U.S. patent application number 11/678911 was filed with the patent office on 2008-05-29 for monitoring camera.
This patent application is currently assigned to SONY CORPORATION. Invention is credited to Norio Ishibashi, Georgero Konno, Makoto Usami.
Application Number | 20080122927 11/678911 |
Document ID | / |
Family ID | 38555571 |
Filed Date | 2008-05-29 |
United States Patent
Application |
20080122927 |
Kind Code |
A1 |
Konno; Georgero ; et
al. |
May 29, 2008 |
MONITORING CAMERA
Abstract
A monitoring camera is provided. The monitoring camera includes
an image capturing unit configured to capture an image of a subject
therein, the image capturing unit having an image capturing field
angle adjustable by a zooming optical system; and a light source
having a light emitting diode configured to emit an illuminating
radiation. The camera further includes a lens unit configured to
apply the illuminating radiation in a direction which is
substantially identical to a direction in which the image capturing
unit captures the image; and an irradiation moving unit configured
to variably set an irradiation range of the illuminating radiation
to irradiate an area which is substantially the same as the image
capturing field angle of the image capturing unit.
Inventors: |
Konno; Georgero; (Kanagawa,
JP) ; Usami; Makoto; (Kanagawa, JP) ;
Ishibashi; Norio; (Kanagawa, JP) |
Correspondence
Address: |
BELL, BOYD & LLOYD, LLP
P. O. BOX 1135
CHICAGO
IL
60690
US
|
Assignee: |
SONY CORPORATION
Tokyo
JP
|
Family ID: |
38555571 |
Appl. No.: |
11/678911 |
Filed: |
February 26, 2007 |
Current U.S.
Class: |
348/143 ;
348/E5.029; 348/E7.085 |
Current CPC
Class: |
H04N 5/2256 20130101;
G08B 13/19626 20130101; H04N 7/183 20130101 |
Class at
Publication: |
348/143 ;
348/E07.085 |
International
Class: |
H04N 7/18 20060101
H04N007/18 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2006 |
JP |
P2006-053285 |
Claims
1. A monitoring camera comprising: an image capturing unit
configured to capture an image of a subject therein, said image
capturing unit having an image capturing field angle adjustable by
a zooming optical system; a light source including a light emitting
diode configured to emit an illuminating radiation; a lens unit
configured to apply said illuminating radiation in a direction
which is substantially identical to a direction in which said image
capturing unit captures the image; and an irradiation moving unit
configured to variably set an irradiation range of said
illuminating radiation to irradiate an area which is substantially
the same as said image capturing field angle of said image
capturing unit.
2. The monitoring camera according to claim 1, wherein said light
source has a light guide configured to guide the illuminating
radiation from said light emitting diode to said lens.
3. The monitoring camera according to claim 1, wherein said light
emitting diode includes an infrared emitting diode configured to
emit an infrared radiation.
4. The monitoring camera comprising: an image capturing unit
configured to capture an image of a subject therein through an
optical system; a light source including a plurality of light
emitting diodes configured to emit an illuminating radiation; and a
controller configured to control energization patterns of said
light emitting diodes in synchronism with an image capturing timing
interval of said image capturing unit.
5. The monitoring camera according to claim 4, wherein said
controller has means configured to change energization patterns of
said light emitting diodes to follow the subject when said
controller detects the subject as moving.
6. The monitoring camera according to claim 4, wherein said
controller sets a first interval and a second interval shorter than
said first interval as emission intervals of said light source; and
said controller has means configured to control said light source
to apply said illuminating radiation entirely to an image capturing
range of said image capturing unit if no moving subject is detected
in an image captured by said image capturing unit, and controlling
said light source to apply said illuminating radiation to a portion
of the image capturing range if a moving subject is detected in an
image captured by said image capturing unit, said portion of the
image capturing range including said moving subject.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] The present application claims priority to Japanese Patent
Application JP 2006-053285, filed in the Japanese Patent Office on
Feb. 28, 2006, the entire contents of which being incorporated
herein by reference.
BACKGROUND
[0002] The present application relates to a monitoring camera for
applying an infrared radiation, for example, to a subject to
capture an image of the subject.
[0003] In general, there have been provided monitoring cameras for
capturing images of suspicious objects or suspicious individuals
for security against crimes in shops, on streets, in parking lots,
and in various other places. Some monitoring cameras are combined
with an infrared projector for projecting an infrared radiation to
a subject. The infrared projector is installed near the monitoring
camera to apply the infrared radiation to an image capturing range
of the monitoring camera. The monitoring camera captures an image
of the subject which is irradiated with the infrared radiation.
Therefore, the monitoring camera combined with the infrared
projector is capable of monitoring a subject and recording its
image even at night or in a dark environment.
[0004] Monitoring cameras with a camera head swingable back and
forth and up and down for an enlarged image capturing range are
also in use. Such a monitoring camera may also be combined with a
plurality of infrared projectors to cover the swinging angle of the
camera head for capturing images in a wide image capturing range.
Monitoring cameras incorporating a small-size infrared projector
have also been provided.
[0005] Japanese Patent Laid-open No. 2004-220147 discloses a
monitoring camera equipped with an illuminating infrared
source.
