Monochrome and Color Denisyuk Holograms from China

[unixboy]

So, to relate the brightness of a full colour hologram to the efficiency of the hologram, the efficiency must be given for each wavelength component in the hologram. However, there is a calculation by John Caulfield (I believe) that states the if you record n holograms on the same medium with the same wavelength, then the efficiency of the final hologram is 1/n^2, where n is the efficiency of just one recording, assuming that all the recordings are independant. Thus, if you shot an H2 with, say, 5 H1s all perfectly exposed and developed, then the final hologram has an efficiency of 1/25th of the hologram if you only used 1 H1. That is, the more holograms you superimpose, with the same wavelength, the faster the final hologram efficiency drops. There are some problems with Caulfield's analysis, but his analysis was made in the 60s, when holograms were not generally bleached. So, the analysis works for unbleached holograms. It breaks down if you bleach the hologram.

I agree with your analysis on the relationship between brightness and the diffraction efficiency of individual wavelengths. My simple word of "1/n^2" is not an accurate description of diffraction efficiency. Because the color hologram uses different wavelengths to record, even if we apply the "1/n^2" theory, the result is not considering the wavelength differences. As the shorter the wavelength, the higher number of Bragg layers recorded in the same thickness of emulsion. Also, the shorter the wavelength, the ratio of AgX crystal size over wavelength increases. So the actual relationship is very complicated. I was just using a "qualitative" equation to mention a "quantitative" phenomena.

Even if the single wavelength diffraction efficiency of multiple-exposure or color holograms is lower than the diffraction efficiency of the single-exposure monochromatic holograms, it can be reached to high enough (theoretically to 100%) as long as the thickness of the emulsion, index modulation, and the low absorption of final processed emulsion are satisfied.

The colour saturation is the proportion of a primary colour to the overall colour (S = Chroma/Lightness*). Therefore, I would think that the colour saturation would depend on the bandwidth of each component as a ration of the sum of the bandwidths of all the components. That is, by the Fourier coefficiant of one of the primaries to the sum of all the components. I don't think this has anything to do with the crystal size, assuming that te crystal size is small enough to record the appropriate spatial frequencies for the different wavelength components. If the crystal are too large to record the spatial frequencies, on average, then there will be no recording at all.

Let me describe in more detail about my stating of color saturation and AgX crystal size. For single-exposure monochromatic hologram, if it is processed in AgX solvent developer, the size of filament silver is significant large compared to the size of original AgX crystals. When those large size silver filament is bleached to AgX, the newly formed AgX will deposit to the AgX crystals in the unexposed zone of the emulsion. Thus, the micro structure of Bragg layer is slightly changed ( i.e. the sharpness of the Bragg layer is changed or the Bragg layer thickness is changed slightly). This is the main reason of increased spectrum width of reconstructed images. Increased spectrum width leads to lower color saturation.

Russian emulsion usually apply the semi-physical developing which generates the colloidal silver. The size of individual colloidal silver speck is very small but the colloidal silver "cloud" is in huge size (depending on the processing time). What I found is the semi-physical developing results in strong color blurring.

By the way, Danny brought one of your holograms to PCGG4. It was pretty good. Danny compared your hologram to my full colour holograms and the opinion was that the brightness was about the same (Danny's conclusion, not mine!). Mine were made on Colourholographics pan material, which he (unfortunately) no longer makes. I'm finding it very difficult to use PFG-03C. Danny has left me with some dye, so I'm going to try the experiment he suggests, put the dye into a fine-grain Slavich material and shoot full colour.

Thanks. I am now far from US and don't know what is PCGG4. I googled PCGG4 but don't get a meaning one. Could you send me a private message telling me your name? I saw your posts in this forum and previous one for a decade but sill don't know who you are. Thanks.

[Martin]

Russian emulsion usually apply the semi-physical developing which generates the colloidal silver. The size of individual colloidal silver speck is very small but the colloidal silver "cloud" is in huge size (depending on the processing time). What I found is the semi-physical developing results in strong color blurring.

I assume it's the diversity of the grain size (from extremely small to relatively large particles) that leads to broadband (or what you called "color blurring") replay.

[unixboy]

I assume it's the diversity of the grain size (from extremely small to relatively large particles) that leads to broadband (or what you called "color blurring") replay.

Yes, what I mean is just as I mentioned in earlier post: "Colloidal silver or different size distribution of AgX crystals will give broader spectrum width and thus it greatly decreases the color saturation."

