Reflector Gunsights: the Fighter Pilot's Friend
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- เผยแพร่เมื่อ 21 ก.ค. 2024
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Reflector or "reflex" gunsights utilize the principle of light collimation to give the shooter a parallax-free aiming reticle and improve target acquisition. In this episode I look at a pair of WWII aircraft gunsights and a modern 'red dot' optic and discuss their operating principles and 120-year development history.
Special thanks to Matt Heintz and Gord Crossley for providing the vintage gunsights shown in this video.
Great explanation! The important thing to remember is that the image of the reticle-or the data in the HUD- is at infinity. So the pilot’s eye focus is on the image and the target at the same time, and both are in focus. Thanks!
Insightful comment!
i have one of those cheap chinese red dot sights for my paintball gun. it took me a little bit to realize you can't focus your eye at the glass - it's not like a layer of glowing paint on the optic. you have to focus your eye in the distance at the target and then the reticle will appear.
Optical infinity to be precise, so not really infinity, since that'd mean the rays were completely parallel and thus an image never formed. Instead a limitation of human eyesight is used, where our eyes' ability to adapt the lens shape beyond certain distance falls off dramatically. Looking at an object 100m away, 50m and 20m they eye does little to virtually no adjustment. For most humans as far as I know the distance is around 8m, give or take. Set the optics up so the reticle (virtual) image appears 10-15m in front of you and voila', you can observe your target and simultaneously see the crosshair in full sharpness without your eye having to adjust constantly
O i always wondered how that woud work if that was not a thing
@@Rigel_6 Learn something new every day. Thanks! I hadn't thought about the interaction between perfectly parallel beams and your lens. This also makes me wonder if someone who is mildly near-sighted, say has trouble with things beyond 50m or so, doesn't actually have a lens or muscle problem and instead just has a lower "resolution". That is, a lower rod/cone density on their retina. It wouldn't be noticeable up close, but their far distance vision would be impacted.
This means whenever we shoot firearms with reflex sights, we can pay homage to our predecessors by making fighter airplane noises.
Exactly !! ✌😎
You mean to tell me you haven't already been doing that??? I don't believe you.
Bro that's the only way I can eat
EEEEErrrruuuummmmm bam bam bam
yeah I already do this
Well researched and fantastically presented. However, when it comes to modern sighting systems, I can offer a bit of help as this is my area of expertise and how make my living. The type of sight that you displayed is called a reflex sight and does not use a laser of any type. It does use a decently efficient LED which sits behind a small shield that has openings in the shape of a reticle, or 4 reticles in the type that you showed. The coatings on the lens is the primary method for reflecting the illuminated reticle back to the shooter's eye. The 2nd type of sight is the prism sight, which uses a prism to make the LED illuminated reticle visible to the shooter and has the advantage of having no distortion when viewed by persons with an astigmatism; and the more expensive versions of the last 2 types of sights have highly efficient LEDs giving them a battery life in the thousands of hours range. The 3rd type is an older type that isn't popular at all and you may have showed a version of it; this 3rd type requires the use of both eyes open when aiming which is called the "Bindon Aiming Principle" and as you stated, the dot should appear over the target. If you have any kind of eye dominance at all, it usually will not work. That type also, used early LEDs. Then there is the 4th type, which is the "Holographic Weapon Sight" and this does use a laser and is what Eotech, Specializes in making. Thank you for the great content!
I use the Bindon method you mentioned to train new shooters on using lit reticle optics. I put tape over the downrange lens. It forces the person to open their left eye. The Bindon principle means your brain places the dot even though you can't see through the sight.
You mentioned an eye dominance issue, but I have been using this method for 15 years as a shooting instructor, and I've never ran across a shooter that couldn't figure it out.
Although the line from solid state laser and LED is not that great. That mostly consists of how the the LED is constructed. LEDs are still extremely monochromatic and if you use a laser diode then the signal is already columnated (and coherent).
This should be pinned to the top.
Thank you. I was watching an episode of 'Dogfights' the other day, and one of the pilots had an issue with the light bulb in his gun sights burning out, rendering it useless. I didn't know how a reflector gunsight worked, so this was a great education for me, and I appreciate it.
