05_04_06

I took the fan screen apparatus outside into the sunshine today...

The main problem with the setup as it stands is the amount of reflected, ambient light, that is reaching the fan screen. Ideally, only light through the lense would be caught by the screen and all other, ambient light would be shaded. At present I'm using an old t-shirt to shade it, a properly designed blackout curtain is needed.

An explaination of what this apparatus does can be found here

03_04_06

The first version of the fan screen apparatus is almost finished. It's made up of a the phase elements, a motor taken from a fan and a laser cut 'fan screen'. Hopefully all will become clear in the jpegs below and on the right.

The effect was not as i expected. However, i should have learnt by now to never expect what i am initially expectin! Th effect was quite subtle with only a small amount of 'fire' or dispersion of the light into the spectrum. The observation position is very important, it can look both stunning and boring depending on where you put your eye.

A short video and pictures of the apparatus in use are posted on the right.

Images, alongside explanations of the apparatus, are posted below

The idea with this apparatus, was to create a three dimensional screen using the spinning blades pictured above. The machine is designed for sunlight. As the sun moves across the sky, the sunlight is refracted by the phase screen in differing ways depending on the time of year and day. The apparatus has an orientation north-south so that it can be viewed without obstruction from the north and so that the sun is never shaded from any position on it's path through the sky to the south.

Sunlight enters through the lens at the top which focuses it through the phase screen and onto the fan screen. The fan screen is designed to be observed from the north side looking up from below. The circular top shades the light so only sunlight through the lense hits the fan screen.

Any feedback is welcome: nick@lightmodulator.org

22_03_06

Some elements from the cadcamed phase screen are shown on the right along with some computer renders of the virtual model.
The three forms shown here are the central shapes in the array. The shape of the array is taken from London's sunpath and the forms are created to refract and disperse the sunlight in differing ways throughout the sun's 6 month cycle.

Images of the water filled phase screen are below. This refracts light through a water filled PVC bag which can be squeezed and stretched to change the projected caustics.

I need to make a decision on which phase screen to use for my final model as well as the scaling of these elements. I also need to make a firm decision on the required effect...

As well as these phase screen elements I am also prototyping a spinning screen (a fanscreen) which catches the light from the phase screen. Working on the metal lathe is proving to be harder than I first thought as the attachment for the motor needs to be perfect or the screen will wobble. Pictures to come...

Images of the phase screen elements in their raw state before sanding and polishing...

20mm thick acrylic block after milling	The block was milled on both sides to create the shapes

19_03_06

At the moment I am dealing with sunlight, taking information from my sun studies and visualisations earlier in the year. Whilst the design is primarily for sunlight, an artificial source will also be accounted for in the design. This will allow me to demonstrate the effect when the sun's not out.

The current proposal works in a similar way to a spectroscope which is designed to split light into its constituent colours. This setup is also similar to the coma maker where light from the source passes through a grid of 1-2mm slots and then through a lense. In this case, the light will pass through a grid, a lense and then a phase screen before being 'caught' on the screen. Using this setup the light should create a distorted image of the source which will change with the path of the sun.

04_04_06 New photos of the trace screen in use are posted below.

Screen

Recently, I have been concerned with the projection surface. Ideas have included spinning oil in a saucepan to create the hemisphere shape that the sunpath takes. While this creates a highly reflective and distorted surface it is too reflective to display specular or direct sunlight but does image its environment wonderfully, sucking the image into a vortex. See Atilia Csorgo's work for more information.

Following on from the mist camera experiment where I tried to create a 3d screen to create an image, I designed a translucent waffle screen to catch sunlight focused through a lense. The first iteration failed as tracing paper doesn't have the rigidity needed, a trip to the London Graphic Centre for some frosted polypropylene sheet solved the problem. The polypropylene was laser cut from sectioning a virtual model and laying out the sections. Results posted above...

I'm planning to make a cross between a fan and a flick book to create a hovering caustic as the next iteration of the 3d screen. initial test with a motor, a piece of paper and a lense have proved successful so watch this space.

Phase Screen

The central element of the apparatus I'm proposing is the 'phase screen'. The name is taken from J.F. Nye's description of a refracting and reflecting surface (eg swimming pool surface) in his book; Natural focusing and fine structure of light : caustics and wave dislocations.

I am planning to create a medium which will create a unique caustic for the time of the day and year. Another take is to use the phase screen as an interactive mechanism so that observers motion can be used to change the phase screen's form and thus the image projected onto the screen.

These two possibilities give rise to two versions of the phase screen. The first, sunlight specific screen could be machined from acrylic in the same way as the first water prisms. The second could be as the image on the right of the pvc water bag which is two films of transparent PVC with bolts attached to stretch the surface clamped together and filled with a liquid.