High-speed time-domain characterization method for polygon scanners

•A new time-domain characterization method for a polygon mirror scanner is proposed.•Temporal positions of scanned laser beams are measured with high-speed electronics.•As polygon mirrors are tested without disassembly, measurement speed is very fast.•Scanning errors due to rotary motion as well as angle irregularity can be measured.•The idea was experimentally demonstrated by measuring three polygon mirror samples. Two major advantages of polygon scanners over galvano scanners are their fast scanning speed and linear scanning motion. However, a polygon scanner has a fundamental problem associated with the irregularity of its structure due to unequal facet-to-facet angles. Conventional methods rely on geometrical measurements of the polygon mirror structure; though accurate, they are time-consuming and do not show other scanning errors in the real beam scanning action. We propose a simple and fast time-domain characterization method that can show the structural defects of a polygon mirror as well as other scanning jitter that exists only when it is in motion. A laser beam's optical power passing through a slit is measured using a fast detector and digitizer. By analyzing repeated pulse patterns in the data, we can estimate facet-to-facet angles and other scanning jitter of a polygon mirror. Our proposed method is experimentally demonstrated by measuring three polygon mirrors with 12 facets.