For dimensional researches and applications, the end standard measurements are the popular subjects in high precision standard systems or instruments. In general, the gauge blocks are the representative of the end standards. The universal measurement machines (UMM) are usually utilized for the dimensional length of gauge blocks. However, for measuring the dimensional lengths of test gauge blocks (TGBs), they should be compared with the same lengths of the master gauge blocks (MGBs). Thus, there are different lengths of the MGBs needed to be prepared and the measuring procedures are usually very time consuming. In order to lower the cost of procurement and maintenance of MGBs, a continuous end standard measurement system (CESMS) was built for many different test ranges of TGBs. The features of the CESMS included at least one gauge block, the LVDT probes for positioning, the real lengths of the TGBs measured from the display value of the laser interferometer, and total procedures controlled by automation software. All of these parts were integrated onto a large platform and its moving carriage could travel up to 1.2-meter in distance. Within these ranges, the CESMS could measure different dimensional lengths of the TGBs and many pieces at the same time. The CESMS utilized the laser interferometer to acquire the accurate display values between two ends when the LVDT probe was touched and triggered the automation software to record. Owing to the recommended radiation of laser head, the CESMS could be traced to the meter, SI unit. Furthermore, the experiment results showed that the comparison results of certificated gauge block at 800 mm suited for calibration certificate by PTB.
The pitch calibration by a single wavelength laser and Littrow configuration laser diffractometer was presented. The calibration system consists of a green He-Ne laser, a precision angular positioning state, a four-quadrant detector, a beam splitter, and some optics. The measurement principles was based on the Littrow configuation that the reflective diffraction beam coincides with the incident beam. The pitch value was determined by the diffraction angle α and laser wavelength λ. A pitch standard, with nominal value of 292 nm, was measured by a wavelength of 543 nm green He-Ne laser diffractometer. The average pitch value was 292.10 nm. According to the "Guide to the expression of uncertainty in measurement", the system uncertainty was evaluated. The error sources included laser wavelength, refractive index of air, angular state, temperature, and coefficient of thermal expansion. The expanded uncertainty was 0.03 nm at a confidence level of 95% and 15 degrees of freedom. The main contributor of uncertainy was the positioning deviation of angular stage. Although the laser diffractometer had a high-accuracy ability, the measurement capability of Laser diffractometer was limited by the laser wavelength. The pitch p should be large than a half of laser wavelength.