Ultrafast dark-field surface inspection with hybrid-dispersion laser scanning

Journal Article · Mon Jun 23 00:00:00 EDT 2014 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4885147· OSTI ID:22303836

Yazaki, Akio ^[1]; Kim, Chanju ^[1]; Chan, Jacky ^[1]; Mahjoubfar, Ata ^[1]; Goda, Keisuke ^[1]; Watanabe, Masahiro ^[2]; Jalali, Bahram ^[1]

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1. Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States)
2. Yokohama Research Laboratory, Hitachi, Ltd., Kanagawa 244-0817 (Japan)

High-speed surface inspection plays an important role in industrial manufacturing, safety monitoring, and quality control. It is desirable to go beyond the speed limitation of current technologies for reducing manufacturing costs and opening a new window onto a class of applications that require high-throughput sensing. Here, we report a high-speed dark-field surface inspector for detection of micrometer-sized surface defects that can travel at a record high speed as high as a few kilometers per second. This method is based on a modified time-stretch microscope that illuminates temporally and spatially dispersed laser pulses on the surface of a fast-moving object and detects scattered light from defects on the surface with a sensitive photodetector in a dark-field configuration. The inspector's ability to perform ultrafast dark-field surface inspection enables real-time identification of difficult-to-detect features on weakly reflecting surfaces and hence renders the method much more practical than in the previously demonstrated bright-field configuration. Consequently, our inspector provides nearly 1000 times higher scanning speed than conventional inspectors. To show our method's broad utility, we demonstrate real-time inspection of the surface of various objects (a non-reflective black film, transparent flexible film, and reflective hard disk) for detection of 10 μm or smaller defects on a moving target at 20 m/s within a scan width of 25 mm at a scan rate of 90.9 MHz. Our method holds promise for improving the cost and performance of organic light-emitting diode displays for next-generation smart phones, lithium-ion batteries for green electronics, and high-efficiency solar cells.

• OSTI ID: 22303836
• Journal Information: Applied Physics Letters, Vol. 104, Issue 25; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CONFIGURATION
CURRENTS
DEFECTS
DETECTION
DISPERSIONS
ELECTRIC BATTERIES
ELECTRIC UTILITIES
FILMS
GAS UTILITIES
INSPECTION
LASERS
LIGHT EMITTING DIODES
LITHIUM IONS
MAGNETIC DISKS
MANUFACTURING
PULSES
SOLAR CELLS
SURFACES
VISIBLE RADIATION