You want a dark field to see things with an expensive microscope, which seems like a paradox. As [IMSAI Guy] explained, a dark field microscope does not darken the subject. It darkens the area around the subject. After selling his expensive microscope, he found that he had missed this ability, so he decided to make one cheaply. You can see how he did it in the video below.
Darkfield microscopes provide better contrast and resolution by discarding light that passes directly through or reflects directly from the sample. The only light you see is scattered light. If you consider an ordinary microscope, you can imagine the cone of light emanating from the top or bottom. The tip of the cone hits the sample and then diffuses back into the other cone. What hits your eyes—well, actually, the eyepiece—is all the light from that cone. In dark field instruments, the illumination cone is hollow-the light is just a ring. This means that any light not scattered by the sample will be blocked by the stopper in the objective lens. When there is no sample, there is no unobstructed light, so you will see a "dark field."
The light refracted through the sample (from below) or reflected from the feature (from the top) will end in the hollow area passing through the objective and you will see the image. You may already have dark field technology on your desk, which may surprise you. An optical computer mouse that can work on a glass surface uses the same technology. If you want to see some examples and diagrams of all working principles, we published an article on a similar low-tech mod. There is also Wikipedia.
The cheap secret to doing this is to get a used darkfield objective lens with a little rust on the barrel, and then modify them with a custom PC board to create an LED ring light. This is different from the usual illuminator, which emits light through a patch stopper to block internal light. In this case, through the arrangement of LEDs, the lamp is made into a ring shape.
For the rest of the microscope, a very cheap toy microscope gave it life and is suitable for fixing modified light-emitting objectives. Some adapter parts complete the inexpensive dark field microscope. There is no eyepiece, but the camera will send the video to your computer.
We are disappointed that there is no microscope video in this video, but if you check the video below, you can see the oscilloscope in action. The video showing the removal of the transistor is interesting in itself. There is also a video of a 40X image taken with a microscope.
We have seen LED microscope illumination before. If you don't want to spend money on the transfer tube, you can make some out of PVC.
very good! I do not have the ability to make printed circuits, but will consider a solution to do this. I want to know what is the difference between a dark field microscope and a metallurgical microscope?
I used a microscope extensively in a previous job. As far as I know, the metallurgical range is only illuminated from the top, and the light is reflected rather than transmitted. Some people can do both. All the binocular or trinocular I have used, but this may not be the deciding factor.
By the way, the best paper I know about darkfield is https://public.wsu.edu/~omoto/papers/darkfield.html-I particularly like Figure 1. Wikipedia is "upside down" to my way of thinking.
Using dark field illumination from above, how is the visual image product different from the classic arrangement of the dark field diaphragm installed on the condenser below the sample? (The latter's optical components are much simpler)
The dark field below requires a transparent subject. Because light must pass through it. Otherwise the light cones are similar, one from the top and one from the bottom
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