EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: cattle435 on August 22, 2022, 09:05:41 am
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Greetings. I am very new to electronics. I have good equipment bar a magnification source. Have thought about getting a HDMI output setup or stereo binocular microscope and decided to go for the stereo binocular scope (SWIFT S41-20). Reading into the reviews I've found people saying the FOV is almost unusable with a 1X objective lens and 10X eyepieces. I haven't been able to find a 0.5X objective lens anywhere without it costing about ~£50+ at which point it probably makes sense to get a different model. However I have been able to find 5X eyepieces for relatively cheap. So is there an inherent difference between having 0.5X objective lens + 10X eyepieces and 1X objective lens + 5X eyepieces W.R.T the FOV?
Any other considerations to make when choosing a microscope or maybe other forms of magnification? I was very keen on the idea of buying the parts from AliExpress 1 by 1 and having output to a 1080p display however I found 1) everything would take a million years to arrive here in the UK 2) the setup would take a lot of space on my table 3) from the videos I've watched on youtube everyone has a problem with the "depth perception" (having not used a microscope in over 10 years I can't really tell what this means). So I thought the stereo was the best option for me.
I'm very much learning electronics mostly as a hobby so it isn't something I would use daily.
Cheers
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Edmond has been in the optics business for a long time. This may help you some:
https://www.edmundoptics.com/knowledge-center/application-notes/microscopy/understanding-microscopes-and-objectives (https://www.edmundoptics.com/knowledge-center/application-notes/microscopy/understanding-microscopes-and-objectives)
But they are not a bargain basement type of supplier. And their prices may make you feel that your previous searches found things that are dead cheap.
One suggestion is that if you want a good field of view at just 5X, a good quality magnifying lens may be a better choice. The only advantage of a microscope with a 1X or 0.5X objective lens would be for a greater working distance from the lens to the object being viewed. That may be better if you intend to use the microscope to view things (PCBs?) as you work on them.
Another suggestion would be an LCD microscope. It may not have the resolution of a purely optical one, but I have one and it is good for doing work on modern circuit boards. Don't fall for claims of 1000X. That is pure bunk and it instantly turns me off. All you would see at that point is a magnified blur. But they can be quite good at 2X to 20X or a bit more.
https://www.amazon.com/s?k=LCD+microscope&ref=nb_sb_noss (https://www.amazon.com/s?k=LCD+microscope&ref=nb_sb_noss)
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All the stereo microscopes I have dealt with magnify the specimen image in two steps, first with the objective(s) and zoom/magnification-changer lenses, from the objective(s) to a pair of intermediate images, typically 10mm below the tops of the eyepiece tubes, then with the eyepieces from the intermediate images to your eyes. A typical zoom microscope might magnify from 0.7 to 4.5X from the specimen to the intermediate image, then another 10X from the image to your eyes.
The field of view is generally constrained by the FOV of the eyepieces which in turn is limited by the largest diameter image you can project into an eyepiece tube before it hits the sides. That might be 27~28mm for tubes accepting 30mm eyepieces: you can only make the tubes and eyepieces so thin.
A standard 10X/21mm eyepieces magnifies the inner 21 mm of the intermediate image 10X, giving you 21mm FOV, there. At its lowest zoom level, an 0.7X objective + zoom magnification increases that FOV to 21 / 0.7 = 30mm at the specimen. A 5X eyepiece only has the intermediate image to work with, so in this case it might offer at most 28 / 0.7 = 40 mm FOV at the specimen before the eyepiece starts looking at the walls.
By halving the magnification, an 0.5X auxiliary lens in front of the objective will double the FOV to 21 / 0.35 = 60mm at the specimen – assuming no vignetting along the way, which there should not be for a good design. Along with winning at least 50% more FOV, the 0.5X lens likewise wins more working distance that helps keep tools from whacking the objective(s).
I hope that made sense.