Improvements in Photographic View Finders.
Year: 1896

page_text: Date of Application, 22nd Dec., 1896.
[Communicated from abroad by ALFRED CLIFFORD MERCER 324 Montgomery
Street Syracuse New York of the United States of America Physician.]
Improvements in Photographic View Finders.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton Buildings, in the County of Middlesex, do hereby declare the
nature of this invention to be as follows:-
The object of my invention is to produce a reduced, clear, upright and not-
reversed-from-right-to-left, and brilliant image of exactly the same portion of a
view or object that is to be photographed, this image being produced when the
camera is held in a convenient position in front of the chest or abdomen and the
eyes of the observer are directed conveniently obliquely (not perpendicularly)
downward toward the finder.
While my finder might be enclosed in a separate box attached to the outside
of the camera box, I prefer (and the character of my finder allows me) to place it
within the camera box, in a portion partitioned off for the purpose. In this
partitioned off portion is supported a glass-body having triangular end surface
and rectangular sides. I polish the three plane rectangular and silver one of the
said surfaces. I provide apertures in the top and front of the partitioned off
portion of the camera box, of the relative proportion hereinafter specified, and in
the front aperture I fit a negative lens. Now when light from the object enters
the aperture, through the negative lens, it pierces the surface opposite the lens,
passes to the silvered back surface on the opposite face, is reflected back to the first
mentioned surface, suffers total reflection (as presently explained), and passes
out through the top surface and opening to the eye. I am especially particular
to make the angles formed by the said three surfaces with each other and with
the vertical, such that while the surface opposite the lens freely transmits the
entering light, it totally reflects the light returned to it from the back surface.
To effect the above-mentioned total reflection in the best manner, I find it
advisable to make the lower angle of the glass-body, the upper front angle, and
the upper back angle; and to place the back surface nearly vertical.
This arrangement effects another object of my invention, by resulting in tipping
the upper surface at a considerable acute angle to the rays of light emitted through it.
It is a well known defect in finders, that where the emitting surface fronts the
eye, the face of the user as well as the sky and other objects at the back of him
are seen reflected from the emitting surface. With my finder, the refraction
at the admitting surface opposite the lens is balanced by that at the emitting
or top surface, and thus I am enabled to incline the latter without producing
fringes of prismatic color in the image. Being so enabled, I set a black screen
above the emitting surface, in such a position as to be all that is reflected
to the eye from said surface. The emitted image is thus preserved perfectly
clear and brilliant. It is also upright, and is not reversed from right to left,

page_text: and in consequence the camera may be correctly pointed with great facility.
That the user may see exactly as much and no more of the field of vision as
will appear in the photograph, I so proportion the apertures that when the eye
is at the right distance from the emitting aperture to see through it the precise limits
of the photograph, the admitting aperture will appear to be just the same size
as the emitting aperture. In other words, the apertures are of such relative size that
their visual coincidence correctly locates the eye.
I am aware that devices exist whereby the eye can be known to be in the central
line of the rays from the image; but the user, in looking into any finder, uncon-
sciously ranges his eye approximately in that line, and what he really needs--and
what I have invented is a means of locating the exact point in the line, from
which the whole image and no more will be visible. It will be perceived that the
negative lens refracts the rays so that while the eye is held a foot or more
from the emitting aperture and that aperture therefore, subtends a small visual
angle, the limits of the view subtend a much larger angle as they enter the
finder, so much larger, in fact, that there is no difficulty in making them corre-
spond with the angle of whatever camera-lens may be used. Or to put it the
other way, the lens throws back the converging-point of the rays, so that the
position of the eye is natural when the camera is held naturally and firmly
opposite the chest or abdomen.
Dated this 22nd day of December 1896.
HASELTINE, LAKE & Co.,
45 Southampton Buildings, W.C., Agents for the Applicant.
I, HENRY HARRIS LAKE, of the Firm of Haseltine, Lake & Co., Patent Agents,
45 Southampton Buildings, in the County of Middlesex, 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 my invention is to produce a reduced, clear, upright and not-
reversed-from-right-to-left, and brilliant image of exactly the same portion of a
view or object that is to be photographed, this image being produced when the
camera is held in a convenient position in front of the chest or abdomen and the
eyes of the observer are directed conveniently obliquely (not perpendicularly)
downward toward the finder.
In the accompanying drawings,
Figure 1 is a longitudinal vertical section through the improved finder and
the portion of the camera to which it is or might be attached and,
Figure 2 is an isometric projection of the same, part of the camera box being
broken away.
While my finder may be enclosed in a separate box attached to the outside
of the camera box, I prefer (and the character of my finder allows me) to place it
within the camera box, in a portion partitioned off for the purpose. In the
drawing indicates the camera box, and 2 the partition. In this partitioned
off portion is supported a glass-body or prism (3) having triangular and faces (4)
and rectangular sides (5, 6, 7). I polish the 3 plane rectangular side surfaces 5, 6, 7
and silver the surfaces 5. I provide apertures 8 and 9 in the top and front of the
partitioned off portion of the camera box, of the relative proportion hereinafter
specified; and in the front aperture (9) I fit a negative lens (10).

