CN101510012B - Composite phase mask plate - Google Patents

Abstract

The invention discloses a composite phase mask, the phase distribution function of which contains two different functions, namely, a sinusoidal type function and a third power type function. The function expression of the phase distribution function Theta(x, y) is as follows: Theta(x, y) is equal to Alpha question mark (x<3> plus y<3>) plus Beta question mark (sin(Omega question mark x) plus sin(Omega question mark y)), and in the expression, Beta question mark (sin(Omega question mark x) plus sin(Omega question mark y)) is a sinusoidal type function, and Alpha question mark (x<3> plus y<3>) is a third power type function; wherein Alpha is the amplitude of the third power type function, Beta is the amplitude of the sinusoidal type function, Omega expresses the angular frequency of the sinusoidal type function, and x, y is space coordinate with normalized aperture plane. The invention also discloses an imaging system which adopts the composite phase mask compounded by the sinusoidal type function and the third power type function and has smaller numerical value of the Fisher information, and the phase mask is not sensitive to defocusing, thus having better expansion capability of depth of focus.

Description

A kind of composite phase mask plate

Technical field

The present invention relates to a kind of phase mask plate, relate in particular to two kinds of compound composite phase mask plates of function of a kind of cube type and sinusoidal pattern

Background technology

As everyone knows, any optical system all has certain depth of field, has only the object within the field depth can be by blur-free imaging, and the object that exceeds field depth will thicken through the formed image of optical system, thereby causes losing of details, texture.

As far back as nineteen sixty, W.T.Welford has just inquired into the use ring aperture, and promptly the central obscuration mode is come the possibility of the expansion optical system depth of field.1987, Ting-Chung Poon and MasoudMotamedi are on the basis of using ring aperture, rely on the digital image restoration algorithm to verify depth of field expansion effect practically, this following period of time from the end of the eighties to the beginning of the nineties, people such as Ojeda-Castaneda Jorge use classical apodization also system's this problem of depth of field continuation to be launched extensive and deep research.Studies show that, change the good result that aperture shape can be created the big depth of field, but this effect is with the logical light quantity of sacrificial system with to reduce resolution be that cost is reached.In addition, from the mid-80 so far, also have many non-mainstream methods to be suggested the depth of field that is used for the expansion optical system, use Fresnel lens, Zeev Zalevsky and Shai Ben-Yaish to use o light, the e light characteristic of birefringece crystal to obtain the effect of depth of field continuation too as people such as Guy Indebetouw.

Though said method has all played positive effect to the depth of field of expansion optical system, but effect all is more limited comparatively speaking, real breakthrough starts from nineteen ninety-five, the E.R.Dowski of Univ Colorado-Boulder USA is in traditional imaging system, the ambiguity function that uses in the field of radar and out of focus optical transfer function combined proposed wavefront coded imaging technique, and derived classical cube PHASE DISTRIBUTION function mask plate, after this researcher has proposed logarithmic, exponential type, polynomial type PHASE DISTRIBUTION function mask plate again successively.

Can determine the physical arrangement of mask plate according to the PHASE DISTRIBUTION function, as in Chinese invention patent 200410018159.2, disclosing the method for a kind of discrete continuous mixed-phase type phase-plate and realization super-resolution thereof, the phase function of this phase-plate comprises two parts: a part is the continuous distribution phase-plate, and another part is the stepped ramp type phase-plate.For example the PhD dissertation of the Wanli Chi of U.S. Rochester optical centre " Computational Imaging System for Extended Depth of Field "chapter 4 " Lens Design and Fabrication " has promptly been introduced the method for determining mask plate face shape according to the PHASE DISTRIBUTION function all-sidely again.

Wavefront coded imaging technique can enlarge the depth of field of optical system effectively by image restoration is combined with optical design under the prerequisite of inexcessive sacrificial light systemic resolution and logical light quantity.Researcher has been done a large amount of theoretical analysises and experimental study, has affirmed the powerful power that wavefront coded imaging technique had, and has proved and verified that the depth of field improves 10 times effect.This light/number hybrid imaging technology has been broken the intrinsic restriction of conventional optical systems when extended depth-of-field, is a kind of imaging technique that practical application foreground is arranged very much, is subjected to paying close attention to widely.

Summary of the invention

The invention provides a kind of composite phase mask plate with better depth of field scalability.

