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NNTP-Posting-Date: Sat, 17 May 2025 22:43:07 +0000
From: Joe Gwinn <joegwinn@comcast.net>
Newsgroups: sci.electronics.design
Subject: Re: "Colorimeter"
Date: Sat, 17 May 2025 18:42:44 -0400
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On Sat, 17 May 2025 12:44:53 -0700, john larkin <jl@glen--canyon.com>
wrote:

>On Sat, 17 May 2025 12:30:38 -0700, Don Y
><blockedofcourse@foo.invalid> wrote:
>
>>Not quite, but, close enough...
>>
>>How can I determine the spectrum of incident light on a sensor,
>>in general?  Then, how many corners can I cut to sacrifice resolution
>>and accuracy?
>>
>>I've worked with true colorimeters (dual wavelength) in the past.
>>But, they were optimized to look for specific wavelengths.
>>
>>I calibrate the light emitted by my monitors with a device,
>>but it controls the light source to do so.
>>
>>With no knowledge of the actual (visible) spectrum impinging on
>>a sensor (and a bit of time to integrate results), how can I
>>do this short of swapping individual filters in front of the
>>sensor(s)?
>
>The people who make spectrometer-type instruments seem to be in a
>battle for ever finer resolution.
>
>I want a spectrometer that spans 400 to 1600 nm, or at least 800 to
>1600. I want to know if a 1310 nm laser is about 1310 and not by
>accident 1550 or something.
>
>I was thinking about making such an instrument. A few filters and a
>few photodiodes might work, with some overlap for interpolation.
>
>A rotating, graded filter and one wideband detector could work.
>
>Or a grating and a couple of detectors, with software to resolve
>ambiguities.
>
>Maybe just three detectors with different wavelength peaks.
>
>We did buy a couple of fiber WDM splitters, which can, for instance,
>tell us if a laser is 880 or 1300 or some such.
>
>Are there toy-level visual spectrometers?
>
>https://www.amazon.com/EISCO-Premium-Quantitative-Spectroscope-Accuracy/dp/B00B84DGDA/ref=sr_1_3?crid=21PO5QTTGGA06&dib=eyJ2IjoiMSJ9.IwA9B16820dPfj5ct0JEivvGqDD0YV5wFHFcG9c1Xss1BCoKEJvHFm_dYkhhHHK8lICo1KuioeQ85usmShFPtgMSSa0gzI2E-_x3ZbRTwkboNHcYYefd34pvzEKKty4RSFiiA4v0BSw_gbiEQH-khaK5lIXJ36q2q2xqW39hJj34hYp1MPTT9w4wb0RRE01F52nClp8J-VhECWQ18IWoopERU1Pl8khD8T_UPIBnauk.iFb6dsfIy8kEJvdCzNVyv8buyH2ji-Budd1i9iTh3IE&dib_tag=se&keywords=spectrometer+handheld&qid=1747511016&sprefix=spectrometer%2Caps%2C170&sr=8-3
>
>Cool. I just ordered one.

In October 2022 there was a SED thread on this, "on chip
spectrometer?".

Joe