DE19726967C1 - Optical imaging device for O-ring seal - Google Patents

Abstract

The optical imaging device has a light deflection device (15,24) at a relative spacing from the examined object (12), with inner and outer reflection surfaces, for reflecting incident light rays parallel to the optical axis (14) from the inner reflection surface to the outer reflection surface, directing the light onto the object peripheral surface at an acute angle. The outer reflection surface is provided by an elongate hollow body with a round or polygonal cross-section. An Independent claim is also included for an application of an imaging device for imaging the inner and/or outer surfaces of an O-ring seal onto the image plane of a photosensor.

Description

The invention relates to a device for optical Mapping the peripheral side surface of an object arranged on a receiving surface onto a Image plane of a light-sensitive receiver according to the Preamble of claim 1. Such Device is known from DE 30 35 082 A1. There will a device for optically imaging the outside of a bottle mouth of a standing bottle on one described photosensitive receiver.

Furthermore, it is known from DE 31 09 270 A1 circumferential side surface of a bottle mouth with a to capture internally mirrored tube. In DE 42 09 417 C2 becomes an optical test device for internal threads described in which an acute-angled conical mirror in the Threaded hole is inserted to the inner surfaces to project a camera arranged coaxially to it. The DE-OS 25 05 063 discloses the use of a pyramidal mirror for testing Photo mask defects. Through the individual mirror segments become several photosensitive receivers at the same time exposed.

In the course of the ever increasing demands on the Product quality requires a comprehensive Check the individual parts before installing them perform. In addition to the Checking the dimensions often includes checking the Surface texture. Especially at  Sealing rings, for example O-rings, are essential on the nature of the surface, as there are imperfections Seal failure even with exact dimensions being able to lead.

It is obvious that a grasp of the whole The surface of an object causes problems because of the Object must be viewed from all sides. Especially with the automatic control of Bulk products require that Handling and testing itself in a very short time done in order to make economic sense. For this Reason are such examination procedures disadvantageous in which complicated handling of the object is required is. Basically, it would be useful and desirable if the object is lying on the receiving surface optically could be detected.

It is known for example from US 4,634,273, an O-ring on a transparent mounting surface to move relative to a camera to the whole To be able to scan the circumferential surface. It is obvious, that this takes a very long time to complete 100% inspection of such a mass product in principle is not available.

Of course, it is also possible that a large number is provided by photosensitive receivers, the Capture an object from different angles. On then the individual photosensitive receivers for example, the top surface and sections of the side surfaces. However, it is obvious that such a device very is complex. Furthermore, the multitude of  photosensitive receiver a relatively high Space required so that the installation of a test device in Production facilities or the like very difficult or is not possible at all. Another disadvantage is in it to see that the evaluation of several images also at fast working data processing systems relative is time consuming. It is also possible to use the circumferential Side surface through only one mirror to the image plane project. However, this enlarges the object, so that a correspondingly large sensor is required. However, there are limitations in the resolving power connected.

The invention has for its object an optical Device of the type described above so different train that the side surface also one on one Recording area lying object essentially can be detected without distortion.

The object is achieved according to the invention in that the object lies on the receiving surface that the external reflection surface an elongated hollow body with a round or polygonal cross section and that Angle on the inner reflection surface is acute. It has been shown to be such Light beam deflection device is possible, the rotating Side surface of the lying on the receiving surface Object to grasp well and on the image plane of the photosensitive receiver essentially reproduce without distortion.

It can be provided, for example, that the external reflection surface of a lateral surface of a coaxial with the optical axis and the cylinder  internal reflection surface of a lateral surface of a Cone or a truncated cone. This is especially for the illustration of a round object, like an O-ring, advantageous. The side face of the O- Ring appears as a closed circular ring Image on the image plane. With such a round Formation of the reflective surfaces is only towards it take care that in certain areas an astigmatism occurs.

But it can also be provided that the outside Reflective surface of a lateral surface of a coaxial and elongated parallel to the optical axis Hollow body with a polygonal cross section and the internal reflection surface of a lateral surface of a Pyramid or a truncated pyramid, whose or the base area of the cross section of the outside Reflecting surface corresponds. By providing one polygonal cross section, for example an octagon  or hexagons, can be an object with a round outline are also mapped approximately well. Appear then several areas of the side surface several times on the Image plane. However, this bothers the test and Evaluation method not, since only the Check the surface quality.

