Digital 3D optical variable image making process and laser photocomposition system

Abstract

According to the orientation and spatial frequency of unit grating the image of decomposed into at least two subimages, the orientation and spatial frequency of unit grating of every subimage are identical, one subimage is inputted on the space light modulator, a parallel light beam is passed through the space light modulator and imaged on beam splitting element to produce split beam, and collected on the recording material to produce the image which is correspondeng to the described subimage and is formed from several diffraction grating, so that the different subimages are inputted into space light modulator in turn until the whole image is made. Its laser photocomposition system includes optical path system formed from parallel light source, space light modulator, imaging system and beam-splitting element, working tablet for placing recording material and control portion, the beam-splitting is positioned on the turnplate, and the recording material is positioned on the focal surface of imaging system.

Description

technical field [0001] The invention relates to a method for making digital three-dimensional and optically variable images and a laser phototypesetting system for realizing the method, which are used for making three-dimensional images and other images with optically variable characteristics. Background technique [0002] Digital three-dimensional and light-variable image is a new type of optical image, which is composed of pixel array, each pixel is a pixel grating (unit grating), the orientation and space frequency of the unit grating have infinite combinations, so that the image has The optical characteristics of various light-changing effects such as color change, dynamic effect and three-dimensional sense, the image can be very complex. For the relief-type image, it can be made into a reflective reproduction hologram through molded aluminum plating, and the human eye can directly face the image. The light source observes the reflected diffracte...

AI Technical Summary

Problems solved by technology

[0003] At present, there are mainly the following ways to make three-dimensional and optically variable images. One is to record holograms that form two-dimensional or three-dimensional images by light interference on a holographic dry plate. It is very difficult to obtain an optically variable image with high precision and dynamic effects; the other is laser direct writing, in which a computer controls the movement of a fine laser beam on the sample stage, and directly exposes on the surface of the photoresist to carve a continuous relief structure. A single-beam direct writing method has high requirements for electronic control and mechanical precision. If a grating of 10 mm × 10 mm is designed, the diameter of the focal point of the beam is 1 micron, and the operating speed is 10 mm / s. It takes at least 80 minutes for a 500 line / mm grating. For optically variable images with smaller grating constants and larger areas (such as optically variable images used for laser anti-counterfeiting packaging materials), single laser direct writing is obviously not suitable; The third is electron beam exposure. Although the grating precision of electron beam lithography is higher, its production cost is too high and the time is longer, and it is not feasible to obtain large-area three-dimensional and optically variable images.

For this reason, the inventor proposed a new production method in another patent application for the production method of an optically variable image and its phototypesetting system, that is, using an interference-type optical head as a laser direct writing head, and using a laser interference fringe image The pixels are used as laser direct writing points to realize the production of pixel gratings. Since one interference fringe pixel contains dozens of grating lines, it is dozens of times faster than the single-beam laser direct writing method, and can be used to design and manufacture larger areas. At the same time, the fringe density of the pixel grating can be higher, and a 10 mm × 10 mm grating is also designed. If the diameter of the focal point of the beam is 0.04 mm, and the operating speed is set to 80 dots / second, it takes more than 15 Minutes, significantly faster than single-beam direct writing, making large-area production possible; however, due to the running time limit of mechanical movement, for an area of ​​500 mm × 500 mm, it takes more than 400 hours. As a large-area application, the time is still It is unacceptable. On the other hand, in order to improve the resolution, the diameter of the beam needs to be reduced, which will lead to the reduction of the intersection area of ​​the two beams. Generally, when the spot diameter is 10 microns, the Vibrating up and down will seriously affect the overlapping degree of the two spots. Therefore, the highest image resolution of the system is 2540dpi

[0004] Considering the above-mentioned schemes, we found that in order to solve the problem of manual operation in holography, the subsequent methods are all made by single-point processing of interference fringes or unit grating points, which leads to slow speed. The main reason why it is difficult to make large-area images, if computer control can be used to realize the simultaneous production of multiple pixel raster points in the same image, the production speed will be greatly improved

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