CN1298283C - Iris image collecting method - Google Patents
Iris image collecting method Download PDFInfo
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- CN1298283C CN1298283C CNB2003101135690A CN200310113569A CN1298283C CN 1298283 C CN1298283 C CN 1298283C CN B2003101135690 A CNB2003101135690 A CN B2003101135690A CN 200310113569 A CN200310113569 A CN 200310113569A CN 1298283 C CN1298283 C CN 1298283C
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Abstract
The present invention relates to a method for collecting iris images, which belongs the technical fields of biological characteristic identification and safety certification. In the method, firstly, a plurality of iris images are collected at real time; the inner edges of irises in the collected iris images are respectively positioned to determine the position of a pupil; a gray scale threshold value is set, gray scale values of threshold values of pixel points in the pupil range are compared, the pixel points of which the gray scale values are higher than the threshold values are counted to obtain the ratios of the counted values to the pixel points in the whole pupil range; the ratios are orderly from small to large at real time, the front n iris images in the ordered result are selected, images firstly passing through iris characteristic detection in the n images are selected, and the final collected image is obtained. In the method, the definition of the iris images are evaluated by calculating the image of an infrared reference light source which is in the pupil and is not dispersed; thereby, the present invention greatly reduces the calculation quantity of quality evaluation, accelerates image collection and ensures the constancy of image quality.
Description
Technical field the present invention relates to a kind of acquisition method of iris image, belongs to living things feature recognition and secure authentication technology field.
In the background technology iris identification system, the important work of the first step is the collection of iris image, and in order to guarantee the quality of iris identification, iris is partly very clear in the image that image acquisition phase must guarantee to collect.In the existing technology, main computed image edge gray scale difference or image frequency domain energy indexes are selected candidate's iris image according to this index, as " How iris recognition works " (John Daugman,
Http:// www.cl.cam.ac.uk/users/jgd1000/irisrecog.pdf), " a kind of quality evaluating method of sequence iris type image " (Li Liangui etc., observation and control technology, 20 (5)), " A Emerging bio-metric Technology " (R.P.Wildes, Proceedings of IEEE, 1997,85 (9)) with " based on the iris image quality evaluation algorithms of WAVELET PACKET DECOMPOSITION " (old halberd, 2003 the 43rd the 3rd phases of volume of Tsing-Hua University's journal (natural science edition)) shown in, and this articulation index refers generally to the high fdrequency component index of image or the local contrast index of image.In actual use, usually following problem can appear:
1, the stringy influence of moving: adopting the interlacing scan photographic head, the motion wire drawing that moving image produces is picture now, can produce very high articulation index; For the object of rapid movement,, also can produce the wire drawing phenomenon because the photographic head primary field is swept the restriction of speed.
2, effect of noise: under the open environment, noise level can produce obvious variation with different illumination conditions.The picture noise level that illumination is good is low, and the image of illumination difference, noise level will become very high, and the automatic equalization function of photographic head can make noise amplify.Like this, when the computed image definition, under the low-light (level) situation, excessive noise will produce higher high fdrequency component index, make to adopt high fdrequency component to judge that image definition is ineffective.
3, amount of calculation is bigger: because the analysis of iris image definition is to be based upon on the basis of iris position calculation in the image, this further increases the amount of calculation of existing image definition, the needed hardware performance of computing is too high, be unfavorable for the reduction of hardware equipment cost, thereby limited the application of iris authentication system.Existing iris image acquiring method is all evenly realized under the lighting condition at iris, as document " A System forAutomated Iris Recognition " (R.P.Wildes, et al, Proceedings of the Second IEEEWorkshop on Applications of Computer Vision, 1994, p121) described.
Summary of the invention the objective of the invention is to propose a kind of acquisition method of iris image, by to the not calculating of the infrared reference light source imaging of disperseization in the pupil, the definition of assessment iris image, to reduce the amount of calculation of image quality assessment, accelerate the picking rate of image, guarantee the constant of picture quality simultaneously.