[0006] The traditional monitoring camera with the projector cannot
be remotely controlled to adjust its irradiation angle. Therefore,
the projector itself needs to have a sufficiently large irradiation
range. If the projector is to maintain a radiation flux density
required for the monitoring camera to capture a desired image, then
the projector is required to have a large output level. However, in
order for the projector to have a large output level, the projector
has to be large in size. However, it is difficult to have a
large-size projector mounted on a monitoring camera having a
motor-driven swingable camera head which is subject to size
limitations.
[0007] If a monitoring camera is combined with a small-size
projector mounted on a camera head thereof, then the projector is
capable of providing sufficient illuminance only within a short
distance because the projector itself is small in size. When a
monitoring camera has its zoom lens shifted toward a telephoto end
for capturing an image of a subject in a far position, the amount
of a radiation applied to the subject tends to be insufficient if
the projector has a fixed projection angle. Therefore, the infrared
radiation application capability of the projector limits the image
capturing range of the monitoring camera.
SUMMARY
[0008] It is desirable to provide a monitoring camera which is
capable of appropriately applying a radiation to a subject to
capture an image of the subject.
[0009] According to an embodiment, there is provided a monitoring
camera including an image capturing unit for capturing an image of
a subject therein, the image capturing unit having an image
capturing field angle adjustable by a zooming optical system, a
light source having a light emitting diode for emitting an
illuminating radiation, a lens unit for applying the illuminating
radiation in a direction which is substantially identical to a
direction in which the image capturing unit captures the image, and
an irradiation moving unit for variably setting an irradiation
range of the illuminating radiation to irradiate an area which is
substantially the same as the image capturing field angle of the
image capturing unit.
[0010] With the above arrangement, the irradiation range of the
illuminating radiation can be varied to irradiate the area which is
substantially the same as the image capturing field angle of the
image capturing unit, and the image of the subject can be captured
in the varied irradiation range.
[0011] According to another embodiment, there is also provided a
monitoring camera including an image capturing unit for capturing
an image of a subject therein through an optical system, a light
source having a plurality of light emitting diodes for emitting an
illuminating radiation, and a controller for controlling
energization patterns of the light emitting diodes in synchronism
with an image capturing timing interval of the image capturing
unit.
[0012] With the above arrangement, energization patterns of the
light emitting diodes can be controlled in synchronism with the
image capturing timing interval of the image capturing unit, and
the image of the subject can be captured while the subject is being
irradiated with the radiation emitted according to the controlled
energization patterns.
[0013] Since the irradiation range of the illuminating radiation
can be varied to irradiate the area which is substantially the same
as the image capturing field angle of the image capturing unit, and
the image of the subject can be captured in the varied irradiation
range, it is possible to apply an appropriate amount of radiation
to illuminate the subject to capture the image thereof.
[0014] Furthermore, because energization patterns of the light
emitting diodes can be controlled in synchronism with the image
capturing timing interval of the image capturing unit, and the
image of the subject can be captured while the subject is being
irradiated with the radiation emitted according to the controlled
energization patterns, the light emitting diodes do not need to be
energized at all times, and hence may consume a reduced amount of
electric power.
[0015] Additional features and advantages are described herein, and
will be apparent from, the following Detailed Description and the
figures.
BRIEF DESCRIPTION OF THE FIGURES
[0016] FIG. 1 is a view showing an example in which a monitoring
camera according to an embodiment is installed;
[0017] FIG. 2 is a block diagram of internal structures of the
monitoring camera according to an embodiment and a central
controller;
[0018] FIG. 3 is a cross-sectional view showing an example of the
monitoring camera according to an embodiment;
[0019] FIGS. 4A and 4B are views showing how infrared radiation
application ranges and image capturing field angles of the
monitoring camera according to an embodiment are ganged;
[0020] FIG. 5 is a cross-sectional view showing another example of
the monitoring camera according to an embodiment;
[0021] FIGS. 6A and 6B are views showing examples of different
light source energization patterns for achieving different
irradiated states with a monitoring camera according to a second
embodiment;
[0022] FIG. 7 is a graph showing an example of intermittent
irradiation only in valid frames according to the second
embodiment;
[0023] FIG. 8 is a diagram showing an example of an irradiated area
required to capture an image according to the second
embodiment;
[0024] FIG. 9 is a cross-sectional view showing an example of a
monitoring camera according to a third embodiment, which employs
optical fibers to increase the freedom with which to position a
light source;
[0025] FIG. 10 is a cross-sectional view showing another example of
the monitoring camera according to the third embodiment, which
employs reflecting mirrors to collect light for the optical
fibers;
[0026] FIG. 11 is a cross-sectional view showing still another
example of the monitoring camera according to the third embodiment,
which employs a multireflector and a lens array to collect light
for the optical fibers;
[0027] FIG. 12 is a cross-sectional view showing yet another
example of the monitoring camera according to the third embodiment,
which employs a condensing light source; and
[0028] FIGS. 13A, 13B, and 13C are perspective views of monitoring
cameras according to other embodiments.
DETAILED DESCRIPTION
[0029] A monitoring camera according to a first embodiment will be
described below with reference to FIGS. 1 through 5. According to
the first embodiment, the principles of the invention are applied
to a monitoring camera with a zooming function which incorporates
therein a light source for applying an infrared radiation to a
subject to capture an image of the subject even at night.
