Difference between holographic paper and diffraction gratings?

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What is the difference between holographic paper sold in decorative shops and professional diffraction gratings? What about the difference between pearlescent decorative tape and professional dichroic mirrors?
Close-up of a roll of holographic tape showing green, blue and yellow iridescent colour bands with a fine embossed pattern and a silver edge.
Three rolls of iridescent holographic tape on a dark background, labelled Indigo Sunrise, Moonbeam and Orange, each showing shifting rainbow colours and landscape-like reflections.
Close-up of three rolls of black holographic tape with rainbow-coloured vertical streaks reflecting off their glossy surfaces against a white background.
Two rolls of iridescent holographic tape on a white background, showing shifting pink, blue, green and violet colours across their surfaces, with a cardboard core visible at each roll's end.
Close-up of silver holographic tape rolls showing rainbow iridescent color bands in reflection, with multicolored streaks running across the metallic surface.
Several curled strips of iridescent holographic ribbon, showing blue, pink, yellow and green color bands that shift across each strip's surface.
Two rolls of shiny silver holographic tape with rainbow iridescence, and a loose strip of the same tape lying diagonally across a grey surface showing blue, orange and yellow color bands.


These photos show pearlescent tape that changes color when observed from different angles. Either it's the full rainbow like in the third, fifth and seventh images I displayed here or just a few colors like in the other images, they still change color and are called "iridescent decorative tapes". How do they compare to professional diffraction gratings and professional dichroic mirrors which are more expensive? Do they work on the same principles in physics or on different principles?
 
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Yes, all these items rely on the same principle of wave interference when light is scattered (or transmitted) by microstructures. These, like the examples you list are human made, but they also occur naturally. This Wikipedia article mentions all that. The morpho butterfly is my favorite example of structural wave interference (see video below.)

 
with
professional diffraction gratings
you can do actual measurements. With a butterfly that's not so realistic :smile:

##\ ##
 
BvU said:
with you can do actual measurements. With a butterfly that's not so realistic :smile:

##\ ##
One of the teachers at my university thought that diffraction gratings and dichroic mirrors are expensive and that me and him could never afford one. He thought about using a CD for a diffraction grating. Yet I found these in a decorations shop - holographic paper and pearlescent tape. I guess they can replace the professional dichroic mirror and diffraction grating?
One such PVC film does completely block a red laser pointer and " is widely applied in decoration of bags, shoes and clothes".

Photo of a sheet of iridescent blue PVC film curling into a tube, with shifting pink, green and gold sheen across its surface.
 
Is it true that these plastic dichroic films are created by melting plastic (polyester or polyvynil chloride) together with mica flakes coated with thin films of titanium dioxide?
 
James2018 said:
One of the teachers at my university thought that diffraction gratings and dichroic mirrors are expensive and that me and him could never afford one.
When I was in charge of introductory physics lab at my University we had two experiments in "modern physics" in which students used gratings. The first week they used the spectrum of hydrogen to determine the Rydberg constant. The second week they used the measured wavelengths from the previous week in a photoelectric experiment to determine ##h/e.## They got decent results.

The gratings they used were mounted on cardboard slides (I don't remember the spacing). Through Amazon.com you can get these for $2.99 ea., these for $9.90 ea. and these for $43.30 ea.

Edmund Scientific has pricier gratings in the $100-200 range that might not be prohibitively expensive for your teacher and you. The adage "you get what you pay for" is almost always the case but, of course, what you should get is what you need to do the job adequately.
 
kuruman said:
When I was in charge of introductory physics lab at my University we had two experiments in "modern physics" in which students used gratings. The first week they used the spectrum of hydrogen to determine the Rydberg constant. The second week they used the measured wavelengths from the previous week in a photoelectric experiment to determine ##h/e.## They got decent results.

The gratings they used were mounted on cardboard slides (I don't remember the spacing). Through Amazon.com you can get these for $2.99 ea., these for $9.90 ea. and these for $43.30 ea.

