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Optical Disc manufacturing

Optical discs are made using replication. This process can be used with all disc types. Recordable discs have pre-recorded vital information, like manufacturer, disc type, maximum speeds, etc. In replication, a cleanroom with yellow light is necessary to protect light sensitive materials and to prevent dust from corrupting the data on the disc. A glass master is used in replication. The master is placed in a machine that cleans it as much as possible using a rotating brush and deionized water, preparing it for the next step. In the next step, a surface analyzer inspects the cleanliness of the master before photoresist is applied on the master. The photoresist is baked in an oven to solidify it. Then, in the exposure process, the master is placed in a turntable where a laser selectively exposes the resist to light. At the same time, a developer and deionized water are applied to the disc to remove the exposed resist. This process forms the pits and lands that represent the data on the...
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History

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This article possibly contains original research . Please improve it by verifying the claims made and adding inline citations. Statements consisting only of original research should be removed. ( July 2009 ) (Learn how and when to remove this template message) The first recorded historical use of an optical disc was in 1884 when Alexander Graham Bell, Chichester Bell and Charles Sumner Tainter recorded sound on a glass disc using a beam of light. Optophonie is a very early (1931) example of a recording device using light for both recording and playing back sound signals on a transparent photograph. An early optical disc system existed in 1935, named Lichttonorgel. citation needed An early analog optical disc used for video recording was invented by David Paul Gregg in 1958 and patented in the US in 1961 and 1969. This form of optical disc was a very early form of the DVD ( U.S. Patent 3,430,966 ). It is of special interest that U.S. Patent 4,893,297 , filed 1989, issued 1990, gene...
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25)Described: What to expect on Republic Morning 2021and what not to

India Republic Day -- Republic Day 2021: In 2020it was the agitation up against the Citizenship Amendment Act (CAA). Nowthousands of farmersmainly from Punjab and Haryanahave been camping at the region of Delhi for more than 8 weeksdemanding the Centre repeal the three farm laws. To the second year in a stripRepublic Day celebrations from the national capital will be placed under the shadow of impetuous protests against laws transferred by the Centre. In 2020it was the agitation up against the Citizenship Amendment Act (CAA). This timethousands of farmersmainly from Punjab and Haryanahave been camping at the region of Delhi for more than 8 weeksdemanding the Centre repeal the three farm laws. This years Republic Day march will also be the first major public event in pandemic times. What is new this year The presentation will be pared down the number of spectatorsthe size of marching contingents and other side interesting attractions. The spectator size has become reduced to 25000 fr...
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