A method and apparatus for inspecting a test object with a non-planar feature. A pattern of light is transmitted from a first array of optical fibers associated with a sensor structure onto a surface of the test object at a location of the non-planar feature. The pattern of light is configured to cause sound waves in the test object when the pattern of light encounters the test object. A response to the sound waves is detected using a second array of optical fibers associated with the sensor structure. A determination is made as to whether an inconsistency is present in the test object at the location of the non-planar feature from the response to the sound waves detected using the second array of optical fibers.