EP3004852A1

EP3004852A1 - Method and device for optically inspecting faults

Info

Publication number: EP3004852A1
Application number: EP14735479.9A
Authority: EP
Inventors: Andreas Sandner
Original assignee: Viprotron GmbH
Current assignee: Viprotron GmbH
Priority date: 2013-06-03
Filing date: 2014-06-03
Publication date: 2016-04-13
Also published as: US9766188B2; WO2014195296A1; US20160103081A1; DE102013105693A1

Abstract

The invention relates to a method for optically checking a large-area three-dimensional object (8). An illumination surface (4) of parallel light beams is generated using a light source (1); a large-area three-dimensional object (8) is partly or completely illuminated by the illumination surface (4); and a change of the parallel light beams of the illumination surface (4) through the object (8) is detected, wherein a projection surface (5) is arranged on an object (8) face opposite the light source (1); and the object (8) shadow cast on the projection surface (5) by means of the illumination surface (4) is detected using an optical detection device (7). The strip-shaped light curtain is produced with a Fresnel lens. The shadow is detected using an optical lens system or a CCD camera. The dimensions of the object (8) parallel to the projection surface (5) are ascertained and compared with specified reference values. The projection surface (5) is an opaque panel made of a translucent material or a surface-treated glass pane.

Description

Method and device for optical defect inspection

The invention relates to a method for optical

Error inspection, or inspection of an object, wherein a luminous source, a footprint of parallel light beams is generated, wherein the object of the

Illuminating surface is illuminated at least partially, and wherein a change in the parallel light rays of the illumination surface is detected by the object. Such methods are for example of a

Manufacturer for the optical control of glass panes

used. Another application of such

Test method relates to the control of framed panes and in particular multi-glazed framed panes

Windows during and after their production. In addition to defects within the disk surface serve these

Test method to check the correct positioning of the glass panes relative to the frame elements. With such test methods can be determined whether a

Frame member was fixed at the intended position relative to the glass sheet, or whether an undesirable

Offset of the frame element is present, which goes beyond the usual tolerance limits of a few millimeters and the window element can be unusable.

It is known from practice, optical

Detecting devices with telecentric lenses to use, which have a very large depth of field. With telecentric lenses, edges of

Three-dimensional objects recorded comparatively sharp and dimensions are precisely determined. The size of the objects is however on the diameter of the

telecentric lenses or a front lens arranged therein limited. From a diameter of several centimeters telecentric lenses are due to the high production cost hardly economically useful for the determination of dimensions of three-dimensional objects used.

The dimensions of the glass panes or the window elements are often more than 0.5 m or 1 m and can

especially in one direction 2 m, 3 m or more.

In a method described, for example, in EP 2 108 116 A1, a glass pane is transilluminated by a collimated light curtain, which is generated by a light source. The parallel light rays, which were influenced by the glass pane, are on one of the

Light source opposite side of a

Lens system focused again on an imaging surface and captured by a camera. The maximum area that can be detected at the same time, or the maximum dimension of the

Light curtain is significantly limited by the size and quality of the lens system with which the light curtain of parallel light after the object passage can be focused again on the imaging surface on or in the camera. For large glass panes, the design effort is very high. From EP 1 866 625 A2, a generic method is known in which the parallel light beams are detected and evaluated by a strip-shaped scanner device after passing through a transparent flat object with a side of the object lying opposite one of the light source. suitable

Scanner devices are commercially available and are used, for example, in facsimile transmission equipment or in digital copier systems. A lens system for focusing the transmitted through the object parallel light beams is not required. However, to check a large area object

Usually several strip-like scanner devices are combined and evaluated, for which, inter alia, an exact positioning of the multiple scanner devices relative to each other and to the object is required.

It is therefore regarded as an object of the present invention to develop a method of the type mentioned in such a way that with simple constructive

Means a quick and reliable capture large

Objects is possible.

This object is achieved in that the light rays coming from the footprint are projected onto a projected behind the object projection surface and of the footprint on the

Projection surface generated shadow of the object is detected with an optical detection device.

As a shadow, any impairment or

if necessary slight impairment of the Beam path of coming from the footprint and influenced by the object light rays. The shadow thus contains a complete

Shading by opaque areas of the object as well as a barely visible or undetectable influence on the light rays through, for example, a completely transparent glass.