A kind of composite phase mask plate, the PHASE DISTRIBUTION function of described composite phase mask plate comprise sinusoidal pattern and two kinds of functions of cube type, the PHASE DISTRIBUTION function # (x, functional expression y) is as follows:

θ(x，y)＝α·(x³+y³)+β·(sin(ω·x)+sin(ω·y))

In the formula, β (sin (ω x)+sin (ω y)) is the sinusoidal pattern function, α (x³+ y³) be the cube type function; Wherein, α is the amplitude of cube type function, and β is the amplitude of sinusoidal pattern function, and ω represents the angular frequency of sinusoidal pattern function, and x, y are the normalized volume coordinate of aperture plane.

Wherein, as preferably, cube type function amplitude α value is between 90 to 300, and sinusoidal pattern function amplitude β value is between scope 50 to 260.The angular frequency value of sinusoidal pattern function in scope at 0.3 π between 0.6 π because not obvious when the improvement in performance of the too small composite phase plate of ω value, the excessive phase-plate that then causes of ω value is blocked up, has increased difficulty of processing.

In the phase-plate of various forms PHASE DISTRIBUTION function, cube type phase-plate is classical type, can realize bigger depth of field expansion.Superpose on the basis of the cube type function composite phase mask plate plate of sinusoidal component of the present invention has bigger depth of field extended capability.

A kind of imaging system is made up of imaging lens, composite phase mask plate, image detector, graphics processing unit.

The PHASE DISTRIBUTION function of described composite phase mask plate comprises sinusoidal pattern and two kinds of functions of cube type, and functional expression is as follows:

θ(x，y)＝α·(x³+y³)+β·(sin(ω·x)+sin(ω·y))

In the formula, α is the amplitude of cube type function, and β is the amplitude of sinusoidal pattern function, and ω represents the angular frequency of sinusoidal pattern function, and x, y are the normalized volume coordinate of aperture plane.

In imaging system, imageable target by imaging lens and composite phase mask plate after, on image detector, form fuzzy intermediary image, graphics processing unit carries out deconvolution processing to intermediary image then, finally obtains focusing on distinct image.

Imaging lens can adopt existing various imaging lens.Image detector can adopt CCD etc.

A kind of imaging system of the present invention has increased a composite phase mask plate in traditional optical imaging system, be placed on the pupil.After light path is passed through this composite phase mask plate, optical information is encoded, be that optical system its modulating transfer function value in bigger out of focus scope changes very little (promptly insensitive to out of focus), the transport function of simultaneity factor does not have zero point or nearly zero point in passband.This means that when there was out of focus in system, the information that exceeds the primal system field depth was not lost, just be encoded in a kind of known mode.Being imaged on the CCD is a width of cloth blurred picture, with digital information processing system to its decoding of deconvoluting, thereby recover sharp keen distinct image.

In wavefront coded field, Fisher information is one of important indicator of estimating depth of field extended capability.According to the definition of Fisher information, in the ideal case, no matter the out of focus parameter is got any value, and Fisher information all should equal zero.Therefore, the numerical value of Fisher information is more little, just means that phase-plate is insensitive more to out of focus, and depth of field extended capability is good more.

The present invention adopts the Fisher information curve of imaging system of the compound composite phase mask plate of sinusoidal pattern and two kinds of functions of cube type little, has depth of field extended capability preferably.

Description of drawings

Fig. 1 is the structural representation of a kind of imaging system of the present invention;

Fig. 2 is the comparison synoptic diagram of Fisher information curve and the Fisher information curve of the imaging system that adopts cube type phase mask plate that adopts the imaging system of composite phase mask plate of the present invention.

Embodiment

A kind of composite phase mask plate, the PHASE DISTRIBUTION function of composite phase mask plate comprise sinusoidal pattern and two kinds of functions of cube type, the PHASE DISTRIBUTION function # (x, functional expression y) is as follows:

θ(x，y)＝α·(x³+y³)+β·(sin(ω·x)+sin(ω·y))

In the formula, β (sin (ω x)+sin (ω y)) is the sinusoidal pattern function, α (x³+ y³) be the cube type function; Wherein, α is the amplitude of cube type function, and β is the amplitude of sinusoidal pattern function, and ω represents the angular frequency of sinusoidal pattern function, and x, y are the normalized volume coordinate of aperture plane.

