CN101833755A - Method for correcting heterogeneities in optical beam image transmission system - Google Patents

Abstract

The invention discloses a method for correcting heterogeneities in a line-face conversion type optical beam image transmission system. The method is used for correcting in a photoelectrical system of an ultra-long line array detector for acquiring line-face conversion type optical beams by adopting a multi-section type graded one point method. After the method is used, the heterogeneities of images are obviously improved, thereby laying foundation for subsequent image analysis.

Description

A kind of fibre bundle passes the method as Nonuniformity Correction in the system

Technical field

The invention belongs to fibre bundle and pass, be meant that specifically a kind of line face conversion hysteria fibre bundle passes as heteropical bearing calibration in the system as system's image processing field.

Background technology

The linear array detector is the critical component in the scanning imaging system, and ultra-long array can enlarge sweep limit, improves systemic resolution.The super long alignment array detector is subject to technology at present and can't accomplishes more than 6000 yuan, adopt the photo electric imaging system of special-shaped optical fibre coherent fiber bundle formation to address this problem (patent No.: 200410089452.8, " pull-broom type ultrahigh resolution infrared focus plane image transmission beam conversion photo electric imaging system ").The cardinal principle of this electro-optical system is exactly to utilize the optical fiber image transmission beam of specific arrangement (promptly an end is that linear array is arranged, an other end is arranged for the face battle array) line target is converted into the appearance mark, the appearance mark images in planar array detector, the resulting image of detector recovers scan image through space-time transformation method (patent No.: 200510030793.2, " based on the focal plane array image space-time changing method of optical fiber coupling ").There is more serious heterogeneity in the image that recovers, mainly shows as in the image perpendicular to tangible stria is arranged on the direction of scanning, also has the band of broad, as shown in Figure 4.The generation of image non-uniform is mainly derived from three directions, and the one, there is heterogeneity in detector, and the 2nd, the heterogeneity that optical system is brought, the 3rd, the heterogeneity that fibre bundle itself brings.With respect to the heterogeneity that fibre bundle causes, the heterogeneity that optical system and detector bring can be ignored.Cause that the heteropical basic reason of fibre bundle is a transmitance difference between each optical fiber, to such an extent as to after the light of equal illumination entered optical fiber, the image that the fibre bundle output terminal obtains was inhomogeneous.The arrangement architecture of fibre bundle input end linear array and output end face battle array respectively as shown in Figures 2 and 3.As shown in Figure 2, fibre bundle input end linear array is Chinese character pin-shaped arrangement and forms by the bundle dislocation of K level optical fiber is overlapping, and optical fiber bundle is made of m * n unit optical fiber.Fibre bundle output end face battle array is corresponding one by one with input end linear array optical fiber, as shown in Figure 3, the output end face battle array by corresponding with the input end linear array strange level 1.-the idol level 2.-3. optical fiber bundle of Qi level ... order is formed by stacking.According to the design feature of fibre bundle the reason that the fibre bundle heterogeneity produces is analyzed below.The intrafascicular number that comprises optical fiber of fibre optic image transmission is huge, is 4 * 220 yuan with optical fiber bundle, and K 40 calculates, and a fibre bundle constitutes by surpassing 35000 optical fiber, and so many optical fiber can not be accomplished between the every optical fiber all identical.The nuance of fibre core diameter, cladding diameter, optical fiber length, fiber optic materials, and the difference of fiber end face verticality all can cause the light path difference of light in optical fiber between the optical fiber, thereby the absorption loss of optical fiber is different with scattering loss, cause transmitance difference between the different fiber, finally on the image that obtains, just shown as striped and existed.In addition, the fibre bundle manufacture craft also has bigger influence to the transmitance of optical fiber.Because fibre bundle row silk still relies on manual arrangement at present, so in the process of optical fiber boundling, fibre bundle input end or the optical fiber out-of-flatness of output terminal one deck may occur or distortion occur, cause emergent ray not concentrated, leaded light is indifferent and scattering influences the optical fiber transmitance.When being squeezed in the process that fibre bundle input end linear array one-level (as shown in Figure 2) is being arranged or twisting, the transmitance of whole level optical fiber all can be affected, and shows on the final image to be exactly to have band to produce (as shown in Figure 4).Yellow silk or dark silk also can appear in fibre bundle in manufacturing process, the transmitance of these optical fiber is starkly lower than the transmitance of optical fiber on every side, shows as darker striped on image.

