CN104165695A - Fourier transform imaging spectrometer based on index mirror polarization interference - Google Patents

Abstract

The invention relates to a Fourier transform imaging spectrometer based on index mirror polarization interference. The imaging spectrometer comprises a polarizer (1), a first Wollaton prism (2), a second Wollaton prism (3), a polarization analyzer (4), a Fourier lens (5) and a focal plane detector (6). The thicknesses and wedge angles of the two prisms are equal, and the main sections of the two prisms are perpendicular to each other. When emitted through the first prism (2), light is transversely sheared into two beams of light perpendicular to each other in the polarization direction. On the FPA6 of the imaging spectrometer, the optical path differences of all image points change along an index mirror and namely change along with time. Accordingly, the imaging spectrometer should belong to time modulation type interference systems. The imaging spectrometer has the advantage that the large optical path differences, namely higher spectral resolution, can be achieved.

Description

Index glass polarization interference Fourier transform imaging spectrometer

Technical field

The present invention relates to a kind of instrument for light spectrum image-forming, relate in particular to a kind of index glass polarization interference Fourier transform imaging spectrometer, belong to light spectrum image-forming field.

Background technology

Fourier Transform Spectroscopy, or referred to as Fourier spectrum technology, can trace back to Michelson (Michelson) interferometer of invention in 1880; Although the original intention of this invention is the measurement for the vacuum light velocity, it has possessed the basic structure of modern Fourier transform spectrometer.Within 1891, Michelson explicitly points out, and on the receiving plane of double beam interferometer, changes the interference strength variation causing and equals the Fourier transform of tested spectrum, thereby established the theoretical foundation of modern Fourier transform spectrometer, by optical path difference.In development course subsequently, although the lot of advantages of Fourier spectrum technology is disclosed out by people, but because the needed calculated amount of high resolving power Fourier trasform spectroscopy refutation process is very large, therefore until the second half in 20th century, Fourier spectrum technology is just along with the development of digital computer technique progressively occupies spectral technique, the especially critical role in infrared spectrometry field.Particularly in nineteen sixty-five, J.W.Cooley and J.W.Tukey have invented Fast Fourier Transform (FFT) (FFT) algorithm and it have been applied on interference spectroscope, thereby the inverting of high resolving power Fourier trasform spectroscopy is shortened needed computing time greatly, also made the widespread use of Fourier trasform spectroscopy measuring technique become a reality.

Fourier spectrum technical development, to today, has not only rested on the spectral measurement for simple pointolite or area source.In order to meet the needs of various application scenarios, have imaging, high sensitivity, fast, the Fourier spectrum technology of the function such as wide spectrum, high stability or feature is also developed.Although Fourier transform spectrometer, FTS (Fourier Transform Spectrometers) just progressively enters practical as far back as the sixties in 20th century, but the concept of Fourier transform imaging spectrometer FTIS (Fourier Transform Imaging Spectrometers), until early 1990s is just suggested along with the development of remotely sensed image spectral technique, and is greatly developed.Therefore can think that Fourier spectrum technology remains a young science.Imaging spectral technology is first in the U.S., propose and grow up the end of the seventies, and it has the feature of image and spectrum unification, and the analyzing and processing of its information concentrates on expansion and the quantitative analysis that carries out image information in spectrum dimension.In remote sensing field, each state is all using interference type imaging spectral technology as prior development direction.

Fourier transform imaging spectrometer is called again picture interferometer (imaging interferometer) in a lot of documents.By scanning theory, divide, current Fourier transform imaging spectrometer roughly can be divided into time-modulation type (Temporarily Modulated) and the large class of spatial modulation type (Spatially Modulated) two.Wherein time-modulation type need to be installed index glass, and the variation of optical path difference is subject to certain restrictions.

Summary of the invention

In order to overcome the deficiencies in the prior art, resolve the problem of prior art, make up the deficiency of existing existing product in the market.

The invention provides a kind of index glass polarization interference Fourier transform imaging spectrometer, comprise the polarizer, the first prism, the second prism, analyzer, fourier lense and the focus planardetector that according to light path, arrange.

Preferably, above-mentioned the first prism and the second prism are Wollaton prism, and two prism thickness equates, the angle of wedge equates, principal section is mutually vertical.

Preferably, above-mentioned the first prism makes incident light produce angular shear.

Preferably, by Transverse Shear, be cut into the orthogonal two-beam in polarization direction during the above-mentioned light outgoing through the first prism.

Preferably, above-mentioned two-beam after lateral shear is identical through described analyzer after vibration direction.

It is temporal evolution that the optical path difference of upper each picture point of FPA6 of imaging spectrometer provided by the invention all changes with index glass, so it should range time-modulation type interference system.Its advantage is to obtain larger optical path difference, i.e. higher spectral resolution.

Accompanying drawing explanation

Fig. 1 is structural representation of the present invention;

Fig. 2 is the schematic diagram calculation of polarization interference optical path difference of the present invention.

Reference numeral: the 1-polarizer; 2-the first prism; 3-the second prism; 4-analyzer; 5-fourier lense; 6-focus planardetector.

