light source for optical flat

ballen · Oct 30, 2018

I rescued an optical flat that was being tossed because it was chipped on the edge. I'd like to use it to locate burrs on gage blocks. What do I need as a light source? I have heard that a white ping-pong (table tennis) ball illuminated with a laser pointer might work. Simple, small, inexpensive suggestions welcome!

Gordon B. Clarke · Oct 30, 2018

ballen said:
I rescued an optical flat that was being tossed because it was chipped on the edge. I'd like to use it to locate burrs on gage blocks. What do I need as a light source? I have heard that a white ping-pong (table tennis) ball illuminated with a laser pointer might work. Simple, small, inexpensive suggestions welcome!

Burrs on gauge blocks? How often does that occur and why and how? It's the "gauge blocks" plural that has me curious.

lou · Oct 30, 2018

This Youtube is using a laser and ping pong ball as a defuser. Looks to me that it works.
Very cheap unique wavelength light for using with Optical Flats... Using a 532nm. 5mw LED laser - YouTube

I'm going to try to set up using low wattage strip green LED lights

adama · Oct 30, 2018

Pretty much any single colour LED will work well, hell the multi colour ones running just one of there pure native colors should also work, thing that i find matters most is the angles - direction need to be right to get the brightest image.

adama · Oct 30, 2018

Green might well be a good choice as the human eye is pretty sensitive to that colour, so should show up better.

Mark Rand · Oct 30, 2018

I use a low pressure (SOX) sodium vapour lamp, with a ballast and igniter. quite cheap off ebay for a more permanent/larger setup.

jhruska · Oct 30, 2018

Monochromatic light source.
Use:
Measures flatness using wave length of light.
Gage blocks, rotary seals, and other surfaces requiring measurement of flatness.
Typical use:
Inspection for wear, warp, distortion, or improper finishing.
Accuracy:
Optical flats are produced for different grades of accuracy.
Measurement can be to millionths of an inch.
John

thermite · Oct 30, 2018

Mark Rand said:
I use a low pressure (SOX) sodium vapour lamp, with a ballast and igniter. quite cheap off ebay for a more permanent/larger setup.

THIS. Or perhaps a neon.

The glass was probably optimized for that wavelength or a neon orange because those were what we had commonly available at the time in monochromatic sources that also hit one of the human-eye's more sensitive zones, green but one of those.

A similar LOOKING output LED is harder to vote for.

Those required a blend of more than one emitter doping, last time I looked, so are neither true point-source nor truly "monochromatic". Mark One human eyeball and the neural-net pre-processors back of it are often tuning in on a heterodyne.

Optical flat has no such technology aiding it.

2CW

CalG · Oct 30, 2018

Diode lasers are "dirty" in that they are not monochromatic. Low contrast is the result. 670 nm red solid state lasers are so red from the customary Hg line at 546 as to be confusing when it comes to correlation with linear measurement.

"When is a band a band?"

An early 633 He-Ne laser is easy enough to come by. A ground glass diffuser employed.
Argon at 514 is "close enough".

All light sources can benefit from clean up filters. Commercial Hg light boxes use "green glass " Schott VG series.

greif1 · Mar 16, 2022

A cheap green filter and most any light source will let you see bands. More monochromatic lights will enhance the contrast. If you are actually measuring, you need to account for the actual wavelength (color).

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