New York - Nokia is expanding its line-up of Windows phones and introducing its first tablet computer, all sporting the powerful camera technology found in its flagship Lumia 1020 smartphone.The struggling cellphone maker is turning to the camera to differentiate its phones from rivals. The Lumia 1020 has a 41 megapixel camera with technology designed to produce better low-light shots and offer greater manual controls than most smartphones.The new devices will use Microsoft's Windows system and come as Microsoft aims to complete its €5.44bn ($7.4bn) deal to buy Nokia's phone business and patent rights. The deal is expected to close early next year.Nokia, a Finnish company, has seen its cellphone business unravel since Apple revolutionised the way people use handsets with the 2007 introduction of the iPhone. Microsoft, meanwhile, is struggling amid declines in sales of traditional personal computers in favour of smartphones and tablets.Nokia's new Lumia 1520 will have a larger screen, measuring 15cm diagonally, compared with 11.5cm on the 1020. Nokia said the new phone's camera will have only 20 megapixels in order to keep the camera sensor smaller and the phone thinner. But that's still more resolution than most other phones.FeaturesThe 1520 will also come with new apps designed to organise photos based on where you take the shots and to give you more flexibility in determining - after the fact - where the image should be focused. The phone will cost $740, though wireless carriers are expected to offer it cheaper with two-year service contracts.Nokia will also make a cheaper version, the Lumia 1320, for a contract-free price of $339. It will have a 5 megapixel camera and a slower processor than the 1520. Both run the latest version of Windows Phone 8, which has new features to accommodate larger screen sizes.Nokia's first tablet will be the Lumia 2520. It will run Windows 8.1 RT, meaning it shares the tile-based interface of the phone software, but can run various apps designed for Windows tablets. However, RT is the lightweight version of Windows, so it will run only apps specifically designed for it. Regular versions of Windows 8.1 can run apps for older versions of Windows.All versions of the 2520 will come with built-in 4G LTE cellular access. By contrast, iPads and most other tablets make cellular access optional, with their cheapest models capable of using Wi-Fi only for internet access.The 25cm tablet will cost $499. An optional cover with a physical keyboard and extended battery life is $149 extra. The camera is 6.7 megapixels, but shares the low-light technology and manual controls found in the Lumia 1020.All three devices are expected to go on sale by the end of the year. They will come in multiple colours with a hard, plastic back moulded onto the device.