The acquisition method of the iris image that the present invention proposes comprises following each step:
(1) gathers several iris images in real time;
(2) several iris images of gathering are carried out iris inward flange location respectively, to determine pupil position;
(3) set a gray threshold, each the pixel gray value and the threshold value that will be in the above-mentioned pupil scope compare, and the pixel that is higher than threshold value for gray value is counted, thereby obtain the ratio of the pixel number in this count value and the whole pupil scope;
(4) above-mentioned ratio is sorted from small to large in real time, select in the ranking results before n width of cloth iris image, select the image that detects by iris feature at first in this n width of cloth image, be final images acquired.
In the said method, the localized method of iris inward flange comprises the steps:
(1) sets a gray threshold, in each column direction of image, find out the sequence that gray value is lower than threshold value;
(2) select the longest sequence from above-mentioned sequence, then the center of the mid point of this sequence and pupil undetermined is in same horizontal line;
(3) pixel on the above-mentioned horizontal line is tested, rejected the pixel that gray value is higher than above-mentioned setting threshold, obtain the left and right border of pupil.
The method that iris feature detects in the said method comprises the steps:
(1) for being positioned at all pixels in pupil center pixel place horizontal line left side, obtain their shade of gray curve, select be higher than a certain threshold value the local maximum point as candidate's left border point;
(2) for being positioned at all pixels in horizontal line right side, pupil center pixel place, obtain their shade of gray curve, select be higher than a certain threshold value the local maximum point as candidate's right side boundary point;
(3) from formation of above-mentioned candidate's left margin point and the formation of right margin point, choose a point respectively arbitrarily, form an iris external boundary by these two points;
(4) calculate the average gray of being had a few on the above-mentioned iris external boundary;
(5) calculate the partial differential value of above-mentioned average gray to current iris radius, the pairing iris boundary of maximum partial differential absolute value is the external boundary of iris undetermined.
(6) iris external boundary undetermined and known inner boundary are compared with the inside and outside boundary characteristic of experience iris, meet empirical model, promptly pass through feature detection.
The acquisition method of the iris image that the present invention proposes, by to the not calculating of the infrared reference light source imaging of disperseization in the pupil, assess the definition of iris image, thereby significantly reduced the amount of calculation of quality evaluation, accelerate the picking rate of image, guaranteed the constant of picture quality simultaneously.By adopting the infrared lamp illumination of not disperse, judge the quality of picture quality fast, avoided the uneven influence that produces of motion wire drawing and noise level, reduced the amount of calculation of image definition assessment simultaneously significantly, satisfied the requirement that image is handled in real time.
Description of drawings
Fig. 1 is the iris image sample of gathering in real time.
Fig. 2 is an iris inward flange positioning result.
Fig. 3 is the shade of gray curve of iris.
Fig. 4 is an iris outward flange positioning result.
Fig. 5 loses burnt image and its result through described algorithm process.
Fig. 6 is coking image and its result through described algorithm process.
The specific embodiment
The acquisition method of the iris image that the present invention proposes is gathered several iris images at first in real time; Several iris images of gathering are carried out iris inward flange location respectively, to determine pupil position; Set a gray threshold, each the pixel gray value and the threshold value that will be in the above-mentioned pupil scope compare, and the pixel that is higher than threshold value for gray value is counted, thereby obtain the ratio of the pixel number in this count value and the whole pupil scope; Above-mentioned ratio is sorted from small to large in real time, select in the ranking results before n width of cloth iris image, select the image that detects by iris feature at first in this n width of cloth image, be final images acquired.
In the said method, the localized method of iris inward flange is: set a gray threshold, find out the sequence that gray value is lower than threshold value in each column direction of iris image (as shown in Figure 1); Select the longest sequence from above-mentioned sequence, then the center of the mid point of this sequence and pupil undetermined is in same horizontal line; Pixel on the above-mentioned horizontal line is tested, rejected the pixel that gray value is higher than above-mentioned setting threshold, obtain the left and right border of pupil, as shown in Figure 2.
