We chose the projection by transparency
to leave all the place available in front of the screen on the user.
This by the fact that the screen is small.
By throwing(planning) of highly-rated convex of the screen, it is not any more necessary question to use a fish-eye lens.
Thus considerable economy and simplification: we do not touch the video-projector.
It against part(party) we are going to face the difficulties of an unusual projection:
problems of settling, will the depth of field be sufficient(self-important)?
The curvature of the screen deforms strongly the image on edges.
As there is no objective capable of setting of such embellish with images, it is necessary either to make of the computer generated image,
or to transform photos fish-eye lens by means of a computer.
A computer is thus always indispensable.
A priori the ideal screen is a half-sphere.
But with the aim of reducing the deformations as well as the problems of settling,
we thought at first of using a spherical applatie calote rather than a half-sphere.
This first version, although in theory valid, showed itself catastrophic for the definition of the image.
The image is better defined on the edges there than in the centre.
The second version, the one who is at present retained, uses a true half-sphere.
She(It) favors the centre of the image, to the detriment of edges. The settling becomes a criticism on edges,
the depth of field necessaire being more important than in the first version.
But this depth of field is obtained diaphragment the projector there at most;
what is possible because we have a lot of light.
Philosophically the image is similar to the one that supplied the eye: net in the centre, swindle on edges.
On a screen Panrama, if we regerde on the highly-rated, the image remains net, fields is uniform. The eye is free to walk in the image.
Here it is not any more the case. There is a priviliégé glance: opposite.
Two types of ecrans are possible:
Post COMPANIME with SPHERICAL screen first version
© COMPANIME 2004
The manufacture of a translucent or transparent spherical dome seems to me out of reach of an amateur.
It is necessary is to find her(it) in the business, intended for the other applications:
dome of roof SIH
Is to make her(it) make:
produced Pascal Rosier
Post COMPANIME with CYLINDRICAL screen
© COMPANIME 2004
© COMPANIME 2004
It is necessary to find a quality of screen adapted to this type of projection and which agrees to bend cylindriquement.
A) Paper traces. Cheap. Too supple(flexible) to do without support.
B) Type plexiglas translucent. Very practical. Leash transparaitre the light of the projector. Impossible to have a precise point because of the thickness.
C) Type plexiglas transparent. Very practical. A coat(layer) screen Necessite: frosted(textured) face? Painting? Paper traces?
D) Special screen projection by the back: the catalog ORAY proposes a supple(flexible) translucent surface, enroulable or tense, of 0,3mm of thickness, dark gray for more contrast, in 23€ m2.
(Code article TOIO1T1100100 page 15). This screen is for the moment the most promising. He(it) seems rather stiff to do without support plexiglas and can roll about for the arrangement. { ORAY}
Thus, on the condition of arranging a video-projector and a computer, having enough know-how in data processing and in do-it-yourself, the projection on cylindrical screen is easily accessible(approachable) to very cheap.
The choice of the screen being decided, remains to define the complete set(group).