Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1995-07-14
1999-02-02
Kim, Robert
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356358, G01B 902
Patent
active
058672710
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a Michelson interferometer in which incident light is divided by a non-polarizing beam splitter into two beams which are then projected onto a stationary reflector and a moving reflector, the light beams being reflected from the respective reflectors back into the beam splitter where they are recombined to interfere with each other, and the resulting interference light being converted to an electric signal to obtain a light power spectrum of the incident light.
BACKGROUND ART
The measurement of a light power spectrum using a prior art Michelson interferometer will be described with reference to FIG. 1. Incident light 11 to be measured enters a non-polarizing beam splitter 12 where it is divided into reflected light 14 and transmitted light 15 at the reflecting/transmitting face 13 of the non-polarizing beam splitter 12 angled at 45 degrees to the incident radiation direction. The reflected light 14 and transmitted light 15 are directed at a stationary reflector 16 and a moving reflector 17, respectively. The two light beams 18 and 19 reflected from the stationary and moving reflectors 16, 17 enter the reflecting/transmitting face 13 of the non-polarizing beam splitter where they are recombined to interfere with each other, and the resulting interference light rays emerge therefrom as light beams 21 and 22 orthogonal to each other.
The stationary reflector 16 is fixed in position, so that the length L.sub.1 of the optical path is invariable along which the light travels as it is reflected from the non-polarizing beam splitter 12 and further reflected by the stationary reflector 16 back into the non-polarizing beam splitter 12. On the other hand, the moving reflector 17 is moved back and forth by a drive means, not shown, so that the length L.sub.2 of the optical path is continuously variable along which the light transmitted through the non-polarizing beam splitter 12 travels as it is reflected by the stationary reflector 16 back into the non-polarizing beam splitter 12.
One 21 of the interference rays is introduced into a light receiver 23 where it is converted into an electric signal which is in turn passed to a high-pass filter 24 from which a DC (direct current) component is extracted corresponding to a change in intensity of the interference light 21 that occurs as the moving reflector 17 is moved. The resulting DC signal is converted by an A/D converter 25 to a digital signal which may be fast-Fourier transformed at a Fourier transform processor 26. A power spectrum of the incident ray being measured corresponding to the wavelength obtained through the transformation is thus displayed at a display 27.
Incidentally, the non-polarizing beam splitter 12 has so-called polarized light-dependency in that the reflectivity (or transmittance) thereof varies depending upon the polarization state of the incident light 11. This polarized light-dependency poses the problem that incident ray 11 having different polarization states will vary in the level of power spectrum measured even if they have the same power. This will be further discussed below. Let it be that the amplitude and wavelength of the incident light 11 are E.sub.0 and .lambda., respectively; the wave number is k=2.pi./.lambda.; the amplitude reflectivity and the amplitude transmittance of the non-polarizing beam splitter 12 for P polarized light are R.sub.P.sup.1/2 and T.sub.P.sup.1/2, respectively; and the amplitude reflectivity and the amplitude transmittance of the non-polarizing beam splitter 12 for S polarized light are R.sub.s.sup.1/2 and T.sub.s.sup.1/2, respectively, and that the amplitude of the P polarized light component is E.sub.op and the amplitude of the S polarized light component is E.sub.os. Then, the intensity (power) E.sub.o.sup.2 of the incident light 11 is given in the following equation:
The amplitude E.sub.1p of the P polarized light component out of the interference light 21 entering the light receiver 23 is expressed by the following equation:
Similarly, the amplitude E.sub.1s of
REFERENCES:
patent: 4360271 (1982-11-01), Downs et al.
patent: 4693605 (1987-09-01), Sommargren
patent: 4702603 (1987-10-01), Augustyn
patent: 4893931 (1990-01-01), Lefeure et al.
patent: 5104223 (1992-04-01), Gremillion
patent: 5402230 (1995-03-01), Tian et al.
patent: 5671047 (1997-09-01), Curbelo
International Search Report, Dated Feb. 28, 1995, For International Application No. PCT/JP94/01905.
Catalog on "Laser Line Non-Polarizing Plate Beamsplitters", Melles Griot, pp. 11-5 and 11-6.
Nishina Shigeki
Tokumoto Isao
Advantest Corporation
Kim Robert
LandOfFree
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