Improvements in Focussing Photographic Cameras.
Year: 1898

page_text: Date of Application, 13th Aug., 1898
1000
PROVISIONAL SPECIFICATION.
Improvements in Focussing Photographic Cameras.
I, HARRY WILLIAMSON TEED, of 18S, Camberwell Grove, in the County of
Surrey, Civil Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to improvements in photographic cameras.
It has for its object the providing of a means for focussing the lens without
examining the image projected by the lens, or making direct measurements of
either of the conjugate foci of the lens or of the distance between the image and the
object.
In carrying out this invention I gear the mechanism for focussing, with
the mechanism of a range finder of the type in which the base-line is contained
in the instrument, in such manner that the operating of the range finder
actuates the focussing mechanism in such a manner that the lens is in focus for
objects at the range chosen.
I prefer to carry this out in the following manner.
I gear with the mechanism for focussing, a mechanism comprising two mirrors,
the one fixed and the other movable, arranged in such a manner that a part of
the object may be viewed directly and the other part after reflection from the
two mirrors. The movable mirror is geared with the focussing mechanism in
such a manner that the image of any object shall be in focus in the camera when
the portion of the object viewed after reflection from the two mirrors shall as
nearly as possible form a continuous image with the portion of the object viewed
directly.
For viewing the object and the image after reflection from the two mirrors I
prefer to use a "bright" type of "finder," but can employ any other suitable
arrangement.
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C
1900
Improvements in Focussing Photographic Cameras.
I, HARRY WILLIAMSON TEED, of 18S, Camberwell Grove, in the County of
Surrey, Civil Engineer, do hereby declare the nature of this invention and in
Price 8d1

page_text: what manner the same is to be performed, to be particularly described and
ascertained in and by the following statement:-
This invention relates to improvements in photographic cameras.
It has for its object the providing of a means for focussing the lens without
examining the image projected by the lens or making direct measurements of
either of the conjugate foci of the lens or of the distance between the image and the
object. In carrying out this invention I gear the mechanism for focussing with
the mechanism of a range finder, of the type in which the base line is contained
in the instrument, so that the operating of the range finder actuates the focussing
mechanism. in. such a manner that the lens is in focus for objects at the range
chosen. One method of carrying out this invention will be understood by refer-
ence to the accompanying drawings. Figure 1 shows the relative position of the
chief parts of the device in plan but with the plate K removed. Figure 2 is a
section of the device taken through the line a x. A is a guide upon which slides
the sliding piece B. The lens of the camera is attached in any convenient
manner to B and travels with it, being actuated by a rack and pinion or other
suitable means. C is another guide parallel to A, upon which slides the piece D.
J is a lever slotted at each end and pivoted at S to the piece P. P is a sliding
piece which may be fixed in any desired position upon the guide R. R being
rigidly fixed to the plate K. L is a pin fixed to the piece B and working in the
slot at one end of the lever J. M is a pin fixed to the piece D and working in the
slot at the other end of the lever J. T is a screw fixed in a bracket on the sliding
piece D. The point of the screw T is in contact with a cam shaped piece E which
is pivoted at Q and kept in contact with the screw T by means of a spring. G is
a mirror fixed to the piece E. H is another mirror fixed to the plate K. The
reflecting surfaces of the mirrors are towards each other and G is so arranged
that when the lens is in focus for objects at an infinite distance the mirror Gis
parallel to the fixed mirror H. F is a bright finder suitably placed for viewing
the mirror H. The reflecting surface of the mirror H only extends to the line
opposite to the centre of the finder the other half being clear glass. The movable
mirror is geared with the focussing mechanism in such a manner that the image
of any object shall be in focus in the camera when the portion of the object
viewed after reflection from the two mirrors shall as nearly as possible form a
continuous image with the portion of the object viewed directly. The curve of
the cam E is for convenience worked out for a certain focal length of lens in
conjunction with the base line of the range finder so as to have the two
leverages M S and S L equal but if it is desired subsequently to use a lens of any
other focal length, the leverages M S and S L are made proportional to the focal
length of the original lens and the focal length of the lens substituted respec-
tively, by shifting the position of the sliding piece P along the guide R. The
curve of the cam E may be obtained for a lens of any particular focal length
either by trial or by calculation. If by calculation, the angle through which the
mirror G must be moved from its position parallel to the mirror H for any
particular range must be combined with the distance through which the lens
must be moved from its position at focal length from the focal plane to the
focussing position using for the calculation the well known properties of lenses.
The various parts can be made of any suitable materials and can be modified in
various ways without departing from the nature of my present invention.
+
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed I declare that what
I claim is:
1. The combination of a range finder of the type in which the base is contained
in the instrument with the focussing mechanism of a camera for the purpose of
focussing.
2. The combination of a range finder comprising two mirrors, the one fixed 5

page_text: and the other movable, with the focussing mechanism of a camera substantially
as and for the purpose described.
3. The combination of a range finder comprising two mirrors the one fixed and
the other movable, with the focussing mechanism of a camera and
as and for the purpose described.
bright finder