RU130698U1 - HYPERSPECTROMETER - Google Patents

Abstract

1. A hyperspectrometer containing an input lens, a diaphragm with a central slit, a collimating unit, a dispersing element, an output lens, a photodetector with a matrix, and an electronic control unit, characterized in that the optically transparent plates are mounted on both sides of the slotted diaphragm and fit tightly to it. 2. The hyperspectrometer according to claim 1, characterized in that the plates are made of glass and have a thickness of from 0.5 mm to 5.0 mm. The hyperspectrometer according to claim 1, characterized in that the slit width is from 10 μm to 30 μm. The hyperspectrometer according to claim 1, characterized in that a prism or diffraction grating is used as the dispersing element. The hyperspectrometer according to claim 1, characterized in that a CCD or CMOS sensor is used as the photodetector array.

Description

The inventive utility model relates to hyperspectrometers, that is, to remote sensing devices, and more particularly to a hyperspectral registration device for optical radiation.

Hyperspectral remote sensing of objects of various nature from mobile (spacecraft, aircraft, helicopter, car, train, etc.) provides identification of objects and their elemental composition.

The identification of objects during hyperspectral measurements is based on the ability of these probed objects to absorb and reflect light waves. The fundamental basis of the remote sensing method is the possibility of establishing a correspondence between the recorded reflected optical signal and the elemental composition of the reflecting surface. Artificial radiation, as well as solar radiation, can be used to illuminate probed objects.

An information characteristic of hyperspectral measurements is the spectrum of radiation reflected by the probed object as a function of wavelength and its state parameters. The high sensitivity of the reflection coefficients of dissimilar objects at different wavelengths distinguishes the hyperspectral method from other methods of remote sensing. Hyperspectral measurements are especially useful for solving complex problems of detecting objects, identifying their composition and processes occurring in them, highlighting differences between very close classes of objects, assessing biochemical and geophysical parameters, etc. Only hyperspectral measurements can reveal small spectral differences between the individual elements of the probed objects.

The hyperspectrometer used for remote sensing of the earth's surface is known (Kalinin A.P., Orlov A.G. and Rodionov I.D., "Bulletin of Moscow State Technical University named after N.E. Bauman", No. 3 (64), 2006 (p. 11-25.), which contains an input lens, a diaphragm with a narrow central slit, a collimating unit, a dispersing element, an output lens, a photodetector with a matrix, and an electronic control unit. The structure of the named unit includes an integrated processor.

The well-known hyperspectrometer is built according to the “pushbroom” scheme, in which a diaphragm with a narrow slit is used, which provides an overview of a narrow strip on the surface of the object.

A disadvantage of the known hyperspectrometer is the lack of noise immunity from exposure to dust particles present in the environment. Due to the use of narrow slit diaphragms, of the size of the order of tens of microns, small dust particles falling on the slit can introduce distortions into the resulting images (displayed as dark stripes).

The objective of this utility model is to create a hyperspectrometer with a dustproof diaphragm assembly.

The technical result is to improve the quality of hyperspectral images.

The task and the necessary technical result are achieved by the fact that in a hyperspectrometer containing an input lens, a diaphragm with a central slit, a collimating unit, a dispersing element, an output lens, a photodetector with a matrix and an electronic control unit, are installed on both sides of the slotted diaphragm and fit snugly against optically transparent plates (forming a dustproof diaphragm assembly).

The plates can be made of glass and have a thickness of 0.5 to 5.0 mm. The width of the central slit in the diaphragm is from 0.01 to 0.03 mm. A prism or diffraction grating can be used as a dispersing element, and CCD or CMOS matrices can be used as photodetector arrays.

The essence of the proposed utility model is illustrated by figures, where:

figure 1 shows a hyperspectral image with lines that arose due to the presence of dust particles on the diaphragm gap;

figure 2 schematically shows the strip of the instantaneous field of view of the hyperspectrometer type "pushbroom" with a narrow gap;

figure 3 presents a functional diagram of a utility model;

figure 4 schematically shows a diaphragm assembly formed by a diaphragm with protective plates, on one of which a speck of dust settled;

figure 5 presents the results of modeling the path of the rays through the diaphragm slit and their display on the surface of the photodetector matrices: a - case without a speck of dust, b - with a speck of dust on the slit; c - with a speck of dust on a protective glass.

