30results about How to "Reduce shot noise" patented technology

Apparatus, method, logic arrangement and storage medium are provided for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source can be split into N spectral bands. The N spectral bands can be individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band may be detected by a separate photo detector and amplified. For each spectral band, the signal can be band p3 filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is likely reduced by a factor equal to the number of spectral bands, while the signal amplitude can remain the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

Apparatus, method, logic arrangement and storage medium are provided for increasing the sensitivity in the detection of optical coherence tomography and low coherence interferometry (“LCI”) signals by detecting a parallel set of spectral bands, each band being a unique combination of optical frequencies. The LCI broad bandwidth source can be split into N spectral bands. The N spectral bands can be individually detected and processed to provide an increase in the signal-to-noise ratio by a factor of N. Each spectral band may be detected by a separate photo detector and amplified. For each spectral band, the signal can be band pass filtered around the signal band by analog electronics and digitized, or, alternatively, the signal may be digitized and band pass filtered in software. As a consequence, the shot noise contribution to the signal is likely reduced by a factor equal to the number of spectral bands, while the signal amplitude can remain the same. The reduction of the shot noise increases the dynamic range and sensitivity of the system.

An apparatus and method are provided. In particular, at least one first electro-magnetic radiation may be provided to a sample and at least one second electro-magnetic radiation can be provided to a non-reflective reference. A frequency of the first and / or second radiations varies over time. An interference is detected between at least one third radiation associated with the first radiation and at least one fourth radiation associated with the second radiation. Alternatively, the first electro-magnetic radiation and / or second electro-magnetic radiation have a spectrum which changes over time. The spectrum may contain multiple frequencies at a particular time. In addition, it is possible to detect the interference signal between the third radiation and the fourth radiation in a first polarization state. Further, it may be preferable to detect a further interference signal between the third and fourth radiations in a second polarization state which is different from the first polarization state. The first and / or second electro-magnetic radiations may have a spectrum whose mean frequency changes substantially continuously over time at a tuning speed that is greater than 100 Tera Hertz per millisecond.

An electron beam apparatus is provided for reliably measuring a potential contrast and the like at a high throughput in a simple structure. The electron beam apparatus for irradiating a sample, such as a wafer, formed with a pattern with an electron beam to evaluate the sample comprises an electron-optical column for accommodating an electron beam source, an objective lens, an E×B separator, and a secondary electron beam detector; a stage for holding the sample, and relatively moving the sample with respect to the electron-optical column; a working chamber for accommodating the stage and capable of controlling the interior thereof in a vacuum atmosphere; a loader for supplying a sample to the stage; a voltage applying mechanism for applying a voltage to the sample, and capable of applying at least two voltages to a lower electrode of the objective lens; and an alignment mechanism for measuring a direction in which dies are arranged on the sample. When the sample is evaluated, a direction in which the stage is moved is corrected to align with the direction in which the dies are arranged.

The invention discloses a rubidium atomic clock device based on differential light detection, which includes a rubidium spectrum lamp device and a photodetection signal generating device; the rubidium spectrum lamp device includes a rubidium spectrum light bulb, an oscillating coil and a radio frequency oscillation circuit board, and the two outputs of the rubidium spectrum light bulb are completely symmetrical Two groups of oscillating coils are symmetrically wound on the side wall of the rubidium spectrum bulb and electrically connected with the radio frequency oscillating circuit board; the light detection signal generating device includes a first light detection signal generating device and a second light detection signal generation device symmetrically arranged at both ends of the rubidium spectrum bulb The photodetection signal generation device, the first photodetection signal generation device and the second photodetection signal generation device are the same to lead out one photodetection signal respectively. The invention is beneficial to reduce optical noise and improve the short-term frequency stability index of the whole machine. The two-way optical signals pass through completely symmetrical optical components, and the background noise of the spectrum lamp and the shot noise in the detector are weakened by differential detection signals. ; It is beneficial to reduce the influence of temperature fluctuations and improve the long-term frequency stability index of the whole machine.

The invention provides a polarization error suppression device and method for a Y waveguide loop of an optical fiber current transformer, belonging to the technical field of optical fiber sensing. The Y waveguide loop is realized through the Y waveguide phase modulator and the polarization beam splitter. The two output pigtails of the Y waveguide phase modulator are respectively connected to the two input pigtails of the polarization beam splitter through melting point 1 and melting point 2, and are connected through melting point 1. The two pigtails and the two pigtails connected by the melting point 2 respectively constitute the two arms of the Y waveguide loop. The two arms of the Y waveguide loop are not equal in length, and the arm length difference is △L. The input pigtail of the Y waveguide phase modulator is connected with the circulator, and the output pigtail of the polarization beam splitter is connected with the polarization maintaining delay fiber ring. The invention can further reduce the optical path loss, reduce the shot noise of the detector, and improve the small current measurement accuracy of the transformer; by suppressing the polarization error of the Y waveguide loop, the stability of the small current measurement accuracy can be further improved.

A polarimeter based on coherent detection and a method for measuring the optical rotation of a polarized light beam by an optically active substance, while enabling the subtraction of background signals, are provided.