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Natural Science Forum / Physics / Optics / December 2004Calibration
Is it possible to buy a scale to put on the slide in order to measure the image? My eyepieces don't look as if they will support a reticle. I suppose the problem with putting a scale on the slide might be that at high magnification the scale and the object won't be in focus at the same time. Can any of you offer any advice on this matter? I'm wanting to identify mosses and it appears that I need to be able to measure the cells. Peter > Is it possible to buy a scale to put on the slide in order to measure the > image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 5 lines] > > Peter Peter, Actually you can put reticule into any eyepiece I've ever seen. While your idea is good, using a ruling on the slide, you would have problems with expense and dept of field. The reticle can go on the inside of the eypiece or be held in place by a very cheap jump ring. Let us know what kind of eyepiece you have and I can let you know what to do. Oh, here's Klarmann Rulings, they make just about all of the reticles (www.reticles.com) Kevin Cunningham SMS >> Is it possible to buy a scale to put on the slide in order to measure the >> image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 16 lines] > Kevin Cunningham > SMS Another way, if you are willing to use photography, is to use certain diatoms as scales. I have a slide with about six or seven species with well known grating pitch. I just do not know how readily available they are. Bill >>> Is it possible to buy a scale to put on the slide in order to measure >>> the [quoted text clipped - 27 lines] > > Bill No, I can't use photography yet, thanks anyway. Peter >> Is it possible to buy a scale to put on the slide in order to measure the >> image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 3 lines] >> identify mosses and it appears that I need to be able to measure the >> cells. >> Peter > Peter, Actually you can put reticule into any eyepiece I've ever seen. [quoted text clipped - 8 lines] > Kevin Cunningham > SMS Kevin, I bought my microscope from ebay a few weeks ago. I've never owned one or hardly ever used one before. I'm very pleased with it; it is ideal for botany, with magnification ranging from x24 to x400. It is a Prior with 3 object lenses and 2 eyepiece lenses. At the very bottom of each eyepiece is what looks like a lens with a ring holding it in place. The ring has two grooves diametrically opposite. That ring is virtually at the bottom of the eyepiece. The eyepieces are about 2cms in diameter. Help would be very much appreciated, let me know what additional information you require. Regards, Peter >>> Is it possible to buy a scale to put on the slide in order to measure >>> the image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 28 lines] > > Regards, Peter Peter, First contact Prior as Andy suggested. I'll bet that if you take the eyepiece in both hands, one hand on the top plastic part and your other hand on the metal part and gently twist (gently mean gentle twisting) it will come apart safely. There will be a place to insert a reticle either on the eyepiece diaphragm or above it. There maybe a screw off ring to hold it in place. Please ask Prior what size the reticle should be before you order. Be carefull but have fun! Kevin Cunningham SMS >>>> Is it possible to buy a scale to put on the slide in order to measure >>>> the image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 41 lines] > Kevin Cunningham > SMS Kevin, Yes you are right, the eyepiece does come apart. There is plenty of room inside although no obvious fastenings. I will email Prior, although I did that once before and never got a reply. I suspect that they are more interested in selling their new electronic gear than helping me with my old manual instrument. It doesn't appear to have a model number so I'm going to have to describe it. I've no idea how old it is, but it's in good condition. Thanks a lot, Peter >Is it possible to buy a scale to put on the slide in order to measure the >image? My eyepieces don't look as if they will support a reticle. I suppose [quoted text clipped - 4 lines] > >Peter Peter, It's not clear from your post if you need to have a reticle/graticule in the eyepiece, or some way of having length information on a camera image. For the reticle, you could probably figure out a way of putting one either in the eyepiece, or down the cylinder into where the eyepiece slides- in that case, you need a known object to calibrate the reticle to give length information. Edmund scientific carries a bunch and they are cheap. The easiest thing is to call Prior and ask them what size reticle is required and where it needs to go. If, on the other hand, you are acquiring images and need to convert pixels into microns (or some such thing), you need an image of a calibrated ruling. Rulings can be cheap or expensive, depending on the exactitude you need. Again, Edmund carries cheap ones.  SignatureAndrew Resnick, Ph.D. Department of Physiology and Biophysics CWRU School of Medicine tanspose 'op' for mail > If, on the other hand, you are acquiring images and need to convert > pixels into microns (or some such thing), you need an image of a > calibrated ruling. Rulings can be cheap or expensive, depending on the > exactitude you need. Again, Edmund carries cheap ones. Out of curiosity, if you happen to know of these systems. When you have a PC+camera+microscope, and calibrate the measurement (for example, distance from point A to point B in image of camera at PC software) with a calibrated ruling. When "nothing" changes (same microscope, objectives etc.), how often do you re-calibrate - or is the calibration ok for 10+ years? Any explanation for the period or lack of need of recalibration? For most electrical measurement devices, you recalibrate every year or whatever, and the accuracy is stated as "A% for 24hours, B% for 1month, C% for 1 year from calibration date". It seems there is no similar statement of accurace of measurements for microscopes.. Best regards, Kristian Ukkonen. >> If, on the other