CN1949024A - Non-diffraction large depth field imaging optical system - Google Patents

Abstract

The invention discloses non diffracted light big depth of scene imaging optical system. It includes object lens, collimator mirror, conic lens, image screen. The object forms the middle image by the object lens, forms approximate non diffracted beam by the collimator mirror and conic lens. The project of the beam at the any place of the screen is the concentric ring diffraction spot with the same size of which center focal spot diameter is basically determined by the conic lens. Thus the image of the object at the any place has basic same definition in required depth of scene. The distance between the medium long shot object and close shot object can be very long. And the long shot object can be infinite long. So the optical system of the invention can realize simultaneous vivid imaging at for the object with big depth of scene.

Description

A kind of non-diffraction large depth field imaging optical system

Technical field

The present invention relates to a kind of imaging optical system, specifically, is a kind of non-diffraction large depth field imaging optical system.

Background technology

Common imaging optical system is made of ordinary lens, the imaging characteristic of ordinary lens is: the incident spherical light wave that object point light source sends is transformed into another spherical light wave through behind the lens, it is the outgoing spherical light wave, the centre of sphere of outgoing spherical light wave is exactly a picture point, it does not overlap with the object point light source, and law of imagery is satisfied in their position:

$\frac{1}{F}=\frac{1}{L}+\frac{1}{L^{\′}}--------\left(1\right)$

F is the focal length of ordinary lens in the formula, and L is the distance of object point light source to lens, and L ' is the distance that picture point arrives lens.

The surface of ordinary lens is sphere normally, in order to correct aberration, aspheric surface is arranged also, but its imaging characteristic all satisfies law of imagery (1).

Common imaging optical system is by a series of different focal, is distributed in along the ordinary lens at optical axis diverse location place and constitutes, and total imaging characteristic of system is still and satisfies above-mentioned law of imagery.

Satisfy in optical system under the condition of above-mentioned law of imagery, have following characteristic:

When placing a panel vertical with optical axis at the picture point place of image space, the outgoing spherical wave will form the diffraction pattern of a minimum thereon, and according to the diffraction theory in the physical optics, the big or small ρ of hot spot is determined by the angle  that converges of outgoing spherical wave:

λ is a light wavelength in the formula.

When panel not during the picture point place at image space, the outgoing spherical wave will form one thereon than large spot, and according to geometrical optics, the big or small ρ of hot spot is:

ρ＝ΔL· (3)

Δ L is the distance between panel and picture point, just defocusing amount in the formula.

From (3) formula as can be seen, for the imaging of a single-shot luminous point, the defocusing amount Δ L of panel is big more, and the hot spot that outgoing beam forms on panel is just big more.And for the imaging of general face luminous object, because a light-emitting area is made of a large amount of luminous point, so each is put pairing picture hot spot and all can increase along with the increase of defocusing amount Δ L, therefore, the picture of face luminous object will blur along with the increase of defocusing amount.

The imaging characteristic of ordinary optical imaging system that Here it is promptly fogs along with out of focus as meeting.Therefore, if fix as panel, then only exist the object plane at a depth of field place can become clearly as, the object imaging of other depth of field position must be blured.If the ordinary optical imaging system is to being distributed in several objects imagings simultaneously of big field depth, then these objects can not on same panel, form the while clearly as.

Summary of the invention

The object of the present invention is to provide a kind of non-diffraction large depth field imaging optical system, this system has overcome the fuzzy problem of above-mentioned out of focus, make whole objects of big field depth can on same picture panel, form the while clearly as.

A kind of non-diffraction large depth field imaging optical system provided by the invention comprises the object lens, collimating mirror and the picture panel that are positioned at successively on the same light path, it is characterized in that: be provided with Conical Lenses at collimating mirror with between as panel, wherein,

The taper angle theta of Conical Lenses is calculated as follows:

$\mathrm{\θ}=2.4048\frac{\mathrm{\λ}}{\mathrm{\π}(n-1)p_x}$

Wherein, p _xBe the imaging resolution that requires, n is the refractive index of Conical Lenses;

The aperture D3 of Conical Lenses satisfies following formula and requires:

D3＞4(n-1)θL ₂

Wherein, L ₂Be the distance of picture panel to Conical Lenses;

The aperture D2 of collimating mirror is greater than the aperture D3 of Conical Lenses;

Object lens are used for that the scenery volume imaging is to the front focal plane of collimating mirror nearly, and the aperture D1 of object lens satisfies following formula and requires:

$\frac{D1}{M}\&GreaterEqual;\frac{D2}{{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="A20061012488500093.png"\; state="\{\{state\}\}">f</figure-callout>}}_2}$

Wherein, f ₂Be the focal length of collimating mirror, M is the distances of object lens to the front focal plane T of collimating mirror.

