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The world of super-resolution is going further than 1nm -High-resolution scale with signal pitch of approx. 138nm outperforms light wave interferometer systems-

Laserscale easily achieves measurement and control with ultra high resolution of better than 1nm. A sinusoidal wave (approximately 138nm signal pitch) is generated using the grating interference method by utilizing a holographic scale with high diffraction efficiency and a high resolution head. The BS series offers strong resistance to disturbance by air pressure or current, and is easy to install. Signal distortion, in principle, remains minimal at a high S/N ratio. Resolution of 17pm can be achieved using our automatic compensation interpolator.

Ultra-high resolution

Volume holography technology of Laserscale achieves high diffraction efficiency to generate a high S/N signal and a strong output signal.

Best in class 17pm resolution

One count movement of the 0.55μm holographic grating pitch diffracts the signal to 4 periods. The 1/4 of the original signal results in a signal of approximately 0.138μm. Using our interpolator, this signal can achieve 17pm resolution.

Ultra-high resolution and high response speed

Our grating interference principle linear encoders offer a signal pitch of approximately 0.14μm. That is 1/140th of a conventional linear encoder with a 20μm signal pitch. Using our interpolator, 17pm resolution and a response speed of up to 400mm/s is achievable.

Principle

The semiconductor laser beam is split by a polarized light beam splitter into S and P polarized light beams, then diffracted through a volume holographic grating with very high diffraction efficiency. The two diffracted beams pass through separate 1/4-wavelength plates to a mirror, which reflects the beams back through the plates. This process converts the S polarized beam to P polarized light and the P polarized beam to S polarized light. The two beams are diffracted again through the volume holographic grating, then super-positioned by the polarized light beam splitter to create interference. All interference travels to the photo-detector side due to conversion of the polarization direction.
Since double diffraction adds +2 Kx and -2 Kx phases to each beam, the interference is subject to four light-dark inversion cycles for each grating scale of movement. Thus a grating pitch of 0.55 μm produces a signal pitch of 0.55/4 = approx. 0.138 μm. This detecting optics is free from fluctuations and change in air pressure, since the light path of both left and right changes identiacally even with the change in wavelength of the optical source. Repeatability and returning errors do not occur in principle.