DE102009013088A1 - Method for measuring and evaluating label image quality of label image of object, involves adjusting target label image in form of vector graphic for provision - Google Patents

Abstract

The method involves adjusting the target label image in form of a vector graphic for provision. The target label image is minimized with a unit of image processing technique and with predetermined evaluation method of dimension and thickness techniques in a consistence with the adjusted label image. An independent claim is also included for a measuring device for the execution of the method.

Description

The The invention relates to a method for measuring and evaluating a label image quality a label on an object according to the generic term of claim 1 and a measuring device for implementation the method according to the preamble of claim 14.

In In manufacturing, it is known objects, such as Plastic parts, for example, in the color, in the form, in the base material or additive additives to the base material differ, for example in type or in terms of Working wavelength or working lens different Mark labeling systems, such as laser marking machines or to label.

By the meeting of different types of plastic to here but also at later points, for example in plastic parts to stay, and different writing system relate on the quality of the label on the concerned Plastic part on different results.

For example has the lettering quality on a plastic part A, for example, marked with a lettering B or has been labeled, a higher degree of contrast to Underground or a finer font width, as if this plastic part, for example, with a labeling C would have been marked or labeled.

Further it is known before a release of the mark or Labeling of a aforementioned marked respectively inscribed plastic part, the marking or lettering alone with the human eyes in different light conditions to rate. The evaluation criterion is the general overall impression the marking or label used. The overall impression is to a large extent subjective Perception and evaluation of the contrast by the examiner People dependent.

In Typically, the lettering quality is sufficient when the marking or lettering in daylight too good recognize or read.

Often the label quality is rated by people who also responsible for a quantity to be produced are. Here there is a danger that, for example, objectively not more sufficiently good picture quality under one Cost point of view subjectively still rated as sufficiently good become.

Furthermore Quality controls are often only used as spot checks executed. For example, it will only be at a batch change controlled or only when changing the label itself.

quality checks the label image are small batches with changing label images correspondingly more necessary.

Because of Subjectivity of the evaluation method differs Evaluation results not only within the examination of a Batch with consistent label image, but also between the evaluation results of the tests of batches with different label image. In particular, the evaluation results differ between successive consecutive batches with the same Label images between those batches with other label images are inserted.

Around with respect to a respective batch with, for example, laser-marked Plastic parts an at least satisfactory lettering quality To obtain it, it is known, only some sample parts with the appropriate To create a label image and the lettering image by a human Visual inspection to control. Only when the desired Result, the production of the batch is started.

adversely but is still that the rating of the label subjectively is, that is, the subjective overall impression of the human examiner depends. Another disadvantage is that the examining Person subject to external influences can and then judge depending on your condition.

For an objective measurement and rating of the label quality of a lettering picture on a subject object are lighting means for Illuminate the label image, a camera system for recording the illuminated lettering image and an electronic calculation system with a cooperating image processing technique for measuring and rating the label image quality of the label image necessary on the basis of what was taken.

From the document US-A-5,859,923 and from International Conference on Technical Diagnostics, 10th IMEKO TC10, 9-10 June, 2005, Budapest, Hungary, pp: 99-102, High-speed Label Inspection System for Textile Industry, István Szatmari and Ákos Zarándy are known measuring methods and measuring devices that use a camera system with illumination and thus a test object with a ausge chose to compare error-free preset. In detail, artificial neural networks are used for a good / bad classification. There is no picture of the subjective perception of quality. In addition, these systems undergo a complex training phase for each new examinee.

From the document US-A-5,969,374 With respect to laser marking of semiconductor disks, it is known to perform only a contrast evaluation based on a comparison with a gray scale card. This is made possible by the use of a camera system with associated illumination, which is typical for optical inspection systems.

