A defect detection device 10 includes: an excitation source 11 capable of being placed at any position on a surface of an inspection target object S, the excitation source 11 being configured to excite an elastic wave within the inspection target object S, the elastic wave being predominant in one vibration mode and propagating in a predetermined direction; an illumination unit (pulsed laser light source 13, illumination light lens 14) configured to perform stroboscopic illumination on an illumination area of the surface of the inspection target object by using a laser light source; a displacement measurement unit (speckle shearing interferometer 15) configured to collectively measure a displacement of each point in a front-back direction within the illumination area in at least three different phases of the elastic wave, by speckle interferometry or speckle shearing interferometry; and a reflected wave/scattered wave detector 16 configured to detect either one or both of a reflected wave and a scattered wave of the elastic wave, based on the displacement measured by the displacement measurement unit.

An optical system includes a collimated light source, a beam splitter, two mirrors and two lenses, a focus lens, and a detector. An initial light beam is generated by the light source and then separated by the beam splitter into a first light beam and a second light beam. The two mirrors respectively direct the first and second light beams on a sample with symmetrical paths and the two lenses focus the first and second light beam on the sample respectively. The first and second light beams are reflected from the sample and along the counterpart paths to the beam splitter. An interfered light beam is then generated by combining the reflected first and second light beams, and focused by a focus lens on a detector. A Dove prism can be configured between one mirror and one lens of the two for contrast enhancement. It can produce the photon combination with same of direction in this setup to enhance contrast.

An optical system includes a collimated light source, a beam splitter, two mirrors and two lenses, a focus lens, and a detector. An initial light beam is generated by the light source and then separated by the beam splitter into a first light beam and a second light beam. The two mirrors respectively direct the first and second light beams on a sample with symmetrical paths and the two lenses focus the first and second light beam on the sample respectively. The first and second light beams are reflected from the sample and along the counterpart paths to the beam splitter. An interfered light beam is then generated by combining the reflected first and second light beams, and focused by a focus lens on a detector. A Dove prism can be configured between one mirror and one lens of the two for contrast enhancement. It can produce the photon combination with same of direction in this setup to enhance contrast.

An interferometer having a fundamental beam generator, a first second harmonic generator, a waveplate, a second second harmonic generator, a harmonic separator, and a polarizing beam splitter, mounted uniaxially, (i.e., the components are aligned along one optical axis), wherein the interferometer is adapted to change a diameter of a beam to match a diameter of a sample, and to change the diameter of the beam back to its original diameter.

A system for passively monitoring a sample is disclosed. The system comprises an optical arrangement, a filtering unit and a detector unit. The optical arrangement is configured for collecting light arriving from a sample, directing the collected light to the filtering unit for filtering based on at least one of spatial and spectral composition and directing the collected light onto the detector unit. The optical arrangement and the detector unit are arranged to provide imaging of collected light from the sample on the detector unit with selected focusing/defocusing level to generate image data pieces comprising speckle patterns formed in the collected light.

An optical system includes a collimated light source, a beam splitter, two mirrors and two lenses, a focus lens, and a detector. An initial light beam is generated by the light source and then separated by the beam splitter into a first light beam and a second light beam. The two mirrors respectively direct the first and second light beams on a sample with symmetrical paths and the two lenses focus the first and second light beam on the sample respectively. The first and second light beams are reflected from the sample and along the counterpart paths to the beam splitter. An interfered light beam is then generated by combining the reflected first and second light beams, and focused by a focus lens on a detector. A Dove prism can be configured between one mirror and one lens of the two for contrast enhancement. It can produce the photon combination with same of direction in this setup to enhance contrast.

Systems and methods for improved interferometric imaging are presented. One embodiment is a partial field frequency-domain interferometric imaging system in which a light beam is scanned in two directions across a sample and the light scattered from the object is collected using a spatially resolved detector. The light beam could illuminate a spot, a line or a two-dimensional area on the sample. Additional embodiments with applicability to partial field as well as other types of interferometric systems are also presented.

Disclosed herein are self-mixing interferometry (SMI) sensors, such as may include vertical cavity surface emitting laser (VCSEL) diodes and resonance cavity photodetectors (RCPDs). Structures for the VCSEL diodes and RCPDs are disclosed. In some embodiments, a VCSEL diode and an RCPD are laterally adjacent and formed from a common set of semiconductor layers epitaxially formed on a common substrate. In some embodiments, a first and a second VCSEL diode are laterally adjacent and formed from a common set of semiconductor layers epitaxially formed on a common substrate, and an RCPD is formed on the second VCSEL diode. In some embodiments, a VCSEL diode may include two quantum well layers, with a tunnel junction layer between them. In some embodiments, an RCPD may be vertically integrated with a VCSEL diode.

A method is presented for determining a phase of an input beam (110, E.sub.in) without a reference ray. In the method, an input beam (110, E.sub.in) having a plurality of input rays is split into a main beam (112, E1) and a reference beam (114, E2) in such a way that each input ray is split into a main ray of the main beam (112, E1) and a comparative ray of the reference beam (114, E2). The main beam (112, E1) is propagated along a first interferometer arm, and the reference beam (114, E2) is propagated along the second interferometer arm. The propagated main beam (112, E1) and the propagated reference beam (114, E2) are superposed to form an interference beam having a plurality of interference rays. The propagation along the first and second interferometer arms is carried out such that at least one interference ray of the interference beam is a superposition of a main ray of the propagated main beam (112, E1) assigned to a first input ray of the input beam (110, E.sub.in), and of a comparative ray of the propagated reference beam (114, E2) assigned to a second input ray of the input beam (110, E.sub.in) different from the first input ray.

There are provided devices, systems and methods utilizing interferometric retro-reflection displacement/vibration meter. In particular, there are provided laser interferometer devices, systems and methods for measuring three-axis small angle displacements and vibrations of a body.