Some questions about laser... - Page 1
Forum section: electronics / general

author: ripuzojohi
author_rank: Newbie
timestamp: July 28, 2019, 11:46:10 am
content: Hello mates, I have some questions about laser...1. Since IR can go through skin, so if a IR laser is aiming at someone, he cannot protect himself by closing his eyelid, or even use his hand to cover his eyes?2. How does laser protection glasses work? Do they only block laser and let normal light passthrough?I really cannot find those answers by searching the web, please help...

author: MosherIV
author_rank: Super Contributor
timestamp: July 28, 2019, 01:05:58 pm
content: Hi1. Yes IR penertrates skin but it only goes through to a certain depth.Try shining a torch at through your hand, it lights up your hand and you can see the thiner parts of your hand lit by the torch, the thicker parts completely block the light.So depending on the strength of th IR light, eye lids/hands can protect your retina.2. The definition of laser light is of a single wavelength and all the waves are aligned.Laser safety glasses are for single light wave legnth, they will totally block light at the specific wavelength and partially either side of that wavelength.QuoteReally! I suspect it is easier to just ask than try and wade through 100s of pages and make sense of it

author: Brumby
author_rank: Unknown
timestamp: July 28, 2019, 02:30:31 pm
content: Quote from: ripuzojohi on July 28, 2019, 11:46:10 amLaser light can come in many different colours/frequencies/wavelengths. Protective glasses will be designed for one wavelength. They will not differentiate between light of a given wavelength from a laser or a coloured light globe. If you have glasses meant for protection from the infrared light of a CO2laser, they're going to be pretty useless around a green He-Ne laser.

author: chris_leyson
author_rank: Super Contributor
timestamp: July 28, 2019, 02:53:44 pm
content: See ThorLabs for a typical range of certified laser safety glasses.https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=762

author: duak
author_rank: Super Contributor
timestamp: July 28, 2019, 06:23:13 pm
content: The Maximum Permissible Exposure (MPE) level is decreased for visble lasers because the eye brings visible light to a sharp focus that can damage the retina. The laser safety rules expect the "Aversion Response" to protect the eye. ie., if you see something unexpected or it is uncomfortable and move out of the way, there shouldn't be any damage to the eye. This doesn't mean you should look down the boresight of any laser even if it is Class 1. Note also that you can see some near IR. For example, an 820 nm laser is visible as a dim red light, very much like a glowing ember.Laser safety glasses can have different attenuations for differing wavelengths. ie., they may have an OD of 3 for visible wavelengths and 5 for IR from 800 nm to 1500 nm.

author: james_s
author_rank: Super Contributor
timestamp: July 28, 2019, 10:29:52 pm
content: There is a very wide range of wavelengths that are classified as "IR". Anything from around 700nm all the way up to 10,600 nm of CO2 lasers.Laser safety glasses are in a basic sense just colored filters, they are selected to block a specific wavelength or range of wavelengths while allowing most other light to pass.