Homework 12

Homework 12 - OPTI-202R Assigned Due(Wednesday(Wednesday...

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OPTI-202R Homework No. 12 Leilei Peng Spring 2010 Assigned: 4/21/09 (Wednesday) Due: 4/28/09 (Wednesday) REMINDER : Final exam on May 7, 11:00-1:00 12-1 ) (40 points) An Epidiascope or Opaque Projector is used to project the words or images on a piece of paper onto a screen. It is similar to an overhead projector except that it is used for diffuse objects. a) Design an opaque projector: Paper: 8.5 x 11 inch Screen: 2 m x 2 m Distance to the screen: 3 m (from projection lens) b) Clearly the problem is going to be getting enough light onto the screen for practical viewing. For practical reasons, the projection lens is limited to a diameter of 8 inches. The desired screen luminance is 2.0 cd/ft 2 (candela/ft 2 ) for white areas on the paper. A candela (cd) has units of lm/sr. If each light bulb used to illuminate the paper produces an illuminance of 1000 foot-candles (lm/ft 2 ), how many light bulbs are needed? You may assume that the paper and the screen are both lambertian with a reflectivity of 1.
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Homework 12 - OPTI-202R Assigned Due(Wednesday(Wednesday...

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