195 results about "Stokes parameters" patented technology

An apparatus and method to determine the surface orientation of objects in a field of view is provided by utilizing an array of polarizers and a means for microscanning an image of the objects over the polarizer array. In the preferred embodiment, a sequence of three image frames is captured using a focal plane array of photodetectors. Between frames the image is displaced by a distance equal to a polarizer array element. By combining the signals recorded in the three image frames, the intensity, percent of linear polarization, and angle of the polarization plane can be determined for radiation from each point on the object. The intensity can be used to determine the temperature at a corresponding point on the object. The percent of linear polarization and angle of the polarization plane can be used to determine the surface orientation at a corresponding point on the object. Surface orientation data from different points on the object can be combined to determine the object's shape and pose. Images of the Stokes parameters can be captured and viewed at video frequency. In an alternative embodiment, multi-spectral images can be captured for objects with point source resolution. Potential applications are in robotic vision, machine vision, computer vision, remote sensing, and infrared missile seekers. Other applications are detection and recognition of objects, automatic object recognition, and surveillance. This method of sensing is potentially useful in autonomous navigation and obstacle avoidance systems in automobiles and automated manufacturing and quality control systems.

A polarization camera includes a microlement polarizer that is situated in proximity to a focal plane array. The microlement polarizer is selectively scanned with respect to an optical image direct to the focal plane array, and an image processor stores a set of images associated with the scanning. Based on the stored images, a polarization image can be produced and displayed. A periodic microelement polarizer modulates the individual images of the set, and these images can be processed by filtering in the spatial frequency domain to isolate contributions associated with one or a combination of Stokes parameters. After filtering, Stokes parameter based images can be obtained by demodulating and inverse Fourier transforming the filtered frequency domain data.

A telecommunications optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. This can be used in a non-locating system where the detection end is opposite the transmit end or in a locating system which uses Fresnel reflections and Rayleigh backscattering to the transmit end to detect and then locate the motion. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a polarization detection system which includes an optical splitter which is manufactured in simplified form for economic construction. This uses a non-calibrated splitter and less than all four of the Stokes parameters. It can use a polarimeter type function limited to linear and circular polarization or two linear polarizers at 90 degrees.

A telecommunications optical fiber is secured against intrusion by detecting manipulation of the optical fiber prior to an intrusion event. This can be used in a non-locating system where the detection end is opposite the transmit end or in a locating system which uses Fresnel reflections and Rayleigh backscattering to the transmit end to detect and then locate the motion. The Rayleigh backscattering time sliced data can be stored in a register until an intrusion event is detected. The detection is carried out by a polarization detection system which includes an optical splitter which is manufactured in simplified form for economic construction. This uses a non-calibrated splitter and less than all four of the Stokes parameters. It can use a polarimeter type function limited to linear and circular polarization or two linear polarizers at 90 degrees.

An apparatus (200) for determining fiber orientation parameters of a sheet of material during a production process includes a polarized radiation generating system (201, 202) operable for providing polarized radiation having a frequency of at least 1×108 Hz. The radiation is aligned to be incident on a sheet of material to be characterized (203). A polarimeter (204, 205) is aligned to receive the radiation transmitted by the sheet of material (203). A photodetector (206) is provided for measuring radiation received after polarization processing by the polarimeter. A processor (207) is coupled to the photodetector (206) for calculating Stokes parameters of the moving sheet (203) based upon intensities of the radiation received and determines at least one parameter relating to fiber orientation of the moving sheet based upon the Stokes parameters.

A polarimetric imaging system employs a pixel pitch matched filter for use within, for example, a 2 by 2 pixel neighborhood, in which one pixel samples the scene via a 0 degree polarization filter and a second pixel samples the scene via a 45 degree polarization filter. The remaining two pixels record the intensity of the light within the 2 by 2 neighborhoods. The polarization filters employ organic materials such as polymers or metallic materials that are patterned and etched using reactive ion etching (RIE) or other appropriate etching technique in order to create 14 micron or smaller circular (or square) periodic structures that are patterned into polarization thin films that are deposited on an imaging sensor that includes a processor that computes from the polarization-filtered inputs the first three Stokes parameters in real-time.

