Interferometric systems and methods for measuring rotational movement are described. In one implementation, an interferometer for measuring rotational movement includes a housing and a light source within the housing configured to project coherent light toward a non-coded surface of an object. The interferometer further includes at least one optical element configured to modify the projected coherent light in a manner accounting for a rotation of the object. The interferometer also includes at least one sensor within the housing including at least one light detector configured to detect reflections of the modified projected coherent light from the opposing non-coded surface as the object rotates relative to the housing. The interferometer further includes at least one processor configured to receive input from the at least one sensor and determine an amount of rotation of the object around the at least one rotational axis.

A laser interference device includes a measurement laser that outputs a laser beam, a beam splitter that divides the laser beam into a measurement laser beam and a frequency monitor laser beam, a reference laser that outputs a reference laser beam, a frequency detector that detects a beat frequency resulting from interference between the reference laser beam and the frequency monitor laser beam, a wavelength calculator that calculates a wavelength of the frequency monitor laser beam (a wavelength measurement value) on the basis of the beat frequency, a light detector that detects an interference light of the measurement light and the reference light of the measurement laser beam and outputs a light detection signal, and a displacement calculator that calculates a displacement of the measurement mirror by performing an arithmetic process based on the wavelength measurement value and the light detection signal.

Method and system for determining separation distance between an object and a processing or measuring tool involve generating a measurement beam of low coherence optical radiation, leading the measurement beam towards the object and the reflected measurement beam towards an optical interferometric sensor assembly in a first direction of incidence, generating a reference beam of low coherence optical radiation, and leading the reference beam towards the optical interferometric sensor assembly in a second direction of incidence, superimposing the measurement and reference beams on a common region of incidence, detecting position of a pattern of interference fringes between the measurement and reference beams on the region of incidence, and determining difference in optical length between a measurement optical path and a reference optical path on position of the pattern of interference fringes along an illumination axis, indicative of a difference between (a) current separation distance between the processing or measuring tool and the object and (b) predetermined nominal separation distance.

Channel separation in ophthalmologic systems is achieved by introducing a small angle between each beam incident on the scanner. The multiple channels are emitted from multiple emitters positioned such that their respective beams reach an X-Y scanner with small angular separations between the beams. This removes the need for dichroic components to combine the multiple channels into a single beam. This also allows the emitters to use the same wavelength if desired, such as in a combined SLO and OCT system in which it may be desirable to use the same light source in order to reduce the cost and complexity of the system.

Techniques for measuring optical aberrations of the eye are disclosed. An example method comprises positioning the eye in a measurement location adjacent to a measurement arm of an optical coherence tomography (OCT) interferometer apparatus, so that source light from the measurement arm passes into the anterior segment of the eye and detecting an interference pattern, the interference pattern resulting from a combination of light reflected from the eye and light reflected from a reference arm of the OCT interferometer apparatus. Based on the interference pattern, an optical delay between a reference surface in the anterior segment of the eye and a measured surface in the eye is calculated, the reference surface being the anterior surface of the cornea or the lens, wherein said calculating comprises measuring an optical phase shift between the reference surface and the measured surface, based on the detected interference pattern.

A heterodyne fiber interferometer displacement measuring system, including a laser light source assembly for simultaneously emitting measuring light and reference light; a first photoelectric detector, a first fiber coupler, a fiber ferrule, a plano-convex lens, a first polarizing beam splitting prism, and a first reflecting device which are sequentially provided on an optical path of the measuring light on the basis of first single mode fibers; and a second photoelectric detector, a second fiber coupler, a collimator, a second polarizing beam splitting prism, and a second reflecting device which are sequentially provided on an optical path of the reference light on the basis of second single mode fibers. An object to be measured is fixed on the first reflecting device, the reference light and the measuring light are processed to form measurement and reference signals, and displacement information of the object is determined according to the measurement reference signals.

An interferometric position sensor for sensing the position of an object is disclosed. The position sensor comprises a light source arranged to emit light, a beam splitter, and a detector array. The beam splitter is arranged to split the light between first and second optical paths, which are configured such that the split light is recombined so as to form an optical interference pattern dependent on the difference between the optical path lengths of the first and second optical paths. The detector array is arranged to measure the intensity of at least a part of the optical interference pattern. At least one of the first and second optical path lengths is arranged to be dependent on the position of the object, such that changes in the optical interference pattern can be related to changes in the position of the object.

An optical coherence tomography system for imaging a sample is configured so as to illuminate a region of interest of the sample with incident light from an optical source. The optical coherence tomography system is further configured so as to interfere, on an optical detector, reference light from the optical source with offset returning light emerging from the sample along an offset collection path which is spatially offset from the region of interest of the sample, thereby creating interference on the optical detector.

A system and a method for phase extraction of a multi-path interferometer, the method comprising generating a reference signal of a coherence length longer than an arm length difference of the multi-path interferometer; splitting the reference signal into a frequency shifted reference signal and an unshifted reference signal; recombining the frequency shifted reference signal and the unshifted reference signal into a polarization- and frequency-multiplexed reference signal, and feeding the polarization- and frequency-multiplexed reference signal to the multi-path interferometer; detecting frequency shifted and unshifted output signals of the multi-path interferometer; and determining the interferometer phase from the detected signal.

An OCT axial length measurement device is configured to measure an area of the retina within a range from about 0.05 mm to about 2.0 mm. The area can be measured with a scanned measurement beam or plurality of substantially fixed measurement beams. The OCT measurement device may comprise a plurality of reference optical path lengths, in which a first optical path length corresponds to a first position of a cornea, and a second optical path length corresponds to a second position of the retina, in which the axial length is determined based on a difference between the first position and the second position. An axial length map can be generated to determine alignment of the eye with the measurement device and improve accuracy and repeatability of the measurements. In some embodiments, the OCT measurement device comprises a swept source vertical cavity surface emitting laser (VCSEL).