CN101431087A - Low height imaging system and associated methods - Google Patents

Abstract

In an embodiment, a low height imaging system has: one or more optical channels and a detector array, each of the optical channels (a) associated with at least one detector of the array, (b) having one or more optical components and a restrictive ray corrector, and (c) configured to direct steeper incident angle field rays onto the at least one detector.

Description

Low height imaging system and correlation technique

The application be submitted on September 14th, 2005, title divides an application for the 200580034581.X patent application of " low height imaging system and correlation technique ".

The cross reference of related application

The application require on September 14th, 2004 submit to be entitled as " improved miniature camera " the 60/609th, No. 578 U.S. Provisional Applications and on July 8th, 2005 submit to be entitled as " light means for correcting and method " the 60/697th, No. 710 U.S. Provisional Application No., and incorporate their full content into this paper by reference.The full content of following United States Patent (USP) is also incorporated this paper by reference into: the 5th of being entitled as of people such as Cathey " optical system of having expanded the depth of field ", 748, No. 371 United States Patent (USP)s, Dowski, Jr. wait the 6th of being entitled as of people " wavefront coded phase-contrast imaging system ", 525, No. 302 United States Patent (USP)s, Dowski, Jr. wait being entitled as of people " making up wavefront coded and phase-contrast imaging system " the 6th, 783, No. 733 United States Patent (USP)s, Dowski, the 6th of being entitled as of people such as Jr. " wavefront coded optics ", 842, No. 297 United States Patent (USP)s, Dowski, the 6th, 911 of being entitled as of people such as Jr. " wavefront coded zoom lens imaging system ", No. 638 United States Patent (USP)s, and Dowski, Jr. wait the 6th, 940, No. 649 United States Patent (USP)s that are entitled as " wavefront coded imaging systems " of people.

Background technology

A recent tendency of imaging device is miniaturization.Along with cell phone be integrated with the surge of other portable handheld devices of camera, the imaging system of the compactness of miniature camera ubiquity for example.Catch requirement though the imaging device of present obtainable compactness is enough to satisfy the image of low resolution concerning personal entertainment, the great majority in them only can provide quite low image quality or its length oversize.

Fig. 1 shows exemplary imaging system 10.System 10 for example can be miniature camera, and is shown as and comprises one group of optical module 2 (being shown as including the refracting element of two separation in the drawings) and detector 4.Optical module 2 can be made by optical material, for example is formed with the PMMA of four aspheric surfaces, and focal length is that 2.6mm, F# are 2.6 in the full visual field of 60 degree.The light 5 that comes from the object (not shown) roughly passes optical module 2 along Z direction 3, and images on the detector 4.The image transitions that detector 4 will receive then in the above becomes data-signal (by 7 expressions of bigger arrow), sends into processor 8 then.18 pairs of described data-signals of signal processor are handled to form final image 9.

Still with reference to Fig. 1, the optical module 2 of system 10 is oriented to the length L (being represented by vertical double-headed arrow) that Z length (first surface that be defined as running into from incident ray, the optics group is to the distance of the front surface of detector, and represented by the double-headed arrow of level) is approximately equal to detector 4.In exemplary imaging system shown in Figure 1, the length L of detector is 4.4mm, and Z length is set to 4.6mm.

Continuation is with reference to Fig. 1, and system 10 (as many other short imaging systems) does not have enough degrees of freedom, thereby diversified optical aberration that may obviously exist in the uncontrollable system and mechanical aberration.That is to say, because the number of components of construction system is less (for example, several lens and fixture, little detector etc. are only arranged), and assembly is also very little in the compact application of for example miniature camera, therefore be difficult to realize the ideal design or the adjustment (alignment) of different assemblies, and/or in case just be difficult to all component is adjusted after the assembling.Therefore, the final image that obtains is of low quality.In addition, be very possible because the physical assemblies (for example optical module 2 and detector 4) of system 10 is not harmonized and might be introduced aberration, thereby in the course of processing, need to improve precision.Even the picture quality of the final system that obtains is relatively poor relatively, this requirement has also increased the cost of system 10.

In addition, in the imaging system 10 of prior art, the ray angles of detector 4 edges may be more shallow.That is to say that the angle θ that the chief ray of detector edge (passing the light at the center in the hole that optical module 2 limited) is become with the detector normal may be up to about 30 degree.Because the light intensity of catching at the detector place depends on and the detector angulation, therefore captive light intensity can reduce along with the increase of key light line angle.In addition, bigger ray angles can cause captive light to form wrong pixel at detector, thereby makes pixel interference (cross-talk).Therefore, because when incident ray during, utilize actual CMOS, CCD and the formed image of IR detector will variation, so big key light line angle be undesirable away from the normal of detector.Because the Z contraction in length of system when making great efforts to make the further miniaturization of system, so the ray angles problem increases the weight of and cause picture quality to reduce further.

Summary of the invention

In one embodiment, a kind of low height imaging system comprises: one or more optical channels and detector array, in described a plurality of optical channel each: (a) related with in the described detector array at least one, (b) have one or more optical modules and restricted light adjuster, and (c) be configured to incidence angle steeper the field light be directed on described at least one detector.

In one embodiment, a kind of low height imaging system comprises: detector array; And grin lens, it comprises having wavefront coded surface, and is configured to make a plurality of detectors of the steeper field light transmission of incidence angle in the described detector array.

In one embodiment, a kind of low height imaging system comprises: a plurality of optical channels; And detector array; In the wherein said optical channel each: (a) related with at least one detector in the described detector array, and (b) have an aspheric grin lens.

In one embodiment, a kind of method with wavefront coded lens that is used to form comprises: positioning lens in mould; And on the surface of described lens, add curing materials, to form the wavefront coded aspheric surface of having of described lens.

In one embodiment, a kind of low height imaging system comprises: the light transmitting material piece, have input aperture, outgoing aperture and at least one interior reflective surface, wherein transmission is reflected by described reflecting surface by the wavefront of described input aperture, and leaves the described wavefront coded outgoing aperture that has.

In one embodiment, a kind of low height imaging system comprises: a plurality of optical channels and detector array, in described a plurality of optical channel each is all related with at least one detector in the described detector array and have an aspheric terms light adjuster, and wherein said aspheric terms light adjuster preferentially makes color point to special detector in the described detector array.

In one embodiment, a kind of photon compensation optical system comprises: at least one optical element and aspheric surface, the scope of non-constant MTF between object and described optical element of wherein said system compensates.

In one embodiment, a kind of restricted light adjuster comprises close detector array placement or the optical element that is coupled with described detector array, described optical element forms at least one surface, thereby make the field light in the optical imaging system point to described detector array according to such incidence angle, promptly, described incidence angle is compared the surface normal of more close described detector array with the incidence angle of the field light that incides the detector array that does not comprise described optical element.

In one embodiment, a kind of low height imaging system comprises: first wafer, and it comprises a plurality of detectors; And second wafer, it comprises a plurality of aspherics assemblies, thereby makes the MTF of described imaging system not have zero point in the passband of described detector; Described first and second wafers are stacked the low height imaging system that has a plurality of optical channels with formation, and each in described a plurality of optical channels has at least one optical module and at least one detector.

Description of drawings

Fig. 1 shows the imaging system of prior art;

Fig. 2 shows low height imaging system, is used for a kind of configuration that chief ray is proofreaied and correct with explanation;

Fig. 3 shows low height imaging system, is used for another configuration that chief ray is proofreaied and correct with explanation;

Fig. 4 shows according to short imaging system of the present invention, and wherein said short imaging system comprises having wavefront coded grin lens;

Fig. 5 shows to incide does not have light pattern on the wavefront coded grin lens, that spend in the visual field for half 60;

Fig. 6-8 show on the visual field of a plurality of incidence angles, the ray plot that on a wavelength, intercepts as calculated of grin lens;

Fig. 9 is a series of figure that are used for the monochromatic modulation transfer function (MTF) as calculated of grin lens, and wherein modulation transfer function is the function of the angle of visual field;

Figure 10 be used for grin lens, as a series of scatter diagrams of the function of the angle of visual field and object space;

Figure 11-the 16th is corresponding with Fig. 5-10 but be used for explanation with the grin lens of the modification of wavefront coded use;

Figure 17 and 18 is the figure that are respectively applied for the coaxial emergent pupil of the system shown in Fig. 5-10 and Figure 11-16;

Figure 19-21 and 22-24 be the system shown in Fig. 5-10 and Figure 11-16 that is respectively applied for, as the picture of the sampling of the point-like thing of the function of the angle of visual field.

Figure 25 is the figure that comprises with the MTF of the imaging system of the grin lens of the modification of wavefront coded use, and MTF shown in it is before signal processing and difference afterwards;

Figure 26 and 27 shows digital filter image format and grid configuration, that be used to form the image among Figure 22-25 respectively;

Figure 28 graphic extension is used to make the system of processing of the grin lens of modification;

Figure 29 graphic extension is used to estimate the measuring system of the grin lens (for example grin lens of the modification of Figure 28) of modification;

Figure 30 is the figure of film light spectral filter response that be fit to use with the grin lens of revising, exemplary;

Figure 31 graphic extension is according to imaging system of the present invention, the visual field of using the set of grin lens in groups to increase imaging system shown in it;

Figure 32 graphic extension is used shown in it and is optionally proofreaied and correct and control the visual field that optics increases imaging system according to another imaging system of the present invention;

Figure 33 graphic extension uses the microreflection optics further to dwindle the total length of imaging system according to optional imaging system of the present invention shown in it;

Figure 34 is the ray plot that incides the light on the single lenslet of a part that constitutes lenslet array;

Figure 35 shows the lenslet array that is made of a plurality of independent lenslet shown in Figure 34 with the stereogram form, and wherein said lenslet array is suitable for being used for replacing the grin lens in groups shown in Figure 31 and 32;

Figure 36 is the ray plot that passes light that be suitable for using, the folded optics configuration in the imaging system shown in Figure 31 and 32;

Figure 37 comprises that with the graphic extension of stereogram form total volume array of the micro-optics system of several imaging systems (for example imaging system shown in Figure 31 and 32) represents;

Figure 38 with the graphic extension of broken section diagram form according to detector array subsystem of the present invention;

Figure 39 is with the part of the detector array subsystem of broken section diagram form graphic extension prior art, and light shown in the figure passes lenslet array and arrives the substrate that comprises detector array, and described subsystem does not comprise any light means for correcting;

Figure 40 and 41 is with the part of broken section diagram form graphic extension according to detector array subsystem of the present invention, light shown in the figure passes lenslet array and arrives the detector array that has according to correcting element of the present invention, and wherein said correcting element is positioned at different positions with described lenslet array;

According to light corrective system of the present invention, wherein said light corrective system comprises with stack manner and is arranged at a plurality of correcting elements on the lenslet array Figure 42 with the graphic extension of broken section diagram form;

Figure 43 is with broken section diagram form graphic extension another embodiment according to light corrective system of the present invention, and wherein said light corrective system comprises a plurality of correcting elements and color filter array;

Figure 44-46 is suitable for use as the embodiment of the correcting element of the correcting element in the light corrective system of the present invention with the graphic extension of broken section diagram form;

