142laser wrote: ... What you and others said was the longer the HeNe laser the shorter the coherence length. This is only true up to a point as the paper clearly shows...thank God. [/b]I was wrong to say the longer the laser the longer the coherence length. It is just as wrong to say the opposite or nobody could make a hologram with a SP 127 or a MG 928. Both of those lasers are excellent.
The graph in Figure 7 of that paper does not describe what I've seen in practical lasers. According to it, the coherence length of the SP-127 and the SP-125 would be essentially the same at 30cm. That's just not true. According to the graph, coherence length of He-Ne lasers essentially hits the bottom at 30cm with about a 40cm long resonator and stays there. Also not true in my experience.
I had a studio with two 4x8' tables in it. I had an SP-124B with 20mW and a 70cm resonator, and an SP-107 (same as the SP-127) with 35mW and a 90cm resonator. I always used the SP-124B for mastering because the obviously noticeable extra coherence length gave better holograms. Well worth the decrease in available power when using silver halide materials. According to the graph, there should be no difference between the two. There is. But I certainly agree that the lasers you're selling are great for making holograms.