Magnescale Co., Ltd. || Magnescale(R), Laserscale(R), Digital Gauge

Oct. 20th, 2014

Self-compensating Absolute Laserscale
Next generation high accuracy Laserscale with unique algorithm to detect absolute position

Magnescale Co., Ltd. has developed a new Laserscale which offers detection of absolute position with self-compensating function. This newly developed technology is based on two elements; a scanning head which optically reads a holographic scale (made by unique exposure technology creating an ultra-fine pitch grating) and an interpolator system having an algorithm for detecting absolute position with self-compensating function. This technology enables ultra-high accuracy measurement, and realizes 0.2 μm/500 mm accuracy and 0.5nm/mm linearity.

The new encoder is expected to enhance accuracy and speed of semiconductor manufacturing equipment and semiconductor inspection equipment. This encoder can also be used for calibration at manufacturing and maintenance of machine tool.

The technical details will be announced at JIMTOF2014 at Tokyo Big Sight (Oct. 20 to Nov. 4, 2014)

Self-compensating two dimensional absolute Laserscale system

The newly developed self-compensating type absolute Laserscale consists of the following technologies; an ultra-high accuracy scale with specified grating pitches distribution, two scanning heads, and an interpolator which detects absolute position from relative phase information of two heads. The values of displacement detected by two heads in short interval are not the same at the different position due to the grating wavelength distribution of the scale. Using the algorithm, the interpolator identifies absolute position through conversion formula after calculating the difference of displacements by highly accurate interpolation of signals from the 2 scanning heads. Absolute Laserscale can realize cumulative accuracy of 0.2 µm over whole range of 600 mm x 500 mm scale through compensation on incremental signal from one head by using the difference between the actual absolute position information and ideal wavelength distribution which was measured in advance and stored in memory. When the absolute Laserscale is powered on, the scale and scanning head must be relatively displaced for a very short range in order to detect the absolute position information. However, it is not necessary to move to the reference position, unlike other conventional encoders.

Two dimensional holographic scale with ultra-fine wavelength distribution






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