Liz suggested that we should ask for things to bring a bit of pressure on image sensor manufacturers - so here's my input.
Having no filter on an image sensor allows the use of an IR-passing filter instead of the IR-blocking filter which now seems to be standard. Passing IR would lead to all sorts of interesting stuff - like detecting a pulse (or continuous beam) of IR light directly from an IR laser diode or bounced from an IR laser diode. IR laser diodes, as a cylindrical module complete with adjustable collimator lens, are extremely low cost. We found that getting diodes as modules from Taiwan was less expensive than getting diodes alone and making our own modules with them.
IR-passing filters are dirt cheap to make. Take a roll of Ektachrome slide film (still available in professional packs in 35mm upwards), DON'T expose it, and get it developed. Tell the company doing the processing that you know the film appears to contain nothing and you don't want the film cut up - just returned as a roll. You are now in possession of enough IR pass filter film to go in front of thousands of image sensors - if only they did not have an IR blocking filter already on them! ( ... and, no, you can't get the IR blocking filter off.)
A filter-less sensor opens up another requirement which may not be possible with the RPi GPU - getting at the stream of raw pixel data in real time, at real speed, to detect when and where this IR pulse was seen. We do this in one of our products using an Atmel AVR to process the raw data in real time. The speed of the processor is a function of the resolution of the sensor - not everyone needs megapixels when sensing things like IR pulses - we could do it with an AT90S2313 - now the ATtiny2313A.
There used to be loads of low resolution (say, 356 x 292) image sensors that allowed this - they were mainly aimed at the mono security market. Trouble is, the security market has gone colour (maybe burglars look prettier in colour?) and increasingly hi res colour at that, and almost all manufacturers integrate a IR filter.
There are loads of posts on loads of forums all over the Internet asking for image sensors with NO filters so they can be used for all sorts of educational and development projects and new products. Trouble is, manufacturers are deaf to this requirement so the door has been totally slammed on innovation in this area.
The RPi Foundation, with its obvious volumes, could easily persuade a manufacturer like Pixart (http://www.pixart.com.tw
) to do a run. We have found them to be an excellent supplier in the past - but they no longer have a part to do the interesting stuff.
Fixed v variable lenses is not such a problem - unless you want to get in really macro-level close - then things get horribly blurry with a standard lens.
Life's single regret: not patenting dongles when we invented and named them to protect the Wordcraft word processor on the Commodore PET!
You can buy 31 RPi3s for the £639 price of one Samsung Galaxy S7 Edge smart phone - who buys this stuff?