CN102944934B - Multilayer curve compound eye type 180 ° of Large visual angle imaging systems - Google Patents

Abstract

The invention discloses a kind of multilayer curve compound eye type 180 ° of Large visual angle imaging systems, this system comprise be arranged in order ground floor lens arra, second layer lens arra, third layer lens arra, the 4th layer of lens arra and image sensor array; Every one deck lens arra is in a spherical substrate, centered by sphere summit, place a lenticule as center lens, its optical axis crosses sphere summit and the centre of sphere, outer to arrange six lenticules with hexagonal structure at it, the optical axis included angle of these six lenticular optical axises and center lens is θ; Above-mentioned all lens arras are identical with the arrangement mode of image sensor array.The present invention adopts multilayer compound eye structural design philosophy, and the mode combined by multichannel ccd detector receives the incident light from different visual field, thus make these lens while guarantee compound eye Large visual angle characteristic, can obtain the imaging of higher picture element, one-piece construction is small and exquisite, compact, is convenient to application.

Description

Multilayer curve compound eye type 180 ° of Large visual angle imaging systems

Technical field

The present invention relates to bionic compound eyes imaging field, specifically Large visual angle imaging system.

Background technology

In recent years, bionic compound eyes imaging system causes the extensive concern of researchist, and the visual field of its uniqueness is large, volume is little, to characteristics such as the sensitivity of moving object are high, make it have very large potentiality in the application in the fields such as medical treatment, industry, national defence.Compound eye is present in a kind of small and exquisite of occurring in nature and the optical texture of precision.Be different from the single aperture imaging system known by us, compound eye is made up of many hexagonal sub-eye unit, and these hexagonal sub-eyes are arranged on a curved surface closely.Every height eye is made up of corneal lens, crystalline cone, rhabdom and photosensory cell.Because size is less, every height eye to a certain field of view imaging in space, during all sub-eye collaborative works, can only can carry out target detection to Large visual angle space.

Biological compound eye is present in the middle of insect more, and therefore compound eye overall dimensions is less, and from several microns to tens microns not etc., the number of sub-eye contained by compound eye is also from hundreds of to several ten thousand not etc. for the size of every height eye.The visual field of Compound Eye of Insects is very open, and some insect horizontal field of view scope can reach 240 °, and vertical visual field scope can reach 360 °.But the resolution of Compound Eye of Insects is very low, usually only has about 1 meter, even if the honeybee that eyesight is the strongest, its eyesight is one of percentage only having human eye also.If in the place that light is faint, their eyesight is also poorer.But Compound Eye of Insects is very high to the sensitivity of moving object, as honeybee only needs 0.01 second to the reaction time of emergent object, and human eye needs 0.05 second.In addition, because the field angle of each height eye is less, therefore to the incident light of all directions in space, all can be similar to and be considered as paraxial light, the relatively conventional wide angle imaging system of image deformation and aberration has clear superiority.

According to some good characteristics that biological compound eye shows, copy the structure of biological compound eye, there has been proposed the artificial compound eye system that many kinds are multi-form.The research initial stage, bionic compound eyes mostly adopts the form of planar lens array, comprise individual layer and sandwich construction, the field angle that this compound eye structural can reach is less, and less owing to forming the lenslet dimension of compound eye, processing technology is difficult to ensure lenticular shape parameter, makes the image quality of this compound eye poor, seldom be applied in the middle of image device, major applications obtains even light at lighting field.Along with the development of Ultraprecision Machining, manufacturing capacity improves constantly, dimensional uniformity and machining precision high, surfaceness is little, controllability is strong, can be used to realize high-precision curved bionics optics compound eye.At present, in order to realize Large visual angle imaging system, related scientific research mechanism both domestic and external investigated some curved compound eye structures, and main thought is contiguity distribution microlens array on curved substrate, each height eye lenticule all adopts hexagon aspheric surface, and its focal length is different according to present position.The field angle of the type compound eye comparatively planar structure increases, but in order to adapt to the CCD size commonly used, the type compound eye device size is less, so that it is lower that each sub-eye passage leads to light quantity, only can be responsive to high intensity object or close-range target, and picture element is poor, similar with real Compound Eye of Insects.Analyze its reason, mainly contain two aspects: be on the one hand the lens arra because the curved compound eye of present stage is also just made up of simple lens, less according to the design freedom of the known this structure of Aberration Theory, be difficult to the various aberrations of correct influences image quality, therefore each lenticular areas imaging is limited, and image quality is not high, in order to obtain larger field angle, just need to distribute more sub-eye lenticule on curved substrate, so bring very large difficulty to processing again.On the other hand, imageing sensor due to present stage is all planar structures, this structure makes each lenticular optical axis have an angle with it, and this angle brings out of focus inevitably to the picture point of lenticule peripheral field, and this is unacceptable concerning imaging system.

