Microsoft develops 3D touchscreen with tactile feedback
Details of a touchscreen showing 3D images that can be felt and manipulated have been published by Microsoft's research unit.
The project combines an LCD flat panel screen with force sensors and a robotic arm that moves it back and forwards.
By controlling how much resistance there is to a user's fingertip the firm says it can simulate the shape and weight of objects shown on screen.
Microsoft says the device could have medical uses as well as for gaming.
Work on the project is being carried out at the firm's Redmond campus near Seattle.
When a person touches the prototype it pushes back with a light force to ensure one of their fingers stays in contact with the screen.
If they then press against it the robotic arm instantly pulls the screen backwards in a matching smooth movement. If they start to retract their finger, it moves it back towards them.
Meanwhile a computer adjusts the size and perspective of the on-screen graphics to create a 3D effect.
The trick to simulating a physical sense of touch is to adjust the amount of force-feedback resistance.
So, in an application which shows graphics representing different square blocks on a wall, a "stone" one requires a relatively large amount of force to push it off the ledge and a "sponge" one less.
In addition, the kit can be used to provide a sense of shape by adjusting the screen's position to match a virtual object's contours as a person drags their finger over its surface.
"As your finger pushes on the touchscreen and the senses merge with stereo vision, if we do the convergence correctly and update the visuals constantly so that they correspond to your finger's depth perception, this is enough for your brain to accept the virtual world as real," said senior researcher Michael Pahud.
His team have used the technique to allow users to feel the shape of a virtual cup and ball, among other objects, while viewing them using special glasses to get a stereo-vision effect.
Microsoft suggests one use for the device would be to allow doctors to explore body scans.
It has created a demonstration using magnetic resonance imaging (MRI) scans of a brain to show how a medic could navigate through the different slices by pushing their finger against the display.
It also allows them to draw notes and leave a "haptic detent" - or force-feedback marker - at certain layers to make it easier to find them again later on.
In time, the researchers suggest, this could be extended to flag up potential problems.
"I could imagine receiving haptic feedback when you encountered an anomaly, such as a tumour, because we can change the response based on what you touch," said Mr Pahud.
"You can have different responses for when you touch soft tissue versus hard tissue, which makes for a very rich experience."
One medical tech expert said the project showed promise, but added that previous efforts to try to use touch-based feedback in robotic surgery and other health-related equipment suggested it was not yet responsive enough to be reliable.
In particular, Dr Peter Weller, head of the Centre for Health Infomatics at City University, London, said he was concerned Microsoft's screen would not be able to give an accurate enough indication of textures.
"If you were moving your finger over a surface that was rough the screen would have to go up and down very quickly to be able to give you that impression," he told the BBC.
"The examples that they give are all very smooth - squares and cylinders and all that - but if it was going to be used in the real world it would have to respond to rapidly changing shapes."
Others are working on different ways to provide touch-feedback. California-based Tactus, for example, has developed a screen with tiny channels of fluid which allows bumps to pop up to simulate the feel of buttons.
Dr Weller suggested that if this or other such technologies could be combined with Microsoft's current research then its screen could indeed find its way into use.
"I think their example of the brain scan is a bit artificial, but where I could see it being useful would be for a doctor doing teleconsultancy work," he said,
"It would mean the patient could be in another country or hospital and the doctor could feel their glands or abdomen from a distance."