BUILD A
            V I S I - S P E C T R U M            
SPECIAL VISION NEEDS
LIGHT SOURCE

WHY DO WE NEED IT?

People with defective color vision need aids to identify colors.

Here are some examples of how defective color vision causes troubles:

  1. People assembling electronic components can't read the color codes identifying the various parts. They insert the wrong parts, because they can't tell the different color codes apart. Repairmen have the same troubles.
  2. Artists make paintings that unintentionally contain colored objects with the wrong colors.
  3. Room decor looks very different to others than intended.
  4. Clothing that appears to match to the wearer does not match.
  5. Color codes used to identify objects are misidentified.
  6. Reading railroad, aircraft, airport, ship, and traffic signal lights requires good color vision.

WHAT CAN BE DONE?

People with defective color vision need special lights or filters to identify colors.

Since the person can see the colored light reflected from objects, but cannot distinguish some colors from others, special lights or filters are needed to identify the colors. There are several different methods, depending on the type of color vision defect:

WHAT CAN BE USED?

The Visi-Spectrum Light

Available Lamps

This is based on the fact that the person has three types of color-sensing cones. By restricting the sensations to the three primary colors, this simplifies the sorting of the colors. In some cases of anomalous color vision, the person will see the colors that people with normal color vision see.

The spectra shown are artificial images based on spectra obtained by the methods shown here:
Build a Spectroscope

The problem is finding a source of light with red, green, and blue wavelengths, but with no other colors present. Here are some of the available products that can be used:

                                                   

Color TV Screen Narrow band spectrum Works by itself.

                                                   

Color TV Screen Wide band spectrum Does not work.

                                                   

Daylight CFL Bright line spectrum Might work by itself.

                                                   

Triphosphor CFL Bright line & band Might work by itself.

                                                   

LED Tricolor Use gaps in spectrum Works by itself

                                                   

Bicolor Yellow CFL Gaps in spectrum Won't keep bugs away

                                                   

Monochrome Yellow LED Specialty party bulb Not Visi Spectrum (see below)

                                                   

Monochrome Orange LED Specialty party bulb Not Visi Spectrum (see below)

                                                   

Red Hg Phosphor CFL Specialty party bulb  

                                                   

Green Hg Phosphor CFL Specialty party bulb  

                                                   

Blue Hg Phosphor CFL Specialty party bulb Some brands

                                                   

Blue Ar Phosphor CFL Specialty party bulb Some brands

                                                   

Cyan LED Specialty party bulb Not Visi Spectrum (see below)

                                                   

Blue LED Specialty party bulb Visi Spectrum

The RGB Method

Choosing lamps for the various kinds of color blindness

There are three kinds of color vision defects:

  1. Anomalous trichromatic vision, where one or more cones have the wrong color response

    This includes protanomaly, deuteranomaly, and tritanomaly.

  2. Dichromatic vision, where one cone type is missing or two cone types appear identical

    This includes protanopia, deuteranopia, tritanopia, and red-green indistinction.

  3. Monochromatic vision, where only one cone type works, or only rod vision works

    This includes monochromatism (only blue cones) and cone blindness.

The following lamps or lamp combinations are useful:

A separate white light can be added for times when color identification is not important.

The Separate Color Method

Choosing lamps for protanopia, deuteranopia, tritanopia, and other defects

The following lamps or lamp combinations are useful:

The Added Color Method

Choosing lamps for color identification

The following lamps or lamp combinations are useful:

BUILDING A LAMP ARRAY

Selecting the color circuits needed

The complexity of the system you make depends on your needs. For some, only one combination of lighted lamps may be needed. For others, many different circuits may be used. Here are some suggestions of what to use:

  1. The RGB Method
  2. The Separate Color Method
  3. The Added Color Method

Designing a fixture

Any of the following can be used to provide a fixture to hold the lamps:

Wiring the circuits for the lamps

lamp circuits The following lamp fixture wiring methods can be used:

lamp switches The following lamp fixture wiring methods can be used:

The Author's Setup

Here is the page author's full-spectrum setup.