A system for determining a new orientation and / or position of an object comprises a sky polarimeter configured to record image data of the sky, a signal processing unit, and logic configured to receive and store in memory the image data received from the sky polarimeter. The logic calculates the Stokes parameters (S0, S1, S2,), DoLP, and AoP from the image data, detects obscurants and filters the obscurants (such as clouds and trees) from the image data to produce a filtered image. The logic is further configured to find the Sun and zenith in the filtered image, and to determine the roll, pitch, yaw, latitude and longitude of the object using the filtered image. A method for determining a new position / orientation of an object comprises recording raw image data using a sky polarimeter, calculating S0, S1, S2, DoLP, and AoP from the image data, detecting obscurants and filtering the obscurants from the image data to produce a filtered image, obtaining last known position / orientation data of the object, finding the Sun and zenith in the filtered image, and determining the roll, pitch, yaw, latitude and longitude of the object using the filtered image.

The invention relates to a testing device for realizing Mueller matrix of an optical device based on a rotatable wave plate and a method. A testing system consists of a laser device, a polarization generator, a tested device, a polarization analyzer, a voltage controller and a computer. Light generated by the laser device enters the polarization generator, the polarization generator consists of a polarizer and the rotatable wave plate, the rotation angle of the wave plate is larger than 180 degrees, rotation of the wave plate is controlled by voltage, and the polarization generator generates different polarization state outputs under different control voltages. Light outputted by the polarization generator enters the tested device, light outputted by the tested device directly enters the polarization analyzer, and the polarization analyzer detects corresponding output polarization states of the polarization generator and corresponding Stokes parameters of output polarization states of the tested device when in different control voltages. Afterwards, a linear system equation among detected input and output polarization state parameters and Mueller matrix parameters of the tested device is built, the computer solves the system equation, and then 16 parameters of the Mueller matrix can be solved.

A synthetic aperture radar hybrid-polarity method and architecture comprising transmitting circular polarization (by driving the orthogonal linear feeds simultaneously by two identical waveforms, 90° out of phase), and receiving horizontal (H) and vertical (V) linear polarizations, coherently. Once calibrated, the H and V single-look complex amplitude data are sufficient to form all four Stokes parameters, which fully characterize the observed backscattered field.

The invention provides a Stokes polarization meter error calibration and compensation method based on a wave plate rotating method. The Stokes polarization meter error calibration and compensation method includes the specific steps that horizontal line polarization light generated by a PSG is used as standard reference light; the standard reference light is measured through a to-be-calibrated Stokes polarization meter N times to obtain N light intensity values; Fourier analysis is carried out on the obtained N light intensity values to obtain corresponding Fourier coefficients; the fast axis azimuth angle error and the phase delay amount error of a quarter-wave plate are calculated through the relation between device parameter errors and the Fourier coefficients according to the Fourier coefficients; error compensation is carried out on the Stokes polarization meter through the relation between Stokes parameters and the parameter errors according to the two parameter errors of the quarter-wave plate. The Stokes polarization meter error calibration and compensation method is easy to operate, high in feasibility and high in calibration accuracy.

To effectively reduce a measurement error in a parameter indicating two-dimensional spatial distribution of a state of polarization generated by variations in retardation of a birefringent prism pair due to a temperature change or other factors, while holding a variety of properties of an imaging polarimetry using the birefringent prism pair. By noting that reference phase functions φ1(x, y) and φ2(x, y) are obtained by solving an equation from each vibration component contained in an intensity distribution I(x, y), the reference phase functions φ1(x, y) and φ2(x, y) are calibrated concurrently with measurement of two-dimensional spatial distribution S0(x, y), S1(x, y), S2(x, y), and S3(x, y) of Stokes parameters.

