Results with Machine Vision Filters
Comparison to Photographic Filters
Comparison to Narrow Band Filters
Recommended Filters for Machine Vision
Kits for testing Filters and Lighting

Typical results when using Machine Vision Filters

1. Color recognition and separation of subject matter.
2. Suppress the strong blue "spike" of standard white LED and metal halide lighting.
3. Improve lens resolution and contrast by reducing the color range being imaged.
4. Eliminate glare.
5. Test the effects of Infrared light... see what our eyes can’t.
6. Enhance contrast for improved viewing of desired features.
7. Test LED colors without the expense and lead time of the lighting.
8. Radiation and temperature IR blocking with short pass filters to see and measure different temperatures of hot material.

 

1. Color recognition and separation of subject matter.

Lower cost, better speed, higher contrast and more consistent reliability can be achieved in some cases by using filters with a monochrome camera as compared to using a color camera alone.

The center image is through an unfiltered monochrome camera and shows how different colors can have similar grayscale intensities.
On the right, the BP525 filter lets the yellow and green colors through as near-white but blocks the red, turning it near-black.
Contrast like this makes for fewer false rejects and/or helps identify and isolate a specific color.

 

2. Suppress the strong blue "spike" of standard white LED and metal halide lighting.

Lower costs, brighter images and longer system lifetimes can be achieved by using the LA120 with standard lighting versus selecting "warm white" LED lighting.

By blocking most of the blue portion of the spectrum transmitted by white LED lamps, the product (below) has a more natural look to the human eye and can be filtered further for increased contrast for machine vision.

(left) 6500ºK LEDs put out a lot of blue.
(right) LA120 limits the blue for a more pleasing image.

 

3. Improve lens resolution and contrast by reducing the color range being imaged.

Better resolution reduces false accepts and false rejects, and the more expensive "megapixel" lensing may not be needed.

(left) Kale leaves under white light through a monochrome camera.
(right) MidOpt Bandpass Filter creates much greater contrast.

 

4. Eliminate glare.

When it is not possible to adjust a system's lighting configuration, polarized glare is selectively removed only through the use of a polarizing filter.

(left) Unfiltered monochrome image with ambient light.
(right) Correctly aligned polarizing filter eliminates the reflections.

5. Test the effects of Infrared light... see what our eyes can’t.

The very best contrast and separation of subject matter is often achieved by working in the infrared. The odds of this being immediately successful are about 50/50; testing is usually the only way to make such a determination.

(left) Monochrome image in white light shows too much information for efficient machine vision use.
(right) BP850 is used to block out unwanted elements for simple reading of the external barcode.

6. Enhance contrast for improved viewing of desired features.

Fluorescence applications require a filter to block the overwhelming light source that excites the fluorescence. Detecting the much weaker fluorescence is difficult if not impossible without blocking the light source and surrounding ambient light. A bandpass filter that only passes the limited fluorescence will significantly improve the contrast and allow the weak glow to be detected.

(left) Monochrome image does not record the subject.
(right) With LED and filter combination, bar codes become readily visible.

7. Test LED colors without the expense and lead time of the lighting.

Quickly test common LED lighting colors without the expense and time wasted while waiting for the appropriate LED lighting. Cut the lead time for bringing a system on-line by as much as several weeks.

(left to right) Ambient light, no filter... with BP525 Light Green Bandpass Filter... with BP660 Dark Red Bandpass Filter... with BP470 Blue Bandpass Filter.

The unfiltered image, as in the peppers example in point #1, show how different colors can appear the same in a monochrome system. Bandpass filters let only a narrow range of color through the lens while blocking all other color wavelengths.

8. Radiation and temperature IR blocking

Certain machine vision filters can be used to block the bright glow of hot metals, glass and other material. Shortpass filters allow light up to a specific wavelength to pass through while blocking all light at higher wavelengths. This useful feature permits, for example, the viewing of hot rolled steel to see certain temperature areas while not blinding the system from the brighter, hotter areas.

See SP510, SP570, SP585, SP625, SP645, SP700 and SP730