EEVblog 1458 - Microscope Polarising MAGIC!

[EEVblog]

Can't see those pesky laser etched part numbers on chips, Dave demonstrates what's happening with  microscope polarising filter lenses on Twitter that's blowing people's minds. And other tricks of the trade.
Does it actually work?



DIY Light box for PCB photography:
https://twitter.com/azonenberg/status/1494061604161220615
https://twitter.com/ghidraninja/status/1494343655053832203
Aputure Amaran AL-M9 LED light https://amzn.to/3H0O5KW
Leica microscope brochure: https://downloads.leica-microsystems.com/Leica%20LED3000%20RL/Brochures/Leica%20LED3000-5000_Brochure_EN.pdf

[yngndrw]

This is what I made, has a joystick to control the relative brightness for the four LEDs. It means that you can change the effective direction of the light.

Sorry about the poor filming, I have my phone held against an eye piece.

[arekm]

Yeah, seeing part numbers is not really a problem but these annoying reflecting solder joints are! That subject is much more interesting.

[graybeard]

This is a standard technique known as Nomarski microscopy.   It was originally developed to see grain structure in metals.   I have a very nice Olympus Nomarski microscope at work I use to look at integrated circuit structures.   I can use the polarizers to highlight different layers inside the IC looking through the Silicon Nitride or Silicon Dioxide (depending on the technology) to see details of components in the IC.   Optimum performance depends on both the absolute polarization of the illumination and the polarization of the analyzer.

I have thought about adding the capability to my Bausch and Lomb Stero Zoom in my home lab.  After seeing this video I feel motivated to do it.

I already have many polarizers for my cameras.   I just need the appropriate step-up ring to fit one of my polarizers to my microscope and some polarizing film (which I think I may have) for my illumination.

I don't remember you touching on the type of polarizer.  Older polarizers for manual focus cameras are typically linear.  Newer polarizrs that are compatible with autofocus cameras are circular.  Every Nomarski microscope I have used has linear polarizers.  I would expect linear polarizers to work better for this, but I have no experience trying circular polarizers on microscopes.

Chris

[Old Fart Analog Engineer]

Yeah, I've found that side lighting is more effective than polarizers.  If you have a small, high intensity flashlight you can shine it on the part from the side temporarily to read the markings while leaving the microscope and lighting set-up alone.  Most of my microscope viewing is to asses solder connections, which turn to dark grey or black viewed through polarizers. 

[richnormand]

Funny...

I posted an almost identical easy add-on for my stereo microscope over a year ago:

https://www.eevblog.com/forum/reviews/polariser-for-microscope-light-ring/msg3375110/#msg3375110

and.... got zero response or reaction. So I figured its a well known technique and no one was interested ... and now a whole (well made) video about it.

I have Nomarski and dark/bright field capability and two added cross polarisers on my Reichert high magnification microscope. It makes a major difference observing decap chip interconnects and topology before going to the SEM.

[thm_w]

Funny...

I posted an almost identical easy add-on for my stereo microscope over a year ago:

https://www.eevblog.com/forum/reviews/polariser-for-microscope-light-ring/msg3375110/#msg3375110

You were using the polarizer on the ring light only for those photos and not on the camera? Or did I misread it.

[richnormand]

I was actually only using the light ring polariser for that photo.
Easy to clip on but I leave it most of the time as my light source is pretty powerful.
It might be that the prisms for the LOMO camera unit (black insert in the middle) provides some polarisation to make it work well.

I did make an insert for the middle, as shown in the photo. It does work better but most of the time I just use the light ring polariser.
Also the inner polariser is in the optical path and can degrade the image resolution as it is a cheap A4 sheet that I cut with scissors.... but it will null the light better if needed.

[rbm]

A long time back when I bought my microscope I researched ring lights.  One DIY project I stumbled upon was AZIZ DIY LED Microscope Illuminator.  This was a clever board designed by Tangent Audio, which used a quantity of individual LEDS controlled by a single chip micro controller.  By manipulating a couple of rotary encoders, the user could cause LEDs to light in different patterns casting various angles of light on the subject.  It was useful in getting these laser etched markings to appear, but without the use of polarising filters. I would have liked to build such a project but Tangent never released the design.   Here are reference URLS:

Web page:  http://www.tangentaudio.com/electronics/aziz/

Demo video: