In 2001, the Edmund Scientific brand was sold to a school science supply company, and is now unrelated to the surviving original company, Edmund Optics. Edmund Optics has continued as a high-end optics manufacturer. Through their Anchor Optics commercial/experimental optics brand, they still have in (electronic) print many of the now classic Edmund Scientific optics publications, and have made these available for free download. See: http://www.anchoroptics.com/documents/ This is a tremendous service to the home shop machinist, amateur scientist, and maker.
The primary item of interest with regard to shop-built optical comparators is No. 9314 of Edmund's "Popular Optics Library," How to Build Optical Projectors. (Get it from the Anchor Optics downloads page) As described, these aren't calibrated as optical comparators, but (as is always the case with Sam Brown's writing, and this is either by him or up to his standards) there is enough information here to make one which is.
There are a number of interesting articles in No. 9059 of the "Popular Optics Library," How to Build [Optical] Drawing Devices. (Again, download it from the Anchor Optics downloads page.) This booklet was incorporated as Chapter 6 of No. 9445 of the "Popular Optics Library," Popular Optics (Barrington, NJ: Edmund Scientific Co., 1974.) (Not reprinted as such on the Anchor Optics site; you'll have to find a secondhand print copy.)
No. 9044 in the "Popular Optics Library," How to Condense and Project Light, is also quite useful. Again, Anchor Optics downloads page.
In Make magazine, Issue No. 14, there is an article by Steve Lodefink entitled "Wall Eye: Build Your Own Opaque Projector." (pp. 74-77). It's a good article, but rather high-level. It refers to the Edmund "How to Build Opaque Projectors" as a technical source, and you'll need it. As noted, the PDF of the Edmund item hosted by Make in conjunction with this article is/was the same as that on the Anchor Optics site.
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