Nondestructive testing of diffusely reflective objects

A method of detecting a leak in a sealed package, comprising:

• a) illuminating the package with coherent light,
• b) causing light rays reflected from two distinct points on the package to enter an image sensor and to interfere with each other to form an interference pattern comprising two laterally sheared images, the interference pattern being detectable by the image sensor, and
• c) analyzing the interference pattern so as to determine relative displacements of said points,
• wherein step (b) is performed by reflecting one of said rays from a first mirror, and reflecting another of said rays from a second mirror.

Apparatus for nondestructive testing of diffusely reflective objects, comprising:

• a) a source of coherent light, positioned to illuminate a test object,
• b) an image sensor, the image sensor being connected to a computer for storing and processing images detected by the image sensor, and
• c) first and second mirrors, positioned to direct light, reflected from the object, to the image sensor,
• wherein the first mirror is partially reflective and wherein the second mirror is totally reflective, and wherein the second mirror is positioned behind the first mirror, relative to the object.

Apparatus for nondestructive testing of diffusely reflective objects, comprising:

• a) means for illuminating a test object with coherent light,
• b) means for detecting an image, the detecting means being connected to means for storing and processing images detected by the detecting means, and
• c) first an second mirrors, positioned to direct light, reflected from the object, to the detecting means,
• wherein the first mirror is partially reflective and wherein the second mirror is totally reflective, and wherein the second mirror is positioned behind the first mirror, relative to the object.