How a projection keyboard generally works:
- A laser or beamer projects visible virtual keyboard onto level surface
- A sensor or camera in the projector picks up finger movements[3]
- detected co-ordinates determine actions or characters to be generated
- An invisible infrared beam is projected above the virtual keyboard
- Finger makes keystroke on virtual keyboard. This breaks infrared beam and infrared light is reflected back to projector
- Reflected infrared beam passes through infrared filter to camera
- Camera photographs angle of incoming infrared light
- Sensor chip determines where infrared beam was broken
- detected coordinates determine actions or characters to be generated
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhbrzrhzJLVKv9nhAWkcPjghm6B6WyZO7dCY0iH_fUS2n6mCAub69IishyKABBNL6ZZvJ-CzyI3LChAXksOklQ8YaTYsXFFGtZpP_RZQ_VsSd3OO0_7_QlQcGGnqRW2aKCJ86nac5LrXceR/s320/800px-ProjectionKeyboard_2.jpg)
In 2002, the start-up company Canesta developed a projection keyboard using their proprietary "electronic perception technology".[4][5][6] The company subsequently licensed the technology to Celluon of Korea.[7]
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Projection keyboards connectivity
Projection keyboards connect to the devices they are used for either through Bluetooth or USB.The Bluetooth projection keyboard is a wireless virtual keyboard, a pocket-size device that projects a full-size keyboard through infrared technology onto any flat surface.[8]
Bluetooth dongle technology enables the projection keyboard for point to multi-point friendly connectivity with other Bluetooth devices, such as PCs, PDAs and mobile phone. Bluetooth is an open specification for wireless data transmission which operates on the globally available 2.4GHz radio frequency.[9]
The way the Bluetooth projection keyboard is connected to a device varies depending on the specific laptop, phone or computer that the user intends to use it for. All the connectivity instructions normally come with the product and they basically consist in turning on the Bluetooth connection on one's device and then turning on the keyboard.
The USB projection keyboard works like a regular USB keyboard. The connection between the virtual keyboard and the device is made through a USB port, which is available on every computer, laptop and other devices that are compatible with the projection keyboard. Connection instructions come as well with the product and with the manufacturer's specifications but it mainly consists in Plug and Play the devices.
How laser keyboards work
The laser keyboards use laser and infra-red technology to create the virtual keyboard and to project the hologram of a keyboard on a flat surface.[10]The projection is realized in four main steps and via three modules: projection module, sensor module and illumination module. The main devices and technologies used to project the hologram are a diffractive optical element, red laser diode, CMOS camera and sensor chip and an infrared (IR) laser diode.
Template projection (Projection module)
A template produced by a specially designed and highly efficient holographic element with a red diode laser is projected onto the adjacent interface surface. [11] The template is not however involved in the detection process and it is only used as a reference for the user. In a fixed environment, the template can just as easily be printed onto the interface surface.Reference plane illumination (Micro-illumination ModuleTM)
An infra-red plane of light is generated on the interface surface. The plane is however situated just above and parallel to the surface. The light is invisible to the user and hovers a few millimeters above the surface. When a key position is touched on the surface interface, the light is reflected from the infra-red plane in the vicinity of the key and directed towards the sensor module.Map reflection coordinates (Sensor Module)
The reflected light user interactions with the interface surface is passed through an infra-red filter and imaged on to a CMOS image sensor in the sensor module. The sensor chip has a custom hardware embedded such as the Virtual Interface Processing CoreTM and it is capable of making a real-time determination of the location from where the light was reflected. The processing core may track not only one, but multiple light reflections at the same time and it can support multiple keystrokes and overlapping cursor control inputs.Interpretation and communication (Sensor module)
The micro-controller in the sensor module receives the positional information corresponding to the light flashes from the sensor processing core, interprets the events and then communicates them through the appropriate interface to external devices. By events it is understood any key stroke, mouse or touchpad control.Most projection keyboards use a red diode laser as a light source and may project a full size QWERTY layout keyboard. The project keyboard size is usually 295 mm x 95 mm and it is projected at a distance of 60 mm from the virtual keyboard unit. The projection keyboard may detect up to 400 characters per minute and it may be connected by using either USB ports or Bluetooth.
The projection keyboard unit works on lithium-ion batteries and it has a capacity of at least 120 minutes of continuous typing. The projection unit sizes vary on the manufacturer but normally it is not bigger than 35 mm x 92 mm x 25 mm.
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