Basically, it can be useful if in cross section perpendicular to the optical axis the contours of the internal and external reflection surfaces to the Contour of the object to be imaged are adjusted. It can be provided, for example, that the Acquisition area towards open angles between the optical Axis and the internal reflection surface between 15 ° and 30 °, preferably 22.5 ° and that the external reflection surface parallel to the optical axis runs so that the viewing angle of the front edge 30 ° is up to 60 ° or 45 °. Such training has further the advantage that the side surface regardless of the Size of the diameter of the object is always about same area of the image plane, d. H. with always about that same diameter, is shown. This allows the Evaluation of the image of the light-sensitive receiver this area will be limited so that the too processing data volume is kept low.

According to a preferred embodiment of the invention provided that the light beam deflecting device from a cylindrical or polygonal prism body formed is, the outer reflection surface the totally reflecting outer interface of the prism body is and the internal reflection surface through the totally reflecting interface of one with the receiving surface open conical or frustoconical or polygonal pyramid or truncated pyramid Recess of the prism body is formed. Through this Training is achieved that the inside Reflecting surface exactly coaxial to the outside  Reflection surface runs. This is particularly the case with circular cross sections required. Another advantage can be seen in the fact that no holding elements that the internal reflection surface in the external Keep reflection surface, are needed. Another The advantage is that the inner interfaces are insensitive to contamination, so that only the light entry surface and the light exit surface must be kept clean.

Furthermore, it can be provided that the recess in the a portion of the area facing the receiving surface has, its interface, in longitudinal section parallel to optical axis, substantially perpendicular to the Viewing direction of the side view runs. Thereby is achieved that the light rays the corresponding Cross the interface vertically so that there are no distractions and influences occur.

The prism body can be made of glass, acrylic, for example Polymethacrylates or a polycarbonate exist. The Surfaces can be sleeked or, if possible, be polished. Furthermore, anti-reflective layers can be applied to the optically effective surfaces can be applied. Further can be provided that the prism body several elements, for example disks at im Cross section of circular reflection surfaces and sectors polygonal reflection surfaces in cross-section.

Such optical test equipment is often used in automatically operating production lines. It it is necessary for the optics to be tested Objects is adjusted. Here it will be necessary the distance of the light beam deflection device in Dependence on the thickness and the external dimension, for example the cord size and the diameter of a O-ring. Because of the redirection optical path length when the  Light beam deflection device extended or shortened, see above that for a sharp image readjustment of the optics is required.

According to an advantageous development of the invention, adjusting means are provided which Distance of the light beam deflection device to the object change, the actuating means using a gearbox a holder of the optical receiver in such a way cooperate that the optical path length between the Side surface of the object to the image plane essentially remains constant. This has the advantage that the lens of the not to be adjusted by the light-sensitive receiver needs.

The changes depending on the viewing angle required adjustment of the distance of the photosensitive receiver to the receiving surface. Basically, it should be noted that with a reduction the distance of the light beam deflection device Increase the distance of the photosensitive Receiver must be set to the receiving surface.

It is therefore provided according to an advantageous development of the invention that Transmission has a gear ratio that the Condition h = -a (1 / sinα - 1) is sufficient, where h is the stroke of the photosensitive receiver, a the adjustment of the Distance of the light beam deflecting device Recording area and α is the viewing angle. The the opposite sign is supposed to be the opposite movements clarify. The gearbox can be two, for example counter-rotating threaded spindles with different Have slopes.

It is obvious that through such Beam deflecting an object both at least partially from above as well as at least partially can be mapped from the side onto an image plane. In particular, it is possible that the peripheral surface  of an annular object through the oblique view can be mapped well.

The device according to the invention is also suitable for Imaging the inner and / or the outer peripheral surface of an O-ring on the image plane of a photosensitive Recipient. The light beam deflection device is in accordance with an advantageous development adjusted according to the dimensions of the O-ring that the outer peripheral surface and at least part of top surface is sharply imaged. In another The position along the production line becomes the Light beam deflecting device according to an advantageous development set so that the inner Circumferential surface of the O-ring and at least part of the top surface is sharply imaged on the image plane. Since the O-ring is circular, in the Usually only the upper half of the circumferential surface is shown can be. For smaller O-rings, the Beam deflecting device both the inner and the outer lateral peripheral surface with sufficient sharpness are displayed simultaneously on the image plane. The O- Ring then appears twice on the image plane.

The O-ring can then be turned around, for example depict the lower half of the peripheral surfaces.

