Abstract

A high-resolution optical position encoder is described that consists of a scale as encountered in a standard moiré-based system, a simple imaging system with stabilized magnification and a novel segmented phase detector integrated circuit. Compared with encoder systems of comparable resolution and accuracy, the encoder presented offers large mechanical tolerances in the alignment of the reading head to the scale, while an interpolation accuracy of better than 0.1 µm is preserved. The system is especially well suited for high-resolution linear encoders as well as for the cost-effective fabrication of compact high-resolution rotary encoders.

© 1997 Optical Society of America

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References

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  1. A. R. Luxmoore, ed., Optical Transducers and Techniques in Engineering Measurement (Applied Science Publishers, London, 1983), Chap. 3, pp. 61–108.
  2. K. Engelhardt, P. Seitz, “Absolute, high-resolution optical position encoder,” Appl. Opt. 35, 201–208 (1996).
    [Crossref] [PubMed]
  3. Baumer Electric AG, Frauenfeld, Switzerland, Fax. +41-52-7281144.
  4. Orbit Semiconductor Inc., 1230 Bordeaux Drive, Sunnyvale, Calif. 94089.
  5. LCS250-5 OEM Laser Interferometer, Intop Precision Engineering, D-88699 Frickingen, Germany.

1996 (1)

Appl. Opt. (1)

Other (4)

Baumer Electric AG, Frauenfeld, Switzerland, Fax. +41-52-7281144.

Orbit Semiconductor Inc., 1230 Bordeaux Drive, Sunnyvale, Calif. 94089.

LCS250-5 OEM Laser Interferometer, Intop Precision Engineering, D-88699 Frickingen, Germany.

A. R. Luxmoore, ed., Optical Transducers and Techniques in Engineering Measurement (Applied Science Publishers, London, 1983), Chap. 3, pp. 61–108.

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Figures (6)

Fig. 1
Fig. 1

Cartesian coordinate system connected to a linear scale and angular misalignments of an encoder head against the scale.

Fig. 2
Fig. 2

Schematic diagram of the high-resolution, absolute optical position encoder system. CNC, computer numerical control.

Fig. 3
Fig. 3

Construction principle of the novel SFPD.

Fig. 4
Fig. 4

SEM of the fabricated CMOS photo-ASIC with the SFPD.

Fig. 5
Fig. 5

Position encoder output at various levels of yaw of the encoder head to the scale. The quadrature signal is displayed as a Lissajous figure where 2π equals one period of the scale of 20 µm (a) obtained with the FPD that consists of an array of four sinusoidally shaped photodiodes and (b) obtained with the SFPD.

Fig. 6
Fig. 6

Linearity of the encoder system at an angular misalignment of yaw β = 4 mrad: The acquired encoder position is measured against the position value acquired with a laser interferometer for both types of phase detectors. With the SFPD the average interpolation error is ∼7 times lower than with the FPD.

Tables (1)

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Table 1 Properties and Mounting Tolerances of the Novel High-Resolution Linear Position Encoder with a SFPD

Equations (5)

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UPD1  UP1+UP4+UP5, UPD2  UP2+UP3+UP6, UPD3  UP1+UP4+UP2, UPD4  UP5+UP3+UP6.
Usin=UPD1-UPD2, Ucos=UPD3-UPD4.
Φ=arctanUsinUcos.
Usin=UP1-UP3-UP2-UP5,  Ucos=UP1-UP3+UP2-UP5.
ΔxFPD55.7±1.6βμmmrad,  ΔxSFPD8.3±0.2βμmmrad.

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