Touchscreens allow users to interact directly with a device’s display by touching it. There are several types, but the Cambridge IGCSE syllabus specifically covers four touchscreen technologies:
- Capacitive
- Resistive
- Infrared (Heat-based)
- Infrared (Light-based)
Let’s explore how each one works, their advantages, disadvantages, and common applications.
1. Capacitive Touchscreen
✦ How It Works:
- The screen is coated with a conductive material (usually indium tin oxide).
- This material stores a uniform electrostatic charge across the screen.
- When a finger touches the screen:
- A small amount of charge is drawn to the point of contact.
- Sensors at screen edges detect this change in capacitance.
- A controller calculates the exact location of the touch.
✦ Key Features:
- Requires a conductive object (like a human finger or special stylus).
- Supports multi-touch (e.g., pinch-to-zoom).
✦ Advantages:
- High responsiveness and accuracy
- Excellent screen clarity
- Durable surface (usually glass)
✦ Disadvantages:
- Doesn’t work with gloves or non-conductive styluses
- More expensive than resistive
✦ Common Uses:
- Smartphones
- Tablets
- Modern laptops
2. Resistive Touchscreen
✦ How It Works:
- Made of two thin layers: one conductive, one resistive, separated by a small gap.
- When you press the screen:
- The two layers make physical contact.
- This completes a circuit at that specific location.
- The coordinates are sent to the device’s processor.
✦ Key Features:
- Works with any pointing device (stylus, gloves, fingernail, etc.)
- Requires physical pressure to register touch.
✦ Advantages:
- Inexpensive to manufacture
- Works in harsh environments
- Works with gloves/stylus
✦ Disadvantages:
- Less sensitive than capacitive
- No multi-touch capability
- Lower display clarity due to extra layers
✦ Common Uses:
- ATMs
- Industrial control panels
- Older mobile phones and PDAs
3. Infrared Touchscreen (Heat Detection Method)
✦ How It Works:
- The screen is surrounded by infrared sensors that detect heat changes.
- When a warm object (like a human finger) touches the screen:
- The temperature difference is detected by the sensors.
- The system determines the position of the touch based on heat location.
✦ Key Features:
- Relies on the presence of body heat.
✦ Advantages:
- No need to apply pressure
- Durable surface—nothing layered on top of the display
✦ Disadvantages:
- Only works with warm objects (no gloves or stylus)
- Slower than other types
- Prone to false readings if the screen is exposed to heat
✦ Common Uses:
- Some kiosks and medical equipment
- Not widely used in commercial consumer devices
4. Infrared Touchscreen (Light Beam Interruption Method)
✦ How It Works:
- The screen is surrounded by a grid of infrared LED emitters and sensors.
- These create an invisible grid of light beams just above the screen’s surface.
- When an object interrupts one or more beams:
- The device detects which horizontal and vertical beams were broken.
- The touch coordinates are calculated from this intersection.
✦ Key Features:
- Doesn’t require heat or pressure
- Works with any object (glove, stylus, finger, etc.)
✦ Advantages:
- Highly durable — no layers to wear out
- Excellent visibility (no conductive layers blocking the screen)
- Works with stylus, gloves, or any object
✦ Disadvantages:
- Can be affected by dust, dirt, or strong ambient light
- Bulkier due to sensor frame
✦ Common Uses:
- Interactive whiteboards
- Public information kiosks
- POS (Point-of-Sale) systems
Summary Comparison Table
| Feature | Capacitive | Resistive | IR (Heat) | IR (Light Beam) |
|---|---|---|---|---|
| Input Method | Finger/capacitive stylus | Any pointing device | Warm object (finger) | Any object |
| Touch Detection | Electrical charge | Physical pressure | Heat sensing | Beam interruption |
| Multi-Touch Support | ✅ Yes | ❌ No | ❌ No | ✅ Possible |
| Glove Compatible | ❌ No | ✅ Yes | ❌ No | ✅ Yes |
| Cost | Higher | Low | Medium | Medium to High |
| Sensitivity & Accuracy | High | Moderate | Low | High |
| Screen Clarity | Excellent | Reduced (due to layers) | Good | Excellent |
| Common Applications | Phones, tablets | ATMs, kiosks | Specialized equipment | Whiteboards, kiosks |
Key IGCSE Exam Tips:
- You must be able to describe how each touchscreen works — not just identify it.
- Be prepared to compare touchscreens based on:
- Input method
- Cost
- Use cases
- Advantages/disadvantages
- Questions often involve a scenario, e.g., “Which touchscreen is best for an outdoor information kiosk?” (Answer: Infrared light-based)