Figure 47 has the part of the wafer of correcting element array with the plan view forms graphic extension, and wherein the correcting element array is arranged on the array of detector elements (invisible), there is shown the embodiment of the possible shape of correcting element;

Figure 48 passes the light of exemplary correcting element with the graphic extension of broken section diagram form, and the possible light that correcting element provided of light corrective system of the present invention shown in the figure is proofreaied and correct type;

Figure 49 passes the light of the correcting element of enhancing of the present invention with the graphic extension of broken section diagram form, some possible modification of in order to strengthen light to proofread and correct correcting element itself being made shown in the figure;

Figure 50-54 passes the light of the additional embodiment of light corrective system of the present invention with the graphic extension of broken section diagram form, is used to customize the possible change of the light correction feature of light correcting element shown in it;

According to color separated function of the present invention, wherein the color separated function can be provided by a pair of correcting element that piles up Figure 55 and 56 with the form graphic extension of front view and end view;

Figure 57-59 pass the correcting element that piles up owing to light shown in it, thereby color is divided into different area of space with the color separated function of sectional top view form graphic extension Figure 55 and 56;

Figure 60 graphic extension Bayer color filtering array format;

Figure 61 graphic extension uses the correcting element that piles up that is used for producing color separated among Figure 55-59 to come the implementation space color separated, the separation function of spatial color shown in it can be customized, thereby makes the distribution of color of the color separated of last acquisition corresponding to the Bayer color filter array format shown in Figure 60;

Figure 62 is illustrated in the cutaway view form and utilizes wavelength to make illumination employed prism when the spatial dispersion, and this prism is suitable for according in the spatial color separation function of the present invention;

Figure 63 is illustrated in the broken section diagram form and utilizes wavelength to make illumination employed two-stage binary diffraction structure when the spatial dispersion, and this diffraction structure also is suitable for according in the spatial color separation function of the present invention;

Figure 64 illustrates with the broken section diagram form and shows off diffraction structure, and the described diffraction structure of showing off also is suitable for spatial color separation of the present invention;

Figure 65 is two exemplary focal length-pupil location curve charts that are used for two different wavefront coded systems, has wherein compared the characteristic curve of cube phase system and constant signal to noise ratio (snr) system;

Figure 66 is used for the figure that focal length is the ambiguity function (AF) of the system that one-dimensional linear changes;

It is 0.175 o'clock that Figure 67 shows in the normalization spatial frequency, response on the AF cross section of Figure 66 and the relation between normalized the defocusing;

Figure 68 is the figure that is used for the ambiguity function (AF) that focal length is the system of one dimension index variation;

It is 0.175 o'clock that Figure 69 shows in the normalization spatial frequency, response on the AF cross section of Figure 68 and the relation between normalized the defocusing;

Figure 70 is the figure of ambiguity function (AF) with wavefront coded traditional imaging system;

It is 0.175 o'clock that Figure 71 shows in the normalization spatial frequency, response on the AF cross section of Figure 70 and the relation between normalized the defocusing; And

Figure 72 is that explanation is used for the flow chart that is applied to the method for optical system with wavefront coded.

To should be noted that in order can clearly illustrating, may proportionally not draw some element in the accompanying drawing.

Embodiment

They a kind of like this optical system and equipment are described below, even also can improve picture quality with respect to the low clearance that the size of detector has short Z length or equivalence." weak point " or " low clearance " is defined as twice Z length less than the optical system effective focal length (distance before from the first surface of optics to detector) prevailingly.

These systems and equipment can provide other advantages, for example, though their optics, mechanical structure and digital detector have undemanding tolerance (to reduce cost), still can realize high picture quality; Use the non-customized small size optics of modification in order to realize high-quality imaging; Can use the small size optics of customization to realize high-quality imaging; Use has small size optics reflecting element, customization and realizes high-quality imaging; Use small size optics group to form high-quality image; Can use the special emergent pupil design of special-purpose imaging system, so that the SNR of detection probability or image is a constant in the object distance scope.These systems have also improved the light sensitivity of system.

Though optical system of the present invention and equipment can comprise refraction and/or diffraction element, but the main application of these add ons is not that incident light is focused on the specific position of detector for example, but under the situation that needn't make light focusing, the control incident light is towards the position of expectation, thus the incidence angle that realization is expected on detector.That is to say, the instruction that this paper provided is intended to particular form " guiding " light, perhaps in other words, " optical channel " along one or more expectations guides light so that following advantage to be provided: for example, the light intensity at detector place increases, color separated is customizable and system dimension reduces.

Fig. 2 shows the detector place that is used for solving in short imaging system, a kind of known trial of big ray angles problem.Fig. 2 shows exemplary low height imaging system 20, and it comprises optical module 12 and the detector 14 that generally is provided with along Z direction 13, this with Fig. 1 in similar along the optical module 2 and the detector 4 of Z direction 3 settings of imaging system 10.Low height imaging system 20 also comprises refraction restriction light correcting lens 22, and it is arranged on the detector 14 or near the detector 14.Refraction restriction light correcting lens 22 makes that the ray angles of some ray angles when not adopting refraction to limit light correcting lens 22 at detector 14 places is precipitous.By place the restricted light correcting lens 22 of refraction in the detector front, the maximum of the key light line angle of the system 20 among Fig. 2 is compared with the maximum of the key light line angle of system 10, can reduce 6 times, thereby reaches 5 degree.The key light line angles of final 5 degree that obtain are considered to smaller, and are positioned in the high-quality operating area of detector of most of reality.

Continuation is with reference to Fig. 2, and a potential shortcoming of system 20 is, because refraction restriction light correcting lens 22 is refrangible, so it has suitable thickness.The thickness of refraction restriction light correcting lens 22 generally is about 1mm, and this thickness is enough to make ray angles to reduce, but also potentially other aberrations is increased to the wavefront of the light 15 before the detector 14.

Fig. 3 shows optional low height imaging system 30, it comprise with Fig. 1 in the optical module 2 and the detector 4 similar optical module 12 and the detectors 14 of imaging system 10.Low height imaging system 30 also comprises diffraction-limited light adjuster 32 (for example, Fresnel lens), and it adopts with the refraction of system 20 restriction light correcting lens 32 similar modes and plays a role.Compare with refraction restriction light correcting lens 32, the thickness of diffraction-limited light adjuster 32 reduces greatly, but also provides identical functions simultaneously.Though the maximum ray angles at detector place still is about 5 degree, the thickness of diffraction-limited light adjuster 32 is less then to be meaned, before light 15 incides detector 14, in fact can't introduce additional aberration in the wavefront of light 15.In practice, according to material, the wave-length coverage of use and the spacing of diffraction zone used, the thickness of diffraction-limited light adjuster 32 can be less than 1/10mm.

A kind of method that elimination need be proofreaied and correct near the ray angles detector place or the detector is that making imaging system is the heart far away (telecentric) for image.The telecentric imaging system of image-side has the key light line angle that is basically parallel to optical axis.For telecentric lens, the ray angles at detector place can only the angle be relevant with rim ray (i.e. which light from rims of the lens to the picture plane), and the rim ray angle is relevant with the speed or the F/# of lens.Because picture point is to the distance of optical axis, and the ray angles that does not have introducing to add.In practice, imaging system preferably has heart characteristic far away, and needn't the heart strictly far away.

When detector one side of lens is seen, the image in aperture is infinitely great or approach under the infinitely-great situation, can make up short far be filled with admiration penetrate optics.When the image in aperture approached infinity, the aperture just should be positioned at last group optics front, and the distance between aperture and last group optics is the effective focal length of last group optics.For for example imaging system that is made of two elements shown in Figure 1, the distance between the aperture and second element must be approximately the focal length of second element, so that system approaches the heart far away.Yet the distance that needs to increase between two elements can obstruction be made very short imaging system this purpose.When the dioptric imaging system that design is lacked further, can not make system's heart far away to a certain extent, and also can not satisfy length constraint.

For example, a kind of improved miniature camera is described below.In cell phone camera, digital camera, endoscope, vehicular imaging system, toy, infrared (IR) imaging system, biometrics imaging system, safety system and the system relevant, can adopt similar techniques with said system.

In some embodiment in this article, provide telecentric imaging by graded index (GRIN) optics.GRIN optics change of refractive is the function of the position in optics normally.The GRIN optics has the refractive index of spatial variations, and this refractive index is given by the following formula:

n(r，z)＝∑a _ir ⁱ+b _iz ⁱ

Wherein (r z) is radially (r) and the axially refractive index of (z) to n.Summation changes along with the change of parameter i.It also is possible occurring its dependent variable in the formula of refractive index.Some variablees comprise, as along the function of the thickness z of the profile of spheric profile or lens shape and change and dynamically change the refractive index of refraction index profile.By suitable configuration GRIN optics, imaging system can be approximated to be the telecentric imaging system, and can also be short imaging system simultaneously.

Fig. 4 shows short imaging system 100, and it comprises the GRIN camera lens 104 of modification.The GRIN camera lens of revising 104 (for example is initially NSG (Nippon Sheet Glass, Japan plate pin Co., Ltd.) grin lens ILH-0.25) be modified to realize wavefront codedly, and it is short, at a high speed and the visual field of non-constant width to realize length to be set at detector 102 fronts.The grin lens of revising 104 has the front surface 106 of customization, and the front surface 106 of customization comprises the wavefront coded assembly of employing of special designs.The signal processing from the image of detector 102 that obtains at last can be used to put upside down wavefront coded space behavior and generates final picture.The rear surface 107 of the grin lens of revising 104 is oriented to almost near detector 102 or is in contact with it.One side of the grin lens of revising 104 comprises the outer surface 108 of blackening, is used for absorbing light, reduces reflection and is used as field stop (field stop).104 of grin lenses of revising based on NSG ILH-0.25 grin lens to have following parameter: focal distance f=0.25mm, F/1, diameter=250 μ m, length=400 μ m and full field of view (FOV) be 60 degree.Detector 102 for example can be 56 * 56 pixels and the cmos detector with the square pixel of 3.3 μ m.Except the front surface 106 of customization, the front surface or the rear surface of the grin lens 104 of modification can also scribble the film spectral filter.In short imaging system 100, use special-purpose surface and graded index optics to produce the optical system of the short basic heart far away of total length (Z length).Telecentric optics helps to guarantee that the key light line angle of detector surface is enough steep, within the usage range with the input angle that remains on obtainable detector.

Fig. 5-10 shows the performance with wavefront coded grin lens.Fig. 5 is illustrated in the half 60 light patterns 120 of spending in the visual field, entering many input light (being represented by dotted ellipse 122) of grin lens 124.Input light enters the front surface 125 of grin lens 124, and focuses on the rear surface 126 of grin lens 124, and wherein grin lens 124 is configured to detector 127 contiguous.Because grin lens 124 has the graded index structure, so many ray angles at detector place (by dotted ellipse 128 expressions) are all less, 20 degree or littler.Mainly by the speed decision of grin lens, wherein the speed of this grin lens is F/1 to the maximum ray angles at detector place.