Systems and methods for measuring the state of polarization (SOP) for each wavelength channel in a multi-wavelength-channel light beam are disclosed. The system includes a set of two or more rapidly switchable waveplates switched to form a sequence of secondary light beams having different polarizations. A polarizer filters the set of secondary light beams, and a spectral dispersing element spatially divides the secondary light beams into their respective wavelength components. A detector array measures in parallel the intensity of the different wavelength components for each of the polarization-filtered light beams. A controller stores the intensity measurements and calculates the Stokes parameters for each wavelength component, thereby characterizing the SOP for all the wavelength channels of the multi-wavelength light beam.

The present invention relates to a Mueller matrix self calibration measurement method, the biggest characteristic of a Mueller matrix measurement method in the prior art is the need of precision calibration of an optical system of a measuring device, and the difficulty of precision measurement of a Mueller matrix is increased. According to the Mueller matrix self calibration measurement method, Stokes parameters of output polarization states before and after a to-be-test sample is put in are measured, a formula of the functional relationship between measured output light intensity and unknown parameters of a system and a Mueller matrix of a measured sample is established, and the Mueller matrix of the to-be-test sample is obtained by solution with a multiple-parameter nonlinear fitting method. The Mueller matrix self calibration measurement method needs no precision calibration of the measurement system, and realizes the self calibration measurement of the Mueller matrix, and the measurement method is simple and easy to operate, and can be widely used in Mueller matrix measurement of various polarization components and optical systems.

A method to monitor the state of polarization incident on the photomask in projection printing is presented. The method includes a series of phase-shifting mask patterns that take advantage of high NA effects to create a signal dependent on only one incident polarization component. The patterns exist in two embodiments: a Radial Phase Grating (RPG) and Proximity Effect Polarization Analyzers (PEPA). The PEPAs are derived from basic principles and are theoretically the most sensitive patterns to polarization. A polarimeter is then constructed of six patterns of either embodiment that, when properly calibrated, is sufficient to measure the Stokes parameters of the incident illumination. A test reticle design is proposed, consisting of multiple polarimeters with an array of pinholes on the backside of the photomask. This technique is able to monitor any arbitrary illumination scheme for a particular tool. Calibration of the test mask is required. However, proper calibration is likely to enable accurate full pupil polarization characterization, even when severe mask topography effects and reasonable maskmaking limitations are considered.

The invention discloses a real-time polarization state and real-time phase measurement method based on a pixel polarizing film array. According to the method, the polarizing film array is integrated with a photosensitive element array, each polarizing film unit of the polarizing film array aligns to each photosensitive unit of the photosensitive element array one by one, the polarizing film array is composed of a plurality of equal-sized subarraies, each subarray comprises a plurality of polarizing film units, and transmission polarization directions of different polarizing film units in the same subarray are different. When polarization states are measured, after first three corresponding stokes parameters of light are obtained according to light intensity value which each pixel corresponds to, the linear polarization degree and the linear polarization angle of each pixel of images are calculated, and when phase positions are measured, laser is divided into object light wave and reference light and then modulated to levogyration circularly polarized light and dextrorotation circularly polarized light which penetrate the polarizing film array to be incident to the photosensitive element array. By means of the real-time polarization state and phase measurement method based on the pixel polarizing film array, light intensity, polarization state information and phase information of a dynamic object can be real-timely measured.

An apparatus and method for measuring optical signal-to-noise ratio in optical communications includes (1) a variable optical band-pass filter (VOBPF) that passes the amplified output beam when the beam wavelength is the same as the passing wavelength of the VOBPF; (2) a 1x4 beam distributor for distributing the passing beam of the VOBPF into four streams; (3) a measuring device for measuring Stokes parameters S0, S1, S2, S3 from the four distributed beams; (4) a calculating device for calculating the optical signal power by finding the power of the polarized component of the amplified output beam from the Stokes parameters S1, S2, and S3; (5) a calculating device for calculating the noise power by finding the power of the noise included in the amplified output beam from Stokes parameter S0 and the optical signal power; and (6) a dividing device for calculating the ratioat the passing wavelength.

