Optical Making a vein viewer with LED lights

[Hieu]

I'm trying to optimize my vein viewer with LED lights but I'm not sure which factors affect the penetration of the light through the skin. (I'm following this guide https://www.instructables.com/id/How-to-make-an-affordable-Vein-Finder-for-use-d/)
I can say those factors are the angle of the lights, the colour of the skin, swollen areas. Is there anything else I should consider too? And should I use Parallel light beam instead of non-divergence light beam?
The last question I want to ask is about the arrangement of the LED lights. Is it best to arrange them as a circle or a rectangular?

Sorry for my bad English if there is any mistake.

 

[berkeman]

I'm trying to optimize my vein viewer with LED lights but I'm not sure which factors affect the penetration of the light through the skin. (I'm following this guide https://www.instructables.com/id/How-to-make-an-affordable-Vein-Finder-for-use-d/)
I can say those factors are the angle of the lights, the colour of the skin, swollen areas. Is there anything else I should consider too? And should I use Parallel light beam instead of non-divergence light beam?

From the link, it sounds like the choice of the LEDs is the most important thing:

This tool works by using near-infrared wavelength LEDs to illuminate the flesh at the site. The veins will appear as dark bands because they are more absorbent of this spectrum of light than the surrounding tissue.

Are you using the exact LEDs that he specifies?

The last question I want to ask is about the arrangement of the LED lights. Is it best to arrange them as a circle or a rectangular?

In the theme of the project, probably you want to arrange them as he did in his project. However, I wouldn't close off the top of the rectangle with plastic like he did. QUIZ QUESTION -- Why?

BTW, don't expect too much out of this project. The vein viewers that are commercially available use IR light and translate that into visible light that you can see, like this product:

https://sgmh.org/wp-content/uploads/2018/08/accuvein-picture.png

 

[Stephenk53]

Now that it’s been a few days, how is your project going

 

[jim hardy]

Try looking at the illuminated area with your cellphone camera. They see farther into IR spectrum than our human eyes do.