“Is an optical breadboard or table needed for my task, or what other options do I have?” This is a question you may face in your optics lab work.
The following discussion may help you answer that question. Unfortunately there is no simple answer which can be invoked for all cases, because the real answer is: “It depends on your application!” Hopefully the following will at least point you in the correct direction.
First, Definitions:
Optical breadboards are intended as relatively portable platforms for building an optical setup on a flat surface. They may be relocated and placed on top of an existing table for convenience of use. Some vendors offer support frames with metal legs to hold the breadboards, ready for use. Many manufacturers offer these breadboards in a variety of sizes and types of construction, including solid metal plates or honeycomb-structured breadboards, with magnetic or non-magnetic surfaces, and with or without a tapped hole pattern in the “top” surface. Their flatness, stiffness, and vibration-damped characteristics vary a lot, but in general, one can find a combination of specs suitable for many applications.
Optical tables are generally not as portable (as breadboards) but may provide the user with better performance (i.e. flatness, stiffness, and vibration-damped characteristics) for measurements or fabrication tasks which require these. These can be metal tables or they may utilize granite slabs. For a measurement etc. requiring a work surface with extreme flatness, or stiffness, and the highest degree of vibration damping, a granite slab optical table is often the best. These are offered in various thicknesses with static or dynamic support legs (e.g. dynamic air-piston floating legs requiring an air source). Granite slab tables are not “portable” in the normal sense, and often require an industrial forklift or hydraulic lifting manual dolly to move them at all! Prices for optical tables vary widely but can become extremely costly, depending on your application.
The critical question to ask is this: “Do I really need an optical breadboard or perhaps an optical table for my application.”
A quick reality check:
If you are fortunate to work in a facility which already has this equipment or has a robust capital equipment budget and management will gladly support your optics lab needs, you probably do not need to read further; just go buy any breadboards or optical tables you need!
It happens; for quite a while I worked in an optics manufacturing plant which had an abundance of metal and granite optical tables, and a few of them were actually unused and available for my testing purposes. Not everybody is that lucky! For some people, the above question may be a significant factor in their budgetary decision making.
The answer to this question is most certainly dependent on your optical application. Let’s look at the easy one first. Suppose you need to do interferometric measurements or any type of testing in which optical wavefronts will be analyzed with or without computer software assistance. Typically, a person using an interferometer or other wavefront-sensing equipment will quickly discover that attempting to do this work on your spare office desk (you get the point) will result in major frustration and a great deal of wasted time. Perhaps if your goal is a one-time test, and you can optimize your lab environment, say by testing in the middle of the night when nobody else is working in the building and the building’s HVAC system is turned off, you might be able to get useful results. Realistically, a person walking across the floor (not even your floor) or the operating HVAC system can ruin interferometric measurements.
When repetitive interferometric measurements must be made, as in optical manufacturing or research work, and “your time is money” applies, users of these interferometer-based techniques find that their equipment needs to be located on an optical table with suitable vibration damping specs, and often it will be apparent that only a heavy granite-slab table on dynamic (air) support legs will be up to this task. It depends on your building and environment, but this is a reasonable generalization. I actually observed a test procedure using a commercial interferometer on a granite bench which had dynamic air-piston legs go “off the rails” because a component of the test system was vibrating in resonance with some unknown frequency stimulus coming from the building, in spite of all the good attempts to isolate the test from external inputs. We stiffened that component and the problem was solved.
There are many optics lab or testing applications which do not require the maximum-effort approach to supporting equipment. If your work is not especially vibration sensitive, you may find that an optical breadboard on a wooden bench is adequate for your task. Breadboards are available with or without a tapped hole pattern provided in the mounting surface. These can be made to accept either imperial (inch) or metric bolts. Patterns vary and can be made to order in some cases.
The tapped hole pattern concept is based on the idea that you may wish to attach optomechanical components in various places on the surface of the breadboard, so the manufacturer provides a large number of holes for you to use. (The idea is similar to that found in electronic breadboards used to prototype electronic circuits. Different holes of course.) Do you actually need a pre-drilled and tapped hole pattern? That is up to you. I personally found that too often, the regularly spaced tapped holes (usually 1/4-20 sized) were never in the right places when I needed to attach optomechanics. Then, one has to get clever about attaching those components which have slots or holes for bolts in specific places, and use clamps or other tricks to hold the components exactly where you wish them to be on the plate! You might find that it is easier for you to get a breadboard with no holes, and install the holes exactly where you need them for your specific testing equipment.
The same idea applies to optical tables (benches). I worked on granite tables which had holes drilled in the top granite surface and threaded inserts installed to accept large bolts. These held test equipment on the table. Of course this is good for “permanent” type equipment setups and not so good for granite benches which may be used for other purposes in the future! How robust is your budget; that’s the question?
Alternatives to commercial breadboards and tables:
If you can’t afford a commercial optical table or perhaps you decide you don’t need a breadboard, the alternatives are simple and numerous. You could buy a basic optical rail with some carriages to fit it; several vendors offer these in different sizes. The choice depends on your application. Clamp or bolt the rail to any wooden table. At least the rail gives you a relatively straight line of sight and the carriages can be moved to accommodate your optical equipment.
If you do not require the flexibility of smoothly-sliding carriages for optics, you can even use a simple aluminum tooling plate of adequate length and width, and drill and tap some holes to fasten brackets or any optomechanical components you need in the appropriate places along the tooling plate. This means you do the optical alignment for yourself, but that is sometimes not difficult.
The simplest and least expensive route is to use wooden rails and blocks you fabricate yourself to hold optomechanical components. Some people will consider this idea too radical to even consider. The truth is, it really depends on your application and testing work. If you anticipate a one-time only setup for a test, and your optical alignment or system precision is not that stringent, the wooden support idea is not that silly! It offers an inexpensive and very flexible method of performing some optical measurements or testing a design concept; I have done this successfully in the past. It can work. Incidently, wood blocks can provide low-expansion dimensional stability for changing temperature in a room, depending on the wood.
I once used blocks of Eucalyptus robusta wood to support a large aluminum tooling plate upon which I installed and aligned optical equipment, for ultimate use on a large telescope. That plate and everything on it ultimately was attached to a Blanchard-ground instrument surface on an observatory telescope after alignment. The blocks of wood held the plate and equipment above an optical table while an alignment telescope mounted on the table looked up through an aperture in the center of the plate by means of a beam folding mirror bolted onto that table. The temperature of the room was uncontrolled and fluctuated somewhat. The work took three weeks to complete. During that time, only minor optical alignment adjustments (on the order of ten seconds of arc or less) were needed to correct for inadvertent movement of equipment, either because of temperature fluctuations or vibration. Those blocks of Eucalyptus robusta wood were used with the grain of the wood oriented in the vertical direction.
It is my hope that this brief non-mathematical discussion will help you decide whether you need to have an optical breadboard or optical table for your task. Perhaps it will be a starting point for contemplating this question in light of your intended work.
Optics Lab Tips and Tricks 