San Francisco - Apple is expected to rev up its iPad line on Tuesday as the tablet market heats up with competition from devices powered by software from Google and Microsoft.Analysts agree that iPads will star at an invitation-only event being held in San Francisco on the cusp of the prime year-end holiday shopping season."Job one for Apple is to get something out there on the large-size iPad that gets people excited, then obviously from a specification focus, the Mini needs to catch up with what everybody else has done," said NPD analyst Stephen Baker."There are a lot of other things happening in that large-size tablet space and there is a huge amount of choices in smaller devices."Tablets face mounting competition from touch screen notebook computers powered by Microsoft Windows software and priced between $350 and $500, according to the analyst.Display quality"Apple will... be number one in large-size tablets probably for a long time, but the definition of competition will change," Baker said.Apple is also under pressure to adapt to the popularity of premium tablets with high quality screens in the 18cm to 20cm range where the Mini competes.Online retail titan Amazon.com on Friday began shipping new 18cm Kindle Fire HDX tablets with boosted display quality and computing power at the starting price of $229."We can't wait to get this tablet into our customers' hands," said Amazon Kindle vice president Peter Larsen.Google's latest Nexus 7 tablet powered by its Android software has been a hot seller at a similarly tempting price.E-mailed invitations to the Apple event revealed little other than the time and place, and bore the message: "We still have a lot to cover."A graphic in the shape of an iPad showed Apple's logo under a shower of colourful leaves.Unconfirmed reports are that Apple will show off a new version of its full-size iPad that will be thinner than its predecessor and boast improved camera capabilities.Fingerprint recognitionScrutiny of Apple's supply chain has industry trackers thinking the new iPad will get "narrower, thinner, and lighter" and possibly be built with processors at least as powerful as those used in the freshly-launched iPhone 5s, according to Gartner analyst Van Baker.An upgraded version of the iPad Mini with an improved screen is also expected.Gartner's Baker will be watching whether new iPad models have 64-bit processors as engines in a significant boost that would enable tablets to handle more heavy weight programs and games."It has the potential to make tablets much more compelling devices in terms of content creation; making devices more sophisticated with more horsepower-hungry applications," the analyst said."It will increase the likelihood that tablets will displace PCs [personal computers]."Analysts agreed that top-end, full-size iPads may get a fingerprint recognition security feature to the one on the iPhone 5s.Such upgrades would promise to entice buyers to pay a bit more for full-size tablets from Apple instead of choosing lower-priced Mini models, boding well for the company's bottom line.The iPad remains the largest-selling tablet, according to surveys, but its market share is being eroded by rivals using the Google Android operating system.MacBook"Mobile connectivity continues to grow and its impact is much broader than business stories about which computer makers are selling the most units," said Kristen Purcell, associate director for research at the Pew Research Centre's Internet and American Life Project."We see mobile connectivity affecting everything from the way people get news and learn to the way they take care of their health and the way they share their lives through social media."Apple was also expected to discuss its computer operating system and its MacBook laptop line at the event.The company is coming off a successful launch of two new iPhone models last month. It estimates selling a record nine million iPhones in the three days after launching two new versions of the smartphone.