In sum, owing to being subject to the restriction of the factors such as present stage processing technology, image quality, not yet realizing field angle at present reaches 180 ° of scopes, and the compound eye system that compact overall structure, picture element are higher.

Summary of the invention

In order to overcome the deficiencies in the prior art, the object of this invention is to provide and a kind ofly realize the Large visual angle imaging of 180 ° of scopes, high picture element, miniaturization, curving monoblock type bionic compound eyes vision system.

For achieving the above object, technical scheme of the present invention is as follows: a kind of multilayer curve compound eye type 180 ° of Large visual angle imaging systems, comprise be arranged in order ground floor lens arra, second layer lens arra, third layer lens arra, the 4th layer of lens arra and image sensor array.Too much processing to reduce sub-eye number the difficulty brought to compound eye, adopting 7 sub-eye passages to form compound eye imaging system and realizing 180 ° of imagings.In order to be reduced to the problem of picture blind area and imaging Duplication as far as possible, and the imaging enabling whole compound eye system realize within the scope of 180 °, the structure of every one deck toroidal lens array as shown in Figure 3, in a spherical substrate, centered by sphere summit, place a lenticule as center lens, its optical axis crosses sphere summit and the centre of sphere, outer to arrange six lenticules with hexagonal structure at it, the optical axis included angle of these six lenticular optical axises and center lens is θ.

Fig. 4 is the schematic diagram of curved compound eye structure object space imaging blind area and overlay region, and as shown in fig. 4 a, true field zero lap, blind area is mainly divided into two parts.Blind area between middle center eye visual field and Zi Yan visual field, two edges, is called blind area I, and the blind area between Zi Yan visual field, two edges and 180 ° of visual field border, is called blind area II.Namely do not have sub-eye passage can to this regional imaging.Now outer circle eye axle and middle center eye axle angle theta and sub-eye field angle 2 α should meet θ=2 α.The existence of blind area will produce considerable influence to Effect on Detecting, for this reason, need increase sub-eye passage field angle, or reduce θ, make θ < 2 α, thus eliminate this blind area.As shown in Figure 4 b, when θ and 2 α reaches a certain value, blind area I just disappears, and now can obtain the following relational expression about θ and 2 α

$\sin \frac{\mathrm{\&alpha;}}{2}=\frac{\sqrt{2-\sqrt{3}\sin \mathrm{\&theta;}\sin \mathrm{\&alpha;}-2\cos \mathrm{\&theta;}\cos \mathrm{\&alpha;}}}{2}---\left(\text{1}\right)$

Wherein θ is outer circle eye axle and middle center eye axle clamp angle, and 2 α are the field angle of every height eye, just can obtain when blind area is minimum according to above formula, and the angle of half field-of view of sub-eye passage is

$\mathrm{\&alpha;}=\arctan \frac{2(1-\cos \mathrm{\&theta;})}{\sqrt{3}\sin \mathrm{\&theta;}}---\left(2\right)$

Because sub-eye number is less, in order to realize the imaging in 180 ° of field ranges, θ angle and the certain relation of α angle demand fulfillment, the arrangement relation according to each height eye passage can obtain

$\mathrm{\&theta;}+\mathrm{\&alpha;}=\frac{\mathrm{\&pi;}}{2}---\left(3\right)$

Now, the field angle of whole compound eye system can reach the imaging of 180 ° of visual fields.

Because sub-eye number is less, in order to reach the imaging within the scope of field angle 180 °, θ angle can not be too small.Because the field angle that the too small meeting of θ makes every height eye bear is very large, the complexity of sub-ocular structure can be increased like this, cannot picture be embodied as a simple lens, for this reason, select multilayer lens arrangement to increase the design freedom of sub-eye system, the imaging performance of sub-eye is improved.

The complex imaging system that every height eye passage is all made up of multi-disc lens, the aperture that can add one or more circle if desired wherein limits the light beam entering imaging system.Therefore between ground floor lens arra and second layer lens arra, be provided with aperture array, the arrangement mode of aperture array is identical with the arrangement mode of all lens arras and image sensor array.

Lens shape on above-mentioned all lens arras can be plano-concave lens, biconvex lens, positive meniscus shaped lens, biconcave lens, plano-concave lens or negative meniscus lens.The various combination of these several lens can enable its field angle reach between 60 ° ~ 70 °, and image quality is superior.Complex imaging system has lens surface face type (radius-of-curvature) parameter, lens thickness, and the design parameter such as interval and different materials refractive index between lens, add that the exact position institute Construction designing degree of freedom of aperture diaphragm can well control required focal length, the design objectives such as F number and field angle.

