ANSI T 563 OM-2015 Equivalent Black Area (EBA) and count of visible dirt in pulp paper and paperboard by image analysis.pdf

1、TAPPI/ANSI T 563 om-15 PROVISIONAL METHOD 1996 REVISED 1997 OFFICIAL METHOD 2003 REVISED 2008 REAFFIRMED 2012 REVISED 2015 2015 TAPPI The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Association assume no liability o

2、r responsibility in connection with the use of such information or data, including but not limited to any liability under patent, copyright, or trade secret laws. The user is responsible for determining that this document is the most recent edition published. Approved by the Standard Specific Intere

3、st Group for this Test Method TAPPI CAUTION: This Test Method may include safety precautions which are believed to be appropriate at the time of publication of the method. The intent of these is to alert the user of the method to safety issues related to such use. The user is responsible for determi

4、ning that the safety precautions are complete and are appropriate to their use of the method, and for ensuring that suitable safety practices have not changed since publication of the method. This method may require the use, disposal, or both, of chemicals which may present serious health hazards to

5、 humans. Procedures for the handling of such substances are set forth on Material Safety Data Sheets which must be developed by all manufacturers and importers of potentially hazardous chemicals and maintained by all distributors of potentially hazardous chemicals. Prior to the use of this method, t

6、he user must determine whether any of the chemicals to be used or disposed of are potentially hazardous and, if so, must follow strictly the procedures specified by both the manufacturer, as well as local, state, and federal authorities for safe use and disposal of these chemicals. Equivalent Black

7、Area (EBA) and count of visible dirt in pulp, paper and paperboard by image analysis 1. Introduction The level of visible dirt present in pulp, paper or paperboard can impact its usefulness in a specific end use application. In such cases, the presence of visible dirt specks which are high in number

8、, easily noticed in visual examination, or both, may detract more from the apparent usefulness of the paper material than does a lower number of specks, or specks which are less easily noticed by the eye. Both the number of dirt specks and their visual impact may be important. For someone controllin

9、g or monitoring the paper making process, the absolute physical area of dirt, or the number of dirt specks present in an inspection area may be of greatest importance. For the end user of the paper material, the overall visual impression may be the critical parameter. 2. Scope 2.1 This method uses i

10、mage analysis to determine the level of dirt in pulp, paper, and paperboard in terms of Equivalent Black Area (EBA) of dirt specks within the physical area range of 0.02 to 3.0 mm2 reported in parts per million as well as the number of dirt specks per square meter of sample. Using the algorithm pres

11、cribed in this method, the maximum dirt size is limited to 3.0 mm2.Extension to other speck sizes (for example those greater than 3.0 mm2in physical area), may require changes in equipment, calculation procedures, or both, and is not covered in this test method. This method cannot be used for physic

12、al area measurements since it does not correctly measure the dirt specks for that mode of measurement. 2.2 The specimen to be evaluated should have a brightness, as determined by TAPPI T 452 “Brightness of Pulp, Paper, and Paperboard (Directional Reflectance at 457 nm),” of 30% or greater. It may be

13、 necessary to reform some pulp sheets into handsheets if the surface is too rough or textured. 2.3 This method is an instrumental equivalent of TAPPI T 437 “Dirt in Paper and Paperboard” and TAPPI T 213 “Dirt in Pulp,” both of which report the equivalent black area of dirt in parts per million, and

14、TAPPI T 537 “Dirt Count in Paper and Paperboard (Optical Character Recognition - OCR)” which reports the number of specks of 0.02 mm2 or larger per square meter. This method can be implemented using any image analysis system, provided that it meets the criteria specified herein. T 563 om-15 Equivale

15、nt Black Area (EBA) and count of visible / 2 dirt in pulp, paper and paperboard by image analysis 2.4 This method, and corresponding precision statement, was developed using laboratory analyzers and cannot be considered applicable to on-line systems. 3. Significance 3.1 The visual impact of a dark s

16、peck on a light background varies as a function of the speck size. The calculation of this visual impact is done based on Riccos law in this test method, and reported in terms of equivalent black area. As the dirt speck becomes sufficiently large, the equivalent black area of a black speck (a Yc/2va

17、lue of 2.4%) on a white background (a Yc/2value of 81.5%) will approach the specks physical area. The use of the equivalent black area calculation procedure in this test method is highly significant, as it provides data continuity of dirt measurement with procedures such as TAPPI T 437 which have be