The invention is shown in the schematic below Drawing explained in more detail using embodiments. Show it:

Fig. 1, an optical test apparatus with a Lichtstrahlumlenkeinrichtung according to the invention,

Fig. 2 a sectional Lichtstrahlumlenkeinrichtung according to the invention,

Fig. 3 shows the top view of the Lichtstrahlumlenk device according to Fig. 2,

Fig. 4 in section a light beam deflecting device according to another embodiment of the invention and

Fig. 5 shows the top view of the Lichtstrahlumlenk device of FIG. 4.

The optical test device shown in the drawing for checking the circumferential side surface of O-rings has a receiving surface 11 on which an O-ring 12 lies with its flat side. The receiving surface can for example be part of a conveyor belt that runs continuously or clocked. Instead of an O-ring 12 , another essentially flat object, for example a sealing washer or the like, can be checked with the device.

Above the support surface 11, a light-sensitive receiver 13 is arranged whose optical axis 14 is perpendicular to the pickup surface. 11 The object 12 is aligned symmetrically, preferably coaxially to the optical axis 14 . The light-sensitive receiver can be a CCD camera. In principle, other orientations of the optical axis to the receiving surface are also possible. This can be particularly useful if an asymmetrical object is to be checked.

In the light beam path between the photosensitive receiver 13 and the receiving surface 11 there is a light beam deflecting device 15 , 24 at a relatively short distance above the O-ring 12. The light beam deflecting device 15 is aligned essentially coaxially with the optical axis 14 and has a mutually facing inner and outer reflection surface 16 and 17 respectively. The inner and outer reflection surfaces 16 and 17 are also aligned coaxially with the optical axis 14 . As a result, an essentially annular light passage 19, which is also coaxial with the optical axis, is formed.

The optical axis 14 of the light-sensitive receiver runs at least in the area of the object and the light beam deflecting device perpendicularly and in a straight line to the receiving surface 11. In the embodiment shown in the drawing, the optical axis between the receiving surface 11 and the light-sensitive receiver 13 runs completely straight. However, it is of course possible that the optical axis above the light beam deflection device 15 , 25 can be pivoted by mirror elements, for example by 90 °.

In detail, the arrangement in the exemplary embodiment of the light beam deflection device 15 shown in FIG. 2 is such that the outer reflection surface 17 has a course corresponding to a cylindrical lateral surface and extends parallel and coaxially to the optical axis 14 . The inner reflection surface 16 corresponds to an outer surface of a truncated cone, the larger end 18 of which points towards the object and the central axis of which coincides with the optical axis 14 . As can be seen from the beam path shown, light rays 20 running parallel to the optical axis are deflected on the inner reflection surface 16 in the direction of the outer reflection surface and are reflected there under the viewing angle α onto the upper section of the side surface 21 of the O-ring.

The light beam deflection device 15 consists of a cylindrical prism body. The outer reflection surface 17 is formed by the totally reflecting outer boundary surface of the prism. The inner reflection surface 16 is formed by the inner boundary surface of a truncated cone-shaped recess 23 of the prism. In the embodiment shown in the drawing, the opening angle of the cone is 45 °, and accordingly the internal reflection surface 16 extends at an acute angle β of 22.5 ° to the optical axis 14 , which is open towards the receptacle. The viewing angle α is accordingly 45 ° . A recess 22 with a greater inclination adjoins the lower region 18 of the truncated cone, the boundary surface of which runs perpendicular to the viewing direction. The light rays are not hindered or deflected at its interface.

With such a light beam deflection device, it is possible to image the peripheral side surface of a flat, round object 12 in a ring shape on the image plane of the light-sensitive receiver 13 . The side surface is completely imaged so that a test can be carried out with only one light-sensitive receiver camera. In the case of an object with a curved front edge, such as an O-ring, usually only the upper half facing the image plane can be imaged well. The lower half would have to be checked after rotating the object by 180 °.

Another embodiment of a light beam deflection device 24 is shown in FIG. 4. The outer and inner reflection surfaces 25 , 26 have a multiplicity of flat surface sections 29 which are polygonal in cross section perpendicular to the optical axis 14 . The outer reflection surface 25 now corresponds to a lateral surface of a tube running parallel to the optical axis with a polygonal, here octagonal, cross section. The inner reflection surface 26 has a course which corresponds to the lateral surface of a pyramid or a truncated pyramid, but whose base surface is polygonal, here octagonal, and whose central axis coincides with the optical axis 14 . The individual surface sections 29 of the inner and outer reflection surfaces are arranged symmetrically and coaxially with one another. Here, the peripheral side surface 21 of the O-ring is imaged in the form of a polygon on the image plane of the light-sensitive receiver. Astigmatism is not expected in this embodiment.