[0030] External structural details of the monitoring camera
according to the first embodiment will first be described below
with reference to FIG. 1. FIG. 1 shows an example in which the
monitoring camera according to the first embodiment is installed.
In the illustrated example, the monitoring camera, denoted by 100,
is substantially in the form of a rectangular parallelepiped and
applies an infrared radiation to a subject to capture an image of
the subject even at night. The monitoring camera 100 is mounted on
an outer wall of a building. The monitoring camera 100 incorporates
therein a light source including a plurality of light-emitting
diodes (LEDs) for emitting an infrared radiation. The monitoring
camera 100 also has a Fresnel lens 14, which is a planar lens, for
emitting an infrared radiation from the light source out of the
monitoring camera 100. The Fresnel lens 14 applies illuminating
light (infrared radiation) from the monitoring camera 100 in a
range which is substantially the same as the image capturing field
angle 51 of the monitoring camera 100. The infrared radiation
emitted from the light source passes through the Fresnel lens 14
and is applied in an irradiation range 50 to irradiate a subject
55. The Fresnel lens 14 has a central through hole 14a in which a
camera lens 1 for capturing a subject image is disposed. The camera
lens 1 includes a zoom lens with a variable image capturing field
angle. Therefore, the monitoring camera 100 has a zooming function.
The irradiation range 50 of the illuminating light irradiates an
area which is substantially the same as the image capturing field
angle 51 in which the camera lens 1 of the monitoring camera 100
captures an image.
[0031] An image captured by the monitoring camera 100 is
transmitted to a central controller 30 which controls operation of
the monitoring camera 100 and is recorded in the central controller
30. The central controller 30 has a video output terminal connected
to a display monitor 40 for displaying images. The central
controller 30 displays a captured image transmitted directly from
the monitoring camera 100 on the display monitor 40 in real time,
or displays recorded image data read from a hard disk drive in the
central controller 30 on the display monitor 40. The central
controller 30 may also display captured images supplied from a
plurality of monitoring cameras 100 installed in different places,
as a segmented image screen on the display monitor 40. The central
controller 30 generates a control signal based on a user's action
on a console panel 33 having various switches or an automatic timer
setting, and transmits the generated control signal to the
monitoring camera 100. Using the control signal, the central
controller 30 can vary the image capturing field angle and the
irradiation range 50 of the illuminating light based on the zooming
function of the monitoring camera 100.
[0032] Internal structural details of the monitoring camera 100 and
the central controller 30 will be described below with reference to
FIG. 2. The monitoring camera 100 captures an image in an image
capturing range through the camera lens 1, which includes optical
components such as a plurality of zoom lenses. Incident light
applied to the camera lens 1 travels through an iris 2 for aperture
control and is focused onto an image capturing surface of a CCD
(Charge Coupled Device) image capturing device 4. The iris 2
controls the size of an aperture for passing the incident light
therethrough based on a control signal generated by a generator 10
which control various parts of the monitoring camera 100. The CCD
image capturing device 4 outputs an image signal depending on a
subject image focused on the image capturing surface thereof.
[0033] The image signal output from the CCD image capturing device
4 is applied to an analog signal processor 5 which performs analog
signal processing on the image signal. Specifically, the analog
signal processor 5 performs a sampling/holding process and an
automatic gain controlling (AGC) process on the image signal, and
outputs a processed analog image signal. The analog image signal is
applied to an analog-to-digital (A/D) converter 6, which coverts
the analog image signal into a digital image signal by sampling the
analog image signal at a predetermined sampling rate. The digital
image signal is then output from the A/D converter 6 to a digital
signal processor 7 which performs digital signal processing on the
digital image signal. Specifically, the digital signal processor 7
generates various signals required for framing, still image
capturing, etc. from the digital image signal through such digital
signal processing. The camera lens 1, the iris 2, the CCD image
capturing device 4, the analog signal processor 5, A/D converter 6,
and the digital signal processor 7 will also be collectively
referred to as a camera block 17. The monitoring camera 100 has an
infrared cutoff filter, not shown, that can selectively be
positioned in and out of the optical path leading to the CCD image
capturing device 4. For daytime monitoring, the infrared cutoff
filter is placed in the optical path for the CCD image capturing
device 4 to capture an image based on visible light. For nighttime
monitoring, the infrared cutoff filter is placed out of the optical
path for the CCD image capturing device 4 to capture an image based
on an infrared radiation.
[0034] Various processing and operational sequences of the
monitoring camera 100 are controlled by the controller 10. The
controller 10 reads processing programs, parameters, and data used
for controlling the various parts from a writable memory 11 on an
as-needed basis, performs various processing processes, and stores
required parameter and data into the memory 11. The controller 10
also controls an emission driver 16 to energize a light source 15
to emit an infrared radiation.
[0035] The monitoring camera 100 incorporates therein the light
source 15 for emitting an infrared radiation. The light source 15
includes a light-emitting diode array of a plurality of
light-emitting diodes mounted on a board 20 (see FIG. 3) integrally
combined with racks 18. An infrared radiation emitted from the
light source 15 on the racks 18 is transmitted as an illuminating
radiation through the Fresnel lens 14 which has an optical axis
substantially in the direction along which the camera block 17
captures images. The racks 18 are held in mesh with gears
operationally connected to motors 13. When the motors 13 are
energized, the gears are rotated to cause the racks 18 to move the
board 20 along the optical axis of the camera lens 1 to vary the
irradiation range of the illuminating radiation. By thus varying
the irradiation range of the illuminating radiation, the light
source 15 is moved to irradiate an area which is substantially the
same as the image capturing field angle of the camera block 17.
