Yaron [LaserOp]

Reference Points and engraving

Recommended Posts

This is a continuation of a few related topics that were previously discussed in emails (involving Me, Paul, Christian Laurent, and Robert Shanbaum), and mentioned on the last VEW meeting.

Since there are potential interested (and contributing) people outside of the email thread, it seems better to transfer this to the forum, so it will be possible for other members to view, and contribute, to the discussion.

Apart from #1 I don't have personal stakes in the matter, except for the confusion that can follow from #2, which at this point is solved for me outside of the DCS document.

So answers/discussion on #1 are needed, it's an open topic.

For the rest I think it's a good idea and important to handle, but they were possible discussed on VEW, so if everyone else is happy...

1. Engraving Reference for front side engraving

All of the above was for back-side engraving/marking. What about front side?

I strongly believe it couldn't be ER as-is, since there should be only one ER per lens in concept, it shouldn't change based on whether it's wanted for front or back (and it's not even possible to always tailor it even if a VCA Host wanted to).

On the other hand, so far in practice from our customers, whenever front-side/finishing engraving isn't done relative to frame (which it usually is, so doesn't matter so much), they expect it relative to FB. But from Christian, they report to use the PRP (Reference Point OC) as center for marking on the front side on a finishing block.  (So difference of FBOC__ )

So there are at least two different practices already in practice, and none of them actually says "Engraving" for when describing their Reference Point. There should be an explicit decision in the DCS. Is there to be a different new Reference Point? Should it be standardized on OC (and so the description of OC should mention it explicitly, or it should be mentioned explicitly in Marking Records)? Something else?

2. The new BE Reference Point, name

The new BE point ("Back Engraving Reference") is intended to be found from inspecting marks already engraved on the back side, and for PRP / OC to be derived from it.

So I think the name and description is currently incorrect and very confusing. "Engraving Reference" very much signals, on clean reading, it's going to be the reference point for engraving, not that it's a different reference point to be gleamed from engraving.

3. The new BE Reference Point, not commutative with other Reference Points, so should it be one or a different record?

So far the list of Reference Points are, to my understanding (?), commutative. SBBC__ + BCOC__ =  SBOC__ , etc... This would work even for connection labels not officially on the standard, I assume, so probably various LMS/VCA-hosts would be happy to "calculate" one if asked for.

But BE doesn't, because it's only useful to find OC, and required the additional BEOCA beyond the normal UP/IN sets for all other Reference Points. Since the usage, and potential errors, are very different from other Reference Points, maybe it shouldn't be on the list as a Reference Point? Or at least there should be something very clear in the definition to separate it.

Alternately, maybe I'm just wrong about the assumption of commutativity?  Is FBSGIN - BCSGIN + BCOCIN = FBOCIN ? And SBSGIN - BCSGIN + BCOCIN = SBOCIN ? And so then FBSGIN - BCSGIN - SBBCIN is the correct equivalent of FBSBIN ?

If yes, then it's a really really strong case that BE (or whatever it should be renamed to) should be differentiated from the Reference Points lists. It's a lone position that doesn't fit and doesn't behave like the rest.

If no (probably since SB and FB aren't on a parallel plane, so "- BCSGIN + BCOCIN" isn't valid from one starting position), then there is already a big problem, and which label is valid in which case is very much not clear from the list of Reference Points. So the Reference Points themselves have to be clearly and explicitly split into the different sets/groups, to it will be possible to get from the DCS which can't, and which can't, be connected.

Edited by Yaron [LaserOp]
Removed a few of the topics that were already closed on the email discussion, and were here more for info than need for discussion. Made the post seem too large and complicated, which could have reduced participation instead of getting it.

Share this post


Link to post
Share on other sites

The ENGMARK question was resolved in email.  You can simplify this post greatly by removing all of that, or at least putting it into it's own topic.  This is quite a lot for someone to read and respond to.  If you can't simplify and shorten it I'm afraid you won't get much feedback.

