Microsoft could be one of the surprise beneficiaries of Amazon's new Kindle Fire tablet, by using its patent claims to Google's Android operating system (OS) to force Amazon to pay royalties on each device it sells.

The just-launched Kindle Fire runs on the Android OS, leaving it vulnerable to Microsoft's claims that the OS infringes on its patents.

Both Apple and Microsoft have used their patent collections to sue or collect royalties from Android device makers. The practice is so lucrative for Microsoft, that it reportedly makes more from a patent-licensing agreement with Taiwanese smartphone maker HTC than from sales of its own Windows Phone.

Just today, Microsoft announced it had signed a patent-license agreement with Samsung, the latest deal in a series of agreements with Android device makers.

Last year, Amazon agreed to pay licensing fees to Microsoft for patents related to its use of open-source and proprietary technologies in its Kindle e-reader, as well as its use of Linux-based computer servers. The fees were part of a larger cross-licensing agreement between the two companies, which gave each company a license to the other's patent portfolio.

However, last year's Kindle deal doesn't cover the Android OS, reports The Seattle Times, which means the door is wide open for Microsoft.

Microsoft reportedly receives $5 per HTC device manufactured, but has asked for as much as $15 per device in recent months.

Analysts with J.P Morgan say they expect Amazon to sell 4 million to 5 million Kindle Fire tablets in the fourth quarter of 2011 -- I'll leave you to do the math.

Related TechFlash coverage of the Kindle Fire launch:

Amazon Kindle Fire tablet priced at $199, ready to rival iPad

Is Kindle Fire a game-changer in bid to catch red-hot iPad?