Optical bench for lens experiments - cheapest commercial kit that I could find - Page 1
Forum section: electronics / general

author: Fraser
author_rank: Super Contributor
timestamp: February 10, 2022, 01:22:19 pm
content: I would be the first to admit that I only know the basics of optics, as taught to me many decades ago in school physics !To improve my knowledge of infrared optics, as used in thermal imaging systems, I bought some excellent books in the topic. I suggest buying such reference books ‘used’ as they can be very expensive new.I have wanted some form of basic optical bench on which to test thermal imaging lens element combinations and other experiments in the thermal IR wavelengths. Upon searching for a used optical bench, as used in schools etc, I was greeted with little availability used and high prices for new kitsI had an idea in my minds-eye as to what I wanted but sadly such optical benches cost around £300 ! The desire for Champagne when on a Beer income !Plan B was a compromise solution….. either make my own optical bench using a 3D printer and some hardware, or buy the cheapest basic optical bench available and modify it to my requirements. Having a basic design on which to create a custom solution can save time and effort if the basics are adequate. I found 3D printable designs for end blocks and lens holders so that is definitely a way forward on a budget. I found a very cheap and nasty looking basic optical bench intended for schools that uses a wooden 1m ruler as the ‘bench’, but that looked too flimsy and nothing like what I wanted. The next cheapest option was a somewhat cheap looking basic optics experimentation kit from a company called “Teenii” that is intended for STEM educational use. Though it appeared ‘built down to a price’ the kit still costs around £50 newThis is the price of educational materials !From what I could see, the Teenii Optics kit would be a useful baseline on which to create my optical bench and it provided some useful optical experiment bits and pieces with which I could experiment in the visible light domain, if desired. I searched for used examples of the kit but none were found. I then found a company selling the kit new at £40 and they recently discounted it down to £35. I offered £30 and got their last kitThe Teenii STEM educational optics experimentation kit arrived today. It is as cheaply made as I had expected, but it shows promise in the areas of importance to meThe parallel slides are in two pieces that screw together but it is possible to use the shorter slide pieces to make a compact optical bench, as I will likely need. The end caps/mounts are of decent manufacture and good enough for my needs. The slides that mount on the parallel rails are also of adequate quality and may be easily adapted to my needs by fitting custom lens holders.The visible light experiment components are cheaply made, but appear fit for purpose in their originally intended role. I may adapt the light source ‘F’ or ‘RGB’ units to a thermal source by using suitable SMD resistors in place of the LED’sThe kit uses a translucent plate as the rear image creation field but I will modify one of my Uni-T UTi80P thermal cameras to capture the thermal images coming from experimental lens systems, or complete lenses. I need to also test for back focus distance and image circle size. The UTi80P uses the FLIR Lepton 2.5 and I will be removing its lens so that I can directly illuminate its microbolomter. The FFC shutter is kept as it does not cause obstruction of the microbolomter. The UTi80P will need to be mounted on an X-Y vernier plate for fine adjustments. I may already have such a plate in my collection of industrial camera accessories.I hope to end up with a decent test bench for complete lenses and experimental lens element combinations. If I can achieve that with this £30 investment I will be happyFor anyone wishing to experiment with thermal imaging lens elements on an optical bench, the Teenii kit, or similar kits from AliExpress, may be a useful starting point. Alternatively, make your own using the available 3D printable designs on Thingiverse. At the end of the day you are just making a platform to support lens elements and the output detection system in correct axial alignment with accurate inter-element distancesFraser

author: Fraser
author_rank: Super Contributor
timestamp: February 10, 2022, 01:30:34 pm
content: The 80 x 60 pixel Lepton equipped Uni-T UTi80P that I will use as the image receiver from the optical experiments. These were recently purchased cheaply, as detailed in another thread on this forum.https://www.eevblog.com/forum/thermal-imaging/cheap-new-basic-thermal-camera-on-ebay-multicomp-uni-t/The Leptons’ lens will be removed but the FFC shutter and dust protection window will be retained.The camera incorporates a standard tripod mounting 1/4 x 20Tpi thread which will simply its mounting for experiments.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: February 10, 2022, 01:58:21 pm
content: Optical bench stuff on thingiverse……https://www.thingiverse.com/thing:2862854https://www.thingiverse.com/thing:49942https://www.thingiverse.com/thing:2336754https://www.thingiverse.com/thing:3535295This is the one that I was going to build if I had not found the Teenii kit.https://www.thingiverse.com/thing:3758534

author: Fraser
author_rank: Super Contributor
timestamp: February 10, 2022, 02:20:33 pm
content: The cheapest optical bench I found that uses a simple wooden ruler and pressed metal parts. Only £17, but probably best avoided IMHO. There is such a thing as being too ‘cheap’.https://www.rapidonline.com/Rapid-Complete-Optical-Bench-Set-06-2242?IncVat=1&utm_source=google&utm_medium=surfaces&utm_campaign=shopping%20feed&utm_content=surfaces%20across%20google&pdg=kwd-294357559827:cmp-810438953:adg-43544079578:crv-192262852978:pid-06-2242&gclid=Cj0KCQiAjJOQBhCkARIsAEKMtO3oMDQ8h_GDrsdiELX1-YLRNcjblWF6SvDGqCEyYk_64xH90aIHnbEaAn2OEALw_wcBFraser

