new thermomechanical terahertz detector

Sounds like a little Golay Cell

George H.

It will be interesting to make an imaging array of these things. Will all the resonators talk to one another, like several pendulums on a table?

How does one excite and read out, say, 100,000 micro-mechanical oscillators?

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Perhaps you could make an array of N**2 oscillators of sufficiently different frequency that they wouldn't lock together, and then tile the arrays. That way you wouldn't get nearest-neighbour locking. It'll obviously need a pixel-by-pixel calibration.

Alternatively they could drive all of them at one frequency and watch the phase of the response of each pixel.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC 
Optics, Electro-optics, Photonics, Analog Electronics 

160 North State Road #203 
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hobbs at electrooptical dot net 
http://electrooptical.net

The existing FLIR type uncooled sensors need individual pixel cal. Mine flips down a shutter about once a minute, for a few seconds, to do that. They probably hide bad pixels too.

That's good. Blast them all together to get them going, then watch them ring down. It will still be interesting to do that.

It would be great to have a cheap hi-res thermal imager.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

A vidicon tube addresses photoconductors with comparable numbers of elements, so maybe you could print a wafer with all the oscillators you need, and power them, then look at one-at-a-time by projecting an e-beam to bias (one at a time) the output buffers to a single line. Multiplexing is too much (CCD is a shift register, not a mux, scheme). Scanning, though, is an old reliable technology.

It'd be too much, too, to put an FM decoder per pixel, driving one LED per pixel.

Isn't, or wasn't, there a projector that used an array of mirror elements to reflect a light beam and generate images? No doubt superceded by LED arrays...

Mike.

DLP projectors work this way. They're very common. People have even done homebrew stuff with the "micromirror" arrays.

Fun fact: If you get a DLP projector securely mounted and accurately focused on a nice flat screen, you can walk up to it and look closely, and see not only the pixels, but the focused images of the microscopic hinges that they swivel on.

Mike

Yes, TI made that called... I forget, some three letter abbreviation. Goog le says it was DLP. It was cheaper for the larger size I believe, but poor er picture and larger cabinet. The apparatus was in the bottom and project ed upward if I remember, so it was still nearly a foot thick.

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  Rick C. 

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On a sunny day (Thu, 16 May 2019 13:08:30 -0700 (PDT)) it happened George Herold wrote in :

Yes, but this is different, It uses MEMS frequency change. I have posted in relation to my test with the MPU6050 as inertial navigation accelerometer and its extreme sensitivity to temperature variations I find it cute how they now use that temperature sensitivity for the good by simply coating it with NiCr. Can be made microscopic small, lots of bolometers per surface area, maybe a sort of camera is possible for those frequencies,

On a sunny day (Thu, 16 May 2019 13:25:35 -0700) it happened John Larkin wrote in :

Yes, good point, resonance!

In series like a musical composition?

>

On a sunny day (Thu, 16 May 2019 15:54:17 -0700 (PDT)) it happened Rick C wrote in :

DLP projectors are common, some use those to make PCBs:

On a sunny day (Thu, 16 May 2019 16:33:24 -0400) it happened Phil Hobbs wrote in :

Cool!

Sure, the TI digital micromirror device (DMD) arrays. You can get them from Digikey. You can do a lot of interesting things with them.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

What's the response time? If it's faster than the expected rate of change of temperature all over an image, just have one detector and scan an image over it.

Mark L. Fergerson

There's a huge SNR hit from doing that.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

Thermal time constant is about 55us, they say.

The article is about a GaAs beam, about 100um long and

25um wide, suspended at both ends. The mechanical resonance frequency is about 500kHz. A piezo-electric capacitor overlaying each end serves to inject or sense mechanical vibrations. The Q factor is about 6k in vacuum.

The resonance frequency varies with the beam temperature. They characterize the sensitivity by passing a current through a NiCr layer deposited on the centre of the beam. The change of frequency is about -40kHz with 1mW dissipated in the NiCr layer.

The NiCr also serves as the absorbing target for THz radiation. The minimum detectable THz power is said to be about 200pW.

Interesting gadget.

Jeroen Belleman

Crazy idea: put them in a vacuum and scan an electron beam across them.

Kind of like this:

Mike

Early digital telephone systems use a vacuum tube companding ADC, with an electron sheet hitting a grey-code target.

Tek sold a scan-conversion-tube digital oscilloscope that had 7 GHz single-shot bandwidth. I think Greenfield in France still sells them. I have a tube!

I think the Whirlwind computer at MIT used a CRT RAM.

One of the favorite things in my life is the 50 GHz Tek 11802 sampling scope on my bench. It's the last thing in our place that uses a monochrome CRT.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

The eye is a very good filter. Besides, you only have to be "good enough". This is engineering after all. Either it meets the requirements or it doesn't.

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  Rick C. 

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