原帖由： yvan ,
I think I can partially answer the question by giving some considerations to think about. I use these on a regular basis, being it in the field of life sciences. Judging from your post, you're an electronics repair man. From personal experience: when you have to use a stereo microscope for hours in a row, you definitly want a binocular with eyepiece tubes placed at 45°. They're more expensive, but really worth it, unless you don't mind your neck and/or your back feeling like shredded each evening... Depending on brand and model, those instruments can magnify anything between 5 x and some 150 x. In biology, and I suppose that goes for your line of work as well, magnifications above say 40 x are only rarely used. And even in an excellent instruments, the image quality deteriorates quickly above that magnification. Unless you want to pay $ 10,000 or even more. There are two types of stereo microscopes: the Greenough (GR) type and the CMO ("Common Main Objective"). Both have their (dis)advantages. The CMO has greater light gathering power (more light in the image) but the GR can easily compensate that by the use of a stronger light source. The CMO is in the literature explicitly advised as "the workhorse" for "electronics repair" and such, but it is 2 - 3 x more expensive than an equivalent GR. A lot of CMO's are equipped with a zoom function. It can come handy, I suppose. If you have every once in a while some other, larger repair work, such as computer mother boards and such, you might want to consider a stereo microscope mounted on a boom stand, giving you more work space. Field of view might be a consideration: a larger FOV is always handy. As a general rule, CMO's have larger FOV's compared to GR's. But there are exceptions. Working distance might be a consideration. Some have far greater working distance than others. Illumination might be a consideration. In their basic version binocular microscopes are usually equipped with a single low voltage illuminator, which often leaves much to desire. Better illumination such as an adaptable ring illuminator or (luxury!) a fiber optic illuminator are expensive options. Regarding brands and models, I can't really give much of an advice, not being an expert on stereo microscopes. I used only two of those: a CMO, the Russian LOMO MBS-10 which I considered usable but nothing more than that and a GR, a 1970's - 1980's Zeiss STEMI DR, which is better than the LOMO, but not as good as the brand suggests.