Sunday, January 26, 2020

Defining And Understanding Holography Physics Essay

Defining And Understanding Holography Physics Essay Holography,  method  of  obtaining three-dimensional photographic images. These images are obtained without a lens, so the method is also called lensless photography. The records are called holograms (Greek holos, whole; gram, message). The theoretical principles of holography were developed by the British physicist Dennis Gabor in 1947. The first actual production of holograms took place in the early 1960s, when the laser became available. By the late 1980s the production of true-color holograms was possible, as well as holograms ranging from the microwave to the X-ray region of the spectrum. Ultrasonic holograms were also being made, using sound waves. Holography  is one of the remarkable achievements of a modern science and technology. Holograms have unique property to restore the high-grade volumetric image of real subjects. The word holography originated from the Greek words holos whole and grapho write, that means complete record of the image. Holography represents photographic process in a broad sense of this word, essentially differs from a usual photo because there is a registration not only  intensity  in a photosensitive material, but also  phase  of light waves, scattered by the object and carried the complete information about three-dimensional structure of the object. As the medium of mapping of the reality, hologram has unique property: unlike usual photo, the  holographic image  can reproduce exactly three-dimensional copy of the original object. Such image with set of views, varied with change of supervision, has amazing realness and often looks like the real object. Unlike photography or painting, holography can render an object with complete dimensional fidelity. A hologram can create everything your eyes see size, shape, texture and relative position. However, if you try to touch a holographic image, all youll find is focused light. History of holography Holography is known from 1947 when British (native of Hungary) scientist Dennis Gabor   produced the theory of holography while he was trying to improve the resolution of electron microscope .Gabor coined the term which we know today i.e. holography by the greek word holos, which means whole while gramma means message. Further development in the field was during the next period because light sources available at that time was not truly coherent . This problem was overcome in  1960  by Russian scientists  N. Bassov  and  A. Prokhorov  and American scientist  Charles Townswith by the invention of the laser, whose pure, intense light was ideal for making holograms. In that year the pulsed-ruby laser was developed by Dr.  T.H. Maimam. This laser system  (unlike the continuous wave laser normally used in holography) emits a very powerful burst of light that lasts only a few nanoseconds (a billionth of a second). It effectively freezes movement and makes it possible to produce holograms of high-speed events, such as a bullet in flight, and of living subjects. The first hologram of a person was made in  1967, paving the way for a specialized application of holography: pulsed holographic portraiture. In  1962  Emmett Leith and Juris Upatnieks of the University of Michigan recognized from their work in side-reading radar that holography could be used as a 3-D visual medium. In 1962 they read Gabors paper and simply out of curiosity decided to duplicate Gabors technique using the laser and an  off-axis technique  borrowed from their work in the development of side-reading radar. The result was the first laser transmission  hologram of 3-D objects (a toy train and bird). These transmission holograms produced images with clarity and realistic depth but required laser light to view the holographic image. Their pioneering work led to standardization of the equipment used to make holograms. Today, thousands of laboratories and studios possess the necessary equipment: a continuous wave laser, optical devices (lens, mirrors and beam splitters) for directing laser light, a film holder and an isolation table on which exposures are made. Stability is absolutely essential because movement as small as a quarter wave- length of light during exposures of a few minutes or even seconds can completely spoil a hologram. The basic off-axis technique that Leith and Upatnieks developed is still the staple of holographic methodology. Also in  1962  Dr.  