Reflected Light Imaging - Essay Example

A report on Reflecting Imaging Table of Contents 3 Introduction 3 Literature Review 4 Imaging 4 2D imaging 6 3D imaging 6 Camera components 6 Digital and analogue image 7 Eye component and light 8 Capture 8 Digitization of analogue image 9 Display 9 Conclusion 10 Bibliography 11 Reflected Light Imaging Abstract Reflected light imaging is one of the ways a person can create an image. Formation of these images is only possible due law that electromagnetic radiations including light follow. Image production can lead to formation of 2D images and 3D images that each has its advantages. The most common type of images is 2D images due to its early invention. The 3D images are still in development stages but radiations like x-rays produce this kind of image used in hospitals for disease analysis. The technique used in the article includes strict analysing of the literature related to the topic of discussion. Cameras form the central part in understanding the image formation processes. The analogue forms the start of modern imagery with components remaining the same over the years. The principle of using reflected light from the object still forms the integral part in image formation. Some cameras such as those used at night in infrared radiation detection are one of the few types that do not use the same principle of reflection target object. Significant similarity between human eyes and digital cameras is very clear. Capturing, storage and display of the images has improved overtime with current images store in data form and displayed on the camera.in the article, an explanation of digitisation and the processes involved such as quantisation and sampling has remained elaborated. The article further explains terms and problems associated with this digitisation. Introduction Imaging is a form of visual representation of an object or reproduction of the same visual object. Reflection is the property of waves changing direction by bouncing off the surface of object as they cannot pass through or get absorbed. The bouncing of light is the most common and it is important in image formation even to human eyes. Reflected light imaging is the process of forming images when electro-optical waves bounce from the target to the camera or recording device. However, transmission imaging involves waves passing through the object before reaching the camera or recording device. In this imaging technique, the images produced depend on the absorption and reflective properties of the object at the specific wavelength of the incident light. Classification of images leads to an image being a digital or analogue image based their properties. Digital image relates to visual illustration of an object in an electronic form that can remains manipulated and stored by electronic devices, which are 2D image I[r, c]. These kinds of images are tangible but have possibility of producing tangible ones through processing. Digital images are different from analogue, as they cannot have any meaning without software and hardware. Literature Review Reflected light imaging requires natural systems such as eyes to sophisticated manufactured systems like digital camera. The basis of these systems remains the same with some slight variations explained in the paper. Further development in improvement of the digital systems has made imaging easier. Imaging Light rays always obey the rule of reflection in which the incident angle equals the reflection angle. Objects reflect the light wavelength they do not absorb or allow to pass through them. Black objects absorb all light while white objects reflect all the light that strikes them. Object with other colours reflect lights with wavelength corresponding to the colour appearing on the image formed. In normal 3D scene objects, reflect light in all direction due to the rugged surface (Reinhard, 2010, p. 546)3. There are at least two types of imaging techniques involved in reflected light imaging. These techniques include 2D imaging and 3D imaging techniques. Both techniques use the principle of light from a different source especially the sun reflected by the object forming image and the background. Image formation is because the light waves obey the rule of electromagnetic radiations in reflection and travelling in straight line. In imaging, the object represented in the image is usually in scene that is 3D. The image reflect pass through a straight line to the eyes or sensor of the camera. In the human eye, light passes through lens and pupil and to the retina where photosensitive cells pick the signals and relay it to the brain. The presence of lens in human eye that is adjustable depending on distance of the object from the viewer enables focusing. In cameras, the light travels in a straight line and passes through the lenses and aperture. The passage through aperture and pupil, which are small, allow for formation of fine image without blurred parts. The lenses in the cameras allow the device to focus on the object. Formation of the image is on a planar surface giving 2D images. During the process of imaging, depending on the device, displaying of the object image may be through digital display or by direct viewing through the lenses. A digital display is surface that offer electronic display of images through screens. The images may be stored or direct from the object. In digital cameras, focusing of the light by lenses on the sensor after passing through the aperture. The lenses used in camera and the eyes are both convex with varying focal length. The sensor then converts the light into electrical energy depending on the amount of light from the object. The electrical energy generated pass through measurement that shows its proportionality to incident rays energy. Reflectance function of the object in this case refers to the dependency of the brightness of the image formed to the incident ray and determines human perception on colour texture. Reflected light imaging is also important in light microscopy used in biological research. Natural source of light or one from a bulb in the microscope bounce from the mirror to the specimen. In analogue cameras, the images formation is in the same way but instead of sensor that converts light to electrical charge, the light reacts with photosensitive chemicals on the film to create the image. The image created depends on the colour and intensity of light from the object. In this type of cameras, shutter is vital in keeping the film unaffected before capturing the image. 2D imaging This is the kind of presentation where an image formed has two algorithms on a planar surface. The image formed depends on the reflected light intensity. These are the most common type of images in normal daily lives. The form analogue images and large part of digital images. However, human eyes have a complex perception of the images by psychological converting even 2D images into 3D images in their mind. This is as result of relating the image to the real world. 3D imaging In reflected light imaging, generation of 3D images is only possible to human eye through placing of mirrors that reflect the image of the object from three dimensions. The image viewed gives the surrounding scene in all direction to the floating object. Although the 3D imaging remains more advanced than 2D, it does not always provide the best images. The images in 3D remains more blurred in production process compared to 2D images. 