4
\$\begingroup\$

This might be a bit of a long shot for this venue, but: I'm looking into sensors for a scientific imaging application where the key is excellent sensitivity (quantum efficiency and noise performance) combined with low readout latency.

I don't need a lot of pixels, something like 64x8 or even a 32x1 line sensor would be just fine. However, readout of these pixels must be quick, not in terms of frame rate (throughput), but in terms of latency. Ideally, the readout latency would be well below 100 µs, so that together with an exposure time on the order of 50 µs, I'd get the result within less than 100 µs of the trigger event (on a custom FPGA board, so the exact interface does not really matter). Also, the short exposure times, compared with the fact that the observed process is rather faint in intensity, necessitate a very good sensitivity.

Traditionally, photo-multiplier tubes would be used for detecting the process, but my goal is (spatially resolved) imaging instead of just counting photons. For this, electron-multiplying CCDs (EMCCDs) seem to be an interesting option.

To give you an idea what this is all about, take a look at Andor's iXon 897 Ultra camera. It would be a near perfect match for the application, if it was not for the long readout latency of >500 µs. The main cause the long latency seems to be the fact that the CCD operates in frame-transfer mode, so that even if only a small region of the camera's 512x512 sensor is used, the image still has to be shifted through the whole storage area.

Are there EMCCD sensors that do not use a frame transfer setup? Or sensors in an oblong/line shape? The target application uses wavelengths just below 400 nm, so good quantum efficiency on the short end of the spectrum would be necessary, even though latency is the key factor. Whether it is a finished camera product or a bare sensor is ultimately not that important, as throwing together some readout electronics for this specific application would be doable.

Another product I stumbled upon is the FirstLight OCAM² camera. It seems to use a custom EMCCD sensor design manufactured by e2v with several readout stages to reach a latency of under 60 µs. However, the used sensor only has a very mediocre quantum efficiency in the near-UV, and while the website mentions that custom developments are possible, custom-ordering a sensor might be prohibitively expensive.

I still think that I'm missing a much more obvious solution, though.

\$\endgroup\$
  • 1
    \$\begingroup\$ To be honest, I don't quite get why this question was put on hold. I described the specific problem I am trying to solve (violet/near-UV light, 50 µs exposure, linear shape, low amount of pixels, short latency required). And just to avoid getting suggestions that I know won't work for me, I also included a few links to commercial products. What's wrong with that? I'm not really looking for specific products, rather for sensor technologies that I don't know might have existed. \$\endgroup\$ – klickverbot Mar 20 '14 at 11:20
  • 2
    \$\begingroup\$ This question was improperly closed. The OP did do a good job of describing his situation and specific problem, and the question is more about selecting an appropriate sensor technology than recommending a specific product. \$\endgroup\$ – Dave Tweed Mar 20 '14 at 11:34
  • \$\begingroup\$ Have you found a suitable detector for your application? I think there is actually no obvious solution, but there are some new technologies available, such as this one. This can be combined with an image intensifier to provide readout latencies in the nanosecond range for photon counting applications. The persistence of the phosphor used in the intensifier can limit the repetition rate, however. \$\endgroup\$ – Oleksandr R. Oct 4 '15 at 15:06
1
\$\begingroup\$

The optical SETI project at Harvard uses multi-pixel PM tubes (64 pixels per tube, 16 tubes total) from Hamamatsu. Would these be suitable for your project?

\$\endgroup\$
  • \$\begingroup\$ Thanks for the suggestion, PMT arrays indeed seem like an interesting choice. I had considered them before asking the question, but it seemed like cross-talk between pixels might become a problem. In any case, I'll have a look at them again if we decide to go through with this project. I also discovered that the noise characteristics of CMOS or non EM CCD sensors might not even compare so unfavorably for the short exposure times in question, so that's probably another thing to look at. \$\endgroup\$ – klickverbot Apr 5 '14 at 14:40

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.