Doug Kerr
Well-known member
After photographic lenses, the lenses with which most of us here are most likely to be interested are vision correction (eyeglass) lenses. It is a fascinating field, with its own language and tools.
I will shortly publish on my technical information site, The Pumpkin, a trio of technical articles relating to this field. They are now available directly, via the links below (they will be indexed on The Pumpkin presently).
The first in the series, "Principles of Eyeglass Prescriptions", is available here:
http://dougkerr.net/Pumpkin/articles/Eyeglass_Prescriptions.pdf
It describes the way in which the optical parameters of an eyeglass lens are specified in a "prescription". Included is a discussion of the fact that two different classes of prescribing daycare professionals, ophthalmologists and optometrists, use different conventions for this.
The article begins with background on such related issues as lens focal length and power, the focusing of the human eye, and deficiencies in that, and how those deficiencies are mitigated by corrective lenses.
The next article, "The Refractor/Phoropter—An Important Tool in Vision Correction", is available here:
http://dougkerr.net/Pumpkin/articles/Refractor.pdf
It discusses the refractor (often called phoropter, although Phoropter is actually a tradename of one manufacturer), the mask-like instrument with many dials used to determine the optimum prescription for corrective lenses for an individual.
As with the first article, we being with a review of important background principles (I wanted each article to stand on its own). Then the principle, and mode of operation, of the refractor are described.
The third article, "The Focimeter—Measuring Eyeglass Lenses", is available here:
http://dougkerr.net/Pumpkin/articles/Focimeter.pdf
The focimeter (often called a lensometer or vertometer, although Lensometer and Vertometer are tradenames of two manufacturers) is the microscope-looking instrument used to ascertain the optical parameters ("prescription") of eyeglass lenses or (as required in the making of eyeglasses) of partially-completed lenses. One interesting recent casus belli is described in the footnote on page 1 of the article.
Again, this article begins with essentially the same background material mentioned above.
Then, the basic nature of the instrument is described, following by an discussion of its operation and use. Its optical innards, and some basic theory of their functioning, are explained in an appendix.
All three articles are laced with historical and societal curiosities. A great deal of both technical and historical research (both some months ago and over the last two weeks) went into the project, and I'm pooped.
But the bravest service was by Carla, my ace copyeditor, who had to find all the lost prepositions, disagreements in number, and mismatched parentheses that peppered this magnum opus in manuscript. But she said there was a lovely poetry in some of the technical terms and phrases.
Best regards,
Doug
I will shortly publish on my technical information site, The Pumpkin, a trio of technical articles relating to this field. They are now available directly, via the links below (they will be indexed on The Pumpkin presently).
The first in the series, "Principles of Eyeglass Prescriptions", is available here:
http://dougkerr.net/Pumpkin/articles/Eyeglass_Prescriptions.pdf
It describes the way in which the optical parameters of an eyeglass lens are specified in a "prescription". Included is a discussion of the fact that two different classes of prescribing daycare professionals, ophthalmologists and optometrists, use different conventions for this.
The article begins with background on such related issues as lens focal length and power, the focusing of the human eye, and deficiencies in that, and how those deficiencies are mitigated by corrective lenses.
The next article, "The Refractor/Phoropter—An Important Tool in Vision Correction", is available here:
http://dougkerr.net/Pumpkin/articles/Refractor.pdf
It discusses the refractor (often called phoropter, although Phoropter is actually a tradename of one manufacturer), the mask-like instrument with many dials used to determine the optimum prescription for corrective lenses for an individual.
As with the first article, we being with a review of important background principles (I wanted each article to stand on its own). Then the principle, and mode of operation, of the refractor are described.
The third article, "The Focimeter—Measuring Eyeglass Lenses", is available here:
http://dougkerr.net/Pumpkin/articles/Focimeter.pdf
The focimeter (often called a lensometer or vertometer, although Lensometer and Vertometer are tradenames of two manufacturers) is the microscope-looking instrument used to ascertain the optical parameters ("prescription") of eyeglass lenses or (as required in the making of eyeglasses) of partially-completed lenses. One interesting recent casus belli is described in the footnote on page 1 of the article.
Again, this article begins with essentially the same background material mentioned above.
Then, the basic nature of the instrument is described, following by an discussion of its operation and use. Its optical innards, and some basic theory of their functioning, are explained in an appendix.
All three articles are laced with historical and societal curiosities. A great deal of both technical and historical research (both some months ago and over the last two weeks) went into the project, and I'm pooped.
But the bravest service was by Carla, my ace copyeditor, who had to find all the lost prepositions, disagreements in number, and mismatched parentheses that peppered this magnum opus in manuscript. But she said there was a lovely poetry in some of the technical terms and phrases.
Best regards,
Doug