Programmable 2D laser marking device based on a pulsed UV image coherent amplifier

Abstract

We present a novel technique for engraving microscopic 2D patterns in one step with a UV pulsed laser by means of a versatile programmable approach. The laser beam is divided to an expanded low energy signal beam which is spatially modulated by a LCD modulator and a higher energy pump beam with a plane homogeneous wave front. Both beams are superposed in a highly magnesium doped photorefractive lithium-niobate crystal where an energy transfer towards the weaker signal beam takes place. The spatially modulated and amplified signal beam is then de-magnified and imaged onto the surface where the image has to be engraved. The need for the coherent amplifier rises out of the fact that LCDs are unable to withstand the high energy throughput required for etching. The combination of the amplifier with the amplitude modulator leads to a faster and more flexible solution than laser marking with pixel-by-pixel raster-scan, or fixed mask projection mode. Such a technique can thus be applied to identify valuable items by imprinting a smart and personalised 2D code onto its surface.

Multilevel 2-D Bar Codes: Toward High-Capacity Storage Modules for Multimedia Security and Management

“…We consider the problem of data transmission via the continuous print-and-scan channel 2 as a digital communications problem. 2 Notice that the physical processes of printing and scanning are continuous. Although, strictly speaking, the actual input and output of the print-and-scan channel are digital, we assume that the granularity of the involved quantization is fine enough to let us consider the print-and-scan channel as being continuous.…”

“…from a zero-mean Gaussian distribution with variance σ 2 Z and is assumed to be independent from the channel input X. This model can be considered as a particular case of model (2) and 3under the assumption that ϕ(x) = x, σ Z (x) = σ Z , and γ Z (x) = 2, for all x ∈ X . Given the channel input variance σ 2 X , the capacity of this channel, in bits per channel use, is:…”

“…Besides being cheap and simple, their main advantage is that they can carry a significant amount of information on surfaces such as paper, plastic, or even ceramics. 2D bar codes can be either directly printed on the above surfaces or engraved using appropriate lasers [1], [2]. Moreover, printing can be performed using either visible, ultraviolet, or infrared inks, depending on the application's concern about security.…”