Edmund Scientific has pricier gratings in the $100-200 range that might not be prohibitively expensive for your teacher and you. The adage "you get what you pay for" is almost always the case but, of course, what you should get is what you need to do the job adequately.
I observed that dichroic mirrors and their plastic pearlescent tape imitations become like a metallic silver mirror in appearance when irradiated only with the wavelength they reflect. When irradiated with the wavelength they transmit they appear completely transparent like window glass, or at least translucent. So do crystals like moonstone or labradorite which also use thin-film interference in multiple layers. Although labradorite is gray so it does not become transparent under transmitted light.
For example, this is a iridescent Christmas tree star decoration which reflects yellow and transmits blue:
 
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  • Two photos of a star-shaped decoration side by side: on the left it appears yellow and reflective, on the right it appears blue and translucent.
    IMG_20240407_080114.jpg
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Holographic paper from decor stores is usually a simple imitation of the holographic effect and does not have true holographic properties like professional diffraction gratings. Mother-of-pearl decorative tape changes color at different angles due to the interference of light on the surface, while dichroic mirrors have a special coating that transmits or reflects certain colors of light. Although both phenomena are based on the interference of light, they use different principles of physics and have different properties.
 
Two rolls of silver holographic foil tape lying on a grey surface, with a loose strip of the foil running diagonally across the bottom showing rainbow-coloured iridescence.

"The holographic effects are created by metalizing the surface with a thin layer of shiny silver aluminum. The holographic patterns are embossed into the aluminum surface, which forms millions of pixels in microscopic grooves and valleys. This embossed surface diffracts the light into many colors and reflects the light."

Source:
https://www.novavisioninc.com/pages/learn_more_holographic_paper.html
Diagram titled How Interference Color Pigments Work showing three panels of white light hitting mica layers coated with TiO2 and reflecting as white, yellow and green, with transmitted light shown as white, blue and red.

Interference Pearls are made by mica coated with titanium dioxide. When you look at them straight on they appear more whitish. When viewed at an angles you see glorious irridescent colors. The presence of the difference colors is due to the thickness of the titanium dioxide coating. By varying the coatings you get all the wonderful colors of the rainbow.

Important things to know when working with interference pigments. (other tradenames may be "hilites" or,"intervals")

They are very translucent.

The particular color effect is angle dependent.

The Strongest color effect is with a thin application over a dark valued color, such as black.


Source:

https://justpigments.com/collections/interference-mica-powder
 
AlexisBlackwell said:
Holographic paper from decor stores is usually a simple imitation of the holographic effect and does not have true holographic properties like professional diffraction gratings. Mother-of-pearl decorative tape changes color at different angles due to the interference of light on the surface, while dichroic mirrors have a special coating that transmits or reflects certain colors of light. Although both phenomena are based on the interference of light, they use different principles of physics and have different properties.
OK some pearlescent tapes I am using have a thin layer on the surface like soap bubbles that varies in thickness
Six rolls of iridescent holographic tape in purple, rainbow, white, blue, pink and orange, arranged on a dot-grid paper sheet.

but other ones I am using have many layers of interference pigment (mica powder coated with titanium dioxide) inside the plastic matrix so they block yellow light or green light and transmit their complementary colors.

Several rolls of iridescent holographic tape on a wooden surface, showing shifting pink, purple, blue and green reflections across the glossy film.


Can you see the difference?
 
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Grating based holographic images and patterns are widely used in
packaging to catch the eye of the consumer. The characteristic
rainbow-like reflection of light from holographic papers can be
used either by itself or with a print to create interesting
contrasts and optical effects. Holographic patterns are also used
for purposes of authentication to protect products and documents
from counterfeiting.

A grating based holographic paper consists of separate areas of
reflective diffraction gratings, which disperse polychromatic
light into its constituent monochromatic components depending on both illumination and observation angles, and the physical
structure of the grating. Due to the angle-dependent nature of the
holographic patterns, conventional measurement methods for paper products cannot be used"

Source:
"Method for the Characterisation of Grating Based0Holographic Paper", Max Karlsson, Uppsala Universitet
 
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My final guess is that the Chinese manufacturers include these pigments to achieve either 2D holographic or pearlescent effect. I am not sure but they could be mixed with molten plastic with a rotating drum so that they disperse evenly in the molten plastic,which is then extruded into foils or shaped using molds. This is just a guess I am not sure. What do you think?

Two photo pairs of a jar of iridescent pearlescent pigment powder, with a close-up of the powder smeared on a hand showing shifting pink, violet and blue sheen.


Clear plastic jar of iridescent holographic pigment powder with a white label reading "50克", held in a hand, showing rainbow sheen.
Close-up photo of a clear cylindrical jar of iridescent pigment powder shimmering pink, green and blue, with the orange label 96215 printed across the middle.

Grid of sixteen swatches of holographic glitter, each labelled with a size such as 1/4"(6.0MM)0.25 down to 1/700"(0.036mm)0.015, showing particles from large chunky flakes to fine dust.

