• Korean Journal of Optics and Photonics
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• v.18 no.3
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• pp.202-207
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• 2007

Optical visual cryptography (OVC) based on binary computer generated holograms (BCGH) is proposed. OVC used optics instead of human eyesight for decryption of visual cryptography (VC). As a result, it was possible to adapt cryptography to an optical system. However, it also had some difficulties because it did not overcome the existing problems of VC completely. This paper suggests a method of optical cryptography implementation based on the phase modulation characteristics of a liquid crystal display (LCD). The problems are evaluated by simulation. This system shows that the noise is reduced and resolution is improved compared with the conventional OVC.

• Journal of the Korea Computer Graphics Society
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• v.25 no.3
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• pp.31-41
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• 2019

A fog screen consists of tiny water drops and the viewers see the image transmitted through the fog screen. In contrast to ordinary screens, the viewers can see the actors passing through the image on the fog screen on stage. In this paper, we describe methods to build a top-down fog screen where fog particles generated in top space fall by gravity forming a flat vertical screen. We use a fog generation technique in which fog particles come out of the water surface when ultrasound vibrators immersed in water tank vibrate. We describe how fog particles form a flat screen while coming out of the fog passage tunnel, by generating guiding winds beside the fog screen. This technique utilizes the principle that fog particles are generated on the surface of a water tank by an ultrasonic vibrator placed in a water tank. The technique of forming a guiding wind on both sides of the passage exit where the fog comes out and the design and manufacturing method of the fog screen generating device are described so that the generated fog group can maintain one plane.