At present, also fewer about the research of optical fiber image transmission beam Nonuniformity Correction algorithm aspect, but the infrared focal plane asymmetric correction has had a lot of effectively algorithms, these algorithm values must be used for reference.The main algorithm of infrared focus plane nonuniformity correction has point calibration and adaptively correcting two classes.Wherein point calibration comprises a point calibration, two point calibrations, multiple spot correction etc.Adaptively correcting mainly contains correcting algorithm based on scene, neural network algorithm, continuous time and proofreaies and correct etc.When selecting correcting algorithm, mainly consider two point, algorithm validity and complicacy.We need a kind of not only effectively but also simple algorithm, could when guaranteeing calibration result, guarantee the real-time of Flame Image Process like this.It is extensively a kind of bearing calibration of utilization in the infrared focus plane that two-point method is proofreaied and correct, and it has considered the gain coefficient unevenness and the biasing unevenness of detector.The unevenness of wherein setovering is meant that when incident light illumination is zero detector output response is non-vanishing, promptly has black level.And optical fiber image transmission beam is different with detector, does not have the black level phenomenon, when incident light illumination is zero and no-output.So without the corrects bias unevenness.So adopt one point method to proofread and correct, only the heterogeneity of gain coefficient proofreaied and correct.It is that detector all pixel response corrections in scaling point place are its average response that traditional one point method is proofreaied and correct, and the coefficient that obtains is exactly a correction coefficient, and is not suitable for line face conversion hysteria optical fiber image transmission beam Nonuniformity Correction.Because because fibre bundle manufacture craft problem, whole transmitance may exist than big difference between each grade optical fiber bundle, if adopt traditional one point method to proofread and correct, is about to the fiber optic element response corrections to its average response, the band in will correcting image.Secondly, adopt traditional one point method timing, just have reasonable calibration result when having only the actual illumination of target near scaling point illumination.

Summary of the invention

The object of the present invention is to provide the method for a kind of biography of line face conversion hysteria fibre bundle formation,, more help the detection of target so that the image that recovers has homogeneity preferably as fibre bundle Nonuniformity Correction in the system.

As showing, establish fibre bundle input end linear array by the sub-Shu Zucheng of K level optical fiber as Fig. 2, K is a natural number.Every grade of optical fiber bundle is by m layer optical fiber, and every layer of n unit optical fiber is that m * n unit optical fiber is formed.Strange level (1., 3. ...) and the idol level is (2., 4. ...) optical fiber bundle dislocation is overlapped into Chinese character pin-shaped arrangement and forms.Face battle array end is corresponding to the linear array end strange level-idol level-Qi level optical fiber bundle ... mode superpose to arrange and form.Because when recovering image, only need the one deck in the m layer optical fiber just can recover scan image, so Nonuniformity Correction of one deck optical fiber wherein in the just m layer optical fiber that we discuss, the bearing calibration of other layers is identical, in literary composition, mention k (k=1,2,3 ... when K) pixel of level optical fiber bundle is counted, that refer to is exactly the pixel number of wherein one deck of that one-level, i.e. m=1.

In order to guarantee the real-time of image, select a kind of effectively and simple algorithm come heterogeneity is proofreaied and correct.According to the arrangement architecture of fibre bundle and the reason of fibre bundle heterogeneity generation, adopt the one point method that is fit to the fibre bundle Nonuniformity Correction to proofread and correct, we claim that it is multi-stage stepped one point method.Main thought is in the detector dynamic range, to choose φ ₀, φ ₁, φ ₂, φ ₃φ _MA different M+1 level of illumination responds each fiber optic element of fibre bundle and calibrates, when each illumination level is calibrated, be divided into the K group with calibrating the progression K of image according to the fibre bundle input end, respectively each group is asked the average response value of respective sets, with average response value the maximum in the K group as calibration reference value, each fiber optic element response and calibration reference value are divided by, and the gained coefficient is the correction coefficient of fiber optic element corresponding group under corresponding illumination conditions.Proofreading and correct k (k=1,2,3 ... K) group optical fiber bundle i (i=1,2, when n) individual fiber optic element responded, this fiber optic element response of judgement was earlier proofreaied and correct with the correction coefficient of corresponding fiber optic element under this scaling point near the sub average response value of restrainting of corresponding optical fiber under which scaling point.