hand, you are acquiring images and need to convert >> pixels into microns (or some such thing), you need an image of a [quoted text clipped - 18 lines] > > Kristian Ukkonen. Kristian, In my experience once in the microscopes life time is adequate. Glass doesn't change enough to affect a reticle. Microscope reticles will be inaccurate by a few percent, far more than than changes in the glass. Of all of the methods of measurement reticles are the worst. However they are more than enough for biological measurements since biological stuff will just vary. If you need more accurate measurement there are all sorts of electronic things that work well. Kevin Cunningham > "Kristian Ukkonen" <kristian.ukkonen@iki.fi> wrote in message >>When you have a PC+camera+microscope, and calibrate the measurement [quoted text clipped - 16 lines] > just vary. If you need more accurate measurement there are all sorts of > electronic things that work well. I was not referring to reticles, but a PC software that shows the image from camera, and calculates distance based on calibration (based on image of calibrated ruler). This was indeed a question regarding "electrical things". :) Is it usual in these kinds of systems that calibration is done only once, like in reticle-based systems you mention above in your reply? Kristian Ukkonen. >> If, on the other hand, you are acquiring images and need to convert >> pixels into microns (or some such thing), you need an image of a [quoted text clipped - 14 lines] > B% for 1month, C% for 1 year from calibration date". It seems there > is no similar statement of accurace of measurements for microscopes.. Interesting question. Let's also assume the camera and PC are constants. I think that the main source of error in this case is the user. Since the image will have some blur, which pixel the user decides is the edge of the micrometer bar is the source of some variation. Also, there will be some variation due to non-perfect alignment of the micrometer to the pixel array in the camera. After that, I would think there are small errors introduced due to temperature fluctuations (thermal expansion of the micrometer, slight changes in the optical path due to thermal expansion of the lenses in the objectives, etc. Aside from things like bulb output, camera electronics and motorized stage wear and tear, there probably are sources of long-term drift in a microscope, but I don't know what they are. Personally, I rarely re-calibrate. Mostly, it's because our work doesn't require extremely high levels of precision. If a particular experiment calls for high precision, I'll take a few "calibration" images just prior to and just after the experiment as a 'best practice'. Are you asking for a reason, or idle curiosity? SignatureAndrew Resnick, Ph.D. Department of Physiology and Biophysics CWRU School of Medicine tanspose 'op' for mail >> If, on the other hand, you are acquiring images and need to convert >> pixels into microns (or some such thing), you need an image of a [quoted text clipped - 18 lines] > > Kristian Ukkonen. Thanks Kristian, but that is all rather out of my league. I'm just an amateur botanist wanting to measure, with a manual microscope, approximate cell sizes in mucrons. Thanks anyway, Peter >>> If, on the other hand, you are acquiring images and need to convert >>> pixels into microns (or some such thing), you need an image of a [quoted text clipped - 24 lines] > Thanks anyway, > Peter Sorry, meant 'microns' :-) >>Is it possible to buy a scale to put on the slide in order to measure the >>image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 20 lines] > ruling. Rulings can be cheap or expensive, depending on the exactitude > you need. Again, Edmund carries cheap ones. Andy, Good post just a quick point. The reticle goes in the eyepiece, if you put it down the below the eyepiece you won't see it but it won't bother you. Depends on what you need. Thanks, Kevin Cunningham SMS >>Is it possible to buy a scale to put on the slide in order to measure the >>image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 20 lines] > ruling. Rulings can be cheap or expensive, depending on the exactitude > you need. Again, Edmund carries cheap ones. Andrew, Good post, just a small point. The reticle goes in the eyepiece not the eyepiece tube. Put it in the tube and you'll never see it but this does keep the reticle from bothering you. Thanks, Kevin Cunningham SMS >>Is it possible to buy a scale to put on the slide in order to measure the >>image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 20 lines] > ruling. Rulings can be cheap or expensive, depending on the exactitude > you need. Again, Edmund carries cheap ones. Thanks Andy. I'm not interested in aquiring images at the moment. I'm going to contact Prior and take it from there. Peter Hi Peter, There is a scale called a stage micrometer which can be used to calibrate an eyepiece reticle or there are special eyepieces called filar eyepieces that have a reticle plus a micrometer driven reference line. Both these items come up for sale from time to time in eBay. Both items are listed now.. The stage micrometer is used to calibrate an eyepiece objective combination. Please contact me off line at nghy_1@REMOVEyahoo.com for additional information. Aaron See http://www.microscopyu.com/articles/formulas/measurements.html >Is it possible to buy a scale to put on the slide in order to measure the >image? My eyepieces don't look as if they will support a reticle. I suppose [quoted text clipped - 4 lines] > >Peter Depending on your scope, you might just buy an ocular with the appropriate eyepiece from Edmund Optics [1]. If your scope uses DIN and you are using Achromats, a decent third-party ocular with a reticle should suffice. A scale in the object plane is not recommended for this application. Gregor [1] http://www.edmundoptics.com/onlinecatalog/browse.cfm?categoryid=206&level=2 > Is it possible to buy a scale to put on the slide in order to measure the > image? My eyepieces don't look as if they will support a reticle. I [quoted text clipped - 5 lines] > > Peter |
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