Dark Shade on Screen/ I miss my projector

[Uncle Al]

I have a 6100 BenQ projector,when the old lamp was at the end of its time a dark shade started showing at a bottom corner and got darker per day. I recieved my new lamp, installed it and ths shade on the screen still existed. I looked at the interoior components and see a round glass which is in front of the lamp and seen some type of design and i don't know if that is the problem. Anyone w/ any info please respond . I miss my projector. thanks All