Thermal defocusing is a phenomenon where the clear text or images on the projection screen blur soon after use, requiring repeated adjustments to become clear again.
Focusing is a very important part of projector imaging, and a perfect focus delivers a clear and stable picture. Otherwise, the projection image will be blurred. Provided the projector has focused beforehand, the projector gradually gets blurred after 10-min use can be viewed as “Thermal defocusing”.
In fact, the principle is also very simple, it is the “thermal expansion “. If the projector has worked for a long time, the internal parts began to hot, specifically, the lens, lens barrel, and structural components shift, then the lens focus will move, resulting in a blurred picture.
Thermal defocusing is a widespread and persistent problem in the projector industry, and projectors are basically unavoidable. The impact of Thermal defocusing is even greater on pico projectors, which are more susceptible due to their small size and close proximity of components.
To avoid the problem, it is necessary to improve the lens module and heat dissipation system.
Projectors on the market mainly adopt two types lens, glass lenses, and resin lenses. As an optical lens, a Glass lens has an absolute advantage in heat resistance, and its production process is harsh, whose imaging effect is also better. The resin lens is relatively poor in terms of heat resistance and is more likely to produce deformation and run out of focus.
You may be interested in Glass Lens vs Resin Lens.
As for the heat dissipation system, the projector should have more vents and good fans to dissipate the internal heat.
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