baffe Posted May 17, 2015 Share Posted May 17, 2015 Just Another Simple Spectroscope: First I read some articles on the web about spectrometer construction. http://saisa.eu/blogs/Guidance/?p=1065 http://www.popularme...meter-14908361/ https://www.flinnsci...roscope__1_.pdf http://saisa.eu/blogs/Guidance/?p=1065 They show how to prepare the CD to get a grating: http://www.euhou.net...de-spectroscope Then I did a lot of tests to determine distances, measurings, angles and so on. I tested CD's (big range but bad resolution) DVD's (good resolution but small Range and bluray's (almost impossible to handle). I decided to use a DVD for the spectroscope shown here. The operating range ends at red, where the performance appears to be very poor. It shows no infrared but reaches into uv as far as possible but limited by the lens and the webcam's chip. And limited of course by the uv abilities of the used DVD grid. The whole instrument is built into and around a 7/16" professional RF-Connector, it's male and it's female part. After disassembling them removed the center pins with insulation first.I took the cable intake part, soldered a brass plate onto it to cover the cable entrance and drilled a deep 1,5mm hole into brass plate and housing to get the visor. http://up.picr.de/21948321on.jpg Then I drilled a 2,5mm hole into the plug, cut a M3 thread in to have a possibility to secure the installed and aligned visor.The circuit board of the USB webcam was glued onto the thread of the female connector. The front element of the lens was removed (to increase focal length) and the filter removed from the lenses back side. The DVD grid was put into the connector thread, aligned and fixed by screwing the plug in and tightening it.Then the visor was mounted, adjusted and secured with the M3 screw. And the whole unit disassembled some times to adjust and test focus alternating.After finding the correct setting the whole units inside was painted black and covered with black rubber foam to reduce the stray light. This is the finished spectroscope unit. http://up.picr.de/21948322dp.jpg http://up.picr.de/21948323hs.jpg http://up.picr.de/21948324ij.jpg The module was installed into a blue painted aluminium cast housing with some 1/4" UNC threads for mountig a tripod and acessories. Here are the parts: http://up.picr.de/21948325qt.jpg http://up.picr.de/21948326dj.jpg And the finished instrument: http://up.picr.de/21948327tu.jpg http://up.picr.de/21948328yc.jpg And this is a file straight out of the cam (daylight through insulating glass): http://up.picr.de/21948329tp.jpg Later I calibrated the unit and wrote a small software in "lazarus" wich is very close to borlands Turbo Pascal but runs in Windows 7.0. The frame shows the analyzed area in the file: http://up.picr.de/21948395ma.jpg Intended to prepare the files automaticly in size and put them into a calibrated grid: http://up.picr.de/21948396sx.jpg Explanation about the markers: http://up.picr.de/21948397to.jpg Finally here are some samples. Noname "uv" lamp: http://up.picr.de/21948392cv.jpg http://up.picr.de/21948393bs.jpg White LED: http://up.picr.de/21948394mm.jpg MTE301 365nm lamp: http://up.picr.de/21948398uf.jpg http://up.picr.de/21948399wx.jpg I want to thank my friend Dr. Klaus Dieter Schmitt for his help! Especially in measuring my homemade LED lightsource (thermic stabilized to 52°) and giving me documentation about it. It was very important to calibrate the wavelength in the software according to the instrument. And he gave me some helpful hints improving my english. baffe Link to comment
colinbm Posted May 18, 2015 Share Posted May 18, 2015 Good on you Stefan, keep at it, it is great to see you doing & learning all this, wonderful Col Link to comment
nfoto Posted May 18, 2015 Share Posted May 18, 2015 "Simple" takes on an extended connotation ..... Nice work. And the tiny tripod is cute, too. Link to comment
baffe Posted May 19, 2015 Author Share Posted May 19, 2015 Oh i like this small tripods! I have some of them. Otherwise you find yourself with one hand on the spectroscope, the other on your lightsource. Both pressed together to hold a filtersheet between. Everything is ok but you haven't got a third hand to click a mousebutton. So don't worry, call batman. -or use that funny tripod! Link to comment
Alaun Posted May 19, 2015 Share Posted May 19, 2015 Hello Stefan, very nice work! Seeing your post, I experimented a little bit anda few questions come to mind. You have to focus on the gap (here hole), so I assume the web cam -with your design-has to have a very short minimal focusing distance. A digital microscope camera perhaps? (I have no clue about web cams). To get the full picture of the spectrum on the sensor, you have to move the grating (DVD) rather close to the gap. So your "gap size” )=drilled hole diameter) is rather large compared to your picture /sensor size. So even a single peak signal would be “smeared” as a kind of steep hill I assume. Though the hole might be nice to bring a light source via a fiver to your spectromter, did you try to “make your hole/gap more look like a narrow gap” to improve the resolution? (The peaks of your UV-lamp curves seem to show this very nicely). Can you control the exposure with the web cam (something you might need to do with a narrower gap)? The “missing” IR response, is that due to a -still in place- IR-filter in the camera? (Might be helpful in blocking out visually interfering higher degree spectrums?) Werner Link to comment