Fig. 6-8 is illustrated in a wavelength place in the visual field, the light cut-away view of grin lens 124.Among Fig. 6-8 each to figure all corresponding to for difference input ray angles, go up at input face (shown in the front surface among Fig. 5 125), picture point in the aperture of grin lens and the relation of pupil point, and the scale of each figure among Fig. 6-8 is-5 microns to 5 microns.Light cut-away view shown in Fig. 6-8 represents that grin lens 124 exists a large amount of curvature of field aberration, spherical aberration, coma and astigmatism.The performance at other wavelength places also is similar.These aberrations have limited the imaging performance in all positions except coaxial (on-axis) position greatly.

Fig. 9 shows the monochromatic modulation transfer function (MTF) of the grin lens that is used for Fig. 5, and wherein monochromatic modulation transfer function is the function of the angle of visual field.As can be seen, along with the continuous increase of the angle of visual field, MTF sharply descends.At maximum field of view Jiao Chu, MTF has zero point near 110lp/mm.3.3 the maximum spatial frequency that the detector of micron pixel is caught is about 151lp/mm.Because curvature of field aberration, spherical aberration, coma and astigmatism, the picture quality that detector is caught depends on the picture position to a great extent.

Figure 10 shows the spot diagram of lens 124, and wherein the luminous point curve is the function of the angle of visual field and object space.As can be seen from Figure 10, the shape and size of spot diagram are completely different in visual field and picture plane.This difference shows that once more under the situation of big visual field configuration, grin lens imaging alone is relatively poor.

By using the wavefront coded of special-purpose optical surface by forming lens and the image of final acquisition carried out signal processing, by optics, mechanical structure, environment, processing and assemble the influence of caused aberration can be all controlled.Signal processing can improve the degree of freedom of whole system, thus the less relatively degree of freedom of the imaging system that compensation is physically lacked.

By wavefront coded, even can make ready-made graded index (GRIN) (F/1) lens image that formation has high spatial resolution (3.3 microns pixels) in the scope of big visual field (the full visual field of 60 degree) fast.Figure 11 shows and can be modified so that with the grin lens of wavefront coded use.Figure 11 shows the light patterns 130 of many input light (by dotted ellipse 132 expressions) of spending in the visual field at half 60, entering grin lens 134.Input light enters the front surface 135 of the grin lens 134 of modification, and focuses on the rear surface 126 of grin lens 134, and wherein grin lens 134 is configured to detector 137 contiguous.The ray angles at 136 places, rear surface (by dotted ellipse 138 expressions) is still smaller.Detector 137 converts the light signal that it received to the signal of telecommunication 140, and the signal of telecommunication 140 is admitted to signal processing unit 142.The signal of telecommunication 144 that obtains from signal processing unit 142 is used to form final image 146.

The grin lens of revising 134 is with the difference of the grin lens 124 of Fig. 5, has formed special-purpose surface on the front surface 135 of the grin lens of revising 134.Notice that compare with the light beam on the rear surface 126 among Fig. 5, the shape of the light beam on the rear surface 136 among Figure 11 is different.The surface of the special use that forms on the front surface 135 of the grin lens of revising 134 for example may be embodied as separable cube of phase modification of rectangle (cubic phasemodification).On mathematics, described phase modification is described to { α (x ^Λ3+y ^Λ3) }, wherein α is selected to provide the optical path difference (OPD) of the crest of 11 wavelength nearly to trough.For simplicity, choose of grin lens 134 uses of this form on special-purpose surface with modification.Various other format surfaces also are valuable and possible.Handle by signal processing unit 142 subsequently by the light signal that the grin lens of revising 134 sends and detects at detector 137 places.Signal processing unit 142 for example can compensate the phase modification that is realized by the surface of special use.For example, if special-purpose surface is configured to known wavefront coding element, 142 of signal processing units can be used to put upside down the space behavior of the phase modification that (reverse) introduce by wavefront coded light transmission so.

Figure 12-14 shows the schematic diagram that the light of the grin lens of revising 134 intercepts on single wavelength in the visual field, the scale of each figure among Figure 12-14 is-50 microns to+50 microns.These curves are only at optics, and do not comprise detector or signal processing.For other wavelength, performance is similar.As can be seen, light intercepting curve is constant as the function of the angle of visual field substantially all from Figure 12-14.For this reason, hope is constant substantially as the system responses of the function of the angle of visual field.The scale that should be noted that the light intercepting curve shown in Figure 12-14 is 10 times of the scale shown in Fig. 6-8.

Figure 15 shows the MTF of the grin lens 134 that is used to revise.These MTF do not comprise the effect of detector or signal processing yet.As can be seen, only in whole visual field, has constant substantially state at the MTF of optics.This MTF state is different fully with the MTF state of grin lens 124 shown in Figure 9.

Figure 16 shows the point range figure (Spot diagram) of the grin lens 134 of modification,, and Figure 16 shows when not carrying out signal processing again, the information relevant with optics only.As can be seen, described point range figure is constant substantially in the angle of visual field with in as the plane.The special shape of point range figure is mainly by the separable surface profile decision of the special rectangle that uses with the grin lens of revising.

Show variation by relatively Figure 17 and Figure 18 in order to the front surface 125 of the front surface 135 of distinguishing the grin lens of revising 134 and grin lens 124.Figure 17 shows the coaxial emergent pupil profile 150 of grin lens 124 with grid configuration.As can be seen, coaxial emergent pupil profile (profile) the 150th, flat substantially, and be a kind of slight curving profile.Figure 18 shows the coaxial emergent pupil profile 155 of special use of the grin lens 134 of modification.According to the wavefront coded effect of expectation, special-purpose coaxial emergent pupil profile 155 is configured to specific phase modification is introduced by in the light of its transmission.The front surface 125 of grin lens 124 and rear surface 126 are considered to flat substantially, as shown in Figure 5.For profile shown in Figure 17, crest is approximately 2.2 wavelength to the OPD of trough.On the contrary, the front surface 135 of the grin lens 134 of modification has the surface profile that can realize separable cube of phase modification of rectangle.In that (x, y) in the coordinate system, this surperficial form is { α (x ^Λ3+y ^Λ3) }, wherein constant alpha is adjusted to realize the apparent height of expectation.In the embodiment shown in Figure 18, the apparent height of the front surface 135 of the grin lens 134 of modification is configured to be approximately 11 wavelength for the coaxial crest of the grin lens revised 134 to the OPD of trough.Though it is flat that the front surface 135 of Figure 11 departs from a little, this point visually is difficult to see.

Figure 19 to 21 shows for the various angles of visual field, utilize after 3.3 microns detectors sample, adopt the grin lens revised 134 formed, as the image of the point-like thing of the function of the angle of visual field.For the separable system of rectangle, the image of point-like thing or point spread function (PSF) present distinctive triangle shown in Figure 19 to 21, and visually can change according to the angle of visual field hardly.The side length that with the pixel is the PSF of unit is about 10.

As shown in figure 11, the image that detects at detector 137 places is admitted to signal processing unit 142, to form final image.Figure 22 to 24 shows by 142 couples of PSF that handle to produce by the picture of the point-like thing of grin lens 134 formation of modification of signal processing unit.The signal processing that being used to shown in Figure 22 to 24 produces PSF is linear digital filtering.The linear digital filter that is adopted in this signal processing all positions in image field all are constant.After the PSF to the sampling of Figure 19 to 21 carries out linear filtering, spatially be compact through the PSF of filtering as can be seen from Figure 22 to 24, and be constant substantially in whole visual field.For the object space of wide region,, be similar as the PSF of grin lens 134 shown in the PSF of the function of object space and Figure 19 to 21 and Figure 22 to 24, that be used to revise though do not illustrate.

Figure 25 shows the MTF of the imaging system of the grin lens of adopt revising 134, and wherein the grin lens 134 of Xiu Gaiing is before signal processing and all adopted wavefront coded afterwards.Like that, the signal processing shown in Figure 25 is linear digital filtering shown in Figure 22-24.MTF before the signal processing is illustrated as the lower sets of curves by dotted ellipse 160 expressions, and the MTF after the signal processing is illustrated as the higher sets of curves by dotted ellipse 170 expressions.These MTF represent whole visual field and the object space scope from 3mm to 15mm.These MTF also comprise from having desirable pixel MTF 100% duty factor, 3.3 microns detectors.Return with reference to Fig. 9, become the picture quality amount also relatively poor at one times of object distance place even can recall imaging system with traditional grin lens.As can be seen from Figure 25, before signal processing, in all angles of visual field and in the object distance scope, by the system of the modification of the grin lens that comprises modification and the lower sets of curves 160 of the MTF that produces is constant substantially.Adopt identical linear digital filter to carry out signal processing for all field positions and object distance, produced MTF with a higher sets of curves group 170 expressions.The MTF that should be noted that a higher sets of curves group 170 expressions has identical height (MTF that the traditional grin lens of supposition employing obtains comprises the pixel MTF of 3.3 microns desirable pixels) with the coaxial MTF of the optimum focusing of adopting traditional grin lens to obtain.

Figure 26 and 27 expressions are used for forming the linear digital filter of the figure of the image of Figure 22-24 and Figure 25.Figure 26 shows the expression of linear digital filter with image format 500, and Figure 27 shows the expression of linear digital filter with grid configuration 550.Shown in Figure 26 and 27, linear digital filter spatially is compact, and has the value of few uniqueness.This digital filter is enough to realize in the hardware handles platform on calculating.In the embodiment shown in Figure 26 and 27, all values of digital filter and equal 1.The root sum square of the square value of this filter has provided after adopting this filter, the approximation of the RMS of the additive noise of generation gain (or noise gain).Thereby through calculating, the noise gain of this exemplary digital filter is 3.2.

Figure 28 shows the embodiment according to the system of processing 800 of grin lens 802 embodiment, that be used to produce modification.The grin lens of revising 802 comprises traditional grin lens 804, has increased special-purpose phase place surface (specializedphase surface) 806 on traditional grin lens 804.Special-purpose phase place surface 806 is formed at the front surface 808 of traditional grin lens 804, and adopts moldable material, such as, but be not limited to UV curing materials, epoxy resin, adhesive or materials similar.The shape on special-purpose phase place surface 806 is decided by the shape on the machining surface 810 of pin (pin) 812.The surface 810 of pin 812 is machined to form the accurate reverse side of representing special-purpose phase place surface 806 desirable surface profiles.Therefore, the form taked of moldable material (thereby form special-purpose phase place surface 806) is by machining surface 810 decisions of pin 812.The shape on special-purpose phase place surface 806 for example can be aspheric surface.That is to say that normally used other pins are similar in pin 810 and the injector.Before inserting traditional grin lens 804 in the systems of processing 800, the moldable material of the some measured is increased to the machining surface 810 of pin 812.Ring (collar) 814 holds traditional grin lens 804, and pushes traditional grin lens 804 so that it is against pin 812.For example, if the UV curing materials as moldable material, can solidify light 816 and make it pass grin lens 804 by 818 introducing UV so from the back side.The back side 818 of tradition grin lens 804 also can be coated with film spectral filter 820.If before mold pressing is carried out on the phase place surface 806 of special use, spectral filter 820 is increased to traditional grin lens 804, and with the moldable material of UV curing materials as special-purpose phase place surface, 820 of the spectral filters light that should be configured to make the UV that is suitable for employed specific UV curing materials to solidify wavelength passes through so.In addition, pin 812 and ring 814 can scribble for example TEFLON

Non-adhesive material is so that be easy to discharge the grin lens 802 of modification after processing.