Share this post


Link to post
Share on other sites

Hi Yaron,

you mentioned above:

" answers/discussion on #1 are needed, it's an open topic. "

So, I tried to understand your concern #1, particularly regarding (from your message):

"On the other hand, so far in practice from our customers, whenever front-side/finishing engraving isn't done relative to frame (which it usually is, so doesn't matter so much), they expect it relative to FB. But from Christian, they report to use the PRP (Reference Point OC) as center for marking on the front side on a finishing block.  (So difference of FBOC__ )"

, please be more explicit for both sentences, particularly for the second one. 

- "from Christian": (when, where?)

- "they report" = who report ???

- "marking" =  engraving operation? (permanent marking, not inking)???

- "on the front side on a finishing block" = on the front side of a lens held on a finishing block ???

TY !

 

 

 

Share this post


Link to post
Share on other sites

Hi Yaron,

First, the suggested label is BEROC_ so actually the first letters are BER and not ER.

Front side is the easier case, and it is explained in the document A&R provided prior to the DCS request. I agree with you that there should be only one ER for each lens but that is still the case, at least as I understand it. Only one ER, that can appear on the front side or the back, not on both.

Personally, I currently don't see how these labels should affect the way we engrave the OC of the lens. It should only affect the description of the measuring points location on the front side of the lens (as defined in ISO/ANSI). These points should be described with reference to the back side engravings (in case they are on the back), and that is what the new suggested system is trying to define.

As you described, there is a chance that we missed the mismatch with some old labels. I pass your notes to our algorithm team for review. I will definitely share their conclusions when ready. Maybe we can have a phone call to exchange insights on that.

Thanks a lot for your notes and hope to see you in the next convention as well.

Haim S.

Share this post


Link to post
Share on other sites
On 10/25/2019 at 3:12 AM, christian.laurent said:

, please be more explicit for both sentences, particularly for the second one. 

- "from Christian": (when, where?)

- "they report" = who report ???

- "marking" =  engraving operation? (permanent marking, not inking)???

- "on the front side on a finishing block" = on the front side of a lens held on a finishing block ???

TY !

On one of the email from you, in the discussion before raising this on the forum, you sent:

Quote

Today, I got the confirmation from both our inking and our laser engraving project leaders that for applications on finished lenses, the reference point used in the ENGMARK definition is the PRP (‘OC’).

Which I took to mean that when your engravers or inkers need to mark, on finished lenses (so on a finishing block, so marking done on the front side of the lens), then the base position you use to detemine where anything is marked (e.g. with ENGMARK records), is 'OC' .

So for example if you have "ENGMARK=TXT;O;;R;F;F;17.00;1.00;;;1.00;"  , then under the current interpretation (as I understand from the quote above), your (for whatever "your" it is you covered in your email) systems will expect the "O" character to be marked on the front side of the lens, 17mm nasally from OC and 1mm above OC.

In contrast to, as I wrote, what is so far the expectation from the labs we have front-side marking on finished lenses for (usually for logos, safety marks, and such), which would be to engrave this 17mm nasally from FB and 1mm above FB.

( and of course in contrast to if this was "ENGMARK=TXT;O;;R;F;B;..." , where for engraving on the back side this would be, I think in any case, 17mm nasally from ER and 1mm above ER )

So the open question here is what should be the base/reference for engraving (regardless of whether it's permanent or not, as I think is currently the agreement for back-side marking as well) when it should be done on the front side.

For our (LaserOp) needs that is something that should be decided, since the DCS should be explicit on it, to avoid confusion (i.e. if already we have two vendors doing it differently, better to standardize now, while front-side marking is still in early days). But it's not urgent (I wouldn't delay the next version if there's no decision, though I'd strongly prefer there would be) because mostly (in practice, at least for our cases) the engraving in those cases is done relative to frame (e.g. all is type ENGMARK=MASK, where the in-layout objects are set to move relative to frame). So it's an important distinction in theory, but not yet in practice, for us, for just now.

