CN203275770U - Phase masking plate capable of being detached and recombined and wavefront coding imaging system - Google Patents

Abstract

The utility model relates to a kind of detachable recombination phase mask plate and the wavefront coded imaging systems based on the phase mask plate, the corresponding phase mask function of detachable recombination phase mask plate is formed by stacking by two cosine functions with relative shift, one-dimensional function expression are as follows:

Wherein; α, m1 and m2 are the parameters of phase distribution function; X is normalized coordinate; The value range of x is [- 1,1]; The value range of offset m1 and m2 are [- 1,1]. The utility model provides a kind of detachable recombination phase mask plate that can effectively expand the system depth of field, and based on the phase mask plate, wavefront coded imaging systems that defocus susceptibility and bandwidth can be adjusted.

Description

Detachable restructuring phase mask plate and wavefront coded imaging systems

Technical field

The utility model belongs to optical field, relates to a kind of phase mask plate and based on the wavefront coded imaging systems of this phase mask plate.

Background technology

The depth of field of expansion optical system always is the focus of academia's research, since 20th century the mid-80, although panoramic method is proposed for depth of field expansion, but until doctor Dowski of Univ Colorado-Boulder USA and Cathey teach after the wavefront coded concept of nineteen ninety-five proposition, depth of field continuation has just had breakthrough truly.

Take the one dimensional optical system as example, its out of focus optical transfer function OTF can obtain by the auto-correlation computation of generalized pupil function, and is as follows:

$H(u,W_{20})=\frac{1}{2}\&CenterDot;\underset{-(1-|u|/2)}{\overset{1-\left|u\right|/2}{\&Integral;}}\exp (j\&CenterDot;(2\mathrm{<figure-callout\; id="20"\; label="k\; W"\; filenames="HDA00003026171300022.png"\; state="\{\{state\}\}">k</figure-callout>}{W}_{}{}_{20}\mathrm{ux}+f(x+u/2)-f(x-u/2)))\mathrm{dx}$

Wherein, u and x are respectively normalized spatial frequency and aperture plane lateral coordinates; W ₂₀It is maximum defocus wave aberration coefficient; K is wave number; F represents phase-plate universal expression formula.

For traditional imaging system, the f item in following formula does not exist, and the expression that therefore can easily obtain out of focus OTF is:

$H(u,W_{20})=\frac{\sin (2\mathrm{<figure-callout\; id="20"\; label="k\; W"\; filenames="HDA00003026171300022.png"\; state="\{\{state\}\}">k</figure-callout>}{W}_{}{}_{20}\&CenterDot;(1-\frac{\left|u\right|}{2}))}{2k{W}_{20}u}u\&NotEqual;0$

Can see, when system did not introduce phase-plate, its OTF was highstrung to out of focus, and zero point can periodically occur in the frequency space, thereby caused irreversible information loss.But cube phase-plate (f (the x)=α x that in a single day doctor E.R.Dowski is invented ³) be incorporated on the entrance pupil face of optical system after, just can obtain a diverse out of focus OTF by the static phase method of approximation, as follows:

$H(u,W_{20})\&ap;\frac{1}{2}\&CenterDot;\sqrt{\frac{\mathrm{\&pi;}}{\left|3\mathrm{\&alpha;u}\right|}}\&CenterDot;\exp (j\&CenterDot;(\frac{\mathrm{\&alpha;}{u}^3}{4}-\frac{k^{2}u{{\mathrm{<figure-callout\; id="2"\; label="W"\; filenames="HDA00003026171300011.png,HDA00003026171300031.png"\; state="\{\{state\}\}">W</figure-callout>}}^2}_{20}}{3\mathrm{\&alpha;}})+j\&CenterDot;\mathrm{sgn}\left(u\right)\&CenterDot;\frac{\mathrm{\&pi;}}{4})u\&NotEqual;0$

