An Improved Instrument for Use in Making Perspective and other Drawings.
Year: 1893

page_text: Date of Application, 16th.June, 1893
Complete Specification Left, 15th Mar., 1894-Accepted, 21st Apr., 1894
PROVISIONAL SPECIFICATION.
An Improved Instrument for Use in Making Perspective and other
Drawings.
I, LEOPOLD DIETMANN, commonly known as LEO DIET, of No. 14, Rothen-
sterngasse, Vienna II, in the Empire of Austro-Hungary, Painter, do hereby declare
the nature of this invention to be as follows:-
The object of this invention is to provide an instrument termed a "perspective-
ruler," whereby a plan and elevation of any object may be converted into a
perspective view without resorting to mathematical construction.
The said invention will be clearly understood by reference to the accompanying
drawings, in which
Figure 1 is a plan, ánd
;
Figure 2 a front view of the instrument arranged for use upon horizontal drawing-
boards.
.
Figures 3 &
are, respectively, a side elevation and a plan showing a modified
arrangement for determining the visual point or point of sight, in cases where the
drawing-board is in a vertical position.
The instrument consists of a ruler A movable both in the longitudinal direction
and in a direction at right angles thereto, on parallel lines only; to this ruler A is
rigidly attached a perpendicular ruler A¹ provided with graduations or divisiou
lines. Against this second ruler A' is placed a protractor B capable of being
moved or adjusted along the said ruler, and of being fixed in any desired position
by means of a set-screw a'. To the centre of the protractor B are pivoted two
rulers C, C¹ rigidly connected at right angles to each other, and adapted to be
secured in any required position by means of a set-screw b', which at the same time
secures in place, against the protractor, an index or pointer C' which is an
extension of the ruler C. The ruler A carries, at a, the fixed pivot of a panto-
graph Ss, the terminal points q and b of which are fitted with marking pencils or
styles.
The style or marker q at the end of the larger parallelogram, which, as will
presently be explained, is intended invariably to retain its position, may, in the
case of a horizontal drawing-board, be maintained in place by a weight Q. Where
the drawing-board is vertical, a bar E may be provided, which is adjustable and
which, by means of a set-screw d', may be fixed in any desired position in a block
or clamp D, capable of being tightly secured to the board by means of a screw d.
In the forked end é of the said bar E is mounted a style or marker q'.
The theory of operation of the instrument, and the manner in which it is to be
employed, are illustrated in Figure 5.
The pencil or style 7, at the end of the larger parallelogram of the pantograph,
is brought to what is intended to be the visual point or point of sight of the
perspective view to be drawn, while the ruler A is fixed, so as to be parallel to the
horizon Fq F¹.
Assuming the problem to be, to draw a straight line from a given point of the
perspective, which line should form a predetermined angle g F O with the plane of
the picture, and itself lie in a plane parallel to that determined by the eye of the
observer and the horizon F F¹:
The ruler C is first so adjusted as to form an angle equal to q FO with the
ruler A (for which purpose the protractor 13 is used). The instrument is then
moved until the style b, at the end of the smaller parallelograms of the pantograph,
coincides with the given point of the perspective image; the other style. 9,