The shadow cast can be generated by light with wavelengths within the visible light spectrum. However, it is also conceivable and advantageous in some application situations to generate the shadow cast by light with wavelengths outside the visible wavelength range and, for example, to use a light source which predominantly or exclusively infrared light or

emitted ultraviolet light. The projection surface used to image the shadow and the optical detector must be similar to those used for the

Shadow intended wavelength range adapted or suitable for it.

The shadow cast of the object on the projection surface enables cost-effective and reliable detection and verification of the dimensions of a large-area three-dimensional object. In addition, translucent areas of the object can be distinguished from opaque areas. Defects within one

Glass panes that create a shadow can be detected quickly. A lateral offset of

Frame elements of a window element result in a correspondingly shifted or excessively wide

Shadow and can be reliably detected. In particular, with the help of the projection surface

large-scale three-dimensional objects essential

cheaper than with the known from practice

Procedures are reviewed, for example, the

Use of telecentric lenses. As large-scale three-dimensional objects can already be considered objects with dimensions of several centimeters. With suitable components, the projection surface can also be used for large-scale objects such as

For example, glass panes or window elements with

Side lengths of more than one or two meters are reliably and inexpensively checked. To change the dimensions of the object in one direction

It is sufficient to check the shadow cast of the object only in this direction. According to a particularly advantageous embodiment of the

According to the invention, it is provided that the object

is completely scanned. This way you can

For example, the orientation of the object relative to the optical detection means are checked, so that it is not necessary, for example by means of

suitable transport or storage facilities the

To specify the orientation of the object to be checked. Also, operating errors or tolerances in the

Object positioning determined and, if necessary

be compensated. To the largest possible and bright

To provide illumination surface is provided that the footprint is generated with multiple light sources, which are spaced from each other. The plurality of light sources may be arranged in a row or in a matrix. It is also possible to arrange different types of light sources next to one another and to combine them as required.

Preferably, it is provided that a strip-shaped light curtain is generated as a footprint and the object and the strip-shaped light curtain relative

be shifted to each other. For the capture and

Evaluation of the generated on the projection screen

Schattenwurfs is a strip-like scanning of the large-area three-dimensional object and thus a substantially one-dimensional detection and evaluation of the shadow cast particularly advantageous. As a strip-shaped

Sampling, the successive detection of the generated with a strip-shaped light source or footprint shadow strip of the object is considered, the

Footprint relative to the large area object

is shifted to illuminate successively all areas of the object. The linear capture and evaluation of the shadow cast can be done with commercially available optical

Components performed inexpensively and quickly

be evaluated. The light emitted by the one or more light sources may be in the

strip-shaped light curtain are bundled to cause a high contrast of the shadow cast on the screen. When the object and not the light source and the optical detector are moved, the measuring system can optimally arranged and adjusted to allow the most accurate optical measurements possible.

A strip-shaped light curtain can according to a

Embodiment of the inventive concept with a

optionally multi-part Fresnel lens are generated. A Fresnel lens allows comparatively large dimensions with a relatively small thickness of the Fresnel lens. In comparison with lenses made of glass or

Plastic Fresnel lenses allow a large area

Focusing the imitated by the light source light into a bunch of parallel light beams, although the

Fresnel lens only a small thickness and concomitantly has a low weight. A multipart

Fresnel lens can also be made of several side by side

arranged Fresnel lenses or from individual

Fresnel lens segments be composed.

It is preferably provided that the object on the

Luminous surface and the projection surface is moved past. The light source, the Fresnel lens, the projection surface and an optical detection device can be arranged stationary and aligned and adjusted relative to each other, and then to move a large number of objects within a short time through the set-up equipment and thus be able to check. The accuracy of the measurements can be improved. The verification process may be performed during the manufacture of the large-area three-dimensional objects or immediately thereafter at one time and in one place

be carried out, in which the large area

For example, three-dimensional objects within one Production line or moved from a production facility to a storage location and transported.

An inexpensive detection of the shadow cast can be carried out with an optical lens system. In this case, large-area projection surfaces can be detected very quickly and reliably and fed to an evaluation. As an optical lens system, for example, a

commercially available camera lens or a video camera with a digital storage medium or even without a digital storage medium can be used.