Obviously, this moment out of focus OTF mould, namely MTF and out of focus wave aberration coefficient have nothing to do, and that is to say that the cube phase-plate can make the MTF of system insensitive to out of focus; Although the phase bit position of OTF and degree of blur W ₂₀Relevant, but as long as modulation factor α increases, it is to W ₂₀Dependency degree will significantly reduce.Simultaneously of paramount importancely be, after having added phase-plate, MTF is in the decline that just has on amplitude within effective frequency range to a certain degree, and do not have zero point or a nearly zero point, be that system is when out of focus occurring, the information that exceeds the primal system field depth is not lost, and just can effectively be recovered by the digital image restoration algorithm afterwards.Simultaneously, because logical light quantity and the resolution of phase-plate to system can not impact, so wavefront coded be a kind of novel field depth extension imaging technology that is different from very much reduced bore method, central obscuration method or apodization.

In existing document, the physical property of most of wavefront coded imaging systems just can't change after optimal design is completed.Yet, because physics scene to be imaged (such as the target imaging distance is changeable) may be very complicated, so need to wavefront codedly can adapt to such variation, namely suppress the ability of out of focus according to the image-forming range dynamic adjustments of estimating, the just greatly dirigibility of Hoisting System this moment.In addition, existing, for wavefront coded systematic research all concentrate on out of focus constant on, few to system response (as whether adjustable in bandwidth) research and comparison.But, due to most of digital imaging system, comprise wavefront coded system, be all that image detector is limited, so there be, spectral aliasing effect that can be lowered into image quality that cause by owing to sample.In order to suppress this effect, usually need to introduce optical low-pass filter before detector.In case design extraordinary phase-plate, be used for the bandwidth of regulating system, so just can play the effect of optically filtering, thereby reduce aliasing to the impact of picture quality.In addition, frequency can be in harmonious proportion the coding reconstruct also have the potentiality of optical encryption, application value is very big.

The utility model content

In order to solve the above-mentioned technical matters that exists in background technology, the utility model provides a kind of detachable restructuring phase mask plate that can effectively enlarge system's depth of field, and based on this phase mask plate, wavefront coded imaging systems that out of focus susceptibility and bandwidth all can be regulated.

Technical solution of the present utility model is: the utility model provides a kind of detachable restructuring phase mask plate, its special character is: phase mask function corresponding to described detachable restructuring phase mask plate is to be formed by stacking by two cosine functions with relative shift, and its one dimension function expression is:

$Q\left(x\right)=\mathrm{\&alpha;}\&CenterDot;\cos \left(\frac{\mathrm{\&pi;}}{2}(x+m_1)\right)-\mathrm{\&alpha;}\&CenterDot;\cos \left(\frac{\mathrm{\&pi;}}{2}(x+m_2)\right)$

$=2\mathrm{\&alpha;}\&CenterDot;\sin \left(\frac{\mathrm{\&pi;}(m_1-m_2)}{4}\right)\&CenterDot;\sin (\frac{\mathrm{\&pi;}}{2}x+\frac{\mathrm{\&pi;}}{4}({\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HDA00003026171300011.png,HDA00003026171300022.png"\; state="\{\{state\}\}">m</figure-callout>}}_1+m_2))$

Wherein,

α, m1 and m2 are the parameters of PHASE DISTRIBUTION function;

X is the normalization coordinate; The span of x is [1,1];

The span of side-play amount m1 and m2 is [1,1].

A kind of based on the formed wavefront coded imaging systems of phase mask plate as above, its special character is: described wavefront coded imaging systems comprises imaging lens, detachable restructuring phase mask plate, image detector and graphics processing unit; Described imaging lens, phase mask plate and image detector are successively set on same light path; Described image detector is connected with graphics processing unit.

Above-mentioned detachable restructuring phase mask plate comprises the first mask plate and the second mask plate; Described the first mask plate and the second mask plate can carry out independent translation centered by the aperture plane of mask plate.

Independent translation between above-mentioned the first mask plate and the second mask plate comprises that the identical and translational movement of translation direction equates, translation direction is identical and translational movement does not wait, the absolute value of translation direction difference and translational movement does not wait and the absolute value of translation direction difference and translational movement equates.

