That "ring" is not a closed circle. The laser diode is spreading almost 180 degrees in an almost planar direction. So the "ring" you see is due to reflections from the laser light that is reflected from inside the laser housing. When this light pass the lens, the reflections are not in a correct focal distance so the light will be projected as an image of the inside of the laser housing.
Most DVDburner lasers have a more narrow beam, making it able to project more energy in one direction. However, most diode lasers are projecting the laser light as a line, spreading the light very wide in one plane, while having a narrow beam angular to that plane. You have probably that kind of laser.
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