1.2 - Laptop Displays: Professor Messer

Exam Objectives

1.2: Compare and contrast the display components of mobile devices.

• Types

  • Liquid Crystal Display (LCD): Light shines through liquid crystals and through color filters to display images. Lightweight, low power, and inexpensive. However, cannot produce true black and requires a separate backlight (e.g., fluorescent, LED) - leading to replacement difficulties

    • In-plane switching (IPS): Best color representation for an LCD screen, but more expensive compared to a TN LCD, and lower response times.

    • Vertical alignment (VA): Compromise between TN and IPS, great color representation, but slower response times compared to a TN.

    • Twisted Nematic (TN): Very fast response times (great for gamers/fast response applications), but produces poor coloring when shifting angles

  • Organic Light-Emitting Diode (OLED): No backlight; organic compound produces light when an electric current is applied. Thin, flexible, and mobile screens. Typically used in smartwatches or phones, but can cost more compared to an LCD.

  • LCD power sources:

    • CCFL (Cold Cathode Flourescent Lamp) - high voltage and power displays, makes laptops thicker - older laptops use this

    • LED-backlight display: Array of LEDs behind screen, thinner and less power-intensive compared to CCFL backlights. Newer laptops use LEDs.

• Mobile display components:

• Wi-Fi antenna connector/placement: Networking antennas (Wi-Fi main, Wi-Fi aux, Bluetooth), wrap around the laptop display screen.

• Microphone: *

• Camera/webcam: Device component that is a built-in camera and microphone; provides both audio and visual capture - specialized drivers/software necessary.

• Touchscreen/digitizer: Converts touchscreen graphical (writing) input (e.g., from a stylus) into digital signals for computer use.

• Inverter: Converts DC power (from your laptop) to AC power for CCFL/LED backlight use.

  • Flashlight test for a failed backlight: hold a flashlight directly toward a dim screen and look closely - faint image = faulty backlight. You may need to replace the inverter or even the entire LCD.

LCD Displays

• Definition and Functionality

  • LCD (Liquid Crystal Display) uses a series of liquid crystals and color filters with a backlight to create images on the screen.

  • Lightweight, power-efficient, and cost-effective for laptops.

Advantages of LCD Displays

• Lightweight: Easier to carry and manage within laptops.

• Low Power Usage: Conserves battery life, making laptops more efficient.

• Cost-Effectiveness: Cheaper to produce compared to other display technologies.

Disadvantages of LCD Displays

• True Black Limitations: Difficulty in achieving true black since the backlight must shine through the crystals.

• Backlight Dependency:

  • Different types of backlights (fluorescent, LED) can fail, complicating repairs.

  • Replacement of backlights can be challenging and costly.

Main Types of LCD Technologies

1. TN (Twisted Nematic) LCD

   • Excellent response times suitable for fast-moving graphics (gaming).

   • Poor viewing angles, with color inversion from side views.

   • Optimal viewing requires direct line of sight to the screen.

2. IPS (In-Plane Switching) LCD

   • Superior color representation; ideal for graphics and design work.

   • More expensive than TN technology but offers improved visual quality.

3. VA (Vertical Alignment) LCD

   • Balanced performance between good color representation and moderate response times.

   • Acts as a middle ground between TN and IPS technologies.

OLED Displays

• Definition: Organic Light Emitting Diode displays do not require a backlight.

• Structure: Uses organic material to emit light when powered, leading to thin and lightweight designs.

• Advantages:

  • Exceptional color accuracy and vibrant displays.

  • Commonly used in tablets, smartphones, and smart devices.

Wireless Network Integration

• Antenna Placement: Laptops utilize their top displays for mounting wireless antennas.

• Types of Networks: Compatible with 802.11, Bluetooth, and other wireless technologies.

• Complications in Repairs:

  • Replacing displays requires reconnecting both video components and antenna wires.

Webcam and Microphone Features

• Integrated Webcams: Found at the top of many laptop displays for video capture.

• Usage: Ideal for video conferencing and online communication, enhancing accessibility for meetings (e.g., Zoom calls).

Backlight Technologies

• Types of Backlights:

  • Older laptops might use CCFL (Cold Cathode Fluorescent Lamp), which consumes more power.

  • Newer models typically utilize LED lights, which are thinner and more energy-efficient, sometimes referred to as LED displays (LED-backlit LCD).

Identifying Backlight Failure

• Flashlight Test: Shine a flashlight on the screen. If the display shows images, the issue may be with the backlight, not the display itself.

• CCFL and Inverter: If using CCFL, the inverter may need replacement to restore functionality.

Hybrid Device Functionality

• Stylus Input: Some laptops support high-resolution input from a stylus, converting analog signals to digital.

• Digitizer Technology:

  • Digitizers can facilitate both stylus and touchscreen input, offering versatile interaction methods on the device.