Actually, they can't! The laser assembly is completely different between CD, DVD, and BD. You probably concluded this because popular bluray drives on the market also include the hardware to read other kinds of disks. The disk drive Sony uses in the PS5 supports BD and DVD, but not CD.
This was a choice by Sony as nearly all commercial drive have both. Usually DVD and CD optic are combined as one unit as well. Do combination BD/DVD optic exist? Otherwise I do not understand a reason to not use a combined CD/DVD unit.
Red book CD-ROM audio does not require license to play, so I am not sure. Looking at a photo of the assembly it looks like there are one lens on some unit and two lens on other, so it must be a BD/DVD combination unit from some supplier and separate from other.
Actually, they can't! The laser assembly is completely different between CD, DVD, and BD. You probably concluded this because popular bluray drives on the market also include the hardware to read other kinds of disks. The disk drive Sony uses in the PS5 supports BD and DVD, but not CD.
This was a choice by Sony as nearly all commercial drive have both. Usually DVD and CD optic are combined as one unit as well. Do combination BD/DVD optic exist? Otherwise I do not understand a reason to not use a combined CD/DVD unit.
All I know is the PS4 and PS5 can play DVD movies, but will reject audio CDs. Perhaps it's some kind of licensing issue.
Red book CD-ROM audio does not require license to play, so I am not sure. Looking at a photo of the assembly it looks like there are one lens on some unit and two lens on other, so it must be a BD/DVD combination unit from some supplier and separate from other.