An Improved Apparatus for Executing Drawings by Means of a Camera Lucida
Year: 1892

page_text: Date of Application, 6th Oct., 1892-Accepted, 12th Nov., 1892
COMPLETE SPECIFICATION.
An Improved Apparatus for Executing Drawings by Means of a
Camera Lucida."
6
I CHRISTEN REES BONNE of 57-8 Chancery Lane London W.C. Patent Agent
(communicated to me from abroad by Heinrich Eppers of 43 Bohlweg, Brunswick
in the Empire of Germany, Optician) 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 :-
The object of the present invention is a new camera lucida destined for practical
purposes and by which a picture of an object may be caused to appear on a surface
and thus copied.
In the drawings herewith
Fig. 1. is a complete view of the instrument for copying landscapes and other
large originals.
Fig. 2 is a side view of same, except the part C which is shewn enlarged and in
section.
Figs. 3 to 11 are variations and details.
The camera lucida according to my invention consists in the main of the drawing
board A, the support B for placing the subject upon which is to be copied, such
support being attached to the drawing board A by means of brackets d d¹ and
screws e e¹, the camera C or C', which is connected with A by means of rod c and
rod which is turnable on a centre a the arrangement being such that the relative
positions of A, B & C to each other do not alter when once fixed and the instrument
is in use.
Throughout all the figures identical parts are designated by identical letters.
The camera C consists essentially of the two plane mirrors x and y (Fig. 2.)
which are mounted in a suitable frame with an eyehole. The angle at which these
mirrors are placed relatively to each other (in the drawing about 30 degrees) is
half the angle of A to B. The mirror may be either a metal one or a silvered, or
platinised or otherwise suitably prepared glass plate, but mirror y is prepared in
such a manner that it partly reflects and partly lets light through; it may for
instance be prepared by removing in places the metallic coating of a glass plate as
shewn by y (Fig. 2) in which the black lines indicate the transparent parts while
the white portions are reflecting. An observation of Fig. 2 will show that an
eye o placed near the eyehole will see the picture m placed on B reflected as n
on A but simultaneously other objects for instance the hand with drawing pencil
may also be seen on account of the peculiar construction of the mirror y, as
explained. The subjective picture n may therefore easily be traced off.
When it is purported to project a reversed picture of the original, then mirror c
is unnecessary and y (Fig. 3) is placed in such a manner that it halves the angle
between A and B. An observation of Fig. 3. (which as in (Fig. 2) shews parts A,
B, d and b in side view and camera C¹ enlarged and in section) will shew that
the eye o at the eyehole of the camera sees the original at B reversed at n on A
and, as before, the peculiar construction of mirror y permits other objects, for
instance the hand and pencil to be seen.
The subjective picture may thus be easily copied.
In projecting landscapes and larger objects parts A and B may be folded as
shewn in Fig. 4 and the apparatus may be mounted on a tripod or other suitable
stand z. Fig. 4 explains how the landscape or object m will be projected at n.
In Figs. 5, 6, 7 and 8 is shewn the manner in which the camera lucida,
according to my invention, may be constructed, especially with a view to its use
for projecting landscapes and small objects and consists essentially of the drawing
board A', the holder B' and the camera C or C' respectively. The connection

page_text: за
between the 3 parts is established by means of 3 rods r, s and t turnable on a
common centre a³ (Fig. 5). Rod is connected with A' by means of a screw a',
rod with B¹ by means of screw i and rod t with camera C or C¹ by some suitable
means, the parts being fitted and disposed in such a manner that during the
operation the parts do not alter their positions relatively to each other.
Figs. 6, 7 & 8 which are side views while Fig. 5 is a front view, shew the
various angles at which the parts may be placed relatively to each other. In
Fig. 8, levers ordinarily carrying the holder is shewn in a position at which it
may be supported against the shoulder of the operator who otherwise holds the
instrument in the left hand, while the sketch book E may be placed on the
board A. This arrangement is especially useful for landscape copying, the land-
scape being represented by the arrow m.
It is obvious that when the distance from the object m to the camera is equal to
the distance from the camera to the drawing board, the projection will be the
natural size and that accordingly as these distances are altered the projection will
be either an enlargement or a reduction of the original object.
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In order now to be able to determine whether the apparatus hereinafter called
Dikatopter," is properly arranged and also in order to be able to determine the
proportionate size of the projection relatively to the original I cause certain
markings to be made on the boards A and B or A' and B' respectively, as shewn
in Figs. 9 and 10. These markings take the form of parallel lines. The centre
lines on B and I on A are square with the eyehole of the camera. Lines 2 and 3
respectively are equidistant from the centre line I, and so are lines II and III
from I, lines 3 and III being also equidistant, relatively to each other from the
centre.
The distance of lines 2 from the centre line is arranged at two thirds the distance
of lines II from their centre line.
When therefore the apparatus is properly set up, the eye should see the centre
lines 1 and I as true continuations of each other, and when the distances between
camera and projection are equal then the lines 3 should appear as true continuations
of lines III and in that case the projection will be the natural size of the original.
When on the other hand lines 2 appear as true continuations of lines III then the
distance between camera and original is three times less than the distance between
camera and projection-and the original must therefore be just three times larger
than the projection.
In projecting landscapes and large objects the lines of perpendicular objects,
such as for instance buildings should be parallel with the lines on the board or a
skellet as in Fig. 4, may be used to obtain a true perpendicular.
In Figs. 11 and 12 is shewn in plan how the Dikatopter may be folded the
hollow produced between the two boards being utilised for storing materials camera
and the like.
Having now particularly described and ascertained the nature of my invention
and in which manner it may be performed I declare that what I claim is :
.1. An improved apparatus, called " Dikatopter," for executing drawings by
means of a camera lucida constructed and disposed substantially in the manner
described and shewn in the drawings.
2. In such apparatus the means for proving the accuracy of the relative positions
of the various parts to each other and for determining the size proportions of
original and projection to each other, consisting in a system of parallel lines marked
and arranged substantially as described.
Dated this 6th dox of Datakon 1909
BONNE & Co.,
57-8, Chancery Lane, W.C.,
Authorised Patent and Trade Mark Agents.