A pixelated color mask is combined with a pixelated polarization mask in dynamic interferometry. The color mask includes a wavelength-selective bandpass filter placed in front of each camera pixel such that each set of contiguous four camera pixels is covered by two green bandpass filters, a red bandpass filter, and a blue bandpass filter. The pixelated phase mask is coupled to the color filters such that one polarization filter covers one set of color filters. At least three polarization filters are used to calculate phase. In addition, the color signals can be used, for example, to encode the motion of the interferometer, to provide very high speed autofocus or tip/tilt feedback, to create a color image of the object being measured, to automatically focus the system at different positions for different measurements conducted with different color sources, and to perform heterodyne interferometry with a single, vibration-immune measurement.

An interferometer system comprises a sample interferometer arm for guiding a first wave to a sample, and receiving a reflected wave from the sample and a phase amplifier for amplifying a phase shift of the reflected wave, to provide phase-shift-amplified intermediate wave. The interferometer system can also comprise an additional interferometer arm for guiding an additional wave to combine with the intermediate wave, to provide an output wave, and a detector for detecting the output wave.

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.

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.

The disclosure discloses a phase delay extraction and compensation method in a PGC phase demodulation technology. The sinusoidal phase modulation interference signal is converted into a digital interference signal by an analog-to-digital converter after amplification and filtering, and the digital interference signal is subjected to orthogonal downmixing of first-order, second-order, and fourth-order harmonics simultaneously to obtain three pairs of orthogonal harmonic amplitude signals. The three pairs of orthogonal harmonic amplitude signals are used to extract phase delay, and the result is used to calculate the corresponding phase delay correction coefficients, and the phase delay correction coefficient are multiplied by the corresponding absolute harmonic amplitude signal equal to the sum of the absolute value of the orthogonal harmonic amplitude signals to obtain a new harmonic amplitude signal that is not affected by the phase delay, then the phase to be measured is obtained through the arc tangent operation.

A laser interferometer includes alight 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.

An optical phase modulation amount measurement technology using sound without being affected by noise included in an average light intensity is provided. A sound measurement method includes an interference light generation step of obtaining first light including light subjected to light phase modulation by a sound measurement unit and second light including light subjected to light phase modulation by the sound measurement unit, which differs from the first light, from light emitted from a light source, a first light detection step of obtaining a first electrical signal from the first light, a second light detection step of obtaining a second electrical signal from the second light, and a differential signal generation step of obtaining a differential signal that is a difference between the first electrical signal and the second electrical signal, wherein a phase of the light subjected to light phase modulation included in the first light and a phase of the light subjected to the light phase modulation included in the second light are in an inverted relationship, and an optical phase modulation amount φ.sub.s by sound is measured as a current Δi of the differential signal expressed by an equation Δi=βI.sub.A cos (φ.sub.s+φ.sub.0) (where β is a predetermined constant, I.sub.A is an amplitude of an interference fringe, and φ.sub.0 is an optical phase modulation amount by an element other than sound).

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.

Systems, methods, and media for multiple beam optical coherence tomography are provided which, in some embodiments, include: a light source; a splitter that outputs a fraction of light to various waveguides; optical components that receive light from the waveguides and direct the light as beams that simultaneously impinge a sample at different lateral positions, and collect backscattered light from the lateral positons; another splitter that outputs a fraction of light to waveguides of a reference arm as reference light samples; a mixer that receives the backscattered light samples and the reference light samples, and combines each backscattered sample with a corresponding reference sample such that the mixer outputs fringes; and a detector that receives the fringes, and outputs OCT signals, each indicative of a structure of the sample at a respective lateral position.

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.