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Optics, Mounts, Rails and Sights If it aims your firearm, post about it here.

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  #1  
Old 11-01-2007, 7:39 PM
Kostya Kostya is offline
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Default HOLOsight vs Red Dot

What are the differences between the two in terms of technology, use, and effectiveness?
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  #2  
Old 11-01-2007, 8:04 PM
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This has been covered extensively.

A lot of people (incorrectly) use the term holographic. EOTech is the only true holographic sight. The other red-dots either use a dielectric mirror (mirror that only reflects the wavelength of light for the dot) to reflect the light or a reticle that's illuminated.

C-More is an example of an open dielectric optic. Aimpoint is a closed tube dielectric.

Downsides and upsides are as much a part of the optic brand/model as they are the specific technology.

Search on Aimpoint vs. EOTech to get started...

For my money, I prefer EOTech -- the reticle is faster, more precise, easier to see, adjusts dimmer and brighter in range and it costs less. The battery life of an Aimpoint is better.and it's more waterproof.

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What are the differences between the two in terms of technology, use, and effectiveness?
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  #3  
Old 11-04-2007, 3:42 PM
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I have to jump in and correct this. EOTech is not a true holographic sight like the manufacturer likes to state. The only correlation to true holography is the VCSEL laser diode component which in itself, cannot record or display 3D representations.

So in short, EOTech does use holographic technology, but in itself, it is short of being a true hologram. I really doubt a hologram would be beneficial but probably the opposite in this application.

However, I prefer my EOTech over my Aimpoint as I find the EOTech image (outer circle and inner dot) better for target acquisition. Althrough, my Aimpoint is no slouch either.
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  #4  
Old 11-04-2007, 8:02 PM
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Quote:
Originally Posted by stator View Post
I have to jump in and correct this. EOTech is not a true holographic sight like the manufacturer likes to state. The only correlation to true holography is the VCSEL laser diode component which in itself, cannot record or display 3D representations.

So in short, EOTech does use holographic technology, but in itself, it is short of being a true hologram. I really doubt a hologram would be beneficial but probably the opposite in this application.
I disagree with stator in this. I've got the EOTech patent (US 6,490,060) in front of me. It shows all the components in detail, and clearly describes and illustrates the use of a hologram (#22) to bend the direction of the laser beam toward the viewer. Only a diffractive optic can do this. The optical design also uses a holographic grating (#20) elsewhere to compensate for dispersion cause by the hologram.

The hologram is the reason EOTech was forced to use laser source instead of an LED (the spectral width of this hologram is apparently very narrow and requires a similarly narrow source). Lasers need more current than LEDs and therefore have a shorter battery life.

Bruce
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Old 11-05-2007, 2:09 PM
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Yup. This is the correct information. Not that the general public even cares about how it does what it does.

The window of an EOTech is a diffraction grating that's made holographically.


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Originally Posted by bruce_ventura View Post
I disagree with stator in this. I've got the EOTech patent (US 6,490,060) in front of me. It shows all the components in detail, and clearly describes and illustrates the use of a hologram (#22) to bend the direction of the laser beam toward the viewer. Only a diffractive optic can do this. The optical design also uses a holographic grating (#20) elsewhere to compensate for dispersion cause by the hologram.

The hologram is the reason EOTech was forced to use laser source instead of an LED (the spectral width of this hologram is apparently very narrow and requires a similarly narrow source). Lasers need more current than LEDs and therefore have a shorter battery life.

Bruce
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  #6  
Old 11-05-2007, 4:10 PM
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Quote:
Originally Posted by bruce_ventura View Post
I disagree with stator in this. I've got the EOTech patent (US 6,490,060) in front of me. It shows all the components in detail, and clearly describes and illustrates the use of a hologram (#22) to bend the direction of the laser beam toward the viewer. Only a diffractive optic can do this. The optical design also uses a holographic grating (#20) elsewhere to compensate for dispersion cause by the hologram.

The hologram is the reason EOTech was forced to use laser source instead of an LED (the spectral width of this hologram is apparently very narrow and requires a similarly narrow source). Lasers need more current than LEDs and therefore have a shorter battery life.

Bruce
They really do not use a laser as the voltage and power requirements would be impractical. A VCSEL, which is what EOTech uses is a diode and not a laser. It is just that it has some laser properties. It is very cheap to manufacture now and many VCSEL have low power requirements. EOTech is probably is older VCSEL devices to keep costs down.

On to your point, however, I believe that the end result, being a 2 dimensional projection, is not a hologram, and therefore the device is not holographic. Otherwise, some of the video projectors can claim the same.