According to the present invention, a Conical Lenses is inserted between picture panel and the common imaging system, simultaneously, make in required field depth light beam that any one point sent after whole ordinary lens imaging systems of Conical Lenses front, the light beam of outgoing is directional light or the very big spherical wave of radius-of-curvature, then, these light beams are for conversion into approximate diffraction light-free through Conical Lenses again, and approximate diffraction light-free along the projection on the panel of the arbitrary position of optical axis all is being an onesize concentric ring diffraction spot, wherein the diameter of anxious spot is determined by the cone angle of Conical Lenses substantially, the out of focus fuzzy problem that can change in diverse location place focal spot size that does not have common imaging system, so in required field depth, the object imaging of arbitrary position all has same substantially sharpness.Because in optical system of the present invention, the distance between distant view object and the close shot object can be very big, distant view object even can be at infinity, therefore, blur-free imaging when optical system of the present invention can realize big depth of field object.

Description of drawings

Fig. 1 is optical system structure of the present invention and image-forming principle synoptic diagram;

Fig. 2 is the structural representation of Conical Lenses;

Fig. 3 is the optical parametric synoptic diagram of imaging system.

Embodiment

Be described in further detail below in conjunction with accompanying drawing and example structure and image-forming principle optical system of the present invention.

As shown in Figure 1, the concrete imaging process of optical system of the present invention is as follows: distant view object A and close shot object B do not wait apart from the distance of object lens 1, distant view object A is imaged onto intermediary image A1 through object lens 1, A1 forms approximate diffraction light-free bundle again behind collimating mirror 2 and Conical Lenses 3, this light beam is referred to as distant view thing projection image as being projected as A2 on the panel 4; Close shot object B is imaged onto intermediary image B1 through object lens 1, and B1 also forms approximate diffraction light-free bundle again behind collimating mirror 2 and Conical Lenses 3, and this light beam is referred to as close shot thing projection image as being projected as B2 on the panel 4.

Because the light that distant view object A and close shot object B are sent, behind object lens 1, earlier near the front focal plane T of collimating mirror 2, form intermediary image---as A1 and picture B1, character according to lens focal plane, the light beam that every bit sends on the intermediary image becomes plane wave or the very big spherical wave of radius-of-curvature after collimating mirror 2 refractions.And according to the theory of diffraction optics, the spherical wave that a branch of planar light or radius-of-curvature are very big after the Conical Lenses refraction, will form in the image space and to be similar to diffraction light-free.Diffraction light-free is the special light beam that a kind of beam cross-section light distribution does not change with the variation of the propagation distance of light.The propagation distance of desirable diffraction light-free is an infinity, and the propagation distance of approximate diffraction light-free is limited.The direction of the central shaft of plane of incidence direction of light decision outgoing diffraction light-free.Therefore, distant view object A and close shot object B go up the light that arbitrary geometric point is sent, the final different approximate diffraction light-free of central axis direction that all becomes, their projections on picture panel 4, form two groups of concentric diffraction rings, with one heart the center of diffraction ring is exactly the central shaft of the approximate diffraction light-free of outgoing and the intersection point of picture panel 4, and if be true origin with the center of ring separately, the light distribution of every group of ring is all obeyed:

$I=\frac{{\mathrm{\&pi;}}^2{(n-1)}^2{\mathrm{\&theta;}}^{2}z}{\mathrm{\&lambda;}}{J}_0^2[(n-1)\mathrm{\&theta;<figure-callout\; id="2"\; label="r"\; filenames="A20061012488500093.png"\; state="\{\{state\}\}">r</figure-callout>}2\mathrm{\&pi;}/\mathrm{\&lambda;}]-------\left(4\right)$