Multi-stage stepped one point method trimming process is as follows:

One diffuse reflection blank is placed whole optical system front end (Fig. 1), shine the illuminance of diffuse reflection blank by change, or change the diffuse reflection blank of different reflectivity, can change in conjunction with aperture in the optical system, obtain the calibration image of M+1 illumination level, this M+1 illumination level in the detector dynamic range, M+1 the desirable 5-10 level of illumination level.The calibration image of M+1 illumination level also can obtain by integrating sphere, and the 1st illumination level is near detected target brightness value lower limit, and M+1 illumination level is near the detected target brightness value upper limit.According to the progression K of fibre bundle input end linear array, will calibrate the image response value and be divided into the K group, each organizes the response of corresponding one-level optical fiber bundle.Respectively each group is asked its average response (formula 1), obtain under the j level illumination, the average response of k level optical fiber bundle, and the response (formula 2) of restrainting as optical fiber at different levels under this illumination conditions respectively, with the maximal value of average response as calibration reference value (formula 3), with the response of calibration reference value, obtain the correction coefficient (formula 4) of the intrafascicular i of k level optical fiber unit optical fiber under the i level illumination divided by each fiber optic element.Formula is as follows:

${\stackrel{\‾}{V}}_{j,k}=\underset{i=1}{\overset{N_k}{\mathrm{\Σ}}}{V}_{i,k}/N_k---\left(1\right)$

${\mathrm{\φ}}_{j,k}={\stackrel{\‾}{V}}_{j,k}---\left(2\right)$

${\mathrm{Vref}}_j=\max \left({\stackrel{\‾}{V}}_{j,k}\right)---\left(3\right)$

$a_{i,j,k}=\frac{{\mathrm{Vref}}_j}{V_{i,k}}---\left(4\right)$

K=1 wherein, 2,3 ... K; I=1,2,3 ... N _kJ=0,1,2, M.K is the progression of fibre bundle input end linear array, the level of illumination number when M+1 represents to calibrate, N _kRepresent first number of k level optical fiber bundle one deck optical fiber, because fibre bundle adopts tight hexangle type to arrange, and in manufacturing process, can't accurately control the fiber optic element number of each grade, so fiber optic element number not at the same level can be different.In the formula (1) Be illustrated in the average response value of k level optical fiber bundle under the j level illumination, V _{I, k}The response of representing the intrafascicular i of k level optical fiber unit optical fiber.φ in the formula (2) _{J, k}Represent the reference response value under the sub-Shu Zaidi j of the k level optical fiber level illumination.Vref in the formula (3) _jRepresent the calibration reference value under the j level illumination.A in the formula (4) _{I, j, k}Represent under the j level illumination correction coefficient of the intrafascicular i of k level optical fiber unit optical fiber.

At timing, according to fiber optic element response V _{I, k}The illumination range at place reads in corresponding correction coefficient a _{I, j, k}Proofread and correct, proofreading and correct the back response is V _{I, k}'.Specifically be exactly the response V that finds out with the intrafascicular i of k level optical fiber unit optical fiber _{I, k}Immediate reference response value φ _{J, k}, according to φ _{J, k}Corresponding illumination level and optical fiber bundle read in corresponding correction coefficient a _{I, j, k}, then

V _i，k′＝a _i，j，k×V _i，k (5)

Fiber optic element to each grade optical fiber bundle in the fibre bundle is proofreaied and correct the image after can obtaining proofreading and correct with above method.

The present invention has following characteristics and technique effect:

1. image non-uniform obtains calibration preferably.

2. the striped that causes owing to the fibre bundle heterogeneity in the image significantly reduces.

3. the band that causes owing to heterogeneity between the optical fiber bundle in the image is eliminated substantially.

4. algorithm is simple, helps the real-time of Flame Image Process.

Description of drawings

Device synoptic diagram when Fig. 1 calibrates the fibre bundle heterogeneity.

Fig. 2 is a line face conversion hysteria optical fiber image transmission beam input end arrangement architecture.

Fig. 3 is a line face conversion hysteria optical fiber image transmission beam output terminal arrangement architecture.

Fig. 4 is the image that does not pass through Nonuniformity Correction.

Fig. 5 adopts the image after multi-stage stepped one point method is proofreaied and correct.