Independent translation between above-mentioned the first mask plate and the second mask plate is the identical and translational movement of translation direction when equating, described wavefront coded imaging systems is common and does not have the imaging system of phase-modulation; Independent translation between described the first mask plate and the second mask plate is the identical and translational movement of translation direction when not waiting, and described wavefront coded imaging systems is effective imaging bandwidth and the wavefront coded imaging systems that can change the susceptibility of out of focus; Independent translation between described the first mask plate and the second mask plate is the absolute value of translation direction difference and translational movement when not waiting, and described wavefront coded imaging systems is the wavefront coded imaging systems that can change over the wide effect of image-tape; Independent translation between described the first mask plate and the second mask plate is the absolute value of translation direction difference and translational movement when equating, described wavefront coded imaging systems is the wavefront coded imaging systems that can regulate the out of focus susceptibility.

The utility model has the advantages that:

The utility model proposes a kind of novel phase mask plate and the wavefront coded imaging systems that the imaging bandwidth is adjustable and the out of focus susceptibility all can be regulated that carries this phase mask plate, this phase mask plate is comprised of two parts independently, each part is a cosine function, but has certain displacement with respect to the aperture plane center.The combination of different displacement will make system common imaging system, possess the wavefront coded imaging systems of out of focus susceptibility regulating power and possess the out of focus susceptibility and wavefront coded imaging systems that bandwidth is simultaneously adjustable in the middle of change.This imaging system can be carried out the adjustable imaging of quality to the target of different distance position in scene; And by bandwidth is changed, this system can regulate the matching degree of detector and optical system, thereby plays the effect that weakens detector constrained system spectral aliasing effect.Simultaneously, system also can allow according to the difference adjustment of imageable target minutia the high-frequency information by system, when reducing unwanted frequency information and the interference of high frequency noise to image quality, can also play the middle effect of optical encryption.When two parts in above-mentioned phase-plate change with respect to the displacement m1 at aperture plane center and m2 size and direction, the effective bandwidth scope of system and out of focus susceptibility will produce corresponding the variation: when identical and translational movement equates when translation direction, it is a common imaging system that system will change in quality, and does not possess depth of field expansion, the adjusting of out of focus susceptibility and bandwidth control ability; When identical and translational movement did not wait when translation direction, system was a wavefront coded imaging systems.Its out of focus susceptibility and system bandwidth all can realize corresponding the adjustment by the various combination of translational movement.When the absolute value of translation direction difference and translational movement equated, system was a wavefront coded imaging systems, and its out of focus susceptibility can allow to regulate.When the absolute value of translation direction difference and translational movement was unequal, system was a wavefront coded imaging systems, and its out of focus susceptibility and imaging bandwidth all can be regulated.The utility model is compared with traditional wavefront coded system, not only can effectively enlarge system's depth of field, can also play the effect that changes the system imaging bandwidth and regulate the out of focus sensitivity simultaneously, thereby make it possess function more flexibly; The utlity model has the ability that suppresses out of focus, and can play the effect of optically filtering by controlling bandwidth, thereby possess the potentiality that are applied to optical encryption, is a kind of conception of novelty, is also the further excavation to the wavefront coding technology application potential.

Description of drawings

Fig. 1 is the structural representation that has carried the wavefront coded system of detachable restructuring phase-plate provided by the utility model;

Fig. 2-1st adopts Fisher information to weigh the corresponding one group of optimization data table of adjustable wavefront coded system of out of focus susceptibility;

Fig. 2-2nd adopts Fisher information to weigh the imaging system of out of focus susceptibility to the sensitivity schematic diagram of out of focus;

Fig. 3 has provided phase-plate effective bandwidth regulating effect figure corresponding to different translational movements when translation direction is identical with out of focus MTF as criterion;

Fig. 4-1st, through optimization, corresponding to the phase-plate parameter list of different bandwidth;

It is respectively 0.5 times of theoretical effective bandwidth through optimization, maximum effective bandwidth that Fig. 4-2 are one group, 0.7 times and 0.9 times of corresponding out of focus MTF curve family;

Fig. 5-1st, the original image of a certain analog simulation;

