This is fascinating. I didn't realize there are so few cone cells, that you can step through literally *all* of them with a digital controller.
- "These laser microdoses are delivered at a rate of 10⁵ per second to a population of 10³ cones[...] individually fiber-coupled acousto-optic modulator that can modulate laser intensity up to 50 MHz[...] This laser spot is scanned in a raster pattern over a 0.9° square field of view using orthogonally oriented resonant and galvo mirrors, with a frame resolution of 512 × 256 pixels and a frame rate of 60 Hz..."
About 90 millions rods vs 6 millions cones. Sometimes I'm surprised we can even see detail at all. Though it certainly helps that they're not uniformly distributed; most cones are in the macula, around the middle of the back of the eye. Still, it's not a lot.
And within the macula, the red and green are generally towards the centre and the blue are generally towards the edge. This helps prevent the red shift problem photographs with high contrast changes sometimes get.
They didn’t literally step through all of them though (only a patch “about twice the size of a full moon”), and I’m not sure if they even stimulated all M cones within that patch.
- "These laser microdoses are delivered at a rate of 10⁵ per second to a population of 10³ cones[...] individually fiber-coupled acousto-optic modulator that can modulate laser intensity up to 50 MHz[...] This laser spot is scanned in a raster pattern over a 0.9° square field of view using orthogonally oriented resonant and galvo mirrors, with a frame resolution of 512 × 256 pixels and a frame rate of 60 Hz..."
https://www.science.org/doi/10.1126/sciadv.adu1052