Embodiment

Below with the present invention one based on the example that is applied as in the project of line face conversion optical fiber image transmission beam system, the specific embodiment of the present invention is elaborated:

The optical fiber image transmission beam arrangement architecture is in the project: fibre bundle input end linear array is Chinese character pin-shaped arrangement by the dislocation of 40 grades of optical fiber bundle is overlapping, and every grade of optical fiber bundle divides 4 layers closely to arrange and form by 4 * 210 yuan of optical fiber.The fibre bundle output terminal is that 210 * 160 yuan of face battle arrays are arranged.When recovering scan image, only used the 2nd layer in 4 layers of optical fiber, thus Nonuniformity Correction only carry out at the 2nd layer of optical fiber of optical fiber bundles at different levels, so when mentioning certain grade of optical fiber bundle, acquiescence referring to the second layer optical fiber of certain grade of optical fiber bundle.If desired other layer optical fiber is proofreaied and correct, then method is identical.

Adopting reflectivity respectively is 100%, 80%, 60%, 40%, 20% diffuse reflector, and, produce the optical fiber image transmission beam calibration image under 10 illumination levels in conjunction with the adjusting of aperture in the optical system.

Fiber optic element response corresponding in the calibration image of each illumination level all is divided into 40 groups, and each organizes the response of corresponding one-level optical fiber bundle, and by formula the respectively average response of group is obtained in (1)～(4) respectively

Optical fiber is at the reference response value φ of each illumination level _{J, k}, calibration reference value Vref _j, the correction coefficient a of each fiber optic element _{I, j, k}Since the 1st grade of optical fiber bundle, with the response V of the intrafascicular fiber optic element of each grade optical fiber _{I, k}With 10 corresponding reference response value φ of this optical fiber bundle _{J, k}Make comparisons, find near V _{I, k}Reference response φ _{J, k}, φ _{J, k}Correction coefficient a under the corresponding illumination level _{I, j, k}As the correction coefficient of this fiber optic element response, correction coefficient multiply by the response after the fiber optic element response can obtain proofreading and correct.

As shown in Figure 4, during without Nonuniformity Correction, there are a lot of stripeds just to deposit in the image, band is also clearly proofreaied and correct image afterwards as shown in Figure 5 through multi-stage stepped one point method, as can be seen, image non-uniform has obtained tangible improvement, and striped also significantly reduces, and the bar zoning has also been eliminated.

Claims (1)

1. a fibre bundle passes the method as Nonuniformity Correction in the system, it is characterized in that may further comprise the steps:

1) obtain the response of each fiber optic element of optical fiber image transmission beam under M+1 illumination conditions, obtain M+1 width of cloth calibration image, wherein M+1 is 5 to 10 a natural number, and the expression calibration is counted;

2) under each illumination conditions, the response of fiber optic element is divided into the K group, wherein K is a natural number, represent the progression of optical fiber image transmission beam input end linear array optical fiber bundle, obtains the average response that each is organized respectively

${\stackrel{\‾}{V}}_{j,k}=\underset{i=1}{\overset{N_k}{\mathrm{\Σ}}}{V}_{i,k}/N_k---\left(1\right)$

In the formula: N _kFirst number of representing the intrafascicular optical fiber of k level optical fiber, k=1,2,3...K, K are the progression of optical fiber image transmission beam input end linear array, V _{I, k}The response of representing the intrafascicular i of k level optical fiber unit optical fiber, i=1,2,3...n, n represent the fiber optic element number of each grade optical fiber bundle;

Average response with each group

Respectively as the sub response φ that restraints of optical fiber at different levels under this illumination conditions _{J, k}:

${\mathrm{\φ}}_{j,k}={\stackrel{\‾}{V}}_{j,k}---\left(2\right)$

With the calibration reference value Vref of its maximal value as each fiber optic element under this illumination _j

${\mathrm{Vref}}_j=\max \left({\stackrel{\‾}{V}}_{j,k}\right)---\left(3\right)$

3) obtain the correction coefficient a of corresponding fiber optic element under this illumination conditions by calibration reference value _{I, j, k}

$a_{i,j,k}=\frac{{\mathrm{Vref}}_j}{V_{i,k}}---\left(4\right)$

4) fiber optic element response V _{I, k}With φ _{J, k}Compare, select near V _{I, k}φ _{J, k}, the correction coefficient under its corresponding illumination conditions is proofreaied and correct;

5) fiber optic element response and pairing correction coefficient multiply each other,

V _i，k′＝a _i，j，k×V _i，k (5)

Response V after obtaining proofreading and correct _{I, k}'.

Images