Referring now to Figure 29 and describe the measuring system 830 of the grin lens (grin lens 802 of for example modification of Figure 28) be used to estimate modification in conjunction with Figure 28.After taking off pin 812, but taking off before the ring 814, the grin lens 802 of modification is used to form the image 840 of test object 842, test object 842 for example is point-like object, bar chart or other suitable objects of being used to test.Micro objective 844 can be used for making the image 840 that forms on the rear surface 818 of the grin lens of revising 802 to focus on.Micro objective 844 and imaging len 846 co-ordinations so that image 840 is transferred on the remote probe device array 848, become the picture 850 that is transferred.Object lens 844 are for example alternatively by unlimited proofread and correct (infinitycorrected).In the embodiment shown in Figure 29, suppose that object lens 844 are infinitely proofreaied and correct.By test object 842 is imaged on the detector array 848, encircle 814 simultaneously and still be attached on the grin lens 802 of modification, just can repeat to examine the quality of the poor picture 850 that is transferred.Whether the phase place surface of the special use of the lens by indicating special modification needs to process again, and measuring system 830 can be used to improve the quality of the grin lens 802 of special modification.Like this, measuring system 830 can be used to the reliable processing of the grin lens accelerating to revise.When adhering in processing grin lens group and according to set of lenses, the processing method that can walk abreast and use this test and reform.

Figure 30 shows the exemplary film spectrum filter response 870 of the grin lens (for example grin lens of the modification of Figure 28) that is used to revise.Table 1 has been described the embodiment of possible configuration of the film spectral filter of Figure 30.Table 1 has been listed the layers of material and the thickness (i.e. prescription) of the logical spectral filters of 13 layer film bands.The imaging passband of this 13 layer film filter is about 50nm.The UV passband is slightly less than the wide bandwidth of 50nm.By the different layers in the suitable design filter, can make the imaging bandwidth of spectral filter enough wide, to cover visible light wave range.By designing the wavefront coded front surface and the signal processing mode of final image, can remove usually the influence of the color aberration that produces by traditional grin lens.

Material thickness (nm)

Air N/A

TiO ₂ 75.56

SiO ₂ 93.57

TiO ₂ 34.13

SiO ₂ 86.48

TiO ₂ 58.57

SiO ₂ 45.05

TiO ₂ 63.34

SiO ₂ 113.25

TiO ₂ 94.20

SiO ₂ 108.37

TiO ₂ 105.07

SiO ₂ 145.66

TiO ₂ 100.20

Substrate (grin lens)

Table 1

Temporarily get back to Fig. 4, the maximum image size of the grin lens 104 of modification is subjected to the restriction of refractive index excursion in the grin lens volume in practice.In grin lens, refraction index changing 0.1 is considered to general.0.3 of refraction index changing is considered to uncommon.Though the bigger change of this refractive index still needs size of images and present available refraction index changing are carried out balance becoming general day by day in the future.

Figure 31 shows and is used to a kind of system of making the larger object imaging and being used to form the bigger image of size.System 900 comprises the group 902 of a plurality of grin lenses 904, in order to form bigger image.In a plurality of grin lenses 904 each for example can be the grin lens 802 of the modification among Figure 28 or traditional grin lens 804.In a plurality of grin lenses 904 each images on the detector 912 the less field of regard 906 (being the object part that each grin lens is seen) of larger object 908, and detector 912 converts the optical image of surveying to viewdata signal 917.Then, in signal processor 918, viewdata signal 917 is handled, to generate final image 919.Therefore, total picture size of final image 919 size of images that may generate than utilizing any one grin lens separately is much bigger.

In Figure 31, the group 902 of a plurality of grin lenses 904 is configured to realize the continuous covering of whole objects 908.The field of regard 906 of each grin lens can be overlapping with the visual field of the aspect of any other grin lens.System 900 can comprise control optics 920 alternatively, in order to control the visual field part of independent grin lens.In Figure 31, show control optics 920 with the refraction configuration, but also can adopt other configurations.For example, in the diffraction configuration, control optics 920 can comprise one or more prisms, and wherein prism has the additional surfaces variant that is used for optical correction.This prism can also directly be installed to the front surface of grin lens group.Control optics 920 also can be configured to show luminous power and carries out some aberration balancing.

Referring now to Figure 31 and in conjunction with Fig. 4, increase to the wavefront coded surface of grin lens 104 front surfaces of Fig. 4, for example can adopt one of following three kinds of modes to realize in the system 900 of Figure 31: 1) aspheric surface can increase to independent refraction and/or diffraction control optics, for example controls the part of optics 920; 2) aspheric surface can directly increase to each the front surface in a plurality of grin lenses 904 of group in 902; Perhaps 3) front surface of customization can be incorporated in the design of each the independent grin lens in the group 902 influence of imaging wavefront.Should be noted that the third cited method do not need shown in the processing method shown in the image pattern 28 like that, enclose or form special-purpose aspheric surface in the front surface or the rear surface of each grin lens.

Still with reference to Figure 31, between the group 902 of grin lens 904 and detector 912, optional correcting plate 922 can be set or free space only is set.For example, if diffraction element or volume element so then can alleviate the additional aberrations from each grin lens as correcting plate 922.If adopt free space to replace correcting plate 922, the effect of propagating by free space can help child picture (sub-image) border between the level and smooth independent grin lens so.In addition, can make the border between the grin lens just black, to act on as field stop (fieldstop).

Continuation is with reference to Figure 31, because each grin lens 904 all makes different field of regard 906 imagings, and therefore can independent grin lens and the corresponding wavefront coded optics thereof of special designs for the visual field of broad.In addition, the optical characteristics of customizable each grin lens, so that with the imaging preferably of special incidence angle, wherein grin lens receives the light that comes from object with this incidence angle.Like this, coaxial observation grin lens and off-axis (off-axis) observation grin lens intrinsic aberration can obtain Optimal Control.Can also customize the signal processing 918 that is used to produce final picture 919 for each independent grin lens.The signal processing that is adopted for example can be similar with the linear filtering shown in Figure 26 and 27.

Referring now to Figure 32 and in conjunction with Figure 31, Figure 32 shows the another kind of form of the group of (adopting wavefront coded) grin lens system.Except the control optics, system and the system among Figure 31 900 shown in Figure 32 are similar.The system 900 of image pattern 31 is such, and system 950 comprises the group 952 of a plurality of grin lenses 954.Yet different with system 900 is, system 950 comprises control optics 955, and different field of regards 956 certain distance before detector 912 that control optics 955 is configured to object 958 intersects.System 950 this disposes some requirement that helps reduce to signal processor 964 when detected image is carried out signal processing.The multiplication factor of the group 952 of grin lens 954 can be for negative, so that image is put upside down.As can be seen from Figure 31, for single grin lens, object 908 images on the detector 912 in the position of close optical axis away from the part of optical axis (promptly starting from the surface normal at detector 912 centers).Then, need carry out signal processing 918, so that the child that is produced by each field of regard 906 is looked like to classify and multiplication factor is proofreaied and correct.There is not this multiplication factor problem in the system 950 of Figure 32 because in special grin lens, object 958 away from the part of optical axis in position imaging away from optical axis.Therefore, do not need to put upside down the child picture that is obtained.

Continuation is with reference to Figure 31 and 32, and Figure 31 and 32 signal processing 918 and 964 still must be removed undesirable distortion respectively and the illumination that may occur along with diminishing of the angle of visual field reduces, and must remove by wavefront coded and cause image blurring.Will be appreciated that distortion can increase usually, owing to the image visual field along with the GRIN optics increases, and illumination can reduce.Before or after removal is fuzzy, can carries out distortion and illumination and proofread and correct.For example can adopt the simple linear filter shown in Figure 26 and 27 to remove fuzzy.

Be incorporated into the example reflection in the minitype optical device as shown in Figure 33 by reduction, can reduce the total length D of reflection imaging system 980.Among the embodiment shown in Figure 33, reflective optical device 982 comprises first surface 984, and first surface 984 for example can be reflecting surface or plane of refraction, perhaps comprises Fresnel lens.Reflective optical device 982 also comprises additional reflecting surface 986 and 988, with the wavefront of further modification by the light 990 of reflective optical device 982.On reflecting surface or therein near reflecting surface, the aperture diaphragm (not shown) can also be set therein.In addition, on final face 992, can introduce additional phase modification.The material that constitutes reflective optical device 982 can be GRIN material, general volume element or homogeneous material.The reflecting surface 986 and 988 the reflective optical device 982 that exists for have been introduced additional degrees of freedom, and these additional reflectings surface can provide further customizability, with the reduction of compensation degree of freedom when with homogeneous material replacement GRIN or general volume material.It is the heart far away substantially that reflection imaging system 980 can be configured to.That is to say, can make by the key light line angle of reflective optical device 982 less, thereby make the final incidence angle at detector 994 places less, and then guarantee that reflection imaging system 980 operates as telecentric system substantially.Can further control the key light line angle of the light that sends by reflection imaging system 980, to reduce the detector loss of intensity.On other surfaces of reflective optical device 982, also can realize reflecting surface or diffraction surfaces.If final face 992 keeps flat, 982 of reflective optical devices can be directly installed on the surface of detector 994 according to the mode of the grin lens 104 that is similar to Fig. 4 so.Be directly installed on the detector or the machining tolerance that can reduce system on the detector cover plate greatly that is installed in of equal value.Yet, be impracticable if reflection imaging system 980 is directly installed on the detector 994, imaging system 980 can also be installed in the position that certain distance is arranged with detector so.

Figure 34-36 shows Figure 31 and 32 extensively other configurations of the optical module of representative.As discussed earlier, Zhuan Yong grin lens group is as the basis of Figure 31 and 32.Generally speaking, there is the imaging configuration of many other types to can be used to replace the grin lens array.That is to say, utilize group that independent optics constitutes can realization and Figure 31 and 32 described in the functionally similar function of configuration.For example, optical element in groups is except can being the grin lens in groups 902 and 952 in Figure 31 and 32, it can also be the simple lenslet (lenset) 1201 among Figure 34, wherein can send Ray Of Light (by dotted ellipse 1205 expressions), and the lenslet among Figure 34 1201 can constitute the lens arra 1210 among Figure 35 by lenslet 1201.The format surface of array 1210 may be summarized to be and comprises wavefront coded aspheric optics, thus grin lens realize and Figure 11-25 shown in the type of imaging performance can adopt lenslet array to realize.Also can adopt a plurality of lenslet array, and a plurality of lenslet array are piled up along optical axis, to improve into the picture quality amount gradually.By the installation feature that on array, forms or by independent array isolator, the interval between the imaging array that can keep piling up along optical axis.Array isolator (arrayspacer) is essentially the optical disc that refractive index is different from the refractive index of array optical element, can be the non-optical disc in the hole at center for the optical axis that has with the array optical element perhaps.

