scan not clear

I have a dell a920 all in one.  I used to be able to scan documents, save them and be able to read them.  I can no longer make a document scan clearn.  I have installed the printer software and reinstalled it.  I have gone to the Dell site and checked for updated.  Nothing works.  Can anyone suggest what I am doing wrong and how I can again scan a document and have it come out clear and readable?

Thank you