Where can I get a cheap x-y mirror scanner? - Page 1
Forum section: electronics / general

author: Ben321
author_rank: Frequent Contributor
timestamp: November 25, 2019, 11:11:39 pm
content: I'm considering building my own single-pixel IR imager. Because it is a single pixel, the sensor itself would be cheap, even for more exotic wavelengths like SWIR (InGaAs photodiode for only $75 exists). Of course, for a single pixel detector to work, I will need a way to scan the field-of-view of that detector. That means I will need an x-y scanning mirror pair, and a driver circuit. From my research, these don't seem to exist as standalone devices. They seem to always to only exist as already installed components in single-pixel IR cameras. I hope I'm wrong though. I just need to know a couple things. Is there a commercially available x-y scanning mirror pair that exists from some company? And what kind of prices are they selling for?

author: james_s
author_rank: Super Contributor
timestamp: November 25, 2019, 11:17:46 pm
content: Closed loop galvos intended for laser light shows are readily available and no longer particularly expensive. I think you will need something different than the standard mirrors to reflect IR though.It could be an interesting project, but it will never touch the performance of even a 30 year old commercially made thermal imager. You might manage to get a recognizable image of something hot against a cool background, like a teapot on a stove.

author: Ben321
author_rank: Frequent Contributor
timestamp: November 25, 2019, 11:28:46 pm
content: Quote from: james_s on November 25, 2019, 11:17:46 pmDepends if they are first-surface or second-surface mirrors. If first-surface the visible light (or LWIR) radiation will reflect off the exposed metal coating of the mirror. If second-surface, the light will pass through the glass or plastic substrate and then reflect, but of course LWIR will be absorbed by that substrate. Are most laser show scanners like this using first or second surface mirrors? First surface mirrors also get best optical reflection (no secondary reflections as it hits the glass substrate, before it hits the reflective coating), but aren't absolutely required for visible light applications.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 26, 2019, 12:21:51 am
content: Used bar code scanners are another option. Usually the fast scanning axis is done with a faceted metal wheel so should be fine for any wavelength. Might need to change the mirror (or silver the existing mirror which is not a terribly difficult process).Another option is just to use a gimbaled platform with model airplane servos. Places like Hobby King have them dirt cheap for use on drones. Frame rates would be frames/minute or frames/hour. This approach also dramatically simplifies the optical design.Be sure you think your approach through carefully. Scanning sensors always perform a difficult trade between frame rate and sensitivity. Faster frame rates mean faster scan rates which mean wider detector bandwidth. And performance is inversely proportional to the square root of the bandwidth for most systems.

author: james_s
author_rank: Super Contributor
timestamp: November 26, 2019, 01:42:10 am
content: Laser equipment invariably uses first surface mirrors. Normally they are aluminized for visible light and gold for far IR such as CO2 lasers. Handheld barcode scanners use a voicecoil driven resonant oscillating mirror, supermarket scanners use a polygon mirror which is aluminized glass, or in some cases a cast frame holding individual mirrors. Laser printers also use a polygon mirror.

author: Vipitis
author_rank: Frequent Contributor
timestamp: November 26, 2019, 01:46:26 am
content: https://www.eevblog.com/forum/thermal-imaging/diy-pinhole-thermal-camera/msg943914/#msg943914Post of interest on building a successful single pixel scanning camera... But as a pinole raster scanner.

author: ebclr
author_rank: Super Contributor
timestamp: November 26, 2019, 02:23:43 am
content: Any source for those galvos ?

author: james_s
author_rank: Super Contributor
timestamp: November 26, 2019, 04:21:56 am
content: Quote from: ebclr on November 26, 2019, 02:23:43 amDid you even look?https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR12.TRC2.A0.H0.Xgalvos.TRS0&_nkw=galvos&_sacat=0

author: Emo
author_rank: Regular Contributor
timestamp: November 26, 2019, 06:59:51 am
content: Just a weird idea, a dlp scanning module from a beamer can be programmed randomly.

author: bap2703
author_rank: Regular Contributor
timestamp: November 26, 2019, 10:47:15 am
content: I guess DLP chips have a glass cover + tiny "pixels" that might diffract LWIR more than just reflect it.I personally have always liked that idea of a totally DIY 3D printed+coils from PCB scanner:https://www.instructables.com/id/Moving-Things-With-Printed-Circuit-Boards/However you'd need to calibrate it yourself.Do you have any idea of the "pixel" frequency you would like to achieve?

author: artag
author_rank: Super Contributor
timestamp: November 26, 2019, 12:39:54 pm
content: There's a nice big spinning metallic scanning mirror in every laser printer. I think it's more likely to be aluminium than gold, but it is at least intended for SWIR rather than visible light.

