According to a study by UltraLeap, a manufacturer of touchless interfaces, the acceptance of touchscreens has declined. Assuming a certain level of complexity, there are various alternatives. One of these is holographic input, which works with a projected hologram and an infrared touchscreen. This system consists of two parts: an infrared touchscreen that detects touch events and gestures with an invisible IR curtain, and an image that is holographically projected into the air.

In the physical sense, the virtual image is not a hologram - monochromatic, coherent light is not used, nor does the image change depending on the viewing angle. Instead, a special material property is used here that convergently bundles the diffusely emitted light rays at the location of the virtual image, thus creating the impression of a free-floating display. The term 'holography' is used for this.

The infrared touch technology

The new technology infrared touchscreen uses the light rays reflected by an object to detect one or more touch events. Photodiodes in the sensor detect the reflected rays.

© Neonode

Thanks to the infrared sensor, touchless operation can be carried out with any object that reflects light - including protective gloves, credit cards and pens, and operation is easy even with wet or dirty hands and long fingernails. In contrast to other touch technologies, there is no layer between the finger and the display to impair the image quality. In addition, if the display is to be protected from adverse environmental conditions and vandalism, the sensor can be mounted at an appropriate distance from the display. The infrared touchscreen uses the reflection from objects in the beam path
to recognize several events simultaneously or gestures.

The 3D projection

The holographic image appears free-standing in the air. The key element is an optical plate that deflects the image generated by the source and projects it according to the laws of optics. Similar to a head-up display in a car: the driver sees an image through the windshield that displays additional information such as speed, traffic signs and navigation instructions in augmented reality. The driver's attention remains focused on the road ahead and the virtual image. The distant display takes the strain off the driver's eyes, which do not have to accommodate between close-up - looking at the instrument panel - and distant - looking at the road. The image itself is generated by a display or projector in the footwell and projected through a lens unit onto the windscreen, which has a partially reflective coating in this area.

Functional principle of the holographic display. The virtual image is displayed floating freely in space thanks to the special 3D plate.

© Aska3D

In this system, the structure looks very similar: The 3D plate creates a virtual image that is 'within reach' of the user. This virtual image is created at the same distance from the mirror as the display itself. If an infrared sensor is now mounted at the position of the image plane, which overlooks the image surface, touch events and gestures that are drawn 'in the air' can be recognized and evaluated without the need to touch any parts.

The holographic projection

The image projection in the air - the holographic display - makes it possible to project the image of an LCD screen 90° away from the screen. The resulting image appears to float freely in space on an invisible screen. A special holographic plate consisting of several layers of micromirrors deflects the light emitted by the display. The plate is positioned at an angle of 45° in the beam path and deflects the light emitted by the display by a further 45°. The divergent light beams converge at one point, creating the floating image. The size of the plate determines the maximum distance and the size of the image.

As there is a fixed angular relationship between the display, the projection plate and the final image, the installation geometry of the display and projection plate determines the orientation of the virtual image. A vertical image is produced by a horizontally mounted display and a 45° plate, while a horizontal projection plate produces a 45° tilted image.

The holographic screen as a user interface

The position of the hologram - vertical or inclined - is defined by the geometric arrangement of the image source (display) and 3D slice.

© Neonode

As with all touch applications, the graphical user interface (GUI) should be ergonomically adapted to the operating conditions. While sensitive movements can be made with a mouse because it is moved on a surface, a pen can be moved in three dimensions until it touches the surface. With holographic operation, on the other hand, the haptics of a surface are completely absent, so that even after touching a button, the hand must be guided completely freely. Filigree structures are therefore difficult to operate, especially for inexperienced occasional users. Designers of software interfaces must take this into account when arranging and sizing control elements. The use of gestures should also be chosen carefully to avoid inadvertently triggering an operating gesture while accessing an element by moving it sideways. Thanks to their high resolution and parameterizability, Neonode's infrared sensors enable precise cooperation with the holographic input.