Abstract
In automated photoelasticity, there are some advantages in using white light; however, the theory underlying many such systems, namely phase stepping, is based on monochromatic light. The effect of using white light has been investigated both by experiment and by a simulation of a polariscope. The simulation has been validated and used to explore the use of bandwidth filters to control the errors caused by using white light. These errors were found to be dependent on the form of the spectrum of the light and to be large for high fringe orders.
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Abbreviations
- α:
-
relative phase retardation
- C m ,C λ :
-
stress-optic coefficient at matching wavelength, and other wavelengths
- ε:
-
quarter-wave plate error
- f :
-
fringe constant (Nm−1/fringe)
- F(λ):
-
response curve of monochromatic CCD camera
- I 0 :
-
light intensity when all the fast axes of the polariscope are parallel to each other
- I 1,...,I 6 :
-
light intensity for phase steps 1 to 6
- I i :
-
light intensity in ideal conditions
- I m :
-
stray light intensity
- (I)λ, (I)w :
-
light intensity: nonmatching monochromatic light source, white light source
- λ, λ m :
-
wavelength (nm), matching wave-length for the quarter-wave plates (nm)
- N, N m :
-
fringe order at matching wavelength
- θ:
-
isoclinic angle
- ρ1,ρ2,ρ3 :
-
angles between the fast axes of the first quarter-wave plate, second quarter-wave plate and analyzer to the fast axis of the polarizer
- S λ :
-
combined response of light source and monochromatic camera
- σ1,σ2 :
-
principal stresses
- t :
-
thickness of the specimen
- T(λ):
-
products of transmission ratio of every element in the polariscope
- ξ1,ξ2 :
-
retardation caused by first and second quarter-wave plate, respectively
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Ji, W., Patterson, E.A. Simulation of errors in automated photoelasticity. Experimental Mechanics 38, 132–139 (1998). https://doi.org/10.1007/BF02321656
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DOI: https://doi.org/10.1007/BF02321656