Five jars of iridescent pearlescent pigment powder, each with a white cap, shown above circular dishes of the same powder, with swatches above them showing color shifts from yellow to pink, blue and green.




Photo of an industrial stainless steel rotating drum machine with a motor on the left side and a sloped metal chute on the right, mounted on a frame.
Diagram of a plastic extrusion line from left to right: a hopper feeding an extruder with a screw inside a barrel, a die, a cooling tank, a pair of pullers, and a removal unit. Labelled Extruder, Die, Cooling, Puller and Removal.
 
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OK, the tapes are iridescent and based on thin film interference. The pearlescent plastic with mica flakes has a more sparkly diffuse reflection like nacre.
Glossy blob-shaped object with a pearly, iridescent finish showing soft pink, blue and white color shifts across its surface, with a small hole near the lower end.
 
Here is what gives iridescent sequins their iridescence. I melted it, seems to be a thin film of transparent plastic.

Before melting, sequins are iridescent
Packaged DIY handmade sequins labelled Pailletten (Sequins), 12 g, priced 1 euro, with a cluster of iridescent star-shaped sequins visible through the clear plastic bag.


After melting, the sequin loses its iridescence and looks like a ball of translucent plastic:
Small whitish lump of melted plastic, roughly irregular in shape, against a dark blurred background.


There is no mica flakes in it coated with titanium dioxide, else it would still be iridescent because these flakes are inorganic and do not melt.

How do you explain this?
 
"
  • Made with PET material, the colour film is made by the superposition of hundreds of layers of polyester film by co-extrusion technology.
"

https://resinsupplies.co.za/product/holographic-iridescent-self-adhesive-sheets-2-pack/

https://plasticfilmchina.en.made-in...idescent-Film-for-Printing-and-Packaging.html

What does it mean co-extrusion? And how can they superpose hundreds of layers of the same material - PET to achieve iridescence? I thought two materials with different refractive indices were needed.
 
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"
Controlling light waves as they pass through or bounce off of hundreds or thousands of layer interfaces is defined by the refractive index of the adjacent polymers. The larger the difference in refractive indices of adjacent polymer layers, the brighter the reflection off their interface. The reflection is also brighter with more layers in the stack.

Decorative films alternate layers of two polymers, typically a polyester like PET with a refractive index of 1.8 and an acrylic like PMMA with a refractive index of 1.5. The reflected-color effect varies as the viewing angle onto the film changes.

Birefringence is caused by the difference in refractive index between polymers at different viewing angles. Birefringent polymer pairs in microlayer films typically leak light when they are tilted and reflect only within a specific range of viewing angles. From all other angles, the interface appears transparent.



3M discovered that different layer thicknesses in a stack could create highly sophisticated patterns of reflections, capable of passing some waves of light through while stopping other wavelengths, and creating structures that reflect equally well from any viewing angle."
https://www.ptonline.com/articles/microlayer-films-new-uses-for-hundreds-of-layers
 
Opalescent and iridescent glitters exhibit effects where colour can only be seen when viewed from a particular angle. This effect is know as a colour travel effect, where the colour observed changes depending upon which angle the glitter is viewed. Opalescent and Iridescent glitters utilise the manipulation of light through refraction and reflection to achieve this effect.

In an iridescent glitter, light is refracted and essentially spun back on itself back. Iridescent glitters are created by micro layering more than one hundred alternate layers of two different type of plastics with complementary refractive indexes. The microlayer film is created by using hi-tech plastic extrusion techniques of the two colourless synthetic plastic polymers. Iridescent glitters are transparent, unlike metallic and holographic which have a reflective aluminium layer and are opaque. Refractive index is the value given relating to a materials’ ability to bend light when light enters it. Refection is the effect seen when light is bent moving from one medium into another, for example from air into water.

These types of plastic glitter do not contain any pigment or aluminium layer and are completely transparent. The intensity of the iridescent effect is increased by using these types of glitters against a dark or black background.
The Structure of Plastic Iridescent Effect Glitter

Diagram of a microlayer film: a stack of more than 100 alternating layers of two synthetic polymers with refractive indexes n1 and n2, with light rays at angle θ partially reflected at each layer boundary, labelled Synthetic Polymer 1 (refractive index y) and Synthetic Polymer 2 (refractive index x), layer spacing d.




