Each spot (pixel) that you view in the picture is made by a single mirror moving back and forth on the DMD. In total, there are over a million of these tiny mirrors, and the white spots you see are those mirrors that have stuck in the "On" position. These mirrors get jammed and hence this problem.
You can contact Samsung Support for the same. You have to call 1.800.726.7864 and request a service. Since it is only 4 years old, they might consider it as a premature failure of light engine and give you a discount, but you will have to persuade for that. Usually it costs around $800 to fix the problem. Hope it helps. If you have any other queries then I would be glad to assist you further.
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