Yuri N. Denisyuk  from Russia combined holography with 1908 Nobel Laureate Gabriel Lippmanns work in natural color photography.  Denisyuks approach  produced a white-light reflection hologram which, for the first time, could be viewed in light from an ordinary incandescent light bulb. Another major advance in display holography occurred in  1968when Dr.  Stephen A. Benton  invented white-light transmission holography while researching holographic television at Polaroid Research Laboratories. This type of hologram can be viewed in ordinary white light creating a rainbow image from the seven colors which make up white light. The depth and brilliance of the image and its rainbow spectrum soon attracted artists who adapted this technique to their work and brought holography further into public awareness. Bentons invention is particularly significant because it made possible mass production of holograms using an embossing technique. These holograms are printed by stamping the interference pattern onto plastic. The resulting hologram can be duplicated millions of timesfor a few cents apiece. Consequently, embossed holograms are now being used by the publishing, advertising, and banking industries. In  1972  Lloyd Cross  developed the integral hologram by combining white-light transmission holography with conventional cinematography to produce moving 3-dimensional images. Sequential frames of 2-D motion-picture footage of a rotating subject are recorded on holographic film. When viewed, the composite images are synthesized by the human brain as a 3-D image. In 70s Victor Komar and his colleagues at the All-Union Cinema and Photographic Research Institute (NIFKI) in Russia, developed a prototype for a projected holographic movie. Images were recorded with a pulsed holographic camera. The developed film was projected onto a holographic screen that focused the dimensional image out to several points in the audience. Holographic artists have greatly increased their technical knowledge of the discipline and now contribute to the technology as well as the creative process. The art form has become international, with major exhibitions being held throughout the world. The commonly and widely used way of imaging of the reality is the photography. A photograph is basically the recording of the differing intensities of the light reflected by the object  and imaged by a lens. However, information about dimensions of the object contained not only in amplitude (intensity), but also in a phase of light waves. A great difference between holography and photography is the information recorded. This difference is why photographs are two dimensional (2-D) images while holograms are three dimensional (3-D) images. Photographs contain only one view point of an object. Our eyes need a minimum of two view points in order to see depth. Vision using two viewpoints of an object is called stereoscopic vision. Each eye receives a slightly different view point of an object, our brain combines the two and we perceive depth. We can fool our eyes into seeing photographs in three dimensions by taking two slightly different views of an object and allowing each eye to see only one image, the right image for the right eye and the left image for the left eye. We can do this with a stereoscope (for pictures) or with polarized glasses (for movies). The shortcoming of stereoscopic images is that when we move our head from side to side or up and down, we still only see the same two view points, whereas we should be seeing continuously changing viewpoints of the object. The image therefore doesnt quite appear to be three dimensional. In order to make a record of a three dimensional object we need to record this continuous set of viewpoints of the object. Estimating sizes of the objects and considering shape  and direction of shadows from these objects, we can create in our mind general representation about volumetric properties of the scene, represented in a photo. But, if sizes of the objects are identical and there are no shadows, volumetric content of the photographed scene is completely lost. For example, we can not define in the photo of snowflakes on a dark background, which of them is closer, and which of them is farther. Holography is the only visual recording medium that can record our three-dimensional world on a two-dimensional recording medium and playback the original object or scene to the unaided eyes as a three dimensional image. The image demonstrates complete parallax and depth-of-field and floats in space either behind, in front of, or straddling the recording medium.