From the document US-A-5,837,983 a software system is known, which determines the quality of a respective label image due to statistical analysis of the recognition rate when reading an underlying label or an associated bar code by a text recognition software, a so-called OCR software. The OCR software recognizes the existing text in the image and compares it with an expected text. Such a system is not based on a subjective perception. The success of such a system depends on the performance of the OCR software.

task The present invention is based on a method of the type mentioned at the outset to improve this method in such a way that that thus a picture of a mean subjective perception of quality in relevant label images by objective measurement or with objective measured values is possible. It's up to you to continue of the present invention, starting from a measuring device of the type mentioned, this measuring device in the way technically to improve that so that the implementation of the invention Method is possible.

In terms of of the method, this object is achieved by a method, that specified in the characterizing part of claim 1 process steps having.

After that A target label image in the form of a vector graphic is available posed. The Sollbeschriftbild is using the means of image processing technology and with given calculation methods dimensional and positional technical in a correspondence with the recorded label image brought. Thereafter, in each case based on the Sollriftriftbild from the label at least one of several possible Attributes with an associated individual rating determined. These attributes include completeness, the contrast to the ground, the edge width and the homogeneity respectively of the label. From the existing determined attributes with associated individual ratings then becomes an overall rating determined, wherein in the presence of several determined attributes with associated attribute evaluations Weighting carried out according to empirical findings becomes.

In terms of The measuring device is this task by a measuring device solved, the specified in the characterizing part of claim 14 features having.

After that the measuring device has in particular a dome with a Base in a base plane spanned by the base, with a base plane base area bounded by the base near the base level, with a vertex above the central region, with an inner surface, with a lighting system that is on the one hand parallel to the base plane to the base plane and on the other hand along the inner surface along evenly distributed around a circumference of the dome with a light emission on the inner surface of the dome is arranged with a shutter between the lighting system and the central area for shadowing the central area of the Light emission of the illumination system, with a camera system in the apex of the dome, looking towards the central area, and with a pedestal that can be arranged in the middle section for one Subject with a positionable below the camera system Beschriftbild.

The inventive measures have the Advantages that to be carried out in the prior art Training phase by the specification of a vector graphic of the label image is automated and that with these measures an intelligent and automatic test plan creation is possible.

Though have the inventive measures also a contrast rating over the comparison with a Graystone card integrated, as in the prior art, however, takes place the valuation based on another calculation and assessment rule, which is adapted to the picture of subjective perception.

At the inventive method is in contrast to the known methods a complex, multi-dimensional feature space used simultaneously with a contrast component, a homogeneity component, include a completeness component and a font / edge width component can. A specific weighting is taken into account, based on empirical findings. The empirical findings are based on investigation of subjective quality perceptions.

Although the basic structure of the measuring device according to the invention is similar to the measuring device, in particular from the document US-A-5,969,374 However, this is known only to the extent that a camera system and a lighting system are used per se. The optical test system according to the invention differs fundamentally from the fact that an indirect and homogeneous illumination is used, by which a significant improvement in the lighting conditions is achieved.

With the inventive method and the inventive Measuring device for carrying out the inventive Procedure is for the first time an actual objectification and standardization of the so far subjective quality assessment process possible through objective measurements.

there Being a high flexibility by using a Vector graphic as target mark image achieved. It is not a learning time for new labels and they are not sentences of test and comparison images necessary.

The inventive measures provide a high repeatability and comparative precision for sure.

she are easy to use in a production line because only the components need to be removed, the manual support, the ergonomics or the Serve transportability.

advantageous Embodiments of the invention are the subject of dependent claims.

The advantageous embodiments of the subjects of the dependent claims are such that, in particular, an objective assessment of lasered label images especially on different plastic parts performed using different labeling systems can be, with an ergonomic and simple manual Operation, wherein the measuring device can be built so that she is also transportable.

following is an embodiment of the invention Method and the measuring device according to the invention explained in more detail with reference to a drawing. In this demonstrate:

1 a schematic representation of the measuring device according to the invention,

2 an inside view of a device with a measuring device according to 1 , and

3 a whole plant with a device after 2 ,

In the 1 are the core components of the measuring device according to the invention to see. In particular, in the 1 to see the principle of indirect, homogeneous lighting.

