An Automatic Image Finder for Lenses and Mirrors.
Year: 1893

page_text: Date of Application, 12th Aug., 1893
Complete Specification Left, 11th May, 1894 Accepted, 11th Aug., 1894
PROVISIONAL SPECIFICATION.
An Automatic Image Finder for Lenses and Mirrors.
RICHARD CREAGH BODKIN Roman Catholic Clergyman and Professor of
Natural Philosophy, St. Vincent's College, Castleknock co. Dublin do hereby
declare the nature of this invention to be as follows:-
The automatic image finder for lenses and mirrors is an instrument by means of
which an object placed in any position immediately indicates where its image must
be and proves experimentally that the image is there. The instrument consists of
an object (A) capable of being moved with ease into various positions.
From the extremities of this object proceed two parallel rays (in the shape of
wires) along which it travels. These parallel rays according to theory are always
refracted to the principal focus (B) and the ray or wire passing through B,
represents the path of one of them.
The direction of this ray or wire is therefore always constant no matter where
the object is placed. The only thing then to be determined is at what point will
these rays intersect the secondary axes. Now, the secondary axes are always
straight lines drawn from the extremities of the object and passing through the
centre of the lens. Hence in the instrument there are two wires passing through
the centre of the lens and also through the extremities of the object. These wires
work on a pivot and so are capable of moving in or out according as the position
of the object requires. The object can slide along them and by its motion open
or close them owing to the fact that these secondary axes pass through two eyes
or similar fittings, placed on the extremities of the object. Thus the point at
which the parallel rays and the secondary axes must meet is shown and so the
position of the image.
The focus (B) is capable of being altered, as it slides in a groove or other
adjustable fitting, to suit lenses of different focus. In the case of concave lenses
the only change to be made is to place the focus (B) at the opposite side where a
similar adjustable fitting is also provided. To prove experimentally that the image
is really at the place indicated-a candle lamp, electric lamp or similar light giving
source is placed immediately over the object (A). Over the section of the lens is
placed a glass lens of known focus, the refracted parallel ray passing through the
principal focus (B) is fixed to the focus of the lens-a screen is placed at the
point where the parallel rays intersect the secondary axes and immediately a
sharp image of the object appears on it.
Dated this 8th day of August 1893.
An Automatic Image Finder for Lenses and Mirrors.
RICHARD CREAGH BODKIN Roman Catholic Clergyman and Professor of
Natural Philosophy, St. Vincent's College, Castleknock, co. Dublin, 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 automatic image finder for lenses and mirrors is an instrument by means of

page_text: which an object placed in any position immediately indicates where its image must-
be and proves experimentally that the image is there.
The instrument consists of an object (A) capable of being moved with ease into
various positions. From the extremities of this. object proceed two parallel
rays C. C. (in the shape of wires) along which it travels. These parallel rays
according to theory are always refracted to the principal focus (B) and so the
ray or wire passing through B represents the path of one of them. The direction of
this ray or wire is therefore always constant no matter where the object is placed.
The only thing then to be determined is at what point will these rays intersect the
secondary axes. Now, the secondary axes D. D are always straight lines drawn
from the extremities of the object and passing through the centre of the lens.
Hence in the instrument there are two wires D. D. passing through the centre of
the lens and also through the extremities of the object. These wires work on a
pivot E. and so are capable of moving in or out according as the position of the
object requires. The object can slide along them and by its motion open or close
them owing to the fact that these secondary axes pass through two eyes or similar
fittings F. F. placed on the extremities of the object. Thus the point at which
the parallel rays and the secondary axes must meet is shown and so the position
of the image. The focus (B) is capable of being altered, as it slides in a groove
or other adjustable fitting, G to suit lenses of different focus. In the case of
.concave lenses the only change to be made is to place the focus (B) at the
opposite side where a similar adjustable fitting H is also provided. To prove
experimentally that the image is really at the place indicated-a candle lamp,
electric lamp or similar light giving source K is placed immediately over the
object (A) over the section of the lens M is placed a glass lens of known focus L.
the refracted parallel ray passing through the principal focus (B) is fixed to the
focus of the lens-a screen S, is placed at the point where the parallel rays intersect
the secondary axes and immediately a sharp image of the object appears on it.
To use the instrument for virtual images push the wire that passes through the
hole in (B) on towards the side of the lens on which the object (A) is. Where
this wire meets the secondary axis (D) in front of the lens (L) there is the
image.
"
To use the instrument for a concave lens take the ray or wire that passes
through (B) and make it pass through (H) and the moveable screw-head at L.
Where this ray or wire cuts the secondary axis (D) there is the image.
For concave mirrors the same structure holds. The rays or wires D and D still
represent the secondary axes-and the pivot on which these rays turn is the centre
of curvature. The screw (B) is the principal focus and the mirror is placed at
about No. 8. The parallel ray C is produced in a straight line till it meets the
mirror at No. 8 and from this point where it meets the mirror the ray or wire (B)
is caused to pass through the principal focus (B). Where these two intersect
there is the image.
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 automatic image finder for lenses and mirrors, by means of which an object
placed in any position immediately indicates where its image must be and proves
experimentally that the image is there substantially as described.
1
RICHARD CREAGH BODKIN.