A twin-etalon scanning spectrometer is disclosed that provides high luminosity and high resolution. The etalons are positioned in spaced relationship with respect to one another in series in the path of an emission light source. With identical etalons so positioned, a line emission transmitted by the rearwardly positioned etalon is at the same angles as that of the forwardly positioned etalon and the light transmission through the etalons is therefore at a maximum. When the relative spacing of the light transmission elements of one etalon is changed, however, the angles of transmission of the etalons are mismatched and the transmission of the light through the etalons is decreased until a minimum is reached when a .lambda./4 change in light transmission element spacing of one etalon relative to the other etalon has been effected. By varying the spacing between maximum and minimum, modulation of the incoming light is effected, which modulated radiation is then collected by a detector with the resulting electrical signals then being processed for display.
Fabri-Perot spectroscopy method comprises a step of directing a light beam at a first refraction angle to a first Fabri-Perot interference plate and a step of directing a light beam transmitted through the first Fabri-Perot interference plate to a second Fabri-Perot interference plate at a second refraction angle, and Fabri-Perot spectroscopy apparatus comprises Fabri-Perot interference plates, a control device for changing a spacing between the Fabri-Perot interference plates, a first optical device for directing a light beam to the first Fabri-Perot interference plate at a first refraction angle, a second optical device for directing the light beam transmitted through the Fabri-Perot interference plate at a second refraction angle different from the first refraction angle to the second Fabri-Perot interference plate, and a seal for externally sealing the Fabri-Perot interference plates. Gas for protecting the Fabri-Perot interference plates is filled in the sealed space.
In the present equipment for spectroscopic measurement of a gas in a gas mixture, for example a gas in the atmosphere, a filter device is used to filter out one spectral line from other spectral lines belonging to other gases and the transmitted light is detected by a detector which gives a signal to devices for calculating and displaying the measurement data. The filter device consists of an interference filter (1), at least one fixed etalon (2) and a Fabry-Perot interferometer (1). In a preferred design, the filter can be fitted with two fixed etalons instead of one.
A strain sensor (50) combines an intrinsic Fabry-Perot interferometer (IFPI) (60) with an extrinsic Fabry-Perot interferometer (EFPI) (56, 62). The IFPI (60) is between two EFPIs (56,62) and shares its two air to glass minors (58, 62). The outside edges (54, 66) of the two EFPIs (56, 64) are connected to an optical fiber (52). The strain sensor (164) can be implemented on a semiconductor chip (150). A waveguide (156) on the semiconductor chip (150) is etched to form two blocks (158) with an island section (162) between them. The two blocks (158) form the EFPI and the center section (162) forms the IFPI. A strain measurement system (100) that takes advantage of the strain sensor (50) has a laser (102) coupled to a optical fiber (106) containing one or more strain sensors (108). A coupler (104) directs the reflected light from the sensors (108) to a tunable Fabry-Perot etalon (114). The output of the tunable Fabry-Perot etalon (114) is coupled to a photodetector (116). A controller (118) monitors the output of the photodetector (116) and controls the tunable Fabry-Perot etalon (114).
A multi-port optical device for transferring optical signals, or portion of optical signals, from one transmission element to another is disclosed. The inventive optical device comprises a pair of graded index lenses having an interposed Fabry Perot etalon. Moreover, the functionality of the device may be modified by varying the transmission characteristics of the etalon, which may be effected by varying the optical path length of the etalon. In operation, the optical device utilizes the graded index lenses as image transfer lenses between transmission elements wherein wavelength selectivity therebetween is afforded by the filtering mechanism associated with the etalon. The optical device may be used as a wavelength multiplexer or as an optical splitter. Moreover, by utilizing a piezoelectric transducer, the optical device may be converted to operate as an optical switch.
The system consists of a light source, a monochrometer, one or more etalons or other stable samples, a detector and a computer to store reference spectra, provide a read out indicative of the spectrum, and to change the instrument response. A transfer function is used to recharacterize the instrument's wavelength position and intensity response to match the actual spectrum with the standard spectrum. In one embodiment, the etalon is used in series with the unknown sample. A spectrum of the sample and etalon is created and is extracted from the spectrum of the sample alone to provide the actual spectrum of the instrument response to the etalon alone. The actual spectrum can then be compared to the standard spectrum and the instrument response recharacterized accordingly.