Saturday, January 18, 2020

How far do you agree with Dr Johnson Essay

Samuel Johnson, or Dr Johnson as he was sometimes referred as, was a great English author who made enduring contributions to English literature. Being such a distinguished and renowned author, his views on literature were and still are today, stern and well-known. However, I have views both agreeing with and opposing Dr Johnson’s view that Milton’s work lacks human interest. Firstly, human interest strictly speaking, is about everyday people just like us, being able to relate to a story, and possibly learn something from it and put it into practise in our own lives. The epic poem Paradise Lost concerns the Christian story of the Fall of Man, while dealing with more present topics such a marriage and politics. Milton’s purpose, as stated in book I, is to â€Å"justify the ways of God to men. † This is a good base to start my argument on, which is that I do not agree with Dr Johnson, and believe that Milton’s work does hold human interest. By involving politics and marriage into his works, this is surely of human interest, as people will be curious and inquisitive about how things worked back then, and it is therefore of human interest if people want to learn about it. Milton states the purpose of his epic poem, and it is obvious that he intended Paradise Lost to educate people about God. If anything, Paradise Lost holds universal human interest. The event in the poem concern the whole of the human race, as the single event of disobeying God and plucking a single apple has moulded the destiny of the world, and it should surely be of interest to anyone who is born into this world. People must be, and generally are, curious about how their world evolved and how it reached the state of where it is now. If people are curious about this and eager to be educated on this topic, then they may read Milton’s work to learn about these events, and consequently are showing signs of human interest. Looking more in depth into Christianity, Christians believe that due to the event of Eve picking the apple, all humans are born with sin, and it is whether people choose to act on it or not that defines us. However, a big factor to consider is whether people actually believe in God or not. Atheists wouldn’t take any notice of this argument, let alone and interest of Milton’s epic poem Paradise Lost. This is my argument agreeing with Dr Johnson and saying that Milton’s work does lack human interest. To an atheist, they would take absolutely no interest in the Fall of Man, and wouldn’t believe anything about God and heaven. Also being literal about it, for anyone, let alone an atheist, it is hard to relate to an event that happened such a long time ago, and we only know to be true from a book and lots of believers. How do we even know that this happened? How do we even know God exists? These are all questions that are very important when answering this question. Many different theological issues are presented in the epic poem, such as fate, the introduction of sin and death into the world, as well as the nature of angels, heaven, hell and Satan. However, sin and death cannot be ignored, even by atheists, as these two issues are both around us and will happen to us in our lives. So, this means that people are able to relate to these issues in Milton’s works, and therefore showing signs of human interest. Also, nowadays, we are not scared of disobeying something that will have as huge of a consequence as picking the apple did. Anything that we do today is not going to have an huge impact on the world, affecting all of its inhabitants and the world itself. So, in this sense, it is hard to relate to Milton’s work, and it can be said that it does lack human interest. Another literal relation that we can have with Paradise Lost is the consequences of picking the fruit relating to God, not just the event itself. Not only did God show his mercy and temperance in their punishments, but he also displayed his love and compassion through the Son, Jesus Christ. Atheist or not, everyone learns about Christ and the Fall and it is whether you chose to believe it or not which is what makes people an atheist. In this sense, Paradise Lost does not lack human interest as it can always be related to and people are always taught about it, even if it was in the classroom and compulsory, or by their parents. The knowledge of Jesus Christ and the garden of Eden is general knowledge, and therefore must be of human interest. Also, the hard work that men and women have to endure, and the pain of giving birth for a woman are all consequences of Eve picking the apple off the tree and disobeying God’s only rule. And therefore, as we all experience hard work, and the majority of women experience child birth, we can all relate to this in some way or another. So, having analysed and read through this epic poem, I am going to disagree with Dr Johnson that Milton’s work lacks human interest. I think that everyone can relate to Milton’s work in one way or another. You could say, that if you were not able to relate to his work, then you havent related to the story of Creation and havent learnt about God or Christ. Also, you do not need to believe in all of the Creation stories and the Garden of Eden to have related to Milton’s work. Above all, Milton is a fantastically talented writer, and that alone is a reason as to why Milton’s work does contain human interest. Bibliography and Webography: The Bible The Complete English Poems – John Milton www. wikepedia. org www. sparknotes. com.

