Minute step measuring method

A minute step measurement method, comprising forming a laser spot on an object by condensing light from a laser light source, condensing light beams from said object on an end face of a double-mode waveguide, branching light propagating in said double-mode waveguide into two channel waveguides, detecting two light beams respectively emerging from said two channel waveguides, and measuring a minute step existing on said object, using at least one of a signal of a difference and a signal of a sum of two signals corresponding to said two light beams detected,

• wherein when W.sub.a is a signal of said sum when said laser spot is located on one of two flat portions at opposite sides of said step, W.sub.b is a signal of said sum when said laser spot is located on the other flat portion, W is a signal of said sum when a center of said laser spot becomes coincident with a center of said step, S is a signal of said difference, and R is a constant determined depending upon a device, said measuring includes obtaining a phase difference .phi. in accordance with at least one of the following two equations:
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A minute step measurement method, comprising forming a laser spot on an object by condensing light from a laser light source, condensing light beams from said object on an end face of a double-mode waveguide, branching light propagating in said double-mode waveguide into two channel waveguides, detecting two light beams respectively emerging from said two channel waveguides, and measuring a minute step existing on said object, using a signal of a difference of two signals corresponding to said two light beams detected,

• wherein said laser spot is formed on said object so that a center of said laser spot is located at a center of said step, a phase difference between an even mode and an odd mode excited in said double-mode waveguide is adjusted, and said step is measured based on an adjustment amount of said phase difference between the even mode and the odd mode when an absolute value of said signal of a difference becomes maximum or minimum.

A minute step measurement method, comprising forming a laser spot on an object by condensing light from a laser light source, condensing light beams from said object on an end face of a double-mode waveguide, branching light propagating in said double-mode waveguide into two channel waveguides, detecting two light beams respectively emerging from said two channel waveguides, and measuring a minute step existing on said object, using a composite signal of two signals corresponding to said two light beams detected,

• wherein said laser spot is formed on said object so that a center of said laser spot is located at a center of said step, a phase difference between an even mode and an odd mode excited in said double-mode waveguide is adjusted, and said step is measured based on an adjustment amount of said phase difference between the even mode and the odd mode when an absolute value of said composite signal becomes maximum or minimum.