Clarification re: Optical Lens

[alanruttenberg]

Is this term intended to denote a single lens, or a multiple lens assembly like a telephoto lens.

[cameronmore]

As it's defined, I now see the ambiguity (Optical Lens = An Optical Instrument that is designed to focus or disperse a beam of light entering the lens by means of refraction.). The benefit to making 'Material Artifact' a subclass of 'Material Entity' is that we can speak about 'gappy' artifacts, like wireless ear buds, but it leads to this sort of problem.

If the entire optical instrument is being treated as a single piece of scientific equipment, then one Optical Lens may suffice even if there are multiple pieces of glass in the chamber which holds them in a particular configuration. If a finer level of granularity is needed, then it may be an Optical Instrument which has at least two Optical Lens parthood relations.

When contrasted with other artifacts, like Catadioptric Telescope (An Optical Telescope that is designed to aid in the observation of spatially distant Objects by means of collecting and focusing visible light through the use of a combination of Lenses and Mirrors to form an enhanced image of the Object.), it seems like Optical Lens definitely refers to just a single lens, a solid object which may be affixed in some larger instrument.

I am not sure what's best.

[alanruttenberg]

Probably there are uses for both. I think I need the one that has multiple lenses, so if this term is for a single piece of glass, consider this a request for the assembly which possibly includes multiple lenses.

[cameronmore]

Would Optical Instrument work instead of adding optical assembly (or optical train, as Wikipedia calls it)?

Optical Assembly = An Optical Instrument that has multiple Optical components (Instruments?) as parts, such as a mirror or lens. Comment; these components are typically affixed in a cylindrical fashion. Definition source; https://en.m.wikipedia.org/wiki/Optical_train. Alternative label; Optical Train.

Telescopes and other artifacts like them often all have Optical Assemblies as parts, usually called an 'optical tube assembly'.

[mark-jensen]

This makes sense to me. You'll also need to redefine 'optical lens' to clearly only include single lenses.
https://en.m.wikipedia.org/wiki/Lens

[cameronmore]

New proposed definition:

Optical Lens = An Optical Instrument that is designed to focus or disperse a beam of light entering the lens by means of refraction which consists of a single material.

Only the last clause 'which consists of a single material' is new. This is the same language that is used for 'prism'. Should we add an alternative label "Simple Optical Lens" which is the Wikipedia defined term for an optical lens which consists of one lens rather than multiple (complex lenses)? Also, should the label change or just consider adding an alternate label? This begs the question 'if we're adding simple lens, should we add complex to cover the bases'.

Happy to make a PR with these changes and @mark-jensen we can discuss merging to master or merging to a developmental branch

[alanruttenberg]

The single material criterion doesn't work because some lenses have coatings which are made of different materials

[cameronmore]

Optical Lens = An Optical Instrument that is designed to focus or disperse a beam of light entering the lens by means of refraction which consists of a single Object.

Is there a better way to talk about the fact that this is an object, maybe without mentioning bfo:Object in the definition? Single crafted portion of material?

[alanruttenberg]

The problem with that is that it's reasonable to consider the lens assembly as an object as well. I'm not yet sure about what a better definition is.

I think optical lenses are always glass, crystal, or plastic. But we don't have a constitution relation so it would need to be a defined class, something like

A glass, crystal, or plastic object with optical lens function
Then:
Optical lens function a function realized by focusing or dispersing light by means of refraction

The lens assembly would have the same function. Lens assembly is distinguished from single lens by including the mounting/housing of the (one or more) lenses. Maybe lens system would be a better name.

Optical lens is distinguished from https://en.wikipedia.org/wiki/Magnetic_lens

[cameronmore]

We can't just say:

Optical Lens = An Optical Instrument that is designed to focus or disperse a beam of light entering the lens by means of refraction which consists of a portion of glass, plastic, or crystal.

And the implied semantics is that there is an act of manufacturing that has as input either glass, plastic, or crystal and as output an optical lens?

Optical Assembly = An Optical Instrument which is designed to focus or disperse a beam of light entering the lens by means of refraction which has one or more Optical Lenses as parts or something along those lines? Perhaps the function of the assembly is just to store the lens and the lens has the focusing or dispersing function

[alanruttenberg]

The definitions would have optical lens be subclass of optical assembly, which is fine but needs to be acknowledged. Both the assembly and the single have those inputs, so it doesn't discriminate. One might think to say "only" but that's probably wrong. I think the mounts are a better discriminator.

Optical Assembly: An Optical Instrument which is designed to focus or disperse a beam of light entering the assembly by means of refraction which has one or more optical lenses as parts as well as material to hold or align the lens parts.

You could replace "material" with the more colloquial "hardware"

Unfortunately, I realize we'll have to hedge a bit using "consists primarily of a portion of glass, plastic, or crystal." to allow for coatings. Or mention the possibility of coatings explicitly.