[0036] The central controller 30 has a controller 32 for
controlling various parts of the central controller 30. Based on a
user's action on the console panel 33 (see also FIG. 1), the
controller 32 reads processing programs, parameters, and data used
for controlling the various parts from a writable memory 36, and
performs various processing processes. The central controller 30
has a communication interface 31 which can be connected to a
communication interface 9 of the monitoring camera 100 for
transmitting data to and receiving data from the monitoring camera
100. When the communication interfaces 9, 31 are connected, the
central controller 30 transmits a control signal generated thereby
through the communication interface 31 to the monitoring camera 100
for remotely controlling the monitoring camera 100 to perform
zooming operation of the camera block 17 and adjusting the
irradiation range of the illuminating radiation. The central
controller 30 also receives captured images from the monitoring
camera 100 through the communication interface 31.
[0037] The controller 32 adds an image capturing time to a received
captured image based on time information that is read from a clock
unit 37 having a timing function, and records the captured image
with the added image capturing time in a hard disk drive 35 which
serves as a mass storage recording medium. The controller 32 can
also read times from the clock unit 37 and start and end capturing
an image with the monitoring camera 100 at preset image capturing
start and end times. The controller 32 records captured images in
the hard disk drive 35 at successive image capturing times. The
central controller 30 has an image output unit 34 for supplying
captured images read from the hard disk drive 35 to the display
monitor 40. The controller 32 controls the image output unit 34 to
output captured images to display monitor 40 to display the
captured images thereon.
[0038] Internal structural details of the monitoring camera 100
will further be described below with reference to FIG. 3. FIG. 3
shows the monitoring camera 100 in cross section. As shown in FIG.
3, linear guides 19 are mounted on inner wall surfaces of the
housing of the monitoring camera 100 along the optical axis of the
camera lens 1. The racks 18 are linearly movable on and along the
linear guides 19 by a power transmitting mechanism of gears, etc.
which can be actuated when the motors 13 are energized. According
to the present embodiment, the light source 15 has a plurality of
infrared emitting diodes 21 mounted on the board 20 which extends
substantially parallel to the Fresnel lens 14. The board 20 with
the infrared emitting diodes 21 mounted thereon is movable toward
and away from the Fresnel lens 14 in response to energization of
the motors 13. When the board 20 is thus moved, the image capturing
field angle of the monitoring camera 100 varies in a range from
3.degree. to 60.degree. in the forward direction of the monitoring
camera 100. Each of the infrared emitting diodes 21 has an
irradiation angle ranging from 20.degree. to 30.degree., for
example. The irradiation range of the illuminating radiation is
variable such that the infrared radiation emitted from the infrared
emitting diodes 21 irradiates an area which is substantially the
same as the image capturing field angle of the camera block 17 by
passing through the Fresnel lens 14. The racks 18 are movable along
the linear guides 19 by the motors 13 depending on the zoom ratio
of the camera block 17. The irradiation range of the illuminating
radiation is variable based on the positional relationship between
the Fresnel lens 14 and the light source 15.
[0039] Ganged operational relationship between infrared radiation
application ranges and image capturing field angles of the
monitoring camera 100 will be described below with reference to
FIGS. 4A and 4B. The monitoring camera 100 with the zooming
function can selectively be set to a wide-angle mode and a
telephoto mode. FIG. 4A shows an example of an infrared radiation
application range and an image capturing field angle in the
wide-angle mode, and FIG. 4B shows an example of an infrared
radiation application range and an image capturing field angle in
the telephoto mode. The irradiation range 50 of the monitoring
camera 100 is selected to irradiate an area which is slightly
greater than the image capturing field angle 51. However, since the
irradiation angle of the infrared radiation is governed by the
distribution characteristics of the applied illuminating radiation,
the irradiation range 50 may be large enough to recognize the
subject 55 when its image is to be captured even if the irradiation
range 50 falls within the image capturing field angle 51.
[0040] If the image capturing field angle 51 is spread as shown in
FIG. 4A, then the light source 15 is displaced toward the Fresnel
lens 14 to widen the irradiation range 50 of the illuminating
radiation. On the other hand, if the image capturing field angle 51
is narrowed as shown in FIG. 4B, then the light source 15 is
displaced away from the Fresnel lens 14 to narrow the irradiation
range 50 of the illuminating radiation. Therefore, the irradiation
range 50 of the illuminating radiation is variable in ganged
relation to the zooming action of the camera lens 1 to change the
image capturing field angle 51.
[0041] Accordingly, it is possible to vary the irradiation range 50
of the illuminating radiation so as to irradiate an area which is
substantially the same as the image capturing field angle 51 of the
monitoring camera 100, for capturing an image of the subject
55.
[0042] According to the present embodiment, the monitoring camera
100 is capable of varying the irradiation range 50 of the
illuminating radiation substantially in the same manner as with the
image capturing field angle 51 which varies as the camera block 17
makes a zooming action between the telephoto mode and the
wide-angle mode. As a result, the monitoring camera 100 can apply
an appropriate amount of infrared radiation depending on the
position and size of the subject 55 to be imaged. The monitoring
camera 100 can reliably capture an image of the subject 55 without
an illuminating radiation shortage even when the subject 55 is
located far away from the monitoring camera 100.
