Holographic Optical Element (HOE) of simple reflection mirror

Starting point for beginners questions.
Din
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Joined: Thu Mar 12, 2015 4:47 pm

Re: Holographic Optical Element (HOE) of simple reflection mirror

Post by Din »

Petr, strictly speaking, you're right. The Bragg orientation would not be 30 degrees. The K vector would depend on the two input waves within the material, and they would be 0 degrees and sin(60)/n. However, when the reconstruction wave is applied at 60 degrees, the input wave also refracts, to an angle of sin(60)/n, hits the Bragg planes correctly according to the Bragg condition. On diffraction, the output wave then refracts again the other way, or, in this case does not because it's normal, as is the other wave being simulated by the R wave,on creation of the Bragg planes. So, in effect, you can model the Bragg planes as if there were no refraction. In fact, Kogelnik starts by explicitly stating that refraction will not be taken into account, for this reason of two refractions. The S wave, for a given R wave, behaves as if there were no refraction because the planes were formed by two waves that simulate the S and R waves, refracting in and out.
Din
Posts: 402
Joined: Thu Mar 12, 2015 4:47 pm

Re: Holographic Optical Element (HOE) of simple reflection mirror

Post by Din »

moonlight wrote: Tue Nov 10, 2020 3:06 pm it looks like it's acting like a lens or mirror with a focal lens so when I move the image away from the film it's very blurry and gradually when I move it towards the film (using same reference beam angel) image quality improve but still blurry not acting like a clear flat mirror reflection, any idea or hints to fix the blurry issue?
The reason it looks like a focusing mirror is because it is a focusing mirror. You're geometry will create hyperboloid surfaces, which are, in effect, focusing mirrors.
moonlight
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Joined: Sat Nov 07, 2020 3:35 pm

Re: Holographic Optical Element (HOE) of simple reflection mirror

Post by moonlight »

Din, if it’s a mirror with a focal length what’s the focal length formula then? Do I have to put my picture within focal length to avoid blurry image? How to increase the focal length of that mirror?
Din
Posts: 402
Joined: Thu Mar 12, 2015 4:47 pm

Re: Holographic Optical Element (HOE) of simple reflection mirror

Post by Din »

Here you can see the formation of hyperbolae from two point sources, from "Optical Information Processing and Holography" by Cathey. The diagram shows a transmission geometry, but it's easy to rotate the photographic emulsion by π/2, either clockwise or anticlockwise, and see that the hyperbolae are constant, relative to space, but rotated, relative to the emulsion. The focal length is given by the simple lens formula 1/|u| + 1/|v| = 1/|f|
hyperbolae.jpg
hyperbolae.jpg (214.45 KiB) Viewed 4236 times
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