Ugh, the stupid "observe means observed by a conscious being" thing again. Any* quantum interaction will cause a collapse of the wave function. No conscious observer is required. When you do the experiment in a closed box and just increase the temperature to make it more likely for air molecules to interact with the laser you will also get a slit pattern.
*not really any interaction, scientists actually still aren't sure what exactly constitutes a measurement, but we're pretty sure a human is not needed