1、Non-destructive testing Part 1 : Quantitative measurement of imaging properties Enalish version of DIN EN 13068-1 Radioscopic testing ICs 19.100 DIN EN 13068-1 - Zerstrungsfreie Prfung - Radioskopische Prfung - Teil 1 : Quantitative Messung der bildgebenden Eigenschaften European Standard EN 13068-1
2、 : 1999 has the status of a DIN Standard. A comma is used as the decimal marker. National foreword This standard has been prepared by CEN/TC 138. The responsible German body involved in its preparation was the Normenausschuss Materialprfung (Materials Testing Standards Committee), Technical Committe
3、e Durchstrahlungsprfung und Strahlen- schutz. EN comprises 21 pages. _ No part of this standard may be reproduced without the prior permission of IN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany, as the exclusive right of sale for German Standards (DIN-Normen)
4、. Ref. No. DIN EN 13068-1 : 2000-02 English price group 12 Sales No. 11 12 07.00 EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 13068-1 December 1999 ICs 19.1 O0 English version Non-destructive testing Part 1 : Quantitative measurement of imaging properties Radioscopic testing Essais non destr
5、uctifs - Contrle par radioscopie - Partie 1 : Mesure quantitative des caractristiques dimage Zerstrungsfreie Prfung - Radioskopische Prfung - Teil 1 Quantitative Messung der bi Idg e bend en Eigenschaft en This European Standard was approved by CEN on 1999-1 0-29 CEN members are bound to comply with
6、 the CENKENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national stand- ards may be obtained on application to the Central Secretari
7、at or to any CEN member. The European Standards exist in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official v
8、ersions. CEN members are the national standards bodies of Austria, Belgium, the Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, the Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and the United Kingdom. CEN European Committee for Standardiz
9、ation Comit Europen de Normalisation Europisches Komitee fr Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels O 1999. CEN - All rights of exploitation in any form and by any means reserved worldwide for CEN national members. Ref. No. EN 13068-1 : 1999 E Page 2 EN 13068-1 : 1999 Conten
10、ts Foreword . 2 1 Scope . 3 2 Normative references 3 3 Radioscopic system . 3 4 Measurement of image quality parameters . 4 Annex A (informative) Example for a test report according to EN 13068-1 21 Foreword This European Standard has been prepared by Technical Committee CENITC 138 “Non-destructive
11、testing“, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by June 2000, and conflicting national standards shall be withdrawn at the latest by June 2000. Ac
12、cording to the CENKENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portug
13、al, Spain, Sweden, Switzerland and the United Kingdom. EN 13068 comprises a series of European Standards of radioscopic systems which is made of the following: EN 13068-1 :I 999, Non-destructive testing - Radioscopic testing - Part 1: Quantitative measurement of imaging properties. EN 1 3068-2: 1999
14、, Non-destructive testing - Radioscopic testing - Part 2: Check of long term stabiliw of imaging devices. prEN 1 3068-3, Non-destructive testing - Radioscopic testing - Pan 3: General principles of radioscopic testing of metallic materials by X- and gamma-rays. Annex A is informative. Page 3 EN 1306
15、8-1 : 1999 1 Scope The procedures given in this standard can be applied to all radioscopic systems which provide an electronic signal to a display unit or an automated image interpretation system. The radioscopic system is analysed for the response to well defined test specimen. The measurement shou
16、ld be performed by a sufficiently equipped laboratory. From the results, the specifications of the imaging system regarding image properties can be derived. This standard so far does not include imaging properties under moving conditions. 2 Normative references This European Standard incorporates, b
17、y dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European stan
18、dard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies. EN 2924 1 -2 rgonomic requirements for ofice work with visual display terminals (VD Ts) - Part 2: Guidance on task requirements (IS0 9241 -2: 1 992) EN 29241
19、-3, Ergonomic requirements for office work with visual display terminals (VDTs) - Part 3: Visual display requirements (IS0 9241 -3: 1992) 3 Radioscopic system In the context of this standard a radioscopic system consists of a radiation source, a handling system, collimators, filters and an imaging d
20、evice. An imaging device consists of an X- or gamma ray conversion device which transforms the radiation relief into an output signal S for numerical or optical presentation (see figure 1). Image processing systems can be part of the imaging device. In the case of visual evaluation it includes the d
21、isplay unit. In cases of fully automated image evaluation systems the display unit is not part of the system. I 2 6 Key 1 Radiation source 2 Object 3 Radiation conversion device 4 Output signal 5 Image processing 6 Display unit Figure 1 - Typical arrangement of an imaging device For the specificatio
22、n of the imaging properties of imaging devices terms and parameters of information theory and radiographic testing are used. The parameters in table 1 define the image quality of imaging devices. In some descriptions of image quality parameters the term “signal-to-noise-ratio (SNR)“ is used. Within
23、the meaning of information theory SNR is the ratio of the actual partial scale signal AS to rms-value %Ms of the overlay noise signal, see figure 2. Page 4 EN 13068-1 : 1999 a Signal Figure 2 - Determination of AS and S, from output signal S 4 Measurement of image quality parameters 4.1 Principle 4.