Share this post


Link to post
Share on other sites

Haim,

Thank you for the response. What I posted here was a continuation of an email discussion following the 3.13 committee draft emailed by Paul on Sep 11. So I have not read any further later documentation, or modifications, since. If the change you mention was discussed on the VEW meeting, or correspondence in another circle, then it's great you bring it up here, and that's one of the points we decided to transfer this to the forum.

If the new point was changed (again, from that 3.13 committee draft) from BE to BER, then having it be a 3-letter position, while all the others are 2, does help with separating it from the rest, given the different handling. I think this should also be further separated in the DCS document by listing it separately from the other Reference Points, given that they generally share the same coordinate system, and this one doesn't.

And, again, I think the name is confusing and misleading, even supported by reading your email.

The thing is, there is the (by now long standing) Reference Point called ER, named "Engraving Reference". Which is where engraving/marking should be made from (base coordinate for engraving data). Where engraving done on the back side of the lens should be made from.

So a new Reference Position, BE or BER (worse for this purpose), named "Back Engraving Reference", is a confusing name. It's basically the name of that other older point, even though this one isn't the reference position for engraving. It is, as you write, just a way used to find OC from where the center of a previously-made back-side engraving seems to be, looked at from a different direction. So it shouldn't be called "Back Engraving Reference", when it's functionally so different from the back-oriented "Engraving Reference". I think it's extremely likely for people who read the DCS, without reading the related discussions, could be confused.

Share this post


Link to post
Share on other sites

Hi Yaron,

referring to your second message, and:

4 hours ago, Yaron [LaserOp] said:

Which I took to mean that when your engravers or inkers need to mark, on finished lenses (so on a finishing block, so marking done on the front side of the lens...

...

what is so far the expectation from the labs we have front-side marking on finished lenses for (usually for logos, safety marks, and such), which would be to engrave this 17mm nasally from FB and 1mm above FB.

I have to say we never engrave or ink lenses on the finishing (=edging) block block.

Share this post


Link to post
Share on other sites
7 minutes ago, christian.laurent said:

I have to say we never engrave or ink lenses on the finishing (=edging) block block.

To be clear, you're still talking about marking on finished lenses, on the front side, from data provided by ENGMARK?

If it's marking on the front side, doesn't matter for the sake of this discussion how you physically hold the lenses (finishing block or something else). Same job data records.

If it's marking on the back side, then I'd think the base/center position should be the same ER regardless of whether the lens is finished or not. The relation between OC and ER haven't changed, so the same logic should apply. No?

The question here is "what should be the base position when marking on the front side, from ENGMARK record "ENGMARK=?;?;?;?;?;F;   ?"   .  If marking on the back side I think it's always ER, but I don't see a clear definition on front. From the quote from you email above, I still understand for you it's always so far OC, and for us so far it was FB (which I see how may not available/relevant to you if you don't have it when you do this). And there should be something agreed upon by everyone, so different labs would work regardless of what devices they have (the purpose of the DCS)

Share this post


Link to post
Share on other sites
On 10/24/2019 at 9:27 PM, Yaron [LaserOp] said:

2. The new BE Reference Point, name

The new BE point ("Back Engraving Reference") is intended to be found from inspecting marks already engraved on the back side, and for PRP / OC to be derived from it.

So I think the name and description is currently incorrect and very confusing. "Engraving Reference" very much signals, on clean reading, it's going to be the reference point for engraving, not that it's a different reference point to be gleamed from engraving.

3. The new BE Reference Point, not commutative with other Reference Points, so should it be one or a different record?

...

Hi Yaron,

Someone might discussed about the seIected name, but I had the feeling that the définitions and descriptions from the proposed draft were quite clear regarding the use cases (without ambiguity):

Table 2 BE:  Back Engraving Reference Point (“BERP”); midpoint between semi-visible alignment marks on the back surface of backside engraved lenses; origin of the back surface reference coordinate system.