3D imaging is also common in hospital for checking patients’ status but this kind uses x-rays that pass through the body. Camera components A camera consists of many components that work together in producing the image needed. While capturing an image a person considers the lens focal length and field of view. The digital camera varies slightly from the analogue camera in capturing image and display system. Both types of camera require direct or reflected light from the object in image formation. All the cameras contain convex lenses that focus the light to planar surface forming the image. Most convex lenses have are compound and have more than two refracting surfaces. The analogue camera must have a shutter to keep the 33mm photosensitive film in the dark. Digital cameras on the other hand do not necessarily require a shutter to keep the detector in dark. Both cameras have apertures that regulate amount of light passing to the image detector or photosensitive film. The main difference in these types of cameras is in the photon detecting components. In the analogue camera, a photosensitive film forms an image immediately illumination strikes it. The digital camera on the hand uses couple-charged device as a sensor that has cells (Shapiro and Stockman, 2001, p. 1)4. Each cell changes the light received to electrical energy relayed to the image plane that act as image memory. An illustration showing internal parts of a digital camera. Figure 1 Digital and analogue image Production of both the images is in two dimensions with difference being that digital image is in form of electronic data while analogue image is not. a digital image are stored in electronic data form that are only retrievable by use of software. Analogue images are usually inform of negative or hard copy picture that do not require special software to retrieve or view. Conversion of analogue to digital image involve digitization that has two processes which include sampling and quantization. A digital image may just be as good as natural scenes if the resolution of the image presented is high with correct colouring and light intensity. At the same time image size should be proportionally equal to human eyes. Eye component and light The eye is a natural camera that has incredible abilities. The conical lens is convex in shape and refracts the light before passing the pupil with focal length of around 20mm (Acharya and Suri, 2008, p. 148)1. The lens width are adjustable in thickness according to distance of the object of focus changing refraction angles. The pupil acts as an aperture that is adjustable to allow only required amount of light to form the image. Retina at the back forms the image plane where the cons and rods are located to transmit impulse to the brain. The rods and cons are equivalent to sensor in digital camera and photosensitive film in analogue camera. The image formed at the image plane on retina is upside down but the brain interprets it to be upright. Figure 2 Capture During the capturing of image, a person carries out various adjustments to allow capturing of better images. In analogue cameras, a person manually adjusts of the focal length of the lenses to give the best image capture. In digital cameras, however the camera has automatic adjustment systems to focus the object properly. The mode of image formation differs between the analogues from digital camera in the sensors. The electrical energy from the CCD cells leads to formation of an electronic image. The advent of digital cameras has also come with new ways of image storage after capturing. Storing images takes place in various data forms that are accessible through software in the cameras and computers. Transfer of these images has become even easier with some transferred over electromagnetic waves. Transfer between devices may require a cable or localised wireless network. Digitization of analogue image The processes of digitization of analogue images involve two processes that include sampling and quantisation (Bowdoin, 2015, p. 1)2. The operations involve discretisation different domain quantity. Sampling involves discretisation of the space with domain function.  : [1,…,N] × [1,…,M] →Rm Figure 3 In image sampling, approximation of the two-dimensional algorithm is normally through equally spaced sample with assumption that the samples placed in N ×M array. Rate of sampling also known as pixel clock of the digitiser affect the spatial resolution of the digitized image. Pixel in 3D images known as volex derived volumetric pixel. Larger values of N and M mean finer sampling and continuous image approximation. Quantisation on the other hand refers to the intensity values discretization also referred as magnitude the sampled image. Intensity values denotes to the continuous values of image brightness and its digital equivalent. For human perception of the digitized image, the quantisation level needs to be high with detailed fine shading. False contours form a great problem in digitisation. It arises due to low level of brightness distinguishable by human eyes, avoidable by intensity of 100 to the lower side (Parts, 2015, p. 1)5. Display The digital display may show an image or video. Digital displays are in different forms including liquid crystal display and light-emitting diode display. These display systems are present in the digital image capturing objects such as cameras, laptops and phones and found in screens attached to desktops. Improvement of the display systems include introduction of semi 3D display systems and cylindrical display system to show 3-dimensional objects. Conclusion Reflected light imaging is a common representation of the analogue world scene. There has been improvement over time in image formation system. Introduction of the digital cameras with digital display screen enables real-time viewing of the images formed. Furthermore, the digital system enables manipulation of images easily compared to analogue system. In all improvements, the image formation in the eyes still has great similarity to all the devices. Light properties form the central part in ability of any device to form an image with principle remaining the same for all image-forming devices. Techniques such as digitisation use sampling and quantisation properties to change analogue images to digital images. Bibliography 1. Acharya, R., Ng, E. Y. K., & Suri, J. S. (2008). Image Modeling of the Human Eye. Norwood: Artech House. 2. Bowdoin. 2015. Definition of a Digital Image. Web. March 9, 2015. Retrieved from http://www.bowdoin.edu/dam/digimage/index.shtml 3. Reinhard, E. (2010). High dynamic range imaging acquisition, display, and image-based lighting. Burlington, MA, Morgan Kaufmann/Elsevier. 4. Shapiro, Linda G., Stockman, George C. 2001. Chapter 2: Imaging and Image. In. Computer Vision. Upper Saddle River, New Jersey: Prentice Hall 5. University of Patras (UPatras). 2015. Image Sampling & Quantisation. Web. March 9, 2015. Retrieved from http://bme.med.upatras.gr/improc/image_sampling.htm Read More