CN100405013C - Composite optical system for solar sensor and realizing method thereof - Google Patents

Abstract

The invention discloses a combined optical system for a sun sensor, comprising photomask and microlens, where the photomask is equipped with pore, and the microlens is arranged in back of the photomask in the direction of incident light and opposite to the pore. And the invention discloses a method for implementing the combined optical system. And the invention can provide smaller diffraction facula by bigger pore and is beneficial to preventing the pore on the photomask from being stopped or polluted.

Description

The complex optics of sun sensor and its implementation

Technical field

The present invention relates to the sun sensor technology in the celestial navigation, particularly relate to complex optics and its implementation in a kind of sun sensor.

Background technology

Sun sensor is to be the reference bearing with the sun, measures a kind of attitude sensor of angle between a certain axons of spacecraft such as sun sight line and satellite or the coordinate plane.Sun sensor mainly contains " 0-1 " formula, analog, coding type and several types such as digital.Wherein, digital sun sensor is based on charge-coupled device (CCD, Charge Coupled Device) or complementary matal-oxide semiconductor (the APS CMOS of active pixel sensor, Active Pixel Sensor Complementary Metal-Oxide Semiconductor) sun sensor of new generation of imageing sensor, can satisfy the requirement of minitype spacecraft, become one of sun sensor of at present tool application prospect attitude sensor high precision, miniaturization and low-power consumption.

Digital sun sensor mainly is made up of optical system, imageing sensor and signal processing circuitry.At present, mainly utilize ripe micro electro mechanical system (MEMS) technology development based on the digital sun sensor optical system of imageing sensor, promptly on mask plate, etch aperture, adopt aperture diffraction imaging principle that the sun is carried out imaging, the diffraction pattern that is presented is radiated on the imageing sensor, calculates the attitude angle of relative solar direction then according to the centroid position of aperture diffraction pattern.Mask in these optical systems optical mask that is otherwise known as, this mask is generally aperture or array of orifices structure, and the shape in hole is based on circular and square.

The composition structure of typical sun sensor optical system and photosensitive imaging face as shown in Figure 1, sunshine is by the 2 process diffraction of the aperture on the optical mask 1, on the photosensitive imaging face 3 below the optical mask 1, form diffraction pattern 4, can determine the position parameters such as attitude angle of the sun according to diffraction pattern 4.Here, with CCD or APS cmos image sensor as photosensitive imaging face 3.Concrete image-forming principle is open in detail in the patent application document of CN200610103797.3 at the number of patent application that the applicant proposes, and does not repeat them here.

Correlative study shows that when the size of diffraction pattern 4 accounted for 3 * 3 pixels on photosensitive imaging face 3, the sun sensor bearing accuracy was the highest.Consider that from diffraction theory aperture 2 apertures on the optical mask 1 are more little, diffraction effect is big more, causes diffraction pattern 4 just big more.And consider that from the principle of pinhole imaging system aperture 2 apertures are big more, diffraction pattern 4 is also big more, illustrates that pore size and spot size are not linear ratio relations, therefore, can't obtain littler diffraction pattern 4 by the method for dwindling aperture 2 merely.

Show by result of calculation, existing sun sensor optical system minimum diffraction pattern 4 pairing apertures 2 apertures that can provide be generally about 50 microns.In this case, diffraction pattern 4 sizes are difficult to reach 3 * 3 pixels of perfect condition about 10 * 10 pixels, and the diameter that continues to dwindle aperture 2 can strengthen diffraction pattern 4 on the contrary.And, in actual applications,, be easy to cause the blocked or pollution of aperture because the aperture is too little.

Summary of the invention

In view of this, the object of the present invention is to provide complex optics and its implementation of a kind of sun sensor, can not only utilize bigger optical mask aperture that less diffraction pattern is provided, and can effectively prevent the blocked or pollution of aperture on the optical mask.

