Bandpass filter for blue light scanning

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OBNRacerMan
Posts: 27
Joined: 12 Aug 2019, 09:46
Location: Obninsk, Russia

Bandpass filter for blue light scanning

Post by OBNRacerMan » 19 Sep 2019, 07:27

Has anyone bought and used a bandpass filter 470nm to scan shiny and mirror objects?
Something like that - Azure BP470:
Azure_BP470.jpg
I saw these on a review of the Rangevision Pro 2M scanner
Azure_BP470.jpg (11.5 KiB) Viewed 156 times
P.S.
KH-013-6.jpg
In this photo, an IR filter (but looks like Azure (there is a golden hue))

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Micr0
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Joined: 15 Nov 2016, 15:20

Re: Bandpass filter for blue light scanning

Post by Micr0 » 20 Sep 2019, 13:06

I Played around with this with some cheap ebay filters and found that I couldn't control the wavelength of the projected light accurately enough and didn't get great results. My light sources were my LG LED projector and a cheap 720p portable laser projector. Neither I think was suitable to the task. My conclusion (after a very limited and amateur attempt) was that a proper light source probably would have proven better, but I can say. TBH I really didn't put a lot of time or though into it. It's obviously the way the high end scanners are doing it so i think it's certainly worth experimenting with. I'd certainly like to know what you find out.
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OBNRacerMan
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Location: Obninsk, Russia

Re: Bandpass filter for blue light scanning

Post by OBNRacerMan » 20 Sep 2019, 14:24

I will try to order them soon. In Russia, Azure BP470 is not a cheap filter (the cost of one filter is $ 80).
I found similar ones on AliExpress, but there is a small diameter, and the price is not much lower. So I’m almost sure that these filters are quite “correct”.
But there are some doubts about the "correctness" of my inexpensive Chinese LED-DLP projector ...

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Micr0
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Re: Bandpass filter for blue light scanning

Post by Micr0 » 21 Sep 2019, 14:25

I think part of the problem with media projectors they achieve whatever color they are projectiong by adding the red, green and blue LED light together. an LED that emits a specific wave length and a filter designed for precisely that frequency would be best. What is the wave length of the blue LED in any given projector? Im sure they differ from manufacturer to manufacturer. Can we specify that only that LED be illuminated? And can we get a filter to match. I guess more importantly, would it make a difference in our scans?
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OBNRacerMan
Posts: 27
Joined: 12 Aug 2019, 09:46
Location: Obninsk, Russia

Re: Bandpass filter for blue light scanning

Post by OBNRacerMan » 21 Sep 2019, 15:25

As far as I know, my projector uses three LEDs (R, G, B). And in the HP3Dscan program I use, there is a scanning mode in white light, as well as red, blue and green. Unfortunately, there is no exact data regarding the emitted wavelength of the blue LED used in the projector, unfortunately.

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