CN103776535A - Large view field type polarization spectrometer polarization accuracy calibration system - Google Patents

Abstract

The invention provides a large view field type polarization spectrometer polarization accuracy calibration system which is composed of an integrating sphere, a collimator, a diaphragm, an interference filter, a polarization state generator (PSG), an electric turntable and a computer. The calibration system adopts the integrating sphere, the collimator, the diaphragm, the interference filter and the PSG to generate a standard polarization calibration source, and large view field type polarization spectrometer polarization calibration can be realized through small view field and small aperture type parallel beam generated by the calibration source through the divided view field and stepwise linear fitting method. According to the invention, full view field polarization calibration can be performed on large view field type polarization spectrometers, and the stepwise linear fitting principle is adopted in the calibration process to process data, so the large view field type imaging polarization spectrometer polarization calibration accuracy can be greatly imprived.

Description

The precision scaling system for polarization of large visual field Intensity modulation

Technical field

The present invention relates to a kind of for skylight being carried out under the hemisphere visual field of ground the precision scaling system for polarization of the Intensity modulation of full polarization multi-spectral imaging detection.

Background technology

For a long time, the many scientists in various countries are all devoted to the correlative study of skylight, are mainly absorbed in the phenomenon of explaining skylight in early days, color, the rainbow etc. of such as sky.After Arago in 1809 has found the polarization phenomena of skylight, the polarization characteristic research of skylight starts to be subject to some scientists' attention.Large quantity research shows, skylight polarisation distribution information aerial navigation, weather forecasting, nephanalysis and over the ground the aspect such as information compensation have very important value.And can the polarisation distribution information that detect accurately skylight depend on the polarization calibration precision of detection system.Polarization calibration refers to the quantitative relationship being created as between actual atural object polarization information corresponding to the output signal of the each probe unit of picture spectrum polarizing detection system and this unit, set up the radiometric response degree formula of each pixel and the instrument matrix of polarization response degree, the final purpose of polarization calibration is in order accurately to obtain the catoptrical polarization characteristic of target according to the output data of imaging Polarization Detection system.What polarization calibration needed calibration is the instrument matrix of system.

In the process of polarization calibration, need a polarized light source, it can produce needed different polarization state in calibration process.At present conventional polarized light source is normally made up of source of parallel light, polaroid and wave plate, and the saturating folk prescription by adjusting polaroid is to just producing the light beam of random polarization state with the optical axis direction of wave plate in 0 ° of field range.After this parallel polarization light beam, add and protect after inclined to one side fan diffuser and collimation lens, polarized light can be expanded to 14 °～36 ° field ranges.But owing to treating that scaling system is hemisphere visual field Intensity modulation, its field angle is 180 °, so will guarantee that in the process of calibration the field range of the light beam of polarized light source generation covers whole visual fields for the treatment of scaling system.Under existing condition, can not find field coverage and can reach the light source of hemisphere visual field, therefore this traditional polarization calibrating method is infeasible for the Intensity modulation of large visual field.

In sum, also do not propose a kind of clear and definite, high-precision polarization scaling system both at home and abroad at present, the Intensity modulation of hemisphere visual field is carried out to accurate polarization calibration.

Summary of the invention

The object of the invention is: a kind of novel large visual field precision scaling system for polarization is provided, this scaling system can carry out the polarization calibration of full visual field to hemisphere view field imaging polarization spectrum system, in calibration process, adopt the principle of substep linear fit to carry out data processing, greatly improved the polarization calibration precision of large view field imaging Intensity modulation.

The precision scaling system for polarization of a kind of large visual field of the present invention Intensity modulation, its technical solution: this system comprises following parts:

Integrating sphere, is positioned at whole scaling system foremost, is light source uniform and stable within the scope of 350nm-2500nm for wave band is provided;

Parallel light tube, be positioned at integrating sphere after, light source that integrating sphere is sent collimation, produces parallel surface light source;

Diaphragm, be positioned at parallel light tube after, the outgoing aperture of restriction parallel surface light source, makes parallel surface light source incide follow-up scaling system with certain aperture;

Interference filter, is positioned at after diaphragm, and incident light is filtered, and the selection of its centre wavelength and wave band is relevant with target polarized systems undetermined;