J wherein ₀Be Bessel's function, n is the refractive index of Conical Lenses, θ be Conical Lenses cone angle (as shown in Figure 2, θ is the bus H of circular cone and the angle of circular cone bottom surface N just), λ is an optical wavelength, r is the distance of light intensity calculation level to this group donut center, and z is the distance of Conical Lenses summit to picture panel 4.Can find out from following formula, the light distribution of diffraction ring spot is by z and r decision, on any one plane parallel (being that z is an arbitrary value) with picture panel 4, light intensity is duplicate with the relative Changing Pattern of r, promptly all meet Bessel's function, and the light intensity of any point increases with the z value is linear all on the diffraction ring, that is to say, when picture screen when optical axis moves, it is constant that the size of diffraction ring hot spot, shape, intensity distribute relatively.Distant view object A and the formed Bezier diffraction of close shot object B annulus are basic identical, as long as θ is enough big, their first Crape ring radius ρ just can be enough little, and be approximately

$\mathrm{\&rho;}=2.4048\frac{\mathrm{\&lambda;}}{2\mathrm{\&pi;}(n-1)\mathrm{\&theta;}}-------\left(5\right)$

Therefore, distant view object A and close shot object B go up the light that arbitrary geometric point is sent, and finally all form the essentially identical ring hot spot of a group switching centre speck radius size on picture panel 4.Distant view object A and close shot object B go up whole luminous points all will form own corresponding ring hot spot on picture panel 4, these ring hot spot superpositions have just constituted A2 of projection image and the B2 of distant view object A and close shot object B together.Because distant view object A is basic identical with the center spot radius size that close shot object B goes up hot spot that each geometric point becomes to encircle, therefore, although distant view object B and close shot object A are different to the distance of camera lens, their resolution of formed projection image on as panel 4 is essentially identical.That is to say that they have formed the picture of same sharpness on as panel 4.

Optical system of the present invention comprises object lens 1, collimating mirror 2, Conical Lenses 3 and the picture panel 4 that is positioned at successively on the same light path, and their mutual relationship and parameter are as shown in Figure 3.

Definite method of the focal length value of object lens 1 is, is imaged onto the requirement on the front focal plane T of collimating mirror 2 according to scenery body B nearly, determines according to ordinary lens imaging formula (1); The aperture D1 of object lens 1 and the aperture D2 of collimating mirror 2 will satisfy following relation

$\frac{D1}{M}\&GreaterEqual;\frac{D2}{f_2}---------\left(6\right)$

Wherein, f ₂Be the focal length of collimating mirror 2, M is the distances of object lens 1 to the front focal plane T of collimating mirror 2.

The aperture D2 of collimating mirror 2 is greater than the aperture D3 of Conical Lenses 3; Relational expression (6) also will be satisfied in the focal length of collimating mirror 2 and aperture.

The aperture D3 of Conical Lenses 3 satisfies formula (7):

D3＞4(n-1)θL ₂ (7)

Wherein, L2 is the distance of picture panel 4 to Conical Lenses 3; The computing method of the taper angle theta of Conical Lenses 3 are:

$\mathrm{\&theta;}=2.4048\frac{\mathrm{\&lambda;}}{\mathrm{\&pi;}(n-1)p_x}--------\left(8\right)$

Wherein, p _xIt is the imaging resolution of requirement.

For compact conformation, collimating mirror 2 is as close as possible with Conical Lenses 3, but can not contact.

The lens combination that the lens combination that object lens 1 also can be made up of some spherical lenses, collimating mirror 2 also can be made up of some spherical lenses.

The object distance Lp1 of the nearest blur-free imaging of the close shot of optical imaging system of the present invention position is:

$\mathrm{<figure-callout\; id="1"\; label="Lp"\; filenames="A20061012488500093.png"\; state="\{\{state\}\}">Lp</figure-callout>}1=\frac{{\mathrm{Mf}}_1}{M+f_1}----------\left(8\right)$

The distant view calculating formula of the object distance Lp2 of blur-free imaging position farthest is

Lp2＝∞ (9)

As seen, as long as the distance between scenery and the object lens surpasses Lp1, as being equally clearly all just.