Fig. 5-2-1 is the corresponding middle analog imagings of the data of umax=1 in Fig. 4-1;

Fig. 5-2-2 is the corresponding restored images of the data of umax=1 in Fig. 4-1;

Fig. 5-3-1 is middle analog imaging corresponding to typical phase-plate in prior art;

Fig. 5-3-2 is restored image corresponding to typical phase-plate in prior art;

Wherein, the Reference numeral in Fig. 1 is as follows:

The 1-imageable target; The 2-imaging lens; The detachable restructuring phase mask of 3-plate; The 4-image detector; The 5-graphics processing unit; 6-focuses on image clearly.

Embodiment

A kind of detachable restructuring phase mask plate for dexterous type wavefront coded imaging systems that the utility model is related, this detachable restructuring phase mask function is formed by stacking by two cosine functions with relative shift, and its one dimension function expression is:

$Q\left(x\right)=\mathrm{\&alpha;}\&CenterDot;\cos \left(\frac{\mathrm{\&pi;}}{2}(x+m_1)\right)-\mathrm{\&alpha;}\&CenterDot;\cos \left(\frac{\mathrm{\&pi;}}{2}(x+m_2)\right)$

$=2\mathrm{\&alpha;}\&CenterDot;\sin \left(\frac{\mathrm{\&pi;}(m_1-m_2)}{4}\right)\&CenterDot;\sin (\frac{\mathrm{\&pi;}}{2}x+\frac{\mathrm{\&pi;}}{4}({\mathrm{<figure-callout\; id="1"\; label="m"\; filenames="HDA00003026171300011.png,HDA00003026171300022.png"\; state="\{\{state\}\}">m</figure-callout>}}_1+m_2))$

In formula, α, m1 and m2 are the parameters of PHASE DISTRIBUTION function, and x is the normalization coordinate.The span of x is [1,1], and the span of side-play amount m1 and m2 is [1,1].

With reference to figure 1, in the system that the utility model proposes, after imageable target 1 is passed through conventional imaging camera lens 2 and detachable restructuring phase mask plate 3, form fuzzy intermediary image on image detector 4, then graphics processing unit 5 carries out deconvolution processing, finally obtains focusing on image 6 clearly.

The utility model can be regarded as has increased a phase mask plate (being placed on pupil) in traditional optical imaging system, after light path is passed through this phase mask plate, optical information is encoded, the modulation transfer function (MTF) that is whole optical system can change, although the mtf value after coding is less than the value before coding, but it null value can not occur in the situation that defocusing amount is arranged, so can not cause the loss of image detail information.Being imaged on image detector (as CCD) is a width blurred picture, with digital information processing system, it is decoded, and this moment, the system MTF value also can correspondingly improve, thereby recovered sharp keen image clearly.

Although the related wavefront coded imaging systems of the utility model on version with conventional wave before coded system similar, its maximum characteristic is: detachable restructuring phase mask plate 3 is comprised of two parts independently.As shown in Figure 1, by regulating two independent sectors with respect to the side-play amount of aperture center, this imaging system can be switched between the novel wavefront coded imaging systems three that common imaging system, the adjustable wavefront coded imaging systems of out of focus susceptibility and out of focus susceptibility and effective bandwidth all can be regulated.Therefore, the imaging system based on Separable combination phase mask plate that the utility model proposes possesses multiple and function more flexibly, is further developing wave-front coding imaging technology.

At present, wavefront coded system based on various phase mask plates only can play inhibiting effect to out of focus and the aberration relevant with out of focus, but, in case after the phase mask plate that the utility model is proposed is loaded on the aperture of system, effective imaging bandwidth of system can change dynamically, be the effect that this novel phase-plate has played optical filter, thereby can control the abundant information degree of the image of finally being caught by sensor.

Fig. 2～Fig. 5, bandwidth adjustable two aspects adjustable from the out of focus susceptibility respectively is illustrated by characteristic and the expection performance of several aspects such as data, chart and analog simulation imaging results to the novel imaging system that the utility model proposes.