Embodiment

For the ease of those of ordinary skills, understand and implement the present invention, below in conjunction with the drawings and the specific embodiments, the present invention is described in further detail.

Specifically as shown in Figure 1, spectrometer comprises the polarizer 1, the first prism 2, the second prism 3, analyzer 4, fourier lense 5 and the focus planardetector 6 arranging according to light path to index glass polarization interference Fourier transform imaging spectrometer of the present invention.The first prism 2 and the second prism 3 are Wollaton prism, and two prism thickness equates, the angle of wedge equates, principal section is mutually vertical.The first prism 2 makes incident light produce angular shear.During through the light outgoing of the first prism 2, by Transverse Shear, be cut into the orthogonal two-beam in polarization direction.Two-beam after lateral shear is identical through described analyzer 4 after vibration directions.

Light path principle of the present invention, it has adopted, and two thickness equate, the angle of wedge equates, the orthogonal Wollaton prism in principal section.The first prism (Wollaston) 2 can make incident light produce angular shear.The two-beam by lateral shear by the outgoing of Wollaton prism is respectively o light and e light, and their polarization direction is mutually vertical, identical through analyzer after vibration direction, then focuses on the upper generation interference of FPA6 through fourier lense (FTL) 5.The interference figure of this system is superimposed upon on the image of measured target, is similar to the situation of index glass Michelson time-modulation interference imaging system.

When light vertical incidence (i=0), i.e. light beam on axle, its optical path difference is:

l＝2(n _e-n _o)×tanθ×x (1)

Wherein, x is the center offset of incident light to optical axis, and θ is the angle of wedge of Wollaston prism.

When light is during with angle i incident, i.e. axle outer light beam, its optical path difference is:

$l=t\×\frac{n_e^2-n_o^2}{2n_o^2{n}_e}({\cos }^2\mathrm{\α}-{\sin }^2\mathrm{\α})\×i^2---\left(2\right)$

Wherein, α is the angle of the principal plane of the plane of incidence and first crystal.With reference to Fig. 1, when i is very little, have:

$i\≈\sin i=\frac{\mathrm{\ξ}}{f}---\left(3\right)$

(2) formula is brought into (1) formula, obtain

$l=t\×\frac{n_e^2-n_o^2}{2n_o^2{n}_e}({\cos }^2\mathrm{\α}-{\sin }^2\mathrm{\α})\×{\left(\frac{\mathrm{\ξ}}{f}\right)}^2---\left(4\right)$

From formula (4), there is not linear relationship in the interference point on FPA6, on FPA6 face, can not produce equidistant interference fringe along ξ direction between the distance ξ of initial point and interference light path difference 1, but produce hyperbolic curve interference fringe.Therefore can not as the system that Savart or Sagnac form, realize pushing away and sweep or window is swept.But, can utilize the structure shown in Fig. 2 to form a Wollaton and stare interference imaging system, in fact it is exactly a kind of time-modulation interference type spectral imaging system.Its crucial part is: within the cycle of staring, change the interference light path difference of each FPA6 image space simultaneously, thereby realize time-modulation by parallel the second prism (Wollaston) 3.

The optical path difference that can be derived parallel incident ray by Fig. 2 changes:

Δl＝[2(n _o-n _e)tanθ]×h

Be that optical path difference increment is directly proportional to the side-play amount h of Wollaston prism.Therefore can realize the poor sampling of aplanatism by uniform translation the second prism (Wollaston) 3.

Can find out, it is temporal evolution that the optical path difference of upper each picture point of FPA6 of imaging spectrometer provided by the invention all changes with index glass, so it should range time-modulation type interference system.Its advantage is to obtain larger optical path difference, i.e. higher spectral resolution.

The embodiment of the above is better embodiment of the present invention; not with this, limit specific embodiment of the invention scope; scope of the present invention comprises and is not limited to this embodiment, and the equivalence that all shapes according to the present invention, structure are done changes all in protection scope of the present invention.

Claims (5)

1. an index glass polarization interference Fourier transform imaging spectrometer, is characterized in that: described spectrometer comprises the polarizer (1), the first prism (2), the second prism (3), analyzer (4), fourier lense (5) and the focus planardetector (6) arranging according to light path.

2. index glass polarization interference Fourier transform imaging spectrometer according to claim 1, it is characterized in that: described the first prism (2) and the second prism (3) are Wollaton prism, and two prism thickness equates, the angle of wedge equates, principal section is mutually vertical.

3. index glass polarization interference Fourier transform imaging spectrometer according to claim 2, is characterized in that: described the first prism (2) makes incident light produce angular shear.

4. index glass polarization interference Fourier transform imaging spectrometer according to claim 3, is characterized in that: during the described light outgoing through the first prism (2), by Transverse Shear, be cut into the orthogonal two-beam in polarization direction.

5. index glass polarization interference Fourier transform imaging spectrometer according to claim 4, is characterized in that: described two-beam after lateral shear is identical through described analyzer (4) after vibration direction.