18、en in use for over 50 years (1). NOTE 1: All Yc/2value (557 nm) reflectances mentioned in this method are to be measured on a diffuse reflectance instrument in accordance with T 527. 3.2 Dirt is usually found on the surface of the sheet, however dirt particles which are embedded may also be discerni

19、ble by eye in papers that are transparent or translucent. The level of visible dirt present in papers used in printing, writing, and other forms of communication may be both an aesthetic and performance requirement. For example, bond and writing papers may be subjected to close visual inspection in

20、their intended use, but may also be required to perform on scanners, bar code readers, or other automated optical recognition devices where dirt above some critical level could impact performance. 3.3 Similar considerations may be appropriate for papers used in wrapping and packaging. In addition, s

21、pecial considerations may be required where such materials come in contact with foodstuffs, and where visible specks may be considered unacceptable. 3.4 Dirt in the form of gritty materials embedded in the sheet is a serious defect in many printing papers used in contact printing because of the pitt

22、ing and wear that they can cause in printing plates. Such dirt can also occur in paperboard such as linerboard, and when present may cause significant reduction in bursting strength. Dirt of this type is not easily detected using this procedure, because there is little color contrast between the dir

23、t speck and the background sheet. 3.5 The repeatability of this method is significantly better than that of TAPPI T 437 “Dirt in Paper and Paperboard.” 4. Related documents TAPPI T 213 “Dirt in Pulp,” TAPPI T 437 “Dirt in Paper and Paperboard,” TAPPI T 452 “Brightness of Pulp, Paper and Paperboard (

24、Directional Reflectance at 457 nm),” TAPPI T 537 “Dirt Count in Paper (Optical Character Recognition - OCR),” and TAPPI T 527 “Color of Paper and Paperboard (d/0 geometry).” 5. Definitions 5.1 Dirt - any foreign matter embedded in or on the sheet, which, when examined by reflected light has a contra

25、sting, darker color to the sheet surface and has an equivalent black area of 0.02 mm2or greater as determined by this test method. 5.2 The equivalent black area (EBA) - the area of one of the round black spots (a Yc/2value of 2.4%) on the TAPPI Dirt Estimation Chart that has the same apparent area w

26、hen examined visually upon its white background (a Yc/2value of 81.5%) as does the dirt speck when examined visually upon the particular sheet in or upon which it is embedded. A larger “gray” dirt speck has the same visual impact as a smaller “black” one when viewed on the same sheet and under the s

27、ame conditions. 5.2.1 The equivalent black area (EBA) of a dirt speck determined visually is generally less than its physical area. The EBA approaches the physical area only as the speck becomes large. 5.2.2 This definition of EBA is technically identical to that found in TAPPI T 213 and TAPPI T 437

28、, and this test method produces results that are the technical equivalent of those test methods except for the minimum dirt size. 3 / Equivalent Black Area (EBA) and count of visible T 563 om-15 dirt in pulp, paper and paperboard by image analysis 6. Apparatus 6.1 Description of the Apparatus: 6.1.1

29、 Detector: The detector is densitometric with at least 256 gray levels (G.L.) of sensitivity with the physical pixel resolution having an effective area of 0.020 mm2or less (see Note 2). The detector must view the specimen normal to its surface. The light is un-polarized and is concentrated in the v

30、isible portion of the spectrum such that 95% of the detected light reflected from a white surface will be between 380 nm and 740 nm. The illumination must be diffuse or axially symmetric with an incident angle of 45 5; the uniformity of the illumination on the specimen stage before any software corr

31、ections must be within 4%. The specimen stage must be shielded to prevent influence from ambient light. NOTE 2: Precision improves with resolution. Therefore it is advisable to have as high a pixel resolution as is practical for the smallest dirt specks. However, to prevent false detections arising

32、from sheet micro-structure , the effective minimum physical pixel resolution must not go below 0.002 mm2. 6.1.2 Analyzer: An analyzer incorporating “Equivalent Black Area” (EBA) calculations and using a technique called the “visual impact parameter” (see (1) and Appendix A.1). This parameter permits

33、 the system to perceive dirt in the same manner as would a human judge. 6.1.3 The certified calibration plates must be matte and have at least one solid white area and a solid black area. There are to be two other image areas containing a minimum of 16 dots each with a Yc/2value difference to their

