Red LED vs. White Light Inspection Lamp

R

Roscoe Splevins

We are presently using white illumination for our inspection department vision system. The lamp has some damage and we will replace it. A lot of new lamps are RED LED. What is the reason for this? We are inspecting polished metal products for surface and dimensional requirements. Color is not an issue.

I've looked at the lamp vendors' promotional information and found no reason or justification for the red vs. white light. Most stock both.

Immediate use will be the inspection department vision system and microscope but we would likely extend the red lamps to production inspection lamps IF there is good reason.

Thanks
 

bobdoering

Stop X-bar/R Madness!!
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We are presently using white illumination for our inspection department vision system. The lamp has some damage and we will replace it. A lot of new lamps are RED LED. What is the reason for this? We are inspecting polished metal products for surface and dimensional requirements. Color is not an issue.

I've looked at the lamp vendors' promotional information and found no reason or justification for the red vs. white light. Most stock both.

Immediate use will be the inspection department vision system and microscope but we would likely extend the red lamps to production inspection lamps IF there is good reason.

Red lamps were common as the red LED was the cheapest and most plentiful at one time. The biggest issue I have ever seen is masking some unexpected conditions, especially rust.
 
M

MIREGMGR

About 8% of males of primarily northern European ancestry are protanomolous trichromatic, i.e. red-green colorblind. This means in practice that they have considerably diminished visual sensitivity to monochromatic red light. In other words, your inspected samples will appear to be illuminated to a much lower brightness.

Since visual acuity is related to brightness, the use of red light for inspection is in my opinion always highly undesirable unless the task technically requires it, and the persons selected to do the inspection are qualified via a suitable optometric testing process.
 
T

The Specialist

Since visual acuity is related to brightness, the use of red light for inspection is in my opinion always highly undesirable unless the task technically requires it, and the persons selected to do the inspection are qualified via a suitable optometric testing process.


I am inclined to agree with this, however...

Is there a 'glare' issue here with 'white' LED use?

Just a thought!
 
M

MIREGMGR

Glare occurs when source intensity, including apparent sources such as specular reflections, is at too high a level for the light acceptance range of the human eye with maximum pupillary contraction. Glare hinders

I don't know of any biological reason why glare would be spectrum or light-color related.

Of course, very high magnification systems may need monochromatic illumination when the features being viewed are sufficiently small or the optical situation includes features such as view through a grating, and the wavelength of light becomes important because of diffraction and interference phenomena.

For macro inspection, though, white light seems to me to be a good choice.
 
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S

Sturmkind

Most North American OEMs within their appearance standards specify lighting. The example below was quoted from GMN6995 for Chrome Plated Parts Appearance Standard:

"The lighting for surface blemish inspection shall
meet or exceed 100 maintained foot-candles. All
horizontal and vertical fluorescent fixtures are to
have a cool white, 800 milliamp, high output,
110 Watt bulbs. The evaluation shall be
performed at arms length (3/4 to 1 m) and​
viewed in car position."
 
R

Roscoe Splevins

Decision has been made with the assistance of your responses. Red LED is out. We will be going with white light. All of the above is valid consideration. But the general requirement for "white light" in our "unaided" inspections by customers has been the decision to use only white for our vision system also.

Thanks to all for the assistance!
 
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