Model for simulating heat induced by parallel laser beams traversing a thin metal film

This model simulates a laser imaging system that uses thermal energy as the exposure mechanism. The recording media is a metal film, typically bismuth, laminated between two transparent polymer sheets. It uses an input stream of binary pixel information to modulate a simulated array of lasers. Absorbed laser energy is converted into heat in the metal film of the recording media. The metal film is disrupted by the heat, allowing light to pass through in the exposed regions. The energy source, generally a laser diode or laser and AOM combination, exposes a recording media in response to the input binary data. The energy source is directed at successive positions in a line across the recording media by a scanning mechanism such that each such position reflects the position of each binary bit in the input stream. Successive lines of input data are positioned adjacent to each other to build an image on the output media that is representative of the input data. The purpose of developing this model was to provide an easily accessible and usable software package for quickly modeling different imaging systems based on thermal recording media. Toward this end the model was developed for the Windows 3. 1 operating environment with all parameters of the model available to the user. This includes the defining parameters for the laser beams, the modulation and switching systems, the thermal characteristics of the recording film, the recording data pattern and the pixel sample size. The simulation can be paused at any time to review the results as they are computed and these results can then be printed while the simulation is paused. The results, both of energy and temperature, can be measured on screen through user positioned guide lines overlaying the graphic display. The performance is such that less than one second is required for each pass through the model, making the system fast enough to use in exploring a wide range of system parameters when creating a new recording machine. Some systems will have multiple laser beams exposing multiple lines in parallel. This is a particularly important case to model due to the potential for thermal cross talk between the beams, particularly at low recording speeds where there is more time for heat to flow out from the exposed pixels. The model can support as many as four beams arranged in a single line. The line can be oriented at an angle relative to the direction of travel and each beam may be individually placed on the line. The model is composed of six discreet elements that reflect the primary components of a laser imaging system. These elements are the input binary data stream, laser driver circuit, laser modulator, laser spot at the recording media, the laser scanner mechanism and the recording media itself. The user interface of the model is designed to allow independent control of each element in the model. In addition there are provisions for examining the results of the model at various times during the simulation as well as the final output of the model. The software provides a means to store and retrieve a models parameters as well as to print the results of the model. A 50 MHz 486 based PC compatible system running DOS 5.X and Windows 3.1 was used to develop and run the model. The system contained 16 mBytes of RAM, though systems with 8 mBytes have successfully run the software. A color VGA display was used to display the model results.