physics

Optical manufacturing and testing

Optical manufacturing and testing is a physics 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 Optical manufacturing and testing rather than just read about it. In short: Optical manufacturing and testing is the process of manufacturing and testing optical components. It spans a wide range of manufacturing procedures and optical test configurations.

Key takeaways

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

Reference excerpt

Optical manufacturing and testing is the process of manufacturing and testing optical components. It spans a wide range of manufacturing procedures and optical test configurations. The manufacture of a conventional spherical lens typically begins with the generation of the optic's rough shape by grinding a glass blank. This can be done, for example, with ring tools. Next, the lens surface is polished to its final form. Typically this is done by lapping—rotating and rubbing the rough lens surface against a tool with the desired surface shape, with a mixture of abrasives and fluid in between. Typically a carved pitch tool is used to polish the surface of a lens. The mixture of abrasive is called slurry and it is typically made from cerium or zirconium oxide in water with lubricants added to facilitate pitch tool movement without sticking to the lens. The particle size in the slurry is adjusted to get the desired shape and finish. Types of lapping include planetary lapping, double-sided lapping, and cylindrical lapping. During polishing, the lens may be tested to confirm that the desired shape is being produced, and to ensure that the final shape has the correct form to within the allowed precision. The deviation of an optical surface from the correct shape is typically expressed in fractions of a wavelength, for some convenient wavelength of light (perhaps the wavelength at which the lens is to be used, or a visible wavelength for which a source is available). Inexpensive lenses may have deviations of form as large as several wavelengths (λ, 2λ, etc.). More typical industrial lenses would have deviations no larger than a quarter wavelength (λ/4). Precision lenses for use in applications such as lasers, interferometers, and holography have surfaces with a tenth of a wavelength (λ/10) tolerance or better. In addition to surface profile, a lens must meet requirements for surface quality (scratches, pits, specks, etc.) and accuracy of dimensions.

Fabrication techniques Glass blank manufacturing Batch mixing Casting techniques Annealing schedules and equipment Physical characterization techniques Index of refraction measurements and calculation of melt pedigree Diamond shaping techniques Diamond wheel curve generation processes and equipment Diamond edging processes and equipment Loose grit fabrication techniques: Rough grinding Fine grinding Polishing and figuring Glass moulding techniques Precision glass moulding Unconventional techniques include single-point diamond turning (SPDT) and magnetorheological finishing (MRF).

Free-abrasive grinding Free-abrasive grinding is a technique to grind down the surface of a material before polishing. It involves the use of small particles of grit to grind away small chips of material from the surface of an optical workpiece. The grit particles are known as free abrasives. The particles are added to a liquid slurry, which goes between a grinding plate and the material. Sliding motions between the grinding plate and the material are used. After grinding, there is a small amount of surface roughness, which is based on the size of the grit. There is also a small amount of fracturing below the surface of the material, known as subsurface damage (SSD). To reduce the amount of surface roughness and subsurface damage, additional grinding at a smaller grit size can be done. Typically, two or three stages of grinding are used, with the second and third stages having a size that is decreasing. For example, a typical set of grit stages is 30 micrometer, then 15 micrometer, then 9 micrometer. An alternate set of typical grit stages is 20 micrometer, then 12 micrometer, then 5 micrometer. Types of abrasives include aluminium oxide, industrial diamond, and silicon carbide. Diamond is typically only used for grinding down very hard materials, or for certain crystals.

Polishing Optics are polished in a slurry of abrasive particles, a fluid carrier, and optional additives. Types of abrasive particles that can be used include cerium(IV) oxide, diamond, aluminum oxide, and colloidal silica. Optional additives include suspension agents, lubricants, and detergents.

Materials There are various materials that can be used for optical components, including various types of glass, fused silica, silicon, and crystal quartz. Calcium fluoride (CaF2) can be used as an optical material, although it is easily fractured and scratched. Materials for infrared optical components include zinc selenide (ZnSe), zinc sulfide (ZnS), and gallium arsenide (GaAs).

Specifications The specifications for optical components vary based on their type: Specifications for prisms include pyramidal error, beam path, beam displacement and deviation, base angle, roof edge chips, wavefront, and polarization. Specifications for aspheric lenses include base radius with tolerance, conic and polynomial coefficients, best-fit sphere reference, sag table reference, sag error tolerance, slope errors versus bandwidth, wavefront per specified test, tilt, and decenter. Optical coating specifications include apertures, reflection, transmission, absorption, phase shift, adhesion, abrasion resistance, and damage threshold. In order to avoid the irrecoverable loss of going under minimum thickness, opticians strive to meet all other specifications for an optical component at the maximum allowable thickness within tolerance.

Surface quality

Surface quality is the condition of the surface of an optical component. It indicates the presence of imperfections, such as scratches and pits. It is typically rated according to scratch-dig (S-D) specifications. Standards for specifying surface quality include the U.S. Military Performance Specification MIL-PRF-13830B and ISO 10110. MIL-PRF-13830B was formerly MIL-O-13830a. Other standards include MIL-C-48497a and MIL-F-48616, which are formally inactive and apply only to coatings. All three of these military standards lack specifications for statistical surface parameters, such as root-mean-square roughness, slope error, and ripple. An extension and improvement to MIL-PRF is the ANSI/OEOSC OP1.002 standard.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Optical manufacturing and testing

Start with the simplest possible case. Write down what Optical manufacturing and testing claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, 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 Optical manufacturing and testing 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 Optical manufacturing and testing 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 Optical manufacturing and testing

In research: Optical manufacturing and testing appears in physics 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 Optical manufacturing and testing 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: Optical manufacturing and testing is common in secondary-school and first-year university syllabi. It links to neighbouring topics Glass engineering and science, Optics, Production and manufacturing by product, so understanding it makes those chapters shorter.
In everyday life: Look for Optical manufacturing and testing 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Optical manufacturing and testing in 20 minutes

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

Frequently asked questions

What is Optical manufacturing and testing in simple terms?

Optical manufacturing and testing is the process of manufacturing and testing optical components. It spans a wide range of manufacturing procedures and optical test configurations.

Why does Optical manufacturing and testing matter?

Because it connects several physics 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 Optical manufacturing and testing?

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 Optical manufacturing and testing.