Microsoft has developed a new head-worn device which it claims is the most advanced holographic computer the world has ever seen.

HoloLens projects 3D holograms into the users real world view.

The new device features see through HD holographic lenses, powered by an on board computer.

The company says as part of its development it had to invent a third processor to work alongside the integrated Central Processing Unit and graphics chip.

HoloLens has spatial sound built into it, and does not require a phone or PC connection to operate.

The company has also built HoloStudio, a software application in which holograms can be designed and from where the designs can be exported for 3D printing.

The company said it had worked on the project for years at a top-secret space in the Microsoft Visitor's Centre.

The tool has been developed in partnership with NASA.

HoloLens was unveiled at a briefing at Microsoft's headquarters, during which the company released further details about its new Windows 10 operating system.

The company said anyone with Windows 7, 8.1 or Windows Phone 8.1 would qualify for a complimentary upgrade to the new software during the first year after the general release of Windows 10 later this year.

The new operating system will see the return of the Start Button and Menu, which were controversially axed in Windows 8.

The company also revealed that its digital assistant, Cortana, will work on PC as part of the new release.

The company also announced that it is developing a new web browser, codenamed Project Spartan, alongside its existing Internet Explorer.

It has a new user interface and a number of other features including a note-taking mode, a reading mode and Cortana integration.

However, Microsoft's Joe Belfiore said it would not be available in the first insider build version of Windows 10 and a phone version would take longer to develop.

Windows 10 will also feature Continuum - a system which automatically recognises what kind of device the operating system is running on, and adapt accordingly.

For example, if a keyboard is added to a Microsoft's Surface tablet, the operating system will be able to switch from tablet to desktop mode.

As part of the new release, Microsoft is also creating a suite of built-in productivity apps that will work across PC, tablet and phone.

There is also a new Xbox app for Windows 10, in a move designed to integrate one of the company's most successful services, Xbox Live, with the new operating system.

The company also said that the new software would protect data and support more devices than ever before.

The new version of Windows, which is still under development, has been tweaked and improved as a result of a programme of testing and feedback involving 1.7 million people.

It will also have an integrated search facility which will work across all Windows 10 devices, the web and the cloud.

Microsoft is under pressure to deliver a vastly improved version of Windows after the previous version of the operating system failed to take off.

Windows 7 accounts for 56% of the desktop computer market, but Windows 8 and 8.1 languish on just 13%. Even the now 14-year-old Windows XP is still running on 18% of desktops, despite the fact it is no longer being supported by Microsoft.

Microsoft CEO, Satya Nadella, said today is a big day for Windows, its customers and partners and is about Microsoft's innovation going forward.

He said the company has an aspiration to move from a situation where people need Windows to where they love Windows.