Abstract

A new, to our knowledge, design for a cylindrical-type diffractive optical encoder is proposed. The wave-front aberrations induced by the power of the rotation disk in this encoder can be canceled out completely. Wave-front-aberration cancellation and desensitization to the grating misalignment are achieved by means of positioning the virtual point source, which was induced by the cylindrical grating with respect to two sets of modified telescopes with a magnification ratio of one: 1× telescopes. For evaluating the performance envelope of this newly designed optical system a code v-based optical-design software program was adopted to simulate the performance of the optical system. From tolerance-analysis results it was found that this newly developed cylindrical encoder system has the capability to compensate for most aberrations and, in addition, possesses a high tolerance for optical-component misalignment. For verifying the performance of the developed system the cylindrical diffractive encoder system was cross-referenced with a Hewlett-Packard Model HP-5529 laser interferometer positioning signal. The experimental results confirm the merits of this newly developed cylindrical encoder.

© 1999 Optical Society of America

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References

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  1. T. Nishimura, K. Ishizuka, “Laser rotary encoder,” Motion Sept./Oct., 14 (1986).
  2. K. Ishizuka, T. Nishimura, O. Kasshara, “Encoder,” UK patentGB 2,185,314 (15July1987).
  3. K. Ishizuka, N. Kawasaki, “Encoder with high resolving power and accuracy,” U.S. patent5,146,085 (8September1992).
  4. D. K. Mitchell, G. Thorburn, “Apparatus for detecting relative movement wherein a detecting means is positioned in the region of natural interference,” U.S. patent5,486,923 (23January1996).
  5. S. Ishii, T. Nishimura, K. Ishizuka, M. Tsukiji, “Optical type encoder including diffraction grating for producing interference fringes that are processed to measure displacement,” U.S. patent4,912,320 (30July1990).
  6. O. P. Lausanne, “Diffraction photoelectric displacement measuring device,” U.S. patent4,938,595 (3July1990).
  7. S. Ichikawa, H. O. Kawasaki, “Diffraction-type optical encoder with improved detection signal insensitivity to optical grating gap variations,” U.S. patent4,943,716 (24July1993).
  8. K. Ishizuka, T. Nishimura, O. Kasahara, “Rotary encoder using reflected light,” U.S. patent5,036,192 (30July1991).
  9. W. W. Chiang, C. K. Lee, “Wavefront reconstruction optics for use in disk drive position measurement system,” U.S. patent5,442,172 (15August1995).
  10. Laser Rotary Encoder, (Canon, Inc., Lake Success, New York, 1996).
  11. B. Horwitz, “Diffractive technique to improve encoder performance,” Laser Focus World Oct.143–148 (1996).
  12. K. Iizuka, Engineering Optics (Kyoristsu Shuppan, Tokyo, 1983).
  13. code v User’s Manual (Optical Research Associates, 3280 East Foothill Boulevard, Pasadena, Calif., 1996).
  14. Laser and Optics Users Manual (Hewlett-Packard, 5651 West Manchester, Los Angeles, Calif., 1992).
  15. M. Dobosz, “New style probe with interferometric transducer for surface roughness and form profiling,” Opt. Eng. 33, 902–907 (1994).
    [CrossRef]
  16. C. T. Hsieh, “Theoretical design and experimental implementation of cylindrical diffractive optical encoders,” Ph.D. dissertation (National Taiwan University, Taipei, Taiwan, 1997).
  17. J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968).

1996 (1)

B. Horwitz, “Diffractive technique to improve encoder performance,” Laser Focus World Oct.143–148 (1996).

1994 (1)

M. Dobosz, “New style probe with interferometric transducer for surface roughness and form profiling,” Opt. Eng. 33, 902–907 (1994).
[CrossRef]

1986 (1)

T. Nishimura, K. Ishizuka, “Laser rotary encoder,” Motion Sept./Oct., 14 (1986).

Chiang, W. W.

W. W. Chiang, C. K. Lee, “Wavefront reconstruction optics for use in disk drive position measurement system,” U.S. patent5,442,172 (15August1995).

Dobosz, M.

M. Dobosz, “New style probe with interferometric transducer for surface roughness and form profiling,” Opt. Eng. 33, 902–907 (1994).
[CrossRef]

Goodman, J. W.

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968).

Horwitz, B.

B. Horwitz, “Diffractive technique to improve encoder performance,” Laser Focus World Oct.143–148 (1996).

Hsieh, C. T.

C. T. Hsieh, “Theoretical design and experimental implementation of cylindrical diffractive optical encoders,” Ph.D. dissertation (National Taiwan University, Taipei, Taiwan, 1997).

Ichikawa, S.

S. Ichikawa, H. O. Kawasaki, “Diffraction-type optical encoder with improved detection signal insensitivity to optical grating gap variations,” U.S. patent4,943,716 (24July1993).

