My hobby desk is limited in space nevertheless I added a SMD viewer with a relatively long working distance.

Here the result. In the screen you can see some 0603 components.

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I started reading this very nice post http://operationalsmoke.blogspot.it/2014/05/diy-usb-soldering-microscope.html

I found in my cellar an old camera made in URSS (1965?). I made some test of the focusing distance of the lens. I used an empty can of tuna in oil as spacer ( use protective gloves when cutting the tin). I took the lens threaded mounting ring from the old camera and fixed it to a hole in the can.  The can is painted mat black to avoid light reflections.

A black plastic box houses the webcam.

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I bought a cheap HD (720p) webcam with manual focus (www.banggood.com).

To modify the webcam remove the webcam board from its housing. Unscrew the lens mounting and cut the black plasic ring. DO NOT TOUCH the red infrared IR filter placed at bottom near the camera sensor. All optics exited the front after cutting the upper black ring. Do not touch the filter glass.  Protect the sensor with paper tape when attaching the camera to the new box. Fix the camera pcb using nylon spacers and screws.

 

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Before attaching the camera card, experiment a little bit with the distance of the lens as the magnification depends on the lens type and the layout of the camera.

I use the camera with a Windows PC 10. The applications I prefer are VirtualDub and Windows native Camera. VirtualDub seems a bit faster.

The positioning of the camera must be very solid to ensure stable images. In my setup I placed 9 neodymium magnets on the back of the plastic box and an iron plate (from an old CD drive cover) is screwed onto the top of my holder. The magnets allow to  move and unplug the camera easily.

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To obtain a wide depth of field a low aperture and a strong lighting must be used.

I made a try of a home made lamp with a 10 watt led and a focusing lens taken from an old video camera. A fan cools the led aluminum radiator. Some magnets are used to suspend the lamp. 

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Costs  
Lens (taken from old photocamera) --
webcam 13 €
plastic box 3 €
neodymium magnets 2 €
spacers, screws, paint etc 5 €
Led 10Watt + power supply + fan 7 €
Lens for led (taken from an old videocamera)  --
Total 30 €