Two ways to make a room-sized touch surface
A shared touch display lets a teacher or presenter write, drag objects and annotate material in front of a group. There are two broad ways to build one. The older approach is an interactive whiteboard: a board that works with a projector, with the projected image acting as the display. The newer approach is an interactive flat panel, a large screen with the display, touch sensing and often a built-in computer in a single unit.
The words are sometimes used loosely, and people may call either type a smartboard, so it helps to check which is meant.
How projector-based boards work
In a projector-based system, a computer sends its image to a projector, which shines it onto a board. The board itself supplies the touch or pen sensing, using methods such as electromagnetic detection under a hard surface, resistive layers, or infrared or camera sensors at the edge. Alternatively, a sensor bar or camera can be added to an existing wall or whiteboard. A calibration step lines up the projected image with the sensing area, so a touch lands where the user intends.
Projector setups can reach large sizes at relatively modest cost, and a large image can be shown even in a big room. The basics of projection are covered in the article on projector basics.
How flat panels work
An interactive flat panel is essentially a very large display, typically an LCD with an LED backlight, fitted with a touch system and usually a built-in operating system and speakers. Many use an infrared or optical frame, and some use capacitive sensing, depending on size and design. The panel can run apps and show content without a separate computer, though users often connect a laptop too. The article on infrared touch explains how the most common frames locate a touch.
Because the image comes from the screen itself, it does not depend on a lamp or on ambient shadows.
Differences you notice in a room
- Shadows: with a front projector, anyone standing at the board can block the beam and cast a shadow on their own work. Short-throw projectors reduce the problem by sitting close and angling the light, but do not always eliminate it. A flat panel has no such issue.
- Brightness and room lighting: projected images tend to look washed out when the room is bright, so lights may need to be dimmed. Flat panels are generally easier to see with the lights on, although glare from windows can still be a problem, a subject related to screen coatings.
- Image quality: a flat panel typically offers sharper text and a wider viewing angle, while a projected image can soften depending on focus, distance and the projector.
- Writing feel: some boards give a pen-on-paper feel, while a glass panel can feel slippery. Pen tracking quality also varies by technology, which is covered in the article on stylus input.
- Size: projectors can fill very large surfaces. Flat panels come in set sizes, and bigger ones can be heavy and costly.
Setup, upkeep and lifespan
Projector systems need a lamp or light source that dims with use, a filter that may need cleaning, and recalibration if the projector or board shifts. Bulb or light source replacement is an ongoing cost in lamp-based models. Flat panels have fewer moving parts, though they are heavy, need a sturdy wall mount or stand and can be costly to repair if the glass or panel is damaged. General information about expected service life is in the article on display lifespan.
Cleaning is simple in principle, but harsh chemicals can damage coatings, so follow the manufacturer’s care instructions as described in the guide to screen cleaning.
Software and sharing
A flat panel often includes software for whiteboard pages, annotation over other content, and saving or sharing what was written. Many support wireless casting from laptops, tablets and phones, so a visitor can show content without cables. Projector boards typically depend on whatever computer and software are attached. In both cases, the real value comes from how comfortably the room’s users can work with the software, and training often matters as much as hardware.
Which suits which room
A projector-based board may suit a budget-limited room where an existing projector is in place, or a space where a very large image is needed. A flat panel may suit rooms where brightness, simplicity and low maintenance matter most. Education settings in particular weigh these points, as seen in the discussion of classroom displays, although every school and company has different budgets, room layouts and support staff.
Questions worth asking before choosing
- How many people need to see the content, and from what distance?
- How bright is the room, and can the lights be dimmed?
- Will multiple people write at once? Not every system supports it.
- Is the software familiar to the people who will use it?
- Who will maintain it, and what happens if a part fails?
There is no single right answer, and many rooms use a mix of both approaches.