In order to realize the foregoing invention purpose, the technical solution adopted in the present invention is: a kind of complex optics of sun sensor comprises optical mask, optical mask is provided with aperture, key is: described complex optics also comprises lenticule, lenticule is arranged at the rear portion of optical mask along the incident light direction, and its position is relative with aperture on the optical mask.The optical system that claims optical mask and lenticule to form herein is a complex optics.

Wherein, described lenticule is little plano-convex lens; Described lenticule is close to the rear portion of optical mask along the incident light direction, or is positioned at optical mask and keeps at a certain distance away along the rear portion of incident light direction and with optical mask; Described lenslet dimension is greater than the orifice size on the optical mask.

The invention also discloses a kind of implementation method of sun sensor complex optics, this method comprises:

Require and computational complexity selecting hole number according to realistic accuracy earlier, and determine lenticular focal length according to the number and the aperture pitch of maximum field of view's requirement, photosensitive imaging face size, optical mask aperture; Determine lenticular plan radius and thickness by lenticule focal length, refractive index again; Determine the size of optical mask aperture according to lenticular focal length, optical wavelength, required imaging facula size; By determined lenticule and optical mask aperture parameter, make the optical mask and the lenticule of band optical mask aperture, cooperate to form the sun sensor complex optics.

The complex optics of a kind of sun sensor provided by the present invention and its implementation have the following advantages and characteristics:

The first, the present invention is provided with lenticule by adding along the rear portion of incident light direction in optical mask, utilize directional light to pass through the principle that lenticule behind the aperture forms Fu Lang and fraunhofer-diffraction, can be under the situation that increases the optical mask orifice size, on the photosensitive imaging face, form littler hot spot, make sun sensor that higher bearing accuracy can be provided.

The second, because the size of optical mask aperture needn't be as limiting very for a short time in the prior art, imaging facula wants about 10 * 10 pixels in the prior art, and the aperture will be limited in about 50 microns, and among the present invention, imaging facula reaches 3 * 3 pixels, and the aperture can increase to hundreds of microns.

The 3rd, because the aperture of optical mask aperture is bigger among the present invention, therefore, the blocked or pollution that can avoid aperture to cause because of the aperture is too little.

Description of drawings

Fig. 1 is sun sensor optical system and a photosensitive imaging face structure diagram in the prior art;

Fig. 2 is sun sensor complex optics and photosensitive imaging face structure diagram among the present invention;

Fig. 3 is sun sensor complex optics imaging schematic diagram among the present invention;

Fig. 4 is the design concept figure of little plano-convex lens among the present invention;

Fig. 5 is the present invention and prior art sun sensor single hole diffraction imaging simulated effect comparison diagram;

Fig. 6 is sun sensor double circular hole diffraction imaging simulated effect figure of the present invention;

Fig. 7 is sun sensor 6 * 6 array of circular apertures diffraction imaging simulated effect figure of the present invention.

Embodiment

The present invention is further described in more detail below in conjunction with drawings and the specific embodiments.

The present invention solves the problem that existing sun sensor optical system is difficult to form less diffraction pattern by a kind of complex optics of sun sensor is provided.The key of complex optics of the present invention is along the rear portion of incident light direction the position lenticule relative with the optical mask aperture to be set in optical mask.

The structure of sun sensor complex optics of the present invention and photosensitive imaging face as shown in Figure 2, this complex optics comprises: the optical mask 1 and the lenticule 5 that are provided with aperture 2, lenticule 5 is arranged on the rear portion of optical mask 1 along the incident light direction, and its position is relative with aperture 2 on the optical mask 1.The sunshine of approximate directional light incides optical mask 1, and 2 places see through at aperture; Effect owing to lenticule 5 forms Fu Lang and fraunhofer-diffraction then, and then forms diffraction Ai Li hot spot on the photosensitive imaging face.Among Fig. 2, the below of optical mask 1 also is provided with photosensitive imaging face 3, and photosensitive imaging face 3 keeps at a certain distance away with optical mask 1, and lenticule 5 is between optical mask 1 and photosensitive imaging face 3.