The invention discloses a ground feature classifying method based on simplified polarization synthetic aperture radar data, which relates to the synthetic aperture radar remote sensing information processing technology. The ground feature classifying method includes steps: a) obtaining Stokes parameters after filtering; b) extracting characteristic parameters including polarizability m, relative phase difference delta among orthogonal channels and total polarization power span for showing scattering mechanisms; c) calculating power ingredients corresponding to the basic scattering mechanisms, and determining main scattering mechanisms of pixels and dividing data into three types of pixels with identical scattering characteristics; d) further dividing each type of pixels with identical scattering characteristics into a plurality of types of pixels with equal sample numbers by the aid of the span; and e) realizing iterative Wishart classification. The ground feature classifying method is simple in principle and convenient in calculation, and can be used for analyzing and classifying ground feature scattering characteristics.

The invention relates to a method for improving measurement precision of a beam polarization degree. A utilized polarization detection device comprises a phase delay device, an analyzer and a photo detector which are sequentially arranged along an optical axis of a system of the device, wherein the output of the photo detector is connected with a signal processing system, a beam to be measured which is parallel to the optical axis of the system is emitted to the phase delay device and the analyzer and detected by the photo detector, and the electric signal output by the photo detector is sent to the signal processing system for data processing. The method is characterized in that the transmission axis direction of the analyzer and the polarization direction of the beam to be measured are adjusted to be parallel or vertical according to the polarization direction of the beam to be measured, and then the measurement of the polarization degree of the beam to be measured is carried out. A stokes parameter and the polarization degree of the beam to be measured are obtained according to the light intensity detected by the photo detector. The invention can improve the measurement precision of the polarization degree.

A system for determining polarization profiles of points in a scene from video frames using Stokes parameters includes a scene having a region that emits scene light rays that correspond to the points in the scene, an optical chopper controller, a rotating Stokes filter wheel that includes five trigger holes, three rotating linear polarizers, a circular polarizer, and a reference screen, a color filter, a video camera having a video frame, and a computer system having a frame grabber apparatus. The scene light rays are transmitted through the Stokes filter and the color filter to the video camera. Images corresponding to the scene light rays are projected onto respective pixels in the video frame and recorded as two-dimensional (2-D) arrays, and the images corresponding to the scene light rays from four unique images, obtained from light transmitted consecutively through three linear polarizers and a circular polarizer of the rotating Stokes filter wheel, are used by programming in the computer system to calculate respective Stokes parameters of the points in the scene.

A method is provided for measuring Mueller Matrix of an optical system of an exposure apparatus. Light flux from a light source is serially converted into any of a plurality of polarized light beams perpendicular to each other on Poincare sphere and is output. This polarized light beam is injected into a projection optical system or the like to be converted into a converted polarized light beam based on Mueller matrix of each optical system. With a linear polarizer or a linear phase retarder being properly inserted into an optical path of the converted polarized light beam, a light intensity is measured. Stokes parameters of the converted polarized light beam are calculated based on the measured light intensity.

An imaging polarimeter and a method of utilizing the imaging polarimeter are provided. The method includes receiving a first light ray at a beam splitter and splitting the first light ray into second, third, fourth, and fifth light rays such that the second, third, fourth, and fifth light rays are simultaneously received on a flat focal plane. The method further includes outputting first, second, third, and fourth signals indicative of first, second, third, and fourth intensities, respectively, of the second, third, fourth, and fifth light rays, respectively, utilizing a sensor array disposed on the focal plane. The method further includes determining first, second, third, and fourth Stokes parameters for a pixel of the sensor array based on the first, second, third, and fourth signals, respectively, utilizing a computer.

