Colourblind Simulation Lamp (DaltonicLamp)

This instructable explains how to create a light source that simulates different types of colorblindness when viewing objects under its light. It works due to the fact that the colour of an object is determined as a product of its spectral reflectivity (what wavelengths are reflected) as well as ambient wavelengths of light (wavelengths in the light source); that is an object can only reflect the light that is shined on it.

As such, if no red light is incident on a red object, it will no longer appear red, This means that colour vision defects can be simulated by carefully choosing the spectral composition (wavelengths) of the illuminant light.

Full Article: https://www.techrxiv.org/articles/preprint/Effect_of_Illuminant_on_Colour_Perception_Concerning_the_Simulation_of_Colour_Deficiencies/19123046?file=33975851

The concept is very simple - please do not be alarmed by the complex theory and explanations: these are just to give some background. Feel free to skip if it is too much.

For Supplies, you'll need pure colour LEDs (i.e. single colour not white or magenta) and a way to power them. This instructable will explain how to choose the LEDs and suggest suitable ways of powering them. These can be obtained from futureeden and other places.

3W LEDs can be powered with a simple battery without overheating, however, if you want a proper device, you may want to invest in heatsinks and constant current sources.

https://futureeden.co.uk/

Typical human colour vision is trichromatic (tri - three, chromatic - colour) meaning that three primary colours (think RGB) are necessary to recreate all visible colours and that typical colour vision can be thought of as three dimensional. It also means that the human eye has 3 types of light sensitive "cone cells", each of which is sensitive to approximately red, green and blue.

In the case of colour deficiencies, there is mainly anomalous trichromacy (i.e. protanomaly) and dichromacy (protanopia). Red-Green colour deficiencies are far more common because red-green vision is quite new in our evolutionary history. Blue-yellow colour deficiency and monochromacy(black and white vision) also exist but these are much rarer.

Red-green anomalous trichromacies are by far the most common (around 6% of men) and occur when either the '"red cone" detects too much green light (protanomaly), and the "green cone" detects too much red light (deuteranomaly). The result is a decreased colour gamut, however, in many cases, it is quite mild and only specific shades are affected. The affected person simply sees some colours in less contrast, will probably fail colorblind tests but rarely confuses colours in everyday life. In more severe cases, the affected person will confuse some colours such as reds with browns, blues with purples, or greens and oranges.

Dichromacies occur when a person lacks a gene for producing one type of photopigment and only has two functioning cones. This means that their colour vision is reduced to two dimensions and they only require two primary colours to recreate any colour that they can perceive. See*

In the case of red-green deficiencies (protanopia and deuteranopia), the person will only see the world in yellows/yellowish-greens, blues, and browns. As such red, orange, yellow and green (every colour from red to cyan) and will be a shade of yellow and blue and purple (every colour from cyan to magenta) will be a shade of blue. Cyan on the other hand will be perceived as grey due to equal activation of their two cone cells.

See this video for a quick explaination: https://www.youtube.com/watch?v=iNRQB5309yo&ab_channel=HumanInterests

Image above is a derivative work of public domain image (credit: Christopher S. Baird): https://wtamu.edu/~cbaird/sq/2012/12/04/why-are-th...

The lamp works by choosing a limited number of wavelengths to illuminate objects. This means that only a limited number of colours can be perceived which can be representative of the colour vision of people with colour deficiencies.

For Protanopia: a condition where a person only has green and blue cones can be simulated with pure green and blue light. In the case of a person with normal vision, only their green and blue cones will be activated under such a set up thus simulating a situation where only green and blue cones are present - protanopia.

For Deuteranopia: pure yellow and blue lights are chosen, simulating a situation where a person only has red (L) and blue (S) cones - it should be noted that the 'red' cones are more sensitive towards the yellow wavelengths, and are only called 'red' only because they can detect red when working together with the green cones.

For Tritanopia: a condition where only red and green cones are present, can be simulated with pure red and cyan lights.

For Monochromacy use only pure cyan light - this is the wavelength most detected by rod cells and simulates what is like to just perceive colour with rods. It should be noted that having just rods leads to other problems, such as diminished visual acuity and photophobia.

Anomalous Trichromacies are more difficult to simulate but varying the light intensity (i.e. small amount of red) or using wavelengths closer to yellow, such as orange, chartreuse/green, and blue LEDs should be able to simulate mild-moderate red-green colour deficiencies. For tritanomaly, try cyan, green and red.

