Press Release Summary:
Providing part-per-billion laser frequency stability, Model RLE20 uses fiber optics to deliver laser light directly to measurement axis, eliminating need for remote beam splitters, benders, and adjustable mounts. System provides positional output signals in differential digital RS422 and 1 Vpp sine/cosine formats. Digital output signals provide resolutions up to 10 nm, while analog signals can be used with RPI20 parallel interface to provide resolution of 40 picometers.
Original Press Release:
New RLE20 Fiber-Optic Laser Encoder Introduces Picometer Resolution, Differential Measurement, and Part-Per-Billion Laser Frequency Stability
Alignment of just two components forms axis positioning system, allowing exceptional application flexibility and installation ease
September 2005 - New from Renishaw, the RLE20 fiberoptic laser encoder system converts the laser interferometer from a complex scientific instrument into a simple production solution offering picometer resolution, differential measurements and part-per-billion laser frequency stability. Key to this transformation is the use of fiber-optics to deliver the laser light directly to the measurement axes, eliminating the requirement for multiple remote beam splitters, benders and adjustable mounts.
The RLE20 interferometer system and associated components provide sub-nanometer non-linearity and resolution capability of 38 picometers, making fiber-optic launch a solution for precision motion system manufacturers and semiconductor equipment OEMs to ever-tightening requirements for wafer inspection, lithography and other yield enhancement tools.
The RLE20 system benefits from the same system architecture and application flexibility as the established RLE10 with a laser unit being connected to a detector head by a 3 m fiber-optic cable. By launching the laser light through fiber-optics, only two components need to be aligned to form a complex axis positioning system, leading to dramatic reduction in installation time and opportunity to reduce equipment footprint.
All Renishaw RLE laser systems provide positional output signals in differential digital RS422 and/or 1Vpp sine/cosine formats. Digital output signals provide resolutions of up to 10 nm, while analog signals can be used in conjunction with Renishaw's RGE interpolators or a new RPI20 parallel interface to provide resolutions of 0.39 nanometers and 40 picometers respectively.
The RPI20 parallel interface interpolates sinusoidal inputs by a factor of 4096 and produces 36-bit parallel position output data. Used with a double pass interferometer (with optical resolution of 158 nm) the RPI20 can produce output resolutions down to 38 picometers at velocities up to 1m/sec, overcoming velocity restrictions and bandwidth limitations with conventional methods.
Easily integrated into bus-based architectures, each RPI20 board contains a switch pack allowing the interface to be allocated a unique address and multi-axis systems to be configured with up to seven axes. The switch pack also allows user selection of the output resolution (LSB) - 38, 77, 154 and 309 picometers for double-pass plane-mirror interferometer, and 77, 154, 309 and 618 picometers for single-pass, retroreflector interferometer.
As with any laser interferometer system, when using an RLE system in a non-vacuum environment or an applications where it is not possible to reference the system against a known distance, some form of refractive index compensation is required in order to maintain accuracy under fluctuating environmental conditions. (Interferometric measurement is based on the wavelength of laser light. Changes in air temperature, pressure and humidity affect its refractive index, hence the wavelength of any laser light traveling through it.) To counter refractive index changes, Renishaw offers the RCU10 compensation system. Taking readings from the RLE system and environmental data from its sensors, the RCU10 modifies 'raw' position feedback signals before supplying corrected data to the motion controller.
Renishaw's comprehensive range of flexible interferometer solutions is further enhanced by a comprehensive 24-month warranty.
For more information on Renishaw's encoders, contact Howard Salt, Business Manager, Encoder systems, Renishaw Inc., 5277 Trillium Boulevard, Hoffman Estates, IL 60192. Phone 847-286-9953; fax 847-286-9974. Email: firstname.lastname@example.org
For a detailed look at other productivity enhancements for metrology, linear and rotary position feedback, and machine tool calibration, visit Renishaw's web site at: http://www.renishaw.com/encoders.
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