When I play il2 (ww2 combat flight sim) a clear piece of glass isn’t the worst thing to sight through because the rounds have tracers and I can focus on where the rounds are hitting my target and use the tracers to dial in my shooting. Obviously it has its disadvantages in that the first few rounds aren’t as accurate.
Note that with World War I fighters with twin synchronized machine guns, there was typically not one set of iron sights but *three*, you had the ring and bead central sight, but also notch and post sights on both machine guns. To get truly good gunnery (there were no explosive rounds and planes were largely hollow, so hitting the fuselage or wings often had fairly little effect--one had to shoot out the pilot or the engine block to score a quick kill, whereas a 20mm could cripple most WWII planes with a glancing hit and a 30mm could blow them apart), one had to learn to constantly switch among the three sights. To fire at an enemy directly ahead, one would use the central sight to train both machine guns more or less on target. For an enemy passing across the field of view, one would train the machine gun on the side the enemy was about to cross, forcing him to pass through the line of fire of at least one gun. When I flew Il-2 Flying Circus in VR I would practice during cruises lining up the various sights, sometimes giving myself a headache from the constant focusing and refocusing of my eyes (VR is not like a screen, things actually appear closer or further away and you focus your eyes accordingly) or neck pain from craning and recraning my neck with two pounds of plastic hanging off my face!
This was very informative and exactly what I was looking for, thanks!
I expect the dichroic coating on the mirror also reduces the amount of light from the LED that projects forwards, an important consideration if you're playing How Not To Be Seen at night.
The sight in the modern HUD also includes a CCIP or continually computed impact point which really does make deflection shooting far easier
CCIP is for bombing, not for deflection shooting.
Awesome explanation. Thanks to those for the loan of the equipment used.
wow, now i FINALLY understand how red dot sights work and probably how something like a google lens or AR glasses in the future will work - collimated light! and i've always heard that the image was placed "at infinity" but i didn't really understand what that meant... until now! ahhhh... the light rays are parallel and so there's no parallax! why didn't they say so! thank you much! that was very very illuminating (ba dum cha) and educational!
The detour about night active insects was amazing! 🥰
nice... always wanted to have a closer look one of those. you always come around with the good stuff, again and again! keep it coming!
Good overview!
It would have been worthwhile to mention that the collimator/beam splitter in the modern sights is a zero power meniscus. You mentioned the concave face, but the diagram suggested a flat front face. Such a piece of glass would be a negative lens, and hence deliver an image of the target very significantly reduced in angular size. In actuality, these parts have a constant thickness, where the front face is convex and with a similar radius of curvature as for the rear concave face. Think of it as a formerly flat piece of ordinary window glass that has been slumped to form a small section of something like an observation dome.
Cheers!
I would think that the concave surface is an off-axis segment of a paraboloid. If it were a simple sphere the dot ray vector would be pretty aberrated, a kind of parallax error. The outer convex surface would have a complementary parabolic shape, keeping it a zero power window. This is easy to do with mass produced molded plastic optics.
As the owner of one of these (very cheap) reflex sights, it is in fact aberrated as hell @@randydewees7338
That what I was gonna say
Pilots and others who shoot and aim guns during WWII needed to appreciate that aiming at a moving target at an angle to your line of sight would miss the target because the by the time the projectile, bullet arrived at the target , the target would have moved on. So shooters were given some instruction on shooting shotguns at clay pigeons to appreciate that it was necessary to lead the target with your firearm, something that every trap shotgun shooter knows. Of course, the gunsights you described took care of that later on. Love your videos on such a wide range of topics.
Thanks for the moth explanation! In my "Rise Of Flight" WW1 flight sim I earned a collimator gun sight for my Albatross DVa. Thanks for making clear to me this was not an exaggeration!
As usual with Gilles, an extremely clear and systematic explanation of a complex device.
