← IGCSE Computer Science Paper 1

Comparing LCD and DLP projectors

Both projectors show an image on a screen. LCD shines light through liquid crystal panels; DLP bounces light off tiny mirrors (micromirrors). They differ in sharpness, colour, size and cost.

Part of: IGCSE Computer Science 0478 — 3.2 Input and Output Devices — Module 24

Understanding Comparing LCD and DLP projectors in IGCSE Computer Science Paper 1

What it does: DLP projectors are generally more compact and portable, and their micromirrors give a sharp image. LCD projectors tend to cost less than DLP projectors, so they are a common budget choice. DLP stands for Digital Light Processing. Its chip is covered in micromirrors that tilt to reflect light towards the lens or away from it. An LCD projector passes light from a lamp through liquid crystal panels. A DLP projector bounces light off mirrors instead. Both types are output devices that project an enlarged image onto a screen or wall. They differ in the technology used inside. The gaps between the pixels on LCD panels can show up as a faint grid. DLP mirrors are packed very closely, so DLP images tend to look smoother and sharper.

Common mistakes: An LCD projector shines light through liquid crystal panels. Tiny mirrors (micromirrors) are used by DLP projectors, so line 4 should say liquid crystal panels. A DLP projector makes its image with millions of tiny mirrors (micromirrors). Liquid crystal panels belong to LCD projectors, so parts should be "micromirrors".

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This module's key terms are also in a printable crossword (Modules 262–272) and word search (Modules 262–282).

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Learning
Duo
Which type of projector makes its image using thousands of tiny mirrors?
DLP projectorLCD projector
Matches
A DLP projector shines light through liquid crystal panels to make the image.
↓
This describes an LCD projector. A DLP projector uses tiny micromirrors that reflect light, not liquid crystal panels.
Applying
Meanings
Term
LCD vs DLP
Meaning
Both projectors show an image on a screen. LCD shines light through liquid crystal panels; DLP bounces light off tiny mirrors (micromirrors). They differ in sharpness, colour, size and cost.
Practice
LCD: light passes through liquid crystal panels
Testing
Gaps
DLP.light ← "reflects off "
Check Answer
Spots
3 print("Light passes through")
4 print("tiny mirrors")

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Quick Questions

1. Which type of projector makes its image using thousands of tiny mirrors?
A. DLP projector ✓
B. LCD projector
DLP stands for Digital Light Processing. Its chip is covered in micromirrors that tilt to reflect light towards the lens or away from it.
2. Which type of projector shines light through liquid crystal panels?
A. LCD projector ✓
B. DLP projector
An LCD projector passes light from a lamp through liquid crystal panels. A DLP projector bounces light off mirrors instead.
3. Which statement about LCD and DLP projectors is true?
A. Both display an image on a screen ✓
B. Only DLP projectors can display an image on a screen
Both types are output devices that project an enlarged image onto a screen or wall. They differ in the technology used inside.
4. What is a micromirror in a DLP projector?
A. A tiny lens that magnifies the image
B. A tiny mirror that tilts to reflect light ✓
Each micromirror tilts to send light towards the lens (a bright pixel) or away from it (a dark pixel).
5. A teacher carries a projector between classrooms every day. Which type is usually the better choice for portability?
A. LCD projector, because it is always smaller and lighter
B. DLP projector, because it is usually smaller and lighter ✓
DLP projectors tend to be more compact and lightweight, so they are easier to carry around. LCD projectors are usually bulkier.

Match the Pairs

LCD panels → Light is shone through liquid crystal panels to make the image, which is then projected onto the screen
Micromirrors → Thousands of tiny mirrors tilt to bounce light towards the screen or away from it to build the image
A projector that is usually smaller and lighter and gives a sharper image, so it is easy to carry between rooms → DLP projector
A projector that is usually cheaper to buy, which suits a school with a small budget → LCD projector
A DLP projector shines light through liquid crystal panels to make the image. → This describes an LCD projector. A DLP projector uses tiny micromirrors that reflect light, not liquid crystal panels.
LCD and DLP projectors make the image in exactly the same way, so the choice does not matter. → They make the image differently (panels versus micromirrors), so sharpness, colour, size and cost differ and the choice does matter.

Key Term

LCD vs DLP
Both projectors show an image on a screen. LCD shines light through liquid crystal panels; DLP bounces light off tiny mirrors (micromirrors). They differ in sharpness, colour, size and cost.

Fill in the Blanks

1. DLP.light ← "reflects off micromirrors"
Hint: Type the name of the tiny mirrors that a DLP projector uses to bounce light.
2. LCD.light ← "passes through liquid crystal panels"
Hint: Type the two-word material that makes up the panels in an LCD projector.
3. IF portable = TRUE THEN projector ← "DLP" ENDIF
Hint: Type the projector type that is usually smaller and lighter to carry.
4. IF sharpness = "high" THEN projector ← "DLP" ENDIF
Hint: Type the pseudocode keyword that starts a selection (decision).
5. IF budget = "low" THEN projector ← "LCD" ENDIF
Hint: Type the projector type that is usually the cheaper choice.

Spot the Error

Question 1
A projector = "LCD"
B if projector == "LCD":
C print("Light passes through")
D print("tiny mirrors")
Line D — An LCD projector shines light through liquid crystal panels. Tiny mirrors (micromirrors) are used by DLP projectors, so line 4 should say liquid crystal panels.
Question 2
A projector = "DLP"
B parts = "liquid crystals"
C print(parts)
Line B — A DLP projector makes its image with millions of tiny mirrors (micromirrors). Liquid crystal panels belong to LCD projectors, so parts should be "micromirrors".
Question 3
A dlp_cost = "higher"
B lcd_cost = "higher"
C print(lcd_cost, dlp_cost)
Line B — LCD projectors are usually cheaper than DLP projectors, so lcd_cost should be "lower" to show the cost difference.
Question 4
A projector = "DLP"
B size = "large and heavy"
C print(projector, size)
Line B — DLP projectors are usually smaller and lighter, which makes them more portable. Line 2 should say "small and light".
Question 5
A lcd = {"cost": "low"}
B dlp = {"cost": "high"}
C cheaper = "LCD"
D print(cheaper, "costs more")
Line D — The LCD projector is the cheaper one, so the message should say it costs less, not more. Line 4 should print "costs less".

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