In the present invention, the reduction of image fault (aberration that distortion brings) is mainly realized by the rotational symmetric aspheric surface of use one, according to designing requirement and aberration correction principle, described Design of Aspherical Lenses becomes a biconcave lens, and designed non-spherical lens is positioned in whole system the last lens closing on imageing sensor, namely be positioned at (the 4th layer of lens arra) before imageing sensor, aspheric surface face type equation is

$z=\frac{{\mathrm{cr}}^2}{1+\sqrt{1-(1+k)c^2{r}^2}}+{\mathrm{\&alpha;}}_4{r}^4+{\mathrm{\&alpha;}}_6{r}^6+{\mathrm{\&alpha;}}_8{r}^8+\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;---\left(\text{4}\right)$

Wherein set z-axis as optical axis, r is that in aspheric surface, any point, to the distance of optical axis, remembers r ²=x ²+ y ², c is the curvature (i.e. the inverse of radius) at aspheric surface summit place, α ₄, α ₆, α ₈deng being repeatedly term coefficient.Wherein k is quadric surface coefficient, and k=0 represents sphere, and k=-1 represents parabola, and-1<k < 0 represents ellipsoid, and k <-1 represents hyperboloid, and k > 0 represents flat ellipsoid.

Except the 4th layer of lens arra, aperture preferable shape on lens on all the other lens arras and aperture array is as follows: the lens on ground floor lens arra are plano-concave lens, lens on second layer lens arra are biconvex lens, lens on third layer lens arra are positive meniscus shaped lens, and the aperture on aperture array is a manhole.

Known according to the above description whole compound eye needs 7 sub-eye passages, because sub-eye system belongs to poly-lens system, so need the every chip-lens array in every sub-eye system to a substrate, each substrate there is the lenslet that 7 such, arrangement as shown in Figure 2, just obtains multilayer curve compound eye structure proposed by the invention as shown in Figure 1.The optical axis of the lens in each passage is coaxial and add aperture array and enable the separately imaging and be not subject to the impact of other passages of every height eye passage.

Beneficial effect: the present invention is in view of the limitation of individual layer compound eye device in aberration correction, adopt multilayer compound eye structural design philosophy, by the mode that multichannel ccd detector combines, receive the incident light from different visual field, thus make these lens while guarantee compound eye Large visual angle characteristic, can obtain the imaging of higher picture element, one-piece construction is small and exquisite, compact, is convenient to application.While realizing whole compound eye system 180 ° of field angle, good image quality can be obtained, meet the application of catching picture rich in detail on a large scale.

Accompanying drawing explanation

The overall schematic of Fig. 1 multilayer compound eye structural;

Fig. 2 is the longitudinal sectional drawing of single sub-eye passage along optical axis direction, and the optical path-tracing figure under different field angle; Shown index path is the viewing angle within half field-of-view α/2;

Fig. 3 is the front elevation of ground floor toroidal lens array;

Fig. 4 a is the schematic diagram that curved compound eye structure object space areas imaging only has blind area;

Fig. 4 b is the schematic diagram that curved compound eye structure object space areas imaging only has overlay region.

Embodiment

Below in conjunction with the drawings and specific embodiments, illustrate the present invention further, the present embodiment is implemented under premised on technical solution of the present invention, should understand these embodiments and only be not used in for illustration of the present invention and limit the scope of the invention.

Fig. 1 is the multilayer curve compound eye lens described in the present embodiment, comprises the ground floor lens arra 1, aperture array 2, second layer lens arra 3, third layer lens arra 4, the 4th layer of lens arra 5 and the image sensor array 6 that are arranged in order; Every one deck lens arra is in a spherical substrate, centered by sphere summit, place a lenticule as center lens, its optical axis crosses sphere summit and the centre of sphere, outer to arrange six lenticules with hexagonal structure at it, the optical axis included angle of these six lenticular optical axises and center lens is θ; Above-mentioned all lens arras are identical with the arrangement mode of aperture array 2 and image sensor array 6.

As shown in the figure, 1-1,3-1,4-1,5-1 are respectively a lenticule on ground floor lens arra 1, second layer lens arra 3, third layer lens arra 4 and the 4th layer of lens arra 5, corresponding 2-1 is an aperture on aperture array, and 6-1 is a slice imageing sensor of image sensor layer.First lenticule 1-1, the second lenticule 3-1, the 3rd lenticule 4-1, the 4th lenticule 5-1 and aperture 2-1, imageing sensor 6-1 constitute a sub-eye passage of compound eye system.Similar, other lenticules on curved compound eye lens correspond other 6 sub-eye passages of aperture and imageing sensor formation, whole compound eye system is made up of 7 sub-eye passages, arrangement form according to summary of the invention and the statement about blind area and overlapping region, θ=57.6 ° can be obtained according to formula (2) and formula (3), when 2 α=64.8 °, imaging blind area is minimum, and the field angle of whole system reaches 180 °.

