No, I’m thinking of ASML’s through the lens (TTL) alignment system. A set of gratings are passed under the lens. Laser light is scattered off of the marks, and the first order light is passed through a similar set of marks on the reticle. What passes through is sampled and the point where the 8um and 8.8um gratings transition at the same place is considered the alignment point.
That’s the simple description. The concept is still more or less used in their latest alignment systems, but I’m not sure of the details.
Wafer stages have used interferometry since the '70s, scanner stages since the early '70s. Interferometry is more accruate for measuring relative movement, but it doesn’t provide an absolute reference point.
In case anybody doesn’t know about mechanical scanning television, yes, there once was such an animal. A few nuts in Britain, and one in the USA, experiment with it even to this day.
One of my prized possessions is a near mint condition Curta II that I bought on Ebay a couple years ago. It’s an amazing machine. The life story of Carl Herzstark who invented the Curta is amazing as well.
Slide Rules
Nomographs
Pocket adding Machines (the ones with moving slides, not the push0button kind)
Manually extracting Square roots (and higher)
Tables of Logarithms
Buffon’s Needle and similar calculation-by-experiment methods
Thus, the log10 of 700 must be about 2.85. When I check that with an electronic calculator, I get 2.8451. Not bad, eh?
About 10 years ago I designed a slide rule to manage several slightly complicated calculations in the industry I was working in at the time. I found a company that still makes them, and had 3000 of them made. There were 4 simple multiplication scales, 5 unit conversion marks, and one special scale that essentially reported purity in terms like 99.5% or 5N7 (99.9997%). We passed hundreds out to possible customers so that they could compare our products with competing ones in a way that used a real and insightful figure of merit.
I guess you can tell that John Napier was kind of a hero of mine. But my favorite thing that he did was publishing pamphlets arguing his view that the Pope was the Antichrist.
Funny thing is: I’m glad you brought this up. My primary hobby these days is making shavings out of billet on a mill and lathe. My current project is a rotary mill (it spins the part to be worked on around an axis…it required making a worm gear and screw), one of the ways of recording angles precisely is with a vernier…but if you’re making it yourself, you also need to make the markings, and a vernier is part of the design.
S’funny how much knowledge we no longer know. (My handbook, how to run a lathe, is the 1942 printing. The FIRST printing was in 1914. Most of the concepts were well known THEN. NOW, it’s all CNC. Not a bad thing, but a lot of the art’s been lost.)
Ok, I’m gonna’ need some help here. I’ve got most of how it works but not all. The buttons on the side input the working value, the top crank performs one operation per spin, and rotating the whole top multiplies the decimal place of the operation X10 per notch. The ringed lever resets the number of operations count and the result count to zero. That leaves pulling out the top crank, and the extra toggle switch. I gather that these somehow invert the operations you’re performing so you can do subtraction and division; but I haven’t worked out how. Anyone?
Not really, you can find much of it on Google! Also, if you haven’t mosied over to Homeshop Machinist’s boards, you outta. There’s more than a few of the old timers there who bitch about how stupid the new fangled dial calipers are making the kids these days.
Haven’t spent much time on HSM, I spend more of it on Popular Machinist…and actually, since I got the South Bend restored, don’t spend a lot of time on the forums.
I need to get back out to the garage, but it’s pretty cold out there.
I’m surprised it took so long for slide rules to get mentioned.
You might also consider the old surveying equipment that was used prior to electronic distance measurement and global positioning systems. Examples would be transits and steel tapes. With the old steel tapes, surveys would have to correct distances measured for air temperature, tension and sag in the tape, and other factors (been a while since I took my old survey class, but seems like there were 7 factors including human error).
Probably very few fields have been so completely revolutionized in the past 20 years as land surveying, due to the advent of inexpensive lasers, satellites, and computers.
Duh, never mind. Finally got it*. Pulling out top crank switches value added to negative; toggle switch changes whether revolution counter increments or de-increments.
*Don’t you wish if you were going to understand something, it would come to you immediately, not hours later?