[alanruttenberg]

Both, BTW, can have skos:altLabel "lens"

[cameronmore]

Are the classes parent-child or sibling? An Optical Assembly has part some Optical Lens but not all Optical Lenses have part some Optical Assembly, and certainly not all Optical Lenses (which are now specifically just a portion of glass or something similar) have the cylindrical parts necessary for the entire assembly. In other words, a lens by itself does not constitute a lens assembly?

Optical Lens = An Optical Instrument that is designed to focus or disperse a beam of light entering the lens by means of refraction which consists primarily of a portion of glass, plastic, or crystal.
Alternative label = Lens

Optical Assembly = An Optical Instrument which is designed to focus or disperse a beam of light entering the assembly by means of refraction which has one or more Optical Lenses as parts as well as material to hold or align the lens parts.
Alternative label = Optical Train
Alternative label = Lens

I would note that one can imagine an optical assembly which has been made with simple metal piping, and hardware might allow ambiguity to creep in if someone down the line asks 'are you using hardware in a consistent manner?' but I'm open to it.

[alanruttenberg]

I went back and looked at the Wikipedia article. Maybe we should follow their lead. They effectively subclass lens to simple and compound lens. The properties I care about are common to both, e.g. focal length, radial distortion, etc.

So the original term is defined in terms of function and the subclasses in terms of material property and parts.

A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis.

Sorry this is going in a circle, but the discussion has helped clarify.

[alanruttenberg]

By phrasing the initial question as a choice between two alternatives, I distracted us an answer that it is both.

[cameronmore]

This has been a good discussion, I agree, so create two new subclasses to Optical Lens, or break optical lens into two classes/create a new one for complex optical lenses? Also, it seems like we should adopt their use of 'transparent' so as to not to worry about coatings and create the 'plastic, glass, or crystal' enumeration, but I think that would be fine anyway in this case. I was also thinking we should adopt the caveat that it's usually arranged along a common axis, but I think that might be overkill and only live in an rdfs:comment

Optical Lens = simple lens

Optical Assembly = a complex lens

[alanruttenberg]

Either break into two subclasses, or add a scope note and examples making clear that the existing term applies to both. I don't have an immediate need for the subclasses - the properties I am working on apply equally to both.

[swartik]

In one of my favorite childhood SciFi novels, Jules Verne's The Mysterious Island, engineer Cyrus Smith makes a firestarting lens from two watch crystals filled with water. The proposed definitions for "Optical Lens" are broad enough to include this device, except that water is as important a component as crystal. The comments so far seem like an Optical Lens is the sort of artifact that could be attached to a camera or used in a telescope, not a seat-of-the-pants gizmo. If it can be the latter, its composition is unimportant so long as it focuses light. If it can be the former, I advocate an elucidation stating what an Optical Lens is not.

[cameronmore]

@swartik it seems like this would be a case where the disposition of water (combined with dispositions of the crystals) creates the same effect as a light concentrating function. The larger device would certainly be an instance of an Optical Instrument which has some light concentration function to start fires. A larger device may have a function while its parts are just mere dispositions. Should we opt for the fact that a lens must be made of a material in which a transparent quality inheres to include your example?

Optical Lens = An Optical Instrument that is designed to focus or disperse a beam of light entering the lens by means of refraction which consists primarily of a portion of transparent material. [or portion of material in which a transparent quality inheres?)
Elucidation = This is intended to represent single lenses lens, which may be parts of more complex optical assemblies.

Optical Assembly = An Optical Instrument which is designed to focus or disperse a beam of light entering the assembly by means of refraction which has one or more Optical Lenses as parts as well as material to hold or align the lens parts.
Elucidation = This is intended to represent complex lens instruments which have multiple optical lenses as parts.

If we go with the above definitions, then the water lens classifies as an Optical Assembly, I like that rather than enumerating the possible types of material because the transparent quality is what motivates us to enumerate those particular materials.

@alanruttenberg if these definitions suffice, I will make coordinate with @mark-jensen to make sure we get it in the development pipeline and pulled in.

[alanruttenberg]

My latest proposal was that there be a parent class for the two, since that will let me capture the generality that properties like focal length apply to both. So something like the below (wordsmith as appropriate)

• Optical lens: keeps current definition
• Simple optical lens: An optical lens consisting of a single piece of transparent material
• Complex optical lens: An optical lens consisting of more than one simple optical lenses [usually arranged along a common axis]

This allows me to define focal length as a quality (or disposition - not sure) that inhering in some optical lens, instead of having to say it inheres in either an optical lens OR optical assembly.

[cameronmore]

I think that sounds fine, I'll let Mark weigh in.

My only hesitation is that such a classification builds semantics into a class rather than expanding the fact that there is some assembly which has two or more distinct lens parts, but because this seems to be the preferred and accepted way of classifying lenses in the optical domain, my concerned might not be relevant.

But it should be fine.