Frame Grabber Enables High-Speed Profiling

Felicia A. Piacentino

Photonic component manufacturers depend on the accuracy and speed of optical metrology systems for the cost-efficient production of microelectromechanical system (MEMS) devices, thick films, optics, ceramics and advanced materials. These measurement systems also are useful for developing inspection standards and for research and development firms working to improve optical components.

Optical profilers conduct surface inspections that yield the information necessary to perform this work by highlighting defects, measuring dimensions and evaluating device quality.

Optical profilers can generate false-color height maps of photonic components and other devices, such as this MEMS micromotor, to reveal surface qualities and other attributes. The arrows represent the micromotor's electrical connections. Courtesy of CNRI MEMS Exchange.

Using white-light interferometry, the profiler generates a pattern of interference fringes, which is used to map the height of each point of a surface with subnanometer resolution. This high-resolution three-dimensional map reveals roughness, steps, topography and other surface features. Because the information is obtained in-line under high-speed production conditions, it is critical that the profiler's frame grabber be as fast and reliable as the system itself. The frame grabber must acquire 10 to 10,000 sequential frames, and each frame has to be captured without fail.

In designing its Wyko series of optical profilers, Veeco Instruments Inc. set out to find a frame grabber that met these performance requirements and that also was flexible enough to accommodate a range of system capabilities and CCD cameras.

The company chose a PCI-compatible frame grabber that acquires a series of 640 x 480-pixel frames at a scanning rate of 100 µm/s and at speeds up to 60 fps. The device, the PCDig from Coreco Imaging Inc., connects to the CCD camera via a 32-bit differential interface and transfers images directly to system memory at a rate of 120 MB/s. This frees the processor to perform data analysis and database logging for faster measurement sequences.

The device has proved fast and accurate, said Colin Farrell, product manager for the optical profilers, "Having a single frame grabber that works with all Wyko camera options and all system performance specifications simplifies and reduces the cost of inventory, manufacturing and support."