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OXP-15 Colour Mixing

  Topics:
Primary / Secondary Colour
Additive / Subtractive Colour Mixing
Absorbance
Transmissivity

James Clerk Maxwell
1831 – 1879

 


In the 1850s and 1860s James Clerk Maxwell investigated the nature of colour and colour vision. He used a simple but very efficient tool to demonstrate colour mixing. With a spinning disc divided in sectors of red, green and blue, he performed mixing of primary colours into a manifold of other colours. Additionally, Maxwell demonstrated the photographic reproduction of colour images, using a three-colour process, where scenes are first photographed, and then projected using red, green, and blue filters.
All methods of colour reproduction are based on colour mixing: paintings, printing, coloured photographs and coloured television. However, different types of colour mixing obey basically different rules of mixing. In principle one can distinguish between mixing of dyes or pigments which is called subtractive mixing, and the mixing of colour light, which is called additive mixing.
The experiment “Colour Mixing” gives examples of additive colour mixing based on Maxwells demonstrations. A set-up is built for investigations on the superposition of three colours, provided by three colour LEDs. An insight is given in subtractive mixing by an experiment of colour filter combination.



 

 


 

Examples of Investigation and Measurement


Additive colour mixing
First the light of three LEDs emitting different colours is superimposed on a screen. By changing the intensity of the sources a huge variety of colours can be generated. In the next step a grey scale mask is inserted in front of each LED. The spatially filtered beams are overlaid on the screen and generate a colour image.


Subtractive colour mixing
An arrangement of two or more colour filters in combination demonstrates the principle of subtractive colour mixing. By use of a diffraction grating the resulting colour can be spectrally resolved.

 

 

 

 

OXP-15   Required Equipment


3
1
 


02.0300
02.0500
 

 


Profile rail OCM 650, 3*00 mm
Profile rail OCM 650, 500 mm

The high precision optical rails are made out of special anodized aluminum. The rails are the base for various modules attached to carriers.
 




 
1 02.1022

 

Carrier OCM 650, 20 mm with screen holder

This module can mount optical screens. Through the attached carrier, the screen holder can be placed onto the optical rail. The carrier 20 mm and the holder are made out of special anodized aluminum.
 

3

02.1024

 

Carrier OCM 650, 20 mm with attached plate holder

Using a spring loaded blade 50 x 50 mm, plates like filters or gratings can be fixed onto this module. The carrier allows the direct attachment to the optical rail. The carrier 20 mm and the holder are made out of special anodized aluminum.

1 02.1601

Screen

Experimental results like colour spectra and interference patterns can be visualized on these screens. Horizontal or vertical scales allow calibrations and quantitative measurements; a screen with an aperture is used for observing back-reflected rays. The screens are made out of anodized aluminum plates with one side painted white and can be fixed onto screen holders (02.1022, 02.1608).
 

3
1
02.2132
02.2150

Mounting plate OCM 650 for click 30, including carrier 20 mm
Mounting plate OCM 650 for click 50, including carrier 20 mm

Mounting plates are used to hold optical mounts. A characteristic feature of the mounting plates is the “click” mechanism of the inserts based on spring loaded spheres. Snapping in the groove of the inserted click mount, the optical element is kept in an exact position. On the other hand, the system allows a quick and easy change of the mounted inserts.
The mounting plates are made out of special anodized aluminum. Mounted onto the carrier 20 mm, the mounting plates can be placed onto an optical rail.
 

1 02.2202

Filter plate holder FH 650, for 3 filters 50 x 50 x 3 mm, including carrier 30 mm

The holder can support a total of three filter plates with the dimension 50 x 50 mm. The maximum thickness of the filters can be 5 mm. Lateral springs fix the filters within the holder. The holder and the carrier 30 mm are made out of special anodized aluminum and can be placed onto an optical rail.

3

02.6106

4 axis adjustment holder KH650, theta, phi, X and Y, including carrier 20 mm

This adjustment holder mounts a Diode Laser or an LED lamp. Using the fine pitch adjustment screws, the optical axis can be aligned within the range of 3 mm. For fine alignment of the angle of the light beam, two additional pitch adjustment screws are attached onto the back of the holder. The holder and the carrier 20 mm are made out of special anodized aluminum and can be placed onto an optical rail.
 

1 04.0054

Biconvex lens f=150 mm, mounted on click 50 mount

Different glass lenses are mounted onto a special anodized aluminum click mount 50 mm by two threaded mounting rings to be used in connection with a mounting plate (02.2150).
 


No illustration

3
1
 
04.0060
04.0062

Plano convex lens f=40, mounted in click 30 mount
Plano convex lens f=60 mm, mounted in click 30 mount

Different glass lenses are mounted onto a special anodized aluminum click mount 30 mm by two threaded mounting rings to be used in connection with a mounting plate (02.2132).
 

1 04.0190

Set of five optical filters

This set of filters comprises of one high- , one low-, one band-pass filter and two band-block filters and can be fixed onto a plate holder (02.1024).
Dim:
50 mm x 50 mm x 3 mm
 

1 04.0702

Optical grating, 600 lines / mm

This optical grating copy mounted between two glass plates is used for generating a spectrum of the investigated light.
The frame has a size of 50 mm x 50 mm x 2,5 mm and the grating window is 35 mm x 24 mm large.
 

1 04.0810

Set of four slides

The superposition of three coloured beams filtered by three black and white masks results in a colour picture. The fourth mask is a colour slide used for filtering out different colours.
All slides have frame sizes of 50 mm x 50 mm x 3 mm and the slide windows are 20 mm x 20 mm large.
 

1
1
1
1
05.0030
05.0032
05.0036
05.0038

LED white in housing
LED red in housing
LED green in housing
LED blue in housing

As universal and easy-to-change light sources, LED lamps are used in optical experiments. The LEDs are mounted onto a 40 mm x 25 mm diameter housing tube made out of special anodized aluminum. For the alignment, the lamps can be fixed onto a four axis adjustment holder mounted onto a carrier. For their operation, the active LDD-05 power supply (07.0206) is required which controls the output power. For the lamps 1 W (white LED: 3W), high brightness LEDs are used.
 

3 07.0206

LDD-05 active power supply

The universal LDD-05 active power supply is used for all laser and LED light sources. It recognizes which source is connected and sets the parameters for it automatically. The unit is equipped with a main switch, a regulation knob for adjusting the laser or LED power and a safety lock. The provided USB bus interface allows control through a personal computer or laptop and qualifies this unit as multimedia source.
The housing is made out of shock-proof plastic with an aluminum front and rear panel.

Voltage: 230 VAC / 50 Hz
Case dimensions: 200 mm x 160 mm x 62 mm.
 




1 09.2510 Angle joint mount OCM 650 cross-piece, modified with dichroic plates

By combining three optical paths, this unit can connect four optical rails and is equipped with two dichroic beamsplitter plates mounted onto rotatable posts.




 


 


 




 

 

Experiments

OXP-01 Refraction of Light

OXP-02 Prisms

OXP-03 Lenses

OXP-04 Reflection & Transmission

OXP-05 Beam Bending

OXP-06 Refractometer

OXP-07 Diffraction of Light

OXP-08 Optical Gratings

OXP-09 Spectral Analysis

OXP-10 Interference

OXP-11 Interferometer

OXP-12 Holography

OXP-13 Polarisation

OXP-14 Double Refraction

OXP-15 Colour Mixing

OXP-16 Optical Filters

OXP-17 Absorption & Emission

OXP-18 Image Projection

OXP-19 Camera

OXP-20 LED & Laser Diode

 

Kits

Basic Kit

Complete Kit

Advanced Kit