Light intensity seem to increase with lower frequency

Hi,

when writing sessions and later testing them, I have noticed, that I apparently have to manually turn down the light intensity with falling frequency. This is non-relaxing and so not OK for a mind machine.

Example: I start the session in the normal beta-range at some 14 to 20 Hz and then slowly ramp down to the target frequency at say 2,5 Hz for sleep..

When I write the session I want a constant stimulation, so I program a general intensity of say 10 in the editor.

But when I listen to the session and adjust it for comfort during the first say 2 minutes (not during the 30 second soft lead in) - I later at the target frequency - and actually several times on the way down - have to manually turn down the light intensinty. This I find quite non-relaxing, but if I don't I will never fall asleep, as the light gets quite intensive.

Does the Proteus not have a constant "duty time" i.e. on 50 % of the time - off 50 % of the time - on 50 % of the time ........ - at any frequency?

I have another mind machine - and one more for pc - which I don't have to adjust more that once at the start.

This is not a question the eyes being more sensitive when one is relaxed at the very low frequencies. If I make a session of pure 20 HZ and compare it to a session of pure 2,5 or say 40 Hz, the problem is the same. If I program the same intensity the higher frequency always is experienced as less intense.

Kind Regards

MindMan

Hello MindMan,

At full brightness (15) the duty cycle of the driving waveform is 30%. As the brightness level drops the duty cycle drops 2% per step.

As the frequency of the lights slows there is a point where the iris starts dilating and contracting in time with the flash rate rather than responding to the overall brightness. This adds extra stress to the muscles controlling the iris. When they tire it will be perceived as being too bright. The best way to compensate would be reduce the brightness as the frequency drops. Also you might try using the green LEDs (if you are using red/green glasses) as they don?t come across as being so bright.

Best regards,
TheRock

Hello, Mindman--

The brightness for the pulse waveforms generated by Proteus are modulated to control brightness; what you may be noticing is the fact that a 20% duty cycle at 20 hz will appear dimmer than the same duty cycle at 4 hz since the "on" portion of the pulse grows longer at the session start. Frankly, no one has complained about this before so we haven't looked at how to modify it (which is possible). You can fix this by editing the sessions you are using and decreasing the brightness during the segments that seem too bright to you, using the Proteus Editor software.

Hope this helps!

Robert

Hi TheRock and Robert,

I think, that you have answered my question nicely.

I.e. the light energy output of the goggles is constant (constant duty cycle) at any frequency.

You don't tell but I asume that the diodes are so fast, that there is no problem for them obtaining full power even at the fastest frequency.

So the light power output is actually constant. The problem are the eyes' retina at low frequencies. The retina relaxes during the relatively long pause with no light pulse - and when the flash comes lots of light comes into the eye - and so the retina contracts violently. The diodes are in case of the Proteus furthermore mounted directly in front of the retina. This augments the flashing problem in itself - and explains why I have not experienced the same with my other mind machine. On that one the diodes are spread out around each retina - and there is a semitransparent screen between the retina and the diodes.

This is very much my experience with audiostrobe as well. Sometimers a low frequency lonely pulse comes - and feels like stroboscopic light. And the eye contracts.

By the way I of course knew how the editor could handle this problem - but I still have to figure out the right level by myself for each frequency.

Thank you again very much.


Kind Regards

MindMan