Figure 36 shows operable another kind of optical arrangement in the lens in groups 902 and 952 of Figure 31 and 32.The folding optics 1220 that adopts among Figure 36 plays the effect of the path doubling (fold) that makes optical axis, has the additional optics degree of freedom with permission on reflecting surface, and allows the direction of detector plane to change.Therefore, change the direction of the light shafts 1225 that pass folding optics 1220, so that it approximately becomes 90 degree with incident direction.Can adopt this folding optical arrangement of single physical assembly structure, install and aim to simplify.

Described up to now minitype optical device generally has the above material of one deck that light is passed through.Figure 31 and 32 shows three different layers.Ground floor shown in the figure (920 and 955) is as proofreading and correct and the control optics.The optics 902 in groups and the 952 pairs of light are assembled and are made it towards the detector transmission.Layer 922 is as further correcting plate.In these layers each layer can be with the form processing of array, so that the system 900 of Figure 31 and 32 and 950 significant components are duplicated across array and along array.Can be by from array, cutting off or downcut the single component that the assembly that needs obtains the system that is suitable for 900 and 950.As everyone knows, on silicon substrate or wafer, process for example electronic sensor of cmos sensor with the form of array.Can obtain single-sensor from wafer by cutting.

Figure 37 shows the general array of micro-optics system and represents, and the system 900 and 950 of Figure 31 and 32 is specific embodiments of described micro-optics system.Figure 37 shows the system 1230 that is made of the wafer that piles up.The array of the optical element of processing is also called " wafer optics " 1232 and 1234 in Figure 37.In wafer optics 1232 and 1234, the optics of each rhombus 1233 expression transducer level.The optical device array that wafer 1236 in the image pattern 37 plays the adjuster effect like that is also called " correcting element wafer ".In correcting element wafer 1236, details is in pixel level, and duplicates with the transducer level.If the coupling of aiming at of the ratio of duplicating of all wafers optics and locus and CMOS wafer 1238, so all the set of wafer optics and electronic component can be held together, to form the array of imaging system.In CMOS wafer 1238, the transducer of a N * M pixel of each square 1239 expression.Can cut this array, add the full set of electronic component with the optics that forms assembling.That is to say that wafer can be held together, the wafer that will pile up cuts into independent transducer and optics then.Generally speaking, can adopt one or more independent wafers to be embodied as the function of picture optics and calibrating optical device.Utilization can be optimized the particular design of these elements to the design of sensor pixel, catches and sensitivity to strengthen light.

Temporarily get back to Figure 31 and 32, describe control optics 920 and 958 the calibrating optical device and the details of control optics among Figure 31 and 32 for example respectively in further detail.To proofread and correct optics and control optics when described imaging system is used so far, can become to have additional function with proofreading and correct optics and controlling optical device designs, so that further advantage to be provided.

The wafer 1236 and the CMOS wafer 1238 of the calibrating optical device among Figure 37 can be described more all sidedly with reference to Figure 38.Figure 38 shows the subsystem 2010 that comprises optics and electronic device in the mode of sectional view.Subsystem 2010 comprises CMOS wafer 2012, at CMOS wafer 2012 upper support detector arrays.Detector array 2014 comprises a plurality of detector pixel 2016 that distribute by CMOS wafer 2012.Subsystem 2010 further comprises lenslet array 2018, and the light that is used to strengthen detector array is caught.In addition, subsystem 2010 comprises the light means for correcting, and it is prevailingly by label 2020 expressions.Light means for correcting 2020 is another embodiment of the correcting element wafer 1236 of Figure 37.In embodiment shown in Figure 38, light means for correcting 2020 comprises transparent substrates 2022, and correcting element 2024 invests on the transparent substrates 2022.Correcting element 2024 can be the combination (including, but not limited to diffraction grating, refracting element, holographic element, Fresnel lens and other diffraction elements) of an optical element or a plurality of optical elements.Light means for correcting 2020 is configured to can be at the incidence angle θ of broad _InReceive incident light (by arrow 2030 expressions) and incident light in the scope and can also arrive one of a plurality of detector pixel 2016.That is to say, no matter incidence angle θ _InSize how, when light means for correcting 2020 exists, have when not having light means for correcting 2020 and more many incident light 2030 and reach detector pixel 2014.In fact, if the arrow of expression incident light 2030 is counted as the chief ray of incident light 2030, light means for correcting 2020 will fully be proofreaied and correct nonideal chief ray incidence angle so, even thereby make that incident light also can arrive one of a plurality of detectors away from the position incident of normal incidence the time.Like this, subsystem 2010 can receive the input light in sizable incidence angle circular cone, and still can play a role effectively.In embodiment shown in Figure 38, correcting element 2024 should be oriented to enough near apart from lenslet array 2018, so that chromatic dispersion and pixel interference minimize.

In order to compare, Figure 39 shows the detector array subsystem of prior art, wherein in this subsystem the light means for correcting is not set.Figure 39 shows the sectional view of the part of detector array system 2035.With shown in Figure 38, incident beam 2030 (comprising chief ray 2032) is with incidence angle θ _InIncide on the part of lenslet array 2018.In detector array system 2035, be not provided with under the situation of any light means for correcting, lenslet array 2018 focuses on point between the detector 2016 with incident beam 2030, do not lost so that incident light drops on the detector and therefore, and then reduced the brightness of sensing.Be used to strengthen the bigger method that is detected light of entrance ray angle and comprise, the photocentre of lenslet 2018 is moved with respect to pixel 2016.Though the photocentre of mobile lenslet can improve performance to a certain extent, to the improvement of uncertain performance, the vignetting (vignetting) that is caused owing to the 3D character of common dot structure is restricted.Therefore, as shown in figure 38, comprise the subsystem 2010 of light means for correcting 2020, compare, provide significant improvement at aspect of performance with the system that does not comprise the light means for correcting of prior art.

Forward Figure 40 and 41 and now to, the details of the effect of correcting element in the detector array system is described in conjunction with Figure 38.At first with reference to Figure 40, subsystem 2037 comprises correcting element 2024, and incident light arrived correcting element 2024 before arriving lenslet array.Correcting element 2024 is with incidence angle θ _InReceive irradiating light beam 2030.Correcting element 2024 is configured for the incident of proofreading and correct non-normal, so that make incident beam 2030 after passing through correcting element 2024, arrive lenslet array 2018 with approximation method line angle (near-normal angle), thereby make incident beam focus on one of detector.

Figure 41 shows the similar configuration that comprises correcting element, and still different with Figure 40 is that correcting element is placed on the path of the incident beam propagation after the lenslet array.Such as shown in figure 39, the lenslet array among Figure 41 at first makes incident beam 2030 focus on point between the detector pixel 2016.Yet the correcting element 2024 among Figure 41 is used to proofread and correct the direction of propagation of the light beam of last acquisition, thereby light beam is dropped on one of detector 2016, and then makes the brightness maximization of being surveyed.

Forward Figure 42 and 43 to, wherein show decoration (embellishment) according to light means for correcting of the present invention.Figure 42 shows detector system 2100, and detector system 2100 comprises light means for correcting 2120, and light means for correcting 2120 comprises a plurality of correcting elements and transparent substrates.In embodiment shown in Figure 42, light means for correcting 2120 comprises a plurality of correcting elements 2122,2124,2126,2128 and 2130.These correcting elements can be supported (for example transparent substrates 2022 supports correcting element 2124 and 2122, and transparent substrates 2132 supports correcting element 2128 and 2130) or independent be provided with (for example correcting element 2124 and 2126) by a plurality of transparent substrates.Compare with single correcting element, piling up of a plurality of correcting elements provides better light calibration result, thereby can realize for example on a large scale key light line angle, the more wavelength of wide region or more compensation of higher diffraction efficiency.Detector 2016 for example can comprise monochromatic detector and multicolour detector.

The detector system 2100 that Figure 43 shows with Figure 42 similarly disposes, but also comprises color filter array in this configuration.The detector system 2200 of Figure 43 comprises detector array 2014, lenslet array 2018, light means for correcting 2220 and is used for the color filter array 2250 of separate colors that wherein light means for correcting 2220 comprises a plurality of correcting elements and a plurality of transparent substrates of stack arrangement.The light correction that a plurality of correcting elements in the light means for correcting 2220 can be configured to the light means for correcting is realized is suitable for the multi-wavelength corresponding with the color in the colour filter.For example, light means for correcting 2220 can be configured to be inducted into especially the detector/colour filter combination of green component by being configured to survey green glow in the irradiating light beam.

Figure 44-46 shows three embodiment of the element form that is suitable for use as the correcting element in the light means for correcting of the present invention.Figure 44 shows and is used to proofread and correct as the function of radial dimension and the refracting element 2302 of the key light line angle that changes.An embodiment of this refracting element is an adjuster.Figure 45 shows the Fresnel lens 2304 that has or do not have luminous power, and Fresnel lens 2304 has the effect identical with refracting element 2302, but Fresnel lens 2304 is along generally can be thinner than refracting element on the optical axis direction.Fresnel lens shown in the figure 2304 comprises mentioned ridge-shaped surface 2306, and mentioned ridge-shaped surface 2306 has the chief ray corrective action.Figure 46 shows diffraction element 2310, and diffraction element 2310 comprises surface 2312, the 2312 grating cycles with spatial variations of surface.Diffraction element 2310 for example can be configured to proofread and correct any variation of key light line angle.Shown in Figure 42 and 43, can be with multiple correcting element combination to realize bigger design flexibility.

Forward Figure 47 to, Figure 47 shows the vertical view of detector system 2400, and wherein detector system 2400 comprises the array of the correcting element 2420 that is positioned on the CMOS wafer 2012.For example, as shown in the figure, in Figure 38, CMOS wafer 2012 comprises a plurality of detector pixel 2016.Notice that the shape of detector pixel is not simple square or rectangle.Generally speaking, the shape of pixel can be very complicated.The array of correcting element 2420 is arranged on a plurality of detectors, so that the light that incides above it is proofreaied and correct.The shape of each in the correcting element 2420 and format surface can be suitable for the size and dimension of incident beam and the shape of detector pixel.

Figure 48 and 49 has illustrated the mechanism that light is proofreaied and correct by exemplary correcting element.As shown in figure 48, correcting element 2502 is the diffraction elements that are used to receive light 2504.Light 2504 is with incidence angle θ ₁Incide the upper surface 2506 of correcting element 2502.When light 2504 left the mentioned ridge-shaped lower surface 2508 of correcting element 2502, light 2504 was with angle of emergence θ ₂Penetrate, wherein angle of emergence θ ₂Less than incidence angle θ ₁This correcting element will be suitable for using in light corrective system of the present invention.

