An Improved Appliance applicable as a View Finder or otherwise in Optical Instruments.
Year: 1896

page_text: Date of Application (in United Kingdom), 28th May, 1896
Complete Specification Left, 1st Mar., 1897-Accepted, 3rd Apr., 1897
PROVISIONAL SPECIFICATION.
An Improved Appliance applicable as a View Finder or otherwise
in Optical Instruments.
I, JULES RICHARD of 8, Impasse Fessart, Paris, France, Scientific Instrument
Maker, do hereby declare the nature of this invention to be as follows:-
In photographic view finders provided with a mirror placed at forty-five degrees,
the picture presented to view although apparently rectified is still reversed as
regards right and left which renders it very difficult to follow a moving object.
The present invention has for its object a system of double reflection whereby
the rectification as regards right and left is effected also so that a perfectly rectified
picture is presented to the retina.
To obtain this result I have devised a special form of prism in which the image
instead of being projected upon a plane surface, as in a total reflection prism,
strikes upon two of its faces at right angles to each other.
The accompanying drawing represents the arrangement as applied to a camera
for facilitating the explanation but it may be applied with equal advantage to any
other optical apparatus.
Figure 1 represents a longitudinal section, Figure 2 a section on line 1-2
Figure 1, and Figure 3 a section on line 3-4 Figure 1, of the view finder.
Figure 4 shews the top and bottom sides of the prism.
In the example which I have selected for the purpose of describing and
illustrating one of the applications of my improved view finder, I employ a
prism whose four faces are inclined at certain angles to each other. Figure 4
which represents the prism separately shews that the vertical face a in the
example illustrated is behind the lens which receives the image to be viewed.
The face b of the prism which is horizontal and perpendicular to a corresponds to
the ground glass e shewn in Figures 1 and 2; upon which the image is reflected.
The two other faces c and d are inclined at angles of forty-five degrees both to
face a and to face band meet at their long sides. The image whose rays pass
through the lens is projected upon the faces c and d and by them reflected
through the face upon the ground glass screen whereon the image is viewed
in its completely rectified position. As the two faces of the prism act as mirrors
similarly placed, double reflection is produced which entirely rectifies the image
and reproduces exactly as it appears to direct vision. In the prism described
the image strikes upon two faces at right angles to each other instead of upon
a plane surface as in a total reflection prism.
My system of prism may be applied in many kinds of existing optical apparatus
and I will instance one in which the image is obtained by means of two convex
lenses the first of which gives the true and virtual image and the second

page_text: magnifies it. In this case, as in the camera, the image is inverted. By applying
my system of prism either in front or rear or between the lenses, the above
objection is avoided and a perfectly rectified image is obtained. My improvement
can thus be applied to existing instruments without alteration, which is a great
advantage more especially for the reproduction of pictures, engravings, manuscripts,
etc. Among other applications Figure 5 represents the prism adapted to a spy-
glass having two bi-convex lenses and in Figure 6 as applied to a camera having
two lenses.
It is to be understood that mirrors mounted in positions corresponding to the two
faces c d of the prism hereinbefore described may be substituted for the prism and
form a more economical means of obtaining the same result in cases where less
precision is required.
Dated this 28th day of May 1896.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
An Improved Appliance applicable as a View Finder or otherwise
in Optical Instruments.
I, JULES RICHARD of 8, Impasse Fessart, Paris, France, Scientific Instrument
Maker, 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 :-
In photographic view finders provided with a mirror placed at an angle of 45°,
the picture presented to view although apparently rectified is still reversed as
regards right and left which renders it very difficult to follow a moving object.
The present invention has for its object a system of double reflection whereby
the rectification as regards right and left is effected also so that a perfectly rectified
picture is presented to the retina.
To obtain this result I have devised a special form of prism in which the image
instead of being projected upon a plane surface, as in a total reflection prism,
strikes upon two of its faces at right angles to each other.
Reference is to be had to the drawing accompanying my Provisional Specification
which represents the arrangement as applied to a camera for facilitating the
explanation but it may be applied with equal advantage to any other optical
apparatus.
Figure 1 represents a longitudinal section, Figure 2 a section on line 1-2
Figure 1, and Figure 3 a section on line 3-4 Figure 1, of the view finder.
Figure 4 shews the top and bottom sides of the prism.
In the example which I have selected for the purpose of describing and
illustrating one of the applications of my improved view finder I employ a prism
whose four faces are inclined at certain angles to each other. Figure 4, which
represents the prism separately, shews that the vertical face a in the example
illustrated is behind the lens which receives the image to be viewed. The face b
of the prism which is horizontal and perpendicular to a corresponds to the ground
glass e shewn in Figures 1 and 2 upon which the image is reflected. The two other
faces c and d are inclined at angles of 45° both to face a and to face band meet at
their long sides. The image, whose rays pass through the lens 7, is projected upon
the faces c and d and by them reflected through the face b upon the ground glass
screen whereon the image is viewed in its completely rectified position. As the two
faces cd of the prism act as mirrors similarly placed, double reflection is produced

page_text: which entirely rectifies the image and reproduces it exactly as it appears to direct
vision. In the prism described the image strikes upon two faces c d which are
at a right angle to each other, instead of upon a plane surface as in a total
reflection prism.
My system of prism may be applied in many kinds of existing optical apparatus
and I will instance one in which the image is obtained by means of two convex
lenses the first of which gives the true and virtual image and the second magnifies
it. In this case, as in the camera, the image is inverted. By applying my system
of prism either in front or rear or between the lenses the above objection is avoided
and a perfectly rectified image is obtained. My improvement can thus be applied
to existing instruments without alteration which is a great advantage more
especially for the reproduction of pictures, engravings, manuscripts, etc. Among
other applications Figure 5 represents the prism adapted to a spy-glass having two
bi-convex lenses and in Figure 6 as applied to a camera having two lenses.
It is to be understood that mirrors mounted in positions corresponding to the two
faces c d of the prism hereinbefore described may be substituted for the prism and
form a more economical means of obtaining the same result in cases where less
precision is required.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. The combination, with the lens of a view finder or other optical instrument,
of a prism having its reflecting surfaces inclined relatively to each other and to
the optical axis of the lens at the angles described so as to rectify the image
projected both in the upright and right and left directions substantially as
specified.
2. The combination, with the lens of a view finder or other optical instrument,
of mirrors inclined relatively to each other and to the optical axis of the lens at
the angles described so as to rectify the image projected both in the upright and
right and left directions substantially as specified.
Dated this 1st day of March 1897.
A. M. & WM. CLARK,
53, Chancery Lane, London, Chartered Patent Agents.