The present invention relates to an apparatus and a method for measuring a thickness and a refractive index of a multilayer thin film using an angle-resolved spectral interference image according to polarization. More specifically, the present invention relates to an apparatus for measuring a thickness and a refractive index of a multilayer thin film using an angle-resolved spectral interference image according to polarization in an apparatus for measuring a thickness and a refractive index of a measurement object coated with the multilayer thin film, the apparatus including: an illumination optical module having a light source emitting light; a first beam splitter configured to reflect some of the light emitted from the illumination optical module; an objective lens configured to input some of the light reflected from the first beam splitter to the measurement object constituted by the multilayer thin film and reflect the remaining light to a reference plane to form interference light on a back focal plane; a second beam splitter in which interference light where the reflected light incident and reflected to the measurement object interferes with the reflected light reflected from the reference plane is incident, wherein some of the interference light is reflected and the remaining interference light is transmitted; a first angle-resolved spectral image acquiring unit configured to receive interference light reflected from the second beam splitter and first-polarize the interference light located in the back focal plane of the objective lens to acquire a first polarized interference image; and a second angle-resolved spectral image acquiring unit configured to receive interference light transmitted from the second beam splitter and second-polarize the interference light located in the back focal plane of the objective lens to acquire a second polarized interference image.

Systems, methods and apparatuses are used for monitoring material processing using imaging signal density calculated for an imaging beam directed to a workpiece or processing region, for example, during inline coherent imaging (ICI). The imaging signal density may be used, for example, to monitor laser and e-beam welding processes such as full or partial penetration welding. In some examples, the imaging signal density is indicative of weld penetration as a result of reflections from a keyhole floor and/or from a subsurface structure beneath the keyhole. The monitoring may include, for example, automated pass/fail or quality assessment of the welding or material processing or parts produced thereby. The imaging signal density may also be used to control the welding or material processing, for example, using imaging signal density data as feedback. The imaging signal density may be used alone or together with other measurements or metrics, such as distance or depth measurements.

OCT measuring device in the present exemplary embodiment includes: wavelength sweep light source that emits light of which a wavelength is swept; optical interferometer that divides the light into measurement light and reference light, emits measurement light toward measurement surface of measuring target object, and generates an optical interference intensity signal indicating an intensity of interference between measurement light reflected from measurement surface and reference light; electro-optic element which is a phase modulator arranged in a light path of optical interferometer; measurement processor which is a signal generator that derives a position of measurement surface and generates a phase amount indicator signal that indicates a phase amount of phase modulator based on the optical interference intensity signal; and electro-optic element controller which is a phase amount controller that controls the phase amount given to the light that is transmitted through phase modulator.

An interferometric overlay tool may include an interferometer and a controller. The interferometer may include one or more beamsplitters to split illumination including one or more wavelengths into a probe beam along a probe path and a reference beam along a reference path, one or more illumination optics to illuminate a grating-over-grating structure with the probe beam, one or more collection optics to collect a measurement beam from the grating-over-grating structure, one or more beam combiners to combine the measurement beam and the reference beam as an interference beam, and a variable phase delay configured to vary an optical path difference (OPD) in the interferometer. The controller may receive one or more interference signals representative of interferometric phase data associated with a plurality of OPD values and the one or more wavelengths from a detector and determine an overlay error of the grating-over-grating structure based on the interferometric phase data.

An interferometric distance-measurement device includes a multi-wavelength light source which provides a beam having at least three different wavelengths. An interferometer unit splits the beam into measuring and reference beams. The measuring beam propagates in the direction of a measuring reflector movable along a measuring axis and undergoes a back-reflection, and the reference beam propagates in the direction of a stationary reference reflector and undergoes a back-reflection. The back-reflected measuring and reference beams interfere with each other in an interference beam. A detection unit splits the interference beam such that several phase-shifted partial interference signals result for each wavelength. A signal processing unit determines absolute position information regarding the measuring reflector from the partial interference signals of different wavelengths and an additional coarse position signal.

A laser interferometer includes a light source that emits first laser light, an optical modulator that includes a vibrator and modulates the first laser light by using the vibrator to generate second laser light including a modulated signal, a photodetector that receives interference light between third laser light including a sample signal generated by reflecting the first laser light on an object and the second laser light to output a light reception signal, a demodulation circuit that demodulates the sample signal from the light reception signal based on a reference signal, and a signal generator that outputs the reference signal input to the demodulation circuit and outputs a drive signal input to the optical modulator, in which Vd/Vr<10, where Vr is a voltage of the reference signal and Vd is a voltage of the drive signal.

A laser interferometer includes a light source that emits first laser light, an optical modulator that includes a vibrator and modulates the first laser light by using the vibrator to generate second laser light including a modulated signal, a photodetector that receives interference light between third laser light including a sample signal generated by reflecting the first laser light on an object and the second laser light to output a light reception signal, and an optical path length variable section that changes an optical path length of an optical path through which the third laser light propagates.

A laser interferometer includes a light source that emits first laser light, an optical modulator that includes a vibrator and modulates the first laser light by using the vibrator to generate second laser light including a modulated signal, a photodetector that receives interference light between third laser light including a sample signal generated by reflecting the first laser light on an object and the second laser light to output a light reception signal, a demodulation circuit that demodulates the sample signal from the light reception signal based on a reference signal, and an oscillation circuit that outputs the reference signal to the demodulation circuit, and the vibrator is a signal source of the oscillation circuit.

A laser interferometer includes a light source that emits first laser light, an optical modulator that includes a vibrator and modulates the first laser light by using the vibrator to generate second laser light including a modulated signal, a photodetector that receives interference light between third laser light including a sample signal generated by reflecting the first laser light on an object and the second laser light to output a light reception signal, and a demodulation circuit that performs a demodulation process for demodulating the sample signal from the light reception signal, and the demodulation circuit intermittently performs the demodulation process.

A method including: scanning a sample over a period of time using an electro-magnetic radiation source, the period of time including a first time period and a second time period, a sample portion of the electro-magnetic radiation source being directed to the sample in a sample arm of an optical interferometric system, and a reference portion of the electro-magnetic radiation source being directed to a reference arm of the optical interferometric system; applying, using a phase modulator, a phase shift comprising a first phase shift and a second phase shift to at least one of the reference portion or the sample portion of the electro-magnetic radiation source, the first phase shift being applied during the first time period and the second phase shift being applied during the second time period, the second phase shift having a difference of 90 degrees from the first phase shift; acquiring in-phase data based on a first interference between first backscattered electro-magnetic radiation during the first time period and the at least one of the reference portion or the sample portion subjected to the first phase shift; acquiring quadrature data based on a second interference between second backscattered electro-magnetic radiation during the second time period and the at least one of the reference portion or the sample portion subjected to the second phase shift; and determining a complex interference signal based on the in-phase data and the quadrature data.