As stated above, you cannot SCAN at dpi, you can only PRINT at dpi. It refers to dots per inch, that is to say the number of dots of ink available to you per inch of paper. It is a printing term, not a digital term and as such has no relevance to scanning or digital information. If you have a scanner that is using dpi, it may well be that it is also a photocopier which scans and then prints - so it refers to print quality not scan quality.