What Is Isochromatic Fringe Pattern?

Isochromatic fringes are lines of constant principal stress difference, (σP - σQ). If the source light is monochromatic these appear as dark and light fringes, whereas with white light illumination coloured fringes are observed.

What is the difference between isochromatic and Isoclinic fringes?

Isochromatic fringes are obtained using monochromatic light, whereas isoclinic fringes are obtained using white light. Isoclinic fringes are obtained when the principal stress direction coincides with the polarisation of the polariser; isochromatic fringes are lines of constant stress difference.

What are Isoclinics and Isochromatics?

Isoclinics are the loci of the points in the specimen along which the principal stresses are in the same direction. Isochromatics are the loci of the points along which the difference in the first and second principal stress remains the same.