Table 3 BEOCA, BEOCIN, BEOCUP: Back Engraving Reference Point on the back surface to Prism Reference Point on the front surface after engraving cla: “front surface after engraving” can be confusing – > “front surface for backside engraved lenses” or simply remove “after engraving” (the definition BE/BERP is clear from table 2)

and particularly with:

5.2.2.1 ...

Note      Most distances and orientations on a lens are defined according to a reference coordinate system on the front. For backside engraved lenses, the lens reference coordinate system on the front is linked to the reference coordinate system on the back as described in  5.2.4.

As a conclusion:

- from the note in 5.2.2.1 mentioned above and "Most distances and orientations on a lens are defined according to a reference coordinate system on the front. ",  (working in fact in a single plane (OFXFYF)) , one get a commutative behaviour. 

- we introduced 3D aspects here with BE at the origin of a new, different coordinate system named "reference coordinate system on the back", without commutative behaviour between points in different coordinate systems - BE being a reference point anyway. 

I do hope this will help to clarify.

Share this post


Link to post
Share on other sites
14 hours ago, christian.laurent said:

Someone might discussed about the seIected name, but I had the feeling that the définitions and descriptions from the proposed draft were quite clear regarding the use cases (without ambiguity):

Table 2 BE:  Back Engraving Reference Point (“BERP”); midpoint between semi-visible alignment marks on the back surface of backside engraved lenses; origin of the back surface reference coordinate system.

 

Again, I think that (for anyone who doesn't know in advance what it's supposed to mean) this is indeed confusing and potentially ambiguous in context.

From the same Table 2, let's show the two items in sequence, I'll copy the first (BR) from your quote above (different from the 3.13 draft I have, I'll assume you're using a newer draft), and the second (ER) from the draft I have, which haven't changed for quite a few versions anyway:

Quote

BE:  Back Engraving Reference Point (“BERP”); midpoint between semi-visible alignment marks on the back surface of backside engraved lenses; origin of the back surface reference coordinate system.

ER: Engraving Reference Point; midpoint between semi-visible alignment marks

You see the issue? Both are "Engraving Reference Point", both are "midpoint between semi-visible alignment marks". The difference being that BE is explicitly stated to be on the "back", which isn't really a difference since practically always the marks will be in the back for engraving, when using ER, so the definition of ER might as well have "Back" in it.

And the purpose/usage is very different. "ER" is used to determine where to engrave. "BE" is used from observing the engraving, from a different angle, to get OC.

So changing the name of BE, and describing them differently, is important.

Share this post


Link to post
Share on other sites
2 minutes ago, Yaron [LaserOp] said:

So changing the name of BE, and describing them differently, is important.

I don't know that the nomenclature is as important as the concept so if you have alternate terms you think would be accurate and less ambiguous, please suggest them.

Share this post


Link to post
Share on other sites
14 hours ago, christian.laurent said:

Yaron,

are you sure you are marking according to the finishing (=edging) block (-> FB) and not according to surface block (-> SB) ?

 

Both, or either, depending on context.

Most of the marks are done on the back side, semi-visible marks, during surfacing, on lenses attached to surface blocks. That's the main usage of our engravers in labs.

But there are also cases where we mark on the front, on finished and edged lenses, attached to finishing blocks (again, usually for things like adding logos and such, visibly).

The same LMS/VCA-Host should be able to provide instructions (e.g. view ENGMARK labels) for both. Which is fine, ENGMARK supports both engraving on front and back. So ENGMARK labels for back will go to the "regular" system, and these are oriented around ER. ENGMARK labels for front will go through the "logo" system/module, and these are oriented around... what we're trying to decide here.

In practice this is usually oriented to the frame anyway, so it won't matter. But it can potentially not be, and there should a standard interpretation on what the reference is on those cases.