Switches off

The page author used an old store display fixture he got at a store-closing sale for a dollar to build a full-spectrum light source. The same kind of fixture can be used for the special vision needs fixture.

lamp switches The switchbox is designed to switch four kinds of lamps:

FULL SPECTRUM LAMP POSITION SPECIAL NEED
LAMP COLOR SWITCHES LAMP COLOR SWITCHES
Daylight CFL CFL Positions 1 and 8 Daylight CFL CFL
Soft White LED WARM Positions 3 and 5 Red CFL RED
Daylight LED COOL Positions 4 and 6 Green CFL GREEN
Blue CFL BLUE Positions 2 and 7 Blue CFL BLUE

Photos of what the lamps look like when on, with approximate spectral distribution:

DISPLAYPHOTOSPECTRUM CFLWARM COOLBLUE
All lights off Switches off

                                                   

OFFOFF OFFOFF
Blue on Blue on

                                                   

OFFOFF OFFON
CFL on CFLs on

                                                   

ONOFF OFFOFF
Full-spectrum
(All but CFL)
Full spectrum

                                                   

OFFON ONON
All lights on All lamps on

                                                   

ONON ONON
The fixture above could be used instead to switch red, green, blue, and white lamps.
The photos below are altered in color, because the author does not have the colored lamps.
DISPLAYPHOTOSPECTRUM CFLRED GREENBLUE
All primary on All primaries on

                                                   

OFFON ONON
All lights on All lamps on

                                                   

ONON ONON
CFL with
Added Red
CFL added red

                                                   

ONON OFFOFF

Additional Tools

The charts at the right can be used to help the user identify colors. Print them on a color printer. Then look at them under the special vision lights to see what the colors are supposed to look like.

primary colors The upper chart has the primary colors of light:

The circles overlap to produce the secondary colors, with white in the center:

primary colors The lower chart has a range of colors:

  1. Magenta
  2. Cerise
  3. Red
  4. Orange
  5. Yellow
  6. Leaf
  7. Green
  8. Aqua
  9. Cyan
  10. Azure
  11. Blue
  12. Violet

Color filters can also be used to help identify colors.






SIMULATING DEFECTIVE COLOR VISION

Build a lamp array to show people with normal color vision how colors appear to the color blind.

Color blind simulator The lamp array contains the following colors of lamps.

Additional lamps may be used to simulate more cases:

Use the following settings to simulate various kinds of color vision.

COLOR VISION TYPELAMPSSPECTRUMFILTER
Normal color vision Red, Green, Blue †

                                                   

None ‡
Protanomaly Yellow, Green, Blue

                                                   

Special
Deuteranomaly Red, Yellow, Blue

                                                   

Special
Tritanomaly Red, Green, Cyan

                                                   

Special
Protanopia Green, Blue

                                                   

Cyan
Deuteranopia Red, Blue

                                                   

Magenta
Tritanopia Red, Green

                                                   

Yellow
Red-Green Indistinction Yellow, Blue

                                                   

Special
Red-Green Indistinction (sharp) Yellow, Blue

                                                   

Special
Red-Green Indistinction (sodium) Yellow, Blue

                                                   

Special
Alternate Form 1 of Protanomaly Orange, Green, Blue

                                                   

Special
Alternate Form 1 of Deuteranomaly Red, Orange, Blue

                                                   

Special
Alternate Form 2 of Protanomaly Chartreuse, Green, Blue

                                                   

Special
Alternate Form 2 of Deuteranomaly Red, Chartreuse, Blue

                                                   

Special

†   A white light can be used here.
‡   The EnChroma glasses could be used instead of no filter.