In detail is in the 1 a dome 1 to see who a base 2 has, in turn, in through the base 2 spanned base level 3 is arranged.

The dome 1 has a covered central area 4 up, from the base 2 is bounded and located near the base level 3 located. Furthermore, the dome points 1 a dome vertex 5 and a dome inner surface 6 on.

In the dome 1 is a lighting system 7 arranged in such a way that it is in close proximity to a base inner edge 8th located in such a way that it is an existing extent of the dome 1 around with an even distribution of bulbs 9 for uniform illumination of the dome inner surface 6 is arranged.

In the dome 1 is further between the lighting system 7 and the middle area 4 for a light shading of the middle area 4 below the dome vertex 5 when illuminating the dome inner surface 6 through the lighting system 7 a panel 10 arranged.

In the dome vertex 5 is a camera system 11 provided in the dome vertex 5 with a view towards the shaded middle area 4 is arranged.

In the shaded middle area 4 is a carrier part 12 for an object 13 with one in the shaded middle area 4 under the camera system 11 to lie next picture 14 ,

The dome ( 1 ) is in the 1 a hemisphere. But it can also be used other dome-shaped forms. For example, cylinder, tunnel, cube or cuboid shapes could be used.

Through the aperture 10 This will prevent that from the bulbs 9 to the dome inner surface 6 emitted light also on the object to be tested and on his scribed image 14 falls, but indirectly over the dome inner surface 6 is reflected. This ensures high homogeneity in the lighting. In addition, the measuring device is independent of environmental influences.

The measuring device according to the 1 he allows a homogeneous illumination and an exact positioning of the object to be tested 13 , which ensures a high repeatability and comparison precision.

For a high homogeneity in the lighting effect of the lighting system 7 carries a dome inner surface 6 at, which is uniformly reflective light formed.

In a concrete embodiment, the illumination means 9 of the lighting system 7 at least substantially formed with a circular fluorescent lamp.

In another advantageous embodiment of the measuring device according to the invention, the dome vertex 5 an opening 15 in the dome 1 in which at least partially the camera system 11 is placeable. In this way, the measuring device can be realized even more compact.

To perform a measurement is either the dome 1 alone opposite the carrier part 12 , the carrier part 12 alone opposite the dome 1 or both each opposite each other along a common central central axis 16 held displaceable.

For this sliding holding is a sliding bracket 20 ( 2 or 3 ) between the dome 1 and the carrier part 12 Installed.

To assist in the positioning of the object to be tested 13 with the label to be tested 14 during a measurement procedure can within the dome 1 at least a single point laser 17 with beam direction 18 to an end position 19 for a camera system 11 to lie next lettering 14 be arranged. The arrangement is the point laser 17 provided in the way that with the point lasers 17 with respect to a given point 21 within one below the camera system 11 to lie next lettering 14 a so-called triangulation is to accomplish.

In the present embodiment is a triangulation with an angle of 45 degrees to the central center axis 16 accomplished.

In the 2 is a concrete device 22 with a measuring device according to the 1 shown.

In the 3 is a complete measuring station with the help of a device 22 according to the 2 shown.

For a measurement procedure, the dome is used for height positioning 1 about the object to be tested 13 with the label to be tested 14 hazards. For this purpose, the device shown 22 externally attached corresponding control buttons 23 Installed.

The Indian 3 shown complete measuring station comprises in the present embodiment next to the device 22 an electronic calculation system 24 with associated controls 25 , wherein the electronic calculation system 24 via a corresponding cable connection 26 with the device 23 is connected for a suitable data exchange between the relevant components. The electronic calculation unit includes, among other things, means of image processing technology.

