WO2002003035A1 - Method and device for testing a test specimen - Google Patents

Abstract

The invention relates to a method for testing a test specimen, comprising the following steps: stimulating the test specimen with respect to at least one operating parameter at a plurality of operating points or operating ranges; and detecting the reaction of the test specimen at said operating points or in said operating ranges; and evaluating said reaction by means of image processing techniques.

Description

 Description Method and device for testing a test object

The invention relates to a method and a device for testing a test specimen.

As part of increasing product quality, it is necessary to have reliable quality assurance in production and in the final inspection. By increasing the inspection depth, which is subject to a continuous improvement process, later very expensive field failures can be avoided. Checking all functionalities and properties of a product is therefore particularly important. For example, when testing a prototype of an integrated circuit or a machine part, it is necessary in many cases to test over a wide operating range depending on several input or operating parameters. For this purpose, there are already stimulation devices which, by specifically influencing the operating conditions in the test object or by applying predetermined stimulations, for example a predetermined voltage or pressure function, enable the test object to run through an entire operating range or to provide targeted stimulation at selected operating points , The reactions of the test object to the stimulation serve as initial values, on the basis of which a test protocol is created and compared with reference values.

A weakness of previous test methods and test devices lies in the evaluation of the test subject's reaction. The larger the operating range to be tested, the finer the desired resolution of the continuously changing reaction of the test object, the higher the number the decisive or to be checked operating parameters, the higher the number of output values to be evaluated. The duration of the evaluation can increase to an unacceptable level.

As a compromise to optimize the test duration and the scope of the test, the test object is typically only tested at selected operating points or predominantly in "interesting" operating areas. However, this has the serious disadvantage that the "interesting" operating areas of a new prototype are not necessarily known a priori. In addition, sporadic errors are often not recognized. There are quality gaps because only certain, specified settings are recorded. In addition, the rapid measurement of individually selected points can cause undesired settling processes that falsify the measurement results. Overall, due to the type of evaluation, feedback of the measurement results into the development or manufacturing process of the test object is insufficient or not possible at all.

It is also known to carry out a visual evaluation of the reaction, in particular of automotive, space and aviation components. Certain operating parameters, for example the input voltage and the operating temperature of the test specimen, are each changed over the range relevant for the use of the components, while the reaction, for example the output voltage, is shown as color values on a conventional electron beam tube. Appropriate synchronization of the electron beam deflection and the change in one of the operating parameters, in which, for example, the relevant voltage range is run through simultaneously with the deflection over a single line, results in one colored two-dimensional image display that can be evaluated visually.

The main disadvantage of such a procedure is that a temporal synchronization between display and stimulation is required, which produces a large number of side effects and excludes many useful test methods. In addition, the evaluation cannot take place automatically.

An object of the invention is to provide a test method or a test device, to avoid the above-mentioned disadvantages of the prior art and to enable extensive tests to be carried out efficiently. In addition, the implementation of the invention should not require costly or complex modifications of any existing test devices available on the market.

According to the invention, this object is achieved by the method according to claim 1 or the device according to claim 6. Preferred embodiments of the invention are defined in the subclaims.

The invention is based on the basic principle of the inventive, symbiotic combination of conventional stimulation techniques (which can only be expanded essentially due to the method) with an evaluation of the reactions of the test specimen by techniques known per se from image processing. Further embodiments of the invention are refined by new techniques which advantageously support or utilize the symbiotic effect of this combination.

According to the invention, for example, the classification, representation, processing, summary and the

Comparison of the reaction values of a stimulated test object through image processing algorithms and operations. For this purpose, the reaction of the test object with respect to at least one test criterion is used to determine the content of the pixels to be processed. Together, the pixels, also called pixels, result in a multidimensional image in which the image coordinates are determined by operating parameters. Accordingly, there is a clear association between each pixel and a specific operating area, the size of a respective pixel or its associated operating area being able to be varied as required. Analog and digital results can be processed. The digital ones can be fed directly to the digital image processing.

The invention can be used for any types of test specimen, any operating parameters and any test criteria. For example, the invention can be used to test the functionality of an analog, digital, or hybrid electronic circuit.

However, it can also be used to test the products of an injection molding machine by displaying or evaluating the curing of the product as a function of the operating parameters temperature and pressure as a test criterion. For example, input voltage, input current, a selected input sequence, temperature, pressure, time or frequency can be used as operating parameters.

All image processing algorithms and functions can be used within the scope of the invention. In addition to the basic mathematical functions such as addition, subtraction, masking, etc. of image data, various, both selective and integrating, filter functions such as erosion, dilation and noise detection are of great importance Importance. So-called "area of interest" blanking and position-dependent scaled evaluations can also play an important role in the evaluation.