First, the translation direction that two parts in phase-plate are introduced is opposite, and during equal and opposite in direction, the system of this moment is a wavefront coded imaging systems, but its modulate intensity can be controlled by a sinusoidal factor, and this sinusoidal factor function of translation variable exactly.According to the principle of wavefront coding technology, the variation of phase function modulate intensity will directly have influence on system to the sensitivity of out of focus, therefore by changing this translational movement, just can realize the adjustment to the out of focus susceptibility.Fig. 2 adopts Fisher information to weigh system to the sensitivity of out of focus as index.Can see, during the mtf value corresponding when middle blurred picture lower (Th is less), Fisher information is too less, thereby illustrative system has inhibiting effect preferably to out of focus, and the sinusoidal factor that mtf value corresponding to intermediate image introduced by translation is just controlled, so this system possesses the ability of dynamic adjustments out of focus susceptibility.Opposite and the equal and opposite in direction of two-part translation direction in phase-plate, i.e. m1=-m2, the system of this moment is an only out of focus susceptibility adjustable wavefront coded system, one group of corresponding optimization data is seen Fig. 2-1.(horizontal ordinate represents defocusing amount in Fig. 2-2; Ordinate represents the size of Fisher information.), Fisher information has represented the sensitivity of imaging system to out of focus, is worth littlely, just more insensitive to out of focus, just means that also phase-plate is stronger to the inhibition ability of out of focus.In addition, Th is a threshold value of introducing in optimizing process, is used for controlling the decline degree of modulation transfer function.Th is larger, and the value of the MTF after the phase-plate coding is just higher so, and middle blurred picture is just easier of restoring to obtain final large depth image.Th, the relation between out of focus susceptibility and Fisher information is: Th is less, and the inhibition ability of out of focus is just stronger, and Fisher information is also just less.

Second, when two parts in phase-plate are not introduced any skew, system will deteriorate to a common optical imaging system, be that its corresponding MTF curve is a typical triangle, (can see in Fig. 3 as shown in the black in Fig. 3, when translational movement was zero, system MTF showed that it is a common optical imaging system that this system changes in quality; When translational movement equated, system was a traditional wavefront coded imaging systems with maximum effective bandwidth; When random combine was carried out in the combination of translational movement, the effective bandwidth of system changed thereupon).After introducing side-play amount, the combination of different side-play amounts will produce different impacts to the maximum effective bandwidth of system.During identical and equal and opposite in direction, system can regard a common wavefront coded imaging systems as when the offset direction, and its corresponding bandwidth is maximum.And work as bias size not simultaneously, and the bandwidth of system can be made corresponding change along with the combination of m1 and m2, shows as colored Curves in Fig. 3, and wherein horizontal ordinate represents normalized spatial frequency, and ordinate represents normalized out of focus optical transfer function.。

The 3rd, any phase-plate all should be optimized design to obtain optimum parameter before real input is used.When providing Fig. 3, the parameter of phase-plate is (principle is that the modulate intensity factor-alpha keeps fixing) chosen at random.Since known that the phase-plate that the utility model proposes possesses the ability that is adjusted to the picture system bandwidth, so just should when optimizing, this point have been taken into account.Fig. 4 has just provided the optimum results that maximum effective bandwidth is respectively 0.5 times, 0.7 times and 0.9 times correspondence of theoretical value.Can see, marked change when occuring in the imaging system bandwidth at this moment, and the reduction of the corresponding mtf value of middle blurred picture illustrates that also the susceptibility of out of focus is changing simultaneously.Wherein, the phase-plate data of optimization provide in Fig. 4-1, and corresponding out of focus MTF curve family provides in Fig. 4-2, and the horizontal ordinate in Fig. 4-2 represents normalized spatial frequency, and ordinate represents normalized out of focus optical transfer function.Can see, if considered maximum effective bandwidth in the process of optimizing, out of focus MTF curve can go out the variation (height of mtf value) of out of focus susceptibility and the variation of bandwidth by simultaneous reactions so.