The height positioning can be done with the help of such a measuring station via appropriate software methods. The height of the camera system 11 The object to be tested is triangulated by a point laser at an angle of 45 ° 17 certainly. This is done, for example, in a display 27 of the measuring program the target point of the point laser 17 appears. Is the endpoint 19 on the surface of the object to be tested 13 in the target point of the point laser 17 , there is the dome 1 at the exact height above the object to be tested 13 , The orientation of the object to be tested in the measurement plane is indicated by the insertion of the label 14 additionally supported. So there are lettering 14 of the object to be tested 13 In the camera image and the vector graphic superimposed on the image, the positioning is correct.

It a measuring device was designed, designed, constructed and designed finally made, which is an ergonomic and easy manual operation allows and which is transportable. The measuring device includes a likewise suitably designed trolley case for protection and for that Transport.

In an example algorithm for evaluating the label image quality of a label image 14 a Sollriftriftbild in the form of a vector graphics is provided and the Sollriftriftbild with the means of image processing technology and with predetermined calculation methods dimensional and location technology in a match with the recorded label image 14 brought. Subsequently, in each case referred to the Sollriftriftbild from the label 14 determines at least one of the following attributes with a respectively associated individual evaluation: the completeness; the contrast; the edge width and / or the homogeneity of the label image. If only one of these attributes with associated individual evaluation is determined, only from this one evaluation will an overall assessment regarding the label image quality of the label image be obtained 14 determined. Are more of these attributes associated with each Based on individual evaluations, taking into account a given weighting for each evaluation in question, an overall assessment of the lettering image quality of the label image is calculated from the available multiple evaluations 14 determined.

For the determination of the respective attributes and their respective ones Individual ratings are areas around individual elements of the match provided Sollriftriftbildes with the means of image processing technology examined.

The the elements of the examined areas of the Sollriftriftbildes corresponding elements of the lettering image are by means of a Binarization each newly determined.

The Completeness of the label image is by comparison calculated with the target label image and depending on the result evaluated according to the calculation.

Of the Contrast of the label is according to a calculated and dependent on Michelson's standard formula according to the result of the calculation.

The Edge width of the label image is made of a gradient and a Intensity difference calculated and dependent on Result of the calculation evaluated accordingly.

• a) eine Standardabweichung von Intensitäten der Bildpunkte untersuchter Elemente;
• b) eine Intensitätsdifferenz zwischen einer vorgegebenen Anzahl von hellsten und dunkelsten Punkten jedes untersuchten Elements, normiert mit einer Intensitätsdifferenz zwischen einer Vorder- und einer Hintergrunddarstellung;
• c) eine Kovarianz in einer Nordsüd- und einer Ostwestrichtung, berechnet unter Verwendung einer Grauwertübergangsmatrix mit Intensitäten benachbarter Punkte entlang einer der genannten Koordinatenrichtungen aus den Abweichungen der Punkte von den Mittelwerten, normiert über die Anzahl aller Punkte eines untersuchten Elements;
• d) lokale Kontraste, berechnet in die unter c) genannten Richtungen unter Verwendung der genannten Grauwertübertragungsmatrix und den daraus erhaltenen Intensitätsdifferenzen, normiert über die Anzahl aller Punkte eines untersuchten Elements.

The homogeneity of the label image is calculated from at least one of several different criteria and evaluated according to the result of the calculation, the various criteria comprising:

• a) a standard deviation of intensities of the pixels of examined elements;
• b) an intensity difference between a predetermined number of brightest and darkest points of each examined element normalized with an intensity difference between a foreground and a background representation;
• c) a covariance in a north-south and east-west direction, calculated using a gray value transition matrix with intensities of adjacent points along one of said coordinate directions from the deviations of the points from the mean values, normalized by the number of all points of a studied element;
• d) local contrasts, calculated in the directions mentioned under c) using said gray-scale transmission matrix and the intensity differences obtained therefrom, normalized by the number of all points of a tested element.