In the variant of correcting element 2502, the correcting element 2512 of Figure 49 comprises the upper surface 2514 that deposits reflection inhibition coating 2516.Reflection suppresses coating 2516 and allows from the optical coupling away from the big pyramid of normal, thereby makes incidence angle θ _InAccording to concrete coated designs can for less than 90 the degree arbitrarily angled.Correcting element 2512 further comprises lower surface 2518, and lower surface 2518 comprises a plurality of reflectings surface that replace 2520 and transition face 2522.Reflecting surface is designed to have curved surface, so that the light that light 2504 is expected proofreaies and correct, thereby makes it with suitable angle of emergence θ _OutOutgoing.Transition face tilts, so that minimum light is by the transition face scattering; For example, transition face can be designed near the particular point place on the correcting element is positioned at the chief ray incidence angle.The direction of the surface of emission and transition face can be suitable for the light source of given type, for example comprises the light source of importing optics, and wherein this input optics provides input ray pencil but not the light beam of calibration.The optic shape of the surface of emission also can be suitable for the specific imaging optics that adopted.

Being on the other hand of the correcting element of the correcting element 2512 of Figure 49 for example, to the chief ray and the ambient light of specific imaging len system, and the position of transducer is controlled.For example, with the example of Figure 50 as this problem.In system shown in Figure 50 2600, correcting element 2024 plays the effect of control chief ray 2032, so that after chief ray is by lenslet 2018 and colour filter 2250, chief ray 2032 is collected by the pixel on the wafer 2,012 2016.For convenience of explanation, Figure 50 shows the chief ray perpendicular to correcting element 2024.Generally speaking, chief ray and other light can arbitrarily angledly incide on the correcting element 2024.As can be seen, light 2632 on angle away from chief ray 2032.It is the light at center with chief ray 2032 that light 2632 can be regarded as the rim ray or the loosely that come from common awl.For the fast imaging system, rim ray will depart from chief ray than wide-angle.For wavefront coded imaging system, can there be uneven and average bigger departing between rim ray and the chief ray.If correcting element 2024 only is designed to control chief ray 2032, transducer 2016 is probably surveyed less than rim ray 2632 so.Can avoid this situation by 2024 of the correcting elements that the knowledge of utilizing imaging system suitably designs between object and the transducer.

Figure 51 and 52 illustrated special-purpose adjuster, be two kinds of expressions of improvement version of the adjuster 2512 of Figure 50, wherein the improvement version of adjuster 2512 is used to utilize the knowledge of lens combination that chief ray and ambient light are proofreaied and correct.Opposite with Figure 50, in Figure 51, except chief ray 2032, rim ray 2632 is also proofreaied and correct by adjuster 2024, thereby makes the light of four corner pass through lenslet 2018 and colour filter 2250, thereby is collected by the pixel on the wafer 2,012 2016.Adjuster 2024 utilizes the knowledge or the wavefront that lens combination produced that forms image that utilizes of equal value of lens combination, and chief ray 2032 and every other light are proofreaied and correct.

Figure 52 shows the wavefront of the structure of Figure 51 and represents.Wavefront 2652 is sent by the lens combination (not shown), and generally speaking depends on the position of illumination wavefront and image.Compare with wavefront 2652, after the adjuster 2024 of Figure 51, wavefront 2654 is flat substantially.2654 needs of wavefront are enough flat, drop within the detector pixel 2016 so that throw light on after by lenslet and colour filter.Bigger detector pixel 2016 or more coarse lenslet 2018 need more not flat wavefront 2654.After lenslet 2018, produce wavefront 2656, and wavefront 2656 is assembled towards pixel 2016 roughly.

Figure 53 shows the more generally situation of the Figure 51 that comprises lens combination 2100 by the description to wavefront.In system 2700, collect by lens combination 2710 from the illuminating ray 2704 of object 2702.Lens combination 2710 comprises a plurality of optics 2714.This lens combination forms chief ray 2032 and other light 2732, and for the position of special illuminating color, image and/or object 2702, chief ray 2032 and other light 2732 with every other light by wavefront 2752 expressions.Adjuster shown in adjuster 2554 image patterns 51 is the same, plays the effect of removing a large amount of local wavefront perks and producing substantially the more flat wavefront of assembling towards special detector pixel 2,016 2756.Then, collect by the pixel on the wafer 2,012 2016 from the light of lens combination 2710.It is this knowledge of function of illuminating color and locus that adjuster utilizes wavefront 2752, with the more flat wavefront 2556 of crooked also generation of basic elimination wavefront 2752, arrives the zone of detector pixel with the light that allows maximum.Do not need to form the image of focusing; Importantly light arrives the detector pixel in any zone of action.For example can by but be not limited to the stereomutation of complementary surface shape (complementarysurface shape), adjuster and the elimination that hologram is realized wavefront.

Figure 54 shows the another kind of the system of Figure 51 is revised, and is that lenslet is incorporated in the adjuster 2024 specifically.In system 2800, adjuster 2810 plays the effect of basic elimination from wavefront and the chief ray 2030 and the rim ray 2632 of lens combination (not shown), so that after colour filter 2250, the pixel 2016 on the wafer 2012 can detect the light that extensively changed before correcting element 2810.Adjuster 2810 is shown in the curved surface that one or more pixels top has repetition in the drawings.Described curved surface can have need be used for eliminating the curvature of the wavefront that comes from lens combination and the curvature that was provided by lenslet as shown in Figure 51 originally.Like this, adjuster can be an only optical element between lens combination and the wafer 2012.Alternatively, in color imaging system, colour filter 2250 can be integrated on the adjuster 2810 or be integrated in the adjuster 2810.Though adjuster shown in the figure 2810 has reflecting surface, Fresnel face and diffraction surfaces are suitable for use as the body holographic element with also being equal to.

Figure 55-64 has further described for example method of the correcting element of the color imaging system of Figure 43 that is particularly suitable for that is used to form.In miniature camera systems, these correcting elements can use separately, perhaps use with the light correcting element among Figure 44 to 55.The particular importance of the correcting element among Figure 55-64 is characterised in that color separated.The light that color separated is used for making different colours is spatially towards suitable colour filter or location of pixels, improves catching of light greatly thereby compare when not using color separated.

Consider to adopt the color filter array that uses in the present imaging system.Different pixels has different colour filters usually, and a plurality of then colors are used with signal processing, to form final coloured image.Color filter array figure commonly used is called Bayer form (pattern), and is made of redness, green and blue color filter.Figure 60 shows the Bayer form.In the imaging system of prior art, represent the light of all colours of object to incide on all related pixels.If the special pixel of image and colour filter are white consistent with object, white light then can incide on this special pixel and the colour filter so.If the color of this special colour filter for example is red, have only the white light photon of about 1/3 incident can be so by this pixel capture, because colour filter plays the effect of removing blue and green photon.Be configured and be provided with the correcting element separating incident light spatially that is used to provide color separated so that incide on the pixel (red filteredpixel) of filter red mainly be red photon, incide that to filter on the green pixel mainly be that green photon and inciding filters on the blue pixels mainly be blue photons.Except redness, green and blueness, utilize this method can also dispose the color separated of other types, thereby a certain proportion of redness, green and blueness can be separated, and it is guided to some pixel.Therefore, the big incident photon of sharing is hunted down, and improves the low-light level imaging performance greatly to allow high signal strength signal intensity.

Figure 55 and 56 shows the conceptual scheme according to two-stage color separated subsystem of the present invention.In practice, essential sometimes is one-level color separated system rather than two-stage color separated subsystem.The subsystem that has the wafer configuration of duplicating among Figure 55 and 56 is the embodiment of the wafer of the correcting element 1232 among Figure 37.The illumination of inciding on first correcting element (first correcting element 2855) is expressed as 2850.This illumination has redness, green and blue component usually, and wherein the ratio of redness, green and blue component depends on the locus of captive scene, lens combination and transducer.Green component is represented by two component G1 and G2 in Figure 55 and 56.G1 is green red/green, and G2 is green or blue.For convenience of explanation, illumination 2850 shown in the figure is perpendicular to first correcting element 2855.After first correcting element 2855, before second correcting element 2865, R (redness) and G1 luminance component and G2 and B (blueness) component are separated in the illumination 2860, shown in front view.The corresponding end view of Figure 56 is illustrated in to throw light on before second correcting element 2865 and does not have separation in 2860, and this just means that one dimension separates the influence that is subjected to first correcting element 2855.After second correcting element 2865, the color separated that the front view of Figure 55 illustrates illumination 2870 does not change (promptly in front view, second correcting element 2865 does not change the illuminating ray direction).Yet the end view of Figure 56 shows (R/G1) of illumination 2870 and the additional color of (G2/B) component separates.The color separated that the color separated that first correcting element 2855 is caused and second correcting element 2865 are caused differs 90 degree.After first correcting element and second correcting element, incident illumination 2850 is divided into independently color component 2870 of four spaces.First correcting element and second correcting element can be positioned on the apparent surface of substrate, the element among Figure 43 2024 and 2122 for example, and substrate 2022 is between the two.In addition, two correcting elements of generation one dimension separation can be combined into and produce the single correcting element that two-dimensional color is separated.Correcting element for example can be the surface with modification or the substrate of volume optical element.

Figure 57-59 additional description the essence of color separated among Figure 55 and 56.At first, before first correcting element, incident illumination 2850 is that the space is uniform basically.The light beam of illumination 2850 is described to the match (fitting) in the circular contour, shown in Figure 57.After first correcting element 2855, before second correcting element 2865, illumination 2860 is divided into two zones 2862 and 2864, shown in Figure 58.(R/G1) luminance component (zone 2862) is an apart with (G2/B) luminance component (zone 2864).The light beam of these luminance component shown in the figure is level and smooth with overlapping.Even the density of luminance component increases for the sub-fraction of luminance component, so also can realize being better than the benefit of prior art.At first and second correcting elements (2855 and 2865) afterwards, illumination 2870 is spatially further separated, shown in Figure 59.In the area of space that separates on four spaces (2872,2874,2876 and 2878), R, G2, G1 and B component have higher density.It is nonoverlapping just these zones being shown for clarity and in the drawings, but in the device of reality, these zones are overlapping slightly also to be possible.That is to say that in neighborhood pixels, any a high proportion of color is all corresponding to improved color separated.If the color separated zone is corresponding to independent detector pixel, the detector pixel among Figure 42 2016 for example, each pixel in 2 * 2 pixel regions all will be sampled to the photon of special lighting spectrum so.If separated color and single detector pixel color filter coupling, detector will be caught the exposure of increase so.

For example, the pixel of supposing the limit, 2 * 2 regional 2880 northwest among Figure 60 has red color filter.So, if in Figure 61 illumination 2880 separated color be red in this position, the photon part that will be caught when not adopting color separated in throwing light on of this special pixel incident photon part of catching so.So just directly improved catching and the low-light level imaging performance of light.If the space configuration sufficiently clear of separated color, just so no longer need the color filter array 2250 of Figure 43.Only adopt the color separated of calibrating optical device to can be used to make the space illumination spectrum to be shaped in any desired way.Separated color can be any desired blend color, and is not only color R, G1, G2 and B.For example, these three kinds of colors of magneta colour, yellow and cyan can be separated, and can produce the new color samples of image when not using with R, G and B colour filter.

Can be used for utilizing correcting element to realize that the method for color separated has a lot.Figure 62 shows a kind of method of utilizing wavelength to make the lighting space chromatic dispersion, and this method adopts dispersing prism.Utilized the chromatic dispersion of optical material (be refractive index as the function of illumination wavelengths and change) in order spatially to make color separated, prism.The unessential character of given miniature camera for some system, only uses dispersing prism that actual solution can not be provided.