I've watched this video several times. It's just SO well done, and a brilliant piece of history, at that. THANK YOU
Excellent. I am just about to commence restoring a battered Mk3 gunsight like yours. Nice to see one getting some visibility on TH-cam and learn a bit more about it's history & operation. Thanks.
Easily the best explanation of sights I've seen. Thanks
Well made and easy to understand video! Didn’t know reflex sights were that old or how they worked, now I do!
Way more interesting than I thought it would have been. Well done.
Bravo! Thanks for the show
Something I’ve tried to understand for years and you finally explained in a way that I comprehend. Thank you
Interesting to see how to operate the optic sight for mortar. Because it is very similar to recent trending technique in the sport shooting that the shooter obscure the glass with the tape and so the optic becomes opaque and cannot be seen through. Only the reticle is seen. This force shooters to use another eye and consequently force them to shoot with target focus (vs. unintentionally focusing on the reticle).
Awesome video! Thank you! I always wanted to know how the WW2 sights were designed!
Excellent work! I studied WW2 for decades (amateur based of course) and I learned a lot today!
This is cool, once you showed the view at 5:41, I was like "oh, I added one of these to my telescope". Granted much smaller and powered with a coin cell, but yeah, same thing with a reflected reticule on a piece of glass/plastic. Makes targeting objects on the fly a lot quicker than the spotter scope.
This is beyond incredible! Thank You!
Loved the video! Got to play with one of these at the RAF Museum in London, was super cool!
Best explanation ever, I saw the same explanation several times and always forget it, but the way you did it I will remember forever.
This presentation style resembles "Fun with flags with Dr Sheldon Cooper",to me, but somehouw you made it really fun to watch, thank you for that and congratuations.
Very VERY interesting video and content. Thanks for developing and sharing!!!
Excellent video, thank you very much. By the way, Brittain had active gunsights in the first world war already: a very cleverly disigned frontal post that moved with little wings in the airstream of the plane. They were designed by a scientist and produced by the gunmaker James Purdey & Sons. Purdey still has one on display in their famous "Long Room". Maybe the subject for another video? Regards sincerly Yours Malte.
Britain* (only one t).
Wow! What an interesting and well-presented video!
Before i was wondering how do the hud and reflex sights work but then this video popped up and so i pressed it now i under stand it's surprisingly simple thanks!
Thanks for this video. I learned a great deal. I just stumbled upon your website. I have subscribed and look forward to seeing your videos.
Fascinating history and great presentation! Subscribing. Thank you!
Thank you, awesome explanation
A great example of parallax can be found in the old video game Rocket Knight Adventures by konami. If you watch the background rolling by you'll find a perfect illustration of the effect.
I just discovered this channel, and I am impressed with how you present the well researched material in a concise way.
I have subscribed and shared this site with friends who have interests that will be satisfied by your content. Thanks!
the intro music... promenade by Mussorgsky.. my handy ringtone 🙂 greetings from Mallorca, Spain !
Thank you. Awesome video
How do you not have more subscribers....excellent channel.
Thanks very much!!! Cheers from Brazil.
Parallax is why a good analogue sweep scale has a mirror behind the needle.. the lack of a mirror on an analogue car speedometer means that taller people and shorter people see different readings and cannot properly adjust..
Modern head up displays (HUD) work in the same way, except it can displays changing live data such as altitude, airspeed, artificial horizon and weapons reticules. The key thing is they’re focused to infinity so that the pilot can read this data without having to refocus from what he’s was looking at outside.
Edit: I’ve just seen this mentioned at 9:28 notice the black circle and black crosshair in the top right corner of the HUD? That’s to harmonise it so the HUD is perfectly inline with the the aircrafts centreline, gun barrel, radar boresight etc.
The black circle and crosshair I believe, is there to aid the pilot in adjusting his seat (the ejection seat can be moved up/down to accommodate different sized pilots), so that he/she gets the proper "sight-picture". That's what an F/A-18 pilot told me (the Hud is that of an F/A-18 Hornet Fighter.)
I love the music at the start.
I never expected such quality content from a channel with a minion in its profile picture.
Really well done!
Super interesting, thanks
Not sure how this landed in my suggestions but I'm glad it did!