For becomes the predetermined number of brightest and darkest points a number used between an upper range of a two-digit and an upper range of a three-digit decimal number.

To bring the target label image in accordance with the label image 14 from the recorded becomes the object 13 with the label 14 segmented by a residual background and subsequently the label image 14 from said object 13 segmented.

A distortion of the lettering image generally caused by lens elements used 14 is corrected in advance at the level of the person admitted.

The target lettering image is determined by means of a so-called best-fit algorithm on the label 14 positioned.

To position the target label image on the label image 14 An image translation, an image rotation and an image scaling is calculated and thus the target markings are compensated in a corresponding manner.

Next the correction of the general distortion will be an additional Correction performed dividing the target label image is in subpictures that are limited to one with shifts so-called best-fit algorithm positioned on the label be calculated, with this calculated shifts a center of each relate to the fields associated and in a predetermined Grid deposited and displacements of individual points be interpolated bilinearly from the shift values in the grid.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• US 5859923A [0014]
• US 5969374A [0015, 0025]
• US 5837983 A [0016]

Cited non-patent literature

• - International Conference on Technical Diagnostics, 10th IMEKO TC10, 9-10 June, 2005, Budapest, Hungary, pp: 99-102, High-speed Label Inspection System for Textile Industry, István Szatmari and Ákos Zarándy [0014]

Claims (22)