According to a particularly advantageous embodiment of the invention, the image, i.e. the reaction of the test object is evaluated by reference to one or more stored pattern reactions, which may also be linked to one another. This is useful, for example, when a subject is to be compared with a sample. It is also possible to create a fictitious sample reaction that is created by the user or that results from the mathematical or image-processing summary of several sample reactions, which thus takes into account the reactions of several sample candidates or a fictitious sample candidate.

Furthermore, a measured value obtained (reaction of the test object) can also be used as a further image coordinate (variable). This can be done, for example, analogously when comparing iterative matching processes and their course and digitally when using the digital signature for random address control.

Due to the possibilities of processing the pixels opened up by the invention, it is not necessary that a test object is stimulated at the same operating points or over the same operating ranges as the sample test object. In this case, the undefined pixels, ie the operating points that are not explicitly excited or measured during the stimulation, can be interpolated or extrapolated from the measured pixels using image processing algorithms. However, there is also a comparison without direct interpolation or extrapolation the undefined image areas possible through image processing measures.

Several images can arise from the respective reactions of the test specimen with regard to different test criteria. Nevertheless, the respective reactions can be summarized in part or in total using image processing algorithms.

The stimulation can take the form of analog, discrete or digital stimulation. Possibly. one of the operating parameters is changed continuously in order to keep the effect of any transient events as low as possible. The reaction of the test object is only recorded at the specified operating points or in the specified operating ranges.

As an alternative control, one of the operating parameters to be set for the stimulation can be determined for several operating points using a look-up table. In this way, programmable stimuli can be generated that optimally measure a response to transients or step functions. Such a stimulation can also be used to measure switching times, delay times and hysteresis behavior.

The resulting image can take any form which comprises selected operating points or operating areas relevant for the test. Also an afterthought

Selection of relevant areas during image processing based on the pixel values is possible. The image can also have gaps, ie undetermined pixel values. The arrangement or distribution of the pixels within the image is arbitrary; they do not have to be arranged at regular intervals or according to a grid. The picture is thus detached from any video standard. The pixel clock can be derived from any clock, this z. B. could come from a test item exit. Pixel type, line length and image height are freely selectable and limited by the hardware chosen for image processing. In an extreme case, the image can only consist of individual, irregularly set, spatial image points, the coordinates of which or their assigned operating points can have been selected at random. The latter is useful, for example, for random tests, which serves quality assurance and saves measurement time.

When testing digital devices, in which the reaction of the test object to a given stimulation as a signature or the like. is present, a value obtained from the reaction or signature can also be returned for use as a further operating parameter or measured value. Such a feedback creates a sequence of operating parameters or stimulation sequence, which leads to a very characteristic reaction that can be easily evaluated. Under the operating parameters of such a stimulation sequence, there may be no function-related mathematical relationship.

Claims

Expectations 1. A method for testing a test object with the following steps: stimulating the test object with respect to at least one operating parameter at several operating points or in operating areas; and Detection of the reaction of the test object with respect to at least one test criterion at the operating points or in the operating areas; marked by Evaluation of the reaction using techniques from image processing. 2. The method according to claim 1, wherein the reaction is used to create a multi-dimensional image on which the evaluation is based, in which the operating parameters represent the image coordinates and the reaction of the test object determines the contents of the pixels. 3. The method according to any one of the preceding claims, wherein the reaction is evaluated by reference to at least one stored pattern reaction directly or via a mathematical link with the pixel values. 4. The method according to any one of the preceding claims, wherein the change of at least one of the operating parameters during the stimulation takes place continuously. 5. The method according to any one of the preceding claims, wherein at least one of the operating parameters to be set during the stimulation is determined for a plurality of operating points on the basis of any function or a look-up table. 6. Device for testing a test specimen with: Stimulation modules that stimulate the test object with respect to at least one operating parameter at several operating points; and Acquisition modules that record the reaction of the device under test with respect to at least one criterion at the operating points; characterized by an evaluation device which evaluates the reaction using techniques from image processing. 7. The device as claimed in claim 6, which uses the reaction to produce a multidimensional image on which the evaluation is based, in which the operating parameters represent the image coordinates and the reaction of the test object indirectly or directly determines the pixel values. 8. The device according to claim 6 or 7, which evaluates the reaction by reference to at least one stored pattern reaction directly or via a mathematical link with the pixel values. 9. Device according to one of claims 6 to 8, which continuously changes at least one of the operating parameters during the stimulation. 10. Device according to one of claims 6 to 9, which determines the operating parameters to be set during the stimulation for a plurality of operating points on the basis of an arbitrary function or a look-up table.