page_text: light (LL) from the object enters the aperture 9, through the negative lens (10),
it pierces the surface 7, passes to the silvered surface (5) is reflected back to the
surface 7, suffers total reflection (as presently explained), and passes out through
the top surface 6 and opening 8 to the eye (E). I am especially particular to
make the angles, formed by the surfaces, 5, 6, 7 with each other and with the
vertical, such that while the surface 7 freely transmits the entering light, it
totally reflects the light returned to it from the surface 5. In the figures, the four
extreme rays of light from the view are shown.
To effect the above-mentioned total reflection in the best manner, I find it
advisable to make the lower angle of the glass-body 350, the upper front angle 70°,
and the upper back angle 75° and to place the back surface (5) nearly vertical.
This arrangement effects another object of my invention, by resulting in tipping
the surface 6 at a considerable acute angle to the rays of light emitted through it.
It is a well known defect in finders, that where the emitting surface fronts the
eye, the face of the user as well as the sky and other objects at the back of him
are seen reflected from the emitting surface. With my finder, the refraction
at the admitting surface (7) is balanced by that at the emitting or
top surface (6), and thus I am enabled to incline the latter without producing
fringes of prismatic color in the image. Being so enabled, I set a black screen (11)
above the emitting surface (6), in such a position as to be all that is reflected
to the eye from said surface. The emitted image is thus preserved perfectly
clear and brilliant. It is also upright, and is not reversed from right to left,
and in consequence the camera may be correctly pointed with great facility.
That the user may see exactly as much and no more of the field of vision as
will appear in the photograph, I so proportion the apertures 8 and 9 that when the
eye is at the right distance from the aperture 8 to see through it the precise limits
of the photograph, the aperture 9 will appear to be just the same size
as the aperture 8. In other words, the apertures are of such relative size that
their visual coincidence correctly locates the eye.
I am aware that devices exist whereby the eye can be known to be in the central
line of the rays from the image; but the user, in looking into any finder, uncon-
sciously ranges his eye approximately in that line, and what he really needs-and
what I have invented-is a means of locating the exact point in the line, from
which the whole image and no more will be visible. It will be perceived that the
negative lens (10) refracts the rays so that while the eye is held a foot or more
from the aperture 8 and that aperture therefore subtends a small visual
angle, the limits of the view subtend a much larger angle as they enter the
finder, so much larger, in fact, that there is no difficulty in making them corre-
spond with the angle of whatever camera-lens may be used. Or to put it the
other way, the lens throws back the converging-point of the rays, so that the
position of the eye is natural when the camera is held naturally and firmly
opposite the chest or abdomen.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, as communicated to me
by my foreign correspondent, I declare that what I claim is:
1. In a photographic view finder, the combination of: first, a negative lens
suitably supported and fixed in the front opening of a box and perpendicularly
to and first in the path of the light passing from the object of view through the
finder to the eye; second, a glass-body (preferably a triangular prism with rectangu-
lar sides), suitably supported and fixed just behind the said negative lens, below a top
opening in the said box and in the said path of light, having two polished internally
reflecting sides one of which, not silvered, is placed or cut at such an angle to the
other which is, silvered that the former or first side transmits one part of a ray
or pencil of light on its' way from the object or view to the latter or second side,
and, simultaneously, totally reflects another, later, part, of the same ray or pencil

