United Technologies Corporation

Demaria Electrooptics Systems, Inc.

Other

Frederick T Olender

William A Veronesi

Leon A Newman

Richard A Hart

Bernard A Woody

Eric R Mueller

Martin F Zabielski

Stephen K Phelps

The present invention is a photo-acoustic leak detection system that detects whether gas is leaking from a component. The system includes multiple beams wherein one beam is not absorbed by the gas and is used as a baseline measurement, while another beam absorbs the gas and emits an increased signal. Upon contact with the gas, an acoustic sensor senses the reaction or lack thereof between the gas and the beams, thereby allowing a signal processor to receive the respective alternating sensor signals after which the processor calculates the difference between the first and second signals to determine whether a leak exists. The photo-acoustic leak detection system also includes a beam combining means which forces the multiple beams to enter an acousto-optic cell at the same location. The acousto-optic cell, in turn, which is controlled by a signal controlling apparatus, sequentially and alternately diffracts the multiple beams at the same predetermined angle. Use of an acousto-optic cell removes the limitations inherent with mechanical parts, which, in turn, increases the sensitivity of the photo-acoustic leak detection system.

Photo-acoustic leak detection system

The present invention is a method and apparatus for sequentially and repetitively diffracting multiple beams at a common predetermined angle. A coincident beam source introduces a plurality of coincident beams into an acousto-optic cell at a common location and angle, wherein each beam has a different wavelength. A signal controlling apparatus sequentially and repetitively introduces a series of signals to the acousto-optic cell. Each signal has a frequency, which corresponds to one of the multiple beams such that when the acousto-optic cell receives the signal, the acousto-optic cell operates at such frequency and diffracts the corresponding beam at the predetermined angle.

Method and apparatus to diffract multiple beams

The present invention is a system for controlling the power level of a beam exiting an acousto-optic cell and/or a beam delivery device. A beam detector senses the power level of the beam and produces a power signal indicative thereof. An error detector compares the power signal to a predetermined power level. If the power signal and predetermined power level differ, the error amplifier emits a correction signal to a variable amplitude source, which adjusts the amplitude of the acoustic drive frequency such that the power level of the beam exiting the acousto-optic cell and/or the beam delivery device is substantially equal to the predetermined power level.

System to control the power of a beam

A photo-acoustic leak detection system for detecting a gas leaking from a component 30, includes at least two laser beams 24,26, incident on the component 30 and disposed so as to completely illuminate an inspection region 159 around at least a portion 28 of the component 30, each beam having a corresponding wavelength .lambda..sub.1 which is absorbed by the gas, the gas emitting an acoustic signal 36 when the gas absorbs light from at least one of the beams, an acoustic sensor 40, which receives the acoustic signals 36 and provides a sensor signal indicative thereof on a line 42 to a bandpass filter 44 and a synchronous detector 18 which provide a filtered signal indicative of the acoustic signal 36 on a line 50 to a signal processor 52. The processor 52 provides an output signal indicative of the leak in the component 30.

Photo-acoustic leak detector with multiple beams

A photo-acoustic leak detection system for detecting a gas leaking from a component includes a beam, having a wavelength, incident on the component and producing an acoustic signal. A second acoustic signal is also produced when an air source dilutes the gas leaking from the component. A signal processor receives sensor signals indicative of both acoustic signals and uses the second sensor signal as a non-leak baseline measurement and provides an output signal indicative of whether a leak exists.

Photo-acoustic leak detector with baseline measuring

A photo-acoustic leak detection system for detecting a gas leaking from a component (30), includes at least one laser beam (20), incident on the component (30) and having a wavelength which is absorbed by the gas, the gas emitting a photo-acoustic signal (36) when the gas absorbs light from the beam (20), the beam (20) being pulsed at a pulse frequency, the pulse frequency being related to a detection frequency of the photo-acoustic signal and being a frequency at which the magnitude of background acoustic noise at the detection frequency is at a predetermined low level, at least one acoustic sensor (40), which receives the photo-acoustic signal (36) and provides a sensor signal on the line (42) indicative thereof to a filter (44) and a synchronous detector (18), which provide a filtered signal on a line (50) to a signal processor (52). The processor (52) provides an output signal on a line (54) indicative of the leak in the component. Setting such pulse frequency to a low level acoustic noise frequency allows the signal-to-noise response to be greatly increased.

Photo-acoustic leak detector with improved signal-to-noise response

A light detection apparatus includes a light detector using a photoelectric converter such as a photodiode. The light detector has a selective viewport that limits the field of view observed by the photoelectric converter. The photoelectric converter generates a current signal based on the light received through the selective viewport. Using current-mode amplification, a current amplifier generates an amplified current signal based on the current signal received from the photoelectric converter. A switch coupled to receive the amplified current signal from the current amplifier, generates an output signal based on the amplified current signal. The switch can be implemented to generate the output signal with predetermined logic levels compatible with a desired logic family.

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Somers, CT, United States of America

Frederick T Olender