Announcement

Collapse
No announcement yet.

new version of Caliper Accuracy article available

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Evan
    replied
    I wonder tho how you deal with stray light with the open construction.
    It's dark at night here. Well, except for now when it doesn't get completely dark at all. Not a productive time for astronomy. At most times of year it's dark at night. No streetlights and I live on a dead end road at the dead end. No headlights and the back field is well removed from the sight of anything but sky. If circumstances required it the scope could be either draped or a sock put on.

    The design of an instrument to be unaffected by temperature is called passive athermalization.
    Interesting. However, from what I can find it isn't a general term. It seems only to apply to optical systems and in particular telescopes.

    It also seems that the term is synonymous with passive temperature compensation, which is how I described it.

    This patent application is related to copending, commonly-assigned U.S. patent application Ser. No. 860,936, filed in the names of O'Brien et al on Mar. 31, 1992, and entitled "COMPACT, PASSIVELY ATHERMALIZED OPTICAL ASSEMBLY", now U.S. Pat. No. 5,120,650 the disclosure of which is included herein by reference.

    BACKGROUND OF THE INVENTION

    The present invention relates to means for effecting temperature-compensation of focal length in an optical assembly.

    Certain optical assemblies such as those found in laser output scanners require a stable monochromatic collimated light beam provided by a laser diode and a collimating lens. For adequate optical performance, the beam source must maintain a predetermined beam quality over a wide ambient temperature range. In conventional apparatus, the beam source and lens are mounted in a mechanical structure that attempts to maintain the beam focal length while the apparatus undergoes temperature-induced structural changes. Hence, the athermalization (i.e., thermal compensation) is effected either passively or actively.

    Passive compensation systems typically rely on the differences in coefficients of thermal expansions of the various elements in the optical system such that there is minimal net focus shift with temperature.

    http://www.patentstorm.us/patents/53...scription.html
    [my emphasis]

    Leave a comment:


  • Optics Curmudgeon
    replied
    Maybe there's more to that than simple incompetence, the old German inch, the "zoll", was 1.037 imperial inches. Works out to 26.3398 mm. Nah, I just think they screwed up.

    Joe

    Leave a comment:


  • John Stevenson
    replied
    Optics,
    Don't believe all you read



    The famous Mars ruler ?

    .

    Leave a comment:


  • Optics Curmudgeon
    replied
    ...In the good old days....

    From the "ankle" of my Chesterman height gage.



    Break out the pencil and paper.

    Joe

    Leave a comment:


  • John Stevenson
    replied
    Incommmmmmmming

    Originally posted by tdmidget
    Evan your telescope appears to be a fine piece of work. I wonder tho how you deal with stray light with the open construction.
    Also it is not thermally compensated. I conferred with a friend who is an engineer at the University of Arizona Optics Labs and designs telescopes for places like Kitt Peak( you may have heard of them). The design of an instrument to be unaffected by temperature is called passive athermalization.
    TDMidget,
    Would you mind awfully providing me with personal details like date of birth, next of kin etc so I can take out a personal insurance policy on you whist you are prodding Evan with a sharp stick.

    I can see a pending claim coming which could net me a few $$$.

    .

    Leave a comment:


  • Swarf&Sparks
    replied
    "passive athermalization"
    Did that work for the HST?

    Leave a comment:


  • tdmidget
    replied
    Evan your telescope appears to be a fine piece of work. I wonder tho how you deal with stray light with the open construction.
    Also it is not thermally compensated. I conferred with a friend who is an engineer at the University of Arizona Optics Labs and designs telescopes for places like Kitt Peak( you may have heard of them). The design of an instrument to be unaffected by temperature is called passive athermalization.

    Leave a comment:


  • IOWOLF
    Guest replied
    "I like the idea of starting a new thread although my motivation is rather selfish. The metrics on my web site show very few people visiting this article and I believe its debut was swept aside by all of the other discussion."


    OMG, now a Metric heat sensitive caliper?

    Oh the humanity, When will it end.

    Leave a comment:


  • Swarf&Sparks
    replied
    Rick, I appreciate the effort.

    Apparently, so do the practical people on this board.
    It is a reminder to those of us who have crossed the analogue/digital boundary.

    Keep up the good work.

    Best regards,
    Lin.
    (edited for spelling)

    Leave a comment:


  • lazlo
    replied
    Originally posted by Evan
    You on the other hand don't seem to have anything better to do. You are, quite simply a troll and just can't stand to see this thread come to a peaceful conclusion.
    Evan,

    I've contributed technical data to every thread that Rick has posted in the last month, including this one. But as soon as it turned into a "yes, there's a temperature compensated caliper" "No, there's not." thread, I tuned out, and a lot of others have as well, as Rick noted.

    OldTiffie is saying the same thing in the post immediately above mine -- is he a Troll too? ...and Sir John is trying politely to either stop the circular argument you're having, or at least redirect it back to Rick's original topic.

    Cheers,

    Robert

    Leave a comment:


  • rgsparber
    replied
    I like the idea of starting a new thread although my motivation is rather selfish. The metrics on my web site show very few people visiting this article and I believe its debut was swept aside by all of the other discussion.

    I did find the discussion about temperature compensation interesting and read all of it. Little of it can be applied to the article because I am convinced the HF caliper has no TC.

    The excellent work, still in progress, by ckelloug (Cameron), will enrich the next version of this article as well as another one on the Shumatech DRO.

    I hope to see you all on the new thread.
    Last edited by rgsparber; 06-10-2007, 10:22 AM.

    Leave a comment:


  • Evan
    replied
    What took you so long Lazlo? Been sleeping?

    Where do you get the idea that any flaming was going on? If I wanted to flame there wouldn't be any doubt as to my intention but that's a waste of time and serves no purpose. You on the other hand don't seem to have anything better to do. You are, quite simply a troll and just can't stand to see this thread come to a peaceful conclusion.
    Last edited by Evan; 06-10-2007, 10:12 AM.

    Leave a comment:


  • lazlo
    replied
    Originally posted by JCHannum
    It is all part of the fun. Through debate and the expression of different opinions and viewpoints, often a new perspective can be obtained.
    From speaking with several of the regulars here offline and in real life, a lot of folks find these monthly Evan-centric flame wars annoying, and they certainly detract from the original poster's intentions, since most people just tune-out of the thread.

    More importantly, just like on the 3-phase power thread, you're not convincing Evan of anything. He believes he saw a temperature compensated Master vernier, and there's nothing you can say that will convince him otherwise.

    Leave a comment:


  • JCHannum
    replied
    It is all part of the fun. Through debate and the expression of different opinions and viewpoints, often a new perspective can be obtained.

    Leave a comment:


  • Evan
    replied
    I think its about time the "point-scoring" stopped and the level of discussion got back to what Rick Barber originally intended.
    Tiffie,

    As you are fairly new to the forum you probably don't realize that Jim and I have a go at it every once in a while. There is no blood involved and you will note that no personal attacks are involved. It's more a hobby. I have a lot of respect for Jim and on the too infrequent occasions when he posts photos of some of his work it is obvious he is an excellent machinist and craftsman. We are both stubborn though.

    Leave a comment:

Working...
X