Polarization state generator, be positioned at after interference filter, formed by accurate linear polarizer and accurate wave plate two parts, by rotational line polaroid and wave plate, can produce 6 kinds of standard polarized light sources, i.e. 0 degree, 45 degree, 90 degree, 135 degree linear polarization light source and left and right rounding polarization or elliptic polarization light sources.The mechanical precision of its rotating mechanism is 1 ', the Stokes parameters precision of the standard polarized light source of generation is 0.001.Incident light, after polarization state generator, can produce standard polarized light source;

Protect inclined to one side fan diffuser, after being positioned at polarization state generator, protect effect partially by adopting microlens array to realize, incident light is evenly exhaled at a certain angle, and keep the polarization state of emergent light and incident light, it protects bias can be better than 99%;

Collimation lens, is positioned at and protects after inclined to one side fan diffuser, its focal length and diameter choose with clear aperature, the field angle of polarized systems to be calibrated and to protect hot spot aperture on inclined to one side fan diffuser relevant;

Electrical turntable, is placed on target system undetermined on turntable, by the rotation of electrical turntable, makes polarized light source and treats that the relative angle between scaling system changes, thereby complete the requirement at the polarized light source of the different visual fields of calibration process.The rotation precision of electrical turntable is 2 ', meet the requirement of scaling system.

Computing machine, by computer program control, gathers the view data in calibration process, utilizes the principle of substep linear fit to carry out data processing, obtains the calibration results of polarized systems.

Principle of work of the present invention is: integrating sphere produces uniform incident light, collimate through parallel light tube, by producing the directional light light of the specific polarization state in corresponding light spectral limit after optical filter, polarization state generator, again through after protecting inclined to one side fan diffuser and collimation lens, produce the polarized light source of small field of view scope, can corresponding a part of visual field of visual field Intensity modulation greatly.Because the optical texture of Intensity modulation is that axle is rotational symmetric, so on CCD imaging surface, the instrument matrix of each pixel is also the distribution of axle Rotational Symmetry with imaging surface center O point, is identical with the instrument matrix of equidistant each pixel of O point in image planes.The instrument matrix of the each pixel that therefore only need take up an official post on Radius OR to CCD imaging surface is in theory calibrated, and can extrapolate the instrument matrix of all pixels on whole CCD imaging surface.Based on this calibration principle, the polarization calibrating method of a kind of point of visual field, substep linear fit is proposed herein.The basic skills of calibration: under initial visual field, making the angle between polarization scaling system and target system undetermined is 0 degree, by the optical axis of polarized light source and the optical axis alignment of system.Rotating accurate polaroid makes incident light be converted to respectively the polarized light of 6 kinds of polarization states with accurate wave plate, utilize the first three columns of linearly polarized light calibration instrument matrix, utilize circularly polarized light (or elliptically polarized light) calibration instrument matrix the 4th row, complete a polarization calibration in visual field.Rotate by electrical turntable afterwards, regulate polarized systems and treat the relative angle between scaling system, under different visual fields, repeat aforesaid operations, complete the calibration of full visual field.In calibration process, adopt the principle of substep linear fit to carry out data processing, complete the polarization calibration of the Intensity modulation to hemisphere visual field, greatly improved the polarization calibration precision of large view field imaging Intensity modulation.After calibrating out instrument matrix, the light source of some groups of polarization states (polarization state adopting while being different from calibration) is incided in the Polarization Detection system after calibration, system result of detection, compared with incident light polarization state, can be tried to achieve to polarization calibration precision.

The present invention's tool of comparing with existing calibration technology has the following advantages:

(1) under the condition of polarized light source that there is no hemisphere visual field, utilize the calibrating method of point visual field, solve the problem of hemisphere visual field Intensity modulation full visual field calibration.

(2) utilize the principle of substep linear fit to carry out data processing, improved polarization calibration precision.

Accompanying drawing explanation

Fig. 1 is system theory of constitution block diagram of the present invention;

Fig. 2 is rotatory polarization light source schematic diagram of the present invention;

Fig. 3 is the calibration area schematic on CCD imaging surface directions X in calibration process of the present invention;

Fig. 4 is visual field rectangle on calibration CCD imaging surface of the present invention;

Fig. 5 is polarization calibration process flow diagram of the present invention.

In figure, concrete label is as follows:

1, integrating sphere 2, parallel light tube 3, diaphragm

4, interference filter 5, polarization state generator 6, protect inclined to one side fan diffuser

7, collimation lens 8, treat scaling system 9, electrical turntable

10, computing machine

Embodiment

Below in conjunction with drawings and Examples, technical scheme of the present invention is described further.

