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Although barcodes can be used to manage data conveniently, they cannot be applied to small areas. Therefore, pointcodes are used to overcome the issue in this article. A pointcode uses a pointcode pattern to encode data and uses a pointcode image to decode data. A pointcode pattern is composed of many grating dots with different specified grating pitches and grating orientations. Moreover, there are two grating-dot sizes generated. When a laser beam illuminates a pointcode pattern with correct illuminating conditions, a pointcode image corresponding to the hidden data is diffractively reconstructed. A pointcode image is composed of many bright points with different positions. There are two possible bright-point sizes generated. A bright point or two bright points at specified positions are used to denote a number. Small pointcode patterns are enough to diffractively form pointcode images. [c] 2009 Optical Society of America OCIS codes: 210.0210, 210.1635, 050.1950.

A new type of diffusion pattern is proposed. The proposed patterns are composed of 2D diffusion dots. The diffusion dots are created on a photoresist plate by recording the image of a local area of a piece of ground glass dot by dot. An imaging lens covered by a mask with a slit aperture is used to form the image. By changing the orientation of the slit aperture on the mask plane, the diffusion dots can have different microintensity distributions for the same incident light beam. Therefore the diffusion dots created by the same slit aperture orientation show the same brightness, and the diffusion dots created by different slit orientations show different brightness for the same illuminating and viewing conditions. Thus a proposed diffusion pattern can show dynamic images by changing its illuminating or viewing directions. By applying the double-exposure technique to the diffusion dots of a pattern, the pattern not only can show dynamic effects but also can possess several hidden features for identifying the pattern. Therefore the proposed patterns are dynamic and anticounterfeiting. OCIS codes: 110.6150, 290.1990.

The images on a dot-matrix hologram contain many two-dimensional (2D) dots with different grating orientations and different grating pitches. Because the zeroth-order light nondiffracted by different grating structures has the same progress direction, the nondiffracted light can be diffracted to a 2D spot spectrum by the 2D dot structure. The 2D spot spectrum depends on grating depths and dot sizes. Although ordinary noises are troublesome for 2D spots, noises caused by special dot arrangement defects or special grating moire fringes are useful in checking holograms. Since the features of grating depths, dot sizes, dot arrangement defects, and grating moire fringes can be randomly changed on a case by case basis, 2D spot spectra in different cases are different. The aforementioned random features are used to identify dot-matrix holograms. OCIS codes: 090.1760, 120.4630.