page_text: of light, on its way from the said second internally reflecting side to the eye;
third, a final upper emitting and refracting polished side of the said glass-body.
oblique to the now emitted and refracted said ray or pencil (or said path) of light
and fixed at such an angle to a black screen, which is suitably supported and
fixed in the said box just above and in front of the said glass-body; that the
said screen only is reflected to the eye by the said emitting and refracting side;
fourth, two contours, one bounding the said front opening in the said box and
the other bounding the said top opening in the said box, so proportioned as
visually to coincide when the eye is correctly located in using the finder.
2. In a photographic view finder, the combination of: first, a negative lens
suitably supported and fixed in the front opening of a box and perpendicularly
to and first in the path of the light passing from the object or view through the
finder to the eye; with, second, a glass-body (preferably a triangular prism with
rectangular sides) suitably supported and fixed just behind the said negative
lens, below a top opening in the said box and in the said path of light, having
two polished internally reflecting sides, one of which, not silvered, is placed or cut
at such an angle to the other which is silvered that the former simultaneously
transmits one part of, and totally reflects another part of it the same ray or pencil
of light passing from the object or view through the finder to the eye; and with,
third, a final upper emitting and refracting polished side of the said glass body, oblique
to the now emitted and refracted said ray or pencil (or said path) of light, and
fixed at such an angle to a black screen, which is suitably supported and fixed
in the said box just above and in front of the said glass-body, that the said
screen only is reflected to the eye by the said emitting and refracting side.
3. In a photograph finder, the combination of: first, a negative lens suitably
supported and fixed in the front opening of a box and perpendicularly to and
first in the path of the light passing from the object or view through the finder
to the eye, with, second, a glass-body (preferably a triangular prism with rectan-
gular sides), suitably supported and fixed just behind the said negative lens, below
a top opening in the said box and in the said path of light, having two polished
internally reflecting sides one of which, not silvered, is placed or cut at such an
angle to the other which is silvered that the former simultaneously transmits
one part of, and totally reflects another part of, the same ray or pencil of light
passing from the object or view through the finder to the eye."
In a photographic view finder, a glass-body (preferably a triangular prism
with rectangular sides) having two polished internally reflecting sides one of
which, not silvered, is placed or cut at such an angle to the other which is silvered
that the former or first side transmits one part of a ray or pencil of light, on
its way from the object or view to the latter or second side, and simultaneously,
totally reflects another, later, part of the same ray or pencil, on its way from
the said second internally reflecting side to the eye.
5. In a photographic view finder, a glass-body (preferably a triangular prism
with rectangular sides) having two polished internally reflecting sides one of
which, not silvered, is placed or cut at such an angle to the other which is
silvered that the former simultaneously transmits one part of, and totally reflects
another part of, the same ray or pencil of light passing from the object or view
through the finder to the eye.
6. In a photographic view finder, a glass-body having a polished light-admitting,
side, and a polished, and silvered internally reflecting side, the latter placed or cut
at such an angle to the former as to reflect the light (passing from the object
or view through the finder to the eye) back to the former and at such an angle
of incidence at the said former side that the said light is now totally reflected
from the said admitting side towards the eye.
7. In a photographic view finder, a glass-body having a polished and silvered
internally reflecting side, and a polished, light transmitting side which latter
stands in the way of the light passing. both to and from the former, or said

page_text: silvered side, and which latter is also so inclined to the former, or said silvered
side, that while transmitting one portion of a ray or pencil of light in its path
from an object or view through the finder to the eye it at the same time totally
reflects another portion of the same ray or pencil of the said light in the said
path.
8. In a view finder, a glass-body having an admitting surface and a reflecting
surface placed at such an angle as to reflect the light (passing from the object
to the eye through the finder back to the admitting surface so obliquely to the
latter as to cause total reflection from said latter to the eye.
9. In a finder, a glass-body having a reflecting surface, and having a transmitting
surface lying in the paths of the rays from the object to the eye through the
finder) passing both to and from said reflecting surface and so inclined that while
transmitting one set of rays it will totally reflect the other set.
10. In a view finder, a glass-body having a final emitting surface oblique to
the emitted pencil of light, in combination with a screen so placed and sized as
to be alone reflected to the eye by said surface.
11. In a view finder, the combination of light-admitting and emitting apertures
of such relative size that the point from which they appear the same size will
be the point from which the view through them will have the same limits as the
photograph.
12. In a view finder, the combination of two contours in the path of light
from the view to the eye through the finder, so proportioned as visually to
coincide when the eye is correctly located.
13. In a view finder, the combination of a negative lens in the path of light
from the view to the eye through the finder, with two contours in said path so
proportioned as visually to coincide when the eye is correctly located.
14. In a view finder, the combination of a negative lens in the path of the light
from the view to the eye through the finder, with a glass-body having an admitting
surface, and a reflecting surface placed at such an angle as to reflect the light
(passing along said path) back to the admitting surface so obliquely to the
latter as to cause total reflection from said latter to the eye.
Dated this 14th day of September 1897
HASELTINE, LAKE & Co.,
45 Southampton Buildings, London, W.C., Agents for the Applicant.