A simple verification process that is meaningful and sufficient for many applications at the same time means that dimensions of the object are determined parallel to the projection surface. The determined

Dimensions can be preset with reference values

be compared. The size of the shadow on the projection surface can be determined quickly and reliably with almost any optical detection device. In many cases, based on the dimensions of the object, a first decision can already be made as to whether the object has successfully passed the check or whether an error has been detected, or if applicable, the object of a closer and possibly manual one

Review must be supplied.

Especially with transparent objects such as

Glass panes also make it possible to perform an automated error check. For this purpose, it is provided that irregularities are determined within the object. Unless the irregularities, For example, imperfections, inclusions, bubbles, scratches or streaks a noticeable change in the

Create shadows, these irregularities can be determined and displayed, or fed to a further evaluation. It is also possible to distinguish the detected irregularities according to pre-defined criteria and, depending on the criterion, to do the same

Display information or take action. The invention also relates to a device for optically checking a large-area three-dimensional object. The devices known from practice have a luminous source, a device for generating a

Luminous surface of parallel light beams and an optical detection means for detecting a change in the parallel light rays of the luminous surface by the object.

According to the invention, it is provided that a projection surface is arranged at a distance from the illumination surface, and that the optical detection device is suitable for detecting the shadow cast of the object produced by the illumination surface on the projection surface from an object located in the beam path of the parallel light rays. With the help of the projection surface, the

Shadow of the object to be made visible. Many commercially available optical detectors are capable of detecting the shadow cast on a projection screen. It is therefore not

necessary, with large-sized optical lens systems, the parallel light rays back to a small format Focusing imaging surface or to use large-sized optical detection devices.

The shadow cast of the object on the projection surface can be detected, for example, with a video camera with a digital storage medium. As an optical sensor, for example, a CCD sensor or a CMOS sensor

be used. For a reliable detection of the shadow cast are commercially available cameras or comparable optical lens systems with a

continuously operable image capture suitable.

Of course, an optical detection device may also include a plurality of cameras or a plurality of CCD sensors, or CMOS sensors.

Depending on the imaging properties of the optical lens system used, a large-area projection surface with a linear extension of more than one meter can be detected with a sufficient resolution and with a sufficient contrast to compensate for the

To allow detection and verification of dimensions of the object.

It may be provided and advantageous, in particular, for the detection of large projection surfaces, if the optical detection device consists of several components or imaging imaging devices whose information can subsequently be combined and processed as automated as possible.

By using a digital optical

Detecting device such as a CCD camera or a CMOS camera, further processing and evaluation of the measured raw data becomes particularly easy.

A large-area luminous surface made of parallel light beams can be achieved by using a Fresnel lens, which may have a multi-part design.

In particular, in the case of a strip-shaped luminous area, a long and approximately linear luminous area can be achieved with a comparatively low weight and with a small total thickness of the Fresnel lens.

It is also possible, instead of a Fresnel lens, another equally suitable optical

Focusing device to use. For example, a luminous area of parallel light beams could also be generated by a system of several juxtaposed lenses. Depending on the used

Light source can also be used mirror systems to produce a footprint with parallel light rays.

According to an advantageous embodiment of

According to the invention, it is provided that the

Projection surface an opaque slice of one

translucent material is. The shadow of the object can thereby be detected on a side facing away from the object side of the projection surface, so that the s.der

Projection object moved past the optical

Capture of the shadow on the screen not hindered. At the same time it is made possible that the light source, the means for generating a luminous surface of parallel light beams, the Projection surface and the optical detection device can be arranged along an optical axis, resulting in particularly advantageous geometric conditions for a large-scale scanning and verification of a

give three-dimensional object.

A suitable projection surface may be, for example, a surface-treated glass pane, both

can be produced inexpensively and also has suitable properties for the imaging and detection of the shadow cast by the object.

It is also possible that the projection surface has an opaque film or an opaque sheet.

Suitable films are commercially available, for example, as filter films. An opaque film may be on a low cost transparent substrate such as

For example, be applied polymethylmethacrylate or stretched in a frame.

