Content
Sensing the Touch: A Tour of IWB Technologies
The method used to detect interaction is the primary differentiator between various types of interactive whiteboards. Over the years, several distinct technologies have emerged, each offering a different balance of cost, performance, and features.Resistive Touch Technology
One of the earlier and more straightforward methods is Resistive technology. Imagine the whiteboard surface as a sandwich. There are two flexible layers, coated with a conductive material, separated by a very thin air gap or tiny spacer dots. When you press on the top flexible layer with a finger or any stylus, it pushes through the gap and makes physical contact with the bottom layer at that specific point. This contact completes an electrical circuit. The board’s electronics measure the resistance characteristics of this contact point to calculate its exact X and Y coordinates. This coordinate data is then sent to the connected computer, which moves the mouse cursor or registers a pen stroke accordingly. Resistive boards are generally lower in cost and respond to pressure from any object – a finger, a gloved hand, a standard stylus. However, the flexible layers can be susceptible to damage from sharp objects, potentially leading to dead spots if punctured. The clarity of the projected image can also be slightly reduced due to the layers, and they typically only support single-touch input.Electromagnetic Resonance (EMR)
Electromagnetic systems take a different approach. Instead of relying on physical pressure, they use a special battery-free pen (an active stylus) and a grid of wires embedded behind the solid whiteboard surface. This grid generates a weak electromagnetic field. The pen contains a resonant circuit. When the pen tip is brought near the surface, it interacts with the electromagnetic field generated by the grid. The sensors in the grid detect the pen’s signal and its precise location. This technology is known for high accuracy and resolution, making it excellent for detailed writing or drawing. It also allows for features like pressure sensitivity (varying line thickness based on how hard you press) and hover capabilities (the cursor follows the pen even before it touches the board). The main drawback is the dependency on the specific proprietary pen – if the pen is lost or damaged, the board cannot be used interactively with touch. Standard EMR boards usually only track the special pen, not finger touches, although some hybrid systems exist.Infrared (IR) Optical Technology
Infrared technology works by creating an invisible grid of light across the surface of the board. Emitters (LEDs) are placed along two adjacent edges of the board’s frame, sending out horizontal and vertical beams of infrared light. Sensors (phototransistors) are positioned along the opposite two edges, detecting these beams. When you touch the board with a finger or any non-transparent object, you physically block some of these horizontal and vertical IR beams at that point. The sensors detect these interruptions, and the controller calculates the X and Y coordinates based on which beams are blocked. IR boards offer several advantages. The surface itself is typically just a hard, durable panel (often porcelain enamel on steel, suitable for dry-erase markers), as the sensing happens in the frame. This makes them quite robust. They inherently support multi-touch, as multiple points of interruption can be detected simultaneously. They also work with any pointing object. Potential downsides include sensitivity to bright ambient light, which can sometimes interfere with the sensors, and the possibility of inaccurate readings if something (like a shirt sleeve) accidentally breaks the beams near the intended touch point. Dust buildup on the emitters or sensors in the bezel can also affect performance over time.Optical Imaging (Camera-Based)
Closely related to IR, but distinct, is Optical Imaging technology. Instead of a full grid of emitters and sensors, this method typically uses digital cameras, usually placed in the corners of the whiteboard’s frame. These cameras continuously monitor the surface. When an object (like a finger or stylus) touches the surface, the cameras detect its shadow or silhouette against the background. By triangulating the position from the perspective of two or more cameras, the system calculates the precise location of the touch. Like IR, optical systems allow for a durable, passive surface and support multi-touch input. They can be quite accurate. However, performance can sometimes be affected by changing light conditions or shadows cast across the surface. If one of the cameras’ lines of sight is blocked, tracking can be interrupted. An early example of this approach was SMART Technologies’ DViT (Digital Vision Touch).Capacitive Touch Technology
Many people are familiar with Capacitive touch from their smartphones and tablets. Interactive whiteboards can use this same principle. The most common type is Projected Capacitive (PCap). A conductive grid (often made of indium tin oxide, ITO) is embedded within layers of glass on the surface. The human body is naturally conductive and holds an electrical charge. When your finger approaches or touches the screen, it distorts the electrostatic field of the sensor grid at that point. The controller measures the change in capacitance at various points on the grid to determine the touch location with high precision. Capacitive touch offers excellent responsiveness, clarity (as the sensor grid can be very transparent), and durability due to the protective glass top layer. It supports multi-touch gestures smoothly. Early capacitive IWBs were often more expensive, but costs have come down. A potential limitation is that they typically require a bare finger or a special conductive stylus to work; standard styluses or gloved hands won’t usually register.Verified Information: Regardless of the touch technology used, proper calibration is essential for most interactive whiteboards, especially those using projectors. Calibration aligns the touch-sensing coordinates with the displayed image coordinates. This ensures that when you touch a specific spot on the board, the cursor appears exactly where you touched. Regular recalibration, particularly if the projector or board is moved, prevents frustrating offsets between touch input and visual feedback.
Connecting the Pieces: Data and Display
Regardless of the sensing method, the calculated touch coordinates need to reach the computer. This is almost universally achieved via a USB connection. The interactive whiteboard essentially acts as a large input device, similar to a mouse or graphics tablet, sending coordinate data over USB. Some modern boards offer wireless connectivity options as well, typically using Bluetooth or a dedicated Wi-Fi connection. For systems relying on projectors, a video connection (like HDMI or VGA) runs from the computer to the projector, displaying the computer’s desktop onto the whiteboard surface. The magic happens when the computer’s software receives the touch coordinates via USB and interprets them relative to the projected image.The Role of Software
It’s crucial to remember that the hardware technology is only half the story. Specialized software running on the connected computer is what truly brings the interactive whiteboard to life. This software performs several key functions:- Driver Installation: It provides the necessary drivers for the computer’s operating system to recognize the whiteboard as an input device.
- Calibration Utility: It includes a tool to perform the essential calibration process described earlier.
- Input Interpretation: It translates the raw coordinate data into mouse movements, clicks, drags, or digital ink strokes.
- Interactive Tools: It usually offers a suite of tools for annotation (writing or drawing over any application), capturing screenshots, saving notes, using virtual keyboards, shape recognition, and integrating with other applications.