Figure 1 is given to illustrate the effect of dust particles deposited on the diaphragm on the quality of the hyperspectral image. Black horizontal stripes worsening image quality appeared as a result of dust particles settling on the diaphragm slit.

The inventive utility model of the hyperspectrometer is designed according to the "pushbroom" scheme and the construction of the hyperspectral image is illustrated in figure 2. In this case, the image of the object is scanned along the X axis due to the movement of the aircraft, for example, an airplane, on board of which a hyperspectrometer is installed.

The structural diagram of the hyperspectrometer is shown in figure 3. The hyperspectrometer contains an input lens 1, a diaphragm unit 2, a collimating unit 3, a dispersing element 4, an output lens 5, a photodetector 6 with a matrix, and an electronic control unit 7.

The diaphragm assembly 2 comprises a diaphragm 8 with a central slot 9 (Fig. 4). On both sides of the diaphragm, tightly adjacent to its sides, protective plates 10 are installed. The number 11 denotes a speck of dust inside the slit.

Figure 5 shows the results of modeling the path of rays through a diaphragm slot 0.06 mm wide with a thickness of protective plates of 2 mm and their display on the surface of the photodetector:

and - a case without a speck of dust,

b - with a speck of dust with a diameter of 0.02 mm on the slit;

c - with a speck of dust with a diameter of 0.02 mm on a protective plate.

The dimensions of the diaphragm gap and dust particles used in the model calculations correspond to the actual sizes. Here, as an example, the path of rays from a point source entering the lens at different angles in the plane AB (figure 4), perpendicular to the diaphragm within the width of the slit. Numeral 12 denotes fragments of the surface of the photodetector matrix onto which the rays transmitted through the entire optical system are projected for the three above cases, i.e.: without a dust particle - a, with a speck of dust on the slit - b and with a speck of dust on the surface of the protective glass - c.

The aberration of the lens was introduced into the model calculations so that the display of each ray on the photodetector would have a certain size. It should be noted that for convenience, the thickness of the protective plates in figure 5 is shown conditionally, since otherwise they would have gone far beyond the boundaries of the figure.

If we take the intensity of radiation transmitted to the photodetector matrix in Fig. 5a as 100%, then for the case corresponding to Fig. 5b, approximately 31 %% of the radiation intensity passes, and for the case shown in Fig. 5c, 99.8%. As a result of the influence of a dust particle located in the diaphragm slot (Fig. 5b), dark lines appear on the hyperspectral image (in this model calculation, the order width for a dust particle with a diameter of 0.02 mm will be about 0.01-0.015 mm wide). In the case of a dust particle with a diameter of d = 0.02 mm, a focal length of the lens f = 20 mm and a flight height of a hyperspectrometer carrier of 1000 m, the dark bands on the photodetector array will correspond to 1 m on the Earth's surface.

The tests showed that the use of protective plates allows virtually eliminating the influence of dust particles in the most critical site (diffraction gap) on the quality of the obtained hyperspectral images, which confirms the industrial applicability of the proposed hyperspectrometer.

Claims (5)

1. A hyperspectrometer containing an input lens, a diaphragm with a central slit, a collimating unit, a dispersing element, an output lens, a photodetector with a matrix, and an electronic control unit, characterized in that the optically transparent plates are installed on both sides of the slotted diaphragm and fit tightly to it. 2. The hyperspectrometer according to claim 1, characterized in that the plates are made of glass and have a thickness of from 0.5 mm to 5.0 mm. 3. The hyperspectrometer according to claim 1, characterized in that the slit width is from 10 μm to 30 μm. 4. The hyperspectrometer according to claim 1, characterized in that a prism or diffraction grating is used as the dispersing element. 5. The hyperspectrometer according to claim 1, characterized in that a CCD or CMOS sensor is used as the photodetector array.

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