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From: Lasse Langwadt <llc@fonz.dk>
Newsgroups: sci.electronics.design
Subject: Re: "Colorimeter"
Date: Thu, 29 May 2025 01:11:20 +0200
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On 5/25/25 11:07, Martin Brown wrote:
> On 24/05/2025 21:07, Don Y wrote:
>> On 5/19/2025 1:33 PM, Lasse Langwadt wrote:
>>> On 5/18/25 21:45, Don Y wrote:
>>>> On 5/18/2025 6:13 AM, Lasse Langwadt wrote:
>>>>> On 5/17/25 23:03, Martin Brown wrote:
>>>>>>
>>>>>> If you are serious about doing this right then a 2D CCD sensor and 
>>>>>> a prism hires grating combo at right angles will allow you to 
>>>>>> quantify the entire visible spectrum at ultra high resolution. 
>>>>>
>>>>> use a CD https://youtu.be/EoAZ-u6hn6g?si=Mv-DfJ5swtq2-j1X&t=98  :)
>>>>>
>>>>> eons ago we used some CCDs as detectors for X-ray fluorescence, 
>>>>> some had weird formats like 1024x64 pixels so I assume they were 
>>>>> really made for spectroscopy
>>>>
>>>> As mentioned elsewhere, how do they fare when light is shining 
>>>> directly on the
>>>> sensor?  How do you keep it from saturating -- dark lens to 
>>>> attenuate the signal?
>>>
>>> or a shutter to limit the time light hits the sensor
>>
>> There's still a limit as to the peak intensity that a sensor can
>> tolerate.  And, gating the light (instead of attenuating it)
>> means there is no signal when the source is gated off.
> 
> Simplest solution is to limit the aperture that you let the light in 
> through which is normally focussed onto a narrow slit anyway. You might 
> get a bit of an issue with readout smearing but it probably won't be too 
> bad.
> 
> Please bear in mind that my experience with spectroscopy the problem was 
> mostly getting enough light to have *any* signal to noise.
>>
>> Fine if you are making a device with a button that says "measure now".
>> But, if you expect to be able to collect data at any time, you
>> want to be sure data is available.
> 
> In extremis the measure now button could just move a spring loaded 
> mechanical shutter that normally blocks the light path.
> 
> Unless the thing is imaging a nuclear blast, steel furnace or an arc 
> lamp then I don't think light intensity is likely to harm a modern CCD. 
> There are hot mirror and anti-UV low pass filters to protect such 
> equipment from hostile radiation.
> 

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