Fig. 2 is the optical path-tracing figure of single sub-eye passage under the longitudinal sectional drawing and different field angle of optical axis direction in the present invention.Every height eye passage is all made up of 4 lens and a circular aperture, and aperture 2-1 is between the first lenticule 1-1 and the second lenticule 3-1.The field angle of whole sub-eye system can reach 64.8 °, maximum image height y '=2.4mm, and system focal length is 3.42mm, system overall length 22.88mm.In embodiment, the first lenticule 1-1 is a plano-concave lens, and namely the first surface of lens is a plane, and second is a concave surface, and the radius-of-curvature on its surface is respectively by R ₁₁and R ₁₂represent.Second lenticule 3-1 is a biconvex lens, and namely two surfaces of lens are convex surface entirely, and the radius-of-curvature on its surface is respectively by R ₃₁and R ₃₂represent.3rd lenticule 4-1 is a positive meniscus shaped lens, and the first surface of lens is convex surface, and second is concave surface, the radius-of-curvature difference R again on its surface ₄₁and R ₄₂represent.4th lenticule 5-1 is a biconcave lens, and two surfaces of lens are concave surface entirely, and the radius-of-curvature on surface is by R ₅₁and R ₅₂represent.Second lens 3-1 has the first surface radius of curvature R of 5.22mm ₃₁and the second surface radius of curvature R of-17.69mm ₃₂, R here ₃₂for negative value does not have practical significance, just according to optical mask rule, the curved surface center of circle is just on the right side on curved surface summit, and left side is negative.Aperture is a diameter is 0.6mm, and thickness is the manhole of 0.7mm.Other each structural parameters of lens are as shown in table 1, comprise the thickness of lens, diameter, material, the clearance between refractive index and lens.

In order to the impact of removal of images distortion on compound eye system image quality, by second face R of the 4th lens 5-1 ₅₂be set to rotational symmetric aspheric surface.Its asphericity coefficient and quadric surface coefficient as shown in table 2.

Table 1

Table 2

。

Claims (4)

1. multilayer curve compound eye type 180 ° of Large visual angle imaging systems, is characterized in that: comprise be arranged in order ground floor lens arra (1), second layer lens arra (3), third layer lens arra (4), the 4th layer of lens arra (5) and image sensor array (6); Adopt 7 sub-eye passages to form compound eye imaging system and realize 180 ° of imagings, every one deck lens arra is in a spherical substrate, centered by sphere summit, place a lenticule as center lens, its optical axis crosses sphere summit and the centre of sphere, outer to arrange six lenticules with hexagonal structure at it, the optical axis included angle of these six lenticular optical axises and center lens is θ; Above-mentioned all lens arras are identical with the arrangement mode of image sensor array (6); Lens on described 4th layer of lens arra (5) are biconcave lens, and the face be positioned at before imageing sensor is rotational symmetric aspheric surface, and aspheric surface face type equation is

$z=\frac{{\mathrm{cr}}^2}{1+\sqrt{1-(1+k)c^2{r}^2}}+{\mathrm{\&alpha;}}_4{r}^4+{\mathrm{\&alpha;}}_6{r}^6+{\mathrm{\&alpha;}}_8{r}^8+\mathrm{......}$

Wherein set z-axis as optical axis, r is that in aspheric surface, any point, to the distance of optical axis, remembers r ²=x ²+ y ², c is the curvature (i.e. the inverse of radius) at aspheric surface summit place, α ₄, α ₆, α ₈deng being repeatedly term coefficient, wherein k is quadric surface coefficient, and k=0 represents sphere, k=-1 represents parabola,-1<k<0 represents ellipsoid, and k<-1 represents hyperboloid, and k>0 represents flat ellipsoid.

2. multilayer curve compound eye type 180 ° of Large visual angle imaging systems according to claim 1, it is characterized in that: between ground floor lens arra (1) and second layer lens arra (3), be provided with aperture array (2), the arrangement mode of aperture array (2) is identical with the arrangement mode of all lens arras and image sensor array (6).

3. multilayer curve compound eye type 180 ° of Large visual angle imaging systems according to claim 2, is characterized in that: the lens shape on described ground floor lens arra (1), second layer lens arra (3) and third layer lens arra (4) is plano-concave lens, biconvex lens, positive meniscus shaped lens, biconcave lens, plano-concave lens or negative meniscus lens.

4. multilayer curve compound eye type 180 ° of Large visual angle imaging systems according to claim 2, it is characterized in that: the lens on described ground floor lens arra (1) are plano-concave lens, lens on second layer lens arra (3) are biconvex lens, lens on third layer lens arra (4) are positive meniscus shaped lens, and the aperture on aperture array (2) is a manhole.