Share this post


Link to post
Share on other sites
8 hours ago, Paul Wade said:

I don't know that the nomenclature is as important as the concept so if you have alternate terms you think would be accurate and less ambiguous, please suggest them.

The concept is always more important in theory, but the nomenclature (name, quick description) is what people process first, and what they process when they just quickly skim through something, or search for something, or try to just refresh their memory for reference. If it's not possible to understand what something is, or what is the difference between two things, without going full into the details, the names/descriptions are bad.

I'm not sure if the final decision was to keep this as a 2-character name (e.g. BE) or a 3-character name (BER), but maybe instead something like "FO" (or "FOB" if 3 letters, "FOBE" if 4), with a description like (trying to keep as close to the existing description as I can while clearly changing the intent) "Find OC from Back Engraving. The observed midpoint between the semi-visible alignment marks seen on an already finished lens, used to find OC on finished lenses. Origin of the back surface reference coordinate system" .

Both the name and description can't be easily confused with any of the other points, and the purpose and usage is clear.

(Note: Not sure if "finished" is a correct word there, the purpose was to clarify it's not used when making the lens, so it will be obvious as not relevant for devices during production in lab, and similarly obvious as relevant for inspections/checks/diagnostics later. I assume there's a term for it, that can't be maybe confused with a lens during finishing/edging, but at the moment can't recall what it would be. People who actually work with lenses/jobs at that stage would anyway have a much better idea than me about the correct terminology, or if this is or isn't confusing between the two states as-is)

Also, I didn't see anyone respond to the topic of whether this point should really be together with the other Reference Points (on Table 2), given that all of the rest share coordinate space and are translatable in the same way (I think?), and this one requires special and unique handling. Maybe it should have its own sub-section?

Share this post


Link to post
Share on other sites

My point was that I didn't think anyone would object to changing the nomenclature if we could come up with something better.  However, no one had proposed any alternatives.  I don't like using "Find" in the abbreviation but it might be a starting point to rethink the descriptors.  Your description seems more clear to me.

Adopting this change to the narrative will also require completely revising the existing documentation in 3.12.  It's a large change and will require rewriting most of that material as well I think.  Someone from the committee will need to volunteer to undertake the primary rewrite.  I suppose this may require another vote.

Share this post


Link to post
Share on other sites

hi Yaron,

I try to understand and to clarify the situation. So, coming back to your 1st post:

On 10/24/2019 at 9:27 PM, Yaron [LaserOp] said:

1. Engraving Reference for front side engraving

All of the above was for back-side engraving/marking. What about front side?

I strongly believe it couldn't be ER (*) as-is, since there should be only one ER per lens in concept, it shouldn't change based on whether it's wanted for front or back (and it's not even possible to always tailor it even if a VCA Host wanted to).

On the other hand, so far in practice from our customers, whenever front-side/finishing engraving isn't done relative to frame (which it usually is, so doesn't matter so much), they expect it relative to FB.(**) But from Christian, they report to use the PRP (Reference Point OC) as center for marking on the front side on a finishing block.  (So difference of FBOC__ )

So there are at least two different practices already in practice, and none of them actually says "Engraving" (***) for when describing their Reference Point. There should be an explicit decision in the DCS. Is there to be a different new Reference Point? Should it be standardized on OC (and so the description of OC should mention it explicitly, or it should be mentioned explicitly in Marking Records)? Something else?

2. The new BE Reference Point, name

The new BE point ("Back Engraving Reference") is intended to be found from inspecting marks already engraved on the back side, and for PRP / OC to be derived from it.

So I think the name and description is currently incorrect and very confusing. "Engraving Reference" very much signals, on clean reading, it's going to be the reference point for engraving, not that it's a different reference point to be gleamed from engraving. (****)

I fully understand your points, viewed from your own specific context of today. Most probably, your assumptions above are based on your own applications you live with every day but they do not match with the general historical intend and use cases of the DCS tags, as I tried to describe below. Below, the stars **** refer to the discrepancy refered with the corresponding stars **** from your text above.

