Bernd R.; It is difficult to tell you with certainty how you should go about your application based on the limited information you provided. My answer is more general.
You need to come up with the criteria. You are calculating the area of a particle. Let say different subjects (i.e. particles) will have different areas. You need to establish a tolerance within which the result is acceptable. It can be as follow: on average, you know the area is 10 (square centimeters, inches, etc.) An area of 9.5 may be too small and 10.5 too big. You can set your thresholds in 9.6 and 10.4. Therefore, you will reject anything with an area below 9.6 or above 10.4. I hope this is of help. Regards; Enrique Vargas