In the said method, the method that iris feature detects is: for being positioned at pupil center's all pixels in pixel place horizontal line left side, obtain their shade of gray curve, select be higher than setting threshold the local maximum point as candidate's left border point; For being positioned at all pixels in horizontal line right side, pupil center pixel place, obtain their shade of gray curve, select be higher than setting threshold the local maximum point as candidate's right side boundary point, Fig. 3 is the shade of gray curve of iris left pixel, among Fig. 3, T
gBe preset threshold, Z
1, Z
2, Z
3Be the left border point of selecting.From the above-mentioned formation of selecting of left margin point and the formation of right margin point, choose a point respectively arbitrarily, form an iris external boundary by these two points; Calculate the average gray of being had a few on this iris external boundary; Calculate the partial differential value of this average gray to current iris radius, the pairing iris boundary of maximum partial differential absolute value is the external boundary of iris undetermined; Iris external boundary undetermined and known inner boundary compared with the inside and outside boundary characteristic of experience iris, meet empirical model, promptly think and pass through feature detection.
In the inventive method, the principle of iris inward flange location institute foundation is: the intensity profile by analysis image can learn that the gray value of different parts such as pupil, iris, the white of the eye, eyelid is inequality.Because the logical light of pupil, therefore the gray value of pupil is very low in image, and intensity profile is very even, significantly is different from other parts of eyes.Therefore can utilize the intensity profile characteristic of pupil, pupil and iris be separated by setting appropriate threshold.
In the inventive method, during iris outward flange location, in the candidate queue of resulting iris left margin and right margin, respectively choose a point and form an iris external boundary.Choose all possible combination, calculate the value of following round detector on these iris external boundaries.Make following round detector reach the external boundary that peaked iris external boundary is exactly real iris, Figure 4 shows that iris outward flange positioning result.
In the following formula, G
δ(r) be a smooth function, can select Gaussian function, r for use usually
k, x
k, y
kRadius and centre coordinate for current iris external boundary.(x y) is original image to I.
The principle of the inventive method institute foundation is: generally, when carrying out iris image acquiring, for fear of lighting source imaging in the visual field disperse light source is adopted in the influence of iris image.But, if the position of ingenious arrangement dot matrix infrared light supply can make the inside of source imaging at pupil, simultaneously, suitably select when the radial position of light source is suitable, can make the picture of light source in pupil and iris tissue in the end photographic head adopt image definition maintenance one to.Therefore, the judgement for the definition of iris image just is converted into the judgement to light source image definition in the pupil.
Near image is in into the focal plane diverse location, because focusing, the picture of light source can take place fuzzy, spot size can change, shown in Fig. 5 a, Fig. 6 a.Image in the pupil scope is carried out binaryzation, and binaryzation result is shown in Fig. 5 b, Fig. 6 b.White portion is counted, just can be calculated the size of hot spot.
When iris tissue not when becoming focal plane, the hot spot scope is bigger, the white portion area is bigger after the binaryzation;
When iris tissue was positioned at into focal plane, the hot spot scope was less, and the white portion area is less after the binaryzation;
The iris image acquiring method that the inventive method adopts only comprises a pupil position fixing process and an image binaryzation counting process.Guaranteeing that operand is simplified greatly under the existing illumination, need not relate to complicated multiplication and division computing, be very suitable for the processor of low sides such as portable equipment, single-chip microcomputer, reduce the cost of device.The inventive method is insensitive for contact lens, still can keep accuracy.
