science

Wavefront coding

Wavefront coding 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 Wavefront coding rather than just read about it. In short: In optics and signal processing, wavefront coding refers to the use of a phase modulating element in conjunction with deconvolution to extend the depth of field of a digital imaging system such as a video camera. Wavefront coding falls under the broad category of computational photography as a technique to enhance the depth of field.

Key takeaways

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

Reference excerpt

In optics and signal processing, wavefront coding refers to the use of a phase modulating element in conjunction with deconvolution to extend the depth of field of a digital imaging system such as a video camera. Wavefront coding falls under the broad category of computational photography as a technique to enhance the depth of field.

Encoding The wavefront of a light wave passing through the camera system is modulated using optical elements that introduce a spatially varying optical path length. The modulating elements must be placed at or near the plane of the aperture stop or pupil so that the same modulation is introduced for all field angles across the field-of-view. This modulation corresponds to a change in complex argument of the pupil function of such an imaging device, and it can be engineered with different goals in mind: e.g. extending the depth of focus.

Linear phase mask Wavefront coding with linear phase masks works by creating an optical transfer function that encodes distance information.

Cubic phase mask Wavefront Coding with cubic phase masks works to blur the image uniformly using a cubic shaped waveplate so that the intermediate image, the optical transfer function, is out of focus by a constant amount. Digital image processing then removes the blur and introduces noise depending upon the physical characteristics of the processor. Dynamic range is sacrificed to extend the depth of field depending upon the type of filter used. It can also correct optical aberration. The mask was developed by using the ambiguity function and the stationary phase method

History The technique was pioneered by radar engineer Edward Dowski and his thesis adviser Thomas Cathey at the University of Colorado in the United States in the 1990s. The University filed a patent on the invention. Cathey, Dowski and Merc Mercure founded a company to commercialize the method called CDM-Optics, and licensed the invention from the University. The company was acquired in 2005 by OmniVision Technologies, which has released wavefront-coding-based mobile camera chips as TrueFocus sensors. TrueFocus sensors are able to simulate older autofocus technologies that use rangefinders and narrow depth of fields. In fact, the technology theoretically allows for any number of combinations of focal points per pixel for effect. It is the only technology not limited to EDoF (Extended-Depth-of-Field).

References

External links Wavefront coding finds increasing use (Laser Focus World)

Worked examples

Example 1 — a first encounter with Wavefront coding

Start with the simplest possible case. Write down what Wavefront coding 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 Wavefront coding 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 Wavefront coding 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 Wavefront coding

In research: Wavefront coding 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 Wavefront coding 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: Wavefront coding is common in secondary-school and first-year university syllabi. It links to neighbouring topics Signal processing, so understanding it makes those chapters shorter.
In everyday life: Look for Wavefront coding 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 Wavefront coding in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Wavefront coding 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 Wavefront coding out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Wavefront coding in simple terms?

Why does Wavefront coding 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 Wavefront coding?

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 Wavefront coding.