[0043] In the first embodiment described above, an infrared
radiation is emitted from the infrared emitting diodes 21 mounted
on the planar board 20. However, as shown in FIG. 5, an infrared
radiation may be emitted from a plurality of infrared emitting
diodes 21 mounted on a curved board 20' which is convex outwardly,
i.e., toward the Fresnel lens 14. Details of the monitoring camera
shown in FIG. 5, other than the curved board 20', are identical to
those of the monitoring camera 100 shown in FIG. 3. Since the light
source has its radiation distribution characteristics changed by
changing the layout of the infrared emitting diodes, the
distribution characteristics of the applied illuminating radiation
can be changed for a wider irradiation range.
[0044] A monitoring camera 200 according to a second embodiment
will be described below with reference to FIGS. 6A, 6B, 7, and 8.
The monitoring camera 200 is capable of varying the irradiation
range of the illuminating radiation by changing light source
energization patterns.
[0045] First, internal structural details of the monitoring camera
200 will be described below. The monitoring camera 200 has a light
source 24 for emitting an infrared radiation, the light source 24
including a total of nine infrared emitting diodes 21a through 21i
arranged in three vertical columns and three horizontal rows and
mounted on the board 20. The monitoring camera 200 also has a
microlens array 22 disposed in front of the board 20 for converting
infrared radiations emitted from the respective infrared emitting
diodes 21a through 21i into a parallel beam, and a projector
optical system lens 23 disposed in front of the microlens array 22
for enlarging the irradiation range of the illuminating radiation
from the microlens array 22. The monitoring camera 200 has a signal
processing system which is identical to the signal processing
system of the monitoring camera 100 according to the first
embodiment shown in FIG. 2. The monitoring camera 200 differs from
the monitoring camera 100 in that the controller 10 controls light
source energization patterns peculiar to the second embodiment.
[0046] Examples of light source energization patterns of the
monitoring camera 200 will be described below. When the monitoring
camera 200 detects a moving subject 55, the monitoring camera 200
changes energization patterns of the light source 24 to follow the
subject to apply the illuminating radiation to the subject or
intermittently energizes the light source 24 at given emission
intervals to apply the illuminating radiation to the subject. These
functions of the monitoring camera 20 are achieved under the
control of the controller 10 which operates according to control
commands from the central controller 30. When the monitoring camera
200 detects a moving subject 55, the controller 10 can also
individually energize the infrared emitting diodes 21a through 20i
according to full or partial energization patterns read from the
memory 11.
[0047] FIG. 6A shows a first light source energization pattern by
way of example. According to the first light source energization
pattern, a diagonal array of infrared emitting diodes on the board
20 are energized. Specifically, when the monitoring camera 200
detects the moving subject 55 which moves diagonally as shown in
FIG. 6A, the controller 10 energizes the infrared emitting diodes
21a, 21e, 21i and de-energizes the other infrared emitting diodes.
Infrared radiations emitted from the infrared emitting diodes 21a,
21e, 21i pass through the microlens array 22 and the optical system
lens 23, and illuminate irradiated areas 53a, 53e, 53i on a
diagonal line of a captured image 52.
[0048] FIG. 6B shows a second light source energization pattern by
way of example. According to the second light source energization
pattern, a lower array of infrared emitting diodes on the board 20
are energized. Specifically, when the monitoring camera 200 detects
the moving subject 55 which moves horizontally, as shown in FIG.
6B, the controller 10 energizes the infrared emitting diodes 21g,
21h, 21i and de-energizes the other infrared emitting diodes for
following the subject 55. Infrared radiations emitted from the
infrared emitting diodes 21g, 21h, 21i pass through the microlens
array 22 and the optical system lens 23, and illuminate irradiated
areas 53g, 53h, 53i on a lower horizontal line of the captured
image 52.
[0049] In FIGS. 6A and 6B, three infrared emitting diodes are
simultaneously energized. However, only one or two infrared
emitting diodes may be simultaneously energized.
[0050] In the second embodiment shown in FIGS. 6A and 6B, the light
source energization patterns are controlled. These light source
energization patterns may be combined with an intermittent light
source energization pattern to be described below for more
efficient generation of illuminating radiation. An example of
intermittent infrared irradiation only in valid frames according to
the second embodiment will be described below with reference to
FIG. 7. FIG. 7 shows a graph having a horizontal axis representing
time and a vertical axis the level of emitted infrared radiation.
In this example, the monitoring camera 200 has its infrared
emitting diodes not continuously energized, but intermittently
energized in synchronism with an image capturing timing interval of
the camera block 17.