author: james_s
author_rank: Super Contributor
timestamp: November 26, 2019, 04:47:00 pm
content: It is aluminum, and it's a very high precision part. It's only a few mm wide though which may or may not be an issue. Also there are a lot of "laser class" printers that are actually LED page printers, these do not have a polygon mirror.

author: Ben321
author_rank: Frequent Contributor
timestamp: November 27, 2019, 07:34:47 pm
content: Of all those suggestions on here, I think the XY laser scanner for a laser light show would be best. It already has the mirrors mounted in position. If I used a spinning barcode scanner mirror, that's just good for one axis, and means having 2 such scanners, and worst of all the need for me to construct a physical frame with mounts for these components. I do not own a machine shop. I can't just build physical mounts and frames and chassis for my equipment. If I need to mount a component, it needs to already be mounted. That's why the laser light show XY scanner seems like the best option. Barcode scanner mirrors or laser printer mirrors just won't work for me, because I have no way to build mounts to hold and align these components.

author: artag
author_rank: Super Contributor
timestamp: November 27, 2019, 08:20:07 pm
content: @james_sYes, it does need to be an actual laser printer. Fortunately that's many of the older dumped ones you're likely to find !@Ben321If light show scanners are fast enough and cheap enough then yes, they're certainly much more flexible. However the spinning mirror is perfect for raster scanning : it just needs a slow framerate tilt to do the other axis. You need pretty good scanner mirrors to reach the raster rate of a spinning mirror. However, the scanner mirrors will be smaller : the size of the second mirror depends on its distance from the first mirror, and that can be much smaller for galvos than mirror drums.The cheaper sets of scanner mirrors will usually be provided as separate devices, especially if you buy them individually rather than as a set with laser diodes etc. But maybe you can find an old scanner with broken lasers that would give you the mounting hardware too.

author: james_s
author_rank: Super Contributor
timestamp: November 27, 2019, 08:22:19 pm
content: If you want to do things on the cheap you need to open your mind a bit and be creative, you do not need a fully equipped machine shop to fabricate mounts, you can make that sort of thing with little more than a hacksaw, file, bench vice and a power drill. All sorts of metal stock is available, you can get extruded right angle aluminum and all sorts of other stuff.If you wanted to get a raster image using a polygon mirror, the typical approach is to use the polygon for the horizontal axis and then use a galvo for the vertical axis. For what you're trying to do the speed advantage likely wouldn't matter much so you could try a set of galvos to do both axis.

author: bap2703
author_rank: Regular Contributor
timestamp: November 28, 2019, 04:36:59 pm
content: Another solution is to move the detector on a XY stage, imaging trough a pinhole.Due to 3D printers I am sure you can get that really cheap.But if you don't know your detector's bandwidth it's quite hard to figure out the requirements of your scanner.

author: Ben321
author_rank: Frequent Contributor
timestamp: November 28, 2019, 10:19:01 pm
content: Quote from: bap2703 on November 28, 2019, 04:36:59 pmYes, I could 3d print a mount for the optics, but to move it you would still need that xy stage you mentioned. I don't know of any company that makes one other than Edmund Optics. And these cost thousands of dollars. The controllers for these stages are separate units, and cost hundreds of dollars.Any money I'd save by manually building such a camera, would end up being spent on the parts. So in the end, I'd not be saving any money.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: November 29, 2019, 02:55:30 am
content: Quote from: Ben321 on November 28, 2019, 10:19:01 pmI am sure that he meant to mount the detector on the x-y stage of a cheap 3-D printer. So you have your stage for under $300 and write g-code to define your scan pattern.

author: Uho
author_rank: Frequent Contributor
timestamp: November 30, 2019, 08:32:36 am
content: The Cheap-Thermocam project is the cheapest. I did this scanning thermal imager. You need to remember the viewing angle of the sensor. Whatever system of movements along X and Y you choose. The maximum quality that I managed to get in the photo.

author: Vipitis
author_rank: Frequent Contributor
timestamp: November 30, 2019, 01:08:11 pm
content: You don't need a 3D printer as you only want 2 axis. And there is better ways to get a 2axis sensor moved, see the pinhole camera thread I posted.Uho reminded me of some teenagers DIY project that got posted here. I am looking for it now but found some more complicated ways to do the same thing.Filming a pyrometer display and translating that into values:https://www.niklasroy.com/project/195/DIY_thermal_imaginghttps://www.eevblog.com/forum/projects/diy-scanning-thermal-camera/I can't find the one that did scanning yet ..