Source:
https://www.bioglitter.com/glitter-colour-effects-how-are-they-created/
 
Holographic effect glitters exhibit a spectacular rainbow effect, created by splitting light into its individual component parts. Each glitter particle acts as little prism splitting light. The structure of a holographic glitter is similar to a metallic glitter in that it has a very thin aluminium layer to reflect, with the addition of a microscopic structural pattern to diffract the light.

In non-diffuse direct light, for example, direct sunshine or LED lights, these products really excel, producing an eye-catching kaleidoscope of dazzling colour.

As holographic glitters contain an aluminium layer, like metallic glitters 2500 times thinner than a human hair, they are opaque, diffusing and reflecting the light that hits them.

Close-up of holographic glitter or foil showing a dense speckle of iridescent rainbow colours in blue, green, yellow and orange across a dark background.

Source:

https://www.bioglitter.com/glitter-colour-effects-how-are-they-created/
Diagram of light reflecting off a grating surface: an incident ray at angle a to the normal, with reflected zero-order and higher-order beams (Order -1, 0, 1, 2, 3) fanned out as rainbow spectra.
 
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Iridescent glitter exudes a soft, pearlescent shine, adding a touch of magic to any project. It's revered for its subtle, shimmering quality that emanates a soft, captivating glow. On crafts, it grants a gentle sheen that changes color as light hits it from different angles. This captivating effect is achieved by layering multiple transparent colors over a reflective base.

The process of making iridescent glitter involves depositing thin layers of metallic oxides onto a substrate, often a polyester film. These layers interact with light, causing interference and diffraction that results in the shifting colors. This type of glitter is made using precision coating techniques to ensure consistent layer thickness and optimal color play. The final iridescent glitter product consists of a polyester film coated with metal oxides, typically titanium dioxide or similar materials.


The creation of holographic glitter involves impressing microscopically fine patterns onto a reflective film. These patterns diffract light, splitting it into a spectrum of colors that shift as the viewer's perspective changes. Quality holographic glitter requires precision imprinting techniques to ensure intricate and consistent patterns.

Source: https://www.boujipanda.com/blogs/cr...m-iridescent-holographic-and-metallic-glitter
 
What do you think of my dichroic mirror and diffraction grating?

Diffraction grating 600 lines / mm, PET, 5.90$; dichroic mirror reflects cyan (~490 nm) and transmits red (~644 nm), 4.76 $, K9 glass.

I think the transmitted color is best seen on a white background and the reflected color on a brown background for the dichroic mirror. The dichroic mirror did not have wavelength specifications but I used RGB to wavelength conversion online.
Photo of a white plastic slide mount held in two hands, with a film window showing a bright reflection of a light source and rainbow diffraction spectra across the top edge.
Square dichroic mirror lying on a brown surface, top half reflecting cyan and bottom half showing pink-red transmitted color against a white background.
 
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Suitable for applications with low requirements, certain types of illumination optics, and demonstrations.

Not suitable for a serious device, as the wavefront will experience many wave aberrations and irregularities. Astigmatism will be one of the main issues.
 
Gleb1964 said:
Suitable for applications with low requirements, certain types of illumination optics, and demonstrations.

Not suitable for a serious device, as the wavefront will experience many wave aberrations and irregularities. Astigmatism will be one of the main issues.
This is how the combined pattern looks like for that dichroic filter and diffraction grating looks like in front of a white LED source:

Dark photo of a bright white-red light source with starburst diffraction spikes radiating outward, seen through a diffraction grating, with red and orange lights visible at the left and right edges.
 
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James2018 said:
What does it mean co-extrusion? And how can they superpose hundreds of layers of the same material - PET to achieve iridescence? I thought two materials with different refractive indices were needed.
Two lumps of slightly different plastic then: Fold and stretch, fold and stretch - just like flaky pastry and Damascus Steel swords.I guess.
 
Gleb1964 said:
Suitable for applications with low requirements, certain types of illumination optics, and demonstrations.

Not suitable for a serious device, as the wavefront will experience many wave aberrations and irregularities. Astigmatism will be one of the main issues.
Perhaps, but my 5$ plastic diffraction grating is labeled as "Professional". You can see this in the photo below on the package label:
Photo of a clear plastic bag's white shipping label reading: Professional 50/100/300/600 Line Transmission Grating Diffraction Grating with for Shell Inner Size 0.91x1.38Inches Dura, SKU Code: J0MD9FF10080, Made in China.
 
Ok it's 6.5 dollars not 5 dollars. Perhaps it's because it's available in a stock of 10,000 pcs every month and it's made of a cheap material - PET plastic?
 

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