Simulation for illumination optimization

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Janóczki Mihály
Department of Electronics Technology


During my laboratory work I have started to research for a lighting

simulation method by means of computer graphics, to create a software,

which makes easier the optimisation setup of the automatic optical

inspection systems. First of all I had been studied the basic of

computer graphics, then component models were generated, and these

models were later applied to the lighting simulation. In my diploma

plan we developed in C++ language a graphics application running on

graphics processor together with my tutor.

The most important parts of the program struct are the handling of

light sources and the reflectance model of the different materials.

To the correct simulation metal surfaces should be displayed as realistic

as possible, that is why the Cook-Torrance method was selected as

behavior descriptor. The shaders of the graphics processing unit are

programmed to calculate the intensity of pixels according to this model.

The light source parameters should be modifyable in runtime to a fast

search for the optimised illumination setup in case of a failure.

The light sources are stored in a flexible structure, that means that

all the frequently applied lighting elements like spotlight, ringlight

and skydome are disassembled to spotlights. This method permit to alter

the geometrical parameters and intensity of sources. On the other hand

this is necessary for the calculation of shadowing at which was analysed

how the component models of the rendered scene cover each other.

A shadowmap is generated for each lightsources used as a point of view.

In this map the distance values of the nearest objects to the source are

stored and during the rendering it is sampled and the probability of

incidence is calculated. In this way the simulation gives a realistic


After the program was completed I compared the simulation against

the snapshot of a real AOI machine. Based on the test of the basic

illumination elements I made an optimisation for the tombstone failure

of a surface mounted capacitor. I found a lighting configuration which

gives an effective failure detection. I tested this solution on a

real machine. In the future I would like to improve the application

with the refinement of the image synthesis and implementing of additional

functions. I could use my experiences with programming of graphics processor

in the image processing also.


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