[Dinesh]

Let me describe in more detail about my stating of color saturation and AgX crystal size. For single-exposure monochromatic hologram, if it is processed in AgX solvent developer, the size of filament silver is significant large compared to the size of original AgX crystals. When those large size silver filament is bleached to AgX, the newly formed AgX will deposit to the AgX crystals in the unexposed zone of the emulsion. Thus, the micro structure of Bragg layer is slightly changed ( i.e. the sharpness of the Bragg layer is changed or the Bragg layer thickness is changed slightly). This is the main reason of increased spectrum width of reconstructed images. Increased spectrum width leads to lower color saturation.

So, you're assuming that the "sharpness of the Bragg layer" will lead to higher colour saturation? I'm not sure why that would be so.

Color saturation is defined in terms of the eye response system, and is based on concepts of Chroma and Lightness. Saturation is basically a parameter of the HSV system, but the CIE does not formally recognise this. As far as human color perception is involved, saturation is defined as,

S = C/(C^2 + L^2)^(0.5)

Where C and L are chroma and lightness. In terms of holography, both chroma and lightness would depend on the range of spatial frequencies present in the hologram and on the reconstruction source. Assuming that the color temperature of the source matched the frequency distribution of the Bragg planes, then the only factor is the statistical frequency distribution of the planes. Thus, the saturation would also depend on the distribution. However, saturation is just one component of the full scene in a colour hologram. For example, if you had a bright, very red object in the scene, surrounded by muted colours such as pink and brown, then the red object would be highly saturated. This is the result of the fact that the ratio of "red" frequency to the total sum of all the frequencies is high. If the hologram were monochromatic, then the saturation would be a function of the bandwidth of the hologram, which would, in turn, depend on the additional frequencies introduced by the processing scheme. For example, display holograms shot on photopolymers, which are dry processed, would have a high saturation for a monochromatic recording.

If the Bragg planes were 'sharpened", by which I assume you mean that the sinusoidal profile has become more of a square wave profile, then additional frequencies would be introduced because the 'squaring off' of the plane structure would introduce Fourier components, each of which would also diffract. The amount of diffraction from these Fourier component planes would depend on the amplitude of the Fourier component. Since the structure is still periodic, the new Fourier components' frequency would each be doubled from the fundamental, so the diffraction, and hence the 'color' of the new planes would be shifted into the UV. For example, let's say you were recording at 633. Ideally, the fringes/planes would be sinusoidal, with a frequency f = 2/633 (nm)^(-1). Let's say for whatever reason (processing, grain growth etc), the fringes/planes became square wave. Now you introduce new frequencies with frequencies of 3/633, 5/633 etc. each with amplitude 4/(pi*n) for odd n ( Here's the series from Wolfram's mathworld: http://mathworld.wolfram.com/FourierSer ... eWave.html ). The second harmonic would diffract at lambda = 633/3 = 211 nm, ie in the UV region.

Thus grain growth, for example, does not affect bandwidth, since bandwidth is dependent on the statistical frequency distribution of the planes, but it does affect the efficiency (or brightness, which is not the same as efficiency) because it takes some energy away from the fundamental frequency, ie the recording frequency, and transfers it to second, third and even higher orders.

[unixboy]

I checked the private message but find none and still don't know what the PCGG4 is and your real name.

If the Bragg planes were 'sharpened", by which I assume you mean that the sinusoidal profile has become more of a square wave profile, then additional frequencies would be introduced because the 'squaring off' of the plane structure would introduce Fourier components, each of which would also diffract. The amount of diffraction from these Fourier component planes would depend on the amplitude of the Fourier component. Since the structure is still periodic, the new Fourier components' frequency would each be doubled from the fundamental, so the diffraction, and hence the 'color' of the new planes would be shifted into the UV. For example, let's say you were recording at 633. Ideally, the fringes/planes would be sinusoidal, with a frequency f = 2/633 (nm)^(-1). Let's say for whatever reason (processing, grain growth etc), the fringes/planes became square wave. Now you introduce new frequencies with frequencies of 3/633, 5/633 etc. each with amplitude 4/(pi*n) for odd n ( Here's the series from Wolfram's mathworld: http://mathworld.wolfram.com/FourierSer ... eWave.html ). The second harmonic would diffract at lambda = 633/3 = 211 nm, ie in the UV region.

