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G7 lens, What is it?

steve001

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I was reading an old group buy for this lens, but I did not see any info on the lens in question except a comparison of how they perform when laser light passes through them. What I'd like to know is these parameters:

1 AR coated? And for which wavelength(s)?

2. Lens type?

3 Focal length?

4 Diameter in millimeters?

Thanks
 



ElectricPlasma

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I was reading an old group buy for this lens, but I did not see any info on the lens in question except a comparison of how they perform when laser light passes through them. What I'd like to know is these parameters:

1 AR coated? And for which wavelength(s)?

2. Lens type?

3 Focal length?

4 Diameter in millimeters?

Thanks
Q: AR coated? And for which wavelength(s)?
A: Coated for 400nm~550nm

Q: Lens type?
A: ??? Focus lens, ~2.5mm thickness

Q: Focal length?
A. Closest: 8mm

Q: Diameter in millimeters?
A. 7mm w/o holder

The G7 is a compromise between the 3E and G2, with better power than the 3E and better divergence than the G2.
 

steve001

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Q: AR coated? And for which wavelength(s)?
A: Coated for 400nm~550nm

Q: Lens type?
A: ??? Focus lens, ~2.5mm thickness

Q: Focal length?
A. Closest: 8mm

Q: Diameter in millimeters?
A. 7mm w/o holder

The G7 is a compromise between the 3E and G2, with better power than the 3E and better divergence than the G2.
Is it a plano-convex or a double convex?
I suspected the lens had a short focal length. It seems most battery operated laser do.
 

RedCowboy

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The G7 is a single element with a longer focal length designed to bridge the gap between the 3 element and the single element short focal length G2.

The G2 has a 2.39mm rear FL and is the most efficient but also produces the widest spot at distance. Note: The DTR G2 is the real one, all the rest fall short and are not as good so far as I have tested, but podo's is my second favorite, but new copies are coming out all the time yet none seem to get as close and close is desired for cutting and pre shaping optics as well as clean. DTR's G2 is by far the cleanest output. But new stuff is coming out all the time. Again it depends on your task, but DTR's G2 is the highest quality and it shows.

The 3 element makes a tighter spot at distance, less than 1/2 the width of the G2 but loses 30% of the diodes power, some in edge clipping and some parasitic.

The G7 is a single element with a longer FL that makes a spot width similar to the 3 element with less waste. There is more than 1 variation of lens holder. Below are pics of 2 G7's in different lens holders.

This explanation could be a lot longer but that's the basics, search and read about it. There are pros and cons to all, it depends on what you want to do.


 
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steve001

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The G7 is a single element with a longer focal length designed to bridge the gap between the 3 element and the single element short focal length G2.

The G2 has a 2.39mm rear FL and is the most efficient but also produces the widest spot at distance. Note: The DTR G2 is the real one, all the rest fall short and are not as good so far as I have tested, but podo's is my second favorite, but new copies are coming out all the time yet none seem to get as close and close is desired for cutting and pre shaping optics as well as clean. DTR's G2 is by far the cleanest output. But new stuff is coming out all the time. Again it depends on your task, but DTR's G2 is the highest quality and it shows.

The 3 element makes a tighter spot at distance, less than 1/2 the width of the G2 but loses 30% of the diodes power, some in edge clipping and some parasitic.

The G7 is a single element with a longer FL that makes a spot width similar to the 3 element with less waste. There is more than 1 variation of lens holder. Below are pics of 2 G7's in different lens holders.

This explanation could be a lot longer but that's the basics, search and read about it. There are pros and cons to all, it depends on what you want to do.


Thanks. My interest is low beam divergence. So what this lens is is an AR coated short focal length small diameter pcx lens. From that I would say a common easily found lens. I wonder if a wider diameter, longer focal length pcx lens could replace the stock lens in a Challenger 2 series Sanwu laser with an correctly threaded lens mount? The mount would have to be wide enough too accommodate the lens. Like I said, I'm interested in low divergence.
 
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RedCowboy

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The back "input" side of the lenses have a concave shape while the front "output" is convex, a flat back lens makes terrible wings with MM diodes.

You can see it a little better, my pics here are terrible, I lost 620 good pics last month, but you can see the concave shape on the input, this is podo's G2.

 
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Sta

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Cowboy, where did you get the G7 lenses in the longer lens holder?
 

RedCowboy

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From Podo at SANWU but they do focus out near the end of the 12mm modules threads. More so with 9mm diodes than 5.6, but the large 9mm diode spring fits and they do work, I like the short holder myself, just have to be careful adjusting while on, or switch off, adjust, then back on.
 

steve001

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The back "input" side of the lenses have a concave shape while the front "output" is convex, a flat back lens makes terrible wings with MM diodes.

You can see it a little better, my pics here are terrible, I lost 620 good pics last month, but you can see the concave shape on the input, this is podo's G2.
]
That's known as a menicus lens. This is the first I've heard of this type lens used alone. Usually such a lens is used in combination closely spaced or cemented to another positive focal length lens.
 
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steve001

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From Podo at SANWU but they do focus out near the end of the 12mm modules threads. More so with 9mm diodes than 5.6, but the large 9mm diode spring fits and they do work, I like the short holder myself, just have to be careful adjusting while on, or switch off, adjust, then back on.
I don't understand this if you are using the word focus correctly because a positive lens used to collimate a laser beam has one position which will create a beam with minimal divergence using that lens. In other words I want an infinite conjugated beam or a beam that looks like this ========== not like this, a finite conjugated beam >>>>.
 
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RedCowboy

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If you want to focus to infinity focus to infinity.
What I meant to convey about the 9mm long G7 lens holder is that it's working range is near the end of the standard 12mm module threads.

Also multi mode diodes have very high divergence on the fast axis, I correct mine with cylindrical pairs to square up the beam, otherwise the best infinity focus you can obtain looks like a Chinese fan.





 
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steve001

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If you want to focus to infinity focus to infinity.
What I meant to convey about the 9mm long G7 lens holder is that it's working range is near the end of the standard 12mm module threads.

Also multi mode diodes have very high divergence on the fast axis, I correct mine with cylindrical pairs to square up the beam, otherwise the best infinity focus you can obtain looks like a Chinese fan.





Gotcha. Edmund Optics sells round cylindrical lenses. I suspect other companies do too. Using that type of cylindrical lens you could get a beam profile that is oval I think do to having greater degrees of freedom orientation
 
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paul1598419

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No. The face of the diodes emitter must be perpendicular to the, not round but, rectangular cylindrical lenses. These do give a square beam profile as the emitter of the multimode diodes give what basically looks like a line when focused through single element or compound lenses.
 

steve001

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No. The face of the diodes emitter must be perpendicular to the, not round but, rectangular cylindrical lenses. These do give a square beam profile as the emitter of the multimode diodes give what basically looks like a line when focused through single element or compound lenses.
You misunderstand I think. A round cylindrical lens performs exactly as a square type and cylindrical lenses don't have to be square in shape. See Edmund Optics for a photo of a round cylindrical lens.
 
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