Comments

Author Comment Last activity Moderation
stoft " Yes, once the camera exposure is under control (and fixed value) then the linearity can be measured -- IF you have controlled means of adjusting t..." | Read more » about 5 years ago
stoft "From that link, I found a 'settings' file here: https://gitlab.com/bath_open_instrumentation_group/picamera_cra_compensation/blob/fdb98308149e686a..." | Read more » about 5 years ago
stoft " Right, the camera's do automate as much as possible, which works against the needs of spectrometers. If the AGC cannot be shut off, then it become..." | Read more » about 5 years ago
stoft " Good work and observations. Yes, I think HDR techniques can help extract additional dynamic range from these simple cameras. In reading through yo..." | Read more » about 5 years ago
stoft "Progress. Right, the likely alignment issue is grating to camera which is notoriously hard to do without having much mechanical control beyond tape..." | Read more » about 5 years ago
stoft " Right ... the optical distances are very small ;-) which is why mechanical rigidity is so important ... (think of the 'optical bench' which is mad..." | Read more » about 5 years ago
stoft " A while back I experimented with some 35mm 'slide-mount' holographic grating film (I believe it was 1200) vs the DVD (which is 740). The diffracti..." | Read more » about 5 years ago
stoft " Looks like a nice clean construction. The glue should help mechanical stability. I did notice the swap from DVD to what appears to be a film holog..." | Read more » about 5 years ago
stoft " "The diffraction grating is not perfectly flat" would suggest you are using one of the readily available 35-mm laser holographic film gratings -- ..." | Read more » over 5 years ago
stoft "Nice graphics. Yes, white LEDs are not broad spectrum. If it's of any help, I set (Matlab code) the ELP camera to: Manual Exposure, Exposure=-3 (-1..." | Read more » over 6 years ago
stoft "Ah, good. Glad you could view the additional data and figured it out. " | Read more » over 6 years ago
stoft "Yes, clearly all but the last image shows compression in the Green (and Red though less). Because the process of spectral data from a webcam does n..." | Read more » over 6 years ago
stoft "The camera's I've used seem different in this effect but you might try to hunt down the technical data sheets from the Mfg -- sometimes they have a..." | Read more » over 6 years ago
stoft "@Tehnicni, I'd agree that any detector-specific non-linearity is likely very small compared with the effect you've presented. I'd guess the more li..." | Read more » over 6 years ago
stoft "There's still some clipping (source light intensity too high) so a comparison, using a cardboard mask (with a small hole in it), between the two bu..." | Read more » over 7 years ago
stoft "No I don't think it is just inherent in the camera. The blue led has a fairly narrow spectrum (say 25nm at most) so producing a 150nm 'spread' woul..." | Read more » over 7 years ago
stoft "I note that 1) your spectrum does "fit" though it is 2) "offset" a bit from center which is likely related to the angle. (Just to identify what is ..." | Read more » over 7 years ago
stoft "The angle is a function of (mathematical) of the detectable wavelength range and the diffraction grating (DVD) line spacing. My calculations and my..." | Read more » over 7 years ago
stoft "@stef, thanks for the curve data. While the data is useful for comparison with relative sensitivity curves of other cameras, the data, unfortunatel..." | Read more » over 7 years ago
stoft "What I've read is that the RPi camera used to use the OV5647 camera chip but has "upgraded" (changed chips) to a Sony IMX 219 PQ CMOS image sensor ..." | Read more » over 7 years ago
stoft "Jeff, I inserted the component details in the note above, just before the plots. As to the RPi camera, it seems to have two "difficulties" which n..." | Read more » over 7 years ago
stoft "Jeff, yes, the data is being collected, and yes, higher resolution does improve observation of detail like slit differences. I'm evolving some new ..." | Read more » over 7 years ago
stoft "Thanks Jeff; understood. I'm presently working on a higher resolution P-4 spectrometers (including monochrome) so might find a spot for comparison ..." | Read more » over 7 years ago
stoft "@warren, I'm not sure I follow the linking details for grids etc., but more abstractly, a tree structure comes to mind. This note describes one com..." | Read more » over 7 years ago