Thank you. Nicely explained and interesting. 🙂
Long time ago, there was a guy on YT, who made fully functioning replicas of firearms out of paper and superglue. At one point he even made a red-dot sight, again mostly out of paper. There were steel springs and some other small bits, but most of the result was paper and superglue.
Obviously the cartridges (another part not out of paper) were underpowered - just strong enough to cycle the action. And he made a bunch of different ones. It was incredible to see. He made a paper rifle and a paper 1911 and more. But I guess it goes against YT ToS now... I wish I could find his videos somewhere.
Was it Tacome1942? I have a video of his about a paper m1903 saved in my to watch Playlist from about 7 years ago lol.
Great explanation - thanks.
thx for such a clear explanation
Very Interesting. Thank you
Your channel is so interesting I headed over to Patreon after about the 3rd video!
Fascinating, thank you
Great job
Brilliant video.
Excellent!
Really interesting!
I once read that collimators such as you describe for mortars, requiring the use of both eyes and looking in a specific way, were also initially used on small arms, but only in some special and anti-terrorist forses and most people did not know about it. I don't remember exactly why they used this solution. Maybe so that the light would not be visible to the opponent? Anyway, it was a short experiment.
They were simply the first ones available for mass production, when normal collimated sights like the aimpoint electronic came out they quickly replaced the two eyes required type.
Thank you Gilles. Viewing your videos, I am always impressed with the consistent clarity of your perception of the subject and particularly with your ability to present with equal clarity a cogent explanation unimpaired by anything that might cloud the explanation for the viewer. You are talented on more than one level, my friend. Chapeau!
I love the choice of Promenade from Pictures for the title. 🙂
Very interesting and well explained! Subscribed!
Ya that piece helped a lot.
this was highly informative, thanks a lot :D
Very interesting to learn the mk3 is British as its used on multiple US Gun's likenthe quad 50 cal set up they had in the m16 meat chopper etc it's attached to the top crossbar whare the gunner sits in the cradle!
I'm looking for a B1 stukas Gun sight!
Very cool video. I had no idea who moths were attracted to the light. That information was also interesting. What is that music piece at the start of the video? I know I should know it. I've forgotten what it's called.
It's the opening to Mussorgsky's "Pictures at an Exhibition"
These were the progenitors of the heads up display modern fighters have.
Probably best to say Cold War era fighters have.
HMD’s are the modern standard.
@@JustanotherconsumerEvery model of fighter aircraft currently operating around the world, except for one, has a heads up display. And most modern fighters began development during the Cold War, making the distinction largely meaningless/nonexistent anyway. The original comment is best just the way it is.
Thank you.
Wow! This is a pretty good channel I have several reflex sights ,vroom vroom.
Your channel is one of my fav new channels! You are like a personal museum guide!
Very interesting
Pretty cool. Thanks :)
dude very clearly explained video
I love the music! I think it's the Prince of Denmark march aka Trumpets Voluntary.
There are in fact two explanations in circulation about the name head-up-display. One is the one you've given, that it allowed the pilots to keep their head up, the other one centers on the fact thar it eas a display facing up instead of towards the pilot
Ive used heads display up in car and was a great benefit keeping your eyes on the road situational awareness was improved greatly should be mandatory as are optional and rare from australia
A few years ago I had a car where the dashboard backlight didn't work and I couldn't read the speedo needle in the dark. I got a phone app (Digihud) that calculates speed from GPS and can display it as mirror-image number. If I put my phone on the lip of the dashboard, it'd rest there securely and the digits were reflected right at the top of the windscreen. it was great!
An interesting trivia item is that heads up displays in cars are usually not focused at infinity, but are imaged closer. They found people tend to run into things when the displays are focused at infinity. The display on my car's HUD appears to be at the distance of the front bumper.
Excellent. I didn’t know 80% of your presentation . More than very good!
What is it about this guy that makes me learn so much
I was hoping you'd cover Holographic optical element huds.
