Three-dimensional printing system

A three-dimensional printing system, comprising:

• a tank filled with a liquid forming material;
• a platform movably positioned above the tank and adapted to immerse into the liquid forming material filler within the tank;
• a lighting module disposed below the tank and used for projecting light toward the liquid forming material, wherein the lighting module comprises a plurality of light emitting diodes (LEDs);
• a controlling module coupled to the lighting module, wherein the controlling module is configured to drive the lighting module to generate light that is focused onto a focus plane between the platform and the tank and away from a bottom of the tank with a predetermined distance for irradiating the liquid material, so that the liquid forming material is cured to form a cross-sectional layer,
• wherein the controlling module uses the brightness of one of the LEDs as a basis for varying the brightness of the other LEDs, so that the liquid forming material cured in each procedure has similar hardness;
• wherein a controlling signal provided by a controlling unit of the controlling module is a pulse width modulating signal, the controlling unit provides different on-times for each of the plurality of LEDs that with different maximum brightness by varying duty cycles of the pulse width modulating signal within the control signal;
• the control unit outputs the control signal including a plurality of duty cycles at the same time so that each of the plurality of LEDs outputs the same brightness, and the liquid forming material respective to each pixel receive the same energy and has same curing hardness, and then each of the cross-sectional layers has similar curing hardness;
• and
• wherein the lighting module further comprises a plurality of focus lenses or rod lenses arranged in between the focus plane and the LEDs for focusing light generated by the LEDs onto the focus plane so that a divergent light from one of the LEDs is shaped by one of the focused lens or rod lenses and focused onto the focus surface;
• an amount of the focus lenses or rod lenses is equal to that of the LEDs and each focus lens or rod lens is arranged with respect to each LED, and a first distance between centers of the focus lenses or rod lenses and light emitting surfaces of the LEDs is equal to a second distance between the centers of the focus lenses or rod lenses and the focus surface, therefore a height of the lighting module is effectively reduced to lower a shipping expense of the three-dimensional printing system.