Thank you for your patience. An Edmund Optic's representative will be with you shortly. Credit Card information can not be accepted over Chat. Pau Loong: Thank you for contacting Edmund Optics Technical Support, my name is Pau Loong; how can I help you today? Nathan McCorkle: Hi, I need help finding the right optics for focusing a laser Pau Loong: wavelength, divergence, raw beam diameter? Nathan McCorkle: i desire a small spot size, but a close working distance (7-18 mm) is fine Nathan McCorkle: one moment Nathan McCorkle: its 405nm Pau Loong: raw beam diameter? Nathan McCorkle: i am not sure Nathan McCorkle: i think about 2mm Nathan McCorkle: but maybe 9mm Nathan McCorkle: it is from a bluray 12X writer drive Pau Loong: so you are looking for a single piece of focusing lens? Nathan McCorkle: i saw these http://www.edmundoptics.com/optics/optical-lenses/aspheric-lenses/blue-laser-collimating-aspheric-lenses/3362#products Nathan McCorkle: what is the difference between the two? Pau Loong: ok, for focusing a laser to a small spot size, we have to follow a equation Pau Loong: spot size = wavelength * focal length / diameter * 4/pi Nathan McCorkle: right Nathan McCorkle: which is why I said a close focal length Pau Loong: yes, you need to collimate the laser first, to make the beam parallel Nathan McCorkle: the link i provided earlier, for the blue lenses? Nathan McCorkle: said it was collimating Nathan McCorkle: the assymetric one Nathan McCorkle: (well there were multiple with different NAs) Nathan McCorkle: coated/uncoated Pau Loong: yes, you need to know the divergence of your laser Pau Loong: then estimate the NA = 1 / 2 / f-number Pau Loong: f-number = focal length / diameter Nathan McCorkle: so if i setup my laser, what procedure could I perform to arrive with sufficient data? Nathan McCorkle: i am assuming the raw diode will not have a focus Pau Loong: wavelength, f-number Pau Loong: that determine your final laser spot size Nathan McCorkle: but if it doesn't have a focus, how can it have an f-number? Nathan McCorkle: if its divergent out of the can Pau Loong: your laser is diverging, so it has a f-number Pau Loong: or NA Pau Loong: NA = sin (half angle in degree) Pau Loong: let me show you an illustration Nathan McCorkle: so i would have to measure the spot size at multiple locations away from the exit hole in the diode can Pau Loong: http://www.edmundoptics.com/optics/optical-lenses/aspheric-lenses/precision-molded-aspheric-lenses/2123 Pau Loong: refer the Technical Images Nathan McCorkle: to determine the angle Pau Loong: right Nathan McCorkle: does edmunds sell micrometers and mounts to help me with that? Pau Loong: measure the angle found here: http://www.edmundoptics.com/learning-and-support/technical/learning-center/application-notes/lasers/beam-expanders/?&viewall Pau Loong: please have a sketch/drawing of your intended setup Pau Loong: we can recommend from your sketch Nathan McCorkle: hmm, ok Nathan McCorkle: so once i determine the NA of the laser, and measure the width at the base... what can you recommend? Pau Loong: yes Nathan McCorkle: do I use the NA I determine and match a collimating lens of the same value? Nathan McCorkle: the flat side up against the laser diode? Pau Loong: the flat surface facing the laser Nathan McCorkle: so that would produce a collimated beam, correct? Pau Loong: right Nathan McCorkle: and then I would need another lens to focus it? Nathan McCorkle: what type of lens would that be? Nathan McCorkle: i.e. the first type is an assymetric collimating lens Pau Loong: depending on your Spot Size requirement, you might need to further expand your beam before focusing Nathan McCorkle: i do not believe i need to expand the beam Nathan McCorkle: when i calculated the spot size with the range of possible beam diameters Nathan McCorkle: (I was assuming the beam was collimated) Pau Loong: yes, but pay attention that f-number = focal length / diameter Pau Loong: you can choose a lens with a fixed FL Pau Loong: but how about the diameter? Nathan McCorkle: is the diameter of the second lens based on the diameter of the beam out of the diode can? Pau Loong: it is the Input to the focusing lens Pau Loong: larger diameter gives you smaller spot size for a fixed FL Nathan McCorkle: right, but if i get a 10mm diameter lens with 10mm focal length... will it perform the same as a 20mm diameter len, with a 10mm focal lenght Nathan McCorkle: when i put the same 10mm collimated beam into them? Pau Loong: certainly not Pau Loong: pay attention to the