Geller Traceable Micro Ruler Model MR-1 Certified Reference Sample
Geller Traceable Micro Ruler™ Model MR-1 Certified Reference Sample:
Traceable rulers are required under ISO and QS-9000 and ISO-17025 quality programs. Geller MicroÅnalytical Laboratory introduces the Micro-Ruler MR-1, a metric dimensional calibration product that follows the very successfulMRS-3 and MRS-4 magnification reference standards. These provide traceable pitch patterns as small as ½µm for magnification determination up to 200,000X. One significant use of the MR-1 is to measure magnified images to determine absolute magnification. We offer the MR-1 only as a certified reference material (a traceable standard) it is the responsibility of the end user to determine when, and if, recertification is required.
E1951-98 Standard guide for calibrating reticles and light microscope magnifications
This guide covers methods for calculating and calibrating light microscope magnifications, photographic magnifications, video monitor magnifications, grain size comparison reticles, and other measuring reticles. Reflected light microscopes are used to characterize material microstructures. Many materials engineering decisions may be based on qualitative and quantitative analyses of a microstructure. It is essential that microscope magnifications and reticle dimensions be accurate. Not everyone has the need and the budget for a "certified ruler" and an alternative for a much lower price could be the PEAK™ glass scales.
The calibration using these methods is only as precise as the measuring devices used. It is recommended that the stage micrometer or scale used in the calibration should be traceable to the National Institute of Standards and Technology (NIST) or a similar organization.
The MR-1 is fabricated by using highly accurate semiconductor fabrication equipment. The pattern is anti reflective chromium (30nm of CrO2 over 70nm of Cr) over soda-lime glass. The overall size is .25mm X 180mm X 3 mm thick. The linear expansion coefficient is 9 X 10-6 PPM/°C. Over its full 150 mm length the ruler will predictably change dimensions by 1.35µm/°C.
The MR-1 is labeled in mm. Its overall scale extends over 150 mm with 0.01mm increments. The ruler is designed to be viewed from either side as the markings are both right reading and mirror images. This allows the ruler marking to be placed in direct contact with the sample, avoiding parallax errors. Independent of the ruler orientation the scale can be read correctly. There is a common scale with the finest (0.01 mm) markings to read.
We measure and certify pitch (the distance between repeating parallel lines using center-to-center or edge-to-edge spacing. This is the only type of measurement that can be used to relate measurements from different microscopy techniques (see "Submicrometer Linewidth Metrology in Optical Microscopy", Nyysonen & Larrabee, Journal of the Research of the National Bureau of Standards, Vol. 92, No. 3, 1987). Linewidth measurements (the measurement of a single line or space width) can only be related if the same type of illumination is used as for the calibrating instrument since edge effects lead to uncertainty in the edge locations. Using pitch measurements, errors from edge-to-edge locations cancel as long as like positions are measured.
What is the measurement uncertainty?
The MR-1 ruler uncertainty is ± 0.5µm over the 0 - 10 mm distance and ± 2.5µm over the entire 150 mm length, as measured by the National Physical Laboratory (the NIST counterpart in the United Kingdom). Our in-house measurements will slightly degrade the uncertainties listed above.
What is included in the certification report?
The Micro-Ruler is currently under consideration to be added to our ISO-17025 scope. The report issued follows the ISO-17025 guidelines for certification and traceability. Included is the unique serial number engraved on the standard, certification data, recertification due date (5 year suggested interval), operator, instrumentation used, and actual pattern measurements along with a measure of total uncertainty. This report has satisfied 100% of our customer audits.