In this embodiment too, the light beam deflection device consists in one piece of a prism body which is provided with a corresponding recess 27 which is open at the bottom. An enlarged section 28 with a greater inclination is also provided. The outer reflection surface 25 is formed by the outer boundary surface and the inner reflection surface by the boundary surface of the prism body created by the recess 27 . The light beam path in longitudinal section corresponds to that of the embodiment according to FIG. 2.

In the illustrated in Fig. 4 the light beam path, only the outer peripheral side surface and the upper surface of the O-ring is shown. In the light beam path shown in FIG. 2 for a relatively small object with respect to the light beam deflection device, both the inner and the outer lateral peripheral surface are imaged. The O-ring then appears twice on the image plane. The distance between the receiving surface and the light beam deflection device and thus the area of the detected surface results from the beam path between the reflection surfaces. Furthermore, the diameter of the light beam deflection device and that of the object is decisive.

Above is predominantly conical and cylindrical or polygonal pyramidal or tubular Reflective surfaces. Of course it is possible that these reflective surfaces also one in relation have a curve curved on the optical axis, in order to for example, to prevent or to prevent astigmatism minimize.  

As a rule, such a light beam deflecting device 15 , 24 can only detect and sharply image a relatively narrow area. It will therefore often be necessary for the distance of the light beam deflection device 15 , 24 to the receiving surface or to the object to be set as a function of its diameter and thickness. Because of the beam path, a change in the distance also causes a change in the optical path length to the image plane, so that the position of the light-sensitive receiver, ie its distance from the receiving surface, must be changed for a sharp image. Specifically, the distance must be set according to the condition h = -a (1 / sinα - 1), where h is the stroke of the light-sensitive receiver, a is the adjustment of the distance of the light beam deflecting device to the receiving surface and α is the viewing angle. Of course, it is also possible to adjust the lens of the light-sensitive receiver accordingly.

Since the displacement of the light-sensitive receiver 13 relative to the receiving surface and the change in the distance of the light beam deflection device 15 , 24 are always in a fixed relationship to one another, these movements can be coupled. In the embodiment shown in the drawing, the light beam deflection device 15 , 24 is held in a linear guide 30 so as to be displaceable via a spindle 31 . The light-sensitive receiver 13 is also slidably held on a linear guide 32 via a spindle 33 . Both the spindles 31 and 33 and the linear guides 30 , 32 can be formed in one piece. The spindles are non-rotatably connected and have opposite threads with different pitches. This has the effect that when the light beam deflecting device 15 , 24 is lowered, the light-sensitive receiver is raised in accordance with the condition h = -a (1 / sinα-1). This makes it possible to effect an exact adjustment with only one motor 34 .

In the drawing there is only one optical test device shown. It is of course also possible to have two side by side to couple the horizontal test device together. The respective spindles can rotate on a belt be connected so that four movements with only an engine can be effected. Then this can be useful if both the inner and the outer Circumferential surface must be checked. If the Diameter is the one optical test device on the inner and at the same time the other test device on the outer circumferential surface of the O-ring with only one motor set. A complex adjustment of the test device to check another object with different dimensions can therefore be omitted.

The light beam deflection device is in one Distance to the receiving surface, which is larger than the thickness or the amount of the object to be checked. It is therefore possible that the receiving surface part of a conveyor belt is on which the objects are transported. It there is no obstruction to the movement, so that a Check for continuous or clocked movement of the Conveyor belt is possible.  

