On May 22-24, Dr. SenHan, the Chairman of H&L Instruments,  went to Beijing to attend the International Symposium on Optoelectronic Technology and Application (OTA 2018) International Conference. This conference brings together key researchers, engineers and scientists from all over the world in the field of optoelectronics. Dr. SenHan chaired a conference on the theme of "Optical Precision Manufacturing, Testing Technology and Application" and gave an invitation report entitled "Absolute Measurement of Super-Smooth Surface".