Friday, January 10, 2020

Personal and Imaginative – Scarred for Life

This was it. My legs were lead; my head throbbed violently. It felt as if the energy within me had slowly oozed away. I dragged my feet like I was being held down by iron chains. Gathering every ounce of my might, I heaved myself towards the bench- and collapsed upon it. Where was I? No clue. That was all I'd been saying to myself since the taxi left. And how long ago was that? Two hours†¦three hours†¦four hours? Still no clue. I hated myself for being so thick. If it wasn't for my ‘thick' brain, I would have been home by now. Home. I felt useless. â€Å"What the hell you doin' ere?† I looked up so fast it made my neck click; my anger rose. It was a brown haired boy who I guessed was trying to pass the time. I found him annoying. I wasn't in the mood of talking to anyone-I hardly ever was. â€Å"You tell me.† I replied stiffly. â€Å"Ain't seen you around this place.† I felt like punching him. I hated this about some people, butting in when they were least wanted. â€Å"That's 'cause I ain't from dis place.† I grumbled, glancing at him, thinking how much longer is he going to stay? There was a pause. Then, just as soon as I expected him to leave, he demanded, â€Å"Where you from then?† â€Å"Look yeh, I don't know you an' I ain't in da mood. So move.† I stated through gritted teeth, giving him the dirtiest look I could muster. He finally got the message and went off, gruffly. I didn't understand myself; I never used to be like this. My mood switched within seconds and I knew that many people found it hard around me. Even my own mates kept their distance from me at times. But they understood that I had a past. Life had changed a lot for me, and since that change, I was never the same person. I cast my eyes around, taking in my surroundings. Even though the street lamps were alight, the road seemed unusually dark. I squinted and could just make out the scenes of every day life before me. Here and there figures would move about; some closing their shops, others walking hastily, making their way home. I gazed blankly at the movements, not bothering to move from my seat. Eventually, the very last of the people edged away towards the end of the street, their silhouettes disappearing from under the very last street lamp. Silence followed. Almost radically, a harsh wind had begun to bluster, causing my numb face to sting. Fed up with my position, I pulled up my hood, got up from the rigid bench and stepped on to the road. The sound of my trainers hitting against the pavement seemed to echo into the night, leaving behind a lethal dead-like silence like that of graveyard. Trying to block out this atmosphere, I began to recount the event that occurred on the taxi†¦ I couldn't believe my stupidity. Losing my mobile was one thing- but losing my purse-on the same day†¦a bit extreme huh? And to make matters worse, being the idiot that I am, I tried to get home in a taxi when I was totally broke! The reaction the driver had when he realised I wasn't going pay was severe to say the least. I knew people had strange solutions but leaving me in the middle of God-knows-where was a bit too strange. Sad or what? Well, what was done was done and I knew there was no way in changing it. Thinking about it wasn't going to get me anywhere. My main priority was to see how to get home. I inhaled deeply as the bleak air rushed in to my blood. What was the point in living when surviving was so hard? Upon reaching the end of the street, I became aware of the bend which had not been visible to me from the bench. It was murky and even at this distance I could not make out what lay on its other side. As I began to make my way through it, my stomach gave a discomforting squirm. I didn't know why that was? Was it the darkness that had just fallen over me? Or the strengthening of the silence which had now reached its peak? Being able to distinguish traces of a light, I became relieved to know that I had entered just another street. This time there were no shops, but instead stood half a dozen or so houses, which I could tell were grand as well as ancient. They were positioned with a great deal of space and on either side of the road which lay in front of me. At the far end, I could discriminate the park which stood out due to its rusty iron gate. As my vision became clearer, I noticed a dark profile standing within the shadow of the great oak tree. Who would be out at this time of night? Or was it a trick of light? Sensing movement, I knew for sure that it wasn't just a fragment of my imagination. My heart began to beat loudly, vibrating heavily in my throat. Now I knew I wasn't alone. It ambled out from under the tree; light shining upon its limp body. Slowly, it began dragging its body in an oddly held manner. It – he was hurt. A slow moaning uttered from his mouth, and my fear turned into grief on seeing the pain radiating from him. On realising that his direction was headed my way, I heaved my body behind the nearest bush, afraid of being seen. From his gnawed, wrinkly hands, I realised he was well aged. His face was entirely hidden, due to the hood of his festering coat. He had now reached a house opposite me, one which I had not noticed due to its miniscule size. It was dilapidated and it showed no sign of warmth. Was this his house? I heard keys dropping, breaking the silence, and watched as he bent to pick them up. As he did so, his hood fell from his face. I screamed†¦ Everything was indistinct, the face flashed in front of me again, yet this time it looked younger by a few years. I could hear loud terrible screaming from within my own head. So loud that I thought that my head would explode. The screaming went on, never ending. The pain searing in the shrill cries was too much to take in. The screaming didn't come from the face, yet I recognised it. But it couldn't be! I tried to cry for help but nothing came out. Slowly, the picture blurred and my vision became focused†¦ My inhalation was hard, my heart aching endlessly. I tried to hold my breath, trembling from head to toe. Cold sweat trickled down my face and my clothes were soaked, clinging to my skin. How much time had passed? A door slammed shut, its reverberation hanging in the atmosphere. I turned my head towards the house- had the man just gone in? It had been ten years. Ten long, painful years since I had heard my brother's voice, shrieking with agonising pain just the same as on that night. The night that I last saw him alive. Was it just a coincidence that I had just seen the convict? All I remembered was the assassin's terribly scarred face, which had appeared there on the day my brother had fought eagerly for his life, aiming viciously at his face. This man was marked – scarred for life. Since then, I had promised myself to find the man who had finished my little brother off- and now that I had found him, there was no way I was going to let him escape. Not this time. No way†¦