author: Fraser
author_rank: Super Contributor
timestamp: February 10, 2022, 02:38:50 pm
content: A similar kit to mine from AliExpress…. £32 delivered.https://www.aliexpress.com/item/4000626200368.html?spm=a2g0o.productlist.0.0.6e7a20a60DPaot&algo_pvid=e0c70e7f-932d-4785-a110-327c87b6afbe&algo_exp_id=e0c70e7f-932d-4785-a110-327c87b6afbe-0&pdp_ext_f=%7B%22sku_id%22%3A%2210000004321895860%22%7D&pdp_pi=-1%3B32.34%3B-1%3B-1%40salePrice%3BGBP%3Bsearch-mainSearchFraser

author: Fraser
author_rank: Super Contributor
timestamp: February 10, 2022, 04:08:41 pm
content: I quickly assembled the little optical bench for some photographs. I am only using half of the available parallel guides as that is all I think I will need for most tasks. This removes alignment/droop issues that a join half way along the parallel guides may introduce as well. The shorter optical bench is more rigid as wellThe good bits….. it assembles in seconds and looks like it may actually work !The bad bits … yep it is built down to a price, the parallel guides are thin wall hollow tubes with nuts and bolts forced into their ends. The sliding lens holders are laughably loose on the guide rails. Only one sliding lens holder is fitted with a lens ‘lollipop’ securing screw.Is it a lost cause ? No, as all defects in the design are relatively quick and easy to fixOut of the box it leaves something to be desired thoughMore of a toy than education grade apparatus.Sorry about the poor picture quality….. the combination of poor lighting and an iPad with image file size reduction employed really makes a mess of things !Fraser

author: Fraser
author_rank: Super Contributor
timestamp: February 10, 2022, 05:06:38 pm
content: In case of interest, these are three of the reference books on optics and optical system design. I chose them due to their reputation for being excellent reference books. As previously stated, such reference books can be very expensive. I found mine on eBay and by searching on-line text book finder services.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: February 10, 2022, 07:53:36 pm
content: So to summarise my thoughts on the Teenii Optical Bench....Is it worth the original £50 asking price ? ..... in a word Nope ! Some UK based sellers are asking £100 for this kitCan the unit be adapted for use with thermal imaging lens elements and a thermal camera ? .... YesWould I recommend buying the Teenii Optical Bench instead of making an optical bench from 3D printed parts and some tubes ? .....That is a harder question to answer. The Teenii kit is more than just the optical bench rail unit and some buyers will gain useful knowledge from the experiments that may be completed with the provided light sources, lenses and beam refraction blocks.For a dedicated thermal imaging optical bench at reasonable cost...I would go with the 3D printed parts and some tubes to make my own unit. This depends upon the ability to print your own 3D parts or obtain them for reasonable cost though.For the £30 that I paid, I am not disappointed, but be under no illusions.... the Teenii Optical Bench is little more than a toy in its delivered state. As part of the kit, the bench is only used for a few simple, undemanding, experiments and only with a single lens or pin hole. The rest of the kit uses a triple laser beam source and optical elements to learn about reflection and refraction.For those wishing to go down the 3D printed DIY path, I believe this design is fit for purpose......https://www.thingiverse.com/thing:3758534Fraser

author: Bill W
author_rank: Super Contributor
timestamp: February 10, 2022, 11:25:26 pm
content: Maybe just some matching runs of angle would do well ?https://www.aluminiumwarehouse.co.uk/30-mm-x-30-mm-x-3-mm-aluminium-angleAll the benches I ever used were machined or extrusion, not rods.Bill

author: Fraser
author_rank: Super Contributor
timestamp: February 11, 2022, 01:22:01 am
content: Yes, very much like the bed of a lathe….. cast or machined rigid beds are preferable to parallel bar type designs.A lab grade optics bench is a tight tolerance, rigid structure that is capable of maintaining axial alignment etc, especially if it is an optical bench being used for laser experiments.With some time and a bit of investment in some suitable raw metal, I could make something pretty decent . A future project maybeFraser

author: JohnG
author_rank: Frequent Contributor
timestamp: February 16, 2022, 01:08:14 am
content: For what it is worth, I use 20 mm x 20 mm aluminum V-slot extrusions for basic optical work and miscellaneous other fixturing. It's the same stuff used for my Ender 5 printer. You can buy lots of fittings, brackets, etc. It's cheap and rigid enough that you can even build some semi-permanent items out of it. If you need something more rigid, you can get 2040, 2060, and even 4040 versions, though 2040 is the biggest I have used. Highly recommended by this non-expert.You can also find lots of models for 3D printed versions of these 2020 extrusion accessories. I have been pleasantly surprised at how well some of these work, given that they are printed plastic. I have also made some basic lens holders in FreeCAD, and some other fixtures. I am not a FreeCAD (or any kind of MCAD) expert, but even so I have made some very useful fixtures and even saved some time here and there.Cheers,John