page_text: however, remaining stationary, and the ruler A remaining parallel to the
horizon F F¹. Now the straight line drawn from the point to the vanishing
point F, will not pass through the point of intersection c of the two rulers C and A
(i.e. supposing the position of the pivot-points and a, on the inner edge of the
ruler A, to be as shown in Figures 1 and 2) unless the following ratios are 5
obtained :-
gb : a b = F q: ca;
The distance between the two points.a and a must therefore be so determined as
to be in the same relation to the visual distance, as the sum of diagonals of the
large and small parallelograms of the pantograph is to the diagonal of the small
parallelogram. When the distance has thus been adjusted, the point of intersection c
will be situated on the straight line drawn from the point b to the vanishing point.
It will therefore be sufficient to mark the said point c and draw the line bc, to
solve the problem as stated above; and b c¹ will, as a matter of course, be the
perspective image of the perpendicular constructed on 6 c.
Should it be desired to cut the straight line bc at a certain distance, the ruler C
is so adjusted that, in conjunction with the ruler A, it forms an angle equal
to FO. A line 6 6* is then drawn parallel to the ruler A, a given distance
being measured off in the required direction (according to the amount of correction
necessitated by the position of the point b relatively to the plane of the picture)
whereby the point * is reached. The style 6 is next placed at b*; the point of
intersection of the ruler C₁* with the ruler A is marked off; and the straight
line is drawn, which, as will be readily seen, passes through the point of
intersection T. The intersection t of this line b* c* with the line bc then gives the
required perspective image of the terminal point &*.
A* CC here designate the same parts as do the corresponding letters
without the asterisk in Figure 1, when these parts occupy the positions conducive
to the solution of the second problem.
From the foregoing description, any person skilled in the art of perspective
drawing will readily understand the manner in which the instrument should be
handled in a given case.
The same instrument will prove serviceable in working out the problem, above
stated, inversely, that is to say, in constructing a plan and elevation from a given
perspective view. For this purpose, it is only necessary to find, by construction or
conjecture, the visual point or point of sight and horizon for the two main lines of
the image which lines extend at right angles to each other in the same plane.
7
Let the point be q, and the horizon line, for the lines b c and b' c', as at F
Figure 5. The style is placed at the visual point, and the style 6 at the point of
intersection of the two lines bc and bc; the ruler A is made parallel to the
horizon, and the two rulers C C¹ are turned and shifted until they pass through the
points of intersection c c' of the ruler A with the lines bc and ; the styles
and b, however, remaining at rest in the meantime. The distance between a and .
will then be the visual distance, while the angles ac a and c c' a give the degree of
inclination of the two straight lines to the plane of the picture.
The point is determined on the ruler A by tightening the screw a'. If it be
desired to determine the exact length of part of the line be, say the distance C C₁,
the ruler C is placed in such a position as to include between it and the ruler A
an angle equal to ca; whereupon the style 6 is moved in a straight-line

page_text: parallel to the horizon (q remaining stationary and A parallel to the horizon) until
a straight line (6* c*, Figure 5) passing through the intersection of C¹ and A,
and through the point 6 intersects the line b c at t. It will be understood that the
distance b b Figure 5, thus found, requires correcting, in accordance with the
position of the point 6 in relation to the plane of the image.
When the distance ar is found for a given perspective view in the manner above
stated, it is only necessary, in order to determine the angle of inclination of a line
to the plane of the picture, to place the style b at any point of such line, and then
to turn the rulers C C₁ about until one of them passes through the point of
intersection of the said line with the ruler A. The angle which the ruler C or C³,
then forms with the ruler A, gives the required angle of inclination.
Dated the 16th day of June 1893
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.
COMPLETE SPECIFICATION.
An Improved Instrument for Use in Making Perspective and other
Drawings,
1, LEOPOLD DIETMANN, commonly known as LEO DIET, of No. 14, Rothen-
sterngasse, Vienna II, in the Empire of Austro-Hungary, Painter, 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 this invention is to provide an instrument termed a perspective-
ruler," whereby a plan and elevation of any object may be converted into a
perspective view without resorting to mathematical construction.
The said invention will be clearly understood by reference to the drawings
accompanying my Provisional Specification, in which
Figure 1 is a plan, and
Figure 2 a front view of the instrument arranged for use upon horizontal drawing-
boards.
Figures 3 and 4 are, respectively, a side elevation and a plan showing a modified
arrangement for determining the visual point or point of sight, in cases where the
drawing-board is in a vertical position.
The instrument consists of a ruler A movable both in the longitudinal direction
and in a direction at right angles thereto, on parallel lines only; to this ruler A is
rigidly attached a perpendicular ruler A' provided with graduations or division
lines. Against this second ruler A' is placed a protractor B capable of being
moved or adjusted along the said ruler and of being fixed in any desired position by
means of a set-screw a¹. To the centre of the protractor B are pivoted two
rulers C, C¹ rigidly connected at right angles to each other, and adapted to be
secured in any required position by means of a set-screw 6' which at the same time
secures in place, against the protractor, an index or pointer C³, which is an
extension of the ruler C. The ruler A carries, at a, the fixed pivot of a
pantograph S s, the terminal points 7 and 6 of which are fitted with marking pencils
or styles.
The style or marker g at the end of the larger parallelogram, which, as will
presently be explained, is intended invariably to retain its position, may, in the case
of a horizontal drawing-board, be maintained in place by a weight Q. Where the
drawing-board is vertical, a bar E may be provided, which is adjustable and which,
by means of a set-screw ', may be fixed in any desired position in a block or
clamp D, capable of being tightly secured to the board by means of a screw d. In
the forked end e of the said bar E is mounted a style or marker q'.

