Improvements in Apparatus for Displaying Photographs of Moving Objects.
Year: 1899

page_text: Date of Application, 19th Apr., 1899-Accepted, 22nd July, 1899
COMPLETE SPECIFICATION.
Improvements in Apparatus for Displaying Photographs of
Moving Objects.
I, MARK BARR, of "Rosbrin," Bowdon, in the County of Cheshire, Electrical
Engineer, do hereby declare the nature of this invention and in what manner the
same is to be performed, to be particularly described and ascertained in and by the
following statement :-
Photographs of moving objects taken as a series of successive pictures on a film,
are usually displayed by causing the film to move rapidly the length of one picture
then to stop for a fraction of a second, during which the picture is displayed on a
screen, to move again, and so on intermittently. The very rapid intermission involves
considerable mechanical difficulties and also objectionable vibrations of the images
displayed.
My invention relates to apparatus so arranged that there are no intermittent or
reciprocating movements, but that while the film travels continuously and uniformnly
onwards, the image thrown from it on a screen remain stationary, as I shall describe
referring to the accompanying drawings.
Fig. 1 is a vertical section af apparatus according to my invention.
Fig. 2 is a front view of the revolving screen.
On an axis a caused to revolve rapidly by any convenient motor, such, for instance,
as an electric motor, is fixed an annular mirror b the reflecting surface of which
gradually and uniformly varies in its inclination to the plane of revolution from a
point where its inclination is least round the same point where its inclination is
greatest, and where it suddenly resumes its least inclination. From the axis a by
worm or other convenient gear is driven a pegged roller c by which a film f is drawn
from a reel e across an opening g fronted by a screen d which is geared to and
revolves uniformly with the mirror b.
The revolving screen & has through it an opening bounded by two curved lines
which are segments of archimedean spirals.
A beam of light from any suitable source is directed through the film at the
opening g, through the aperture of the revolving-screen d and after passing through
lenses is reflected from the mirror band directed on a screen.
As the film travels while the light passes through it, the spiral form of the aperture
of d causes a beam of the light to travel with it, and if this were directed through a
But the
projecting lens on to a screen the image would travel along the screen.
travelling beam is received on the mirror the inclination of which is changing as
the beam is travelling and thus the beam is caused to travel in the opposite direction,
the effect being that the image on the screen is stationary.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is
1. Apparatus for displaying photographs of moving objects comprising means of
causing a film having photographs on it to travel uniformly across an opening,
L
tion
allantine

page_text: continuously varying throughout its periphery, a revolving screen having through
it a spiral aperture, and a projecting lens or set of lenses, substantially as
described.
2. The herein described method of causing an image from a travelling picture to be
presented stationary on a screen by reflecting rays from the picture from a revolving
annular mirror the inclination of which changes continuously throughout a revolution
made during the travel of the picture over its own length.
Dated this 19th day of April 1899.
ABEL & IMRAY,
Agents for the Applicant.