Iizuka, K.

K. Iizuka, Engineering Optics (Kyoristsu Shuppan, Tokyo, 1983).

Ishii, S.

S. Ishii, T. Nishimura, K. Ishizuka, M. Tsukiji, “Optical type encoder including diffraction grating for producing interference fringes that are processed to measure displacement,” U.S. patent4,912,320 (30July1990).

Ishizuka, K.

T. Nishimura, K. Ishizuka, “Laser rotary encoder,” Motion Sept./Oct., 14 (1986).

K. Ishizuka, T. Nishimura, O. Kasahara, “Rotary encoder using reflected light,” U.S. patent5,036,192 (30July1991).

S. Ishii, T. Nishimura, K. Ishizuka, M. Tsukiji, “Optical type encoder including diffraction grating for producing interference fringes that are processed to measure displacement,” U.S. patent4,912,320 (30July1990).

K. Ishizuka, T. Nishimura, O. Kasshara, “Encoder,” UK patentGB 2,185,314 (15July1987).

K. Ishizuka, N. Kawasaki, “Encoder with high resolving power and accuracy,” U.S. patent5,146,085 (8September1992).

Kasahara, O.

K. Ishizuka, T. Nishimura, O. Kasahara, “Rotary encoder using reflected light,” U.S. patent5,036,192 (30July1991).

Kasshara, O.

K. Ishizuka, T. Nishimura, O. Kasshara, “Encoder,” UK patentGB 2,185,314 (15July1987).

Kawasaki, H. O.

S. Ichikawa, H. O. Kawasaki, “Diffraction-type optical encoder with improved detection signal insensitivity to optical grating gap variations,” U.S. patent4,943,716 (24July1993).

Kawasaki, N.

K. Ishizuka, N. Kawasaki, “Encoder with high resolving power and accuracy,” U.S. patent5,146,085 (8September1992).

Lausanne, O. P.

O. P. Lausanne, “Diffraction photoelectric displacement measuring device,” U.S. patent4,938,595 (3July1990).

Lee, C. K.

W. W. Chiang, C. K. Lee, “Wavefront reconstruction optics for use in disk drive position measurement system,” U.S. patent5,442,172 (15August1995).

Mitchell, D. K.

D. K. Mitchell, G. Thorburn, “Apparatus for detecting relative movement wherein a detecting means is positioned in the region of natural interference,” U.S. patent5,486,923 (23January1996).

Nishimura, T.

T. Nishimura, K. Ishizuka, “Laser rotary encoder,” Motion Sept./Oct., 14 (1986).

K. Ishizuka, T. Nishimura, O. Kasahara, “Rotary encoder using reflected light,” U.S. patent5,036,192 (30July1991).

K. Ishizuka, T. Nishimura, O. Kasshara, “Encoder,” UK patentGB 2,185,314 (15July1987).

S. Ishii, T. Nishimura, K. Ishizuka, M. Tsukiji, “Optical type encoder including diffraction grating for producing interference fringes that are processed to measure displacement,” U.S. patent4,912,320 (30July1990).

Thorburn, G.

D. K. Mitchell, G. Thorburn, “Apparatus for detecting relative movement wherein a detecting means is positioned in the region of natural interference,” U.S. patent5,486,923 (23January1996).

Tsukiji, M.

S. Ishii, T. Nishimura, K. Ishizuka, M. Tsukiji, “Optical type encoder including diffraction grating for producing interference fringes that are processed to measure displacement,” U.S. patent4,912,320 (30July1990).

Laser Focus World (1)

B. Horwitz, “Diffractive technique to improve encoder performance,” Laser Focus World Oct.143–148 (1996).

Motion (1)

T. Nishimura, K. Ishizuka, “Laser rotary encoder,” Motion Sept./Oct., 14 (1986).

Opt. Eng. (1)

M. Dobosz, “New style probe with interferometric transducer for surface roughness and form profiling,” Opt. Eng. 33, 902–907 (1994).
[CrossRef]

Other (14)

C. T. Hsieh, “Theoretical design and experimental implementation of cylindrical diffractive optical encoders,” Ph.D. dissertation (National Taiwan University, Taipei, Taiwan, 1997).

J. W. Goodman, Introduction to Fourier Optics (McGraw-Hill, New York, 1968).

K. Iizuka, Engineering Optics (Kyoristsu Shuppan, Tokyo, 1983).

code v User’s Manual (Optical Research Associates, 3280 East Foothill Boulevard, Pasadena, Calif., 1996).

Laser and Optics Users Manual (Hewlett-Packard, 5651 West Manchester, Los Angeles, Calif., 1992).

