Abstract:
The present invention is directed at a coherence test reticle or lithographic plate, and a method for testing the coherence of a laser beam using the test reticle. The quality or coherence of the laser beam is measured by illuminating the test reticle and recording and/or analyzing the optical patterns generated by the illumination. The technique was designed for the characterization of laser-based systems via the detection of optical radiation modulated by transmissive, reflective and diffractive patterns printed on a reticle or lithographic plate designed specifically for this purpose. The novelty and advantages over the prior art are insensitivity to vibration, alignment, and multi-path differences associated with classical interferometric coherence measurement techniques. The technique is focus error insensitive. The robustness and convenience of the technique is driven by the use of a single plate with no optical alignment, making the technique easily implemented in the field.
Abstract:
The present invention is directed at a coherence test reticle or lithographic plate, and a method for testing the coherence of a laser beam using the test reticle. The quality or coherence of the laser beam is measured by illuminating the test reticle and the recording and/or analyzing the optical patterns generated by the illumination. The technique was designed for, but not limited to, the characterization of laser-based systems via the detection of optical radiation modulated by transmissive, reflective and diffractive patterns printed on a reticle or lithographic plate designed specifically for this purpose. The novelty and advantages over the prior art are insensitivity to vibration, alignment, and multi-path differences of classical interferometric coherence measurement techniques. Spatial coherence and longitudinal or temporal coherence may be measured independently. Vertical and horizontal coherence may be measured independently. The technique is focus error insensitive. That is to say, that focus errors will be recorded by the technique in a deterministic fashion and can be removed from the data. The robustness and convenience of the technique is driven by the single plate with no optical alignment, making the technique easily implemented in the field. The multiplexing of the feature orientations, sizes and line types and feature locations allows for the determination of coherence parameters as a function of position in the beam.
Abstract:
An incident light field is applied to the two separate front fiber faces of a pair of identical optical fibers which are initially held in a common plane. One fiber face is always kept stationary. The other fiber face may be moved either laterally in a plane common to the stationary face, or longitudinally into and out of the common plane. The output end of the device comprises two separate rear fiber faces that are held in a common plane. These faces are stationary. There is no lateral or longitudinal motion of one relative to the other. The light emerging from these two faces interferes in the far field. Straight line interference fringes whose spacing depends upon the lateral separation of the rear fiber faces are formed. The fringe modulation, however, depends upon the relative position of the front fiber faces. This modulation changes as one front face is scanned either laterally or longitudinally. The modulation changes with such motion is related to the degree of spatial or temporal coherence of the incident light field.
Abstract:
An interference device for discriminating between radiation sources of differing coherence length comprises means to divide received radiation from a source into two components. A path difference, defining a coherence length cut-off, is introduced into the path of one component and the components are brought together for interference. The recombined light passes through a reticle with alternate opaque and tranparent bars and an optical band-pass filter to a detector. Interference fringes present in the plane of the reticle are swept across the reticle by the action of the collection optical system of the device which includes a scanning rotating mirror. Two similar devices can be arranged for band-pass coherence length filtering and when used in conjunction with a light soruce whose coherence is modulated the device can be used for signalling.
Abstract:
A self-tuning optical notch filter is employed to separate coherent from noncoherent radiation in an overall beam. The presence of coherent radiation is detected, preferably with an interferometer, and the frequency of the detected coherent radiation is determined. An electrical control signal is generated with a frequency corresponding to that of the coherent radiation, and causes an optical filter to filter out the coherent radiation from the beam. In the preferred embodiment the optical filter is a Bragg cell, and the electrical control signal is applied to an electro-acoustic transducer which furnishes an acoustic control signal to the Bragg cell.
Abstract:
An imaging coherent radiometer for detecting and determining the location and wavelength of coherent radiation or coherent lack of radiation in the presence of non-coherent ambient radiation. The apparatus includes an unequal path interferometer which divides incoming radiation containing coherent and non-coherent radiation into a first beam path and a second beam path through which a first beam and a second beam, respectively, travel. The optical path length difference between the first beam path and the second beam path are greater than the coherence length of the non-coherent radiation, but substantially less than the coherence length of the coherent radiation or coherent lack of radiation. Modulation means are provided to cause a predetermined difference in the optical frequencies between the first beam and the second beam proportional to a modulation signal. The first and second beams are then recombined into a recombined beam. Detecting means are provided to detect the interference of the first and second beams across the entire wavefront of the recombined beam, and over the entire image of the scene being viewed. Processing means detect and determine the location and wavelength of coherent radiation or coherent lack of radiation in the scene being viewed by the apparatus. This information can then be visually displayed. Additional processing means to respond to specific coherent wavelengths or wavelength sets.
Abstract:
The invention relates to a device (1) for detecting laser radiation (45), comprising at least one light inlet (51) and at least one photoelectric transducer (5), which is designed to convert electromagnetic radiation (46) entering through the light inlet (51) into an electrical signal, wherein a modulator (4) is arranged in the beam path between the light inlet (51) and the photoelectric transducer (5), which modulator is designed to modulate laser radiation at a specifiable modulation frequency. The invention further relates to a corresponding method.
Abstract:
A quantitative phase image generating method for a microscope, includes: irradiating an object with illumination light; disposing a focal point of an objective lens at each of a plurality of positions that are mutually separated by gaps Δz along an optical axis of the objective lens, and detecting light from the object; generating sets of light intensity distribution data corresponding to each of the plurality of positions based upon the detected light; and generating a quantitative phase image based upon the light intensity distribution data; wherein the gap Δz is set based upon setting information of the microscope.
Abstract:
Systems and methods for forming a coherent optical phased array laser source from a spatially combined array of output beams is accomplished without any external measurement devices or wavefront sensors. A master oscillator laser is split into a plurality of optical beam transport and amplifier channels to produce a plurality of optical output beams that are spatially combined in an array format. The spatial phase state of the plurality of output beams is measured at the output of a spatial combiner without use of an external measurement device or sensor. The phase of the plurality of optical output beams is controlled to compensate both for aberrations induced by the optical beam transport and amplifier paths to produce a coherent and spatially phased laser beam at the output of the laser source or to produce a phased laser beam with prescribed phase state on each output beam.