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Lightguide display

Lightguide display is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Lightguide display rather than just read about it. In short: A Lightguide display (also known as an edge-lit display) is an obsolete electronic mechanism which was used for displaying alphanumeric characters in electronic devices such as calculators, multimeters, laboratory measurement instruments, and entertainment machines such as pinball games. Construction It contains a set of sandwiched acrylic or clear plastic panels, each of which is engraved with a numeral or characte…

Lightguide display — main illustration
Lightguide display — illustration

Key takeaways

  • Lightguide display belongs to science; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Lightguide display to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Lightguide display from memory before moving on to harder problems.

Reference excerpt

A Lightguide display (also known as an edge-lit display) is an obsolete electronic mechanism which was used for displaying alphanumeric characters in electronic devices such as calculators, multimeters, laboratory measurement instruments, and entertainment machines such as pinball games.

Construction

It contains a set of sandwiched acrylic or clear plastic panels, each of which is engraved with a numeral or character to be displayed. Light from independently controlled incandescent bulbs passing into the edge of these panels reflects off the internal surfaces of the plastic. When the light encounters engraved digits, it is scattered, rendering a brightly illuminated digit or character.

History The principle of edge-lighting was discovered early and used for commercial signs. U.S. patent 1,139,723 for an "Electric edge lit sign" was filed on July 31, 1914, and granted in 1915. Other similar patents (1,707,965, 1,741,748, 2,082,724, 2,623,313) for illuminated signs were filed 1928-1948. But the need for digit read-out arose with electronic computers in the 1950s with many independent inventions, both in edge-lighting, nixie tubes and other technologies. U.S. patent 2,751,584 for an edge-lit multi-layer digit "Visual readout device" was filed on November 10, 1953, by inventor Carl L. Isborn of Hawthorne, California, for the National Cash Register Company and granted on June 19, 1956. For a similar invention of a "Visual in-line multi-symbol signal indicator", U.S. patent 2,766,447 was filed on July 7, 1954, by Wesley E. Woodson, Jr., El Cajon, and Jack I. Morgan of San Diego, California, and granted on October 9, 1956. U.S. patent 2,813,266 for an "Indicator device and means for mounting" was filed on January 9, 1956, by Andrew F. Kay, Covert B. Meredith, and Leonard M. Scholl of San Diego County, California, and granted on November 12, 1957. This patent describes a display of five digits next to each other, whereas the earlier two describe just a single digit.

The technology was rendered obsolete by the development of light-emitting diodes (LED) in the 1970s, though lightguide tubes are still used in electronics manufacturing, in situations where it is difficult to place an LED in the appropriate physical location on a display or bezel. In such cases, LEDs mounted on printed circuit boards are fitted with lightguides to channel light to the appropriate position. This employs the same principle used in optical fibers.

See also Nixie tube Optical fiber Waveguide (optics)

References

External links Mike's Electric Stuff: Display and Counting Tubes YouTube video showing a lightguide display in action

Illustrations

Lightguide display: A lightguide (edge-lit) display.
A lightguide (edge-lit) display.
Lightguide display: The Swedish electronic computer BESK, built in 1953, displayed 18 hexadecimal digits using edge-lit acrylic, the grey squares at the center of the green console.
The Swedish electronic computer BESK, built in 1953, displayed 18 hexadecimal digits using edge-lit acrylic, the grey squares at the center of the green console.
Lightguide display: Light guide LEDs using plastic light guides on a network switch
Light guide LEDs using plastic light guides on a network switch

Worked examples

Example 1 — a first encounter with Lightguide display

Start with the simplest possible case. Write down what Lightguide display claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Lightguide display before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Lightguide display ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Lightguide display

In research
Lightguide display appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Lightguide display in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Lightguide display is common in secondary-school and first-year university syllabi. It links to neighbouring topics Display technology, so understanding it makes those chapters shorter.
In everyday life
Look for Lightguide display outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Lightguide display in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Lightguide display means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Lightguide display out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Lightguide display in simple terms?

A Lightguide display (also known as an edge-lit display) is an obsolete electronic mechanism which was used for displaying alphanumeric characters in electronic devices such as calculators, multimeters, laboratory measurement instruments, and entertainment machines such as pinball games. Constructi…

Why does Lightguide display matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Lightguide display?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Lightguide display.

Tags

  • Display technology

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