Abstract

A surface tester was developed for the VHD (video high-density disk) using an optical technique. A 10-μm diam beam from a laser diode irradiates the disk surface, and a photosensor detects the angle and the intensity of a reflected beam. Defects on the surface are found by observing changes in the photosensor signal. A microscopic examination of the disk surface revealed that the tester can detect defects larger than 10 μm. The tester classifies defects by their category and size and displays a defect map on a monitor screen. The data obtained are utilized for improving the VHD manufacturing process.

© 1988 Optical Society of America

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References

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  1. I. Morishita, M. Okumura, “Automated Visual Inspection Systems for Industrial Applications,” Proc. Acta Imeko, p. 17 (1982).
  2. J. M. Bennett, “Measurement of the rms Roughness, Autocovariance Function and Other Statistical Properties of Optical Surfaces Using a FECO Scanning Interferometer,” Appl. Opt. 15, 2705 (1976).
    [CrossRef] [PubMed]
  3. D. Y. Lou, A. Martinez, D. Stanton, “Surface Profile Measurement with a Dual-Beam Optical System,” Appl. Opt. 23, 746 (1984).
    [CrossRef] [PubMed]
  4. M. Born, E. Wolf, Principle of Optics (Pergamon, New York, 1975), p. 396.
  5. G. Bouwhuis, J. J. M. Braat, “Video Disk Player Optics,” Appl. Opt. 17, 1993 (1978).
    [CrossRef] [PubMed]
  6. D. G. Kocher, “Automated Foucault Test for Focus Sensing,” Appl. Opt. 22, 1887 (1983).
    [CrossRef] [PubMed]

1984 (1)

1983 (1)

1982 (1)

I. Morishita, M. Okumura, “Automated Visual Inspection Systems for Industrial Applications,” Proc. Acta Imeko, p. 17 (1982).

1978 (1)

1976 (1)

Bennett, J. M.

Born, M.

M. Born, E. Wolf, Principle of Optics (Pergamon, New York, 1975), p. 396.

Bouwhuis, G.

Braat, J. J. M.

Kocher, D. G.

Lou, D. Y.

Martinez, A.

Morishita, I.

I. Morishita, M. Okumura, “Automated Visual Inspection Systems for Industrial Applications,” Proc. Acta Imeko, p. 17 (1982).

Okumura, M.

I. Morishita, M. Okumura, “Automated Visual Inspection Systems for Industrial Applications,” Proc. Acta Imeko, p. 17 (1982).

Stanton, D.

Wolf, E.

M. Born, E. Wolf, Principle of Optics (Pergamon, New York, 1975), p. 396.

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Figures (9)

Fig. 1
Fig. 1

VHD surface and stylus close-up.

Fig. 2
Fig. 2

Microscopic photographs of typical defects on a VHD.

Fig. 3
Fig. 3

Optical head of the VHD tester.

Fig. 4
Fig. 4

Laser beam behavior around the elevation irregularity.

Fig. 5
Fig. 5

Output signals from the position sensor.

Fig. 6
Fig. 6

Signal curve drawings simplified to point up defect features.

Fig. 7
Fig. 7

Signal processing circuit block diagram.

Fig. 8
Fig. 8

VHD tester block diagram.

Fig. 9
Fig. 9

Examples of test results.

Equations (5)

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

I r = I a + I b .
p = f tan θ ,
p = α I a - I b I a + I b ,
θ = α f I a - I b I a + I b .
d = 1.22 f λ D ,

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