To have with the size of the correcting element of the similar feature of dispersing prism and reduce its cost in order to dwindle, can shown in Figure 63 and 64, adopt color separated diffraction type structure like that.Figure 63 and 64 has illustrated the method for utilizing wavelength to make the compactness of lighting space chromatic dispersion.As everyone knows, diffraction structure for example is used to generally adopt that the instrument of spectrometer makes the luminance component apart.Even the simple two-stage binary diffraction structure shown in Figure 63 also can make luminance component with respect to its color generation diffraction.The angle deviating of color component directly depends on wavelength.More complicated diffraction structure can come more effectively separate colors component with the amount of the light of the direction do not expected or order diffraction by control.Figure 64 shows and shows off diffraction structure.These diffraction structures can be for more than the two-stage, and has as the function of locus and the structure height that changes.The structure that precision improves may more be separated with the spatial color shown in Figure 59 near Figure 55.

Figure 65-70 has described and has adopted wavefront coded so that the SNR of image equates or the emergent pupil as the equal imaging system of the detection probability of object distance function is disposed.Many systems based on task are used to obtain the information of the special use that comes from distant objects.In general these imaging systems based on task can not form image desirable for human eye.One based on the system of task is exemplified as the biologicall test imaging system, is specially iris authentication system.Another is exemplified as image tracking system.In both cases, distant objects is all luminous or reflect a certain amount of light.Imaging system in these exemplary systems is configured to obtain for example iris-encoding or object (x, y) information of the special use of position respectively having noise, adopting under the situation of coarse optics and mechanical structure.In the ideal case, can on the volume of big object, adopt high accuracy and obtain above-mentioned information fully fifty-fifty.In some cases, may wish to specify in the precision or the accuracy of the information of obtaining in the object volume.For example, according to object residing position in volume, can think that information is more important.The full accuracy of information is estimated to be designed to corresponding with the critical positions in the object volume.This point also is useful in general imager, such as, for example more important than 1.5 meters picture qualities to 10cm from the picture quality of infinity to 1.5 meter.

When in bigger object volume, making general scene imaging, for human viewer, if object volume is enough big, be constant in object volume thereby make the feature of optics, imaging system or wavefront coded system are configured are commonly referred to be acceptable so.Modulation transfer function or point spread function for example are configured to basically form identical value usually in wide object volume.

An one dimension cube phase imaging system adds that perfect lens can illustrate this notion.For this system, for certain constant alpha, the phase outline that increases to lens or emergent pupil is p (y)=α y ^Λ3.Parameter y represents along the locus of desirable one dimension lens.We can think that the phase outline of scioptics diaphragm is along with the variation of the focal length of continuous variable is variation at perfect lens.Because the focal length of lens can be approximately the second dervative of lens phase place, therefore the change whole cube of phase system mid-focal length can be described as:

Focal_length(y)～d ^Λ2p(y)/d ^Λ2＝6*α*x＝β*x

Perhaps, the variation of the focal length of lens is linear.We can regard simple cube of phase system as the unlimited gathering of the focal length of the lenslet that increases to perfect lens, and the focal length of lenslet changes the focal length that passes diaphragm linearly.The linear change of focal length causes MTF to be approximately constant in the object distance scope of certain broad.Using ambiguity function to allow these systems are carried out simple analysis, is constant to show MTF in the object distance scope of broad or in the de-focus region that equates substantially.

Consideration is in the detection system of special use, in the effect of the special constant MTF of spatial frequency place.As the Shannon instruction, image information is relevant with signal to noise ratio (snr) after all.Increase the information that SNR can increase the maximum that can be extracted out.Suppose that for image detecting system the response at given spatial frequency place is the MTF of imaging system of (being amplified by imaging system) this spatial frequency and the product of object spectra.Noise reads noise, still image noise with detector, depend on that the noisiness of the noise (comprising shot noise) of signal and other types is relevant.Along with the distance of diaphragm to object increases, the photon that the entrance pupil of imaging system is caught reduces.Along with the distance of diaphragm to object reduces, the photon that entrance pupil is caught increases the photon that pupil catches and increases.In ideal system, captive total number of light photons can be followed square distance inverse ratio rule.If the object response is along with radical change takes place distance, suppose that so present multiplication factor is constant, and for the distance or the enough I of distant objects to regard the point-like thing as, the time of the signal regulation optic response that is sampled so, thereby SNR will change along with constant optic response for given spatial frequency.Even adopt constant MTF, whole object SNR and image information also will be the functions of object distance.When image (with such in the most systems) when the imaging multiplication factor changes along with distance, the change of multiplication factor further makes the SNR at a spatial frequency place in the de-focus region change.

For many systems, image information is as the function of object distance, should be constant or is subjected to special control.We can obtain this feature by changing as the basic response of the MTF of object space or the function that defocuses.Because the total amount of mtf value square is constant all defocus in, therefore, can cut apart with the constant or concrete SNR system of formation the MTF response as distance function by keeping the fuzzy behaviour of optics.Figure 65 shows for two of two different wavefront coded systems exemplary focal length-pupil location curves.The focal length curve representation design of index variation is used for realizing the new system of constant SNR in the object distance scope.In the diaphragm scope, the form that focal length is index variation is focal_length (y)={ α [b* (y) ^Λ2+c*y+d] }.In this special embodiment, b=c=12, d=-4.

Figure 66 and 67 shows ambiguity function (AF) expression that is used for focal length and is linear change or cube phase system.Figure 66 shows and is used for the AF that focal length is the system of one-dimensional linear variation.The MTF that represents the function that conduct defocuses by the radial component of AF initial point.Defocus between the angle of aberration coefficients and radial transmission line and have linear relationship.Represent poly-accurate (in-focus) (scattered Jiao) MTF of focus by the lateral part of AF initial point.Represent the value of the MTF of the function that conduct defocuses by the vertical component of AF at certain spatial frequency place.

Consideration is 0.175 o'clock vertical component by AF in normalization spatial frequency (or U axle value).It is the MTF that conduct in 0.175 o'clock defocuses function that this part is illustrated in the normalization spatial frequency.Figure 67 shows the vertical component by AF.Be approximately+/-0.2 normalization out-focus region in, at the MTF at this spatial frequency place approximately constant.Alternatively, the system of focal length linear change makes that MTF is substantially invariable in the de-focus region of expansion.It should be noted that in Figure 67, the conduct of a spatial frequency is defocused the response of function, is substantially invariable in specified scope.

Figure 68 and 69 shows and is used for the AF that focal length is (photon compensation) system of index variation.Figure 65 shows the system that focal length is index variation.As can be seen, the shown AF of the image among Figure 68 is different from the AF shown in Figure 66 slightly.Phase function has p (y)=α * (y ^Λ4+2y ^Λ3-2y ^Λ2) form.Figure 69 shows the part by AF at normalization spatial frequency 0.175 place.When drawing with logarithmic scale, the MTF response that this conduct defocuses function is approximately linear function.When drawing, be approximately exponential function as the MTF response that defocuses function with linear graduation.In Figure 69, as can be seen, when representing with logarithmic scale, the response that the conduct of a spatial frequency is defocused function is (perhaps being meant the number form formula when representing with linear graduation) of substantially linear in the scope of appointment.

Figure 70 and 71 shows the AF of the imaging system that is used for not having wavefront coded desirable traditional imaging system or diffraction limited.As can be seen, compare with the AF of Figure 66 and 68 wavefront coded system, the AF shown in Figure 70 very closely aims at transverse axis.This feature of AF among Figure 70 means that the MTF with wavefront coded system changes greatly along with the change that defocuses.Figure 71 shows the part by AF at 0.175 normalization spatial frequency place.As can be seen, this MTF is very narrow, has bigger mtf value at scattered Jiao Chu, and at the normalization values of defocus place that is different from scattered Jiao slightly, has less mtf value.SNR with imaging system of this MTF is maximized at scattered Jiao Chu, and is minimized everywhere at other.Should be noted that, the conduct of a spatial frequency is defocused the response of function, scattered bigger when burnt, then very little everywhere at other.

Owing to kept fuzzy,, be constant along the quadratic sum of the AF value of any particular vertical line therefore for any phase place of the emergent pupil that is applied to the ideal image system.Perhaps, for all values of defocus, the quadratic sum of the mtf value at a spatial frequency place is a constant.Therefore mtf value is invariable.Though be the system of linear change for focal length, in+/-0.2 de-focus region, and defocus relative mtf value and be about 0.05, be the system of index variation for focal length, mtf value changes to more than 0.1 from 0.03.Owing to kept fuzzy behaviour, therefore mtf value increases for some values of defocus, also just means that other values of defocus mtf value reduces for some.

But the product of the response of object response relative with distance and the optical system of Figure 69 can be the system matches of index variation with focal length, is constant to guarantee SNR, thereby guarantees that the image information as the object distance function is constant.Be the system of linear change for focal length, SNR and image information will be as the functions of object distance and are changed.For not having wavefront coded system, SNR will be maximized at the pinpointed focus place, and will be minimized in every other position.If requiring the mtf value of specific proportions is the function of object distance, the structure with the similar shown in Figure 66-69 can be used to approach the focal length variations function so, and then the last pupil function that obtains of structure.In addition, need realize further improvement by optimizing, so that the pupil function of last acquisition is finely tuned.Then, can customize as the function that defocuses or of equal valuely as the MTF of the function of object scope, to satisfy the needs of special applications.Figure 72 is used to illustrate the flow chart that is applied to the method 3500 of optical system with wavefront coded.Method 3500 has illustrated the design that is used to realize having wavefront coded special grin lens, has been similar to the step of the effect of focusing with control.The describe, in general terms of this process is as follows.

Step 3510 is selected the optical arrangement of beginning.Described optical arrangement comprises type and the form in order to each element of handling the light from object to photon sensing element or detector array.Described optical arrangement comprises a plurality of optical modules and the type of assembly, for example refractor, light adjuster, speculum (mirror), diffraction element, the volume hologram device etc. in the system (for example three systems that lens constitute).In addition, determine employed special material, for example glass, plastics, specific glass or plastics, GRIN material etc.

Step 3520 selective system parameter, wherein system parameters is that can change or unfixed in advance.These parameters will become the part of optimization process (the optimization circulation 3540 for example).System parameters can comprise the set of spendable optical material or mechanical material, physical size and the shape and the relevant distance of assembly.During optimizing, for example the general characteristic of weight, cost and performance also can be used as parameter and handles.The signal processing that is used to form final image also has parameter, for example needs to be used for producing the dynamic range, Nonlinear noise reduction parameter of silicon area, linear core (kernel) value, the filter kernel (filter kernel) of final image etc. in ASIC implements.Comprise the composition and the type of the aspheric surface optical control (aspheric optical manipulations) that will be applied to imaging system with wavefront coded relevant important parameter.These parameters can be unusual simple parameters (for example, the apparent height on the separable surface of rectangle), perhaps can be unusual complicated parameter, for example define the parameter of the three-dimensional refractive index of volume imagery element.Grin lens is an embodiment of volume imagery element.The volume hologram device is another embodiment of volume imagery element.

