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Anonymous Poster

Color Sensors

01/17/2011 8:06 AM

what is the best way to sense coloured(red,blue) surfaces?
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Tornado
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#1

Re: sensors

01/17/2011 8:11 AM

An eyeball.

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#2
In reply to #1

Re: sensors

01/17/2011 8:22 AM

God, what a cynic. How about a spectral analyzer, or whatever else might turn up from a Google scrounge on "color sensors"?
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Tornado
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#3
In reply to #2

Re: sensors

01/17/2011 8:23 AM
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Doorman
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#5
In reply to #2

Re: sensors

01/17/2011 10:04 AM

I agree with our guest. Ask Blackle to arrange equipment by price, and select the most expensive.

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lyn
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#6
In reply to #1

Re: sensors

01/17/2011 11:28 AM

This seems to answer the OP directly, and correctly.

Just my 2 cents worth.
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Mikerho
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#7
In reply to #6

Re: sensors

01/17/2011 12:03 PM

I agree. It's too bad that the Guest OP won't get the obvious hint in Tornado's answer and come back with a better-formulated question, or at least some more information.

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RDGRNR
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#4

Re: sensors

01/17/2011 8:39 AM

Here's one company that has color sensors that you can "teach".

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Winfield Hill
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#8

Re: Color Sensors

01/17/2011 12:29 PM

The best way is to use accurate color filters with calibrated light sensors, calibrated at the wavelength of the associated filter. For really-high sensitivity, use a PMT sensors. Expensive.

The cheapest way, which supposedly works well at high light levels, is to use LEDs as light sensors. They're reputed to be sensitive only near the same wavelength as they emit light when powered. If you try this and it works out, report back and let us know about it. Good luck!

For example, this guy has found LEDs with 13 different wavelengths.

He also sends us to TheLEDLight.com, which has a nice LED color chart, with 18 different colors. Whoa! Fun for all!

��
� Wavelength
(nm)		 Color Name Fwd Voltage
(Vf @ 20ma)		 Intensity
5mm LEDs		 Viewing
Angle		 LED Dye Material
635 High Eff. Red 2.0 200mcd @20mA 15� GaAsP/GaP - Gallium Arsenic Phosphide / Gallium Phosphide
633 Super Red 2.2 3500mcd
@20mA		 15� InGaAIP - Indium Gallium Aluminum Phosphide
623 Red- Orange 2.2 4500mcd
@20mA		 15� InGaAIP - Indium Gallium Aluminum Phosphide
612 Orange 2.1 160mcd @20mA 15� GaAsP/GaP - Gallium Arsenic Phosphide / Gallium Phosphide
592 Amber
Yellow		 2.1 7000mcd
@20mA		 15� InGaAIP - Indium Gallium Aluminum Phosphide
585 �Yellow 2.1 100mcd @20mA 15� GaAsP/GaP - Gallium Arsenic Phosphide / Gallium Phosphide
3500K "Incan-
descent"
White		 3.6 2000mcd
@20mA		 20� SiC/GaN -- Silicon Carbide/Gallium Nitride
5000K Pale
White		 3.6 4000mcd
@20mA		 20� SiC/GaN -- Silicon Carbide/Gallium Nitride
6500+K Cool White 3.6 6000mcd
@20mA		 20� SiC/GaN - Silicon Carbide / Gallium Nitride
574 Super
Lime Yellow		 2.4 1000mcd
@20mA		 15� InGaAIP - Indium Gallium Aluminum Phosphide
570 Super
Lime Green		 2.0 1000mcd
@20mA		 15� InGaAIP - Indium Gallium Aluminum Phosphide
565 High�
Efficiency�
Green		 2.1 200mcd
@20mA		 15� GaP/GaP - Gallium Phosphide/Gallium Phosphide
560 Super
Pure Green		 2.1 350mcd
@20mA		 15� InGaAIP - Indium Gallium Aluminum Phosphide
555 Pure Green 2.1 80mcd
@20mA		 15� GaP/GaP - Gallium Phosphide/ Gallium Phosphide
525 Aqua Green 3.5 10,000mcd
@20mA		 15� SiC/GaN - Silicon Carbide / Gallium Nitride
505 Blue Green 3.5 2000mcd
@20mA		 45� SiC/GaN - Silicon Carbide / Gallium Nitride
470 Super Blue 3.6 3000mcd
@20mA		 15� SiC/GaN - Silicon Carbide / Gallium Nitride
430 Ultra Blue 3.8 100mcd
@20mA		 15� SiC/GaN - Silicon Carbide / Gallium Nitride
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Mikerho
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#10
In reply to #8

Re: Color Sensors

01/17/2011 10:20 PM

GA, Win! I have more than half of the colors of the LEDs on your list (for sure I don't have the pale yellow - for some reason they're quite elusive). If I tried something like this, my biggest concern would be intensity. Intensity levels discernable by the human eye vary with wavelength.

Thanks for the link and the idea.

Mike

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Mikerho
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#12
In reply to #8

Re: Color Sensors

01/17/2011 10:51 PM

And where to get these specific wavelength LEDs?

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#9

Re: Color Sensors

01/17/2011 3:01 PM

Depends a lot on the purpose for sensing the surfaces, and depends somewhat on whether the surface is reflective or emissive.

A pair of silicon photo-diodes can be mated with red and blue color filters to provide a simple go/no-go detection for each color.

A somewhat more elaborate method uses a colorimeter. This can be set up to detect specific shades of colors -- different shades of reds, blues, greens, etc.

The most exacting detector uses a spectroradiometer to examine the spectrum emitted from each surface. This would allow for variations in the illumination source if the surface is reflective (e.g., paints which might look different in different lighting conditions.)

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Mikerho
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#11
In reply to #9

Re: Color Sensors

01/17/2011 10:27 PM

Hi Usbport,

GA. I think you touched on the complexity of detecting the actual color of a surface. Now I just have to do some research on what the hell is a spectroradiometer!

Mike

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#13
In reply to #11

Re: Color Sensors

01/18/2011 7:55 AM

Thanks. You can get more info on spectrometers (and spectroradiometers, which are essentially the same things) from:

http://www.oceanoptics.com/

The ones from Ocean Optics are small, easy to use, and relatively inexpensive.

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#14

Re: Color Sensors

01/19/2011 5:02 AM

For detecting colored surfaces one best way to use color sensor is of specfied wavelength.

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Anonymous Poster (1); Doorman (1); lyn (1); Mikerho (4); RDGRNR (1); sajal mittal (1); Tornado (2); Usbport (2); Winfield Hill (1)

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