jevidon Posted January 27, 2015 Author Share #81 Posted January 27, 2015 Advertisement (gone after registration) Can someone here tell a layman (me) why a glass is "corroding"? Other than from a few fluorine compounds I was always under the impression that glass didn't do much of anything. Thanks, s-a Here are some links, some pretty technical, that explain the corrosion mechanism of glass. One of the links discusses glass corrosion tests using sulfuric acid commenting that sulfuric acid mimics pretty well the corrosion that glass undergoes when exposed to atmosphere ("...the treatment with sulphuric acid mimics well the atmospheric weathering..." ) For those that remain confused by the technical explanations, just accept that there are scholarly studies that investigate corrosion of glass due to atmospheric exposure as well as exposure to certain chemicals. The PPG article (highlighted in red) is perhaps the most comprehensible to those of us that lack the technical expertise. Glass corrosion? Believe it. Corrosion - Wikipedia, the free encyclopedia (scroll down to 10.2 Corrosion of Glass) http://www.sciencedirect.com/science/article/pii/S0167273808005365] http://buyat.ppg.com/glasstechlib/19_TD105F.pdf Link to post Share on other sites More sharing options...
Advertisement Posted January 27, 2015 Posted January 27, 2015 Hi jevidon, Take a look here Reid Review on M9 sensors. I'm sure you'll find what you were looking for!
semi-ambivalent Posted January 27, 2015 Share #82 Posted January 27, 2015 just accept I hate doing that. But I do, and often. Thanks! s-a Link to post Share on other sites More sharing options...
williamgm Posted January 27, 2015 Share #83 Posted January 27, 2015 This thread is getting very technical, I think I'm just going to go out and take some photographs….. Link to post Share on other sites More sharing options...
Lenshacker Posted January 27, 2015 Share #84 Posted January 27, 2015 It is very relaxing to just grab a camera and take it out to shoot some photographs. Knowing what went into making that camera- makes me appreciate it even more. Link to post Share on other sites More sharing options...
pibitller Posted January 27, 2015 Share #85 Posted January 27, 2015 I have a question: it is an IR filter glass or film? If it's a film, the solution would be to put it in the CCD, instead outdoors. A glass can be cleaned easily. Xavier Link to post Share on other sites More sharing options...
Lenshacker Posted January 27, 2015 Share #86 Posted January 27, 2015 The glass is question is a "IR Absorbing Cover Glass" that is cemented over the CCD. The cover glass itself has a protective coating on it, to block humidity. The problem seems to be the integrity of that coating. The glass "corrodes" and cannot be cleaned. Think of it as trying to clean a lens that has an etched surface. The cover glass is cemented to the CCD, making it so the entire CCD must be replaced. A longterm solution would be to use a different glass, or to make it easier to replace just the glass cover. Other CCD's in the lineup have "taped cover glass", easy to replace. Link to post Share on other sites More sharing options...
jevidon Posted January 28, 2015 Author Share #87 Posted January 28, 2015 Advertisement (gone after registration) The glass is question is a "IR Absorbing Cover Glass" that is cemented over the CCD. The cover glass itself has a protective coating on it, to block humidity. The problem seems to be the integrity of that coating. The glass "corrodes" and cannot be cleaned. Think of it as trying to clean a lens that has an etched surface. The cover glass is cemented to the CCD, making it so the entire CCD must be replaced. A longterm solution would be to use a different glass, or to make it easier to replace just the glass cover. Other CCD's in the lineup have "taped cover glass", easy to replace. I hadn't heard of that. Could you expand on taped cover glass and what cameras use them? Link to post Share on other sites More sharing options...
Lenshacker Posted January 28, 2015 Share #88 Posted January 28, 2015 "Taped Cover Glass" has been offered by Kodak's sensor Division, now "On Technology" from the early 1990s as an option on many of their detectors. It's easier to remove than the cemented cover glass. I'm not sure which cameras make use of them, most camera manufacturers do not publish the details. Kodak CCD's were bought and used by the scientific market, and easily replacing the cover glass was important. Most camera manufacturers use clear cover glass over the detectors, and use IR absorbing glass that is separate from the sensor. Currently, the KAF-18500 is the only detector in the On Technology line-up that uses IR absorbing glass for the cover. The design of wide-angle lenses used with the Leica M-Mount forces the use of a thin sensor stack, meaning the use of a clear cover glass over the CCD and a separate IR absorbing glass could not be used. I'm just stating that use of taped cover glass is one possible solution for making it less expensive for Leica, would mean the CCD would stay in place and only the defective cover glass need be replaced. Using a cover glass that does not corrode, ie will not need to be replaced, is of course a better solution. The optical properties of the S8612 cover glass are "the best available" for the role of filtering out IR and passing visible. Link to post Share on other sites More sharing options...
jevidon Posted January 28, 2015 Author Share #89 Posted January 28, 2015 Thanks for the explanation. i had assumed that cover glasses, whether IR or not were all bonded. Link to post Share on other sites More sharing options...
Lenshacker Posted January 28, 2015 Share #90 Posted January 28, 2015 KAF-8300: Full Frame CCD, Image Sensor, 8.3 MP just an example in the current ON Technology line-up, the KAF-8300 is offered with options for taped cover glass, also available in color and monochrome. Link to post Share on other sites More sharing options...
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