baffe Posted May 19, 2015 Author Share Posted May 19, 2015 Hi Werner! Thanks! The lens used in my unit ist not it's own lens bt the lens of different cam and that even modified. But every webcam that I ever tested has a very close minimal focus distance. Of course the cam can not show a spike, but the MTE301 look like that (1:1 crop from software delivered bmp):http://up.picr.de/21966618ov.jpg I have calibrated gaps with about 0.5mm and one adjusteable currently ajusted to 30µm:http://up.picr.de/21966721yj.jpg http://up.picr.de/21966722xr.jpg This is the picture with a gap. http://up.picr.de/21966723by.jpg I came to the drilled hole to get some more low light performance. Even if the files are not so sharp because of better overall performance. The dvd grid is not as "passive" as it should be. At wavelength much shorter than 350nm it doesn't work at all. There are some reasons for the missing infrared abilities. First the grid from dvd-r is blue. And the red comes out of the grid more flat than blue. I removed the coated front elemt from the lens but there is still something shimmering in it. But it works useful to 350nm. No I do not have a fiber that is useful for that. And I don't need that fpr my puposes too. Link to comment
Alaun Posted May 19, 2015 Share Posted May 19, 2015 Stefan, thanks for the information. It seems, further improvements are on track ;-) (with all your housings, are a "Funkamateur" ?) Link to comment
baffe Posted May 19, 2015 Author Share Posted May 19, 2015 Oh I'm not finished with that theme yet. So that is a already working narrow band spectrometer with electric servo adjustment for different wavelength. http://up.picr.de/21967571ra.jpg No I'm not a "Funkamateur" (in english Radio amateur) :-) Link to comment
colinbm Posted May 20, 2015 Share Posted May 20, 2015 Hi StefanYou don't need a lens, the slit becomes a 'pinhole' & you are effectively focused at infinity.Col Sorry StefanI was thinking of the Amisi Prism Spectroscope that I use.Col Link to comment
baffe Posted May 20, 2015 Author Share Posted May 20, 2015 The slit makes pictures "looking better to the eyes". The round hole produces some kind of corona around the image of a spike if overexposed. This enables the software to detect a maximum even if the image (I don'n use a line but an area!) is totally overexposed. If underexposed then you get a significant "area of increased noise" where the software's statistic functions also can detect a maximum and this works very well too. But of course you loose some resolution... Best would probarbly be a slit with the edges not in parallel. I'm thinking of a slit in delta shape. This will produce both in the image, lines with high resolution because they are correctly exposed and also lines with lower exposure to find maxima at high levels and of course lines with higher exposure to work at lower resolution at lower light levels. There's only one problem: I don't have a drill that drills triangular holes. ggg The blubox is not a precision instrument, but it shows a good overview... The black one shows better results but first one has to calibrate it before every use (the wavelength scale), adjust the range by reading the multimeter display according to a spreadsheet. And of course focus referring to that has to be adjusted afterwards and the exposure has to be measured out very carefully. I'm going to disassemble that black thing anyway because the plastic housing is too floppy and bends if you don't use a trigger delay on the cam. The blubox doesn't suffer from that problems at all! No moving parts and a very compact bulletproof housing... Link to comment
baffe Posted May 21, 2015 Author Share Posted May 21, 2015 Following Werners hint with the fiber i took a 62,5/125 fiber of 1m length to cover both, light input and narrow gap. I used my Samsung NV7 (unmodified) fired the flash straight into the fiber at no distance. I put a Grid onto the lens, focussed onto the other end of the fiber and made a shot. http://up.picr.de/21986261fx.jpg The bluspec software was used to analyze the shot. The lambda calibration oft the bluspec spectroscope is not valid! http://up.picr.de/21986262ts.jpg Resolution is really good but the loss of light is tremendous. Remember the fiber is held direct onto the lighting surface of the cams flash. Link to comment
Alaun Posted May 21, 2015 Share Posted May 21, 2015 But it seems you still got a signal. The entrance of the fiber might have an influence? Is it like a mirror surface, then you might need to take care of the inclination so the light from the flash is not reflected. Can you expose for a longer time and ignite the flash several times? Werner Link to comment
baffe Posted May 21, 2015 Author Share Posted May 21, 2015 Oh this little test was ok. But sometimes I have sources a little darker than a flash. I'm not talking about the 1 or 2 decibels a better fiber alignment will save... Link to comment
Andrea B. Posted May 22, 2015 Share Posted May 22, 2015 I've been reading as the work continued and thought I should say hello. Excellent experiment, Baffe !! ;) Link to comment
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