Lenticule 5 can be biconvex lens, plano-convex lens, concave-convex lens, gets final product so long as can form the lens of Fu Lang and fraunhofer-diffraction.The position of lenticule 5 can be positioned at optical mask 1 and be spaced a distance along the rear portion of incident light direction and with optical mask 1, also can directly be attached to the rear portion of optical mask 1 along the incident light direction.Herein, as long as described lenticule 5 can guarantee that with optical mask 1 distance at interval is far and near complex optics of the present invention forms effective Fu Lang and fraunhofer-diffraction imaging.

Can select plano-convex lens as the preferred embodiments of the present invention, the plane of this plano-convex lens directly is attached to the rear portion of optical mask 1 along the incident light direction, like this, helps realizing optical mask and lenticular complex optics by integrated processing.Aperture on the optical mask can be circular, square or other shapes, and as the preferred embodiments of the present invention, the aperture on the optical mask adopts circular.

The selection of lenticule 5 sizes can be bigger, equal or smaller than aperture 2, when lenticule 5 sizes than optical mask 1 on aperture 2 slightly hour, situation for big incident angle, the part incident light can occur can't be by the situation of lenticule 5, but, just can any influence not arranged to imaging for the situation of small incident or vertical incidence.In general, lenticule 5 edge imaging effects are relatively poor, can select lenticule 5 sizes to be slightly larger than aperture 2 on the optical mask 1 in the preferred embodiments of the present invention.

Select little plano-convex lens at lenticule, and little plano-convex lens directly is attached under the situation on the optical mask, the diffraction principle that complex optics of the present invention is realized as shown in Figure 3, incident light is by the aperture 2 on the mask 1, through the optically focused effect of lenticule 5, on photosensitive imaging face 3, form Ai Li hot spot 4.Its diffraction model meets the Fresnel of scalar--Kirchhoff's diffraction formula, and the mathematic(al) representation of formula is:

$\tilde{E}\left(P\right)=\frac{l}{\mathrm{i\λ}}\underset{\mathrm{\Σ}}{\∫\∫}\tilde{E}\left(Q\right)\frac{\exp \left(\mathrm{ikr}\right)}{r}\frac{\cos (n,r)-\cos (n,l)}{2}\mathrm{d\σ}$

Wherein, λ is a wavelength, (n, r) and (n, 1) be respectively the angle of aperture plane normal n of living in and r and incident ray, (n r) is α, and (n, 1) is π-θ.Sunshine is during with the parallel incident of angle θ, and the complex amplitude of any 1 P is on the photosensitive imaging face:

E(Q)＝E ₀exp(-ikx?sinθ)

Complex amplitude substitution Fresnel--Kirchhoff's diffraction formula with this point can obtain:

$\tilde{E}\left(P\right)=\frac{E_0\exp \left(\mathrm{ik}{r}_1\right)(\cos \mathrm{\α}+\cos \mathrm{\θ})}{i2\mathrm{\λf}}\underset{\mathrm{\Σ}}{\∫\∫}\exp (-\mathrm{ikx}\sin \mathrm{\θ})\exp \left({\mathrm{ikr}}_2\right)\mathrm{d\σ}$

Can determine the size and the position of Ai Li hot spot thus.

In order to realize sun sensor complex optics among the present invention, need to determine earlier the geometric parameter of the aperture on lenticular geometric shape parameters and the optical mask face.Particularly, sun sensor complex optics implementation method of the present invention mainly may further comprise the steps:

Step 1, accuracy requirement according to actual needs and computational complexity selecting hole number;

Step 2, determine lenticular focal length according to the number and the aperture pitch of maximum field of view's requirement, photosensitive imaging face size, optical mask aperture;

Step 3, determine geometric parameters such as lenticular plan radius and thickness by lenticule focal length, refractive index;

Step 4, determine the size of optical mask aperture according to lenticular focal length, optical wavelength, required imaging facula size.

Step 5, by determined lenticule and optical mask aperture parameter, make the optical mask and the lenticule of band optical mask aperture, cooperate to form the sun sensor complex optics.