'ER' (= engraving reference point)  that appeared in DCS 3.03 to my knowledge (where no engraver<>(****) was taken into consideration yet) is neither reserved for engraving <>(****), nor for the back <>(*): the tags ERNR and ERDR were and are still providing distances for NV and FV measurements, including for traditional PAL’s already engraved <>(****) on the front.<>(*)

 

To use FB as a reference for ENGMARK (as mentioned above) is again for a very very specific application. Most systems are not using FB as a reference for inking or engraving.<>(**)

So, most often 'engraving point' 'ER' refers to an already existing (not to be engraved (***) (****) ) permanent positioning reference marking used to position the lens or as reference for finding another point.   

Many DCS tags are not taking 3D aspects into consideration for historical reasons, considering often there is no parallax effect: the lens in some way is behaving like a flat thin lens, with no difference between front and back engravings <> (*) for example. 

BE, with the ‘B’ for 'back' provides more clear 3D information: I have the feeling that it can be considered as a reference point (-> DCS table 2) anyway, but the ‘B’ for 'back' differentiates the specific use of this point for a 3D approach.

So, I think you are reconsidering what is done since 20 years.

Anyway, I would like to better understand your concern. Maybe, for our understanding, you could illustrate what are the tags you are using that involve 'ER'. TY in advance.

Again, I do hope this helps.

 

Share this post


Link to post
Share on other sites

Christian,

Main part of your comments, re usage of ER and re BE:

When working with the same axis system, there is no difference between "where X should be place" and "where X was placed", for the same X.

So "this is where the center point of the engraving is", would be identical to "what should the center point for engraving be".

And, given how the Reference Points are all connected, it's very usable that way. Specifically in our use case (and I'd image other engravers), If something has to be engraved, and what the machine physically knows (common use case, engraving on the back side during surfacing) is where the block is located, to find where the center of the engraving should be (which, again, same as it would be after it's done), we generally use SBBC + BCER.

(And, as a side note, notice that while it's true the usage labels include ERNR and ERDR, indicating ER usable as source/origin, there is and was also BCER, indicating ER usable as target to get to from somewhere else)

I also think you're probably wrong when you write that ER is "most often" used for already marked points as reference for something else. It's entirely possible it was like that 20, maybe even 10, years ago. But at this point, and for a very long time now, the overwhelming majority of labs do engrave/mark lenses as a part of the process. And so, again, if that engraving should be centered on ER when it's done, then it should be done around ER.

We're using BCER to position engraving for about since ENGMASK was first introduced (3.06, I think? around early 2007?). And it has been used (i.e. with non 0/? values) by various labs (and LDS vendors), as the main way to indicate decentration for engraving. That's pretty common, established, and industry-wide acceptable, use.

And one which is usually done on the back side of the lens.

For marking on the front side:

I absolutely agree that at this point it's rarely done, which is why FB is rarely needed for engraving. But it is done in some places, and it's being done more and more. So, I think the question of "when being asked to engrave on the front side, where should I engrave, if I'm not explicitly told to engrave relative to the frame?" is a very valid question (together with its counterpart of "When we want an engraver to engrave on the front side, how do we tell it where to engrave, if we don't want it relative to the frame?" ) .

And I think it's better to get a standard acceptable answer early, instead of just letting engraver vendors all do whatever they personally think is best, and try to sort it out later. I don't quite get the attitude of "no need to decide that before people are starting to use it a lot, lets allow wide usage with no rules and no specification in the standard before trying to figure out the best way to proceed".

Share this post


Link to post
Share on other sites

We had a call on this topic yesterday.  We will be adjusting the descriptive text to make the intention of the records more clear.  This won't be ready for several weeks.  3.13 is being delayed until our next meeting.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.