Claims (1)
1, a kind of acquisition method of iris image is characterized in that this method comprises following each step:
(1) gathers several iris images in real time;
(2) several iris images of gathering are carried out iris inward flange location respectively, to determine pupil position, the localized method of wherein said iris inward flange comprises the steps:
(a) set a gray threshold, in each column direction of iris image, find out the sequence that gray value is lower than threshold value;
(b) select the longest sequence from above-mentioned sequence, then the center of the mid point of this sequence and pupil undetermined is in same horizontal line;
(c) pixel on the above-mentioned horizontal line is tested, rejected the pixel that gray value is higher than above-mentioned setting threshold, obtain the left and right border of pupil;
(3) set a gray threshold, each the pixel gray value and the threshold value that will be in the above-mentioned pupil scope compare, and the pixel that is higher than threshold value for gray value is counted, thereby obtain the ratio of the pixel number in this count value and the whole pupil scope;
(4) above-mentioned ratio is sorted from small to large in real time, n width of cloth iris image before selecting in the ranking results, select in this n width of cloth image the image that detects by iris feature at first, be final images acquired, the method that wherein said iris feature detects comprises the steps:
(a) for being positioned at all pixels in pupil center pixel place horizontal line left side, obtain their shade of gray curve, select be higher than a certain threshold value the local maximum point as candidate's left border point;
(b) for being positioned at all pixels in horizontal line right side, pupil center pixel place, obtain their shade of gray curve, select be higher than a certain threshold value the local maximum point as candidate's right side boundary point;
(c) from formation of above-mentioned candidate's left margin point and the formation of right margin point, choose a point respectively arbitrarily, form an iris external boundary by these two points;
(d) calculate the average gray of being had a few on the above-mentioned iris external boundary;
(e) calculate the partial differential value of above-mentioned average gray to current iris radius, the pairing iris boundary of maximum partial differential absolute value is the external boundary of iris undetermined;
(f) iris external boundary undetermined and known inner boundary are compared with the inside and outside boundary characteristic of experience iris, meet empirical model, promptly pass through feature detection.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110602980A (en) * | 2017-05-10 | 2019-12-20 | 波士顿科学医学有限公司 | Region of interest representation for electroanatomical mapping |
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| CN102521576A (en) * | 2011-12-16 | 2012-06-27 | 北京天诚盛业科技有限公司 | Iris location method |
| CN105550631B (en) * | 2015-08-25 | 2019-03-22 | 宇龙计算机通信科技(深圳)有限公司 | A kind of iris image acquiring method and device |
| CN110348840B (en) * | 2019-05-30 | 2020-06-30 | 北京昱达天丽科技发展有限公司 | Small-amount secret-free payment system improved by using biometric identification technology |
| CN110619272A (en) * | 2019-08-14 | 2019-12-27 | 中山市奥珀金属制品有限公司 | Iris image segmentation method |
| CN111178189B (en) * | 2019-12-17 | 2024-04-09 | 北京无线电计量测试研究所 | Network learning auxiliary method and system |
| CN112022641A (en) * | 2020-09-10 | 2020-12-04 | 深圳职业技术学院 | Method and system for assisting eye rotation movement |
| CN113099135B (en) * | 2021-02-24 | 2023-04-07 | 浙江大华技术股份有限公司 | Infrared image focusing, terminal device and computer readable storage medium |
| CN113264399A (en) * | 2021-04-26 | 2021-08-17 | 杭州创恒电子技术开发有限公司 | Footprint image acquisition equipment capable of automatically changing film and footprint image acquisition method |
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|---|---|---|---|---|
| US5953440A (en) * | 1997-12-02 | 1999-09-14 | Sensar, Inc. | Method of measuring the focus of close-up images of eyes |
| CN1282048A (en) * | 1999-07-22 | 2001-01-31 | 中国科学院自动化研究所 | Identity identifying method based on iris idendification and its equipment |
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Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5953440A (en) * | 1997-12-02 | 1999-09-14 | Sensar, Inc. | Method of measuring the focus of close-up images of eyes |
| CN1282048A (en) * | 1999-07-22 | 2001-01-31 | 中国科学院自动化研究所 | Identity identifying method based on iris idendification and its equipment |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110602980A (en) * | 2017-05-10 | 2019-12-20 | 波士顿科学医学有限公司 | Region of interest representation for electroanatomical mapping |
| CN110602980B (en) * | 2017-05-10 | 2022-06-28 | 波士顿科学医学有限公司 | Region of interest representation for electroanatomical mapping |
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