24、1.1 Conversion device The basis of all measurements with the conversion device is the use of a defined radiation relief by artificial test indicators as an input signal and the measurement of the system response in the linear raw output signal with suit- able measuring equipment (see figure 1). All
25、measurements shall be done with the imaging device itself. In figure 3 the principle set up for all measurements is shown. The radiation filter shall be placed in front of the X-ray tube. Collimators shall be used to reduce scattering radiation. All test indicators shall be placed in front of the in
26、put screen of the conversion device. They produce a defined radiation relief as an input signal. Measuring equipment shall be connected to the final output signal for measurement of the total system response. For video signals the measuring equipment shall fulfill the following minimum requirements:
27、 - - - Bandwidth 2 50 MHz; - - Signal averaging function. Amplitude resolution 2 10 Bit; Time resolution 2 1 O Bit = 1024 sample points; Minimum sampling rate 2 100 MHz; Page 5 EN 13068-1 : 1999 5 e .- c c E a Q - m 3 U W o, - E C O o C ._ c i2 U a a v) w C L LL Y ._ o uo c e E c ffl C O o c m Page
28、6 EN 13068-1 : 1999 a O K ru r O - E K O .- c E m x W - a O O * c 8 K .- Page 7 EN 13068-1 : 1999 Tube voltage kV Because image quality parameters are dependent on radiation energy and quality, measurements shall be done in the lower, middle and upper part of a permissible energy range of the radios
29、copic system with constant potential X- ray equipment. In order to guarantee a defined radiation quality, the radiation filtering shall be used as given in table 2. The tube current shall be adjusted to give a dose rate of 0,Ol mGy/min; 0,l mGy/min; 1,0 mGy/min or 10 mGy/min at the input plane of th
30、e conversion device. Table 2 - Radiation filtering for system measurement Radiation filter thickness and material “) mm 300 50 7 i 0,5 AI 1 O0 22 f 0,5 AI 15 f 0.5 Cu 400 25 i 0,5 Cu 35 f 0,5 Cu The ouritv of the filter material should be better than 99 Yo 400 During measurements the radioscopic sys
31、tem shall be operated in accordance with the instruction manual and manufacturers instructions. The radiation intensity shall be adjusted to such a value that in the middle of the input screen behind the radiation filter (without any test specimen) the output signal S shows the maximum signal amplit
32、ude S,.The radiation intensity shall be measured with an ionization chamber in the middle in front of the input screen and documented together with all other measuring results. X-ray detectors should have a sufficient period of use (e. g. for X-ray image intensifiers 1 Gy) before the measurements ar
33、e made. 4.1.2 Display unit and image processor For assessment of display units and image processors the following procedure is recommended. A bar pattern is generated by an electronic test pattern generator according to the requirements 4.1.1 for measuring equipment (according to EN 29241 -2 and EN
34、29241 -3). The generator shall be able to produce vertical bars up to the limiting band width of the display unit or image processor. The bar pattern is displayed on the image display unit. For evaluation a small section (max. 10 Yo of the total display area) is picked up by an optical sensor. The r
35、esult is digitized. Suitable optical sensors are TV cameras or linear line-scan cameras. The magnification scale shall be at least 10. Therefore, at least 10 pixels in the frame buffer are available for the presentation of 1 pixel on the N monitor. Beating effects between the pixel frequencies of th
36、e display unit and camera can be compensated by signal integration. 4.2 Measurement procedures 4.2.1 Conversion device 4.2.1.1 Sharpness (spatial resolution) In order to characterize the system sharpness the following three image quality parameters shall be measured: a) Inherent unsharpness For meas