(Diagram above: normal vision with 2 wavelengths (green and blue) is equivalent to protanopia with full-spectrum illumination)*

Modified from: https://commons.wikimedia.org/wiki/File:Cone-response-en.svg, Credit: TAKASUGI Shinji

The number of wavelengths to choose works like this:

Anomalous Trichromacies: three wavelengths but some/one is dimmer (red green blue where red is dimmer or green and blue where green has a phosphor - some red is present)

Dichromacies - two wavelengths (yellow ~570nm and blue ~440nm, green ~525nm and blue ~440nm or red ~635nm and cyan ~495nm )

Monochromacy (one wavelength - cyan)

Power and Size

The lamp can be anywhere from pocket-sized (battery-powered) to large enough to illuminate an entire room (2 50W LEDs heat sinks and mains connection).

Important:

-For dichromacy and monochromacy the LED wavelengths used must be pure, if a phosphor is present, fluorescence will occur and the LED will give off other wavelengths. Fluorescent objects will also not change colour under the lamp's light.

-You can use a marker pen or light filter to purify the light of the lamp and remove the effect of any phosphor.

-You can use a CD as a diffraction grating to analyse the spectral composition of your lights.

-There must be no other light source for the lamp to work at its best.

-Although yellow LEDs are more ideal for simulating full red-green colour deficiency, they are more difficult to come by than green ones and are more likely to emit additional red and green wavelengths. Instead, it is better to go with the standard green LED (525nm) which is already slightly yellower.

You may be tempted to ask a colourblind person to describe what they see under the lamp and you will be surprised to see that they will see a difference.

The image above is an approximation of what could happen when both a colour blind and normal colour sighted person looks at objects under the lamp. For normal colour vision, the 3 dimensional colour space is reduced to 2 dimensions. However for a protanope with 2 colour dimensions in their colour vision will also experience a change, but only a brightness intensity of colours.

Please note that, although the transformations appear rather cyan, without a good white balance, your eyes will naturally adjust for this and the environment will appear with proper white balance. This is a camera problem!

Image credit alexraths from: https://www.gettyimages.in/detail/photo/assortment-of-colorful-ripe-tropical-fruits-top-royalty-free-image/995518546?adppopup=true

The images shown above are taken under normal light and the Red-Green Deficiency simulator lamp (Protan - Green and Blue LED) As you can see the colours are strongly desaturated and all become shades of yellow and blue under the simulator lamp.

This is because only 2 wavelengths are emitted from the lamp and only 2 wavelengths can stimulate your cone cells in your eyes in only 2 ways. This effectively makes you perceive light as if you only had two types of colour receptors in your eyes.

Original Images - 3 images taken with the familiar normal colour spectrum

Lacking Red (L) Cones - only two main colours are present - those being yellowish-green and blue. Red and green are just shades of the same colour and red is now much darker. This is an imperfection in the lamp, as reds will not be that dark to protanopes under normal light because their green (M) cones still pick up a bit of red light, adding to the brightness of red.

Note that the blue wires have become rather desaturated - this is an imperfection in the simulation. Blue is virtually unchanged for protanopes.

Lacking Green (M) cones - only two main colours are visible on the spectrum - that is yellow and blue (the faint red is caused by imperfections in the yellow LED light). Notice how the difference between red and green is near non-exisitent and the 74 on the colour blind test is now more of a 21.

Tritanopia is characterised by lacking Blue (S) cones - two colours are visible - red and cyan, and the distinction between green and blue is largely diminished, and red and pink are difficult to distinguish.

Red-Green colourblind tests appear unchanged as the red-green dimension is unchanged.

Only Rods - this is an approximation of the colours rod monochromats will see. Notice how everything is a shade of one colour.

This simulation does not show the decreased visual acuity and light sensitivity associated with only having rod cells in your retina and the fact that a monochromat will perceive in shades of grey, and not cyan.

Coming Soon

LED wavelengths and intensities could also be adjusted to aid the colour deficient in distinguishing colours. Adding in a slightly brighter red light could increase colour saturation of red and would make reds appear bright making them easier to distinguish from greens. Additionally, a slightly pulsating red light could help reveal colour distinctions without distorting the overall image.

Colours can also be enhanced using pure red green and blue lights with slightly brighter red light. This works in a similar way to the famous Enchroma Glasses - both cases are characterised by the lack of orange-yellow and cyan wavelengths which lie on the overlap of a colour deficient person's cone cells. Removing these colours will give a purer spectrum of light and thus better colours (i.e. red objects still reflect a bit of yellow and orange and removing it will give purer red).

Coming Soon