formula of the spot size again Pau Loong: you will have a spot size smaller by double if you double the diameter Nathan McCorkle: i am talking about the diameter of the focusing len Nathan McCorkle: s Nathan McCorkle: not the collimated beam Pau Loong: yes, i am assuming the diameter of the laser input same as diameter of the lens Pau Loong: it is the laser diameter that concern Nathan McCorkle: but if my laser diameter is 1.9mm and you only sell a 2mm diameter lens Nathan McCorkle: then what is the effect? Nathan McCorkle: does the spot size calculation use the lens diameter, or the beam diameter going into the lens (like i say the beam could be 1.9mm into a 2mm lens) Pau Loong: the formula is for the laser diameter Nathan McCorkle: ok so I just need to choose a lens larger than the beam, with the desired focal length? Pau Loong: right Nathan McCorkle: ahh, ok Nathan McCorkle: so i need to match the NA of the laser to equal one of the asymmetric collimating lenses? Pau Loong: it is Aspheric lens, not asymetric lens Nathan McCorkle: i believe this may be correct Nathan McCorkle: the beam divergence angles, of 8.5 degrees on horizontal direction and 19 degrees on vertical direction Nathan McCorkle: ahh right, aspheric Pau Loong: then you need to make your beam circular first Pau Loong: http://www.edmundoptics.com/optics/prisms/specialty-prisms/anamorphic-prism-pairs/2429 Nathan McCorkle: is it a problem to choose the larger divergence angle and use that for the NA calculation? Pau Loong: yes, use the largest one if you plan to use an elliptical beam Nathan McCorkle: hmm Nathan McCorkle: how do i determine when the beam is mostly circular if I use the Anamorphic Prism Pairs Pau Loong: check under the "Specifications" tab Pau Loong: there is different magnifiation for different angle of adjustment Nathan McCorkle: how would I mount the unmounted 405nm version Nathan McCorkle: ? Pau Loong: we don't have an empty mount to offer Nathan McCorkle: ! Nathan McCorkle: so i have to machine something myself? Pau Loong: it depends how you with to hold it Pau Loong: wish Nathan McCorkle: can you give me a link to the focusing lenses you think would be best? Pau Loong: you must first determine the spot size you need Nathan McCorkle: would it be plano convex? Pau Loong: then we can determine the input diameter you need Nathan McCorkle: or again an aspheric? Nathan McCorkle: i need <= 5microns Pau Loong: aspheric gives smaller spot size than PCX Pau Loong: you can calculate the f-number based on the spot size equation Nathan McCorkle: and i buy a lens by the F-number? Pau Loong: f-number or NA, they are the same thing Pau Loong: NA = 1/2/f-number Nathan McCorkle: but for the spot size equation, I thought I just need to buy a lens based on the focal length Pau Loong: spot size = 4/pi * f-number *wavelength Nathan McCorkle: earlier you said "spot size = wavelength * focal length / diameter * 4/pi" Pau Loong: yes, f-number = focal length / diameter Nathan McCorkle: so i know its 405nm, its 2-3mm beam diameter, and I want something 7-17mm focal length to produce <= 5 micron spot size Nathan McCorkle: so can i just choose a lens based on focal length? Pau Loong: you cannot choose diameter and focal length by yourself Pau Loong: it is determine by the formula Nathan McCorkle: earlier you said "Pau Loong: the formula is for the laser diameter" Pau Loong: you need to calculate the focal length you need Nathan McCorkle: why, I have calculated that a range from 7-17mm will produce a spot sufficient for my purposes Pau Loong: ok, if you have calculated, then you can choose the Aspheric lens Nathan McCorkle: link please? Pau Loong: http://www.edmundoptics.com/optics/optical-lenses/aspheric-lenses/precision-molded-aspheric-lenses/2123 Pau Loong: and Pau Loong: http://www.edmundoptics.com/optics/optical-lenses/aspheric-lenses/blue-laser-collimating-aspheric-lenses/3362#products Nathan McCorkle: and do you sell the mounting track, to place items next to each other? Nathan McCorkle: are those "Precision Molded Aspheric Lenses" glass or plastic? Pau Loong: http://www.edmundoptics.com/mechanics/optical-mounts-plates/lens-mounts/ Pau Loong: glass Nathan McCorkle: ok, well I think that's enough info for tonight, I will try to find the information on the laser, and if I can't, I will have to measure it Nathan McCorkle: thanks a lot Pau Loong: If you have any further questions our Technical Support Department is here Sunday 8:00 pm through Friday 6:00 pm EST. Pau Loong: Thank you for contacting Edmund Optics!