37、urement of the inherent unsharpness 1.1 (see equation (2) an intensity step function shall be produced by a sharp edge of absorbent material (figure 4). The image of the edge shall be located in the centre of the input screen perpendicular and horizontal to the read out line of the detector. The rad
38、iation intensity shall be adjusted by the tube current according to the selected values as given in 4.1. In order to reduce the effect of scattered radiation the input screen shall be covered by absorbing material whereby approximately 10 Yo of the input screen should be irradiated only. The system
39、shall be adjusted such that the output signal shows a black-to-white signal (Edge Spread Function ESF) with a minimum signal amplitude of 90 Yo of the maximum electronic signal amplitude and an overshoot less than 10 %. The inherent unsharpness is proporional to the rise time t, of the edge spread f
40、unction. If there is an adjustable diaphragm the setting shall be stated in the protocol. Page 8 EN 13068-1 : 1999 A second measurement will give the value for the scale factor s, in order to calculate the inherent unsharpness in millimetres (figure 5). The edge shall be substituted by a test indica
41、tor with well-known length /and the corre- sponding dimension (time interval for an output signal) x, shall be measured (see equation (I). (1) I S =_ “4 L/; = s, . 1, with overshoot 5 10 h with 4 = 90 % - ESF - 10 Z - ESF b) SDatial modulation transfer function MTF) The starting point for the calcul
42、ation of the MTF is the edge spread function from the former unsharpness measurement (figure 6). The edge spread function shall be digitized with high resolution and stored in a computer. The sampling theorem shall be considered. In the next step the ESF shall numerically be differentiated in order
43、to get the Line Spread Function LSF. The magnitude spectrum of the Fourier-transformed LSF will give the MTF. For a common representation of MTF curve the modulation m for the spatial frequency f= O Lp/mm shall be normalized to m = 1. If possible the vertical MTF can be determined by using the unmod
44、ified grey values taken from a digital image processing system. c) Contrast ratio for low sDatial frequencies To measure the contrast ratio Co at first the input screen shall be irradiated with a uniform radiation relief without any mask (figure 7). The mean signal amplitude So in the middle of the
45、input screen area shall be measured. In the next step 10 Yo of the input screen area shall be covered with an absorbent mask in the centre and again the mean amplitude S, of the electronic signal behind the mask shall be measured. The absorbent mass shall reduce the intensity of the radiation by a f
46、actor 1000. 4.2.1.2 Contrast The exposure time per frame, the number of integrated frames and the dose rate shall be stated in the protocol. Contrast properties of the radioscopic system are described by the following image quality parameters: a) Contrast sensitivity For producing the radiation reli
47、ef with decreasing radiation contrast a steel plate of thickness din combination with a step wedge (steel) on the source side of the plate shall be positioned in front of the input screen (figure 8). The step wedge shall be positioned in the direction of the read out line of the detector and in the
48、centre of the input screen. In the output signal the signal-to-noise-ratio SNR of each step wedge shall be measured. The thinnest step with a SNR 2 2 shall be regarded as the minimal detectable wall thickness change Aw,. S= A w,Jw (4) In order to reduce the influence of quantum noise the feature of
49、signal averaging shall be used. b) Wall thickness ranae At the beginning of the measurement radiation parameter like energy and tube current shall be defined and fixed. Only a small part (- 1 O %) of the front screen shall be irradiated in order to reduce scattering effects. In front of the input screen a step-like test indicator with a step height of - 1 mm shall be placed (figure 9 ). The thinnest step w, which gives the maximum amplitude S, of the output signal shall be the starting point of the measurement. The test indicator shall be shift
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