K. Ishizuka, T. Nishimura, O. Kasshara, “Encoder,” UK patentGB 2,185,314 (15July1987).

K. Ishizuka, N. Kawasaki, “Encoder with high resolving power and accuracy,” U.S. patent5,146,085 (8September1992).

D. K. Mitchell, G. Thorburn, “Apparatus for detecting relative movement wherein a detecting means is positioned in the region of natural interference,” U.S. patent5,486,923 (23January1996).

S. Ishii, T. Nishimura, K. Ishizuka, M. Tsukiji, “Optical type encoder including diffraction grating for producing interference fringes that are processed to measure displacement,” U.S. patent4,912,320 (30July1990).

O. P. Lausanne, “Diffraction photoelectric displacement measuring device,” U.S. patent4,938,595 (3July1990).

S. Ichikawa, H. O. Kawasaki, “Diffraction-type optical encoder with improved detection signal insensitivity to optical grating gap variations,” U.S. patent4,943,716 (24July1993).

K. Ishizuka, T. Nishimura, O. Kasahara, “Rotary encoder using reflected light,” U.S. patent5,036,192 (30July1991).

W. W. Chiang, C. K. Lee, “Wavefront reconstruction optics for use in disk drive position measurement system,” U.S. patent5,442,172 (15August1995).

Laser Rotary Encoder, (Canon, Inc., Lake Success, New York, 1996).

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Figures (15)

Fig. 1
Fig. 1

Wave-front aberration induced by a rotating disk.

Fig. 2
Fig. 2

(a) New design for a cylindrical-type diffractive optical encoder. Close-up views of a cylindrical diffractive optical encoder system for (b) a +1-order diffracted beam and (c) a -1-order diffracted beam.

Fig. 3
Fig. 3

Diagram of the optical simulation for a +1-order diffracted beam in which the designed grating pitch is 1.6 µm, the wavelength is 632.8 nm, and the radius of the rotation disk is 110 mm.

Fig. 4
Fig. 4

Diagram of the optical simulation for a -1-order diffracted beam in which the designed grating pitch is 1.6 µm, the wavelength is 632.8 nm, and the radius of the rotation disk is 110 mm.

Fig. 5
Fig. 5

Quality of the rms wave front of a +1-order returning beam for which the rms and the peak-to-valley wave-front errors are 0.005 and 0.025 wave, respectively.

Fig. 6
Fig. 6

Quality of the rms wave front of a -1-order returning beam for which the rms and the peak-to-valley wave-front errors are 0.005 and 0.025 wave, respectively.

Fig. 7
Fig. 7

Quality of the rms wave front versus the disturbance in the grating rotation.

Fig. 8
Fig. 8

Quality of the rms wave front versus the disturbance in the grating offset.

Fig. 9
Fig. 9

Offset of the diffracted beam in the x direction that was induced by a tilting disturbance about the y or the z axis. The offset of the diffracted beam is negligible in the x direction for cases of offset disturbance along the x, the y, and the z directions and for cases of tilt about the x axis.

Fig. 10
Fig. 10

Offset of the diffracted beam in the y direction (a) as induced by an offset disturbance along the y or the z direction and (b) as induced by a tilt disturbance about the x axis. Note that the offset of the diffracted beam in the y direction is negligible for cases of an offset disturbance along the x direction and for cases of tilt disturbance about the y or the z axis.

Fig. 11
Fig. 11

Tilt of the diffracted beam about the x axis that is induced by the tilt disturbance about the y or the z axis. The tilt of the diffracted beam about the x axis is negligible for cases of offset disturbance along the x, the y, or the z direction and for cases of tilting about the x axis.

Fig. 12
Fig. 12

Tilt of the diffracted beam about the y axis (a) as induced by an offset disturbance along the y or the z direction and (b) as induced by tilt disturbance about the x axis. Note that the tilt of the diffracted beam about the y axis is negligible for cases of offset disturbance along the x direction and for cases of tilt about the y or the z axis.

Fig. 13
Fig. 13

Diagram of the experimental setup of the cylindrical diffractive optical encoder.

Fig. 14
Fig. 14

Quadrature signals detected by the signal detector.

Fig. 15
Fig. 15

Experimental results for two sets of data: the proposed cylindrical diffractive optical encoder and the Hewlett-Packard Model HP-5529 laser interferometer.

Equations (8)

Equations on this page are rendered with MathJax. Learn more.

δ1=sin-1λp+dR+sin-1dR,
δ=12sin-1λp+dR+sin-1λp-dR.
L=sinπ/2-δsin αd+R1-cos θtan δ+R1-cos θsec δ,
δ2=sin-1λp-dR-sin-1dR
δ3=sin-1λp-dR-sin-1dR.
δ=12sin-1λp+dR+sin-1λp-dR.
L=sinπ/2-δsin αd+R1-cos θtan δ+R1-cos θsec δ.
δ4=sin-1λp+dR+sin-1dR,

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