page_text: The distance between the two points a and a must, therefore, be so determined
as to be in the same relation to the visual distance, as the sum of diagonals of the
large and small parallelograms of the pantograph is to the diagonal of the small
parallelogram. When the distance has thus been adjusted, the point of inter-
section c will be situated on the straight line drawn from the point b to the vanishing
point. It will, therefore, be sufficient to mark the said point c and draw the line bc,
to solve the problem as stated above, and c' will, as a matter of course, be the
perspective image of the perpendicular constructed on b c.
Should it be desired to cut the straight line bc at a certain distance, the ruler C
is so adjusted that, in conjunction with the ruler A, it forms an angle equal
to FO. A line is then drawn parallel to the ruler A, a given distance
being measured off in the required direction (according to the amount of correction
necessitated by the position of the point relatively to the plane of the picture)
whereby the point is reached. The style 6 is next placed at 6*; the point of
intersection of the ruler C₁* with the ruler A is marked off; and the straight
line is drawn, which, as will be readily seen, passes through the point of
intersection T. The intersection of this line 6* c with the line bc then gives
the required perspective image of the terminal point b*.
A, a*, *, C, C₁ here designate the same parts as do the corresponding letters
without the asterisk in Figure 1, when these parts occupy the positions conducive
to the solution of the second problem.
From the foregoing description, any person skilled in the art of perspective
drawing will readily understand the mauner in which the instrument should be
handled in a given case.
The same instrument will prove serviceable in working out the problem, above
stated, inversely, that is to say, in constructing a plan and elevation from a given
perspective view. For this purpose, it is only necessary to find, by construction or

page_text: conjecture, the visual point or point of sight and horizon for the two main lines of
the image, which lines extend at right angles to each other in the same plane.
Let the point be q, and the horizon line for the lines b c and b¹ c', as at F F',
Figure 5. The style g is placed at the visual point, and the style b, at the point of
intersection of the two lines bc and c; the ruler A is made parallel to the
horizon, and the two rulers C C' are turned and shifted until they pass through the
points of intersection c c' of the ruler A. with the lines b, c and b₁ c'; the styles q
and I, however, remaining at rest in the meantime. The distance between a and
will then be the visual distance, while the angles ca and c¹ a give the degree of
inclination of the two straight lines to the plane of the picture.
I
The point is determined on the ruler A by tightening the screw a'. If it be
desired to determine the exact length of part of the line 6 c, say the distance C C',
the ruler C is placed in such a position as to include between it and the ruler A an
angle equal to ca; whereupon the style 6 is moved in a straight line parallel to
the horizon (q remaining stationary, and A parallel to the horizon) until a straight
line (b, Figure 5) passing through the intersection of C and A, and through
the point b intersects the line b c, at t. It will be understood that the distance b b*,
Figure 5, thus found, requires correcting, in accordance with the position of the
point in relation to the plane of the image.
When the distance a x is found for a given perspective view in the manner above
stated, it is only necessary, in order to determine the angle of inclination of a line
to the plane of the picture, to place the style b at any point of such line; and then
to turn the rulers CC' about until one of them passes through the point of inter-
section of the said line with the ruler A. The angle which the ruler C, or C', then
forms with the ruler A, gives the required angle of inclination.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
-
An instrument for converting a plan and elevation into a perspective view, or for
performing the reverse operation, which instrument consists of two rulers (A A¹)
arranged at right angles to each other, to one of which (A') are pivotted two other.
rulers (C C'), also arranged at right angles to each other, both turning about, and
intersecting at, an adjustable point (x) movable along the first of these rulers and
of a pantograph (Ss) pivotted at the point of intersection (a) of the first mentioned
rulers (A A¹), substantially as hereinbefore described.
Dated this 15th day of March 1894
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicant.