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Ethnographic research
Theoretical framework for ethnographic research
Ethnographic research
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Chapter 2
Segmentation
2.1 OVERVIEW
The eye conatins two concentric cirles , the iris/sclera boundary and the iris/pupil boundary. The objective is to isolate the actual iris region from the rest of the image. The image may contan some
Noise and the same could be occuluded due to eye lashes and eyelids. So in this step we have to excude these interfrences corrupting the image and determine the circular iris region. The results may depend upon the quality of the image. The database used can have pecuilaiar corruptions for ex the LEI database contains specular reflections in all images and CASIA does not have it. This stage is very critical as any false representation of data at this stage will have cascading effect on the compete databse templates
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The same is fixed by roatting the image in a fixed direction and align both the templates at matching stage.
3.2 Implementation
Daugman’s rubber sheet model technique was adopted for normalization. Reference point is the centre of the pupil and radial vectors are assumed to pass from centre till the iris boundary. A number of feature points are selected on these vectors. The number of points on the radial line is called radial resolution and along the angular line is called angular resolution.
A remapping function is used to rescale the points on the angular lines. A fixed number of points is taken on each radial vector. The Cartesian coordinates form the normalized pattern are back tracked to get the radial and angular positions. The size of the rubber sheet was taken as 10 pixels on the radial vector and 40 on the angular vector.
3.3 Result
The Daugman’s rubber sheet model was successfully implemented and images normalized. However the process was not able to reconstruct the exact pattern in varying dilation levels of the pupil. The relational consistencies were not addressed at this stage, so various normalized samples looked misaligned. The issue is addressed in the matching
There are three parts to the eye exam, the visual acuity exam. This test uses an eye chart to measure how good you can see an object details or the shape of an object at a far distance. 20/20 is the perfect visual acuity and if you 're legally blind than its worse than or equal to 20/200 in both eyes. The second exam is called the slit lamp exam which is a type of microscope that is used to examine the front part of the eye,, that includes the eyelids, conjunctiva, sclera, cornea, iris, anterior chamber, the lens, and part of the retina and optic nerve. The third exam is called dilated exam. Dilated exam is when drops are placed in the eyes to widen or dilate the pupil to enable your eye M.D. to examine the retina and optic nerve for signs of damage (“Diabetic Retinopathy
The Steps are repeated until the centroid does not change beyond a limit. The limit must be set while
Retinal vessel segmentation is important for the diagnosis of numerous eye diseases and plays an important role in automatic retinal disease screening systems. Automatic segmentation of retinal vessels and characterization of morphological attributes such as width, length, tortuosity, branching pattern and angle are utilized for the diagnosis of different cardiovascular and ophthalmologic diseases. Manual segmentation of retinal blood vessels is a long and tedious task which also requires training and skill. It is commonly accepted by the medical community that automatic quantification of retinal vessels is the first step in the development of a computer-assisted diagnostic system for ophthalmic disorders. A large number of algorithms for retinal vasculature segmentation have been proposed. The algorithms can be classified as pattern recognition techniques, matched filtering, vessel tracking, mathematical morphology, multiscale approaches, and model based approaches. The first paper on retinal blood vessel segmentation appeared in 1989 by Chaudhuri et al. [21]...
Psychologist Raymond Dodge and his student T.S. Cline developed the first camera-based technique for registering eye movement in 1901 [3]. They used a falling plate camera (also referred to as a photo-chronograph) to measure light reflected from the cornea. However, their method required the subject’s head to be motionless and was only capable of recording horizontal eye movement. Only a few years later, motion picture photography was applied to record eye movement. This technique was useful because it allowed for a frame-by-frame analysis of the eye’s movement allowing for quantitative research on a solid basis**.
...omated detection of lines and points in the images and the use of smart markers in reference video recordings.
This is a representation of the eye's lens system. This eye has no eye condition, such as nearsightedness or farsightedness, and the lens is drawn in its relaxed position. The light rays are focused appropriately on the retina. The thickness of the cornea is 0.449 mm, the distance from the cornea to the lens is 2.
The eye consists of many parts. The part of the eye you can see when you look at someone consists of four parts. The colored part of the eye where the light enters is called the iris. The white part around the iris is the conjunctiva and episclera. This part also contains blood vessels. The cornea is the clear covering of the iris and pupil. The cornea contains no blood vessels. The lens is located behind the iris. The lens is used to focus, as in the cornea, but the lens can move. The retina is responsible for telling the brain what a person is seeing. They determine all the different parts of what is being seen. It then codes them to electrical signals for the brain (Cassel p 4-10).
From many points of views, it can be considered as the starting point. The team working with it has a dream to make more objects recognition which is context base. They also have a desire to make the recognition more interactive. A new and exceptional feature has been suggested where a particular part of an image can be tapped and the information can be heard.
2.“Idaho eye center”. Modern guides for eye care. ( Pocatello, Id.) 2002 3.Howard Bedrossian, M.D. “The Eye” A Clinical and Basic Science Book. (Blackwell scientific publications. LTD., Oxford, England.) 1958
the cornea and the sclera. The cornea is what covers the iris, and is the
Thirdly, the edge points must be well localized, that is, the distance between the edge pixels found by the detector and the actual edge must be minimum. And lastly, only one response must be there for a single edge. The standard convolution method is performed once the mask is calculated. Since the convolution mask is usually much smaller than the actual image, the mask slides over the image, manipulating the pixels in the image.
(KidsHealth.org, 2013) How does an eye work? Well the first thing that light passes through is the cornea. The cornea is a dome of clear tissue. The cornea’s job is to focus on the light as it passes through. The color part of the eye is the iris. The Iris is behind the cornea, and in
This approach includes two processes, training and classification (Chelali, Djeradi & Dejradi, 2009). In the training process, a subspace will be established by using the training samples, and then the training faces will be projected onto the same subspace. In the classification process, the input face image will be measured by Euclidean Distance to the subspace, and a decision will be made, either accept or reject.
...he cornea is deformed so that its surface is oval instead of spherical. Light rays are distorted at the entrance of the eye. This produces a blurred image and is known as astigmatism. To correct it, glasses are given a nonspherical or cylindrical curvature. Cross-eyes and walleyes are produced when both eyes do not work together because of weakness of the eye muscles.