Laser intensity question

[leif26]

Hi, I have a question about watt ratings on 405nm lasers. Am I correct to assume that if I want to project lets say an ILDA test pattern at a given KPPS and beam diameter on projected surface and I want the image to be brighter I would just need a laser with a higher watt rating, is this correct? or is there another parameter?

A related question: If I wanted to double the surface area of the light beam and maintain the same brightness I could just use a laser with double the power?

Thanks!

[-bart-]

405 nm is UV and hardly visible, if you want the projected image to be visible you should choose a surface that has good fluorescent properties.
Beware that some galvo mirrors that are coated for visible light reflect 405nm very poorly.
If you don't have a particular reason to use 405nm, 445 or 465 would be a far better choice.

Spot size on the projected surface also plays a role in the perceived brightness. An image projected with a 5mm beam will appear brighter than an image projected with a 10mm beam, even though the same amount of light is used.

Keep in mind that doubling the diameter of the projected image actually quadruples the area.

[leif26]

Ok, so assuming I'm using the correct mirrors and I want more light projected, I just need a higher watt rating then on the laser I'm using? There is no other parameter for perceived brightness in a given area?

Thanks

[mixedgas]

What your looking into is called Photometry, and it is a complex subject..
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Spotsize, Wavelength, Screen Material Gain, Scan rate, Scan Angle, Viewing History, Viewing Angle to the Screen, Background Light Level, Genetics, and Wattage Matter.
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You can't just say 2x at 2x in all cases. There are too many variables. A real answer to your question requires measurements, assumptions, and calculations that will not fit in one post, and would take three months to master.
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See:

https://en.wikipedia.org/wiki/Luminosity_function for starters.. Which does not take into account the contrast ratio and background illumination, as well as the eye's viewing history.
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The eye has a Logarithmic response in the dark, Astronomers consider the eye as responsive over more then six orders of magnitude, and it's color response changes with the aggregate level of the light around it.
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There is no response to your question that is NOT situation dependent...
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See Also: https://www.ecse.rpi.edu/~schubert/L...le-Chapter.pdf PAGE 276 for a block diagram that starts to explain how local light level changes vision response....
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Steve

[araugh]

Spotsize, Wavelength, Screen Material Gain, Scan rate, Viewing History, Background Light Level, Genetics, and Wattage Matter.
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You can't just say 2x at 2x in all cases.

Amen!

I don't want to be quoted on the Interweb at all saying this, because it could be taken as Gospel for decades when its totally wrong.

Damnit.

[mixedgas]

Araugh, You caught me in Mid Edit,,, Toss in Viewer Age, and Viewing Angle, too...

Steve