Reference list

11

Receiving area

12th

O-ring

13

photosensitive receiver

14

optical axis

15

Beam deflecting device

16

internal reflection surface

17th

external reflection surface

18th

lower area

19th

Passage of light

20th

Beam of light

21

Side surface

22

Recess

23

Recess

24th

Beam deflecting device

25th

external reflection surface

26

internal reflection surface

27

Recess

28

Recess

29

Surface sections

30th

Linear guide

31

spindle

32

Linear guide

33

spindle

34

engine
α Viewing angle
β angle

Claims (14)

1. Device for optically imaging the peripheral side surface ( 21 ) of an object ( 12 ) arranged on a receiving surface ( 11 ) on an image plane of a light-sensitive receiver ( 13 ), with a light beam deflection device ( 15 , 24 ) arranged at a distance above the object and which has at least one mutually facing inner ( 16 , 26 ) and outer ( 17 , 25 ) reflection surface, which outer reflection surface ( 17 , 25 ) extends rotationally symmetrically about the optical axis ( 14 ) of the light-sensitive receiver ( 13 ) and which surrounds the inner reflection surface ( 16 , 26 ) coaxially while leaving a light passage ( 19 ), the inner reflection surface having a cross section corresponding to the outer reflection surface perpendicular to the optical axis ( 14 ) and at an angle (β) to the optical axis (open) towards the receiving surface ( 14 ) runs so that parallel to optical axis ( 14 ) extending light rays are deflected from the inner reflection surface to the outer reflection surface and are reflected there with an acute viewing angle (α) on the surrounding side surface, characterized in that the object lies on the receiving surface, that the outer reflection surface is an elongated hollow body with a round or polygonal cross-section and that the angle (β) on the inner reflection surface is acute. 2. Device according to claim 1, characterized in that the outer reflection surface ( 17 ) corresponds to a lateral surface of a coaxial to the optical axis ( 14 ) extending cylinder and the inner reflection surface ( 16 ) corresponds to a lateral surface of a cone or a truncated cone. 3. Apparatus according to claim 1, characterized in that the outer reflection surface ( 25 ) of an outer surface of a coaxial and parallel to the optical axis ( 14 ) extending elongated hollow body with a polygonal cross section and the inner reflection surface ( 26 ) corresponds to an outer surface of a pyramid or truncated pyramid whose base corresponds to the cross section of the outer reflection surface. 4. Device according to one of claims 1 to 3, characterized characterized in that the outer reflection surface has a clear dimension that is larger than the outer dimension of the Object is. 5. Device according to one of claims 1 to 4, characterized in that the contours of the inner and outer reflection surfaces are adapted to the contour of the object to be imaged in cross section perpendicular to the optical axis ( 14 ). 6. Device according to one of claims 1 to 5, characterized in that the angle towards the receiving surface open between the optical axis ( 14 ) and the inner reflection surface between 15 ° and 30 °, preferably 22.5 ° and that the outer reflection surface runs parallel to the optical axis, so that the viewing angle of the front edge is 30 ° to 60 ° or 45 °. 7. Device according to one of claims 1 to 6, characterized in that the light beam deflecting device is formed in one piece from a cylindrical or polygonal prism body, the outer reflection surface being the totally reflecting outer boundary surface of the prism body and the inner reflection surface through the totally reflecting boundary surface one of the receiving surface open conical or frustoconical or polygonal pyramid or truncated pyramid-shaped recess ( 23 , 27 ) of the prism body is formed. 8. The device according to claim 7, characterized in that the recess in the area facing the receiving surface has a section ( 19 , 28 ) whose interface, in longitudinal section parallel to the optical axis, is substantially perpendicular to the viewing direction of the side view. 9. Device according to one of claims 1 to 8, characterized in that the distance between the receiving surface ( 11 ) and the light beam deflecting device ( 15 , 24 ) is greater than the thickness or height of the object to be tested ( 12 ). 10. Device according to one of claims 1 to 9, characterized in that adjusting means ( 34 ) are provided which change the distance of the light beam deflecting device ( 15 , 24 ) to the object, the adjusting means via a gear ( 31 , 33 ) with a holder of the optical receiver ( 13 ) cooperate in such a way that the optical path length between the side surface of the object and the image plane remains essentially constant. 11. The device according to claim 10, characterized in that the transmission ( 31 , 32 ) has a transmission ratio which satisfies the condition h = -a (1 / sinα - 1), where h is the stroke of the light-sensitive receiver ( 13 ), a the adjustment of the distance of the light beam deflecting device to the receiving surface and α, the viewing angle. 12. The apparatus according to claim 11, characterized in that the transmission comprises two interacting spindle sections ( 31 , 33 ) which have opposite threads with different pitches. 13. Device according to one of claims 9 to 12, characterized characterized in that at least two photosensitive  Receiver and two light beam deflection devices via one Gearbox interact in this way. 14. Use of a device according to one or more of the preceding claims for mapping the inner and / or the outer peripheral surface of an O-ring on the Image plane of a light-sensitive receiver.