Digital Camera Patent Abstract
A digital camera (300) has panning and/or tilting functionality
and comprises: a camera housing (6) with an optical input (400),
such as a lens or objective (8); an image capturing unit (500) for
producing a digital image from light received through the optical
input; and a controller (600). A first mirror (9) is mounted externally
to the camera housing (6). An image rotating device (200) receives
an angular displacement control signal from the controller (600)
and rotates the first mirror at an angle with respect to the optical
input (400, 8) of the camera housing (6).
Digital Camera Patent Claims
The invention claimed is:
1. An apparatus for panning and tilting an optical input to an
objective of a stationary camera; and the apparatus comprising:
a panning mirror rotationally coupled to the camera for bending
the optical input to align with an optical axis of the objective
and the optical input and the optical axis defining a plane, and
a rotation of the panning mirror panning the optical input to the
objective of the camera about the optical axis; a tilting mirror
radially displaced from the panning mirror about the optical axis,
and rotationally coupled to the camera for rotation concentric with
the panning mirror about the optical axis, and the tilting mirror
optically coupled with the panning mirror and the titling mirror
configured to tilt the optical input in selectable amounts about
an axis substantially perpendicular to the plane; and a planetary
linkage coupling the panning mirror and the titling mirror, and
including: a mirror wheel rotatable about the optical axis, and
the panning mirror affixed to the mirror wheel and the titling mirror
tiltably affixed to the mirror wheel both for rotation about the
optical axis; a guide wheel rotatable about the optical axis; and
a planetary member mechanically coupled to both the guide wheel
together with the mirror wheel to convert a relative rotation there
between into a rotation of the planetary member and the planetary
member further coupled to the tilt mirror to convert rotation of
the planetary member into titling of the tilt mirror.
Digital Camera Patent Description
The present invention relates to a digital camera having panning
and/or tilting functionality, and more specifically to a digital
camera having a camera housing with an optical input, such as a
lens or objective, an image capturing unit and a controller. The
invention also relates to an image rotating device for providing
the panning and/or tilting functionality of such a digital camera.
A common example of a digital camera with panning and/or tilting
functionality is a web camera, which e.g. may be mounted at a given
location for the purpose of surveillance, production monitoring,
etc. The web camera comprises an optical input in the form of a
lens or objective and an image capturing unit for producing a digital
image from light received from the optical input. Usually, the image
capturing unit comprises a CCD element (Charge Coupled Device).
The web camera has software and hardware for allowing the camera
to be connected to a given network, such as an Ethernet or Token
Ring network. The web camera is arranged to produce digital images
at a given rate, such as 1-25 images per second. In order to increase
the visual volume covered by the web camera, the camera is provided
with mechanical means for panning and/or tilting the camera. Generally
speaking, "panning" means rotating the camera by a given
angle (normally 0.degree.-360.degree.) in a horizontal plane, and
"tilting" means rotating the camera by a given angle (normally
0.degree.-180.degree.) in a vertical plane.
In prior art web cameras the panning and/or tilting functionality
is obtained by moving the whole camera or at least the objective
thereof. Since the camera and objective have a considerable weight,
such an approach involves complex, large and expensive mechanics.
Furthermore, the speed at which the camera may be panned or tilted
is restricted due to the large mass, that has to be moved accordingly.
It is an object of the present invention to provide a digital camera,
which allows faster and more accurate panning and/or tilting, thereby
allowing the camera to produce more images per time unit. Furthermore,
it is an object of the present invention to provide an image rotating
device, to be mounted externally to the digital camera, for providing
efficient and rapid panning and/or tilting funtionality, without
requiring large or expensive mechanics.
The above objects are achieved by providing the digital camera
with an image rotating device having a mirror mounted externally
to the camera housing and having a rotational member for rotating
the mirror with respect to the optical input (lens or objective)
of the camera housing in response to an angular displacement control
signal received from a controller of the digital camera.
Other objects, features and advantages of the present invention
will appear from the following detailed disclosure, from the appended
claims as well as from the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention will now be described
in more detail, reference being made to the accompanying drawings,
FIG. 1 is a schematic block diagram of the overall structure of
a digital camera according to the preferred embodiment,
FIG. 2 is a first sideview of the image rotating device and the
camera, to which it is mounted,
FIG. 3 is a second sideview of the image rotating device and the
camera shown in FIG. 2, and
FIG. 4 is a topview of the image rotating device shown in FIGS.
2 and 3.
Referring to FIG. 1, a digital camera 300 is illustrated in a basic
modular form. The digital camera 300 is arranged to produce one
or several digital image(s) of a generic object 100, which may be
any physical object that is present in a volume optically covered
by the digital camera 300. An inventive image rotating device 200
is mounted externally to the digital camera 300 in front of an optical
input 400 of the digital camera. The optical input 400 is a generally
known lens or objective. The purpose of the image rotating device
200 is to extend the available field of view of the digital camera
300 in at least one plane, preferably in a horizontal plane as well
as in a vertical plane. A preferred embodiment of the image rotating
device 200 will be described in more detail with reference to FIGS.
As shown in FIG. 1, the digital camera 300 further comprises an
image capturing unit 500, which is provided with appropriate means
for producing a digital image representative of the object 100.