Initial optical design procedure 3530 comprises the traditional optical designs, and as putting into practice in many textbooks, design process involves the aberration balancing of the aberration relevant with non-focus (non-focus) especially.(for example when ready-made optical module provides initial supposition for optical design) can delete optical design step 3530 in some cases.The aberration relevant with focus comprises following several aberration: for example ball-shaped aberration, the curvature of field, astigmatism, aberration, the aberration relevant with temperature and with processing with aim at relevant aberration.The aberration relevant with non-focus comprises following aberration: for example coma, lateral chromatic aberration and can not be by the moving or distortion (if can realize this distortion in some way) and the distortion of proofreading and correct secretly of image planes, wherein image planes be functions of the variable of the angle of visual field, color, temperature and aligning for example.The influence of the aberration that the concentrated signal processing of removing special-purpose optical device designs of utilization and final image of optical design step 3530 is not easy to remove.Optical design step 3530 comprises to be provided and the relevant initial guess of parameter of optical system set.

Utilize the initial optical design, can begin the combined optimization of optical module and digital assembly.Optimize the optical design parameter that circulation 3540 is modified in appointment in the step 3520, till satisfying some last design standard.Optimize circulation and comprise step 3550,3560,3570,3580 and 3590, will discuss to these steps below.

In modify steps 3550, the initial guess of parameter is applied to initial optical design from step 3530, thereby forms the optical system of revising.

Step 3560 is determined signal processing parameter, and these signal processing parameters will act on formed image to produce final image.Signal processing parameter for example can comprise the size and the form of two-dimensional linear filtering core.Signal processing parameter can be based on the optical system of modification special in the step 3550 and choose.

In step 3560, determined after the signal processing parameter, in step 3570, corresponding signal process has been applied to analog image from the optical system of revising.Analog image can comprise for example target image of the special use of point, line, grid, bar etc., and/or can be the color images of general scene.Analog image can comprise the noise from reality or ideal detector, for example shot noise, still image noise, read noise etc.

Step 3580 pair comes from the optical imagery and the signal processing of the simulation of step 3570 to be estimated, to determine whether to satisfy the overall system standard.Described standard can comprise imaging performance, for example picture quality is specifically defined, wherein picture quality is the function of a position, color, objective scene, intensity level etc., and described standard for example can also comprise size, optics, electronic device and system cost, machining tolerance, assembling and the temperature of system dimension, optical element.Can calculate specification according to analog image, can calculate specification value in number, be higher than desired value or be lower than desired value to judge them.Specification and desired value can convert the discernible numerical value of computer in order to the picture quality that people are seen to.Application program (for example iris recognition) based on task can have the specific specification numbers of application, and this specification numbers can not need to convert the parameter of picture quality to numerical value.If step 3580 is determined the imaging system of revising and satisfies standard that design process finishes so.If the imaging system that step 3580 determine to be revised does not satisfy standard, so in the further optimization of step 3590 execution parameter.During optimizing,, need to change parameter of optical system for system is guided towards the special system that satisfies system specifications.During optimizing, the method that changes system parameters is to adopt the general problem of multiple solution.Change or the typical method of parameters optimization can comprise optimal speed and find global maximum or minimizing ability between balance.As the nonlinear method of for example Nelder-Mead or genetic search (Genetic Search), for example the linear search technique of gradient decline (Gradient Descent) also is useful.The selection of optimization method can be the function of the complexity of the special imaging system that designing.

After step 3590 has changed system parameters, repeat and optimize circulation 3540: utilize new parameter to revise optical system in step 3550 then, determine the parameter of signal processing, before step 3570 is carried out signal processing and form image or the like afterwards in step 3560.At last, by determining to satisfy standard in step 3580 or, optimizing circulation 3540 and finish owing to do not find suitable solution but not convergence.

The embodiment of method 3500 is the designs to the grin lens 134 of the modification of Figure 11.Described method starts from selecting ready-made grin lens.Choose NSGILH-0.25 grin lens and gray scale detector in step 3510 with 3.3 μ m side pixels.Select desirable pixel and simple linear signal to handle in step 3520, but non-selected light detectors.Equally in step 3520, carry out aspheric surface at the front surface of grin lens and revise, that is to say, select modification, so that it has the separable cubic surface form of rectangle to the front surface 135 of the grin lens 134 of Figure 11.The separable cubic surface form of rectangle is defined as: and height (x, y)=α (x. ^Λ3+y ^Λ3).Only determine an optical parametric α at this embodiment, it is corresponding to maximum surface deviation.

Owing to only designed modification, therefore omitted step 3530 in this embodiment to ready-made grin lens.As a comparison, do not have grin lens that revise, Custom Design (custom-designed), so then need execution in step 3530 if target is a front surface.

The first special value of cubic surface straggling parameter α is chosen for α=0 arbitrarily.In step 3550, the emulation tool by means of customization utilizes parameter alpha that lens are carried out separable cube of phase modification of rectangle.

At step 3560 signal calculated processing parameter, be applied to the grin lens of described special modification in step 3570, thereby make the image of formation have big mtf value and compact PSF.Owing to adopt linear filtering, be used for therefore determining that the algorithm of linear filter is:

Final_PSF=Sampled_PSF*Linear_Filter is on least squares sense, and wherein symbol * represents the two-dimensional linear convolution.Determine PSF (Sampled_PSF) value of sampling according to grin lens emulation of revising and digital detector in step 3560.In step 3560, select Final_PSF as the PSF that conventional optical systems generated, in conventional optical systems, most of power concentration are on a pixel.Value (at the high spatial frequency place of detector) corresponding to the MTF of this special Final_PSF is about 0.4.The technical staff in signal processing field is understandable that, can adopt several different methods to solve the linear equation of these least squares, so that determine linear filter based on PSF collection that adopts and PSF last or expectation.Certainly, can be in frequency domain and/or repeatedly carry out described algorithm.

Along with calculating digital filter, PSF and MTF after step 3570 produces signal processing.Then, in step 3580 these PSF after the signal processing and MTF and visual image quality specification are compared, and described specification is converted into most of PSF power on the pixel that concentrates in whole image fields and the corresponding M TF that has 0.3 above minimum value after signal processing.In first time of optimizing circulation 3540 in the repetitive process, when α=0, PSF and MTF after the signal processing are discontented with the pedal system standard.Optimize at step 3590 beginning Nelder-Mead then,, thereby improve optical system with definite optical parametric α and linear filter.Figure 18 shows the final solution of the optical parametric of optimization.The peak is about 11 wavelength (perhaps being approximately 11 λ at the interior α of optical path difference distance) to the optical path difference of paddy.The corresponding linear filter that signal calculated is handled is so that convert the PFS of sampling among Figure 19,20 and 21 among Figure 22,23 and 24 PSF.Visually as can be seen, compare the most power that the PSF among Figure 22,23 and 24 has with Figure 19,20 with PFS in 21 in a pixel.As can be seen, among Figure 25 the corresponding M TF after the signal processing greater than 0.3.The maximum spatial frequency of detector is 151lp/mm.In Figure 26 and 27, can see the true form of linear filter.This special linear filter can regard as with Figure 19,20 and 21 in the inverse filter of PSF substantially invariable, sampling similar.

Can under the situation that does not depart from its scope, change said method and system.Should be noted that comprise in the top description or accompanying drawing shown in content should be interpreted as schematic but not determinate.Below claim wish to cover all general featuress described herein and special characteristic and method and system of the present invention all scope is described, on language, all that we can say method and system of the present invention are described scope and are fallen within the scope of the claims.

The various assemblies that though each in the above-mentioned embodiment have been described and had special direction separately, but should be understood that, system described in the present disclosure can take various concrete configurations, and various elements can be located on multiple position and the mutual direction, and described system still remains in the spirit and scope of present disclosure.

In addition, can adopt suitable equivalent to replace various assemblies or replenish, and to keep the function of this replacement assemblies or add-on assemble and use be that those skilled in the art are familiar with, so it is counted as within the scope that drops on present disclosure as it.For example, each in the previous embodiments has been discussed though be primarily aimed at chief ray correction situation, can be with one or more correcting element combinations, so that the width of light beam difference that causes for the variation by beam angle provides illumination to proofread and correct.For example, there is the plane of refraction at angle will be suitable for this application, and can for example further makes up so that proofread and correct the key light line angle simultaneously with diffraction pattern.

Therefore, it is schematic but not determinate that present embodiment should be regarded as, and present disclosure be not limited to this paper given details, and can make amendment to present disclosure within the scope of the appended claims.

Claims (15)

1. low height imaging system comprises:

Detector array; And

Grin lens, it comprises having wavefront coded surface, and is configured to make a plurality of detectors of the steeper field light transmission of incidence angle in the described detector array.

2. low height imaging system comprises:

A plurality of optical channels; And

Detector array;

In the wherein said optical channel each: (a) related with at least one detector in the described detector array, and (b) have an aspheric grin lens.

3 low height imaging systems as claimed in claim 2, the aspheric surface of wherein said aspheric grin lens is modified by wavefront coded.

4. low height imaging system as claimed in claim 3, the modulation transfer function of each in the wherein said optical channel does not have zero point in the passband of described detector.

5. low height imaging system as claimed in claim 2 further comprises signal processing, so that based on the phase effect that is caused by the aspheric grin lens in each described a plurality of optical channel, provide final image.

6. one kind is used to form the method with wavefront coded lens, comprising:

Positioning lens in mould;

On the surface of described lens, add curing materials, to form the wavefront coded aspheric surface of having of described lens.

7. low height imaging system comprises:

The light transmitting material piece has input aperture, outgoing aperture and at least one interior reflective surface, and wherein transmission is reflected by described reflecting surface by the wavefront of described input aperture, and leaves the described wavefront coded outgoing aperture that has.

8. low height imaging system as claimed in claim 7, the surface of wherein said light transmitting material piece is formed with wavefront coded, and comprises one of described input aperture and described outgoing aperture.

9. low height imaging system as claimed in claim 7, wherein said reflecting surface are aspheric surface, and be described wavefront coded to obtain.

10. low height imaging system as claimed in claim 7, wherein said outgoing aperture comprises the flat part of described light transmitting material piece, lists in order to be installed to focal plane array.

11. a low height imaging system comprises:

A plurality of optical channels and detector array, in described a plurality of optical channel each is all related with at least one detector in the described detector array and have an aspheric terms light adjuster, and wherein said aspheric terms light adjuster preferentially makes color point to special detector in the described detector array.

12. a photon compensation optical system comprises:

At least one optical element and aspheric surface, the scope of non-constant MTF between object and described optical element of wherein said system compensates.

13. photon compensation optical system as claimed in claim 12, wherein said aspheric surface comprises the surface of described optical element.

14. photon compensation optical system as claimed in claim 12, wherein said aspheric surface pass its aperture and have non-linear focal length variations.

15. photon compensation optical system as claimed in claim 12, wherein said aspheric surface pass its emergent pupil and have non-linear focal length variations.

16. photon compensation optical system as claimed in claim 12, wherein compensation is included in and makes the Energy distribution normalization of passing the focal plane in the described scope.

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