Can a blue BD laser read/write to DVD/CD?

On Quora, the user called Michael Daniel claimed to own a BluRay player, which used solely a blue laser for all disc types.

I’ve never heard of that, and am doubtful. Every Blu-ray player or drive I’ve heard of has two laser assemblies, one of which is the longer wavelength red laser used for CD’s and DVD’s.

It is theoretically possible to use separate lasers behind a specially constructed holographic single lens. In a BD white paper I once read that LG displayed such a prototype device at the 2002 Consumer Electronic Show. This may be the basis for the quoted writer’s erroneous impression that a single laser was used. Using different lasers with separate optics was proven to be more reliable for backwards compatibility as the different thicknesses of the cover layers

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It is also possible to use a 3-wavelength laser assembly which would give the same impression on external examination.

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