34、background of 25% and 55%. Each set of certified calibration plates is numbered and provided with a calibration certificate containing the correction factors for the Yc/2 reflectance of the dots. Additionally the certified calibration plates must meet the specifications in Appendix A.2. These plates

35、 are available from TAPPI. NOTE 3: It is known that large amounts of fluorescence in paper can cause possible problems with the calibration or measurement with this method. However, that effect will be normally minimal since the reflectance values are measured at the Yc/2value, not at 457 nm for bri

36、ghtness. 6.2 Calibration: Turn on the light source. Allow the equipment to warm up and adjust the hardware settings according to the instructions or recommendations. If there is an adjustable focus on the detector, verify that the calibration plate image is sharply focused. The system will have reac

37、hed a steady state condition when five consecutive G.L. readings are within 2% of each other. 6.2.1 Contrast calibration: Place the calibration plate with the greatest contrast flat on the stage. If a device is used to hold a sample flat on the stage, then this same device must be used to hold the c

38、alibration plate flat. 6.2.1.1 Zero adjust: With the black square in the field of view, scan the black area on the plate, adjust the instrument to report a value of not less than 9 out of 255 gray levels or 3.5% of the full gray scale (see Note 4). Successive scans of the black area must give result

39、s within 0.4% G.L. values. 6.2.1.2 Span adjust. With the white square in the field of view, scan the white area on the plate, adjust the instrument to report a value not greater than 220 out of 255 gray levels or 86.3% of the full gray level scale (see Note 5). Successive scans of the white area mus

40、t give results within 0.4% G.L. values A minimum of 200 G.L. resolution between the black and white squares is recommended and a minimum of 170 G.L. is required. The gray level scale must be precise enough that each gray level corresponds to a step of not more than 0.5% reflectance units. NOTE 4: As

41、 calibration plates age, there may be a loss Yc/2reflectance The Yc/2 must be checked at least annually. If the minimum resolution falls below the required 170 G.L., then the calibration plates must be replaced. NOTE 5: The Yc/2%-reflectance and G.L. are linearly related such that 1% Yc/2= 2.55 G.L.

42、 To determine the G.L value of the black and white calibration plates, multiply the % Yc/2reported on the certificate by 2.55 provided with the set of calibration plates. 6.2.1.3 Repeat these two adjustments iteratively until both specifications are achieved. 6.2.2 Equivalent black area calibration:

43、 Measure each of the calibration plates. Verify that all 16 dots are detected and that the EBA results measured and reported agree within 10% of the average of all 16 dots to those determined from the data supplied with the certified calibration plates. To calculate the EBA of the dots on the plates

44、, multiply the nominal area as stated in the specifications in Appendix A.2 by the corrected contrast difference reported on the certificates provided with the plates. If they do not match, then check the hardware and/or the condition of the T 563 om-15 Equivalent Black Area (EBA) and count of visib

45、le / 4 dirt in pulp, paper and paperboard by image analysis calibration plates. If necessary, verify the correct operation of the equipment with the manufacturer for its adherence to this standard. NOTE 6: Due to digitization, measurement of the smallest dots on the lowest contrast plate at the mini

46、mum resolution prescribed in this method may give variation greater than 10% from the actual EBA when individual dots are evaluated for verification. Verification should be done by using the average EBA of all 16 dots on a plate. 6.3 Maintenance: Follow the manufacturers instructions regarding the e

47、quipment maintenance. 6.3.1 The calibration plates should be stored in the dark or in a black plastic envelope to prevent discoloration and loss of contrast. They should be cleaned DRY to remove dust or lint. Avoid scratching the surface as this may cause the plates to be out of specification. Perio

48、dically measure the Yc/2value of the white square. If the calibration plates fall outside the specifications given in Appendix A.2, then they must be replaced. 6.3.2 Unless the ambient light changes, or the hardware settings have changed, it is not necessary to recalibrate the hardware for a particu

49、lar analysis. It should be noted that, with time, light sources age and hence, there may be a loss of intensity. Thus, full calibration checks and hardware adjustments must be made as frequently as specified by the manufacturer. 7. Sampling and test specimens 7.1 Sample the paper or paperboard in accordance with TAPPI T 400 “Sampling and Accepting a Single Lot of Paper, Paperboard, Containerboard, or Related Product.” 7.2 Paper and paperboard: From each test unit, select ten or more sheets having a total exposed area (both sides) of at least 10 m2. Keep the s