[0051] A traditional monitoring camera has its infrared emitting
diodes continuously energized for monitoring. In FIG. 7, the
traditional monitoring camera emits a level L2 of infrared
radiation continuously for times t1 through t4 from the infrared
emitting diodes. The monitoring camera 200 according to the present
embodiment shown in FIG. 7 has its infrared emitting diodes
energized for strobe emission for a strobe emission period T=t4-t1
in synchronism with an image capturing timing interval. An image
capturing timing interval from time t2 to time t3 represents a
valid frame, and a timing interval from time t3 to time t5
represents an invalid frame. Time t5-t4 is equal to time t2-t1. The
monitoring camera 200 emits a level L1 of infrared radiation
intermittently for times t2 through t3 from the infrared emitting
diodes. If the amount of emission energy produced by the level L1
of infrared radiation for times t2 through t3 is equal to the
amount of emission energy produced by the level L2 of infrared
radiation from times t1 through t4, then the infrared emitting
diodes can emit a stronger level of infrared radiation in
synchronism with the image capturing timing interval to give a far
subject an amount of infrared radiation required to capture an
image of the subject.
[0052] An example in which only an area required to capture an
image is irradiated in synchronism with the image capturing timing
interval will be described below with reference to FIG. 8. FIG. 8
shows a diagram having a horizontal axis representing time with an
array of captured images 52 arranged at respective times. The
monitoring camera 200 according to the present embodiment shown in
FIG. 8 has its infrared emitting diodes energized for strobe
emission in synchronism with an image capturing timing interval of
the camera block 17, and also changes energization patterns of the
infrared emitting diodes in order to follow a moving subject.
Specifically, the monitoring camera 200 controls the light source
24 to emit an infrared radiation at intervals T1 (in sec.)
according to a pattern or to emit an infrared radiation at
intervals T2 (in sec.) according to another pattern wherein the
intervals T1 are longer than the intervals T2 (T1>T2).
Similarly, the monitoring camera 200 controls the camera block 17
to capture images at image capturing timing intervals T1 (in sec.)
or to capture images at image capturing timing intervals T2 (in
sec.) wherein the intervals T1 are longer than the intervals T2
(T1>T2). If there is no moving subject 55 detected in captured
images 52 output from the camera block 17, then the monitoring
camera 200 controls the light source 24 to emit an infrared
radiation at the intervals T1. The controller 10 selects a lower
frame rate for increased infrared radiation emission intervals, and
applies the illuminating radiation to the entire image capturing
range. If there is a moving subject 55 detected in captured images
52 output from the camera block 17, then the monitoring camera 200
controls the light source 24 to emit an infrared radiation at the
intervals T2 and also controls the camera block 17 to capture
images at image capturing timing intervals T2. The controller 10
selects a higher frame rate for reduced infrared radiation emission
intervals, and applies the illuminating radiation to a portion,
which includes the subject 55, of the entire image capturing range
to change light source energization patterns in order to follow the
moving subject 55. Each of the intervals T1 may be 1 second, and
each of the intervals T2 may be 1/30 second.
[0053] In this manner, the monitoring camera 200 is capable of
capturing images by changing image capturing timing intervals and
light source energization patterns.
[0054] According to the second embodiment, when the light source is
energized intermittently, the electric power consumption is reduced
and the amount of heat generated by the monitoring camera is also
reduced. However, the light source can apply an intensive
illuminating radiation in synchronism with the image capturing
timing intervals of the camera block. As a result, the monitoring
camera achieves a sufficient level of illuminance at positions far
the monitoring camera to make captured images highly bright, and
can capture images positioned at greater distances from the
monitoring camera at night. When a subject is detected, the image
capturing timing intervals are shortened to capture images of the
subject at a higher frame rate. Consequently, images of the subject
can reliably be captured even if the subject moves quickly. Since
the light source includes infrared emitting diodes, it can switch
instantaneously between the energized state and the de-energized
state, allowing images of the subject to be captured depending on
the motion of the subject.
[0055] When the image capturing range is monitored ordinarily with
no subject detected, its image is captured at a lower frame rate.
Even if the image capturing range is monitored for a long period of
time, therefore, the amount of data of captured images to be
recorded may be small. Accordingly, the required amount of data may
be recorded in a recording device such as a hard disk drive, a tape
drive, or the like for an increased period of time. If images are
recorded in a tape drive, then the tape in the tape drive may be
replaced less frequently.
[0056] In FIGS. 6A and 6B, a diagonal array of infrared emitting
diodes and a low array of infrared emitting diodes, respectively,
are energized simultaneously. However, the infrared emitting diodes
to be energized are not limited to the patterns shown in FIGS. 6A
and 6B. If a plurality of subjects 55 are detected at opposite ends
of the image capturing range 52, the emitted infrared radiation may
be applied to the subjects 55 only. In this manner, the electric
power consumption of the light source is further reduced, and the
freedom with which to switch between irradiation ranges is
increased.
[0057] In FIGS. 6A and 6B, the light source includes a total of
nine infrared emitting diodes 21a through 21i arranged in three
vertical columns and three horizontal rows. However, the number of
infrared emitting diodes that can be used is not limited to nine,
but the light source may include more or less infrared emitting
diodes depending on the circumstances in which the monitoring
camera is used.
[0058] In FIG. 7, the amount of emission energy produced by the
level L1 of infrared radiation for times t2 through t3 is equal to
the amount of emission energy produced by the level L2 of infrared
radiation from times t1 through t4. However, there is a situation
where a high level of infrared radiation may not be required when
the image capturing range is monitored ordinarily with no subject
detected. In such a situation, the infrared radiation emission
intervals may be increased to reduce the amount of emission energy
produced by the level L1 of infrared radiation for times t2 through
t3, for thereby lowering the electric power consumption. If the
monitoring camera is powered by a limited power supply such as a
battery or the like, then the increased infrared radiation emission
intervals are effective to prolong the service life of the
battery.
