I want to measure the amount of light striking a photodiode in a specific time window (about 1ms). In this window, we get \$10^6-10^7\$ photons, which get converted into electrons with about 80% efficiency.
The standard method of performing this measurement is to use a transimpedance amplifier to convert the current into a voltage which is then sampled rapidly throughout the time period and integrated. However, there are lots of places for noise to creep in. Each of the measurements is quite noisy, and this get integrated up.
I was wondering if there was a more accurate method of measuring the total charge produced in this window?
So far I have been considering something like an analog CCD:
- A capacitor is used to store the charge.
- When the time window is over a digital signal can isolate the capacitor from the photodiode
- The charge on the capacitor is then measured, by some method I haven't thought of yet
If anyone has any advice I'd love to hear it. Essentially, I currently have a noisy measurement of the current over time, which I would like to trade for a more accurate measurement of the total charge produced.
Edit: As some context, this question was brought up when I realised that a single-pixel CCD would actually do this job much better than a photodiode. They can have large quantum efficiencies and read noise in the 10s of electrons. Sadly, single-pixel CCD's don't appear to exist, as far as I can tell. (Also, the dark current is a little problematic, but you can always cool them down).
An avalanche photdiode (or photomultiplier) might also be better suited, but we're trying to avoid high voltage.