As the preferred embodiments of the present invention, lenticule is selected little plano-convex lens for use.Based on this, the specific implementation step of the inventive method comprises:

Steps A, accuracy requirement according to actual needs and computational complexity are carried out the hole number and are chosen.

According to statistical theory, the optical mask of porous structure can make the random meausrement error of sun sensor reduce greatly, thereby improves its precision, and the square root of the aperture number on the raising of precision and the optical mask is directly proportional in theory.But aperture is many more, causes the complexity of post-digital signal Processing also high more, takes all factors into consideration this two factors, carries out choosing of aperture number m.

Step B, determine little plano-convex lens focal distance f.

Here, focal distance f mainly requires θ by sun sensor maximum field of view _Max, photosensitive imaging face size S, optical mask aperture radius R, optical mask aperture number m and pitch of holes L determine that according to the imaging requirements of sun sensor, focal distance f should satisfy following formula:

$f<\frac{S-2R-(m-1)\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="C20071010015000111.png,C20071010015000112.png"\; state="\{\{state\}\}">L</figure-callout>}}{2\tan {\mathrm{\&theta;}}_{\max }}$

Geometric parameters such as step C, the plan radius of determining little plano-convex lens and thickness.

Wherein, the relation of the geometric parameter of plano-convex lens as shown in Figure 4, its focal distance f satisfies:

$f=\frac{r}{N-1}$

In the following formula, r is the spherical radius of convex surface correspondence, and N is a refractive index, so just can calculate r according to focal length.On the size principle of little plano-convex lens plan radius r ' more than or equal to, even be slightly less than the optical mask pore radius and all can.But because the imaging of lenticule edge is relatively poor, thus r '＞R selected in a preferred embodiment, then according to relational expression $h=r-\sqrt{r^2-r^{\&prime;2}},$ Determine the thickness h of little plano-convex lens.

Step D, determine the little pore radius of optical mask.

The little pore radius of optical mask is decided by Fu Lang and fraunhofer-diffraction Ai Li spot radius formula:

$r_0=1.22f\frac{\mathrm{\&lambda;}}{2R}$

Wherein, r ₀Be the Ai Li spot radius, f is lenticular focal length, and λ is a wavelength, and R is the little pore radius of optical mask.

Step e, by determined lenticule focal length, plan radius and thickness, and optical mask aperture number, aperture pitch and the aperture size determined are made the optical mask and the lenticule that have aperture, cooperate to form the sun sensor complex optics.

In the prior art,, can select the little pore radius of less optical mask, be generally about tens microns in order to reach less spot radius; And need not in the present invention to limit the value of the little pore radius of optical mask too little, generally can select the little pore radius of optical mask is tens to hundreds of microns.

An act instantiation further specifies use starting condition and its implementation of sun sensor complex optics below.

Suppose that starting condition is: lambda1-wavelength λ=1um, the pixel size of photosensitive imaging face is 15um * 15um, 120 ° * 120 ° of visual field sizes.Accordingly, implementation method of the present invention is specially:

Step a, choose aperture number m=6 * 6 according to the accuracy requirement of computational complexity and actual needs;

Step b, to choose aperture pitch L be 300um, requires θ by the visual field _Max, the aperture number m on the photosensitive imaging face size S, optical mask and the pitch of holes L focal length of determining plano-convex lens is 4mm;

Step c, according to the geometric parameter of plano lens relation and refractive index, determine spherical radius r=2mm, the lens plan radius r '=300um of little plano-convex lens convex surface correspondence, lens thickness is 23um;

Steps d, establish the Ai Li hot spot and occupy 3 * 3 pixel sizes on the photosensitive imaging face, determine that thus the little pore radius of optical mask is 120um.

Step e, the optical mask aperture that 6 * 6 apertures are set on optical mask is 120um, aperture pitch is 300um, and b and c determine that parameter makes little plano-convex lens set by step, cooperate to form the sun sensor complex optics.

