Signal beam

About: Signal beam is a research topic. Over the lifetime, 1881 publications have been published within this topic receiving 20717 citations.

Coherent imaging in turbid media

Abstract: A system for forming an image of an object in a turbid medium comprises a light source for producing a coherent light beam of a selected frequency that is divided by a beamsplitter into a reference beam directed along a first optical path and a signal beam directed along a second optical path where the object to be imaged is located. The signal beam impinges upon the object and reflects back toward the beamsplitter. The reference beam is modulated to shift its frequency. A mirror reflects the reference beam back toward the beamsplitter for combination with the signal beam to produce an output optical signal. A photodetector receives the output optical signal from the beamsplitter and produces an electrical signal having a frequency related to shifts in frequency between the reference beam and the signal beam and having an amplitude proportional to the image intensity. A heterodyne detector connected to the photodetector produces a beat signal when the first and second optical paths have matching lengths so that the location of the point on the object where the signal beam reflected can be determined. By scanning the signal beam across the object, the system determines locations of a number of points on the object sufficient to form its image.

Optical information recording and reproducing device, optical information recording and reproducing method, and reproducing device

Abstract: In recording and reproducing devices that use angular-multiplexing holography, accessing a recorded hologram of interest had taken time because after positioning at the vicinity of the hologram, it had been necessary to carry out fine adjustment of the position while checking the signal quality of the hologram. The optical information recording and reproducing device according to the present invention uses angular-multiplexing to record interference patterns formed from a signal beam and a reference beam onto an optical information recording medium as page data and reproduces information from the optical information recording medium, said optical information recording and reproducing unit being provided with: a light-source unit that outputs light; an optical splitting unit that splits the light into a reference beam and a signal beam; an angle controlling unit that controls the angle for the direction of angle multiplexing at which the reference beam enters the optical information recording medium; an optical detecting unit that detects a reproduced image that is reproduced by using the reference light; and a position control unit that controls the position relationship between the reference beam and the optical information recording medium. The device treats a set of page data as a book, and during recording, at least a portion of the page data in adjacent books is recorded while the entrance angle for the direction of angular-multiplexing for the reference light is shifted by means of the angle controlling unit. During reproduction, at least a portion of the light amount of a reproduced image is detected by using the optical detecting unit, and the position of the book is detected on the basis of information about the detected light amount.

Fringe scanning method

Abstract: PURPOSE:To perform uniform fringe scanning without disturbing a wave front over the entire range of beam, by performing fringe scanning while the phase scanning between reference beam and signal beam is changed by the voltage applied to a member having electrooptical effect. CONSTITUTION:When the voltage from an oscillator 15 is applied to the electrooptical crystal 18 provided on the common beam path 2 of reference beam and signal beam as crystal apply voltage 17 through an amplifier 16, the phase difference between the reference beam and the signal beam receives relative modulation in proportion to said voltage to perform fringe scanning. When the applied voltage data at this time is taken in a computer and the image processing of the interference fringe pattern subjected to modulation is performed, the interpolation between fringes can be performed and the profile of an object to be measured can be measured with measuring resolving power higher than lambda/4.

Four-wave-mixing interferometer.

Abstract: We have developed a new method of determining in time both the real and the imaginary parts of third-order nonlinear-optical coefficients. In this method the phase-conjugated four-wave-mixing signal beam interferes with one of the transmitted pump beams. By comparing the interference pattern with that of a known reference, we are able to determine the real and the imaginary parts of the third-order optical nonlinearity for an unknown sample. The real and the imaginary parts can also be separated when one incoming beam is delayed. We apply this method to a bis-thienyl polyene molecule containing five conjugate double bonds and find that the hyperpolarizability is γ1111 = (−2.5 − 0.17i) × 10−30 esu.

High efficiency coherent imager

Abstract: An extended field heterodyne detection apparatus comprises a local signal oscillator, a micro-lens array set in optical relation to the local signal oscillator to multiplex a beam from the local signal oscillator, a local oscillator injection lens in the optical path of the local oscillator and the micro-lens array, a semi-reflective beam splitter at the telecentric stop of the local oscillator injection lens to reflect the beam of the local oscillator in parallel to a signal beam passing through the semi-reflective beam splitter, an objective lens, with a stop, located at the semi-reflective beam splitter, and a focal plane array, situated to receive the source beam. The extended field heterodyne detection apparatus solves the problem of creating a local oscillator beam that is mode-matched for an incoming signal beam, for the eventual process of mixing both the signal beam and the local oscillator using a conventional, square-law detector.