Page 134 - Blog Posts v1

However, green and blue inks reacted best with the red 755nm wavelength, followed by the green 532nm line then the 1064nm wavelength.
Unfortunately, this study did not investigate the minimum fluences required to induce a reaction. But, their results do shine a light (pun fully intended!!) at the relative absorptions of these coloured inks to those wavelengths – I have shown this in the graph below:
% absorption
100
90
80
70
60
50
40
30
20
10
0
Nd:YAG 1064nm
Black
Alex 755nm Red Yellow Green
Nd:YAG 532nm
Blue
The absorption values above are my own guesstimations, based on the Choi data. They will not be exactly right, but they do give us an indication.
So, if we assume that the minimum fluence needed to induce the desired reaction in black in, with a 1064nm wavelength, is 2 J/cm2, then, it is clear that higher fluences must be applied to the other colours, to achieve the same result.
From the above graph, it appears that red ink may require about 40% more fluence, to match the reaction in black ink; while yellow will require more than four times the fluence needed for black ink – greater than 8 J/cm2.
The same argument can be applied to the 755nm and 532nm wavelengths. In other words, we can use any wavelength to treat any ink colour, as long as the required fluence is applied for that ink’s colour and depth.
This may appear counter-intuitive since many people believe that some colours can only be removed by certain wavelengths – this is incorrect!! The physics is very simple – ink colours with lower absorptions merely require higher fluences.
Ah but.... There is a problem...
Mike’s Blog Posts 134