I am not writing an optical paper here. So to make it simple, I want to use easy words and not math to describe it.
How do you assume that I mean square wave rather than sinusoidal wave by just using the word "sharpness"? Here I mean that the chemically processed Bragg layers in AgX emulsion are slightly different from the actual Bragg layers. Maybe the word "contrast" is a better one. Dry processed photopolymers do not introduce any modifications of the Bragg layers and thus have high color saturation.

Thus grain growth, for example, does not affect bandwidth, since bandwidth is dependent on the statistical frequency distribution of the planes, but it does affect the efficiency (or brightness, which is not the same as efficiency) because it takes some energy away from the fundamental frequency, ie the recording frequency, and transfers it to second, third and even higher orders.

If high order harmonic generation is so easy to achieve, than everyone here can double or triple the frequencies of the lasers in hands. We have 1550nm, 1064nm, 808nm, 760nm, 650nm, 532nm, 450nm, 405nm and we can easily divide those by 2, 3, or 4 to obtain desired laser wavelengths. Life is so easy, right?

[Dinesh]

If high order harmonic generation is so easy to achieve, than everyone here can double or triple the frequencies of the lasers in hands. We have 1550nm, 1064nm, 808nm, 760nm, 650nm, 532nm, 450nm, 405nm and we can easily divide those by 2, 3, or 4 to obtain desired laser wavelengths.

The hologram does not generate a frequency doubled out. But it diffracts a frequency doubled reconstruction beam. So, if illuminated by a laser of frequency nu, it does not generate an output of 2nu. But, since a non-linear plane structure contains higher modes that diffracts higher orders, you can make a HOE that diffracts a frequency doubled wavelength. In 1987 I shot a reflective HOE with 488, processed it to deliberately create non-linear planes. I then put it in a spectrophotometer. There was a peak of about OD 3 at about 500 nm and another peak of about OD 1 at 250 nm. However, you have to illuminate it with a wavelength of 250 nm in order to diffract 250nm. Illuminating the HOE with a 500 nm beam would not generate a 250 nm beam.

I checked the private message but find none and still don't know what the PCGG4 is

PCGG4 was a collection of holographers that spent the weekend talking about holography and making holograms. It's a tradition of sorts that got started about 10 years ago with amateur and hobbyist holographers. We did not do a PCGG for a number of years. Danny suggested we do another one and I hosted it. You can see some pictures of the event in the "General" section of the forum: http://holoforum.org/forum/viewtopic.php?f=5&t=861

and your real name.

Dinesh!

[unixboy]

PCGG4 was a collection of holographers that spent the weekend talking about holography and making holograms. It's a tradition of sorts that got started about 10 years ago with amateur and hobbyist holographers. We did not do a PCGG for a number of years. Danny suggested we do another one and I hosted it. You can see some pictures of the event in the "General" section of the forum: http://holoforum.org/forum/viewtopic.php?f=5&t=861

Thanks for telling me PCGG4 and the link in this forum. I get your PM now. I was wondering why Danny's friend use the word "colour" rather than "color" and now it is clear. I visited your websites and they are very good and helpful. I downloaded all the PDFs of your publications and will carefully read and learn. Thanks a lot.

[Martin]

I assume it's the diversity of the grain size (from extremely small to relatively large particles) that leads to broadband (or what you called "color blurring") replay.

Yes, what I mean is just as I mentioned in earlier post: "Colloidal silver or different size distribution of AgX crystals will give broader spectrum width and thus it greatly decreases the color saturation."

Ah, OK, now I see, thanks.

Dry processed photopolymers do not introduce any modifications of the Bragg layers and thus have high color saturation.

That seems to depend also on the specific photopolymer system and layer thickness. While it may be easy to get the same replay wavelength as during the recording, making it sufficiently broadband, is not quite trivial. As you know for display use and in order to achieve a "bright" image, you'll definitely need some bandwidth (say, 30nm). You can make a photopolymer, giving you 100% DE, but if the bandwidth of the hologram is narrow the image will still look "dim" when illuminated with an extended white light source.

[unixboy]

That seems to depend also on the specific photopolymer system and layer thickness. While it may be easy to get the same replay wavelength as during the recording, making it sufficiently broadband, is not quite trivial. As you know for display use and in order to achieve a "bright" image, you'll definitely need some bandwidth (say, 30nm). You can make a photopolymer, giving you 100% DE, but if the bandwidth of the hologram is narrow the image will still look "dim" when illuminated with an extended white light source.

Yes, there is a balance between the color saturation and the visual brightness (or the bandwidth).