As shown in Figure 1, the present invention includes: integrating sphere 1, parallel light tube 2, diaphragm 3, interference filter 4, polarization state generator 5, protect inclined to one side fan diffuser 6, collimation lens 7, treat scaling system 8, electrical turntable 9, computing machine 10.First, by the optical axis alignment of the optical axis of polarized light source and system, as shown in the calibration light path schematic diagram while being positioned at position 1 as the light source in Fig. 2, (along systematic optical axis, the direction gage of light transmition is decided to be Z axis, be decided to be XOY face perpendicular to the planometer of Z axis, set up coordinate system according to left-hand rule).Utilize scaling system under this position to carrying out polarization calibration along the each pixel in the rectangle A1 in 0 °～8 ° visual fields on x direction of principal axis on CCD imaging surface, as shown in Figure 3.Then,, take the summit of system first lens as the center of circle, the distance take this center of circle to light source center is radius, light source is turned in xz plane to 18 ° to position 2, as shown in Figure 2.Visual field coincidence angle before and after rotating is 2 °, each pixel in the rectangle A2 in 8 °～24 ° visual fields is carried out to polarization calibration, as shown in Figure 3.Light source is rotated further, and every rotation once, completes the polarization calibration of each pixel in a specific rectangular area in 16 ° of field ranges.Light source is rotated after 5 times, just completed the rectangle A in 0 °～+ 90 ° field ranges ₁to A ₆the polarization of all pixels calibration in region, as shown in Figure 4.By rectangle A ₁to A ₆rectangle MNN ' the M ' forming is 350 pixel sizes along the length of X-direction, equals the radius value of CCD imaging surface, and in this rectangle, the instrument matrix of the pixel of any one is

$M_{\mathrm{INS}(i,j)}=\left(\begin{array}{cccc}{\left(a_{00}\right)}_{(i,j)}& {\left(a_{01}\right)}_{(i,j)}& {\left(a_{02}\right)}_{(i,j)}& {\left(a_{03}\right)}_{(i,j)}\\ {\left(a_{10}\right)}_{(i,j)}& {\left(a_{11}\right)}_{(i,j)}& {\left(a_{12}\right)}_{(i,j)}& {\left(a_{13}\right)}_{(i,j)}\\ {\left(a_{20}\right)}_{(i,j)}& {\left(a_{21}\right)}_{(i,j)}& {\left(a_{22}\right)}_{(i,j)}& {\left(a_{23}\right)}_{(i,j)}\\ {\left(a_{30}\right)}_{(i,j)}& {\left(a_{31}\right)}_{(i,j)}& {\left(a_{32}\right)}_{(i,j)}& {\left(a_{33}\right)}_{(i,j)}\end{array}\right)$

Wherein, i and j be integer and-3≤i≤3,0≤j≤350.When i=0, M _iNS(0, j) be the instrument matrix of each pixel on imaging surface OR radius.For any one pixel N in full visual field on CCD imaging surface, can obtain the instrument matrix of this pixel by substep linear fit.If pixel N Range Imaging face center O point is n pixel, n is rounded and obtain [n] and [n+1], according to the formula of linear fit:

$\frac{M_{\mathrm{INS}(x_N,y_N)}-M_{\mathrm{INS}(0,[n\left]\right)}}{n-\left[n\right]}=\frac{M_{\mathrm{INS}(0,[0+1\left]\right)}-M_{\mathrm{INS}(0,[n\left]\right)}}{1}$

?

$M_{\mathrm{INS}(x_N,y_N)}=(M_{\mathrm{INS}(0,[n+1\left]\right)}-M_{\mathrm{INS}(0,[n\left]\right)})(n-[n\left]\right)+M_{\mathrm{INS}(0,[n\left]\right)}$

Wherein

the instrument matrix of represent pixel point N, with

represent respectively the instrument matrix that is respectively [n] and [n+1] individual pixel place in X-axis with initial point O apart.