Hereinafter, an embodiment of the

Invention idea explained in more detail, which is shown by way of example in the drawing. 1 shows a schematic representation of the method according to the invention for the optical inspection of a large-area three-dimensional object,

Figure 2 is an exemplary representation of one for the

Implementation of the method suitable device, Figure 3 is a schematic representation of a differently designed device, which is used to carry out the

Method is suitable, and Figure 4 is a schematic representation of a turn deviating designed device.

In a method shown schematically in Figure 1 for the optical inspection of a large area

Three-dimensional object is generated with a light source 1, a light beam 2 of non-coherent light. With a suitable optical component 3, a footprint 4 of parallel light beams is generated, which on a

Projection surface 5 are directed. The projection surface 5 consists of a translucent pane with a matt surface 6. On an opposite side of the light source 1 of the projection surface 5, an optical detection device 7 is arranged, with an image of the projection surface 5 can be recorded.

The projection surface 5 is illuminated by the illumination surface 4 with parallel light beams. An object 8 located between the illumination surface 4 and the projection surface 5 generates a projection on the projection surface 5

Shadows. The shadow can be with the optical

Detection device 7 detected and evaluated.

When the object 8 is moved transversely to the parallel light beams between the illumination surface 4 and the projection surface 5, the shadow cast by the object 8 on the projection surface 5 changes in a corresponding manner. Through continuous acquisition the shadow cast with the optical detection device 7 can also large-scale objects 8, the dimensions of which are larger than the dimensions of the illumination surface 4 and the projection surface 5, are checked with the arrangement described above.

Based on the size and shape of the shadow cast, which is imaged and detected by the optical detection device 7, it can be checked by comparison with predetermined reference values whether the dimensions of the object 8 are within predetermined tolerance ranges or if the object 8 has deviations from the predetermined reference values that may cause the object 8 to fail the check or, if appropriate, another more in-depth and

if necessary, be subjected to manual verification.

In the example shown in Figure 2

Embodiment, the light generated by the light source 1 from a Fresnel lens 9 in a

strip-shaped footprint 4 of parallel

Converted light rays. The dimensions of the

strip-shaped footprint 4 are given by a strip-shaped aperture 10.

A window element 11 moved between the luminous surface 4 and the projection surface 5 with a glass pane 12 and a frame 13 surrounding the glass pane 12 generates a shadow 14 on the projection surface 5. The dimensions of the shadow cast 14 correspond to FIG

Dimensions of the frame 13 of the window member 11, the is moved between the luminous surface 4 and the projection 5 through. With a CCD camera 15, the shadow cast 14 generated on the projection surface 5 is detected. The raw data recorded by the CCD camera 15 are fed to an evaluation device 16, with the aid of which the dimensions of the shadow cast 14 are determined and determined

predetermined reference values are retrieved from a memory device 17. In the exemplary embodiment in FIG. 3 and schematically

illustrated embodiment of a device according to the invention is generated by the light source 1

Light beam 2 by a lens 3 laterally incident on a mirror 18 directed. The on the mirror 18

incident parallel light beams are arranged in the direction of the spaced apart from the mirror 18

Projection surface 5 reflected. Between the mirror 18 and the projection surface 5, the object 8 can be displaced parallel to the projection surface 5. The one of the

Object 8 generated on the projection surface 5 shadow is detected with the optical detection device 7.

In the schematic in Figure 4 shown

Embodiment of a device designed again deviating from the light source 1 is generated

Light beam 2 is parallelized by the lens 3 and thrown onto a semi-transparent mirror 19. A part of the light beam 2 is in the direction of the mirror 18th

reflected. Through the beam path of the parallel

Light beam 2 from the semi-transparent mirror 19 to the fully reflecting mirror 18 and back, the object 8 as possible parallel to the reflecting mirror 18 are moved. The thereby arranged by the object 8 on the behind the semi-transparent mirror 19

Projection surface 5 generated shadow can be detected by means of the optical detection device 7.

The exemplary embodiments of the device according to the invention described in FIGS. 3 and 4 are particularly suitable in confined spaces. The beam path of the parallel light beam 2 described in FIG. 4 has a double passage through the object 8, so that a shadowing caused, for example, by disturbances in glass surfaces is enhanced and imaged with a higher contrast in the shadow cast on the projection surface 5.