Very nice. :)
thank you
2:40 I googled that and the top result was "the idea that moths are trying to navigate by the Moon has been disproved. Exactly why moths fly towards artificial lights still isn’t understood - all we know is that artificial lights confuse them in some way" from the BBC.
Awesome video man!🙏🏼🙏🏼🙏🏼
'Yeah, man'.
Very interesting- I've never really looked into how a reflex sight works, and it's great to finally know. It's way simpler than I thought- seeing the lenses and such inside some of them made me think it was rather more complicated.
I don't know if you can really say the GGS Mk II was 'incredibly successful' given that it didn't really increase the RAF's victory to loss ratio at all, as far as I know. The Luftwaffe didn't seem to find a need for calculating gunsights until quite late, and they maintained a very good victory to loss ratio. The Revi C/12D and Revi 16A / B sights employed a very elegant solution by simply designing the reticle to be a measuring device; so a given plane would fit into the circle x number of times at y range, and the circle and marks on the crosshairs would help determine the lead necessary. Easy enough for pilots to learn and required no adjustments to be made in combat or intricate machinery in the plane itself. Although that being said, most pilots were simply smart enough to recognize that the closer you get, the more hits you'll score ;) And turning battles were always less than ideal.
I've always thought it highly suspect that a pilot in action would be able or want to fiddle with the sight while trying to maueuver with an enemy plane. I'd love to hear the experience of a real veteran as to how he used his sight...
What mechanism is used to shrink and enlarge the reticle in ww2 fighter aircraft? You turn the knobs and stuff to adjust for range and wingspan but how does the reticle get bigger/smaller? Something to do with electricity/resistance or something?
The light from the lamp was bounced off a mirror whose angle was controlled by the gyroscope, providing the deflection offset. This mirror in turn was covered by a pair of discs cut with a pattern of radial slits - one with straight lines and the other with logarithmic spirals. Where the two slits intersected, light could pass through to form a diamond-shaped point of light that was projected onto the reflector glass. Turning one disc relative to the other caused the diameter of the circular pattern of diamonds to expand and contract. You can see for yourself in this patent:
patentimages.storage.googleapis.com/dd/16/42/facd8206dc4d12/US2527245.pdf
@@CanadianMacGyver I see... What about other parameters like aircraft speed, temperature, wind speed, etc? Were those compensated for as well by the device or just gyro offset?
Also, how difficult would it be to build such a device in your spare time, like a home project or something?
@@ivvan497 As far as I am aware, no other parameters other than rate of turn and range were compensated for. Aircraft speed was irrelevant as both aircraft would be flying at around the same speed (only turn rate is relevant to making a deflection shot), the effects of air temperature on bullet trajectory are minor compared to all other factors, and wind can't meaningfully be measured while in the air. Indeed, to this day the only way of gauging wind speed and direction while flying is to measure your aircraft's drift relative to the ground.
As for how difficult a gyro gunsight would be to build, I would say pretty difficult. While a basic reflector gunsight is simple enough, gyroscopes require a lot of precision machining to get them to balance properly. About the easiest way I could think of to build a working gyro gunsight would be to cheat and run the deflection compensation mechanism with an off-the-shelf set of electronic accelerometers.
I believe the German EZ.42 reflector gunsight had settings for altitude as well.@@CanadianMacGyver
Canopy projection ones are cool
Alright smarty pants. you got my sub ! haha great video !!
So why does the reticle move around relative to the corner of the sign when he moves the camera around?
I noticed that those vertical reflector sights in front of you have flat glass. Was that a problem, and/or did they have a fix for that?
Why would it be a problem that needed a fix? They used lenses to do the collimation and flat glass as a semi-transparent mirror. It wasn't until much later that the lens and mirror functions were combined.
5:26
Looking down the working sight
Very well presented. Thank you.
Vell done !! 👍
The first one was done in WW1?! The mind boggles 🤯
The first reflector gunsight was called the: OIGEE (oigee )
The large gunsight is a Mk III not a Mk II and the small one is a Mk III n. The Mk II does not have the sight glass angle adjuster.
What is the music in the intro?
Does anyone happen to have the source for that K-14 gunsight illustration at 8:46 ?