[0059] A monitoring camera 300 according to a third embodiment will
be described below with reference to FIGS. 9 through 12. The
monitoring camera 300 employs a light guide in the form of optical
fibers to increase the freedom with which to position a light
source. The monitoring camera 300 has a signal processing system
which is identical to the signal processing system of the
monitoring camera 100 according to the first embodiment shown in
FIG. 2. The monitoring camera 300 differs from the monitoring
camera 100 in that it has a light source peculiar to the third
embodiment.
[0060] First, internal structural details of the monitoring camera
300 will be described below. FIG. 9 shows in cross section the
monitoring camera 300 which employs optical fibers 63 for guiding a
infrared radiation from infrared emitting diodes of a light source
25 to a Fresnel lens 14'. Specifically, the infrared radiation from
the infrared emitting diodes of the light source 25 is collected by
a reflector 64 having a circularly curved inner reflecting surface
toward a first terminal end 63a of the optical fibers 63. The
optical fibers 63 are capable of transmitting the infrared
radiation applied to the first terminal end 63a therethrough to a
second terminal end 63b, opposite to the first terminal end 63a,
and emitting the transmitted infrared radiation from the second
terminal end 63b without any substantial loss. The infrared
radiation applied to the first terminal end 63a passes through the
optical fibers 63 and is emitted from the second terminal end 63b.
The emitted infrared radiation is converted from a converged beam
into a spread beam by a diffusion plate 62. The infrared radiation
emitted from the diffusion plate 62 passes a zoom lens 61 and the
Fresnel lens 14', and is applied to the image capturing range of
the monitoring camera 300. Although the light source 15 according
to the first embodiment is movable, the light source 25 of the
third embodiment is not movable, but the zoom lens 61 is movable to
enlarge or contract the infrared radiation beam emitted from the
second terminal end 63b of the optical fibers 63 before the
infrared radiation passes through the Fresnel lens 14 and is
applied as the illuminating radiation to the image capturing
range.
[0061] According to the third embodiment, the light source 25 of
the illuminating radiation may be located at a position spaced from
the monitoring camera 300.
[0062] For example, the optical fibers 63 allow the light source 25
to be spaced from the Fresnel lens 14' of the monitoring camera
300. Therefore, as shown in FIG. 9, the light source 25 may be
disposed behind the camera block 17 in the housing of the
monitoring camera 300. Therefore, the monitoring camera 300 itself
may be reduced in size. Alternatively, the light source 25 may not
be placed in the housing of the monitoring camera 300, but may be
located outside of the housing of the monitoring camera 300 to
transmit the infrared radiation through the optical fibers 63 into
the monitoring camera 300. The alternative arrangement makes it
possible to further reduce the size of the monitoring camera
300.
[0063] In the third embodiment, the infrared radiation from the
light source 25 is collected by the reflector 64. However, the
infrared radiation from the light source 25 may be guided to the
optical fibers 63 by any of various other structures. FIGS. 10
through 12 show such other structures for guiding or collecting the
infrared radiation from the light source toward the optical fibers
63.
[0064] FIG. 10 shows a structure in which the infrared radiation
emitted from the light source is collected by two reflecting
mirrors that confront each other. The light source includes an
infrared emitting diode chip 26. The infrared radiation emitted
from the infrared emitting diode chip 26 is reflected by a concave
reflecting mirror 66 and focused to a position at the focal point
of the reflecting mirror 66. The first terminal end 63a of the
optical fibers 63 is disposed near the focal point of the
reflecting mirror 66. Another smaller-diameter concave reflecting
mirror 65 is positioned near the infrared emitting diode chip 26 in
confronting relation to the reflecting mirror 66 for directing the
infrared radiation emitted from the infrared emitting diode chip 26
toward the reflecting mirror 66. With the arrangement shown in FIG.
10, the infrared radiation emitted from the infrared emitting diode
chip 26 is collected by the reflecting mirrors 65, 66 toward the
first terminal end 63a of the optical fibers 63. The collected
infrared radiation is transmitted through the optical fibers 63 and
then emitted from the second terminal end 63b.
[0065] FIG. 11 shows a structure in which the infrared radiation
emitted from a light source 27 is collected by a multireflector.
Specifically, a microlens array 67 for producing parallel beams is
disposed in front of a plurality of infrared emitting diodes of the
light source 27. The infrared radiation emitted from the light
source 27 is converted by the microlens array 67 into parallel
beams, which are reflected by a concave multireflector 68 and
focused onto the first terminal end 63a of the optical fibers 63.
The infrared radiation beam applied to the first terminal end 63a
travels through the optical fibers 63 and then is emitted from the
second terminal end 63b.
[0066] FIG. 12 shows a structure in which the infrared radiation
emitted from a plurality of light sources. Specifically, concave
reflectors 69 are disposed respectively around light sources 28 and
have respective focal points positioned at the first terminal end
63a of the optical fibers 63. The infrared radiation emitted from
the light sources 28 are reflected by the respective reflectors 69
and focused onto the first terminal end 63a of the optical fibers
63. The infrared radiation beam applied to the first terminal end
63a travels through the optical fibers 63 and then is emitted from
the second terminal end 63b.