Due to the existence in systematic error, operate miss equal error source in the process of calibration, can cause the error of instrument matrix of part pixel on OR radial direction larger.For the visual field difference value between any one pixel on this radial direction and its neighbor pixel in y direction, between 0 °～0.257 °, so little visual field difference, can think that their instrument matrix only has small especially difference.In order to improve calibration precision, the instrument matrix of adjacent two pixels in the instrument matrix of this pixel and y direction is averaged, obtain the instrument matrix value of new instrument matrix as the final calibration of this pixel, as shown in formula,

${\stackrel{\‾}{M}}_{\mathrm{INS}(0,j)}=\frac{M_{\mathrm{INS}(-1,j)}+M_{\mathrm{INS}(0,j)}+M_{\mathrm{INS}(1,j)}}{3}$

, for the instrument matrix of any one pixel N in full visual field be:

${\stackrel{\‾}{M}}_{\mathrm{INS}(x_N,y_N)}=({\stackrel{\‾}{M}}_{\mathrm{INS}(0,[n+1\left]\right)}-{\stackrel{\‾}{M}}_{\mathrm{INS}(0,[n\left]\right)})(n-[n\left]\right)+{\stackrel{\‾}{M}}_{\mathrm{INS}(0,[n\left]\right)}$

Calibrate out instrument matrix M _iNSTRUMENTafterwards, the light source of some groups of polarization states (polarization state adopting while being different from calibration) is incided in the Polarization Detection system after calibration, system result of detection, compared with incident light polarization state, can be tried to achieve to polarization calibration precision.

Polarization calibration process flow diagram of the present invention as shown in Figure 5.First build scaling system according to the theory diagram shown in Fig. 1, first, the optical axis alignment of the optical axis of polarized light source and system is placed, rotatory polarization sheet makes PSG produce 4 kinds of linearly polarized lights and two kinds of circularly polarized lights (or elliptically polarized light), every kind of polarization state reuses 5 times, gather image, record the light intensity detecting on CCD, calculate the instrument matrix of each point under this visual field; Then adjust visual field, repeat aforesaid operations process, complete in pair radius OR direction the calculating of each point instrument matrix in all visual fields.Recycling is the method for linear fit step by step, calculates the instrument matrix of whole system; Finally utilize the some groups of polarization states that adopt while being different from calibration to verify polarization calibration precision.

The content not being described in detail in instructions of the present invention belongs to the known prior art of professional and technical personnel in the field.

Claims (2)

1. the precision scaling system for polarization of large visual field Intensity modulation, is characterized in that: comprise following part:

Integrating sphere, is positioned at whole scaling system foremost, is light source uniform and stable within the scope of 350nm-2500nm for wave band is provided;

Parallel light tube, be positioned at integrating sphere after, light source that integrating sphere is sent collimation, produces parallel surface light source;

Diaphragm, be positioned at parallel light tube after, the outgoing aperture of restriction parallel surface light source, makes parallel surface light source incide follow-up scaling system with certain aperture;

Interference filter, is positioned at after diaphragm, and incident light is filtered, and the selection of its centre wavelength and wave band is relevant with target polarized systems undetermined;

Polarization state generator, be positioned at after interference filter, formed by accurate linear polarizer and accurate wave plate two parts, by rotational line polaroid and wave plate, can produce 6 kinds of standard polarized light sources, i.e. 0 degree, 45 degree, 90 degree, 135 degree linear polarization light source and left and right rounding polarization or elliptic polarization light sources.The mechanical precision of its rotating mechanism is 1 ', the Stokes parameters precision of the standard polarized light source of generation is 0.001.Incident light, after polarization state generator, can produce standard polarized light source;

Protect inclined to one side fan diffuser, after being positioned at polarization state generator, protect effect partially by adopting microlens array to realize, incident light is evenly exhaled at a certain angle, and keep the polarization state of emergent light and incident light, it protects bias can be better than 99%;

Collimation lens, is positioned at and protects after inclined to one side fan diffuser, its focal length and diameter choose with clear aperature, the field angle of polarized systems to be calibrated and to protect hot spot aperture on inclined to one side fan diffuser relevant;

Electrical turntable, is placed on target system undetermined on turntable, by the rotation of electrical turntable, makes polarized light source and treats that the relative angle between scaling system changes, thereby complete the requirement at the polarized light source of the different visual fields of calibration process.The rotation precision of electrical turntable is 2 ', meet the requirement of scaling system.

Computing machine, by computer program control, gathers the view data in calibration process, utilizes the principle of substep linear fit to carry out data processing, obtains the calibration results of polarized systems.

2. the precision scaling system for polarization of large visual field according to claim 1 Intensity modulation, it is characterized in that: the polarization calibrating method that proposes a kind of point of visual field, substep linear fit, make system in the case of the polarized light source that there is no large visual field, still can accurately carry out polarization calibration to large visual field Intensity modulation.

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