Claims

Patent claims

1. A method for optical defect inspection of an object (8), wherein with a light source (1) a footprint (4) is generated from parallel light rays, wherein the object (8) of the footprint (4) at least

wherein a change in the parallel light beams of the illumination surface (4) is detected by the object (8), characterized in that the light rays coming from the illumination surface (4) are projected onto a projection surface (5) arranged behind the object (8). be projected and of the illumination surface (4) on the projection surface (5) generated shadow (14) of the object (8) with an optical detection means (7, 15) is detected.

2. The method according to claim 1, characterized in that the object (8) is a large-area three-dimensional object (8) with a shading area of more than 0.25 m ² .

3. The method according to claim 1 or claim 2, characterized in that the object (8) is completely illuminated.

4. The method according to any one of the preceding claims, characterized in that the Ausleuchtfläche (4) spaced from parallel light beams with a plurality

to each other arranged light sources (1) is generated.

5. The method according to any one of the preceding claims, characterized in that a strip-shaped

Light curtain generated as a footprint (4) and the object (8) and the strip-shaped light curtain are displaced relative to each other.

6. The method according to any one of the preceding claims, characterized in that the strip-shaped

Light curtain with an optionally multi-part

Fresnel lens (9) is generated.

7. The method according to any one of the preceding claims, characterized in that the object (8) on the

Illuminated surface (4) and the projection surface (5)

is moved past.

8. The method according to any one of the preceding claims 1 to

6, characterized in that the illuminating surface (4) and the projection surface (5) and possibly also the detection device (7, 15) on the object (8)

be moved past.

9. The method according to any one of the preceding claims, characterized in that the shadow (14) is detected with an optical lens system.

10. The method according to any one of the preceding claims, characterized in that dimensions of the object (8) are determined parallel to the projection surface (5).

11. The method according to claim 10, characterized in that the determined dimensions of the object (8) are compared with predetermined reference values.

12. The method according to any one of the preceding claims, characterized in that irregularities within the object (8) are determined.

13. A device for optical inspection of an object (8), with a light source (1), with a device for generating a footprint (4) of parallel

Light rays, and with an optical

Detection device (7, 15) for detecting a

Change in from the footprint (4) coming

Light rays through the object (8), characterized in that spaced from the footprint (4) a

Projection surface (5) is arranged and the optical

Detection device (7) is adapted to that of the footprint (4) on the projection surface (5) of one in the beam path of the parallel light beams

located object (8) generated shadows (14) to capture.

14. The device according to claim 13, characterized in that it is in the object (8) is a large-scale three-dimensional object (8) having a shading area of more than 0.25 m ² .

15. The apparatus of claim 13 or claim 14, characterized in that the means for generating a

Luminous surface has an optionally multi-part Fresnel lens (9).

16. Device according to one of claims 13 to 15, characterized in that the means for generating a luminous area a system of several side by side

arranged lenses or a system of multiple mirrors.

17. Device according to one of claims 13 to 16, characterized in that the optical detection device (7) comprises an optical lens system.

18. The device according to claim 17, characterized in that the optical detection device (7, 15) has at least one camera with a digital storage medium or without a digital storage medium.

19. The apparatus of claim 17 or claim 18, characterized in that the optical detection means at least one CCD sensor or a CMOS sensor

having.

20. Device according to one of claims 13 to 19, characterized in that the optical detection means (7, 15) of a plurality of components, or imaging

Image capture devices consists

21. Device according to one of claims 13 to 20, characterized in that the projection surface (5) is an opaque disc of a translucent material.

22. The apparatus according to claim 21, characterized in that the projection surface (5) is a surface-treated glass sheet.

23. Device according to one of claims 13 to 22, characterized in that the projection surface (5) has an opaque film or an opaque sheet.

24. Device according to one of claims 13 to 23, characterized in that the device is one with the optical

Detection device (7, 15) connected

Evaluation device (16) for determining dimensions of the object (8) and irregularities within the

Object (8).

25. The apparatus according to claim 24, characterized in that the evaluation device (16) is data-transmitting connected to a memory device (17), in the

Reference values are stored.