[0067] In the third embodiment described above, the optical fibers
63 are used as a light guide. However, any of various other members
capable of emitting a radiation applied to one end thereof from the
other end thereof may be employed as a light guide.
[0068] According to the first through third embodiments described
above, since the monitoring camera can employ various different
light sources and emission patterns, a effective illuminating
radiation can be applied to a subject positioned in the image
capturing range to capture an image of the subject. Images of
subjects, which have heretofore been difficult to capture at night
unless a combination of a large-size projector and a large-size
motor-driven camera platform are used, can be captured by a single
monitoring camera combined with a small-size light source.
According to an embodiment, the monitoring camera can be installed
in a reduced installation space at a reduced installation cost. The
image capturing field angle and the irradiation range of the
monitoring camera can freely be controlled in a ganged fashion.
Inasmuch as the infrared radiation emitted from the light source
can be efficiently guided to a position near the camera block, the
light source may be reduced in size. The light source in the form
of light-emitting diodes is capable of emitting a required amount
of radiation even though it consumes a small amount of electric
power, and hence may be of a low electric power requirement.
[0069] In the first through third embodiments described above, the
light source includes infrared emitting diodes. However, the light
source may include light-emitting diodes for emitting visible
light. Alternatively, infrared emitting diodes and light-emitting
diodes may be combined with each other and may alternatively be
energize to selectively emit an infrared radiation and visible
light. White-light-emitting diodes are easy and convenient to use
because they are less liable to deteriorate even when used over a
long period of time and are highly durable when instantaneously
energized. The light source for emitting visible light may include
a halogen lamp, a fluorescent tube, or the like.
[0070] The arrangement for varying the irradiation angle depending
on the image capturing field angle, the arrangement for changing
light source energization patterns to intermittently energize the
light source, and the arrangement for guiding the infrared
radiation through the light guide, as described above according to
the first through third embodiments, may be combined in any of
various possible combinations.
[0071] The recording device incorporated in the central controller
30 includes the hard disk drive 35 in the illustrated embodiment.
However, captured images may be recorded in any of various
recording mediums including an optical disk, a magnetic disk, a
magneto-optical disk, a flash memory, at the like.
[0072] In the first through third embodiments described above, the
light source and the camera block are accommodated in the
monitoring camera housing in the form of a rectangular
parallelepiped. However, the monitoring camera may have a housing
having another shape. FIGS. 13A through 13C show motor-driven
swingable PTZ (Pan-Tilt-Zoom) monitoring cameras having an infrared
emitter for emitting an infrared radiation from a light source
incorporated therein. Each of the motor-driven swingable PTZ
monitoring cameras shown in FIGS. 13A through 13C includes a
dome-shaped camera having a camera block and a projector, and can
be rotated about vertical and horizontal axes (not shown).
[0073] Specifically, FIG. 13A shows a monitoring camera 400 having
a camera lens and an infrared emitter whose respective axes are
aligned with each other. Specifically, the monitoring camera 400 is
fixedly mounted on a base 71. The monitoring camera 400 includes a
horizontally movable unit 72 disposed on the base 71 for rotation
through horizontal angles and a vertically movable unit 73 disposed
in the horizontally movable unit 72 for rotation through vertical
angles. The vertically movable unit 73 houses therein an infrared
emitter 75 having a Fresnel lens and a camera lens 1 coaxial with
the infrared emitter 75.
[0074] FIG. 13B shows a monitoring camera 410 having a camera lens
and an infrared emitter whose respective axes are spaced from and
extend parallel to each other. Specifically, the monitoring camera
410 is fixedly mounted on the base 71. The monitoring camera 410
includes the horizontally movable unit 72 disposed on the base 71
and the vertically movable unit 73 disposed in the horizontally
movable unit 72. The vertically movable unit 73 houses therein the
infrared emitter 75 and the camera lens 1 whose respective axes are
spaced from and extend parallel to each other.
[0075] FIG. 13C shows a monitoring camera 420 having a camera lens
and four infrared emitters, the infrared emitters having respective
axes disposed around the camera lens. Specifically, the monitoring
camera 420 is fixedly mounted on the base 71. The monitoring camera
420 includes the horizontally movable unit 72 disposed on the base
71 and the vertically movable unit 73 disposed in the horizontally
movable unit 72. The vertically movable unit 73 houses therein the
camera lens 1 and four infrared emitters 76a through 76d which are
disposed around the camera lens 1. The infrared emitters 76a
through 76d have respective axes parallel to the optical axis of
the camera lens 1.
[0076] The monitoring cameras 400, 410, 420 may be electrically
connected to a central controller for setting swinging angles and
swinging patterns to vary an image capturing range and adjust an
irradiation angle depending on a camera zooming action. The
motor-driven swingable monitoring cameras with the projector
incorporated in their head are thus capable of providing a
sufficient distance over which the radiation is to be projected and
a sufficient level of illuminance over the distance, for thereby
achieving an increased monitoring capability.
[0077] It should be understood that various changes and
modifications to the presently preferred embodiments described
herein will be apparent to those skilled in the art. Such changes
and modifications can be made without departing from the spirit and
scope of the present subject matter and without diminishing its
intended advantages. It is therefore intended that such changes and
modifications be covered by the appended claims.
* * * * *