Finally, I should state that the reason why EOTech uses a VCSEL and not a regular LED is the sharpness they need of the light to project through the mask and onto the display.
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Last edited by stator; 11-05-2007 at 4:20 PM..
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  #7  
Old 11-06-2007, 7:47 PM
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Quote:
Originally Posted by stator View Post
They really do not use a laser as the voltage and power requirements would be impractical. A VCSEL, which is what EOTech uses is a diode and not a laser. It is just that it has some laser properties. It is very cheap to manufacture now and many VCSEL have low power requirements. EOTech is probably is older VCSEL devices to keep costs down.

On to your point, however, I believe that the end result, being a 2 dimensional projection, is not a hologram, and therefore the device is not holographic. Otherwise, some of the video projectors can claim the same.

Finally, I should state that the reason why EOTech uses a VCSEL and not a regular LED is the sharpness they need of the light to project through the mask and onto the display.
OK, I get it. You're pulling my leg, right? Haha.

Just for the record. A VCSEL is a diode laser. It differs from a conventional diode laser in that the cavity is vertical not parallel to the substrate. The EOTech uses a holographically recorded grating (i.e., a hologram).

Bruce
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  #8  
Old 11-07-2007, 7:24 AM
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Wow, you guys are no joke!

lol

I love my Eotech and my Aimpoint. I honestly can't decide which I like better.
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  #9  
Old 11-07-2007, 7:29 AM
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I think different situations call for different tools. I believe the Eotech is the better optic when comparing to the aimpoint. The reticle just works better in close/long range use. That being said my M14 wears an aimpoint. With my scout rail setup I would not be able to co-witness with an eotech.
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  #10  
Old 11-13-2007, 4:00 PM
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I'm an EOTech fan although if I had to go into war, I might lean towards an Aimpoint.

The EOTech reticle is MUCH better IMO as the 65MOA ring allows very fast target acquisition and the 1MOA center dot works great for distance work.

Aimpoints are getting better int he accuracy dept (I think they have a 2MOA dot now) but that sacrifices CQB speed IMO (harder to find a small dot).

However, they are extremely rugged (I watched an Aimpoint rep let a couple guys throw one as far as they could downrange into gravel, retrieve it, and it kept working and held zero) and the battery life is outstanding.

In a perfect world, try both and buy whichever one you like better.
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  #11  
Old 11-19-2007, 7:55 PM
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I have both and I like both of them..... Batteries will last a lot longer in the Aimpoint. I guess it boils down to what you like.
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  #12  
Old 11-19-2007, 11:15 PM
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i've used EOtech, Aimpoint, and Trijicon Reflex. I ended up purchasing the Trijicon Reflex red dot. holo's are great, but i like the plain old red dot!!!

can't go wrong with Trijicon. They are expensive.
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  #13  
Old 11-19-2007, 11:19 PM
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Just to throw an additional condition in here: which holographic and red-dot optics are paralax-free?
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  #14  
Old 11-20-2007, 6:04 PM
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Eotech and Bushnell claim their holosights are 100% parallax free.

Here's a site that discusses parallax with red dot sites:
http://www.bullseyepistol.com/dotsight.htm

Excerpt from bullseyepistol.com:
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The most popular misconception about dot sights is that some are blessed with complete freedom from parallax. Nonsense! Parallax exists in all dot sights because of the nature of the sight design itself. While it is true that all sights do adjust for parallax at particular distances, they become more vulnerable to the problem at other distances.

What exactly is parallax? Parallax is the "error" that occurs when one of two vectors that are parallel is used as a reference for the other. This is a factor with a dot sight because its reflecting lens is optimized for reflecting the image of the LED right down the center of the tube into your eye. If the pistol is held incorrectly and the shooter views the dot near the edge of the tube, it will not actually be pointed at the actual correct point of aim. In an attempt to correct for this, the reflecting lens is concave. Unfortunately this design is only somewhat effective.
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  #15  
Old 11-21-2007, 3:33 PM
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Quote:
Originally Posted by MedSpec65 View Post
Just to throw an additional condition in here: which holographic and red-dot optics are paralax-free?
Aimpoints and EOTechs (and other so-called "reflex" sights) are parallax-free and have infinite eye relief. I haven't tried to take long-distance shots while sighting from the extreme edges of my EOTech but so far, point of aim has equalled point of impact (at my zero'd distance). I believe EOTech avoids this (whether on purpose or by accident) by causing the dot to fade as you get to the extreme edge of the glass.
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  #16  
Old 11-22-2007, 9:27 AM
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Here in Iraq, the Aimpoint wins the popularity contest.

The EOtech reticle is just too big and busy. It's a LOT easier and quicker to drop a dot on a guy, than trying to see him past all that circle and slash....especially with NVG's.

While writing this, I noticed my Aimpoint was still on from two weeks ago (firefight outside AL Kut). No whoop, just turned it off. With a 50,000 hour running battery life, I'm not too worried about it.
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