computer science

LS-R

LS-R is a computer 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 LS-R rather than just read about it. In short: LS-R, or the Layer-Selection-Type Recordable Optical Disk, is the term coined by Hitachi in 2003 for a next-generation optical disc technology which allows much larger data storage densities than DVD, HD DVD or Blu-ray Disc, by allowing the use of many data layers in a single disc. In previous optical disc technologies, relatively few data layers can be incorporated in a single disc, since the reflections from the d…

Key takeaways

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

Reference excerpt

LS-R, or the Layer-Selection-Type Recordable Optical Disk, is the term coined by Hitachi in 2003 for a next-generation optical disc technology which allows much larger data storage densities than DVD, HD DVD or Blu-ray Disc, by allowing the use of many data layers in a single disc. In previous optical disc technologies, relatively few data layers can be incorporated in a single disc, since the reflections from the different layers interfere with each other. However, in LS-R, only the layer of interest generates a reflection, meaning that very many layers can theoretically be stacked in the same disc. This feat is accomplished by an electronic "selection" mechanism, whereby each data layer is coated with electrodes and only the electrodes associated with the layer of interest are activated. This activation changes the "selected" data layer from being transparent to being reflective or opaque, thus it can be addressed.

Technology In the Hitachi implementation, LS-R technology utilizes an electrochromic film, for example of tungsten oxide or an organic material to accomplish the optical change. A two-layer feasibility prototype has been demonstrated, and it was estimated that a 20-layer CD-sized disc could provide 1 terabyte (TB) of data capacity, with each layer containing 50 gigabytes (GB). Electrical activation of layers has been achieved with transparent ITO electrodes, and a contactless power supply has been developed in order to allow long-term operation, and given that the disc is spinning at several thousand revolutions per minute for a long time, the disk could technically run for weeks at a time.

Commercial product No plans or timeline for the development of a commercial product have been released. It is possible that this technology, while interesting, will remain in the realms of research, either because it is superseded by an alternative technology (such as holographic storage or another 3D optical data storage variant), or because it can not be made to be economically viable. The need for the disc to be meticulously constructed from many layers of different materials, and the need for the drive to be able to electrically address each layer specifically, may make this solution too expensive for commercialization. In the next generation, the LS-R disk may compete with other next-generation optical disc formats, such as the Holographic versatile disc and Protein-coated disc formats.

References

Illustrations

Worked examples

Example 1 — a first encounter with LS-R

Start with the simplest possible case. Write down what LS-R claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer 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 LS-R 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 LS-R 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 LS-R

In research: LS-R appears in computer 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 LS-R 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: LS-R is common in secondary-school and first-year university syllabi. It links to neighbouring topics Audiovisual introductions in 2003, Rotating disc computer storage media, Upcoming products, so understanding it makes those chapters shorter.
In everyday life: Look for LS-R 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 LS-R in 20 minutes

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

Frequently asked questions

What is LS-R in simple terms?

Why does LS-R matter?

Because it connects several computer 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 LS-R?

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 LS-R.