desk mirror 25, the mirror surface 26 of which is preferably frustoconical and semi-transparent on the inside. This desk mirror 25 has a through hole 29, the axis of symmetry 27 of which coincides with the optical axis 7 of the desk mirror 25. The workpiece 28, the surface 13 of which is to be imaged, is passed through said through bore 29, which can again be done by means of a linear drive 4, not shown in detail.

A plane mirror 30 is arranged above the desk mirror 25, which is arranged inclined to the optical axis of the desk mirror 25 and serves to deflect the light coming from the desk mirror 25 onto the sensor 8,8 '. On the side of this plane mirror 30 there is an objective 31 for optical imaging; The optical sensor 8, 8 'is arranged behind the objective 31.

The workpiece 28 is illuminated by a plurality of light beams 32, 32 'surrounding the workpiece 28 in an annular manner, the angle of incidence of the light beams 32, 32' on the surface 13 of the workpiece 28, with respect to the optical axis 7, being not equal to 90 °, so that do not place the light beams 32, 32 'and the optical axis 7 perpendicular to one another, but the light beams penetrate the optical axis at an angle. The desk mirror 25 can be translucent in a suitable manner in the area of incidence of the light beams 32, 32 'so that the light beams 32, 32' surrounding the workpiece 28 penetrate the desk mirror 25 and the semi-transparent mirror surface 26 and within a certain width on the entire circumferential surface Fall surface of the workpiece 28 and there scan a more or less narrow surface ring. Or the workpiece 28 is illuminated in a ring laterally above the desk mirror 25. From there, the light is reflected onto the mirror surface 26 or scattered light reaches where the reflected light 33, 33 'falls upwards onto the plane mirror 30, which contains the light throws on the lens 31, which bundles the light and images it according to the imaging scale on the sensor 8,8 '.

Analogous to the detection of a cavity surface described at the beginning, an annular disk-shaped section of the surface 13 is projected onto this sensor 8, 8 '. After readout of the sensor 8,8 'and storage of the sensor ^8,8' image data supplied, the workpiece is moved further to the width of a 'detectable by the sensor 8.8 surface portion 28, which is carried out further process continuously. A continuous movement according to FIG. 8a can be provided or the movement speed according to FIG. 8b can be reduced to save each partial image.

Furthermore, this sensor 8, 8 'can either be designed as a single-line ring sensor 8 (FIG. 9a) or by a matrix sensor 8' (FIG. 9b), the technology of the sensor being selectable in each case. however, CMOS or CCD sensors are preferably used, in particular ring sensors held in CMOS technology.

When using ring sensors 8, the individual partial images again have a height h corresponding to the pixel height p of these sensors 8; when using surface sensors 8 ', the individual partial images can be wider. Corresponding to the width of the surface section that can be projected onto the sensor 8, 8 ′,

Movement path to choose, after the completion of that just detected by the sensor 8,8 '

Surface partial image is stored by the image evaluation unit 2.

9, in order to achieve the relative movement between surface 13 and all-round optics 6, the workpiece 28 can also be held immovably and the all-round optics 6 can be moved, for which purpose the latter on the carriage 5

Linear drive 4 is fixed. The components of the plane mirror 30, lens 31 and sensor 8, 8 'can also be kept movable, that is, they can also be fixed on the slide 5 of the linear drive 4, or they can also lie outside the linear drive 4, that is, they can be held immovably with respect to the all-round optics 6.

Although not shown in explicit drawings and explained in detail, the

All-round optics 6 can also be designed in any other design.

In deviation from FIG. 9, the light beams can also be passed on by means of light guides.

Claims

PATENT CLAIMS

1. A method for capturing an image of an essentially cylindrical surface (13), such as the surface of a cavity or outer jacket of an essentially cylindrical workpiece, characterized by an image capturing unit (1) and an image evaluating unit (2), the image capturing unit (1) having all-round optics (6), which detects light from the entire circumference of the cylindrical surface (13) and projects it onto an optical sensor (8, 8 '), the all-round optics (6) and the cylindrical surface (13) being moved relative to one another and after the completion of a predefinable one The partial image of the surface just detected by the sensor (8, 8 ') is stored by the image evaluation unit (2) and all partial images are combined to form an overall image of the surface and the all-round optics (6) and cylindrical surface (13) are continuously moved relative to one another.

2. The method according to claim 1, characterized in that the speed of the relative movement between the all-round optics (6) and the surface (13) is reduced for the duration of the storage of a partial image.

3. The method according to claim 1, characterized in that the speed of the relative movement between the all-round optics (6) and the surface (13) is chosen to be the same throughout.

4. The method according to claim 1, 2 or 3, characterized in that the surface (13) is kept still and the all-round optics (6) is moved relative to the surface (13).

5. The method according to claim 4, characterized in that the optical sensor (8,8 ^' ) is held stationary with respect to the all-round optics (6) and the light detected by the all-round optics (6), preferably using light guides or mirror systems, on the optical sensor (8,8 ') is projected.

6. The method according to claim 4, characterized in that the optical sensor (8,8 ') is rigidly connected to the all-round optics (6) and is moved together with this relative to the surface.

7. The method according to claim 4, characterized in that the all-round optics (6) is held immovably and the surface (13) is moved relative to the all-round optics (6).

8. The method according to any one of the preceding claims, characterized in that the image evaluation unit (2) by comparing the overall surface image with a reference image defects in the surface (13) are recognized.

9. Device for performing the method according to one of claims 1 to 8, characterized by an image acquisition unit (1) and an image evaluation unit (2), wherein the image acquisition unit (1) has all-round optics (6), the light from the entire circumference of the cylindrical surface (13) detected and projected onto an optical sensor (8, 8 '), the all-round optics (6) and cylindrical surface (13) being held movable relative to one another and the optical sensor (8) being a ring sensor.

10. The device for carrying out the method according to one of claims 1 to 8, characterized by an image acquisition unit (1) and an image evaluation unit (2), the image acquisition unit (1) having all-round optics (6) which emit light from the entire circumference of the cylindrical Surface (13) detected and projected onto an optical sensor (8,8 '), the all-round optics (6) and cylindrical surface (13) being held movable relative to one another and the optical sensor (8') being a matrix sensor.

11. The device according to claim 9 or 10, characterized in that the optical sensor (8,8 ') is carried out in CMOS technology.

12. The apparatus of claim 9 or 10, characterized in that the optical sensor (8,8 ') is carried out in CCD technology.

13. Device according to one of claims 9 to 12, characterized in that the all-round optics (6) and optionally the optical sensor (8, 8 ^' ) are fixed on a continuously movable linear drive (4).

14. The apparatus according to claim 13, characterized in that the linear drive (4) is formed by an electrical spindle drive.

15. The apparatus according to claim 14, characterized in that the threaded spindle of the spindle drive is formed by an electrical stepper or servo motor.

16. The apparatus according to claim 13, characterized in that the linear drive (4) is formed by a pneumatic smooth-running cylinder.