Preferably, the image capturing unit 500 comprises a CCD element
(Charge Coupled Device), the internal structure of which is believed
to be well-known to a man skilled in the art. The digital camera
300 also has a controller 600 for controlling the image capturing
unit 500 as well as the external image rotating device 200. The
controller 600 is operatively connected not only to the device 200
and the unit 500 but also to a digital memory 700 for storing images
captured by the image capturing unit 500. Furthermore, the digital
camera 300 may comprise an image transforming unit 800, the purpose
of which is to rotate the digital image to compensate for image
rotating effects caused by the image rotating device 200, when the
field of view is panned or tilted. The image transforming unit 800
is responsive to an angle of rotation of the image rotating device
200 with respect to the objective 400 and uses this angle of rotation
when transforming the digital image to compensate for the current
pan and/or tilt angle. To perform such image transforming, i.e.
to rotate a digital image in one or more than one direction, is
believed to be well within reach of a man skilled in the art of
digital cameras. Therefore, the internal structure of the image
transforming unit 800 will not be described herein.
The memory 700 may be implemented by any commercially available
memory, such as an EEPROM memory.
As indicated in FIG. 1, the digital camera 300 may be connected
to a network 900, such as an Ethernet or Token Ring network, which
in turn may be part of the Internet. In such an application, the
controller 600 of the digital camera 300 is provided with appropriate
software for allowing the digital camera 300 to act as a web camera
available on the network 900, i.e. a web server that produces digital
The pan and/or tilt angle of the digital camera 300, or more specifically
the angle(s) by which the image rotating device changes the field
of view of the camera 300 with respect to a central axis of the
objective 400, may be set and changed by a user of the camera by
accessing the controller 600 through the network 900. Alternatively,
the pan and/or tilt angle(s) may be controlled from a computer directly
connected to the digital camera 300.
A preferred embodiment of the image rotating device 200 will now
be described in more detail with reference to FIGS. 2-4. The following
elements are shown in these drawings:
TABLE-US-00001 Qty Ref. No. Name 1 19 Frame 1 18 Timing belt tightener
1 17 Belt wheel 1 16 Timing belt 1 15 Belt wheel 1 14 Timing belt
1 13 Timing belt tightener 2 12 Optical sensor 1 11 Mirror holder
1 10 Tilting mirror 1 9 Fixed mirror 1 8 Camera lens (objective)
2 7 Motor 1 6 Camera housing 1 5 Mirror wheel 1 4 Bevel gear 1 3
Tilt shaft 2 2 Fixing part 1 1 Guiding wheel
The image rotating device 200 has a mirror system, comprising a
first fixed mirror 9 and a second tilting mirror 10. The fixed mirror
9 is mounted directly in front of the objective 8 at an angle of
37.degree. relative to the optical center axis of the camera 300.
The fixed mirror 9 is mounted to a mirror wheel 5, which is rotatable
around the objective and hence provides a field of view with an
angle of rotation of between 0.degree. and 360.degree..
In the center of the field of view the tilting mirror 10 is mounted,
so that the axis of rotation thereof is perpendicular to the optical
center axis of the camera. The tilting mirror 10 is carried on the
mirror wheel 5, thereby causing the tilting mirror 10 to rotate
around the objective 8 together with the fixed mirror 9. Thanks
to the geometrical arrangement of the mirrors 9 and 10 with respect
to the objective 8, it is possible to monitor a large volume in
a short time.
The tilting mirror 10 is attached to a mirror holder 11, which
in turn is journalled in the mirror wheel 5 between two fixing parts
2. Opposite to the mirror wheel 5 a slightly smaller guiding wheel
1 is concentrically mounted. A tilt shaft 3 is eccentrically mounted
to the mirror wheel, so as to cause the tilting mirror 10 to move.
The guiding wheel 1 transmits its motion to the tilt shaft 3 and
from the tilt shaft 3 through a bevel gear 4 to the mirror holder
11. The arrangement resembles a planetary gear, where the guiding
wheel represents a sun pinion and the tilt shaft represents a planet
pinion. The mirror wheel acts as holder of the planet pinion.
When the mirror wheel does not move, if the guiding wheel is rotated,
the tilt shaft 3 will rotate around its own axis, wherein the mirror
holder 11 will be rotated around its axis of rotation. Hence, the
tilting mirror 10 is rotated with respect to the mirror wheel 5,
and the center axis of the field of view will be angled with respect
to the optical center of the camera. If the mirror wheel 5 and the
guiding wheel 1 rotates at the same angular velocity, there will
be no relative motion in the tilt shaft and consequently no rotation
of the mirror holder/mirror around its axis of rotation. However,
the mirror wheel 5 as a whole will rotate with the fixed mirror
9 and the tilting mirror 10 at a constant angle to the optical center
axis of the camera.
In other words, by rotating the mirror wheel 5 and the guiding
wheel 1 synchronously, the field of view may be rotated 360.degree.
for any given tilt angle. Then, if the wheels are rotated relative
to each other, the angle of the mirror holder 11 will change, and
the field of view may be again be rotated 360.degree. for a new
tilt angle. In this way, a very large volume around the camera may
be covered, and images may be obtained for any given location within
this large volume.
The mirror wheel 5 and the guiding wheel 1 are driven by respective
motors 7. Belt wheels 15, 17, timing belts 14, 16 and timing belt
tighteners 13, 18 are provided, as shown in FIGS. 2-4.
The inventive image rotating device provides at least the following
advantages: Low moment of inertia for rotating parts High pan/tilt
adjustment speed, short time between angular settings High setting
accuracy Compact design Few structural components Low manufacturing
cost Flexible design Simple pan/tilt control Wide field of view
The present invention has been described above with reference to
a preferred embodiment. However, other embodiments than the one
disclosed herein are possible within the scope of the invention,
as defined by the appended independent patent claims.