Would someone please explain these terms: I see them a lot, but don't really fully understand.
broadband, narrowband, red shift, blue shift
definition of broadband, narrowband, red shift, blue shift
Re: definition of broadband, narrowband, red shift, blue shift
In any source of light, there are a number of colours, the range of wavelengths. So, a source may contain all the wavelengths between 450nm and 630nm, and such a source would look white. It may just contain the wavelengths from 570 to 600, and this will appear orange. The range of wavelengths in the source is the "bandwidth" of the source. If the source contains a large range of wavelengths, it's a "broadband" source, if it contains a small range of wavelengths, it's a "narrowband " source.
In a reflection hologram, when you record a hologram, you're creating a set of planes within the emulsion, like sheets embedded within the emulsion. The separation of these sheets are determined by the laser you use, if you use a HeNe, you'll get a set of planes corresponding to 633nm. However, when you process the hologram, the range of plane separation increases, the emulsion swells (it is a jelly, after all!). You've effectively created a new set of plane separations in the emulsion caused by the swelling.
Now, when you reconstruct a hologram, ie when you look at it under a light, the hologram will "choose" a range of colours determined by the range of plane separations with the emulsion.So, if you shot the hologram with a HeNe (633nm), the hologram will swell causing a range of plane separations corresponding to a range between, say, 640nm to 670nm. The hologram will "choose" all the wavelengths between 640nm and 670nm from your light source, and will appear red. Always assuming your light source contained these wavelengths. Reconstructing such a hologram with a blue led will give you nothing! In the example given, the center wavelength is 655nm, and the 'bandwidth' of the hologram is 30nm (from 640 to 670nm). Such a hologram will appear red
The amount by which you swell it will depend on the development and the material. The more you swell it, the larger is the range of plane separations. The larger the separations, the larger the bandwidth. Your eye sees all colours by taking in all the wavelengths present and mixing them up. Thus, the greater the number of colours in a source, or in a hologram,,the brighter will be the hologram. However, the greater the bandwidth, the more your eye mixes the colours, and the more diluted will be the colour.So, the narrower the bandwidth of your hologram, the sharper is the colour of the image, but the dimmer is the image; the broader the bandwidth, the brighter is the image, but the more the colours are muted.A hologram with a bandwidth of 30nm (as above) is considered pretty narrow for a display hologram, whereas a bandwidth of about 100nm is broadband and so creates a very bright hologram, but a very diluted colour.
Now, in the above example, I shot the hologram at 633, and developed it with a bandwidth from 640 to 670nm - a 30nm bandwidth with a center wavelength of 655nm. This is a red image. Suppose, for whatever reason, I want a green hologram? Then, I need to find a development method to swell not only around the center wavelength of 655nm,I need to swell the hologram so it's center wavelength 540nm, with bandwidth between 520nm and 560nm. Now the hologram has roughly the same bandwidth (40nm), but a different central wavelength. Such a hologram is green. I've 'green shifted' my hologram. I may also find a processing method to shift the central wavelength 540, but have the range from 510 to 570nm, a bandwidth of 60 nm. Now, I've made my hologram green shifted and more broadband.
In a reflection hologram, when you record a hologram, you're creating a set of planes within the emulsion, like sheets embedded within the emulsion. The separation of these sheets are determined by the laser you use, if you use a HeNe, you'll get a set of planes corresponding to 633nm. However, when you process the hologram, the range of plane separation increases, the emulsion swells (it is a jelly, after all!). You've effectively created a new set of plane separations in the emulsion caused by the swelling.
Now, when you reconstruct a hologram, ie when you look at it under a light, the hologram will "choose" a range of colours determined by the range of plane separations with the emulsion.So, if you shot the hologram with a HeNe (633nm), the hologram will swell causing a range of plane separations corresponding to a range between, say, 640nm to 670nm. The hologram will "choose" all the wavelengths between 640nm and 670nm from your light source, and will appear red. Always assuming your light source contained these wavelengths. Reconstructing such a hologram with a blue led will give you nothing! In the example given, the center wavelength is 655nm, and the 'bandwidth' of the hologram is 30nm (from 640 to 670nm). Such a hologram will appear red
The amount by which you swell it will depend on the development and the material. The more you swell it, the larger is the range of plane separations. The larger the separations, the larger the bandwidth. Your eye sees all colours by taking in all the wavelengths present and mixing them up. Thus, the greater the number of colours in a source, or in a hologram,,the brighter will be the hologram. However, the greater the bandwidth, the more your eye mixes the colours, and the more diluted will be the colour.So, the narrower the bandwidth of your hologram, the sharper is the colour of the image, but the dimmer is the image; the broader the bandwidth, the brighter is the image, but the more the colours are muted.A hologram with a bandwidth of 30nm (as above) is considered pretty narrow for a display hologram, whereas a bandwidth of about 100nm is broadband and so creates a very bright hologram, but a very diluted colour.
Now, in the above example, I shot the hologram at 633, and developed it with a bandwidth from 640 to 670nm - a 30nm bandwidth with a center wavelength of 655nm. This is a red image. Suppose, for whatever reason, I want a green hologram? Then, I need to find a development method to swell not only around the center wavelength of 655nm,I need to swell the hologram so it's center wavelength 540nm, with bandwidth between 520nm and 560nm. Now the hologram has roughly the same bandwidth (40nm), but a different central wavelength. Such a hologram is green. I've 'green shifted' my hologram. I may also find a processing method to shift the central wavelength 540, but have the range from 510 to 570nm, a bandwidth of 60 nm. Now, I've made my hologram green shifted and more broadband.