“How do you do that, colour engraving?” Herewith an explanation of how we at Lion Lasers play with light, how we can turn off the light by shining more light on it and why peacocks are just boring grey beasts at dusk.
Colours do something to people. A black-and-white scene in a film is usually a sign of mourning. Lacking bright colours is a sign of drudgery such as a boring office job. Even the mere absence of the colour “green” in the opening scene of Wall-E does something to you. (1)
To understand coloured light, you need to understand light. But what exactly is light?
Light is a particle, but also a wave at the same time. We will make use of the latter property because 2 waves can reinforce each other (graph A below), but also cancel each other out (graph B). Noise-cancelling headphones make good use of this by creating ‘anti-noise’ (chart B), and light can do the same. With 2 precisely tuned lasers, we can ensure that nothing happens, both light waves extinguish each other. The other way round can be the same, then they reinforce each other (2).
The peaks of light wave 1 and 2 coincide at graph A and reinforce each other. In graph B, they counteract and flatten each other.
Coloured light is light of a certain wavelength, just like pitch in sound.
Red has a long wavelength and if you make it shorter and shorter you will encounter orange, yellow, green, blue, indigo and violet successively. The colours of the rainbow.
Now a jump to stainless steel, RVS. Not stainless because, as with aluminium, the outer layer is oxidised. Only it doesn’t oxidise through like you have with iron. Liquid stainless steel very definitely oxidises and that is what we take advantage of with the laser; we liquefy the top 0.0002 to 0.00035 millimetres, allowing it to oxidise. In fact, stainless steel oxide is partially permeable to light.
Light hitting the stainless steel then starts to do something special, part of the light reflects on the oxidation layer (‘1’ in the drawing below) while the other part only reflects on the stainless steel (2 below). The latter part (‘2’ in the drawing below) travels a greater distance than light beam ‘1’. If we do this properly, we can make these 2 light waves come together in such a way that they amplify each other as shown in graph A.
The wavelength of visible light
The wavelength of visible light is between 350 nanometres (violet, 0.00035mm) and 750 nanometres (red, 0.00075mm). With only 400 nanometres of slack for all visible colours (humans can distinguish roughly 10 million of them!), this has to be done with extreme precision otherwise you get a colour shift. (3)(4)
The best thing about this is that the light gets 2x as bright in that colour. So if you shine 2x more light on it, it becomes (2*2=) 4x as bright! A peacock at dusk on the left, in the sun on the right. Tip: set the screen as bright as possible.
(1) Use of colour in films: Watch video
(2) Wave-Particle Duality: Watch video
(3) This way of generating colour is called “structural colouration”: read more
(4) These structured colours are called “iridescent”: read more
Addendum to (2): How light can travel back in time: Double Slit Quantum Eraser experiment Watch video