The invention relates to a method for simulating an underwater polarization field of wave water surface transmitted light. The method comprises the following steps: firstly, building a polarization model based on Rayleigh scattering sky light, and calculating the polarization of incident sky light; according to different refraction coefficients corresponding to a parallel component and a vertical component of an incident light E vector, obtaining a Mueller matrix of a refraction process of a calm water surface; secondly, building a probability distribution model of a wave water surface element gradient, unifying the reference coordinate systems of the incident light and transmitted light, considering the shield effect among wind waves, and obtaining a Mueller matrix of a refraction process of a wave water surface; and finally, combining the Stokes parameter representation method to obtain a polarization field distribution mode of underwater transmitted light. The method can successfully simulate polarization characteristic distribution of underwater transmitted light of different sun positions and takes the influence of wind speed and wind direction on underwater light field polarization characteristic distribution into consideration. Meanwhile, the method can reveal polarization distribution rules of underwater transmitted light in a Snell window.

The present invention relates to an embedded polarization state measuring apparatus, which is composed of a detection unit (1), liquid crystal type adjustable-phase delayer(s) (3, 4), a polarization beam-splitting prism (5), a collective lens (6), a photo detector (7) arranging in a shaft of a first part of the detection unit (1); a collective lens (8) and a photo detector (9) arranging in a shaft of a second part being orthogonal with the first part; a control unit (2) containing a signal-collection and liquid crystal control module (10), a data treatment module (11), a display module (12) and a RS232 serial port (13). By means of replacing rotational wave sheet by the liquid crystal type adjustable-phase delayer, It is able to control polarization state of incident light and measure Stokes parameter for real time quantity of polarization state accurately, and to overcome mechanical vibration problem; it is used for collimation of optical element(s), measurement of optical phase delay, material representation, medicament development, communication equipment, ellipse polarization instrument and spectrum application as well as space optical communication.

The invention discloses a real-time pressure sensing method based on a fiber bragg grating reflected light polarization parameter. Laser transmitted by a tunable laser (1) sequentially passes through an isolator (2), an online polarizer (3), rotational optical fiber connection ports (A and B) and a polarization controller a (4) and then enters a first port (1) and a second port (2) of a circulator (5) and is connected with a sensing fiber bragg grating (6); light reflected by the sensing fiber bragg grating (6) is output from a third port (3) and enters an online polarization detection module (8) through a polarization controller b (7) to output four paths of simulation voltage signals V1, V2, V3 and V4 containing polarization information; four paths of simulation voltage signals are converted into digital signals through an analogue / digital conversion module (9); the digital signals enter a signal processing and displaying module (10) to obtain four stokes parameters S0, S1, S2 and S3 as well as other relevant polarization parameters of reflected light in a polarization state; and the pressure borne by the sensing fiber bragg grating is sensed by monitoring and normalizing a first stokes parameter s1 being equal to S1 / S0 value in real time.

The invention discloses a light beam stokes parameter measuring device and a measuring method thereof. The polarization measuring device is composed of a beam splitter prism group, a phase retarder array, a polarization analyzer, a photoelectric detector array and a signal processing system, wherein all units of the photoelectric detector array correspond to all units of the phase retarder array one by one. The measuring method is realized through the following steps: adopting the phase retarder array to replace the rotational phase retarder; according to the polarization direction of a to-be-measured light beam, adjusting the direction of a light-transmitting shaft of the polarization analyzer to be parallel to or vertical to the polarization direction of the to-be-measured light; measuring the polarization parameters of the to-be-measured light beam; processing data as per light intensity signals detected by the photoelectric detector array so as to realize the real-time high accuracy measurement of the light beam stokes parameters. Though adopting the method, the stokes parameters of the light beam can be measured in real time, and furthermore, the influences on the measurement accuracy of the light beam polarization state caused by the phase delay error of phase delaying devices, the fast-shaft direction error, the direction error of the light-transmitting shaft of the polarization analyzer and the extinction ratio error are reduced.