The 4th, in the research of coded system, what pay close attention to is mostly out of focus susceptibility, and seldom have, its potential bandwidth control ability is inquired into before for conventional wave.By research, this phase-plate that the utility model proposes, the system bandwidth regulating power that it possesses can also be applied to optical encryption except the low-pass optical filtering field can play a role.Fig. 5 has provided contrast with the conventional wavefront coded system simulation imaging effect of tradition, and (wherein, Fig. 5-1st is for the original image of analog simulation; Fig. 5-2 provided the data of umax=1 in Fig. 4-1 corresponding in the middle of analog imaging (Fig. 5-2-1) and restored image (Fig. 5-2-2); Middle analog imaging corresponding to a kind of typical phase-plate mentioned in the list of references (Fig. 5-3-1) and restored image (Fig. 5-3-2), in order to compare) have been provided in Fig. 5-3.Can see, the phase encoding system that the utility model proposes, its intermediate image that obtains almost can't be differentiated any Useful Information, and still can see clarification of objective to be imaged in the corresponding intermediate image of the wavefront coded system of routine.Therefore, the utility model proposes divides, can regulate phase-plate and have based on the dexterous type wavefront coded system of this phase-plate the potentiality that are applied to optical encryption.

The key that bandwidth is adjusted is that two parts in phase-plate can be according to demand, and take the aperture plane center as with reference to being offset independently, this has just proposed new designing requirement to the structure in aperture.Must design the dynamic adjustments device on the aperture of the novel adjustable wavefront coded imaging systems of bandwidth, the two parts that can satisfy in phase-plate satisfy specific side-play amount combination.

In addition, when reality is used, can carry out a demarcation in advance to system, build the funtcional relationship between side-play amount and system bandwidth, perhaps set up a discrete look-up table, in order to the system imaging bandwidth is carried out conscious adjusting.

Claims (5)

1. detachable restructuring phase mask plate, it is characterized in that: phase mask function corresponding to described detachable restructuring phase mask plate is to be formed by stacking by two cosine functions with relative shift, and its one dimension function expression is:

Wherein:

α, m1 and m2 are the parameters of PHASE DISTRIBUTION function;

X is the normalization coordinate, and the span of x is [1,1];

The span of side-play amount m1 and m2 is [1,1].

2. one kind based on the formed wavefront coded imaging systems of detachable restructuring phase mask plate claimed in claim 1, and it is characterized in that: described wavefront coded imaging systems comprises imaging lens, detachable restructuring phase mask plate, image detector and graphics processing unit; Described imaging lens, detachable restructuring phase mask plate and image detector are successively set on same light path; Described image detector is connected with graphics processing unit.

3. wavefront coded imaging systems according to claim 2, it is characterized in that: described detachable restructuring phase mask plate comprises the first mask plate and the second mask plate; Described the first mask plate and the second mask plate can carry out independent translation centered by aperture plane.

4. wavefront coded imaging systems according to claim 3 is characterized in that: the independent translation between described the first mask plate and the second mask plate comprises that translation direction is identical and translational movement equates, translation direction is identical and translational movement does not wait, the absolute value of translation direction difference and translational movement does not wait and the absolute value of translation direction difference and translational movement equates.

5. wavefront coded imaging systems according to claim 4, it is characterized in that: the independent translation between described the first mask plate and the second mask plate is the identical and translational movement of translation direction when equating, described wavefront coded imaging systems is common and does not have the imaging system of phase-modulation; Independent translation between described the first mask plate and the second mask plate is the identical and translational movement of translation direction when not waiting, and described wavefront coded imaging systems is effective imaging bandwidth and the wavefront coded imaging systems that can change the susceptibility of out of focus; Independent translation between described the first mask plate and the second mask plate is the absolute value of translation direction difference and translational movement when not waiting, and described wavefront coded imaging systems is the wavefront coded imaging systems that can change over the wide effect of image-tape; Independent translation between described the first mask plate and the second mask plate is the absolute value of translation direction difference and translational movement when equating, described wavefront coded imaging systems is the wavefront coded imaging systems that can regulate the out of focus susceptibility.

Images