The face shape of a kind of composite phase mask plate of the present invention and the face shape of exponential type phase mask plate are relatively referring to accompanyingdrawing 2, the face shape of a kind of composite phase mask plate of the present invention dots in accompanyingdrawing 2, and the face shape of exponential type phase mask plate is represented with solid line in accompanyingdrawing 2.

Referring to Fig. 1, a kind of imaging system of the present invention is made up ofimaging lens 2, compositephase mask plate 3,image detector 4,graphics processing unit 5.

Afterimageable target 1 is passed throughimaging lens 2 and compositephase mask plate 3, form fuzzy intermediary image onimage detector 4,graphics processing unit 5 carries out deconvolution processing then, finally obtains focusing ondistinct image 6.

The PHASE DISTRIBUTION function of composite phase mask plate comprises sinusoidal pattern and two kinds of functions of cube type, the PHASE DISTRIBUTION function # (x, functional expression y) is as follows:

θ(x，y)＝α·(x³+y³)+β·(sin(ω·x)+sin(ω·y))

In the formula, β (sin (ω x)+sin (ω y)) is the sinusoidal pattern function, α (x³+ y³) be the cube type function; Wherein, α is the amplitude of cube type function, and β is the amplitude of sinusoidal pattern function, and ω represents the angular frequency of sinusoidal pattern function, and x, y are the normalized volume coordinate of aperture plane.

In wavefront coded field, Fisher information is one of important indicator of estimating depth of field extended capability.According to the definition of Fisher information, in the ideal case, no matter the out of focus parameter is got any value, and Fisher information all should equal zero.Therefore, the numerical value of Fisher information is more little, just means that phase-plate is insensitive more to out of focus, and depth of field extended capability is good more.

The present invention adopts the Fisher information curve ratio of Fisher information curve and the imaging system that adopts cube type phase mask plate of imaging system of composite phase mask plate referring to accompanyingdrawing 2.

During data after α, β, each parameter of ω adopt in the table 1 nine groups to optimize respectively, the Fisher information curve of imaging system that adopts cube type phase mask plate is shown in the solid line in the accompanyingdrawing 2, and the Fisher information curve of imaging system that adopts the compound composite phase mask plate of two kinds of functions of sinusoidal pattern of the present invention and cube type is shown in the dotted line in the accompanyingdrawing 2.

Tables of data after table 1 α, β, nine groups of optimizations of each parameter of ω

By contrast adopt the PHASE DISTRIBUTION function be cube type mask plate imaging system Fisher information curve and adopt the Fisher information curve of PHASE DISTRIBUTION function for the imaging system of the compound composite phase mask plate of sinusoidal pattern of the present invention and two kinds of functions of cube type, the Fisher information curve of imaging system of the present invention is starkly lower than the former as can be seen, therefore has better depth of field extended capability.

Claims (2)

1. composite phase mask plate, it is characterized in that: the PHASE DISTRIBUTION function of described composite phase mask plate comprises sinusoidal pattern and two kinds of functions of cube type, the PHASE DISTRIBUTION function # (x, y) functional expression is as follows:

θ(x，y)＝α·(x³+y³)+β·(sin(ω·x)+sin(ω·y))

In the formula, β (sin (ω x)+sin (ω y)) is the sinusoidal pattern function, α (x³+ y³) be the cube type function; Wherein, α is the amplitude of cube type function, and β is the amplitude of sinusoidal pattern function, and ω represents the angular frequency of sinusoidal pattern function, and x, y are the normalized volume coordinate of aperture plane.

2. imaging system, form by imaging lens, composite phase mask plate, image detector, graphics processing unit, it is characterized in that: the PHASE DISTRIBUTION function of described composite phase mask plate comprises sinusoidal pattern and two kinds of functions of cube type, and functional expression is as follows:

θ(x，y)＝α·(x³+y³)+β·(sin(ω·x)+sin(ω·y))

In the formula, α is the amplitude of cube type function, and β is the amplitude of sinusoidal pattern function, and ω represents the angular frequency of sinusoidal pattern function, and x, y are the normalized volume coordinate of aperture plane;

In imaging system, imageable target by imaging lens and composite phase mask plate after, on image detector, form fuzzy intermediary image, graphics processing unit carries out deconvolution processing to intermediary image then, finally obtains focusing on distinct image.

Images