|There are usually two lasers in CD/DVD drives. The DVD laser is either worn out or the lense is extremely dirty.|
If you have a desktop computer just replace it. Burners are cheap. Look at the link below. Be aware you may need IDE ATA type interface while many of the current drives are SATA type interface. Both types are available at the link. Some with free shipping and some with software.
I see you have a slim case. Choices are scarcer and more money.
You may be able to clean the lens with a Qtip and alcohol after dismantling.