Hey Mooreshire,
Thanks for replying. I know this is a huge undertaking, but there's a couple things that give me reason to think it can be done. First of all the headlamp does not need to be sterilizable. It's never sterile and does not need to be sterile. It never touches the patient, and never touches the sterile parts of our garb or setup. But I agree with everything else you mention. They do have to have an adjustable focus, which I think just changes the aperature. And the color in general i think is set at ~1600K or so, which is the whitest light that gives the best color rendering. The light doesn't need FDA approval to in order to be used in the OR. Just like when we wear "loupes" which are basically mini telescopes attached to glasses- do not need approval either since they do not touch the patient.
I'm excited about your project! I'm also glad to hear that it won't have to comply with any sort of certification process. Perhaps the lamp in my collection was intended for messier work or some such, as it is constructed out of surgical materials like titanium and ultra-high-molecular-weight polyethylene. Its zoom is the very same sort of sliding aspheric TIR optic arrangement found in many flashlights, but it's a step above any optic I've seen in a flashlight in terms of its beam's smoothness and sharp boarder with complete lack of spill. Its head is also very narrow (25mm at its widest), so that it doesn't obscure your vision when positioned between your eyes (for true coaxiality when peering into shadowy incisions
) like that Cyclops XLT 225 model's fatter looking head seems it would. I have seen medical headlamps (on a dentist and their assistant, if I'm recalling correctly) which didn't look totally sterilizable but which had their heads wrapped in some sort of disposable plastic - that would be a good cleanliness solution for when you needed to reach up to adjust the angle or zoom (I know you said it never touches your garb but how do you adjust it sans hands?). Unfortunately a plastic wrap would keep a hot diode from getting the air circulation it needs to keep from overheating.
The diode you inquired about is 51mm wide on its bare board and would require a hefty hunk of heatsinking to dissipate the huge amount of heat it produces (literally an 85 watt space heater on your head) - and that heat would then be dissipated right onto your face, whereas the hot bulb in the traditional design is off in its own box leaving only the relatively lightweight lens, fiber optic cable end, and tilt mechanism on your head. A compact 1000 lumen lamp might run at that brightness for an hour off of one common li-ion battery and barely add any sweat to my brow or weariness to my neck in the process, but if you wanted to run longer at double that apparent brightness (which would require 4000+ lumens) you would of course need a significantly larger battery pack to be guaranteed to last a full surgery at that output level and a way larger heatsink which would stress your brow and neck. If you can get the size of the head down to work sitting coaxial between your eyes and keep the heat output and weight/balance to within what you think you could comfortably wear for the length of time required then you could be good to go. I'd still run everything by your school's technicians of course.
Color accuracy and color temperature are independent; a perfect color rendering source can be any temp - the star we're closest to burns at 5800K, but different atmospheric conditions filter that to a wide variety of warmer color temperatures at the planet's surface but the color rendering accuracy of sunlight is never reduced. I do wonder if it will matter whether your headlamp's light properties match the other lights being used in the room, as light sources with different CRI/temps rarely seem to mix particularly well. For example, when examining (and photographing) minerals inside caves I prefer to have only my fancy custom Nichia219-powered lights trained on my subject, and when a companion wearing a different light looks over it usually seems to screw the colors and textures up - but my eyeballs can tell that my lamp (CRI:92) is still less color-accurate than sunlight (CRI:100) or even a medical-imaging-grade Ceramic Metal-Halide bulb (CRI:96). It is easier to have all your equipment take the same model CMH bulb than it is to find perfectly matching diodes, especially if those diodes will be shone through any sort of optics which could themselves alter the light properties. (Different optics alter different properties in different ways, such as refracting or shifting the color temperature or producing beam artifacts or uneven brightness.) If you're the only person trying to shine a light into the skull in question and a mismatched overhead light isn't an issue, then I doubt <10 CRI points or a different color temperature will make any practical difference.
I work as an imaging technician at a liberal arts and environmental sciences college designing illumination solutions for projects ranging from moviemaking to microscopy and I collect headlamps for fun because of my interests in the history of mining/caving/outdoorsmanship technologies and I know
absolutely nothing about surgical illumination. You should inquire around and try to find someone who has worked on designing surgical lamps and I'd bet they'll be excited to talk to you about the challenges you will encounter. Companies love getting inquiries from academics; email a few and I bet some enthusiastic PR person will get you in touch with an equally enthusiastic engineer.
Good luck with your project, and please do keep us updated! (Yeesh, I sure do love parentheticals don't I? lol!) Oh, and :welcome:!