Thursday, January 2, 2020

How Big Are Millions, Billions, and Trillions

The Piraha tribe is a group living in the jungles of South America. They are well known because they do not have a way to count past two. Studies have shown that tribe members cannot tell the difference between a pile of eight rocks and 12 rocks. They have no number words to distinguish between these two numbers. Anything more than two is a â€Å"big† number. Most of us are similar to the Piraha tribe. We may be able to count past two, but there comes a point where we lose our grasp of numbers. When the numbers get big enough, intuition is gone and all we can say is that a number is really big. In English, the words million and billion differ by only one letter, yet that letter means that one of the words signifies something that is a thousand times larger than the other. Do we really know how big these numbers are? The trick to thinking about large numbers is to relate them to something that is meaningful. How big is a trillion? Unless we’ve thought of some concrete ways to picture this number in relation to a billion, all that we can say is, A billion is big and a trillion is even bigger. Millions First consider a million: One million is a thousand thousands.One million is a 1 with six zeros after it, denoted by 1,000,000.One million seconds is about 11 and a half days.One million pennies stacked on top of each other would make a tower nearly a mile high.If you earn $45,000 a year, it would take 22 years to amass a fortune of one million dollars.One million ants would weigh a little over six pounds.One million dollars divided evenly among the U.S. population would mean everyone in the United States would receive about one third of one cent. Billions Next up is one billion: One billion is a thousand millions.One billion is a 1 with nine zeros after it, denoted by 1,000,000,000.One billion seconds is about 31 and a half years.One billion pennies stacked on top of each other would make a tower almost 870 miles high.If you earn $45,000 a year, it would take 22,000 years to amass a fortune of one billion dollars.One billion ants would weight over 3 tons — a little less than the weight of an elephant.One billion dollars divided equally among the U.S. population would mean that everyone in the United States would receive about $3.33. Trillions After this is a trillion: One trillion is a thousand billions, or equivalently a million millions.It is a 1 with twelve zeros after it, denoted by 1,000,000,000,000.One trillion seconds is over 31 thousand years.One trillion pennies stacked on top of each other would make a tower about 870,000 miles high — the same distance obtained by going to the moon, back to Earth, then to the moon again.One trillion ants would weigh over 3,000 tons.One trillion dollars divided evenly among the U.S. population would mean that everyone in the United States would receive a little over $3,000. What’s Next? Numbers higher than a trillion are not talked about as frequently, but there are names for these numbers. More important than the names is knowing how to think about large numbers. To be a well informed member of society, we really should be able to know how big numbers like a billion and trillion really are. It helps to make this identification personal. Have fun coming up with your own concrete ways to talk about the magnitude of these numbers.