In this example, the photosensitive imaging face adopts imageing sensor.

According to aforementioned complex optics diffraction model, carry out the emulation of optical imagery with the parameter of complex optics in the above-mentioned example.The present invention and prior art sun sensor single hole diffraction imaging simulated effect contrast as shown in Figure 5, and wherein, a, b, c represent the Ai Li hot spot that vertical incidence, 30 degree incidents and 60 degree incident the present invention are presented respectively; And d, e, f represent that respectively the sun sensor optical system is for vertical incidence, 30 degree incidents and the 60 degree Ai Li hot spots that incident presented in the prior art, from Fig. 5, can clearly find out, the Ai Li hot spot that complex optics of the present invention is presented under various incident states is littler than prior art scope, and imaging is concentrated.

Sun sensor double circular hole diffraction imaging simulated effect of the present invention as shown in Figure 6, wherein, a, b, c represent the shape of the Ai Li hot spot that the present invention is presented when adopting double circular hole under vertical incidence, 30 degree incidents and the 60 degree condition of incidence respectively.As can be seen from Figure 6, adopt sun sensor complex optics of the present invention under the vertical incidence situation, imaging is the most concentrated, effect is also best, and along with the increase of incident angle, imaging is elongated gradually, but until incident angle is 60 degree, and hot spot still can guarantee preferable imaging effect.

Sun sensor 6 * 6 array of circular apertures diffraction imaging simulated effects of the present invention as shown in Figure 7, wherein, a, b, c represent the shape of the Ai Li hot spot that the present invention is presented when adopting 6 * 6 array of circular apertures under vertical incidence, 30 degree incidents and the 60 degree condition of incidence respectively.As can be seen from Figure 7, adopt sun sensor complex optics of the present invention, under the situation of 6 * 6 array of circular apertures and 60 degree incidents, each hot spot still imaging is clear, does not interfere mutually.

The above is preferred embodiment of the present invention only, is not to be used for limiting protection scope of the present invention.Those skilled in that art should be able to associate, and the aperture of other shapes and size is set on optical mask, and the array of orifices of varying number is selected difformity and big or small lenticule for use, all should belong to protection scope of the present invention.

Claims (6)

1. the complex optics of a sun sensor comprises optical mask, and optical mask is provided with aperture, it is characterized in that, described complex optics also comprises lenticule, and lenticule is arranged at the rear portion of optical mask along the incident light direction, and its position is relative with aperture on the optical mask.

2. the complex optics of sun sensor according to claim 1 is characterized in that, described lenticule is little plano-convex lens.

3. the complex optics of sun sensor according to claim 2 is characterized in that, described lenticule is close to the rear portion of optical mask along the incident light direction; Or be positioned at optical mask and keep at a certain distance away along the rear portion of incident light direction and with optical mask.

4. the complex optics of sun sensor according to claim 1 and 2 is characterized in that, described lenslet dimension is greater than the orifice size on the optical mask.

5. the implementation method of a sun sensor complex optics is characterized in that, this method comprises:

A, require and computational complexity selecting hole number, and determine lenticular focal length according to the number and the aperture pitch of maximum field of view's requirement, photosensitive imaging face size, optical mask aperture according to realistic accuracy;

B, determine lenticular plan radius and thickness by lenticule focal length, refractive index;

C, determine the size of optical mask aperture according to lenticular focal length, optical wavelength, required imaging facula size;

D, by determined lenticule and optical mask aperture parameter, make the optical mask and the lenticule of band optical mask aperture, cooperate to form the sun sensor complex optics.

6. implementation method according to claim 5 is characterized in that, determines the focal length basis described in the steps A $f<\frac{S-2R-(m-1)L}{2\tan {\mathrm{\&theta;}}_{\max }}$ Determine; Wherein, f is a focal length, and S is a photosensitive imaging face size, and R is the little pore radius of optical mask, and m is an optical mask aperture number, and L is a pitch of holes, θ _MaxBe the requirement of sun sensor maximum field of view.

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