High-precision absolute linear encoder based on a standard calibrated scale

Oleg U. Lashmanov, Aleksandr S. Vasilev, Anna V. Vasileva, Andrei G. Anisimov, Valery V. Korotaev

Research output: Contribution to journalArticleScientificpeer-review

9 Citations (Scopus)


This paper presents the full research and development cycle of a high-precision absolute linear encoder based on a standard calibrated scale. Already available and used in industry standard scales of invar alloy were employed in the study. The scales have incremental indexes with 1 mm spacing intervals without an absolute code. However, the existing technical task is to measure the absolute position in the range of 2 m with accuracy less than 5 μm. For that, the developed encoder rationally combines magnetic measuring channel for the index numbering and an optical channel for the precise estimation of the encoder position. First, for the development, a simulation was performed to synthesize and analyze an image of an index. This image was used to develop a real-time double-threshold image processing algorithm to estimate the index position. Later the developed image processing algorithm was verified by preliminary testing and supported by a presented three-stage calibration procedure. The final measurements proved that the designed and developed encoder has the accuracy of 1.65 μm (3 standard deviations) at the speed up to 3 m/s. The possibility of use of standard calibrated scales with the presented encoder to solve existing and new industrial tasks forms the value of this paper. A possible use of the existing scales also provides unification and compatibility with conventional metrology equipment.

Original languageEnglish
Pages (from-to)226-234
Number of pages9
Publication statusPublished - 1 Jul 2018


  • Automatic positioning
  • High-precision measurements
  • Imaging encoder
  • Invar scale
  • Linear optical encoder

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