As shown in Figure 3, optical system of the present invention is to being in object lens 1 preceding, distance L ₁The imaging enlargement factor β of the object O of place is:

$\mathrm{\&beta;}=\frac{\mathrm{Lp}3}{(L_1-\mathrm{Lp}3)}\&times;\frac{L_2}{(M+f_2)}-----------\left(10\right)$

Wherein:

$\mathrm{Lp}3=\frac{(M+f_2)f_1}{M+f_2-f_1}---------\left(11\right)$

Optical imaging system of the present invention also can not be provided with object lens 1, and before object directly being placed the front focal plane T of collimation lens 2, in this case, the nearest blur-free imaging of prospect position is exactly front focal plane T, and background farthest blur-free imaging position Lp2 be

$\mathrm{<figure-callout\; id="2"\; label="Lp"\; filenames="A20061012488500093.png"\; state="\{\{state\}\}">Lp</figure-callout>}2=\frac{{2\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="A20061012488500093.png"\; state="\{\{state\}\}">f</figure-callout>}}_2\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="A20061012488500093.png"\; state="\{\{state\}\}">L</figure-callout>}}_2}{2\&CenterDot;L_2-f_2}-------\left(12\right)$

Enlargement factor β is

$\mathrm{\&beta;}=\frac{L_2}{{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A20061012488500093.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+f_2}-----------\left(13\right)$

L in the formula ₁Be the distance of object to collimation lens 2.

Removing the other parts of Conical Lenses 3 in the optical system of the present invention, is traditional optical lens system, and wherein the principle of design of object lens is the front focal plane T that will need the nearest object image-forming of imaging to collimating mirror, and satisfies the requirement of enlargement ratio; And the principle of design of collimating mirror is to guarantee under the situation of clear aperature greater than Conical Lenses 3, reduces focal distance f as far as possible ₂

If object lens directly do not place object front focal plane T, then should design f according to the enlargement ratio β of system of formula (13) ₂

In addition, object lens and collimating mirror also should satisfy the requirement of aberration minimum.

Embodiment:

Design conditions: p _x=14 μ m, n=1.5, λ=0.65 μ m, L ₂=100mm;

Optical system parameter result of calculation:

Conical Lenses parameter: θ=0.07 radian; D=14mm; Thickness=5mm, material refractive index n=1.5

Collimation lens parameter: focal distance f ₂=192.9mm, the front surface radius-of-curvature is ∞, and the rear surface radius-of-curvature is 100mm, and thickness is 5mm, material refractive index n=1.5168.

Distance is 5mm between Conical Lenses and the collimation lens.

Object lens parameter: focal distance f ₁=97.3mm, the front surface radius-of-curvature is 100mm, and the rear surface radius-of-curvature is 100mm, and thickness is 5mm, material refractive index n=1.5168.

Between object lens and the collimation lens apart from M=106mm.

The prospect position Lp1=1000mm of present embodiment optical system, the background position is the infinite distance.

Claims (1)

1, a kind of non-diffraction large depth field imaging optical system, this system comprises object lens (1), collimating mirror (2) and the picture panel (4) that is positioned at successively on the same light path, it is characterized in that: between collimating mirror (2) and picture panel (4), be provided with Conical Lenses (3), wherein

The taper angle theta of Conical Lenses (3) is calculated by formula (I):

$\mathrm{\&theta;}=2.4048\frac{\mathrm{\&lambda;}}{\mathrm{\&pi;}(N-1)p_x}---\left(I\right)$

Wherein, p _xBe the imaging resolution that requires, n is the refractive index of Conical Lenses;

The aperture D3 of Conical Lenses (3) satisfies formula (II) and requires:

D3＞4(n-1)θL ₂ (II)

Wherein, L ₂Be the distance of picture panel (4) to Conical Lenses (3);

The aperture D2 of collimating mirror (2) is greater than the aperture D3 of Conical Lenses (3);

Object lens (1) are used for the front focal plane (T) that scenery body (B) nearly is imaged onto collimating mirror (2), and the aperture D1 of object lens (1) satisfies formula (III) and requires:

$\frac{D1}{M}\&GreaterEqual;\frac{D2}{f_2}---\left(\mathrm{III}\right)$

Wherein, f ₂Be the focal length of collimating mirror (2), M is the distances of object lens (1) to the front focal plane T of collimating mirror (2).

Images