A method of measuring and evaluating a lettering image quality of a lettering image on an object, comprising method steps for illuminating the lettering image by illumination means, recording the illuminated lettering image by a camera system, and evaluating the lettering quality of the lettering image by the recorded image by an electronic computing system having an image processing technique cooperating therewith; characterized in that - a target mark image in the form of a vector graphic is provided, - that the target mark image by means of image processing technology and with predetermined calculation methods dimensional and location technology is brought into agreement with the recorded label image, - that in each case based on the Sollbeschriftbild the label of at least one of the following attributes is determined with a respective individual evaluation: a) the completeness; b) the contrast; c) the edge width; d) homogeneity; and - that when determining only one of these attributes with associated individual evaluation from only this one evaluation and determination of at least two of these attributes with respectively associated individual ratings from the available ratings, taking into account a given weighting for each relevant evaluation an overall rating with respect to the label image quality of the label image ( 14 ) is determined. Method according to claim 1, characterized in that that for the determination of the respective attributes and the each associated individual ratings areas by individual Elements of the matched Sollriftriftbildes with the means of image processing technology are examined. Method according to claim 2, characterized in that that the elements of the examined areas of the Sollriftriftbildes corresponding elements of the label image by means of a Binarisierung each newly determined. Method according to one of claims 1 to 3, characterized in that the completeness of Label image by comparison with the target label image calculated and according to the result of the calculation accordingly Is evaluated. Method according to one of claims 1 to 3, characterized in that the contrast of the lettering image according to a standard formula known per se calculated according to Michelson and depending on the result of Calculation is evaluated accordingly. Method according to one of claims 1 to 3, characterized in that the edge width of the label image calculated from a gradient and an intensity difference and valued accordingly depending on the result of the calculation becomes. Method according to one of claims 1 to 3, characterized in that the homogeneity of the lettering image calculated from at least one of several different criteria and valued accordingly depending on the result of the calculation with the different criteria: a) one standard deviation intensities of the pixels of examined elements; b) an intensity difference between a given number of the brightest and darkest points of each element studied, normalized with an intensity difference between one Foreground and a background view; c) a covariance in a north-south and east-west direction, calculated using a gray level transition matrix with intensities neighboring points along one of said coordinate directions from the deviations of the points from the mean values, standardized over the number of all points of an examined element; d) local Contrasts, calculated in the directions mentioned under c) below Use of said gray value transmission matrix and the resulting intensity differences, normalized by the number of all points of a tested element. Method according to claim 7, characterized in that that for the given number of the brightest and darkest Points a number is used, the between an upper Range of a two-digit and an upper range of a three-digit Decimal number lies. Method according to one of claims 1 to 8, characterized in that for bringing the Sollriftriftbildes in accordance with the label of the shot the object with the lettering image from a remaining background segmented and subsequently the label of said object is segmented. Method according to one of claims 1 to 9, characterized in that one of the lens elements used generally caused distortion of the label image on the plane the recipient is corrected in advance. Method according to one of claims 1 to 10, characterized in that the Sollbeschrift image is positioned on the label using a so-called best-fit algorithm. Method according to claim 11, characterized in that that for positioning the target label image on the label image an image translation, image rotation, and image scaling calculated and thus the Sollriftriftbild in a similar manner is compensated. Method according to one of claims 10 to 12, characterized in that in addition to the correction of the general Distortion performed an additional correction in which the target letter image is subdivided into partial images, those with a shifts limited so-called best-fit algorithm be positioned on the label, where calculated Shifts to a center of the relevant partial images assigned and deposited in a predetermined grid and shifts of individual points from the shift values in the grid be interpolated bilinearly. Measuring device for carrying out the method according to one of claims 1 to 13, comprising a lighting and a camera system, characterized in that a dome ( 1 ) is provided with: a) a base ( 2 ) in one through the base ( 2 ) base plane ( 3 ); b) one of the dome's ( 1 ) covered middle area ( 4 ); c) a dome vertex ( 5 ); d) a dome inner surface ( 6 ); e) the lighting system ( 7 ), which is close to a base inner edge ( 8th ) around an existing extent of the dome ( 1 ) with an even distribution of uniform illumination of the dome inner surface ( 6 ) ( 9 ) is arranged; f) an aperture ( 10 ) arranged between the lighting system ( 7 ) and the middle area ( 4 ) for light shading of the middle region ( 4 ) below the dome vertex ( 5 ) when illuminating the dome inner surface ( 6 ) by the lighting system ( 7 ); g) the camera system ( 11 ) in the dome vertex ( 5 ) looking towards the shaded middle area ( 4 ) is arranged; and h) one in the shadowed mid-range ( 4 ) Placeable support member ( 12 ) for an item ( 13 ) with a shadowed mid-range ( 4 ) under the camera system ( 5 ) to be laid ( 14 ). Measuring device according to claim 14, characterized in that the dome ( 1 ) is a hemisphere. Measuring device according to claim 14 or 15, characterized in that the dome inner surface ( 6 ) is formed evenly reflective light. Measuring device according to one of claims 14 to 16, characterized in that the illumination system ( 7 ) at least substantially with a circular fluorescent lamp as a lighting means ( 9 ) is formed. Measuring device according to one of claims 14 to 17, characterized in that in the dome vertex ( 5 ) an opening ( 15 ) in the dome ( 1 ) for at least partial placement of the camera system ( 11 ) is provided therein. Measuring device according to one of claims 14 to 18, characterized in that either the dome ( 1 ) alone with respect to the carrier part ( 12 ), the carrier part ( 12 ) alone opposite the dome ( 1 ) or both each opposite each other along a common central axis ( 16 ) are held displaceable. Measuring device according to one of claims 14 to 19, characterized in that inside the dome ( 1 ) at least one single point laser ( 17 ) with beam direction ( 18 ) to an end position ( 19 ) for a camera system ( 11 ) to come to rest ( 14 ) is arranged. Measuring device according to claim 20, characterized in that the displaceable holder ( 20 ) between dome ( 1 ) and carrier part ( 12 ) and the arrangement of the point lasers ( 17 ) are provided in such a way that with the point lasers ( 17 ) concerning a given point ( 21 ) within one below the camera system ( 11 ' ) to lie next picture ( 14 ) a triangulation is to accomplish. Measuring device according to Claim 21, characterized that as triangulation a triangulation with an angle of 45 Degree is to accomplish.