Let's daydream a little bit for fun. We could have a theoretical ideal holographic recording medium, which is panchromatic sensitive and has zero absorption in whole visible spectrum and we have a tunable wavelength (400nm-760nm) SLM laser. We make 180 layers of such emulsion, which is 10 micron thickness per layer and we make (760-400)/2=180 laser exposures (2nm step of laser wavelengths), then we stack them all together, the total thickness is 10micron * 180=1800 micron=1.8 mm. Such 1.8mm thick multi-layer-multi-wavelength hologram should give us: high brightness and high color saturation as the real objects. That's the real virtual reality.

[unixboy]

Hello, I am now selling 4inches x 5inches red sensitive holographic plates directly via the forum. My color and monochromatic holograms were made from exactly my plates I am selling now. Please send me the private message for your address and mailing information if interested. Paypal is preferred.

From Sep 18 to Oct 18, 2014, if you buy 20 or more pieces of 4in X 5in holographic plates, I will send you a piece of 4inX5in color reflection hologram (Name: "Friendship", 3 figures of ancient Chinese generals, see the picture in early posts of this thread) for free as a gift. You can use the plates to make beautiful reflection holograms as the same brightness (diffraction efficiency) as the hologram you received. Quality guaranteed.

Holography is like photography, as your skills are proportional to the numbers of holograms (photos) your make (take). I had been using Slavich and Fuji holographic film before deciding to make my own plates. The only reason I don't make film is because I like the simplicity and solidity of plates.The advantages of holographic plates over films are rigidness, ease of use and short waiting time before exposure. Moreover, films need further protection and flattening while plates are self-protected and self-supported.

Prices:
20 pieces US$ 140.00 (US$ 7/piece)
10 Pieces US$ 80.00 (US$ 8/piece)
5 Pieces US$ 45.00 (US$ 9/piece)

Plate size: 4in x 5in (10.2mm X 12.7 mm)
Plate material: high grade flat glass
Thickness of plate: 2mm
Photosensitive material on the plate: silver halide (AgX) gelatin emulsion
Thickness of the AgX emulsion on the plate: about 10 micron
Peak of spectral sensitivity: 633nm (red)
Resolution: >5000 lines/mm
Best exposure for Reflection hologram at 633nm: 660 uJ/cm^2 (micro Joul per square centimeter), when laser intensity is about 100-150 uW/cm^2, higher exposure is needed if the laser intensity is below 80 uW/cm^2 (Law of reciprocal failure)
Best exposure for Reflection hologram at 532nm: 5800 uJ/cm^2 (micro Joul per square centimeter), when laser intensity is about 400-600 uW/cm^2, higher exposure is needed if the laser intensity is below 350 uW/cm^2 (Law of reciprocal failure)
Recommendation for best exposure: depending on your laser intensity (could be as high as mW/cm^2 or as low as several uW/cm^2), get the exposure amount to get OD (optical density or absorption of developed plate) about 3 to 3.5 for reflection holograms. You will need an optical density meter or use the laser light meter to calculate OD=log(10, (input intensity/output intensity))
Maximum diffraction efficiency (633nm): about 80% (measured through monochromatic reflection holographic mirror)
Maximum diffraction efficiency (532nm): about 75% (measured through monochromatic reflection holographic mirror)
Shelf life: 12 months at room temperatures or 2-3 years at 4 degree celsius, do NOT freeze!
Mass of plate per piece: 65 grams

Shipping cost is shown on China Post http://zf.chinapost.com.cn/gj/zfQuery.d ... jBgzfQuery (in Chinese, you might want to use google translate to see it) as international parcel, it depends on weight and your location.

The item price and the shipping cost do NOT include any duty or tax, which if applied must be paid by the buyer.

Shipping to the US is for standard speed (usually 10-15 business days but could be 20 business days in severe weather conditions).
International shipping (non US) is for standard speed, usually 7-25 business days depending on the distance of the destination country and the speed of your local postal service.

Item will be shipped within 2 days as payment is received.

Due to the photosensitive nature of the product, no returns accepted. I will try my best to keep this product safe during transportation and in customs by well packaging and labeling the nature of holographic plates. However, I would not be responsible for exposure of holographic plates if the package needs or has to be opened by customs in your country.

Keep in mind that plates are to be opened in dark room or under green safe light!

A much more detailed user instruction about this product, processing formulas, and suggestions on how to make bright holograms (monochromatic or color) is included!

BTW, my plates had been sent to east Europe and Russia. The buyers were happy after tests of several months.