Note that for this to work correctly, the following must occur:

What the page author used:

In addition, the page author had to make changes to the outputs of these LEDs using filter covers to obtain other colors used in the charts above:

When the page author used a Feit Yellow LED with red and green color filters to make the bandwidth narrow enough that he could not see differences between red and green for the Red-Green Indistinction setting, the filters cut the light output so much that he had to use twice as many lamps.

One possibility for a pure yellow light source for Red-Green Indistinction is a low-pressure sodium lamp.

One possible set of observations to make during these experiments might be to use the two sets of samples used in The Crayon Trials. Particularly notice what happens to the appearance of the grid made with the CMY printer.

EPILOG 2016:

The page author has since acquired the following colored LED bulbs:

In addition, the page author's changes to the outputs of these LEDs using filter covers are altered as follows:

When the page author used the illumin8 yellow LED, it is slightly dimmer than the other LED bulbs. But the bandwidth is narrow enough that he could not see differences between red and green for the Red-Green Indistinction setting.

THE PAGE AUTHOR'S 2016 SIMULATOR FOR DEFECTIVE COLOR VISION:

Author Color blind simulator off The page author had the good luck to find another used light bar with 6 sockets, so he built the color-blindness simulator. He used a switchbox (below) and an 8-conductor cable between the switchbox and the lamp. Colored LED bulbs were used.

Author Color blind simulator faked on For some reason, the author's camera will not auto-adjust for brightness with nearly monochromatic lights in the field of view, so it was impossible to take a good photo with any lamps on. The photo had severe halation (scattered light fogging the photo). So the first photo shows the lamps turned off. The second photo is the first photo altered with added color to make the lamps look turned on.

Author Color blind circuit The lamp array contains the following lamps (left to right).

All of these lamps except the Feit Blue have extremely narrow bandwidths. This makes the simulation work quite well. A few objects in the room might look wrong because they reflect a very narrow bandwidth of light. Fortunately, this is not usually the case, and most objects will have the expected color to be seen under these lights.

The page author used the color grids made for the web page The Crayon Trials as sample colors to compare under the simulations of the different color vision defects.

The light bar switching is wired as shown at right.

The switches are wired to quickly show the differences between normal vision and 11 different color vision defects, using only one switch to show the difference in most cases:

Author Color blind circuit The following table shows the switch positions needed for each vision defect. The - means center off:

Defect Case... Normal Vision... Lamps... Defect Simulation... Lamps...
Switch Settings: 123456 ........ ........ ........ 123456 ........ ........ ........
Protanomaly Narrow: -R- G-B -O- G-B
Protanomaly Wide: R-- G-B Y-- G-B
Deuteranomaly Narrow: R-G --B R-Y --B
Deuteranomaly Wide: R-- G-B R-- O-B
Tritanomaly: R-- G-B R-- Y-C
Switch Settings: 123456 ........ ........ ........ 123456 ........ ........ ........
Protanopia: R-- G-B --- G-B
Deuteranopia: R-- G-B R-- --B
Tritanopia: R-- G-B R-- G--
Red-Green Indistinction: R-- G-B Y-- --B
Cone Monochromatism: R-- G-B --- --B
Rod Monochromatism: R-- -G-BB --- -G-BC

This light bar can also be used (in a Normal Vision setting) for the visi-spectrum light.

Why can't color-filtered glasses be used instead of colored lights?

In most of these cases, a filter for the purpose would be hard to make. The FILTER column in the table above shows the cases where a simple filter will work. Simple filters do not work in the other cases.

Most of the cases require either a very sharp notch filter or a very narrow bandpass filter. Those would have to be specially made. They are labeled "Special" in the table. Note that the EnChroma glasses are specially made notch filters.



Appendix: Comparing Colored LED Bulbs

Here are the approximated differences between FEIT and illumin8 colored LEDs:

COLORFEIT LAMPillumin8 LAMP
Red

                                                   

                                                   

Orange

                                                   

                                                   

Yellow

                                                   

                                                   

Green;

                                                   

                                                   

Blue

                                                   

                                                   

 

LINKS