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

page_text: Date of Application, 19th Apr., 1899-Accepted, 27th May, 1899
COMPLETE SPECIFICATION.
Improvements in Apparatus for Taking and 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:-
Apparatus hitherto employed for taking and displaying photographs of moving
objects have acted intermittently, that is to say, the film sensitised for receiving
the successive images or the film on which the positives have been printed moves
the length of a picture then rests for a short time, and so on alternately. This
intermittent action, recurring every small fraction of a second, involves consider-
able mechanical difficulties, and certain optical imperfections. My invention
relates to apparatus in which the movement of the film either for receiving or
for displaying successive views of moving objects is uniform and continuous, no
parts of the apparatus having reciprocating or intermittent action.
I shall describe apparatus according to my invention referring to the accom-
panying drawings.
Fig. 1 is a vertical section of the apparatus and Fig. 2 is a front view of the
interior, the front of the casing being supposed to be removed. Fig. 3 is a vertical
section of a modification.
Referring first to Figs. 1 and 2, an axis a caused to revolve rapidly, say 10 to 20
an electric
times per second, by any convenient motor, such for instance as
motor, has fixed on it two equal and similar annular mirrors b and c, their reflecting
faces being helical, that is to say, they gradually and uniformly slope from a
point of the circumference where the face is highest down to the same point where
it is lowest, the pitch or difference between the greatest and least height being
suited as will be presently described to the length of film occupied by each
picture. From the axis a by worm or other suitable gear, is driven a pegged
wheel which, as it revolves draws the film f from a reel e and over suitable
guide pulleys so that it moves continuously always presenting a portion of its
Tength at an opening 9. A beam of converging rays (obtained from any
convenient source) included between the lines hk as it is reflected from the
mirror b, is caused by the rotation of the helical surface of that mirror to travel
across the opening g to a position indicated by the dotted lines hand, the pitch
of the helical surface and the speed of travel of the film having in the first place
been determined in proper relation to each other, the reflected beam travels
along with the image on the film through the opening and also travels along
the reflecting face of the second mirror c. This mirror having its face directed
onposite to the face of would cause a beam reflected from it to travel in the
direction opposite to that in which the beam travels and therefore, this
beam is reflected from c as indicated by without any travel at all, conse-
quently the beam carrying the image from the film, when directed through
suitable lenses i throws a stationary image upon a screen.
So far the apparatus has been described as for displaying pictures from a film.

page_text: For photographing images on a travelling film, the mirror b is dispensed with,
and for the lenses i, suitable for projection, are substituted lenses suitable as
objective.
According to the modification shewn in Fig. 3, the beam h³ ³ is assumed to
consist of parallel rays passing directly through the film at g where every different
point of the travelling image receives a different ray, and therefore, the effect
would be the movement of the image on a screen but for the action of the mirror e
which corrects the movement of the rays, reflecting the beam so as to throw
a stationary image on the screen.
In like manner when the apparatus is employed for photographing, the stationary
object taking the place of the screen image, sends rays through a suitable objec-
tive on to the revolving mirror c which causes those rays to travel along with
the film on which they are therefore virtually stationary.
Having now particularly described and ascertained the nature of this
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. Apparatus for taking photographs on a travelling film comprising means of
causing the film to travel uniformly across an opening, an objective and a
revolving mirror having a helical surface adapted to reflect the rays which pass
through the objective, these rays being caused by the continuous change of
position of the reflecting surface to travel along with the film on which they
are directed, substantially as described.
2. Apparatus for displaying photographs from a travelling film comprising
means of causing the film to travel uniformly, suitable projecting lenses, and two
revolving mirrors having helical surfaces, the one adapted to reflect rays from a
source of light on to the film, these rays being caused by the continuous change
of position of the reflecting surface to travel with and through the film the other
mirror adapted to receive the rays passed through the film and by the continuous
change of position of its reflecting surface to cause these travelling rays when
reflected to pass through the projecting lenses and form a stationary image on
a screen, substantially as described.
3. The modified apparatus for displaying photographs from a travelling film
comprising means of causing the film to travel uniformly, projecting lenses and
a revolving mirror having a helical surface adapted to reflect rays: passed through
the travelling film, which would otherwise seem to travel along a screen, by the
change of position of the reflecting surface to pass through the projecting
lens so as to render the image on the screen stationary, substantially as described.
4. The herein described method of causing rays to travel laterally or of
neutralising the motion of laterally travelling rays by reflecting them from a
revolving helical surface.
Dated this 19th dor of An;1 1900
ABEL & IMRAY,
Agents for 'the Applicant.