Abstract

The task is to learn the phases of real positive intensity fringes from an optical testing interferometer. The introduction of substantial tilt into the interferometer establishes a field of finely spaced fringes that serve as a spatial heterodyne carrier. Sequential pixel values from a TV video signal of the picture are distributed among three separate signal channels, every third pixel going to the same channel. The distribution rate is set at ~3 pixels/fringe so that each channel senses one phase of a three-phase stroboscope or moiré. Complex weighting of the channel signals eliminates the common mode to provide in-phase and quadrature analog fringe signals. A direct analog-to-digital arctangent converter, with that analog signal pair as input, provides 4-bit (1/16-cycle resolution) fringe phase at a 5-MHz sampling rate. The converter is coupled to a turns counter that automatically registers unwrapped phase. The similarity of the signals to ntsc color TV encoding is noted along with certain other applications.

© 1983 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. M. Takeda, H. Ina, S. Kobayashi, J. Opt. Soc. Am. 72, 156 (1982).
    [CrossRef]
  2. L. Mertz, Appl. Opt. 22, 1530 (1983).
    [CrossRef] [PubMed]
  3. L. N. Mertz, Appl. Opt. 16, 812 (1977).
    [CrossRef] [PubMed]

1983

1982

1977

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (8)

Fig. 1
Fig. 1

Signal distributor with three-phase output.

Fig. 2
Fig. 2

Three- to two-phase converter.

Fig. 3
Fig. 3

Four-bit Gray encoded analog to digital arctangent converter.

Fig. 4
Fig. 4

Gray to binary code converters.

Fig. 5
Fig. 5

Oscilloscope traces of video (upper traces) and concurrent arctangent displays (lower traces) (see text for details).

Fig. 6
Fig. 6

Further oscilloscope traces showing principal values of arctangent (A) and (C) and unwrapped phase (B) and (D).

Fig. 7
Fig. 7

Filter transfer function.

Fig. 8
Fig. 8

Fringe encoded photo of Orion nebula suitable for fringe-pattern analysis. Phase shifts of fringes correspond to Doppler shifts of source regions.

Tables (1)

Tables Icon

Table I Phase Error in Cycles as a Function of Spatial Frequency and Phase

Equations (5)

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

Z = A exp ( - 2 π i / 3 ) + B exp ( 0 i ) + C exp ( + 2 π i / 3 )
I = ( - 1 / 2 ) A + B + ( - 1 / 2 ) C ,
Q = ( - 3 / 2 ) A + ( + 3 / 2 ) C .
T = - ( 1 / 2 ) cos ( - f ) + 1 - ( 1 / 2 ) cos ( + f ) - ( 3 / 2 ) sin ( - f ) + ( 3 / 2 ) sin ( + f ) = 1 + 2 sin ( f - 30 ° ) .
( 3579545 / 15734.264 ) ( 0.82 ) 186.55 cycles

Metrics